JPH07264883A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the driving efficiency of an ultrasonic motor and the occurrence of a performance difference in the motor depending upon the driving direction. CONSTITUTION:An ultrasonic motor is provided with an elastic body 11, polarized first and second piezoelectric materials 12 and 13 which are coupled with the body 11 and make the body 11 to make elliptic motions resulting from the resultant vibration of a longitudinal vibration mode and flexural vibration mode, and unpolarized third piezoelectric material 14 which is coupled with the body 11 and transmits the potential at the body 11 through an electrode 14a provided on the surface of the 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 motor for generating a driving force by generating an oscillating wave in an elastic body using an electromechanical conversion material that has been subjected to a polarization treatment, and more particularly to an elastic body and an electromechanical conversion material. The present invention relates to an ultrasonic motor having an improved coupling structure.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a conventional example of a linear ultrasonic motor. In a conventional linear ultrasonic motor, a vibrating transformer 102 is arranged on one end side of a rod-shaped elastic body 101 and a vibrating transformer 103 is arranged on the other end side.
Each of the transformers 102, 103 includes a vibrator 102a, 103
a is joined. An alternating voltage is applied from the oscillator 102b to the vibrator 102a for vibration to vibrate the rod-shaped elastic body 101, and this vibration propagates through the rod-shaped elastic body 101 to become a traveling wave. Due to this traveling wave, the rod-shaped elastic body 10
The moving body 104 that is brought into pressure contact with 1 is driven.

On the other hand, the vibration of the rod-shaped elastic body 101 is transmitted to the vibrator 103a through the vibration damping transformer 103, and the vibrator 103a converts the vibration energy into electric energy. The load 103b connected to the vibrator 103a consumes the electric energy to absorb the vibration. This vibration damping transformer 103 suppresses the reflection of the end surface of the rod-shaped elastic body 101, and the rod-shaped elastic body 1
The generation of standing waves of 01 eigenmodes is prevented.

The linear type ultrasonic motor shown in FIG.
The length of the rod-shaped elastic body 101 is required only for the moving range of 04, and the whole of the rod-shaped elastic body 101 has to be vibrated, so that the device becomes large and the standing wave of the eigenmode is generated. In order to prevent this, there has been a problem that the vibration damping transformer 103 and the like are required.

In order to solve such problems, various self-propelled ultrasonic motors have been proposed.
The "degenerate vertical L1-bending B4 mode flat plate motor" described in "222 Piezoelectric linear motor for moving optical pickup" in "Proceedings of Dynamics Symposium on Electromagnetic Force" is known.

FIG. 7 is a schematic diagram showing a conventional example of a modified degenerate vertical L1-bending B4 mode flat plate motor.
7A is a front view, FIG. 7B is a side view, and FIG. 7C is a plan view. The elastic body 1 includes a rectangular flat plate-shaped base portion 1a,
Protrusions 1b, 1 formed on one surface of the base 1a
and c. The piezoelectric elements 2 and 3 are elastic bodies 1.
Is an element that is attached to the other surface of the base portion 1a to generate a longitudinal vibration L1 mode and a bending vibration B4 mode. The protrusions 1b and 1c of the elastic body 1 are provided at antinodes of the bending vibration B4 mode generated in the base portion 1a, and are brought into pressure contact with a relative motion member (not shown) to perform relative motion.

[0007]

In the motor as shown in FIG. 6, it is necessary to obtain the electric potential of the elastic body in the design of the motor drive circuit. The applicant of the present invention electrically connects a surface electrode of an electromechanical conversion element (an electromechanical conversion material that has been subjected to a polarization treatment) and an elastic body with a conductive paint, and wires through the surface electrode. It has already been proposed (Japanese Patent Application No. 5-342630).

However, in the above-mentioned proposal, since the surface electrode of the electromechanical conversion element and the elastic body are short-circuited, the electromechanical conversion element portion for transmitting the potential of the elastic body has a damping function. However, there is a problem that the driving efficiency is deteriorated and a performance difference occurs depending on the driving direction.

An object of the present invention is to solve the above-mentioned problems and to provide an ultrasonic motor capable of preventing a decrease in driving efficiency and a performance difference due to a driving direction.

[0010]

In order to solve the above-mentioned problems, the first means for solving the problems of the ultrasonic motor according to the present invention is an elastic body, and the elastic body is coupled to the elastic body and is excited by the elastic body. A first and a second electro-mechanical conversion material that has been subjected to a polarization process for generating an oscillating wave, and a third electrode that is coupled to the elastic body and has an electrode on the surface thereof and is not subjected to the polarization process.
And the electric potential of the elastic body is transmitted via the electrode of the third electromechanical conversion material.

A second solving means is an elastic body and a polarization treatment which is coupled to the elastic body and causes the elastic body to generate an elliptical motion by a combined vibration of a longitudinal vibration mode and a bending vibration mode. The first and second electromechanical conversion materials and the third electromechanical conversion material which is coupled to the elastic body and has an electrode on the surface thereof and which has not been subjected to polarization treatment are provided. Is transmitted through the electrode of the third electromechanical conversion material.

A third solving means is the ultrasonic motor of the first or second solving means, wherein the electrode of the third electromechanical conversion material is electrically connected to the elastic body by a conductive paint. It is characterized by

A fourth solution means, in the ultrasonic motor according to any one of the first to third solution means, is coupled with the elastic body and converts mechanical vibration of the elastic body into an electric signal. It is characterized by having a fourth electromechanical conversion material which has been treated.

A fifth solving means is the ultrasonic motor according to any one of the first to fourth solving means, wherein the first to third electromechanical converting materials or the first to fourth electromechanical converting materials are used. The material is characterized in that it is composed of a single electromechanical conversion material.

[0015]

According to the present invention, since the portion of the third electromechanical conversion material for transmitting the electric potential of the elastic body is not polarized, the third electromechanical conversion material is attenuated. It no longer functions.

[0016]

Embodiments Embodiments will be described in more detail below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of an ultrasonic motor according to the present invention. The elastic body 11 has a base portion 11a and two protruding portions 11b and 11c, and the material thereof is metal such as stainless steel or aluminum alloy, or plastic.

The piezoelectric elements 12 to 15 are bonded to the upper surface of the base portion 11a of the elastic body 11. Piezoelectric elements 12, 13
Is an element that has been subjected to a polarization process in order to generate a longitudinal vibration L1 mode and a bending vibration B4 mode. Electrodes 12a and 13a are printed on the surfaces of the piezoelectric elements 12 and 13, and the electrodes 12a and 13a are attached to the piezoelectric element 12 via the electrodes 12a.
The voltage of the terminal is applied, and the voltage of the terminal B is applied to the piezoelectric element 13 via the electrode 13a. In this embodiment, the piezoelectric elements 12 and 13 are polarized in the thickness direction as shown in FIG. 3, and the polarization directions are the same. Further, the voltage of the A terminal and the voltage of the B terminal have the same frequency and are out of phase with each other by π / 2. The two piezoelectric elements 12, 1
The polarizations of 3 may be opposite to each other.

The piezoelectric element 14 has an electrode 14a burned on its surface, but unlike other piezoelectric elements, since it is not polarized, it does not have an electromechanical conversion function. The electrode 14a is composed of the elastic body 11 and the conductive paint 16
Are electrically connected by.

An electrode 15a is printed on the surface of the piezoelectric element 15, and the vibration state of the elastic body 11 is converted into an electric signal and transmitted to the P terminal via the electrode 15a. This electric signal contains the vibration state of the fourth bending vibration mode and 1
Two vibration modes different from the vibration state of the next longitudinal vibration mode are included in a degenerated form. And the elastic body 11
A signal having a magnitude substantially corresponding to the combined vibration amplitude of is obtained.

As shown in FIG. 3, the piezoelectric elements 11 to 14 have electrodes 11b to 14b burned on the surface opposite to the surface on which the electrodes 11a to 14a are arranged. These electrodes 11b to 14b have the same electric potential as that of the elastic body 11, and the electric potentials thereof are the conductive paint 16 and the electrodes 14
It is transmitted to the G terminal via a. With the above configuration, the potentials of the electrodes 11b to 14b are set to the A terminal,
Wiring can be performed in the same form as the B terminal and the P terminal, and since they are structurally symmetrical, damping does not occur, so driving efficiency does not decrease, and there is no difference in performance depending on the driving direction.

FIG. 2 is a diagram for explaining the operation of the ultrasonic motor according to the present invention. FIG. 2 (A) shows time changes of two-phase high-frequency voltages A and B input to the ultrasonic motor from t1.
It is shown at t9. The horizontal axis of FIG. 2A shows the effective value of the high frequency voltage. FIG. 2B shows how the cross section of the ultrasonic motor is deformed, and shows a temporal change (t1 to t9) of the bending vibration generated in the ultrasonic motor. Figure 2
(C) shows the state of deformation of the cross section of the ultrasonic motor, and changes in longitudinal vibration (t1 to t) generated in the ultrasonic motor.
9) is shown. FIG. 2D shows a temporal change (t1 to t9) of the elliptic motion generated in the protrusions 11b and 11c of the ultrasonic motor.

Next, the operation of the ultrasonic motor of this embodiment will be described for each time change (t1 to t9). Time t
2, the high frequency voltage A generates a positive voltage, and the high frequency voltage B similarly generates the same positive voltage, as shown in FIG. As shown in FIG. 2B, the bending motions due to the high frequency voltages A and B cancel each other out, and the mass point Y1
And Z1 have zero amplitude. Further, as shown in FIG. 2C, the longitudinal vibrations due to the high frequency voltages A and B are generated in the extending direction. The mass points Y2 and Z2 show the maximum elongation around the node X, as indicated by the arrow. As a result,
As shown in (D), the above-mentioned both vibrations are combined, and the mass point Y1
The synthesis of the motion of Y and Y2 becomes the motion of the mass point Y, and the synthesis of the motion of the mass points Z1 and Z2 becomes the motion of the mass point Z.

At time t2, as shown in FIG. 2 (A), the high frequency voltage B becomes zero and the high frequency voltage A generates a positive voltage. As shown in FIG. 2 (B), a bending motion is generated by the high frequency voltage A, the mass point Y1 oscillates in the positive direction, and the mass point Z1 oscillates in the negative direction. Further, as shown in FIG. 2 (C), longitudinal vibration due to the high frequency voltage A occurs, and the mass points Y2 and Z2 contract more than at time t1. As a result, as shown in FIG. 2D, the above-mentioned both vibrations are combined, and the mass Y
And Z move clockwise relative to the time t1.

At time t3, as shown in FIG. 2 (A), the high frequency voltage A generates a positive voltage, and the high frequency voltage B similarly generates the same negative voltage. As shown in FIG. 2 (B), the bending motions due to the high frequency voltages A and B are combined and amplified, and the mass point Y1 is amplified in the positive direction more than at the time t2, showing the maximum positive amplitude value. Mass point Z1 is time t2
It is amplified in the negative direction more than, and shows the maximum negative amplitude value. Further, as shown in FIG. 2C, the longitudinal vibrations due to the high frequency voltages A and B cancel each other out, and the mass points Y2 and Z2
And return to their original positions. As a result, as shown in FIG. 2D, both of the above vibrations are combined, and the mass points Y and Z move clockwise relative to the time t2.

At time t4, as shown in FIG. 2 (A), the high frequency voltage A becomes zero and the high frequency voltage B produces a negative voltage. As shown in FIG. 2 (B), a bending motion is generated by the high frequency voltage B, and the amplitude of the mass point Y1 is lower than that at the time t3, and the amplitude is lower than that at the mass point Z1 time t3. Further, as shown in FIG. 2C, longitudinal vibration due to the high frequency voltage B is generated, and the mass points Y2 and Z2 contract.
As a result, as shown in FIG. 2 (D), both of the above vibrations are combined, and the mass points Y and Z move clockwise relative to the time t3.

At time t5, as shown in FIG. 2 (A), the high frequency voltage A produces a negative voltage, and similarly the high frequency voltage B produces the same negative voltage. As shown in FIG. 2B, the bending motions due to the high frequency voltages A and B cancel each other out, and the masses Y1 and Z1 have zero amplitude. Also, FIG.
As shown in (C), the longitudinal vibration due to the high frequency voltages A and B is generated in the contracting direction. The mass points Y2 and Z2 show the maximum contraction around the node X, as indicated by the arrow. As a result, as shown in FIG. 2 (D), both of the above vibrations are combined, and the mass points Y and Z move clockwise relative to the time t4.

As the time t6 to t9 changes,
Flexural vibrations and longitudinal vibrations are generated in the same manner as the above-described principle, and as a result, as shown in FIG. 2D, the mass points Y and Z move clockwise and make an elliptic motion. Based on the above principle, this ultrasonic motor is configured to generate an elliptic motion at the tips of the protrusions 11a and 11b to extract the driving force.
Therefore, the tips of the protrusions 11b and 11c are attached to the relative motion member 1
When pressure is applied to the elastic body 11,
Self-propelled against.

FIG. 4 is a block diagram showing the drive circuit of the ultrasonic motor according to this embodiment. The oscillator 21 is for oscillating a signal having a frequency corresponding to the first-order longitudinal vibration mode and the fourth-order bending vibration mode of the vibrating body composed of the elastic body 11 and the piezoelectric elements 12 to 15. The output of the oscillator 21 is branched, and one output is amplified by the amplifier 23, and then is output as the B layer voltage to the electrode 13 of the piezoelectric element 13.
Input to a. The other branched output is connected to the phase shifter 22. The phase shifter 22 shifts the phase of the B layer voltage by π / 2 to make it the A layer voltage, and then passes through the amplifier 24. And is input to the electrode 12a of the piezoelectric element 12.

The comparator 25 receives the voltage set by the setting device 26 and the output of the P terminal connected to the piezoelectric element 15, and compares the two, and the output of the P terminal is smaller. In some cases, the oscillator 2 is set so that the frequency is low, and when the output of the P terminal is higher, the frequency is increased.
Control 1 As a result, the vibration amplitude of the ultrasonic motor is maintained at a predetermined magnitude.

FIG. 5 is a view showing the main part of another embodiment of the ultrasonic motor according to the present invention. In addition, the same reference numerals are given to portions that perform the same functions as those in the above-described embodiment,
Overlapping description will be omitted as appropriate. In the embodiment shown in FIG. 3, the piezoelectric elements 12 to 15 are divided, but in this embodiment, the same piezoelectric element 17 is used. The piezoelectric element 17 corresponds to the piezoelectric elements 12 to 15 described above.
Electrodes 12a, 13a, 14a, 15a are formed on the surfaces of the portions 7-12, 17-13, 17-14, 17-15, and one electrode 17b is formed on the opposite surface. In addition, 17-12, 17-1 of the piezoelectric element 17
The portions 3 and 17-15 are polarized as shown in FIG. 5, but the portions 17-14 have no electromechanical conversion function because they are not polarized. In this embodiment, since each piezoelectric element can be formed on one sheet of piezoelectric material, there is no need for positioning on the elastic body 11 and there are advantages such as easy attachment work.

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 the electromechanical conversion element, the piezoelectric element has been described as an example, but an electrostrictive element may be used. Further, as the different vibration modes, the vibration of the L1-B4 mode has been described as an example, but other modes such as L1-B2, L1-B6, L2-B4 may be used. The example of the L1-B4 mode vibration has been described, but by the electromechanical conversion element,
The same can be applied to an annular ultrasonic motor that generates a progressive vibration wave on the surface of an elastic body. However, in this case, the difference in performance in the driving direction does not cause a problem, so only the reduction in driving efficiency is improved. Although the self-propelled example has been described, the elastic body side may be fixed and the long relative movement member may be moved.

[0032]

As described above in detail, according to the present invention, the electromechanical conversion material portion for transmitting the potential of the elastic body is not subjected to the polarization treatment, so that the damping function is achieved. And the driving efficiency is reduced, and there is no difference in performance depending on the driving direction. Further, the potential of the electrode formed on the third electromechanical conversion element can be wired in the same form as the electrodes of the first, second, and fourth electromechanical conversion elements. Furthermore, since the structure is symmetrical, there is no difference in performance depending on the driving direction.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a diagram illustrating a driving operation of the ultrasonic motor according to the present embodiment.

FIG. 3 is a detailed view of a piezoelectric element and an electrode portion of the ultrasonic motor according to this embodiment.

FIG. 4 is a block diagram showing a drive circuit of the ultrasonic motor according to the present embodiment.

FIG. 5 is a detailed view showing a piezoelectric element and an electrode portion of another embodiment of the ultrasonic motor according to the present invention.

FIG. 6 is a diagram showing a conventional example of a linear ultrasonic motor.

FIG. 7 is a schematic view showing an example of a modified degenerate vertical L1-bending B4 mode flat plate motor.

[Explanation of symbols]

 11 Elastic body 12, 13, 14, 15 Piezoelectric element 16 Conductive paint 17 Relative motion member 21 Oscillator 22 Phase shifter 23, 24 Amplifier 25 Comparator 26 Setting device

Claims (5)

[Claims] 1. An elastic body, first and second electromechanical conversion materials that are coupled to the elastic body, and are subjected to a polarization process to generate a vibration wave in the elastic body by excitation thereof, and the elastic body. A non-polarized third electromechanical conversion material that is coupled to the surface of the elastic body and has an electrode on the surface thereof, and the potential of the elastic body passes through the electrode of the third electromechanical conversion material. An ultrasonic motor characterized by being transmitted. 2. An elastic body, and first and second polarization-processed members that are coupled to the elastic body and cause the elastic body to generate an elliptical motion by a combined vibration of a longitudinal vibration mode and a bending vibration mode. An electromechanical conversion material and a third electromechanical conversion material which is coupled to the elastic body and is provided with an electrode on the surface thereof and which is not subjected to polarization treatment are provided, and the potential of the elastic body is the third electromechanical conversion material. An ultrasonic motor, characterized in that it is transmitted through electrodes of electromechanical conversion material. 3. The ultrasonic motor according to claim 1 or 2, wherein the electrode of the third electromechanical conversion material is electrically connected to the elastic body by a conductive paint. Characteristic ultrasonic motor. 4. The ultrasonic motor according to any one of claims 1 to 3, wherein a polarization process is performed to combine with the elastic body and convert mechanical vibration of the elastic body into an electric signal. An ultrasonic motor having the fourth electromechanical conversion material described above. 5. The ultrasonic motor according to any one of claims 1 to 4, wherein the first to third electromechanical conversion materials or the first to fourth electromechanical conversion materials are used.
The electro-mechanical conversion material of is composed of a single electro-mechanical conversion material.