JPH08126358A - Ultrasonic motor - Google Patents

Abstract

PURPOSE: To drive an ultrasonic motor two-dimensionally by positioning slide members to the intersections of antinode positions of second move vibrations and antinode positions of fourth mode vibrations so that the members can commonly use first- and second-direction relative motion fetching sections. CONSTITUTION: Four electromechanical conversion elements and four slide members 3a-3d are respectively stuck to the front and rear surfaces of an elastic body 1. The members 3a-3d are positioned to the intersections of the antinode positions of quaternary flexural vibrations B4 and those of sextic flexural vibrations so that the members 3a-3d can commonly use X-and Y-direction relative motion fetching sections. In response to the input of a first-frequency voltage, first and second mode vibrations degenerate and generate elliptic motions so as to cause first-direction relative motions and, in response to the input of a second-frequency voltage, third and fourth mode vibrations degenerate and generate elliptic motions so as to cause second-direction relative motions against an object. As a result, an ultrasonic motor can be driven two- dimensionally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor which produces an elliptical motion in an elastic body to obtain a driving force.

[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 vibrator 102 for vibration is arranged at one end of a rod-shaped elastic body 101, and a transformer 103 for vibration suppression is arranged at the other end.
The vibrators 102a and 103 are respectively provided in the vibrators 102a and 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 is a rectangular flat plate-shaped member,
Protrusion-shaped driving force extracting portions 1a and 1b are formed on one surface. The driving force extracting portions 1a and 1b are provided at antinodes of the bending vibration B4 mode generated in the elastic body 1, and are pressed against an object such as a guide rail.
The electromechanical conversion elements 2a and 2b are elements that convert electric energy into mechanical energy, and are attached to the other surface of the elastic body 1 to cause the elastic body 1 to generate a longitudinal vibration L1 mode and a bending vibration B4 mode.

[0007]

Next, the principle of operation of the motor shown in FIG. 5, which has been clarified by the present inventors, will be described, and the problems will be referred to. FIG. 6 is a diagram for explaining the driving principle of the modified degenerate vertical L1-bending B4 mode flat plate motor shown in FIG. As shown in FIG. 6 (A), this ultrasonic motor causes high frequency voltages A and B to be applied to the two electromechanical conversion elements 2a and 2b, thereby causing a combined vibration of bending vibration and longitudinal vibration. Drive force extraction part 1
An elliptic motion is generated at the tips of a and 1b to generate a driving force. Here, G is the ground.
Further, the two electromechanical conversion elements 2a and 2b are polarized so that the polarities thereof are in the same direction, and the high frequency voltages A and B are polarized.
Has a temporal phase difference of π / 2.

FIG. 6 (A) 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. 6A indicates the effective value of the high frequency voltage. FIG. 6B shows how the cross section of the ultrasonic motor is deformed, and shows a temporal change (t1 to t9) of bending vibration generated in the ultrasonic motor. FIG. 6C shows how the cross section of the ultrasonic motor is deformed, and shows the temporal change (t1 to t9) of the longitudinal vibration generated in the ultrasonic motor. FIG. 6D 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 will be described for each time change (t1 to t9). At time t1, as shown in FIG. 6A, 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. 6B, the bending movements due to the high frequency voltages A and B cancel each other out, and the masses Y1 and Z1 have zero amplitude. Further, as shown in FIG. 6C, the longitudinal vibration due to the high frequency voltages A and B is 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 FIG. 6 (D), both of the above vibrations are combined, the movement of the mass points Y1 and Y2 is combined into the movement of the mass point Y, and the movement of the mass points Z1 and Z2 is combined into the mass point Z. Exercise.

At time t2, as shown in FIG. 6A, the high frequency voltage B becomes zero and the high frequency voltage A generates a positive voltage. As shown in FIG. 6 (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. 6C, 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. 6 (D), both of the above vibrations are combined, and the mass Y
And Z move clockwise relative to the time t1.

At time t3, as shown in FIG. 6 (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. 6 (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. 6C, the longitudinal vibrations due to the high frequency voltages A and B cancel each other out, and the mass points Y2 and Z2 are cancelled.
And return to their original positions. As a result, as shown in FIG. 6 (D), both of the above vibrations are combined, and the mass points Y and Z move clockwise relative to the time t2.

At time t4, the high frequency voltage A becomes zero and the high frequency voltage B produces a negative voltage as shown in FIG. 6 (A). As shown in FIG. 6 (B), a bending motion occurs due to 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. 6 (C), longitudinal vibration is generated by the high frequency voltage B, and the mass points Y2 and Z2 contract.
As a result, as shown in FIG. 6 (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. 6 (A), the high frequency voltage A produces a negative voltage, and the high frequency voltage B produces the same negative voltage. As shown in FIG. 6B, the bending movements due to the high frequency voltages A and B cancel each other out, and the masses Y1 and Z1 have zero amplitude. In addition, 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. 6 (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 changes from t6 to t9,
Similar to the above-described principle, bending vibration and longitudinal vibration are generated, and as a result, as shown in FIG. 6D, the mass points Y and Z move clockwise and make an elliptic motion. Based on the above principle, the ultrasonic motor is configured to generate an elliptic motion at the tips of the driving force extracting portions 1a and 1b to obtain the driving force. Therefore, when the tips of the driving force extracting portions 1a and 1b are pressed against an object (not shown), the elastic body 1 moves relative to the object.

However, in the above-described motor shown in FIG. 5, the direction in which the elliptic motion occurs is determined by the size of the elastic body 1 and the positions where the electromechanical conversion elements 2a and 2b are attached. There was a problem that it could only be driven.

An object of the present invention is to solve the above-mentioned problems and to provide an ultrasonic motor which can be driven in a two-dimensional direction with a simple structure.

[0017]

To achieve the above object, the present invention according to claim 1 comprises an elastic body and an electromechanical conversion element coupled to the elastic body. In response to the first frequency voltage input to the elastic body, the first-mode vibration and the second-mode vibration generated in the elastic body degenerate to generate elliptical vibrations, and the object comes into contact with the elastic body. And a relative motion in a first direction between them and in response to a second frequency voltage input to the electromechanical conversion element,
The vibration of the third mode and the vibration of the fourth mode generated in the elastic body are degenerated to generate elliptical vibration, and relative movement in a second direction different from the first direction is generated between the object and the object. It is an ultrasonic motor to generate | occur | produce, Comprising: The extraction part of the relative motion of the said 1st direction and the said 2nd direction are the position of the intersection of the antinode position of the said 2nd mode vibration, and the antinode position of the said 4th mode vibration. It is characterized in that it is arranged so as to be shared with the taking-out portion for the relative motion of.

According to a second aspect of the invention, in the ultrasonic motor according to the first aspect, the first mode vibration and the third mode vibration are longitudinal vibrations, and the second mode vibration and the second mode vibrations are longitudinal vibrations. It is characterized in that the four modes of vibration are bending vibrations.

According to a third aspect of the present invention, in the ultrasonic motor according to the second aspect, the order of modes of the second mode vibration and the fourth mode vibration is different.

According to a fourth aspect of the invention, in the ultrasonic motor according to the second aspect, the vibration of the first mode and the vibration of the third mode are primary longitudinal vibrations, and the vibration of the second mode. Is a fourth-order bending vibration, and the vibration of the fourth mode is a sixth-order bending vibration.

[0021]

In the present invention, in response to the input of the first frequency voltage, the vibration of the first mode and the vibration of the second mode degenerate to generate elliptical vibration, and the first vibration is generated between the vibration and the object. Responsive to the input of the second frequency voltage, the third
The mode vibration and the fourth mode vibration degenerate to generate elliptical vibration, which causes relative motion in the second direction with the object. At this time, the antinode position of the vibration in the second mode and the fourth position
Since the extraction part for the relative motion in the first direction and the extraction part for the relative motion in the second direction are arranged in common at the position of the intersection with the antinode position of the mode vibration, it is possible to drive in the two-dimensional direction. .

[0022]

The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a plan view, a side view, a front view and a bottom view of a main body of an embodiment of an ultrasonic motor according to the present invention, which is drawn by trigonometry. The ultrasonic motor of this embodiment includes an elastic body 1, electromechanical conversion elements 2a to 2d,
It is composed of sliding members 3a to 3d and the like. Elastic body 1
Is a plate-shaped member, and the material thereof is metal such as stainless steel or aluminum alloy, or plastic. In this embodiment, the elastic body 1 has a thickness H, a length Wx, and a width Wy. The elastic body 1 has four electromechanical conversion elements 2a to 2d on its surface.
However, four sliding members 3a to 3d are attached to the back surface, respectively.

The electromechanical conversion elements 2a to 2d are elements for converting electric energy into mechanical energy, and for example, piezoelectric elements such as PZT or electrostrictive elements such as PMN are used. The sliding members 3a to 3d are provided in portions that come into contact with an object (not shown) and that extract the driving force from the elastic body 1. As the sliding members 3a to 3d, a plastic containing ethylene tetrafluoride resin (for example, Teflon: trade name of DuPont), molybdenum disulfide, or the like is used.

This ultrasonic motor has an electromechanical conversion element 2
When a frequency voltage is applied to a to 2d, elliptical vibration occurs at the position where the sliding members 3a to 3d of the elastic body 1 are attached, and the sliding members 3a to 3d press against an object (not shown). Due to the contact, a relative motion is generated between the object and the object.

FIG. 2 is a block diagram showing a drive circuit of an embodiment of the ultrasonic motor according to the present invention. In FIG.
11 is an input frequency indicator, 12 is an oscillator, 13 is a phase shift indicator, 14 is a phase shifter, 15 and 16 are amplifiers, 17 is X-.
The Y direction indicator, 18 to 21 are analog switches.

When it is desired to move the ultrasonic motor in the (+) direction of (X), first, the XY direction indicating section 17 is provided.
Set (X) by using the analog switches 18 and 2
0 is turned on and the analog switches 19 and 21 are turned off to group the electromechanical conversion elements 2a and 2c integrally and the electromechanical conversion elements 2b and 2d integrally.

Next, the phase shift instructing section 13 sets (+), and the phase shifter 14 shifts the phase by + π / 2. In this state, when the XY direction instructing unit 17 instructs the input frequency instructing unit 11 to drive in the (X) direction, the input frequency instructing unit 11 instructs the oscillator 12 to the first frequency. When the first frequency signal is output from the oscillator 12, one is amplified by the amplifier 16 and input to the electromechanical conversion elements 2b and 2d. The other phase is shifted by + π / 2 by the phase shifter 14, amplified by the amplifier 15, and input to the electromechanical conversion elements 2a and 2c.
As a result, first-order longitudinal vibration and sixth-order bending vibration are generated in the elastic body 1, and these two types of vibration are degenerated, and the sliding members 3a to 3d of the elastic body 1 are attached. Elliptical vibration is generated at the position, which causes relative movement in the (X) (+) direction with the object.

When it is desired to move the ultrasonic motor in the (-) direction of (X), first, (X) is set by the XY direction indicator 17 and the analog switches 18 and 20 are turned ON. And analog switches 19 and 21
Is turned off to group the electromechanical conversion elements 2a and 2c integrally and the electromechanical conversion elements 2b and 2d integrally.

Next, the phase shift instructing section 13 sets (-), and the phase shifter 14 shifts the phase by -π / 2. In this state, when the XY direction instructing unit 17 instructs the input frequency instructing unit 11 to drive in the (X) direction, the input frequency instructing unit 11 instructs the oscillator 12 to the first frequency. When the first frequency signal is output from the oscillator 12,
One is amplified by the amplifier 16 and input to the electromechanical conversion elements 2b and 2d. The other phase is shifted by -π / 2 by the phase shifter 14, is amplified by the amplifier 15, and is input to the electromechanical conversion elements 2a and 2c. As a result, first-order longitudinal vibration and sixth-order bending vibration are generated in the elastic body 1, and these two types of vibration are degenerated, and the sliding members 3a to 3d of the elastic body 1 are attached. Elliptical vibration is generated at the position, and a relative motion is generated between the object and the object in the (-) direction (X).

Further, when it is desired to move this ultrasonic motor in the (+) direction of (Y), first, (Y) is set by the XY direction indicating section 17, and the analog switches 19 and 21 are turned on. And analog switches 18 and 20
Is turned off to group the electromechanical conversion elements 2a and 2b integrally and the electromechanical conversion elements 2c and 2d integrally.

Next, the phase shift instructing section 13 sets (+) and the phase shifter 14 shifts the phase by + π / 2. In this state, when the XY direction instructing unit 17 instructs the input frequency instructing unit 11 to drive in the (Y) direction, the input frequency instructing unit 11 instructs the oscillator 12 to the second frequency.
When the second frequency signal is output from the oscillator 12, one is amplified by the amplifier 16 and input to the electromechanical conversion elements 2c and 2d. The other phase is shifted by + π / 2 by the phase shifter 14, amplified by the amplifier 15, and input to the electromechanical conversion elements 2a and 2b.
As a result, first-order longitudinal vibration and fourth-order bending vibration are generated in the elastic body 1, and these two types of vibration are degenerated, and the sliding members 3a to 3d of the elastic body 1 are attached. Elliptical vibration is generated at the position, and a relative motion is generated in the (Y) (+) direction with respect to the object.

Finally, when it is desired to move the ultrasonic motor in the (-) direction of (Y), first, (Y) is set by the XY direction indicating section 17, and the analog switches 19 and 21 are set. Turn on, analog switches 18 and 20
Is turned off to group the electromechanical conversion elements 2a and 2b integrally and the electromechanical conversion elements 2c and 2d integrally.

Next, the phase shift instructing section 13 sets (-) and the phase shifter 14 shifts the phase by -π / 2. In this state, when the XY direction instructing unit 17 instructs the input frequency instructing unit 11 to drive in the (Y) direction, the input frequency instructing unit 11 instructs the oscillator 12 to the second frequency.
When the second frequency signal is output from the oscillator 12, one is amplified by the amplifier 16 and input to the electromechanical conversion elements 2c and 2d. The other phase is shifted by -π / 2 by the phase shifter 14, is amplified by the amplifier 15, and is input to the electromechanical conversion elements 2a and 2b.
As a result, first-order longitudinal vibration and fourth-order bending vibration are generated in the elastic body 1, and these two types of vibration are degenerated, and the sliding members 3a to 3d of the elastic body 1 are attached. Elliptical vibration is generated at the position, which causes relative movement in the (Y) (-) direction with the object.

FIG. 3 is a diagram for explaining the principle of driving the ultrasonic motor of the present invention in the X and Y directions, respectively. When the length Wx of the elastic body 1 is set to Wx = 32 · π · H / (12) ^1/2 , the resonance frequency ΩL1X of the first-order longitudinal vibration is E, the longitudinal elastic coefficient of the elastic body 1, and ρ is the density. when, the Omegaeru1X = [π · (E / ρ) ^1/2] / (2 · Wx) = [(12 · E / ρ) ^1/2] / (64 · H).

Further, the resonance frequency of the 6th bending vibration ΩB6X
Is ΩB6X = [16 · π · π · (E · I / ρ · A) ^1/2 ] / (Wx · Wx), where I is the second moment of area of the elastic body 1 and A is the sectional area. = [(12 · E / ρ) ^1/2 ] / (64 · H), and it can be seen that the first-order longitudinal vibration and the sixth-order bending vibration coincide with each other and degenerate. Therefore, [(12 · E /
By inputting the frequency of ρ) ^1/2 ] / (64 · H), the ultrasonic motor is driven in the X direction (left and right direction of the paper surface).

Next, when the width Wy of the elastic body 1 is set to Wy = 72 · π · H / (12) ^1/2 , the resonance frequency ΩL1Y of the first-order longitudinal vibration is E , ΩL1Y = [π · (E / ρ) ^1/2 ] / (2 · Wy) = [(12 · E / ρ) ^1/2 ] / (144 · H), where ρ is the density .

Further, the resonance frequency of the fourth-order bending vibration ΩB4Y
Is ΩB4Y = [16 · π · π · (E · I / ρ · A) ^1/2 ] / (Wy · Wy), where I is the second moment of area of the elastic body 1 and A is the sectional area. = [(12 · E / ρ) ^1/2 ] / (144 · H), and it can be seen that the first-order longitudinal vibration and the fourth-order bending vibration are coincident and degenerate. Therefore, [(12 · E /
By inputting the frequency of ρ) ^1/2 ] / (144 · H), the ultrasonic motor is driven in the Y direction (vertical direction of the paper surface).

Naturally, the input frequency for driving in the X direction [(12 · E / ρ) ^1/2 )] / (64 · H),
Input frequency for driving in Y direction [(12 · E / ρ)
Since it is different from ^1/2 ] / (144 · H), driving in the X direction and driving in the Y direction can be selected.

To be precise, the electromechanical conversion elements 2a ...
It is necessary to obtain the resonance frequency in consideration of the influence of 2d and the sliding members 3a to 3d, but it is omitted here because it is a considerably complicated calculation.

In the present embodiment, as shown in FIG. 3, the sliding members 3a to 3d have the antinode position of the vibration of the fourth bending vibration B4 (corresponding to the vibration of the third mode) and the sixth bending. Vibration B6
Of the relative movement in the X direction (corresponding to the first direction) and the Y direction (corresponding to the second direction) at the position of the intersection with the antinode position of the vibration (corresponding to the vibration of the fourth mode). It is arranged so as to be shared with the taking-out portion for relative movement.

[0041]

As described above, according to the present invention, the first mode vibration and the second mode vibration are degenerated in response to the input of the first frequency voltage, and elliptical vibration is generated to generate the elliptic vibration. In the first
In a second direction relative to the object by causing a relative motion in a directional direction and degenerating the third mode vibration and the fourth mode vibration in response to the input of the second frequency voltage to generate an elliptical vibration. A motion is generated so that the extraction portion for the relative motion in the first direction and the extraction portion for the relative motion in the second direction are shared at the intersection of the antinode position of the second mode vibration and the antinode position of the fourth mode vibration. Since it is arranged in the above, there is an effect that an ultrasonic motor that can be driven in a two-dimensional direction can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view, a side view, a front view and a bottom view in which an embodiment of an ultrasonic motor according to the present invention is drawn by trigonometry.

FIG. 2 is a block diagram showing a drive circuit of the ultrasonic motor according to the present embodiment.

FIG. 3 is a diagram for explaining the principle of driving the ultrasonic motor of the present invention in each of the X direction and the Y direction.

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

FIG. 5 is a schematic view showing a conventional example of a modified degenerate vertical L1-bending B4 mode flat plate motor, and FIG.
5B is a side view and FIG. 5C is a plan view.

FIG. 6 shows the modified degenerate vertical L1-bending B4 mode shown in FIG.
It is a figure explaining the drive principle of a flat plate motor.

[Explanation of symbols]

 1: Elastic body 2, 2a to 2d: Electromechanical conversion element 3, 3a to 3d: Sliding member 11: Input frequency indicator 12: Oscillator 13: Phase shift indicator 14: Phase shifter 15, 16: Amplifier 17: XY direction indicator 18 to 21: analog switch

Claims (4)

[Claims] 1. An elastic body and an electromechanical conversion element coupled to the elastic body, wherein a first frequency voltage is generated in the elastic body in response to a first frequency voltage input to the electromechanical conversion element. The first-mode vibration and the second-mode vibration degenerate to generate elliptical vibration, which causes a relative motion in the first direction between the elastic body and an object in contact with the electromechanical conversion element. In response to the input second frequency voltage, the vibration of the third mode and the vibration of the fourth mode generated in the elastic body are degenerated to generate elliptical vibration, and between the target and the object, An ultrasonic motor that produces relative motion in a second direction different from the first direction, wherein the first motor is provided at a position of an intersection of an antinode position of the second mode vibration and an antinode position of the fourth mode vibration. Direction relative movement extracting portion and the second direction relative movement extracting portion The ultrasonic motor is characterized in that it is arranged so as to be shared. 2. The ultrasonic motor according to claim 1, wherein the vibration of the first mode and the vibration of the third mode are longitudinal vibrations, and the vibration of the second mode and the vibration of the fourth mode. An ultrasonic motor characterized in that is a bending vibration. 3. The ultrasonic motor according to claim 2, wherein the second mode vibration and the fourth mode vibration have different mode orders. 4. The ultrasonic motor according to claim 2, wherein the first mode vibration and the third mode vibration are primary longitudinal vibrations, and the second mode vibration is a quaternary bending. An ultrasonic motor, wherein the vibration of the fourth mode is a bending vibration of sixth order.