JP2005261080A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch the direction of movement by a frequency change by single-phase excitation related to an actuator that oscillates an oscillating body by the oscillation of a piezoelectric element and drives a driven member. <P>SOLUTION: This actuator, which oscillates the oscillating body by the oscillation of the piezoelectric element and drives the driven member by the oscillation of the oscillating body, is characterized in that first and second protrusions that contact with the driven member and are different in resonance frequencies are formed at the driven member side of the oscillating body at an interval so as to be inclined while reversely opposing each other, and the resonance frequency of the piezoelectric element is an intermediate value of the resonance frequencies of the first and the second protrusions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an actuator that drives a driven member by vibrating a vibrating body by vibration of a piezoelectric element.

2. Description of the Related Art Conventionally, as an ultrasonic linear motor that drives a driven member by vibrating a vibrating body by vibration of a piezoelectric element, for example, one disclosed in JP-A-2003-180091 is known.
In this ultrasonic linear motor, three vibration elements are attached to an elastic body, and the driven body is driven by applying high frequency voltages having the same frequency and different phases to the three vibration elements.
JP 2003-180091 A

However, in the above-described ultrasonic linear motor, three vibration elements are attached to the elastic body, and the traveling direction is switched by applying high-frequency voltages having the same frequency and different phases to the three vibration elements. However, there is a problem that the size of the ultrasonic linear motor is increased.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an actuator capable of switching the traveling direction by a frequency change caused by single-phase excitation.

  The actuator according to claim 1 is an actuator that vibrates a vibrating body by vibration of a piezoelectric element and drives a driven member by vibration of the vibrating body, and contacts the driven member on the driven member side of the vibrating body. The first protrusion and the second protrusion having different resonance frequencies are formed to be inclined in opposite directions at an interval, and the resonance frequency of the piezoelectric element is set to be equal to the resonance frequency of the first protrusion. It is a value between the resonance frequency of the second protrusions.

An actuator according to a second aspect is the actuator according to the first aspect, wherein the resonance frequency of the first protrusion and the resonance frequency of the second protrusion are determined by the magnitude of the first protrusion and the second protrusion. It is characterized by being made different by making it different.
The actuator according to claim 3 is the actuator according to claim 1 or 2, wherein the first protrusion and the second protrusion are formed to be inclined outward. .

According to a fourth aspect of the present invention, in the actuator according to any one of the first to third aspects, the tips of the first protrusion and the second protrusion are formed in an arc shape. And
The actuator according to a fifth aspect is the actuator according to any one of the first to fourth aspects, wherein the vibrating body is provided on both sides of the main body portion on which the first protrusion and the second protrusion are formed. It has a fixing part, and a constriction part is formed between the main part and the fixing part.

The actuator according to claim 6 is the actuator according to any one of claims 1 to 5, wherein the vibrating body is made of a conductive metal, and the first protrusion and the second protrusion are formed. There are fixing portions on both sides of the main body portion, and the fixing portions are fixed to a conductive support member.
The actuator according to a seventh aspect is the actuator according to any one of the first to sixth aspects, wherein the piezoelectric element is a bulk piezoelectric element.

An actuator according to an eighth aspect is the actuator according to the seventh aspect, wherein the piezoelectric element has a stepped shape having a small cross-sectional area on the vibrating body side.
The actuator according to claim 9 is the actuator according to any one of claims 1 to 8, wherein the actuator is a micro ultrasonic linear motor, and the driven member is a slider driven linearly. Features.

(Function)
In the actuator according to the first aspect, for example, the resonance frequency of the first protrusion is set smaller than the resonance frequency of the second protrusion. When the piezoelectric element is longitudinally vibrated at a driving frequency between the resonance frequency of the first protrusion and the resonance frequency of the piezoelectric element, flexural vibration is generated in the first protrusion, and the driven member becomes the first protrusion. Moved to the side.

On the other hand, when the piezoelectric element is longitudinally vibrated at a driving frequency between the resonance frequency of the second protrusion and the resonance frequency of the piezoelectric element, flexural vibration is generated in the second protrusion and the driven member becomes the second protrusion. Moved to the side.
In the actuator according to the second aspect, the resonance frequency of the first protrusion and the resonance frequency of the second protrusion are made different from each other by changing the sizes of the first protrusion and the second protrusion. The

In the actuator according to the third aspect, the driven member is brought into contact with the first protrusion and the second protrusion that are inclined outward.
In the actuator according to the fourth aspect, the driven member is brought into contact with the tips of the first protrusion and the second protrusion formed in an arc shape.
In the actuator according to the fifth aspect, the fixing portions are formed on both sides of the main body portion where the first protruding portion and the second protruding portion are formed via the constricted portion.

In the actuator according to the sixth aspect, the vibrating body and the support member have conductivity, and a voltage is applied between the piezoelectric element and the support member.
In the actuator according to the seventh aspect, a bulk piezoelectric element capable of applying a voltage larger than that of the piezoelectric thin film is used as the piezoelectric element.
In the actuator according to the eighth aspect, the piezoelectric element has a step shape having a small cross-sectional area on the vibrating body side.

  In the actuator according to the ninth aspect, the slider is driven by the micro ultrasonic linear motor.

In the actuator according to the first aspect, the first protrusion and the second protrusion, which are in contact with the driven member and have different resonance frequencies, are formed on the driven member side of the vibrating body with an interval and a reverse inclination. Since the resonance frequency of the piezoelectric element is set to a value between the resonance frequency of the first protrusion and the resonance frequency of the second protrusion, the traveling direction can be switched by a frequency change due to single-phase excitation.
In the actuator of claim 2, since the first protrusion and the second protrusion are made different in size, the resonance frequency of the first protrusion and the resonance frequency of the second protrusion are made different. The resonance frequency can be easily and reliably made different.

In the actuator according to the third aspect, since the first protrusion and the second protrusion are inclined toward the outside, the contact state with the driven member can be stabilized.
In the actuator according to the fourth aspect, since the tip ends of the first protrusion and the second protrusion are formed in an arc shape, even when the first protrusion and the second protrusion are deformed, the driven member is moved to the driven member. The contact state can be kept constant.

In the actuator according to the fifth aspect, since the constricted portion is formed between the main body portion and the fixing portion of the vibrating body, the influence on the vibration of the main body portion caused by fixing the fixing portion can be reduced.
In the actuator according to the sixth aspect, since the vibrating body and the support member are formed of conductive members, the actuator can be operated by applying a voltage between the piezoelectric element and the support member.

In the actuator according to the seventh aspect, since the bulk piezoelectric element is used without using the piezoelectric thin film as the piezoelectric element, it is possible to increase the applied voltage, thereby increasing the output of the actuator.
In the actuator according to the eighth aspect, since the piezoelectric element has a step shape with a small cross-sectional area on the vibrating body side, the primary longitudinal vibration resonance frequency can be set low, and a larger vibration speed can be obtained with the same applied voltage. it can.

  In the actuator according to the ninth aspect, a fine slider can be driven by a fine micro ultrasonic linear motor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show an embodiment of the actuator of the present invention.
The actuator of this embodiment is a micro ultrasonic linear motor, and is a slider in which a driven member is linearly driven.
This actuator includes a piezoelectric element 11 and a vibrating body 13.

The vibrating body 13 is made of a conductive metal having elasticity, and has fixed portions 13b on both sides of the main body portion 13a.
A first protrusion 13c and a second protrusion 13d are integrally formed on the main body 13a of the vibrator 13 on the side of the slider 15 that is a driven member with a gap therebetween. The tips of the first protrusion 13c and the second protrusion 13d are in contact with the slider 15. The tips of the first protrusion 13c and the second protrusion 13d are formed in arc shapes having different radii. In this embodiment, the radius of the first protrusion 13c is larger than the radius of the second protrusion 13d, and the resonance frequency fL of the first protrusion 13c is greater than the resonance frequency fR of the second protrusion 13d. Has been lowered. The first protrusion 13c and the second protrusion 13d are formed to face each other and are inclined toward the outside.

  A constricted portion 13e is formed between the main body portion 13a and the fixed portion 13b of the vibrating body 13, and the constricted portion 13e reduces the influence on the vibration of the main body portion 13a. A recess 13f is formed on the side surface of the fixed portion 13b. For example, a protrusion 17 a of a conductive support member 17 made of an adjacent bronze plate having a thickness of 1 mm is fitted into the recess 13 f, and the fixing portion 13 b is fixed to the support member 17.

  The piezoelectric element 11 includes a bulk piezoelectric element 11. The piezoelectric element 11 has a rectangular parallelepiped shape, and a small diameter portion 11b and a large diameter portion 11c are formed by a step portion 11a. The tip of the small-diameter portion 11b is inserted into a recess 13h formed on the opposite side of the first protrusion 13c and the second protrusion 13d of the main body 13a of the vibrator 13, and is bonded by, for example, an epoxy resin. Yes. The resonance frequency fPZT of the piezoelectric element 11 is set to a value between the resonance frequency fL of the first protrusion 13c and the resonance frequency fR of the second protrusion 13d. An electrode 19 is formed on the bottom surface of the large diameter portion 11 c of the piezoelectric element 11. A voltage is applied between the electrode 19 and the protrusion 17 a of the support member 17.

In this embodiment, the slider 15 is guided by a linear guide using a ball fixed to a fixing member (not shown).
In the actuator described above, as shown in FIG. 3, the piezoelectric element 11 vibrates in the primary longitudinal vibration mode, and the longitudinal vibration is caused by the primary deflection vibration of the first protrusion 13c and the second protrusion 13d of the vibrating body 13. Is converted to And since the step part 11a was provided in the piezoelectric element 11, it is possible to set the primary longitudinal vibration resonance frequency of the piezoelectric element 11 low, and to obtain a larger vibration speed with the same applied voltage. The primary longitudinal vibration resonance frequency of the piezoelectric element 11 is substantially equal to the resonance frequency fPZT of the piezoelectric element 11, but the resonance frequency fL of the first protrusion 13c <resonance frequency fPZT of the piezoelectric element 11 <resonance of the second protrusion 13d. The frequency is fR. Thereby, the moving direction of the slider 15 can be switched by frequency control.

FIG. 4 shows the operating principle of the actuator described above.
Due to the difference between the resonance frequency fL of the first protrusion 13c and the resonance frequency fR of the second protrusion 13d, the longitudinal vibration and the flexural vibration between the first protrusion 13c and the second protrusion 13d are ( There is a phase difference as shown in a). As shown in (a), at the driving frequency f1 where fL <f1 <fPZT, the phase difference between the two orthogonal vibrations of the first protrusion 13c is 90 °, and as shown in (c), An elliptical locus is generated at the tip of the first protrusion 13c.

On the other hand, since the phase difference between the two vibrations is smaller than 90 ° and the bending vibration speed is small with respect to the longitudinal vibration speed, the second projecting portion 13d has a substantially linear trajectory with only longitudinal vibration. As a result, a driving force in the left direction of the figure is generated in the slider 15 by the frictional force as shown in FIG.
At the driving frequency f2 where fPZT <f2 <fR, the phase difference between the two orthogonal vibrations of the second protrusion 13d is −90 °, and as shown in FIG. Draw an elliptical trajectory in the opposite direction. On the other hand, in the first protrusion 13c, only the longitudinal vibration is almost the same as the second protrusion 13d at the drive frequency f1. Therefore, at the driving frequency f2, a driving force in the right direction in the figure is generated in the slider 15 as shown in FIG.

FIG. 5 shows the detailed shapes of the vibrating body 13 and the piezoelectric element 11 described above.
This detailed shape is sized by using finite element analysis so as to satisfy the condition of the resonance frequency fL of the first protrusion 13c <the resonance frequency fPZT of the piezoelectric element 11 <the resonance frequency fR of the second protrusion 13d. It has been decided. Here, the calculated value of the primary vibration resonance frequency of the piezoelectric element 11 is 532 kHz. The resonance frequency fL of the first protrusion 13c is 507 kHz, and the resonance frequency fR of the second protrusion 13d is 542 kHz. The dimensions of the fixed portion 13b of the vibrating body 13 were determined so that the influence on the main body portion 13a was reduced. The parameters hf, s, tf, θ, and Δr shown in FIG. 5 were analyzed with different dimensions, and the values of the parameters were determined as shown in the figure. The unit of each dimension is μm.

When an actuator was prototyped with the dimensions shown in FIG. 5 and the frequency of the admittance of the electrical terminal of the piezoelectric element 11 was measured, resonance occurred at 560 kHz. This is considered to be the primary resonance of the piezoelectric element 11. In addition, there was resonance that seems to be a secondary mode in the vicinity of 770 kHz.
FIG. 6 shows the measurement results of the vibration speed of the first protrusion 13c and the second protrusion 13d of the prototype actuator. This measurement was performed using a laser Doppler in-plane velocity vibrometer. The voltage applied to the piezoelectric element 11 was 100 Vp-p. As shown in FIG. 6, it can be seen that it vibrates greatly in the vicinity of 550 kHz, 630 kHz, and 780 kHz. In addition, it seems that the target vibration is around 550 kHz.

  As shown in FIG. 1, the measurement was performed by bringing the first protrusion 13c and the second protrusion 13d of the actuator prototyped with the dimensions shown in FIG. 5 into contact with the slider 15, as shown in FIG. The driving frequency at which the maximum speed was obtained was 522 kHz in the right direction and 508 kHz in the left direction. However, the slider 15 did not move in the vicinity of 560 kHz, 630 kHz, and 780 kHz where a large vibration speed was obtained with the vibrator alone. This is probably because the resonance frequency has shifted due to the pressurization of the slider 15.

FIGS. 7 and 8 show the thrust and efficiency of rightward movement of the prototyped actuator.
For measuring the moving speed of the slider 15, a photosensor was used, and the thrust and efficiency were calculated using the transient response measurement result. It was possible to obtain a maximum speed of 22.5 cm / s and a maximum thrust of 168 mN by moving in the right direction, and a maximum speed of 50 cm / s and a maximum thrust of 9.2 mN by moving in the left direction. 7 and 8, the arrows indicate the pressure applied by the slider 15.

  In the actuator described above, the first protrusion 13c and the second protrusion 13d that are in contact with the slider 15 and have different resonance frequencies are formed on the slider 15 side of the vibrating body 13 by inclining in the opposite direction with an interval between them. Since the resonance frequency fPZT of the piezoelectric element 11 is set to a value between the resonance frequency fL of the first protrusion 13c and the resonance frequency fR of the second protrusion 13d, the traveling direction is switched by a frequency change due to single-phase excitation. Can do.

In addition, since the sizes of the first protrusion 13c and the second protrusion 13d are made different, the resonance frequency fL of the first protrusion 13c and the resonance frequency fR of the second protrusion 13d are made different. The resonance frequency can be easily and reliably made different.
And since the 1st projection part 13c and the 2nd projection part 13d were formed inclining toward the outer side, the contact state to the slider 15 can be made stable.

Further, in the above-described actuator, since the tips of the first protrusion 13c and the second protrusion 13d are formed in an arc shape, even when the first protrusion 13c and the second protrusion 13d are deformed, The contact state with the slider 15 can be kept constant.
And in the actuator mentioned above, since the narrow part 13e was formed between the main-body part 13a of the vibrating body 13, and the fixing | fixed part 13b, the influence on the vibration of the main-body part 13a produced by fixing the fixing | fixed part 13b is reduced. be able to.

Further, since the vibrating body 13 and the support member 17 are formed of conductive members, the actuator can be operated by applying a voltage between the piezoelectric element 11 and the support member 17.
Since the bulk piezoelectric element 11 is used without using a piezoelectric thin film for the piezoelectric element 11, the applied voltage can be increased, thereby increasing the output of the actuator.

Furthermore, in the actuator described above, since the piezoelectric element 11 has a stepped shape with a small cross-sectional area on the vibrating body 13 side, the primary longitudinal vibration resonance frequency can be set low, and a larger vibration speed can be obtained with the same applied voltage. Can be obtained.
In the above-described embodiment, the resonance frequency fL of the first protrusion 13c and the resonance frequency fR of the second protrusion 13d are different from each other in the size of the first protrusion 13c and the second protrusion 13d. However, the present invention is not limited to such an embodiment. For example, the resonance frequency can be set by changing the materials of the first protrusion and the second protrusion. You may make it differ.

In the above-described embodiment, the example in which the first protrusion 13c and the second protrusion 13d are formed to be inclined toward the outside has been described. However, the present invention is limited to such an embodiment. Instead, the first protrusion and the second protrusion may be formed to be inclined inward.
Further, in the above-described embodiment, the example in which the bulk piezoelectric element 11 is used as the piezoelectric element 11 has been described. However, the present invention is not limited to such an embodiment, and for example, a piezoelectric thin film may be used.

In the above-described embodiment, the example in which the small diameter portion 11b of the piezoelectric element 11 is connected at right angles to the large diameter portion 11c has been described. For example, as illustrated in FIG. Is connected to the large diameter portion 11c by an arc r, stress concentration can be prevented and the life of the piezoelectric element 11 can be increased.
In the above-described embodiment, an example in which the present invention is applied to a micro ultrasonic linear motor has been described. However, the present invention is not limited to such an embodiment, and can be widely applied to actuators using piezoelectric elements. Can do.

  FIG. 10 shows an example in which the present invention is applied to a rotary motor, and the first protrusion 13c and the second protrusion 13d are pressed against a rotating body 21 such as a disc, a cylinder, or a ball. The rotating body 21 can be rotated clockwise and counterclockwise.

It is a front view which shows one Embodiment of the actuator of this invention. It is a side view of FIG. It is explanatory drawing which shows the primary longitudinal vibration mode and bending vibration of the actuator of FIG. It is explanatory drawing which shows the operation principle of the actuator of FIG. It is explanatory drawing which shows the detailed dimension of the actuator of FIG. It is explanatory drawing which shows the vibration speed of the 1st protrusion part of the actuator of FIG. 5, and a 2nd protrusion part. It is explanatory drawing which shows the thrust of the actuator of FIG. It is explanatory drawing which shows the efficiency of the actuator of FIG. It is explanatory drawing which shows the other example of a piezoelectric element. It is explanatory drawing which shows the example which applied this invention to the rotary motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Piezoelectric element 11a Step part 11b Small diameter part 11c Large diameter part 13 Vibration body 13a Main body part 13b Fixing part 13c 1st projection part 13d 2nd projection part 13e Constriction part 15 Slider 17 Support member 19 Electrode

Claims (9)

In the actuator that vibrates the vibrating body by the vibration of the piezoelectric element and drives the driven member by the vibration of the vibrating body,
On the driven member side of the vibrating body, a first protrusion and a second protrusion that are in contact with the driven member and have different resonance frequencies are formed to be inclined in opposite directions with an interval therebetween, and An actuator characterized in that the resonance frequency of the piezoelectric element is set to a value between the resonance frequency of the first protrusion and the resonance frequency of the second protrusion. The actuator according to claim 1, wherein
The resonance frequency of the first protrusion and the resonance frequency of the second protrusion are made different by making the sizes of the first protrusion and the second protrusion different. Actuator. The actuator according to claim 1 or 2,
An actuator, wherein the first protrusion and the second protrusion are formed to be inclined outward. The actuator according to any one of claims 1 to 3,
The actuator is characterized in that tips of the first protrusion and the second protrusion are formed in an arc shape. The actuator according to any one of claims 1 to 4,
The vibrator has fixing portions on both sides of a main body portion on which the first protrusion portion and the second protrusion portion are formed, and a constriction portion is formed between the main body portion and the fixing portion. An actuator characterized by that. The actuator according to any one of claims 1 to 5,
The vibrating body is made of a conductive metal and has fixing portions on both sides of the main body portion where the first and second protrusions are formed, and the fixing portions are fixed to a conductive support member. An actuator characterized by being made. The actuator according to any one of claims 1 to 6,
The actuator, wherein the piezoelectric element is a bulk piezoelectric element. The actuator according to claim 7, wherein
The actuator, wherein the piezoelectric element has a step shape with a small cross-sectional area on the vibrating body side. The actuator according to any one of claims 1 to 8,
The actuator is a micro ultrasonic linear motor, and the driven member is a slider that is linearly driven.

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