JPH07143770A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To reduce the supporting loss while sustaining the oscillation as intact as possible both in longitudinal oscillation mode and bending oscillation mode. CONSTITUTION:The ultrasonic motor comprises an elastic body 11 and piezoelectric elements 12, 13 coupled with the elastic body wherein the piezoelectric elements 12, 13 cause oscillation of the elastic body 11 in longitudinal and bending oscillation modes and the combined oscillation causes elliptical motion to produce driving force from a predetermined position of the elastic body 11. The ultrasonic motor further comprises means 15, 16, 17, 18 for supporting the elastic body at the position 14 where the node of longitudinal oscillation mode matches the node of bending oscillation mode and its vicinity.

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 producing a driving force by generating an elliptical motion in a rod-shaped elastic body, and more particularly,
The present invention relates to an ultrasonic motor that drives a longitudinal vibration mode and a bending vibration mode in two phases.

[0002]

2. Description of the Related Art FIG. 4 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. 5 is a schematic view showing a conventional example of a modified degenerate vertical L1-bending B4 mode flat plate motor.
5A is a front view, FIG. 5B is a side view, and FIG. 5C 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 pressed against a guide rail (not shown).

[0007]

However, the above-mentioned FIG.
In this motor, since vibrations in two modes of a longitudinal vibration mode and a bending vibration mode are generated in the elastic body 1, there is a problem that if the elastic body 1 is not properly supported, the generated vibrations are attenuated. there were.

An object of the present invention is to solve the above-mentioned problems and to provide an ultrasonic motor in which the supporting loss is reduced without damaging the vibration in both the longitudinal vibration mode and the bending vibration mode as much as possible. Is to provide.

[0009]

In order to solve the above-mentioned problems, a first solution of the ultrasonic motor according to the present invention comprises an elastic body (1) and an electromechanical conversion element coupled to the elastic body ( 2 and 3), the electromechanical conversion element causes the elastic body to generate a longitudinal vibration mode and a bending vibration mode, and an elliptic motion generated by a combined vibration of them causes
In an ultrasonic motor that obtains a driving force from a predetermined position of the elastic body, a supporting unit that supports the elastic body at a position where the node of the longitudinal vibration mode and the node of the bending vibration mode coincide with each other and a position around the position. 14, 15, 16, 17, 18)
It is characterized by having.

A second solving means is the ultrasonic motor of the first solving means, wherein the supporting means supports a substantially central portion of the elastic body in a longitudinal vibration direction.

A third solving means can be characterized in that, in the ultrasonic motor of the first solving means, the supporting means presses and contacts the elastic body against the fixing portion.

A fourth solving means can be characterized in that, in the ultrasonic motor of the first solving means, the supporting means presses the elastic body into the fixing portion to bring it into pressure contact.

[0013]

According to the present invention, the longitudinal vibration mode node and the flexural vibration mode node are supported at a position where the node and the periphery of the node coincide with each other. Also, it is possible to perform support with little support loss with almost no attenuation.

[0014]

Embodiments Embodiments will be described in more detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a first embodiment of an ultrasonic motor according to the present invention. Elastic body 11
Has a base 11a and two protrusions 11b and 11c, and the base 11a has piezoelectric elements 12 and 1 for generating a longitudinal vibration L1 mode and a bending vibration B4 mode.
3 are arranged. The function of each element is similar to that shown in FIG. 5 described above. In this embodiment, the piezoelectric element 1
2 and 13 are polarized as shown in FIG. 1B, and two-phase input voltages A and B as shown in FIG.

The elastic body 11 is provided at the center of the base portion 11a.
A pair of pins 14 are arranged. As will be apparent from FIG. 2, which will be described later, this position is a position where both vibrations of the longitudinal vibration L1 mode and the bending vibration B4 mode become nodes. This pin 1
The position 4 is the center position of the elastic body 11 in the thickness direction and the length direction. Therefore, supporting this position and its periphery is most suitable from the viewpoint of supporting efficiency.

The support member 15 is a pressing means (for example, a spring).
The pin 14 is separated from the fixing portion 20 via the bearing 16 (for example, rollers) 17 and 18 and the fixing portion 19 is pressed in a pressing direction. The pressed elastic body 11 is 2
The tips of the two protrusions 11b and 11c come into pressure contact with the fixed portion 19, and relative movement occurs between the two protrusions 11b and 11c and the fixed portion 19.

As shown in FIG. 1, this ultrasonic motor is
By applying high-frequency voltages A and B to the two piezoelectric elements 12 and 13, a composite vibration of bending vibration and longitudinal vibration is caused, thereby causing elliptical motion at the tips of the protrusions 11b and 11c, and driving force. Is configured to generate.
Here, G is the ground. In addition, the two piezoelectric elements 1
2 and 13 are polarized so that their polarities are in the same direction, and the high frequency voltages A and B have a time phase difference of π / 2. The polarizations of the two piezoelectric elements 12 and 13 may be opposite to each other.

FIG. 2A shows time changes of the two-phase high frequency voltages A and B input to the ultrasonic motor at t1 to 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. FIG. 2C shows how the cross section of the ultrasonic motor is deformed, and shows the temporal changes (t1 to t9) of the longitudinal vibration generated in the ultrasonic motor. FIG. 2D shows the protrusions 11b and 11 of the ultrasonic motor.
3 shows temporal changes (t1 to t9) of the elliptic motion generated in c and c.

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 generates 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. 2A, 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 generate a driving force. Therefore, the tips of the protrusions 11b and 11c are fixed to the stator 19
When pressure is applied to the elastic body 11, the elastic body 11 is self-propelled with respect to the fixed portion 19.

FIG. 3 shows a second ultrasonic motor according to the present invention.
It is a schematic diagram showing an example of. The parts having the same functions as those in the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted. The supporter 21 pressurizes the pin 14A in the direction of drawing it into the fixing portion 25 via the pressing means (spring) 22 and the bearing members (rollers) 23 and 24. The support 21, the pressing means 22, the bearing member 2
The pins 3 and 24 are also provided on the pin 14B on the side opposite to the pin 14A. In the pressurized elastic body 11, the tips of the two protrusions 11b and 11c come into pressure contact with the fixed portion 25, and the relative movement between the two protrusions 11b and 11c and the fixed portion 25 occurs. Occur.

The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also included in the present invention. For example, the elastic body 11 may be pressed against the fixed portion 19 by its own weight.

[0027]

As described above in detail, according to the present invention, the vertical vibration mode is supported by utilizing the position where the longitudinal vibration mode node and the flexural vibration mode node coincide with each other and the periphery thereof. There is an effect that it is possible to perform the support with a small support loss, while almost not dampening the vibration of both the mode and the bending vibration mode.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first 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 first embodiment.

FIG. 3 is a schematic diagram showing a second embodiment of the ultrasonic motor according to the present invention.

FIG. 4 is a diagram showing a conventional example of a linear ultrasonic motor.

FIG. 5 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 piezoelectric element 14 pin

Claims (4)

[Claims] 1. An elastic body and an electromechanical conversion element coupled to the elastic body, wherein the electromechanical conversion element generates a longitudinal vibration mode and a bending vibration mode in the elastic body, and combines them. In an ultrasonic motor that obtains a driving force from a predetermined position of the elastic body by an elliptical motion caused by vibration, the elasticity is obtained at a position where a node of the longitudinal vibration mode and a node of the bending vibration mode coincide with each other and a peripheral position thereof. An ultrasonic motor comprising a support means for supporting a body. 2. The ultrasonic motor according to claim 1, wherein the supporting means supports a substantially central portion of the elastic body in a longitudinal vibration direction. 3. The ultrasonic motor according to claim 1, wherein the supporting means presses the elastic body against the fixing portion to bring the elastic body into pressure contact. 4. The ultrasonic motor according to claim 1, wherein the supporting means presses the elastic body into contact with the fixed portion so as to bring the elastic body into pressure contact.