JPH053685A - Elliptical ultrasonic motor - Google Patents

Abstract

PURPOSE:To constitue an elliptical ultrasonic motor, being utilized as a linear motor, only of rectangular piezoelectric element boards which can be fabricated easily without sacrifice of driving force. CONSTITUTION:An elliptical ultrasonic wave transmission path 4 having predetermined cross-section has a width n/4 times(n is an odd number) as long as the ultrasonic wavelength lambda and elongated holes 7, 8 are provided adjacent to the long sides 3, 3' of the ultrasonic wave transmission path 4. Rectangular piezoelectric element boards 11, 12 are bonded to the rear of the long sides 3, 3' with positional phase shift corresponding with odd times of lambda/4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor suitable for use as a linear motor.

[0002]

2. Description of the Related Art As a rotary type ultrasonic motor, in Japanese Examined Patent Publication No. 1-17354, a plurality of electrostrictive elements are arranged in a flat ring-shaped elastic plate body so as to have a phase difference. It is shown that a voltage is applied to generate an ultrasonic traveling wave in the flat ring-shaped elastic plate body, and the flat plate circular rotor brought into pressure contact with the surface of the flat ring-shaped elastic plate plate is rotated. ing. Further, as a linear type ultrasonic motor, in Japanese Patent Laid-Open No. 61-35177, a plurality of piezoelectric elements having a phase difference are laminated on almost the entire back surface of an oval elastic substrate to form an elastic substrate. It has been proposed to excite the entire surface and transmit an ultrasonic traveling wave to a slider from an elliptical vibration transmission member integrally formed with an elastic body.

[0003]

However, in the above-mentioned conventional ultrasonic motor, a piezoelectric element is arranged over substantially the entire surface of a circular or elliptical elastic diaphragm, and vibration is excited on the entire surface of the elastic diaphragm to generate the vibration. A shaft for fixing the ultrasonic motor and the like were arranged in the node portion. Therefore, a piezoelectric element having an arc shape or a fan shape is required. Since a piezoelectric element is generally formed of a ceramic material, the fabrication of a precise piezoelectric element having such a shape has problems that workability and yield are poor and cost is high due to uneven shrinkage in the firing process. It was Therefore, in an elliptical ultrasonic motor, it is possible to arrange the piezoelectric element only on the linear portion of the long side, not on the entire back surface of the elastic base body. Vibration does not always travel along the planned ellipse, ultrasonic vibration is transmitted to the part for fixing the motor, etc., the traveling direction of ultrasonic waves is disturbed, and the driving force of the motor becomes extremely weak. I found a problem. The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic motor using only a rectangular piezoelectric element that is easy to manufacture.

[0004]

In order to achieve the above object, the present invention is provided with a stator body 1 made of an elastic body such as metal, as illustrated in the drawings, and the stator body 1 has a semicircular shape. An ultrasonic conducting passage 4 configured as a closed passage having a substantially oval shape composed of the portions 2 and 2'and long side portions 3 and 3 ', and a substrate 5 for supporting and fixing the ultrasonic conducting passage 4 are integrally formed. The long side portions 3 and 3'of the ultrasonic wave conduction passage 4 of the substrate 5 are formed.
Slots 7 and 8 are provided in a portion adjacent to the ultrasonic conducting passage 4, and the movable element 30 is in contact with the surface of the ultrasonic conducting passage 4, and the ultrasonic conducting passage 4 has a substantially constant cross-sectional shape. The piezoelectric element 1 is provided on the bottom surfaces of the long side portions 3 and 3'of the sound wave conduction passage 4.
1 and 12 are attached to each of the piezoelectric elements 11,
Numeral 12 is polarized in the thickness direction thereof, and is half the length λ (λ is equal to the wavelength of the standing wave generated in the ultrasonic wave conduction passage 4) which is an integer fraction of the ultrasonic wave transmission passage 4. The polarization directions of the piezoelectric elements 11 and 1 are different from each other.
2 are disposed along the ultrasonic conduction path at a position relatively displaced by an odd multiple of λ / 4.
An oval ultrasonic motor is provided which is characterized in that the width thereof is an odd multiple of λ / 4.

[0005]

In the oval ultrasonic motor configured as described above, the long side portions 3 and 3'of the ultrasonic conduction passage 4 are applied by applying a high frequency voltage of an appropriate frequency to the piezoelectric elements 11 and 12.
A bending vibration having a wavelength λ, which is an integral fraction of the entire circumference of the ultrasonic conduction path 4, is excited. The vibration is a transverse wave, and its wavelength λ is also defined by the cross-sectional shape of the ultrasonic conduction passage 4. The vibration not only tries to be transmitted in the longitudinal direction along the long side portions 3 and 3 ′ in the ultrasonic conduction path 4, but also to the side substrate 5. However, the long sides 3, 3'of the ultrasonic conduction passage 4 are
Since the substrate 5 and the substrate 5 are separated and insulated by the long holes 7 and 8, vibration is not transmitted to the substrate 5 from the long side portions 3 and 3 '.
In the semi-circular portions 2 and 2'of the ultrasonic conduction passage 4, the ultrasonic conduction passage 4 and the substrate 5 are continuous, but according to experiments, the traveling direction of ultrasonic vibration is semi-circular due to the semi-circular shape. It travels along the circumference along the circles 2, 2'and does not try to enter the substrate 5. Further, since the width of the ultrasonic conduction passage 4 is formed to be 1/4 of the wavelength λ, the vibration component that is going to be transmitted in the width direction of the ultrasonic conduction passage 4 has an anti-resonance relationship and is attenuated. .. Therefore, the traveling direction of the ultrasonic vibration does not meander in the ultrasonic transmission passage 4. Due to the above three actions, when a high frequency voltage having an appropriate frequency is applied to the first or second piezoelectric element 11 or 12, a stable standing wave is generated all around the ultrasonic conduction path 4. Therefore, a high-frequency voltage having a temporal phase difference of 90 ° between the first and second piezoelectric elements 11 and 12 having a positional phase difference of λ / 4, for example, Asin (ωt) to the first piezoelectric element, By applying a voltage of Asin (ωt ± 90 °) to the second piezoelectric element, the oval ultrasonic wave conduction path 4
It is possible to generate a stable traveling wave on the surface of the. The mover 30 is driven by this traveling wave.

[0006]

Embodiments of the present invention will be described with reference to the drawings. 1 is a plan view showing a stator portion of an ultrasonic motor, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a bottom view. The stator body 1 is formed of an elastic body made of a copper alloy, and an ultrasonic conduction path 4 in which the semicircular portions 2 and 2'and the long side portions 3 and 3'continue to form an oval closed passage, It consists of a central substrate 5 for fixing the ultrasonic motor to a base, etc.
5 is integrally formed.

A large number of lateral grooves 6 are formed on the surface of the ultrasonic conducting passage 4.
Are formed. As shown in FIG. 2, the cross section of the ultrasonic conduction passage 4 below the bottom of the lateral groove has a constant rectangular shape. As shown in FIG. 3, in the ultrasonic conducting passage 4, the arc length of 1/3 of the semi-circular portions 2 and 2'in the central length thereof is 1 wavelength (λ), and the long side portion is 3.5 λ. Has been made of.
Therefore, the total circumferential length of the ultrasonic conduction passage 4 is 13λ. Further, the width W of the ultrasonic conduction passage 4 is formed to have a length of λ / 4. Then, two elongated holes 7 and 8 are formed in the substrate 5 adjacent to the long side portions 3 and 3'of the ultrasonic conduction passage 4. Therefore, the ultrasonic conduction passage 4 and the substrate 5 are separated by the semicircular portion 2,
2 ′ is continuous, and long side portions 3 and 3 ′ have long holes 7,
Separated by 8. The central portion of the substrate 5 is formed to have a slightly thick plate, and an elongated hole 9 for inserting a fixing bolt is provided at the center thereof.

Three piezoelectric elements 11, 12 and 13 are attached to the bottom surfaces of the long side portions 3 and 3'of the ultrasonic wave conduction passage 4. Each of the piezoelectric elements 11, 12 and 13 is a plate-shaped ceramic polarized material having a thickness of about 0.5 mm and electrodes are provided on both sides thereof, and the first and second piezoelectric elements 11 and 12 have a length of 3λ. And is polarized in the thickness direction so that the polarization directions alternate for each λ / 2. In the figure, the shaded portions are polarized portions, and the portions with different shaded directions have different polarization directions. The second piezoelectric element 12 is fixed at a position separated from the first piezoelectric element 11 by 3.25λ, that is, at a position where the positional phase shifts by λ / 4. The third piezoelectric element 13 has a length of λ / 4, and is fixed at a position separated from the first piezoelectric element 11 by λ / 4. The first and second piezoelectric elements 11 and 12 are used for exciting ultrasonic waves, and the third piezoelectric element 13 is used for detecting a feedback signal of the excitation amplitude.

First piezoelectric element 11 and second piezoelectric element 1
2 is connected to oscillators 21 and 22 and is connected to the first piezoelectric element A
A sin (ωt), a high frequency voltage of about 32 KHz with a time phase of Asin (ωt ± 90 °) deviated by ± 90 ° is applied to the second piezoelectric element in the thickness direction. As a result, an ultrasonic traveling wave is generated on the surface of the oval ultrasonic conduction passage 4 and circulates in the ultrasonic conduction passage 4. The amplitude of ultrasonic vibration is detected by the third piezoelectric element 13 and fed back to the oscillators 21 and 22 to control the applied voltage appropriately. The frequency of the applied high-frequency voltage is the wavelength of the ultrasonic wave because the velocity of the transverse ultrasonic wave propagating through the ultrasonic conduction path 4 is determined by the cross-sectional shape, material and temperature of the ultrasonic conduction path 4. The frequency is selected to match λ (1/13 of the entire circumference of the ultrasonic conduction path 4).

FIG. 4 is a sectional view showing a linear type ultrasonic motor using the stator 1 described above. The stator 1 is fastened and fixed to a base 24 by a fixing bolt 23 inserted in a long hole 9 in the center of the substrate 5. Bolts 25 and 26 are erected on both sides of the long side portion 3'on the right side of the drawing, and a horizontal shaft 27 is fixed to the bolts 25 and 26. A roller 28 is rotatably supported on the horizontal shaft 27 so that the roller 28 contacts the long side portion 3 '. A rail-shaped mover 30 having an L-shaped cross section is placed in contact with the roller 28. The mover 30 contacts the roller 28 and also directly contacts the surface of the long side portion 3 on the left side of the drawing. The mover 30 is guided by a guide (not shown) and is movable in a direction perpendicular to the drawing. When a high-frequency voltage with a temporal phase shift of ± 90 ° is applied to the first and second piezoelectric elements 11 and 12 fixed to the bottom surfaces of the long side portions 3 and 3'by shifting the positional phase by a quarter wavelength, An ultrasonic traveling wave is generated on the surface of the oval ultrasonic conduction passage 4. Due to the ultrasonic wave of the transverse wave that bends up and down, the driving force is transmitted by friction to the mover 30 that directly contacts the surface of the long side portion 3 where the transverse groove 6 is cut, in the direction opposite to the traveling direction of the ultrasonic wave. Then, the mover 30 is linearly driven. The drive direction is reversed by the roller 28 at the long side portion 3'on the right side of the drawing, and the driving force in the same direction as the left side portion 3 on the left side is transmitted to the mover 30.

In order to generate a stable ultrasonic traveling wave in the oval ultrasonic wave passage 4, the substrate 5 is provided with elongated holes 7 and 8 and the width W of the ultrasonic wave passage 4 is 1 / wavelength λ. It will be explained that it is extremely effective to make it an odd multiple of 4. In order to generate a stable ultrasonic traveling wave, when only one piezoelectric element 11 is excited, the vibration is transmitted to the opposite long side portions 3 ′ along the ultrasonic conduction path 4, and the elliptical supersonic wave is generated. It must be possible to generate a stable standing wave in the sound conduction path 4. 5, 6 and 7 are Claudeney's figures showing the pattern of standing wave vibration when only the first piezoelectric element 11 is excited, and are figures observed by spraying alumina powder on the back surface of the stator 1. is there. The thick line shows the area where the alumina powder has gathered, indicating the nodal line of vibration.

FIG. 6 shows the width W'of the ultrasonic conducting passage 4 as λ / 4.
This is a case in which the holes are made larger by about 50% and only the holes 41 and 42 for inserting bolts are provided in the substrate 5, and the long holes 7 and 8 adjacent to the long side portions 3 and 3'are not provided. In this case, the Clardonie pattern is not perpendicular to the longitudinal direction at the long side portions 3 and 3'and extends from the long side portions 3 and 3'to the substrate 5. This indicates that the vibration is meandering and is penetrating from the ultrasonic wave conduction passage 4 to the substrate 5. further,
Although not shown in the drawing, the thick line portion where the alumina powder was collected was not stationary and was constantly moving around and changing. This indicates that the standing wave is unstable. Even if the first and second piezoelectric elements 11 and 12 are excited in this state, the long side portion 3,
In 3 ', a stable traveling wave cannot be generated, and depending on the location, a traveling wave traveling in the opposite direction is also generated, and only a very weak driving force can be applied to the mover 30.

In FIG. 7, long holes 7 and 8 adjacent to the long side portions 3 and 3'are provided in the substrate 5, but the width W'of the ultrasonic conduction passage 4 is λ /.
This is the case where the value is increased by about 50% from that of No. 4. In this case, the Clardonii pattern appeared only on the ultrasonic conduction path 4 and was relatively stationary. However, it is shown that the long sides 3 and 3'are not perpendicular to the longitudinal direction, and that the vibrations meander along the long sides 3 and 3 '. When the first and second piezoelectric elements 11 and 12 are excited in this state, the long side portion 3,
The traveling wave in the center of 3'becomes weak, and the driving force applied to the mover 30 is slightly weak.

FIG. 5 shows a long hole 7 adjacent to the long side portions 3 and 3 '.
8 is provided and the width W of the ultrasonic conduction passage 4 is set to λ / 4, which is the case of the present embodiment. In this case, the Klardney's figure shows a shape perpendicular to the longitudinal direction at the long side portions 3 and 3 ′, appears only on the ultrasonic conduction path 4, is stationary and stable, and has the entire circumference of the ultrasonic conduction path 4. A shape obtained by dividing the above into 26 is shown. This indicates that by exciting one piezoelectric element 11, a stable standing wave is generated in the entire circumference of the oval ultrasonic wave conduction passage 4. In this state, the first and second piezoelectric elements 11, 1
When 2 is excited, the standing waves whose λ / 4 position phase is deviated from each other interfere with each other to generate a stable traveling wave that circulates in the ultrasonic conduction path 4, and a strong driving force is applied to the mover 30. I was able to give.

In the embodiment described above, the ultrasonic conduction passage 4
Although the movable element 30 is brought into contact with the long side portions 3 and 3'of the above so as to obtain the driving force in the linear direction, the disk-shaped movable element is brought into contact with the semicircular portion 2 or 2'of the ultrasonic conduction passage 4. It may be possible to obtain a rotational force. Also, without using the roller 28,
The mover may be brought into contact with only one of the long sides 3 to obtain a linear driving force.

[0016]

According to the present invention, the width of the ultrasonic conducting path is set to an odd multiple of 1/4 of the wavelength λ, and the long hole is provided in the substrate adjacent to the long side portion. There is an excellent effect that a stable ultrasonic traveling wave can be generated in an elliptical stator by using only a rectangular plate-shaped piezoelectric element that is easy to process. Therefore, an inexpensive linear ultrasonic motor can be provided.

[Brief description of drawings]

FIG. 1 is a plan view showing a stator of an ultrasonic motor,

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a bottom view of the stator,

FIG. 4 is a sectional view showing an ultrasonic motor,

FIG. 5 is a bottom view showing a Clarney pattern in the embodiment,

FIG. 6 is a bottom view showing a Klarney pattern in another example;

FIG. 7 is a bottom view showing a Klarney pattern in another example.

[Explanation of symbols]

1. ． Stator, 2, 2 '. ． Semicircle part, 3, 3 '. ．
Long side part, 4. ． Ultrasonic conduction passage, 5. ． substrate,
7, 8. ． Long hole, 11, 12. ． Piezoelectric element, 30. ．
Mover.

Claims (1)

Claim: What is claimed is: 1. A stator main body made of an elastic material such as metal, wherein the stator main body is a super-closed passage formed of a semi-circular portion and a long side portion. An ultrasonic wave conduction passage and a substrate for supporting and fixing the ultrasonic conduction passage are integrally formed, and a long hole is provided in a portion of the substrate adjacent to the long side portion of the ultrasonic conduction passage, and A mover is in contact with the surface of the passage, the cross-sectional shape of the ultrasonic conduction passage is formed into a substantially constant shape, and piezoelectric elements are attached to the bottom surfaces of the long sides of the ultrasonic conduction passage. , Each of the piezoelectric elements is polarized in the thickness direction thereof, and is half the length λ (where λ is equal to the wavelength of the standing wave generated in the ultrasonic conducting path) of the ultrasonic conducting path. The polarization directions are alternately different depending on the length, and each piezoelectric element is aligned with the ultrasonic conduction path. Are arranged at positions relatively displaced by an odd multiple of λ / 4, and the width of the ultrasonic conduction path is an odd multiple of λ / 4. motor.