JPH09215349A - Vibrating actuator and adjustment thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to adjust a resonance frequency of each of the longitudinal vibration and the flexing vibration without causing the decline in the performance of a vibrating actuator due to the adjustment of frequencies by providing members for frequency adjustment on an end face and a side face of an elastic body in the longitudinal direction. SOLUTION: On the lower face of a base section 11a of an elastic body 11, projecting drive force extraction sections 11b, 11c for extracting drive force are formed. And, a piezoelectric element 12 is installed on the elastic body 11. Then, AC voltages which have a 90 deg. electric phase difference with each other are applied to the piezoelectric elements for driving 12a, 12b of the piezoelectric element 12 and thereby drive force due to an elliptic motion which is a composite vibration of a longitudinal vibration mode and a flexing vibration mode is caused on the drive force extraction sections 11b, 11c. Furtheremore, screw holes 11d-11g which are installation holes for members for frequency adjustment are preliminarily formed on both end faces of the elastic body 11 and then screws 13d-13g, the members for frequency adjustment, are driven into the screw holes 11d-11g. Therefore, a fine adjustment can be made to frequencies.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vibration actuator and a method for adjusting the same.

[0002]

2. Description of the Related Art Vibration actuators such as ultrasonic actuators are characterized by high torque, good controllability, high holding power and quietness, and are roughly classified into annular type and linear type. To be done. The ring type vibration actuator is
It is used in AF motors of cameras. Further, a linear vibration actuator having the following structure is known.

FIG. 9 is an explanatory view showing a conventional example of a linear vibration actuator. In a conventional linear vibration actuator, a transformer 102 for vibration is arranged on one end side of a rod-shaped elastic body 101. Further, a vibration damping transformer 103 is arranged on the other end side. Each transformer 102, 103 has a
The vibrators 102a and 103a are bonded to each other. An AC voltage is applied from the oscillator 102b to the vibrator 102a for vibration to vibrate the rod-shaped elastic body 101. Then, this vibration propagates through the rod-shaped elastic body 101 and becomes a traveling wave. The traveling wave drives the moving body 104 that is in pressure contact with the rod-shaped elastic body 101.

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.
Vibration energy is converted into electric energy by the vibrator 103a. The load 103b connected to the vibrator 103a consumes the electric energy to absorb the vibration. With this vibration damping transformer 103,
The reflection at the end face of the rod-shaped elastic body 101 is suppressed, and the standing wave of the eigenmode of the rod-shaped elastic body 101 is prevented from being generated.

However, the linear type vibration actuator shown in FIG. 9 requires the rod-shaped elastic body 101 for the entire length of the moving range of the moving body 104, and the rod-shaped elastic body 1 is required.
The whole 01 must be excited. Therefore, there is a problem that the device becomes large-sized and a vibration suppressing transformer 103 or the like is required in order to prevent the occurrence of standing waves in the eigenmode.

To solve such problems, various self-propelled vibration actuators have been proposed. For example,
"Differential degenerate vertical L1-" described in "222 Piezoelectric linear motor for moving optical pickup" in "Proceedings of the 5th Electromagnetic Force-related Dynamic Symposium"
A "bending B4 mode flat plate motor" is known.

FIG. 10 is a schematic diagram showing a conventional example of a modified degenerate vertical L1-bending B4 mode flat plate motor.
10A is a front view, FIG. 10B is a side view, and FIG.
(C) is a plan view. FIG. 11 is a perspective view of the modified degenerate vertical L1-bending B4 mode flat plate motor.

The elastic body 1 comprises a rectangular flat plate-shaped base portion 1a,
The base portion 1a is composed of driving force take-out portions 1b and 1c formed in a protruding shape on one plane. Piezoelectric elements 2 and 3 which are electromechanical conversion elements are attached to the other plane of the base portion 1a of the elastic body 1, and have longitudinal vibration L1 mode and bending vibration B4.
These are elements that generate modes and, respectively. The piezoelectric elements 4 and 5 both have mechanical energy (mechanical displacement).
Is a mechanical-electrical conversion element that converts electric energy into electric energy and detects the amount of bending that occurs in the base portion 1a.

The driving force output portions 1b and 1c are provided at the antinodes of the flexural vibration B4 mode in the elastic body 1 and are pressed against the relative motion member 6 such as a rail. This vibration actuator is designed so that the natural frequencies of the longitudinal vibration L1 mode and the bending vibration B4 mode generated in the elastic body 1 are very close to each other, and an AC voltage having a frequency close to the two natural frequencies is applied. By applying to the piezoelectric bodies 2 and 3, the longitudinal vibration L1 mode and the bending vibration B4 mode are harmonized to generate an elliptic motion in the base portion 1a. The generated elliptical motion is taken out as a thrust force with the relative motion member 6 via the driving force take-out parts 1b and 1c.

Resonant frequencies of the longitudinal vibration first-order mode and the bending vibration fourth-order mode in the base portion 1a of the elastic body 1 are as follows: longitudinal vibration: f _L1 = {1 / (2ξ)} × (E / ρ) ^{1 / 2}・ ・ ・ ・ ・ Bending vibration: f _B4 = {(λ ₄ ξ) ² τ / (2πξ ² )} × (E / 12ρ) ^1/2

Here, E: Young's modulus ρ: Density ξ: Equivalent length of elastic body 1 (length equivalent to a perfect rectangular elastic body) τ: Equivalent thickness of elastic body 1 (perfect rectangular elastic body Equivalent thickness) λ ₄ ξ = 14.137166.

As shown in the formulas and formulas, the thickness τ of the elastic body 1 affects the resonance frequency of bending vibration, but does not affect the resonance frequency of longitudinal vibration. Also, the length ξ of the elastic body 1 affects both resonance frequencies, but the longitudinal vibration:
First-order, flexural vibration: Since the order of power is different from that of second-order, the magnitude of the influence is different.

By the way, in order to obtain a highly efficient drive characteristic, the resonance frequencies of the longitudinal vibration and the bending vibration are close enough so that the difference between the two resonance frequencies is within 1% of the drive frequency. Must be a value. However, the difference between the resonance frequencies of both vibrations may be larger than the design value due to dimensional tolerances during processing. Therefore, in manufacturing the ultrasonic actuator shown in FIGS. 10 and 11, after the assembly of the elastic body 1, the resonance frequencies of both vibrations are measured, and the elastic body 1 is appropriately processed according to the measurement result, thereby It is necessary to adjust the difference between the resonance frequencies of the vibrations within a predetermined range.

[0014]

Here, as shown in the equations and equations, the shape parameters of the resonance frequency are the equivalent thickness τ of the elastic body 1 and the equivalent length ξ. Therefore, when the elastic body 1 is processed, there are two possible methods for the equivalent thickness τ and the length ξ. Further, the simplest processing means is to scrape the elastic body 1. Therefore, by cutting the elastic body 1,
There are two possible ways of reducing the equivalent thickness τ and the length ξ.

When the elastic body 1 is cut to reduce the equivalent thickness τ, only the resonance frequency of bending vibration can be changed, and its adjustment is easy. However, elastic body 1
As shown in FIGS. 10 and 11, the piezoelectric elements 2 and 3 are bonded to the plane, and it is difficult to scrape only the elastic body 1. Therefore, it is not suitable as a frequency adjusting method.

Therefore, the present applicant previously filed Japanese Patent Application No. 7-22.
No. 4909 proposed a method for adjusting a vibration actuator by cutting the elastic body 1 to reduce the equivalent length ξ. That is, when the elastic body 1 is cut to reduce the equivalent length ξ, the resonance frequencies of the longitudinal vibration and the bending vibration are increased, but the resonance frequency of the bending vibration has a larger increase rate. The difference between can be reduced.

12 (A) and 12 (B) show bending vibration (B4) by reducing the equivalent length of the elastic body 1.
12A and 12B are graphs showing an example of fluctuations in the resonance frequency and the antiresonance frequency in each of the mode) and the longitudinal vibration (L1 mode). FIG. .

In FIG. 12 (A), the resonance frequency of the longitudinal vibration (L1 mode) is larger than that of the bending vibration (B4 mode) by Δf in the stage before processing, but the elastic body 1 is cut to have an equivalent length. When ξ is reduced, as shown in FIG. 12 (B), the resonance frequency of the bending vibration (B4 mode) has a larger increase rate, and therefore the difference is Δf ′ (however, Δf ′
<Δf, and the difference between the resonance frequency of the longitudinal vibration (L1 mode) and the resonance frequency of the bending vibration (B4 mode) becomes small.

The equivalent length ξ of the elastic body is cut by cutting.
In order to reduce the difference between the two resonance frequencies by decreasing the vibration frequency, the resonance frequency of the longitudinal vibration (L1 mode) is the bending vibration (B4 mode) as shown in FIG. Must be larger than the resonance frequency of.

The equivalent length ξ is obtained by processing the elastic body 1.
For the method of reducing the noise, see the new version of the ultrasonic actuator (Sadayuki Ueba and Yoshiro Tomikawa, published by Trikeps 103).
Page) describes that for an ultrasonic actuator that uses a first-order longitudinal vibration-an eighth-order bending vibration mode, the difference in resonance frequency between both vibrations is reduced by adjusting the equivalent length ξ of the elastic body 1. ing.

As described above, when adjusting the resonance frequency of the longitudinal-flexural vibration type vibration actuator, it is common to adjust the equivalent length ξ of the elastic body by cutting the end face in the longitudinal direction of the elastic body 1. is there.

In such adjustment, in order to obtain an ideal vibration mode shape, the equivalent length ξ of the elastic body 1 must be uniform in the strict sense in the longitudinal direction. But,
Since the cross-sectional shape of the elastic body 1 of the vertical-bending type vibration actuator is a rectangle whose thickness direction is short, it is necessary to cut a relatively large area in order to cut the entire end face to adjust the equivalent length ξ. In reality, it is quite difficult to make the equivalent length ξ of the elastic body uniform by such a cutting process.

Therefore, the equivalent length ξ of the elastic body 1 is not uniform in the longitudinal direction, the shape of each vibration mode of the longitudinal vibration and the bending vibration is changed, and the driving characteristic is deteriorated.

Further, a cutting tool such as a grinder is used for cutting both end surfaces of the elastic body 1. When cutting a relatively large area, the piezoelectric material attached to one flat surface of the elastic body 1 is cut. The elements 2 and 3 are adversely affected, or the elastic body 1 is distorted by cutting, so that the driving force extracting portion 1b,
There is a problem in that the flatness of the plane (contact surface with the relative motion member 6) on which 1c is formed is reduced and the driving efficiency is reduced.

Furthermore, in order to adjust the resonance frequency by changing the equivalent length ξ of the elastic body 1, instead of cutting the entire longitudinal end face with a grinder, the elastic body 1 is used with a drill or a laser. It is also conceivable to make a hole in a part of both end faces of the. This drilling is easier and more reliable than the grinding of the entire end surface with a grinder, and it is considered that the elastic body 1 after processing is not adversely affected by processing strain or the like.

However, unless drilling is performed with high dimensional accuracy even by this means, for example, when the depth of the machined hole is larger than the target value, the resonance frequency is reversed and the bending vibration mode is generated. However, the resonance frequency becomes higher than the resonance frequency of the longitudinal vibration mode, and there is a problem that the frequency cannot be adjusted to a desired state.

[0027]

In the method for adjusting a vibration actuator according to the present invention, a mass body for frequency adjustment is added to an elastic body instead of adjusting the vibration actuator by cutting which is difficult to obtain accurate dimensional accuracy. By changing the equivalent length of the elastic body, it is possible to adjust the resonance frequency of each of the longitudinal vibration and the bending vibration without degrading the performance of the vibration actuator due to the frequency adjustment.

Specifically, a frequency adjusting member mounting hole is provided in advance on the end face in the long side direction of the rectangular plate-like elastic body,
The resonance frequency is surely adjusted by mounting the frequency adjusting member, which is a mass body having various masses, in the frequency adjusting member mounting hole while appropriately selecting the mass adjusting member.

According to a first aspect of the present invention, a rectangular flat plate-like elastic body, an electromechanical conversion element joined to one plane of the elastic body, and a relative motion of press-contacting the other plane of the elastic body. And a longitudinal vibration in a direction including a contact surface between the elastic body and the relative motion member and a bending vibration in a direction intersecting the contact surface, and the elastic body and the A vibration actuator that generates relative motion with a relative motion member, comprising a frequency adjusting member mounted on at least one of an end face and a side face in the long side direction of the elastic body. .

According to a second aspect of the present invention, a drive voltage is applied to the electromechanical conversion element joined to one plane of the rectangular plate-shaped elastic body to excite it, so that the other plane of the elastic body is pressed. Longitudinal vibration in a direction including the contact surface with the relative movement member to be contacted and bending vibration in a direction intersecting with the contact surface are generated, and the relative vibration is generated between the elastic body and the relative movement member. A method of adjusting a vibration actuator for performing a motion, comprising: attaching a frequency adjusting member to at least one of an end face and a side face in a long side direction of the elastic body, whereby the longitudinal vibration and the bending It is characterized in that the resonance frequencies of the respective vibrations are brought close to or matched with each other.

According to a third aspect of the present invention, in the method of adjusting a vibration actuator according to the second aspect, the mounting of the frequency adjusting member is performed by mounting the frequency adjusting member on an end face of the elastic body in a long side direction. It is characterized in that a hole is formed in advance and the frequency adjusting member is attached to the frequency adjusting member mounting hole.

According to a fourth aspect of the present invention, in the method for adjusting a vibration actuator according to the third aspect, after the frequency adjusting member is attached to the frequency adjusting member mounting hole, It is characterized in that mass reduction processing is performed on the portion.

In the vibration actuator adjusting method according to the present invention, the frequency adjusting member mounting hole means a hole into which the frequency adjusting member can be mounted. For example, the frequency adjusting member may be a screw or a bolt. Is a screw hole, and is a pin hole when the frequency adjusting member is a pin. By changing the length and weight of these screws, bolts or pins, and further the screwing length, finer frequency adjustment can be performed.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, an embodiment of a method for adjusting a vibration actuator according to the present invention will be described in detail with reference to the accompanying drawings. Note that the following description of the present embodiment will be given by taking an ultrasonic actuator that utilizes vibration in an ultrasonic region as an example of the vibration actuator.

FIG. 1 is a perspective view showing an actuator alone of an ultrasonic actuator used in the first embodiment of the present invention. The ultrasonic actuator 10 according to the present invention is
Elastic body 11, piezoelectric element 12 which is an electromechanical conversion element connected to one plane of elastic body 11, and driving force extracting portions 11b, 1 provided on the other plane of elastic body 11 in a protruding shape
It is composed of a relative movement member (not shown) such as a rail or a roller that comes into pressure contact with 1c.

The elastic body 11 is a rectangular plate-shaped base portion 11a.
And driving force extracting portions 11b and 11c for extracting the driving force, which are provided on the lower surface of the base portion 11a in a protruding shape. These driving force output parts 11b and 11c are
It is provided at the position of the antinode (the portion with the maximum amplitude) of the flexural vibration generated during driving. In this embodiment, the driving force output unit 1
Although the protrusions 1b and 11c are formed, the protrusions 1b and 11c may not be formed in the protrusion shape, and may be left flat like other general surfaces. Further, the driving force output parts 11b and 11c may be made of a sliding material.

The piezoelectric element 12 is an electromechanical conversion element for converting electric energy (electric signal) into mechanical displacement. In this embodiment, the driving piezoelectric elements 12a and 12b are used.
And vibration monitoring piezoelectric elements 12p and 12p '. The piezoelectric elements 12a, 12b, 12p, 12p 'are attached to the elastic body 11 by, for example, bonding.

Although not shown, the driving force output unit 1
In order to suppress the sliding resistance between the relative motion members 1b and 11c and the relative motion member (not shown), a sliding material may be attached to the relative motion member contact surfaces (bottom surfaces) of the driving force output portions 11b and 11c, respectively. Good.

The driving piezoelectric elements 12a and 12b are applied to the elastic body 11 with AC voltages having phases different from each other by 90 degrees, so that the elastic body 11 has a longitudinal vibration mode (L1 mode in this embodiment) and a bending vibration mode (L1 mode). (B4 mode in this embodiment)
To generate a driving force by the elliptic motion as a combined vibration of these two vibration modes in the driving force extracting portions 11b and 11c.

Piezoelectric elements 12p, 12p 'for vibration monitoring
Is a mechanical-electrical conversion element that converts mechanical displacement into an electric signal, and monitors the state of vibration generated in the elastic body 11 and outputs it to the control circuit 35 described later.

Although not shown, the elastic body 11 is G
Generally, it is connected to the ND potential, and the electrode (common electrode) in that case is, for example, by soldering a lead wire to the elastic body 11 or by using a metal foil with a lead wire on the elastic body 1.
It may be performed by adhering to No. 1.

Further, in the present embodiment, the both end surfaces of the elastic body 11 are arranged so as to be symmetrical with respect to the center line parallel to the long side direction (the direction of the double arrow in the figure) of the rectangular plate-shaped elastic body 11. In advance, screw holes 11d, 11 which are mounting holes for frequency adjusting members
e, 11f and 11g are provided.

In the present embodiment, the frequency adjusting member mounting holes are screw holes 11d to 11g, and the frequency adjusting member mounting holes 11d to 11g are provided with screws 13 as frequency adjusting members.
Although d, 13e, 13f, and 13g are screwed, the present invention is not limited to such an embodiment. For example, the frequency adjustment member mounting hole may be a drill hole 11
d'to 11g ', and this frequency adjustment member mounting hole 11
Pins 13d 'which are frequency adjusting members on d'to 11g'
~ 13g 'may be attached.

These screw holes 11d to 11g are formed by appropriate means (drill, laser beam irradiation, etc.) according to the frequency adjusting member to be mounted. According to the present embodiment, since it is not necessary to use a grinder to form the frequency adjustment member mounting holes 11d to 11g, it is possible to adjust the resonance frequency without adversely affecting the elastic body 11 and the piezoelectric element 12. Become.

In the ultrasonic actuator 10 of this embodiment, the resonance frequency of the longitudinal primary vibration and the resonance frequency of the bending fourth vibration are obtained by screwing the screws 13d to 13g, which are frequency adjusting members, into the screw holes 11d to 11g. And adjust. That is, by mounting the screws 13d to 13g on the elastic body 11, the equivalent length ξ of the elastic body 11 is increased by the amount of the mass increase of the screws 13d to 13g.

When the screws 13d to 13g are screwed into the screw holes 11d to 11g formed on the end face of the elastic body 11 in the longitudinal direction, the equivalent length increases from ξ to (ξ + Δξ) in the above-mentioned formulas and formulas. Here, the resonance frequencies of the longitudinal vibration and the bending vibration, which are obtained by the equations and the expressions, both decrease, but the reduction rate becomes larger for the bending vibration resonance frequency having a larger order with respect to the equivalent length ξ.

FIG. 2 is a graph showing an example of how the resonance frequencies of the flexural vibration and the longitudinal vibration change, using the relationship between the frequency of the elastic body 1 and the impedance. Shows the situation before mounting the screws 13d to 13g, and FIG. 2 (B) shows the situation after mounting.

Before mounting the screws 13d to 13g on the ultrasonic actuator 10 on which the piezoelectric element 12 has been bonded and wired (see FIG. 2A), the resonance frequency of the bending vibration mode (B4 mode) is better. It is larger than the resonance frequency of the longitudinal vibration mode (L1 mode) by Δf, but the screw 13d
By mounting ~ 13g, as shown in FIG. 2 (B), the resonance frequencies of both of them decrease, and the decrease rate of the resonance frequency of the flexural vibration mode (B4 mode) is particularly higher than that of the longitudinal vibration mode (L1 mode). It becomes larger than the reduction rate of the resonance frequency, the magnitudes of the two are reversed, and the difference changes to Δf ′ (where Δf ′ <Δf). In this way, the difference between the resonance frequencies of the longitudinal vibration mode and the bending vibration mode is adjusted to be small.

Further, in this embodiment, various kinds of screws 13d to 13g having different lengths and weights are prepared, or the screwing lengths of the screws 13d to 13g are changed to make finer adjustment. You can also

However, since the method of adjusting the ultrasonic actuator of the present embodiment has the effect of increasing the equivalent length ξ of the elastic body 11, as shown in FIG. The elastic body 11 is designed so that is higher than the resonance frequency of the longitudinal vibration.

In this embodiment, even if the elastic body 11 has a hole on the end face thereof for the purpose of frequency adjustment but the hole is too large to perform the desired frequency adjustment,
Can be applied. That is, for the one in which the resonance frequency has been reversed by drilling the end face of the elastic body,
By inserting a frequency adjusting member into this hole, it is possible to perform fine adjustment for eliminating the inversion of the resonance frequency.

FIG. 3 shows the ultrasonic actuator 10 of FIG.
3 is a block diagram showing a configuration example of a drive circuit of FIG. Oscillator 3
Reference numeral 1 is for oscillating a signal having a frequency corresponding to each of the first-order longitudinal vibration mode and the fourth-order bending vibration mode of the vibrator 10 including the elastic body 11 and the piezoelectric element 12. The output of the oscillator 31 is branched, and one output is
After being amplified by the amplifier 33, as the A phase voltage,
It is input to the electrodes of the driving piezoelectric body 12a. The other branched output is connected to the phase shifter 32. The phase shifter 32 shifts the phase of the A-phase voltage by π / 2 to obtain the B-phase voltage, and then the output is passed through the amplifier 34. , Are input to the electrodes of the driving piezoelectric element 12b.

The control circuit 35 includes the piezoelectric element 1 for vibration monitoring.
When the output voltage of 2p, 12p 'is input and the output of p, p'terminal is smaller than the preset reference voltage, the frequency is low, and the output of p, p'terminal is low. When is larger, increase the frequency,
The oscillator 31 is controlled. As a result, the vibration amplitude of the ultrasonic actuator 10 is maintained at a predetermined magnitude.

FIG. 4 shows the ultrasonic actuator 10 of FIG.
6 is an explanatory diagram of the operation of FIG. This ultrasonic actuator 10
Has an electrical phase of 9 to the driving piezoelectric elements 12a and 12b.
By applying AC voltages different by 0 degrees, a composite vibration of bending vibration and longitudinal vibration is generated, and elliptical motion is generated at the tips of the driving force extracting portions 11b and 11c of the elastic body 11. Then, the elastic body 11 is brought into pressure contact with a relative motion member (not shown) via the driving force take-out portions 11b and 11c to obtain a driving force.

In this embodiment, the driving piezoelectric body 12 is used.
The a and 12b are polarized so that the polarities thereof are in the same direction, and the applied high frequency voltages A and B have a time phase difference of π / 2, but the invention is not limited to this. The polarization of the driving piezoelectric bodies 12a and 12b may be opposite to each other.

FIG. 4A shows the time change of the two-phase high frequency voltages A and B input to the ultrasonic actuator.
It is shown from ₁ to time t ₉ . The horizontal axis of FIG. 4A indicates the effective value of the high frequency voltage. FIG. 4B shows a state of deformation of the cross section of the ultrasonic actuator, and shows a temporal change (t _{1 to} t ₉ ) of bending vibration generated in the ultrasonic actuator. FIG. 4C shows how the cross section of the ultrasonic actuator is deformed, and shows temporal changes (t _{1 to} t ₉ ) in the longitudinal vibration generated in the ultrasonic actuator. FIG. 4 (D) driving force output portion 11b of the vibration actuator, showing temporal changes of the elliptical motion generated 11c a (t ₁ ~t _9).

Next, the operation of the ultrasonic actuator 10 of this embodiment will be described for each time change (t _{1 to} t ₉ ). At time t ₁ , the high frequency voltage A generates a positive voltage and the high frequency voltage B also generates the same positive voltage as shown in FIG. 4 (A). As shown in FIG. 4 (B), the bending motions due to the high frequency voltages A and B cancel each other out,
The masses Y1 and Z1 have zero amplitude. FIG.
As shown in (C), 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 arrows. As a result, as shown in FIG. 4 (D), both of the above-mentioned vibrations are combined, and the movement of the mass points Y1 and Y2 is synthesized by the mass point Y.
And the combination of the motions of the mass points Z1 and Z2 becomes the motion of the mass point Z.

At time t ₂ , the high frequency voltage B becomes zero and the high frequency voltage A generates a positive voltage as shown in FIG. 4 (A). As shown in FIG. 4 (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. 4 (C), longitudinal vibration due to the high frequency voltage A occurs, and the mass points Y2 and Z2 contract more than at time t ₁ . As a result, FIG.
As shown in (D), the above-mentioned both vibrations are combined, and the mass point Y and the mass point Z move clockwise relative to the time t ₁ .

At time t ₃ , as shown in FIG. 4A, 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. 4 (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 t ₂ and shows the maximum positive amplitude value. Than when point Z1 is the time t ₂ is amplified in the negative direction, indicating the maximum negative amplitude values.
Further, as shown in FIG. 4C, the longitudinal vibrations due to the high frequency voltages A and B cancel each other out, and the mass point Y2 and the mass point Z2.
And return to their original positions. As a result, as shown in FIG. 4 (D), both of the above vibrations are combined and the mass point Y and the mass point Z are time t.
Move clockwise than when ₂ .

At time t ₄ , the high frequency voltage A becomes zero and the high frequency voltage B generates a negative voltage as shown in FIG. 4 (A). As shown in FIG. 4 (B), a bending motion is generated by the high frequency voltage B, the amplitude of the mass Y1 is lower than that at the time t ₃ , and the amplitude of the mass Z1 is less than that at the time t ₃ . Further, as shown in FIG. 4 (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. 4 (D), both vibrations are combined, and the mass points Y and Z move clockwise relative to the time t ₃ .

At time t ₅ , the high frequency voltage A produces a negative voltage, and the high frequency voltage B produces the same negative voltage, as shown in FIG. 4 (A). As shown in FIG. 4B, the bending movements due to the high frequency voltages A and B cancel each other out, and the masses of the mass points Y1 and Z1 become zero. Also,
As shown in FIG. 4C, the longitudinal vibrations due to the high frequency voltages A and B are generated in the contracting direction. The mass points Y2 and Z2 show the maximum contraction around the node X, as indicated by the arrows. As a result, as shown in FIG. 4 (D), both vibrations are combined, and the mass points Y and Z move clockwise relative to the time t ₄ .

As it changes from time t ₆ to time t ₉ , bending vibration and longitudinal vibration are generated in the same manner as the above-mentioned principle,
As a result, as shown in FIG. 4D, the mass points Y and Z
Moves clockwise and makes an elliptical motion.

On the basis of the above principle, the ultrasonic actuator 10 causes an elliptic motion at the tips of the driving force extracting portions 11b and 11c to generate a driving force. Therefore,
When the tips of the driving force output parts 11b and 11c are pressed against the relative motion member, relative motion is generated between the ultrasonic actuator 10 and the relative motion member.

FIG. 5 is an explanatory diagram of an algorithm for determining the length of the frequency adjusting member to be attached to the elastic body in the ultrasonic actuator adjusting method according to the present invention. First, in step 1 (hereinafter, simply referred to as “S1”), resonance frequencies of bending vibration and longitudinal vibration of the assembled ultrasonic actuator 10 are measured using an impedance analyzer.

In S2, the difference Δf between the two resonance frequencies measured in S1 is calculated. In S3, the magnitude of Δf calculated in S2 and the preset target value a are compared. If Δf ≦ a, the process proceeds to S4, and if Δf> a, the process proceeds to S5.

Since the difference Δf between the two resonance frequencies is within the predetermined range, S4 ends as it is, and the frequency adjusting members 13d to 13g are not mounted. In S5,
Using the difference Δf obtained in S2, the length Δ of the frequency adjustment member
ξ is calculated by the function Δξ = f (Δf). Here, the function f is experimentally and empirically obtained in advance.

At S6, based on Δξ obtained at S5,
The frequency adjusting members 13d to 13g are attached to the frequency adjusting member attaching holes 11d to 11g. Then, after mounting the frequency adjusting members 13d to 13g on the elastic body 11, the process returns to S1 and the resonance frequencies of the bending vibration and the longitudinal vibration of the ultrasonic actuator 10 are measured again by using the impedance analyzer, and the difference Δf is obtained in S2. 'Is calculated.
Then, in S3, when Δf> a, the length Δξ of the frequency adjusting member is performed in exactly the same manner, and when Δf ≦ a, the process ends.

Next, an example of a driving device using the ultrasonic actuator 10 of this embodiment will be described. FIG.
FIG. 6 is a diagram showing an example of the overall configuration of a driving device using the ultrasonic actuator 10 described with reference to FIGS. 1 to 5;
6A is a front view, and FIG. 6B is a cross-sectional view taken along the line AA in FIG. 6A.

An elastic body 11 to which a piezoelectric element 12 is attached,
The driving force output portions 11b, 11 provided on the elastic body 11
In the ultrasonic actuator 10 including the relative motion member 20 that contacts c, the elastic body 11 is pressed toward the relative motion member 20 by the pressing mechanism 21.

Further, the ultrasonic actuator 10 is shown in FIG.
The linear guide rail 23 supported by the groove-shaped linear guide 24 fixed to one inner surface 25a of the connecting member 25 having the groove-shaped step surface shape shown in (B) and the inner surface 25b facing this. Is installed between the outer surface 23a and the outer surface 23a.

The coil spring 2 of the pressing mechanism 21
One ends of the 1b and 21c and the guide rods 21d and 21e are fixed to the inner surface 25a of the connecting member 25, and the other ends are fixed to the pressure plate 21f that presses the elastic body 11 via the piezoelectric element 12. On the other hand, the relative movement member 20 and the linear guide rail 23 are fixed by screwing in this embodiment. Note that a leaf spring, a disc spring, or the like may be used instead of the coil spring.

When a high frequency voltage is applied to the piezoelectric body 12 to cause elliptical vibration in the elastic body 11 in the driving device thus constructed, when the connecting member 25 is fixed, that is, the ultrasonic actuator 10 moves. If not, the relative movement member 20 and the linear guide rail 23 move relative to each other as a unit.

When the relative motion member 20 is fixed, that is, when the ultrasonic actuator 10 moves, the ultrasonic actuator body, the connecting member 25 and the linear guide 24 move relative to each other as a unit.

(Second Embodiment) FIG. 7 is a perspective view showing an elastic body shape of an ultrasonic actuator used in a second embodiment of the method for adjusting an ultrasonic actuator according to the present invention. In the following description of each embodiment, only the differences from the first embodiment will be described, and the portions common to the first embodiment will be denoted by the same reference numerals and will not be described.

The ultrasonic actuator 10-1 in this embodiment has pins 13d-1, 1 as frequency adjusting members.
3e-1, 13f-1 and 13g-1 are used, and the frequency adjusting member mounting holes are correspondingly provided with pin holes 11d-1, 11
This is the point provided as e-1, 11f-1, and 11g-1.

The pins 13d-1 to 13g-1 may be fitted into or bonded to the pin holes 11d-1 to 11g-1. According to this embodiment, as in the first embodiment, the difference between the resonance frequencies of the bending vibration mode and the longitudinal vibration mode generated in the elastic body 11 can be adjusted.

(Third Embodiment) FIGS. 8A to 8C.
[Fig. 3] is a plan view showing a third embodiment of the frequency adjusting member.

As shown in FIG. 8 (A), the groove-shaped planar frequency adjusting member 14a may be attached to the base portion 11a by, for example, bonding or fitting, and as shown in FIG. 8 (B). In addition, the frequency adjusting member 14b having a dovetail groove-shaped convex portion may be fitted to the base portion 11a by fitting,
Further, as shown in FIG. 8C, a rectangular plane-shaped frequency adjusting member 14c may be bonded to the base portion 11a.

According to the first to third embodiments described in detail above, the difference between the resonance frequency of the longitudinal vibration and the resonance frequency of the bending vibration can be easily achieved without adversely affecting the elastic body, the piezoelectric element and the like. In addition, it is possible to make a reliable adjustment.

Further, even for an elastic body whose resonance frequency has been reversed due to the drilling adjustment, fine adjustment for eliminating the reverse rotation can be performed again. In this way, the method of adjusting the ultrasonic actuator according to the present invention can eliminate the performance deterioration of the ultrasonic actuator based on the processing tolerance. Therefore, when the ultrasonic actuator is mass-produced, the yield can be improved and the driving characteristics of the ultrasonic actuator can be improved.

(Modification) First Embodiment described above
The present invention is not limited to the third embodiment, and various modifications and changes are possible, which are also included in the present invention.

For example, in each of the embodiments, the piezoelectric element is used as the electromechanical conversion element, but the present invention is not limited to such an aspect, and can convert electric energy into mechanical displacement. Can be applied equally. For example, an electrostrictive element or a magnetostrictive element can be used.

Further, in the first to third embodiments,
Although the ultrasonic actuator using the longitudinal first order vibration and the bending fourth order vibration has been described, the same applies to an actuator generally using the vertical nth order vibration (n: natural number) and the bending mth order vibration (m: natural number). It is possible to adjust the resonance frequency using the method.

[Brief description of drawings]

FIG. 1 is a perspective view showing an actuator alone of a vibration actuator used in a first embodiment of the present invention.

FIG. 2 is a graph showing an example of changes in resonance frequencies of flexural vibration and longitudinal vibration using a relationship between frequency and impedance of an elastic body, and FIG. 2 (B) shows the situation after mounting.

3 is a block diagram showing a configuration example of a drive circuit of the vibration actuator of FIG.

FIG. 4 is an explanatory diagram of an operation of the vibration actuator of FIG.

FIG. 5 is an explanatory diagram of an algorithm for determining the length of the frequency adjusting member to be attached to the elastic body in the vibration actuator adjusting method according to the present invention.

6 is a diagram showing an example of the overall configuration of a drive device using the vibration actuator described with reference to FIGS.
6A is a front view, and FIG. 6B is A- in FIG.
It is A sectional drawing.

FIG. 7 is a perspective view showing an elastic body shape of a vibration actuator used in a second embodiment of the vibration actuator adjusting method according to the present invention.

8A to 8C are all plan views showing a third embodiment of a frequency adjusting member.

FIG. 9 is an explanatory diagram showing a conventional example of a linear vibration actuator.

10A and 10B are schematic views showing a conventional example of a modified degenerate vertical L1-bending B4 mode flat plate motor, in which FIG. 10A is a front view, FIG. 10B is a side view, and FIG. Is a plan view.

FIG. 11 is a perspective view of a modified degenerate vertical L1-bending B4 mode flat plate motor.

12A and 12B are resonance frequency and anti-resonance frequency of bending vibration (B4 mode) and longitudinal vibration (L1 mode), respectively, by reducing the equivalent length of the elastic body. 12 is a graph showing an example of the fluctuation of FIG.
12A shows the state before processing and FIG. 12B shows the state after processing.

[Explanation of symbols]

 10, 10-1 Vibration actuator 11 Elastic body 11a Foundation part 11b, 11c Driving force extraction part 11d-11g Screw hole (frequency adjusting member mounting hole) 12a, 12b Driving piezoelectric element 12p, 12p 'Vibration monitoring piezoelectric element 13d- 13g Screw (frequency adjusting member) 20 Relative movement member 21 Pressurizing mechanism 21b, 21c Coil spring 21d, 21e Guide rod 21f Pressing plate 23 Linear guide rail 24 Linear guide 25 Connecting member 25a, 25b Inner surface 31 Oscillator 32 Phase shifter 33, 34 amplifier 35 control circuit

Claims (4)

[Claims] 1. A rectangular flat plate-shaped elastic body, an electromechanical conversion element joined to one plane of the elastic body, and a relative motion member that is brought into pressure contact with the other plane of the elastic body,
Relative motion occurs between the elastic body and the relative motion member by causing longitudinal vibration in a direction including a contact surface between the elastic body and the relative motion member and bending vibration in a direction intersecting the contact surface. And a frequency adjusting member mounted on an end face and / or a side face of the elastic body in the long side direction. 2. Relative motion in which the electromechanical conversion element joined to one flat surface of a rectangular plate-shaped elastic body is excited by applying a driving voltage to the other flat surface of the elastic body. A vibration actuator that generates a longitudinal vibration in a direction including a contact surface with a member and a bending vibration in a direction intersecting the contact surface to perform relative motion between the elastic body and the relative motion member. An adjusting method, wherein a resonance frequency of each of the longitudinal vibration and the bending vibration is approximated or matched by mounting a frequency adjusting member on an end face and / or a side face in the long side direction of the elastic body. How to adjust the vibration actuator. 3. The vibration actuator adjusting method according to claim 2, wherein the frequency adjusting member is attached by forming a frequency adjusting member attaching hole on an end face of the elastic body in a long side direction. A method for adjusting a vibration actuator, which is performed by mounting the frequency adjusting member in the frequency adjusting member mounting hole. 4. The method for adjusting a vibration actuator according to claim 3, wherein after the frequency adjusting member is attached to the frequency adjusting member mounting hole, a mass reduction process is performed on a part of the frequency adjusting member. A method for adjusting a vibration actuator, which comprises: