JP3295192B2 - Ultrasonic motor - Google Patents

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 generates elastic vibration by a piezoelectric material and uses the elastic vibration as a driving force.

[0002]

2. Description of the Related Art In recent years, an ultrasonic motor that excites a vibrating body made of a piezoelectric body such as a piezoelectric ceramic or the like to rotate a moving body by using the vibrating body as a driving force has attracted attention.

FIG. 8 is a cross-sectional view of a conventional disk-shaped ultrasonic motor, wherein 1 is a disk-shaped elastic body made of stainless steel or the like, 2 is a disk-shaped piezoelectric ceramic which is a piezoelectric body, Is a vibrating body formed by bonding a piezoelectric ceramic 2 to one of the disk surfaces of the elastic body 1, 4 is a support for holding the vibrating body 3, 5 is a friction material made of a wear-resistant material, Reference numeral 6 denotes a disc- shaped elastic body made of stainless steel or the like , and is also shown in FIG.
As described above, a rotating shaft is provided upright at the center of the elastic body 6.
I have. Reference numeral 7 denotes a moving body. The moving body 7 is configured by fixing the friction material 5 to one surface of the elastic body 6. Reference numeral 8 denotes a spring for bringing the moving body 7 into pressure contact with the vibrating body 3 via the friction material 5;
Reference numeral 9 denotes a bearing provided at the center of the vibrating body 3 for transmitting the rotary motion to the moving body 7 without loss, and 10 denotes a retaining ring for stopping the spring 8. Then, bearin is attached to the rotation axis of the elastic body 6.
9 and fix the spring 8 with the retaining ring 10.
Set. The spring 8 is fixed with a set amount of deflection so that a set pressure is obtained by the retaining ring 10.

FIG. 9 is an explanatory view showing an example of the electrode structure of the piezoelectric ceramic 2 used in the ultrasonic motor of FIG. In FIG. 9, E and F indicate electrode groups, and the electrode groups E and F
Consists of small electrode portions each having a length corresponding to a quarter wavelength in the circumferential direction, and the polarization directions of the electrodes adjacent to each other are opposite to the thickness direction. Then, the electrode groups E and F are shifted in the circumferential direction by an amount corresponding to a quarter wavelength.
With this design, the piezoelectric ceramic 2 excites the first-order radial and third-order circumferential elastic waves.

[0005] The electrode groups E and F of the piezoelectric body 2 of the ultrasonic motor configured as described above include:

[0006]

## EQU1 ## V ₁ = V ₀ × sin (ωt)

[0007]

V ₂ = V ₀ × cos (ωt) where V ₀ : instantaneous value of applied voltage ω: angular frequency t: time If V ₁ and V ₂ represented by Is

[0008]

Equation 3] _{ξ = ξ 0 × {cos (} ωt) × cos (kx) + sin (ωt) × sin (kx)} = ξ 0 × cos (ωt-kx) However, xi]: amplitude of bending vibration xi] ₀ : Instantaneous value of bending vibration k: Wave number (2π / λ) λ: Wavelength x: Traveling wave of bending vibration traveling in the circumferential direction represented by the position is excited.

FIG. 10 is an explanatory view showing a state in which the moving body 7 is driven by a traveling wave excited on the vibrating body 3 via frictional force and moves. Due to the excitation of the traveling wave of the bending vibration, the point A on an arbitrary surface of the vibrating body 3 makes an elliptical motion of the major axis 2w and the minor axis 2u. When the moving body 7 placed under pressure on the vibrating body 3 comes into contact with the vicinity of the vertex of the elliptical motion,
The moving body 7 moves at a speed of w × u in a direction opposite to the traveling direction of the wave.

[0010]

When the traveling wave of the bending vibration is ideal, the point A of the vibrating body 3 is in an elliptical motion in which the magnitude of the major axis is constant. However, when the traveling wave of the bending vibration has a standing wave component, the size of the major axis of the elliptical orbit drawn by the point A of the vibrating body 3 changes.
On the other hand, the force of tapping upward acts at the same time as the force to move in the circumferential direction.

The elastic traveling wave to be excited on the vibrating body of the ultrasonic motor contains a considerable amount of standing wave components. Therefore, as described above, the elastic wave traveling along with the original driving force for moving the moving body 7 The unnecessary force of tapping also acts. This upward tapping force is particularly large when moving the moving body 7 at high speed, and has a problem that the driving efficiency is reduced and the movement of the moving body 7 becomes unstable.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide an ultrasonic motor having both low speed characteristics and high speed characteristics, and having high driving efficiency and high operation stability.

[0013]

To achieve the above object, the present invention drives a piezoelectric body with an AC voltage to excite an elastic traveling wave to a vibrating body composed of the piezoelectric body and an elastic body. Thereby, an ultrasonic motor for rotating a moving body placed in pressure contact with the vibrating body by a pressurizing mechanism, wherein the rotating shaft erected at the center of rotation of the moving body,
A vibrating body, the pressing mechanism, and a fixed member for fixing the pressing mechanism.
A fixed member, between the vibrating body and the fixed member,
The moving body is projected by the standing wave generated on the vibrating body.
It is characterized in that a shock-absorbing part is provided for absorbing the vibrations to be lifted .

Further, according to the present invention, the buffer portion may be made of felt,
Rubber elastic, at least plastic material with fiber
It is characterized by being constituted by a cushioning material including a gap .

Further, according to the present invention, the buffer portion may be made of felt,
Rubber elastic, at least plastic material with fiber
A cushioning material including a slipper and a pair of cushions for holding the cushioning material
And an impact material holding portion .

Further, according to the present invention, the buffer section may be combined with the vibrating body.
It is characterized by being interposed between the pressurizing mechanism .

Further, according to the present invention, the buffer section may include the pressure mechanism.
It is characterized by being provided within .

[0018]

According to the present invention, a standing wave generated on a vibrating body is
The moving body absorbs the vibration that is pushed up, and
By reducing transmission loss to moving objects, ultrasonic
It can stabilize motor operation and improve efficiency.
Wear.

Further , according to the present invention, it is generated on the vibrating body.
Energy generated by the vibration of a moving object being pushed up by a standing wave
Ghee, felt, rubber elastic, plastic with fiber
Use the internal friction of the cushioning material containing at least one of the materials
To convert it to heat energy and release it to the outside.
Can effectively absorb and attenuate unwanted vibrations.
You.

Further , according to the present invention, the cushioning member holding portion
By holding the cushioning material, the pressure spring contacts the cushioning material
Always use the effect of the entire cushioning material, not just the part
And unnecessary vibrations can be suppressed more efficiently.

According to the present invention, the vibration is generated at the center of the vibrating body.
Ideal vibration for vibrating body by suppressing slight unnecessary vibration generated
Realizes a structure that excites
Vibrating body due to higher efficiency or unnecessary vibration in the center
The noise caused by contact between the shaft and bearings
This stabilizes the operation of the ultrasonic motor, improves
Moderation can be achieved. Further, according to the present invention, the vibration
Suppresses unnecessary vibration generated at the center of moving body
To realize a structure that excites the ideal vibration
For improving output extraction efficiency and for vertical vibration of moving objects
It is caused by unnecessary vibration that occurs in the pressure spring part due to
It is possible to suppress noise from the spring part,
Achieves stable operation, improved efficiency, and quietness of motor operation
be able to.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

Hereinafter, the same members as those in the prior art shown in FIGS. 8 to 10 are denoted by the same reference numerals, and detailed description is omitted.

As described in the section of the problem to be solved by the invention, in FIG. 8, when the traveling wave of the bending vibration is ideal, any point on the vibrating body 3 has a constant major axis. However, when the traveling wave of this bending vibration has a standing wave component, the point on the vibrating body 3 changes in the size of the long axis. At the same time, a force for hitting the moving body 7 upward also acts. This upward tapping force is particularly large when the moving body 7 is moved at a high speed, so that the driving efficiency is reduced and the movement of the moving body 7 becomes unstable.

Therefore, in the first embodiment of the present invention, by using the disc spring 8 having a spring constant of 1.5 kgf / mm or more, the reaction force of the upward tapping force f generates f ', and the moving body 7 The amplitude value of the vertical vibration was reduced. According to an experiment, when a disc spring having a spring constant of 1.5 kgf / mm or less was used, the vertical vibration of the moving body 7 increased, the driving efficiency decreased, and the movement of the moving body 7 became unstable. The spring constant is
When a disc spring 8 of 1.5 kgf / mm or more was used, an ultrasonic motor having high driving efficiency and stable operation was realized. In FIG. 8, two disc springs are stacked, but one or two or more disc springs can be stacked.

FIG. 1 is a characteristic diagram of the pressurizing disc spring according to the first embodiment of the present invention. The spring constant shows the characteristic curve of FIG.

According to the first embodiment configured as described above, it is possible to provide an ultrasonic motor having a stable motor characteristic and a wide speed range from low speed to high speed. Although a disc spring is used here as the pressurizing spring, the same effect can be obtained by using a coil spring or a leaf spring.

FIG. 2 is a sectional view showing the structure of an ultrasonic motor according to a second embodiment of the present invention. In FIG. 2, reference numeral 11 denotes a cushioning material made of felt, a rubber elastic body, a plastic material containing fibers, and the like. The cushioning material 11 is provided between the support 4 and the disc spring 8. The disc spring 8 has a spring constant of 1.5 kgf / mm or more as in the first embodiment.

In the second embodiment, as in the first embodiment, a force f hitting the moving body 7 upward is generated, and when the moving body 7 is moved at a high speed, the driving efficiency is reduced and the moving body 7 is not moved. Causes movement instability. Therefore, the spring constant is 1.5kgf
By using the disc spring 8 of not less than / mm, a drag force f 'of the upward tapping force f is generated, thereby reducing the amplitude value of the vertical vibration of the moving body 7 and reducing the vertical vibration. By this, the transmission efficiency of the elliptical motion can be improved and the motion of the moving body 7 can be stabilized. In addition, in the disc spring 8 shown in FIG. 2, two set of disc springs having the same characteristics are stacked to increase the set deflection so that the pressing force can be easily set. It is also possible to stack disc springs.

According to the second embodiment thus constructed, it is possible to provide an ultrasonic motor having a stable motor characteristic and a wide speed range from low speed to high speed. Although a disc spring is used here as the pressurizing spring, the same effect can be obtained by using a coil spring or a leaf spring.

FIGS. 3 and 4 are sectional views showing a modification of the second embodiment. In the modification shown in FIG.
A modified example shown in FIG. 4 in which the position of the cushioning material 11 is changed between a pair of pressurizing disc springs 8 is shown.
And between the retaining ring 10. Even with such a configuration, the same effect as that of the second embodiment can be obtained.

FIG. 5 is a sectional view of an ultrasonic motor according to a third embodiment of the present invention. In FIG. 5, reference numeral 12 denotes a cushioning material holding unit that is provided on both sides of the cushioning material 11 and holds the cushioning material 11.
Reference numeral 13 denotes a buffer unit composed of a buffer 11 and a buffer holder 12. Further, the disc spring 8 is 1.5 kgf /
It has a spring constant of not less than mm.

In the third embodiment, a cushioning material holding portion 12 is added to the cushioning material 11 according to the second embodiment shown in FIG. 2, and the cushioning material 11 is provided between a pair of cushioning material holding portions 12. Things. The pressure applied to the cushioning material 11 is evenly distributed by the cushioning material holding unit 12. As a result, the maximum pressure acting on the cushioning material 11 is reduced, the internal damping rate is improved, and the vibration damping effect is improved.

According to the third embodiment thus constructed, it is possible to provide an ultrasonic motor having a stable motor characteristic and a wide speed range from low speed to high speed.

Although a disc spring is used here as the pressurizing spring, the same effect can be obtained by using a coil spring or a leaf spring.

FIGS. 6 and 7 are cross-sectional views showing a modification of the third embodiment. In the modification shown in FIG.
A modified example shown in FIG. 7 in which the position of the buffer 13 is changed to a set of the pressurized disc springs 8
And between the retaining ring 10. Even with such a configuration, the same effect as that of the third embodiment can be obtained.

[0037]

According to the present invention configured as described above, the following effects can be obtained.

According to the first aspect of the present invention, the shock absorber is provided with a vibration.
The moving object is pushed up by the standing wave generated on the moving object
Vibration from the vibrating body to the moving body by absorbing
Loss is reduced, and the operation and efficiency of the ultrasonic motor are stabilized.
Can be improved.

According to the second aspect of the present invention, on the vibrating body,
The vibration of the moving body being pushed up by the generated standing wave
Uses felt, rubber elastic, fiber-filled
Of the cushioning material containing at least one of the plastic materials
Converts to thermal energy using partial friction and releases it to the outside
By absorbing unnecessary vibration more effectively
be able to.

According to the third aspect of the present invention, the cushioning material is retained.
By holding the cushioning material by the part, the pressure spring and the cushioning
The effect of the cushioning material as a whole, not just
And unnecessary vibration can be suppressed more efficiently.
it can.

According to the fourth and fifth aspects, the ultrasonic wave
Stabilizes motor operation, improves efficiency, and reduces noise
be able to.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a pressurized disc spring according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a modification of the second embodiment of the present invention.

FIG. 4 is a sectional view showing a modification of the second embodiment of the present invention.

FIG. 5 is a sectional view of an ultrasonic motor according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a modification of the third embodiment of the present invention.

FIG. 7 is a sectional view showing a modification of the third embodiment of the present invention.

FIG. 8 is a cross-sectional view of a conventional disk-type ultrasonic motor.

9 is an explanatory diagram showing an example of an electrode structure of a piezoelectric ceramic used in the ultrasonic motor of FIG.

FIG. 10 is an explanatory view showing a state in which a moving body is driven by frictional force by a traveling wave excited on a vibrating body and moves.

[Explanation of symbols]

1: Elastic body, 2: Piezoelectric ceramic, 3: Vibration body,
4 support, 5 friction material, 6 elastic body, 7 moving body, 8 disc spring, 9 bearing, 10 retaining ring,
11 ... cushioning material, 12 ... cushioning material holding part, 13 ... cushioning part.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masanori Sumihara 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Takahiro Nishikura 1006 Odaka Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In-house (72) Inventor Takashi Nojima 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Tetsuro Odo 1006 Odaka Kadoma, Kadoma City, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-230773 (JP, A) JP-A-63-140674 (JP, A) JP-A-3-74183 (JP, A) JP-A-2-49390 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) H02N 2/00

Claims (5)

(57) [Claims] 1. A piezoelectric body is driven by an AC voltage to excite a vibrating body composed of the piezoelectric body and an elastic body with an elastic traveling wave, whereby the vibrating body is brought into pressure contact with a vibrating body by a pressurizing mechanism. An ultrasonic motor for rotating a moving body mounted on the rotating body, wherein the vibrating body is mounted on a rotating shaft erected at the center of rotation of the moving body.
, The pressing mechanism, and a fixing member for fixing the pressing mechanism
Is provided between the vibrating body and the fixing member.
The moving body is pushed up by the standing wave generated on the moving body
An ultrasonic motor comprising a shock absorber for absorbing vibrations generated. 2. The cushioning part comprises a felt, a rubber elastic body,
Contains at least one of fibrous plastic materials
2. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is made of a cushioning material . 3. The cushioning part comprises a felt, a rubber elastic body,
Contains at least one of fibrous plastic materials
A cushioning material, and a pair of cushioning material holding portions for holding the cushioning material.
The ultrasonic motor according to claim 1, wherein the ultrasonic motor comprises: 4. A method according to claim 1, wherein said shock-absorbing section includes said vibrating body and said pressing mechanism.
4. The method according to claim 2, wherein
An ultrasonic motor as described. 5. The ultrasonic motor according to claim 2, wherein the buffer is provided in the pressurizing mechanism .