JPH0681522B2 - Ultrasonic motor using ultrasonic vibration - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrasonic motor utilizing ultrasonic vibration having an elastic body and a piezoelectric body for exciting the elastic body.

(Background of the Invention) The principle of an ultrasonic motor will be described with reference to Figs. FIG. 3 shows a linear ultrasonic motor, and FIG. 4 shows a rotary ultrasonic motor. FIGS. 3 and 4 show a state in which the elastic body 1 is excited to generate a surface wave (having a wavelength λ) on the surface thereof. With the traveling direction N of this surface wave and focusing on the movement of particles near the apex A of one mountain of the surface wave, the movement draws an elliptical locus as shown in FIG. When the moving body 2 is brought into pressure contact with the portion where the surface wave 1 is generated, the moving body 2 moves on the surface of the elastic body 1 in the direction M opposite to the traveling direction N of the surface wave.

Next, a method of generating surface waves in the elastic body 1 will be described based on FIGS. 5 (a) to 5 (c). The piezoelectric body 3 is adhered to the elastic body 1 with a conductive conductive adhesive, and the central portion 3a of the piezoelectric body 3 is polarized in the direction opposite to the side portions 3b and 3c of the piezoelectric body 3 (the polarization direction is indicated by an arrow). Has been done. Electrodes are baked on the entire surfaces 3d and 3e of the piezoelectric body 3, and the surface 3e is grounded via the conductive adhesive. As shown in FIG. 5 (a), when the surface 3d of the piezoelectric body 3 is opened (no voltage is applied to the surface 3d) or dropped to the ground of the same potential as the surface 3e, the piezoelectric body 3 Since the elastic body 1 does not expand and contract, the elastic body 1 remains in the planar shape. As shown in FIG. 5 (b), when a negative voltage is applied to the surface 3d, the central portion 3a of the piezoelectric body 3 contracts in the longitudinal direction and both side portions 3b, 3c extend in the longitudinal direction due to the difference in polarization direction. At this time, since the elastic body 1 tries to maintain the length in the longitudinal direction in the state of FIG. 5A against the expansion and contraction of the piezoelectric body 3, the piezoelectric body 3 and the elastic body 1
And bend as shown in FIG. 5 (b). Moreover, when a positive voltage is applied to the surface 3d as shown in FIG.
It bends in the opposite direction to the shape shown in FIG. Therefore, when a sine wave voltage is applied to the surface 3d of the piezoelectric body 3, the elastic body 1 makes a bending motion.

The conventional rotary ultrasonic motor based on this principle and the rotary ultrasonic motor proposed by the present applicant will be described. Sixth
The conventional ultrasonic motor is shown in FIGS.
Fig. 10 shows an ultrasonic motor proposed by the applicant in Japanese Patent Application No. 59-100116. In the perspective view shown in FIG. 6, the ring-shaped piezoelectric body 30 and the ring-shaped elastic body 10 are bonded with a conductive adhesive, and the rotor (moving body) 20 is pressed against the elastic body 10 by a mechanism (not shown). . On the surface of this piezoelectric body 30, electrically independent segment electrodes 40a to 40n are fired, and electrodes 40b to 40g are electrically conductive adhesive 43, and electrodes 40i to 40n are electrically conductive conductive adhesive 44. The electrodes 40a are electrically connected to the elastic body 10 by the conductive adhesive 42 and are grounded.

The piezoelectric portions below the segment electrodes 40b to 40g and 40i to 40n are indicated by a direction T (from the back side to the front side of the paper) and a direction B (from the front side to the back side of the paper) as shown in FIG. As such, they are alternately polarized in opposite directions. The electrode 40a has a length of 3/4 of the wavelength λ of the surface wave, the electrode 40h has a length of 1/4 of the wavelength λ, and the electrodes 40b to 40g and 40i to 40n each have a wavelength of λ.
Each of them corresponds to a length of 1/2.

Then, as shown in FIG. 8, the sine wave voltage V1 is applied to the segment electrodes 40b to 40g and the segment electrodes 40i to 4g are
When a sinusoidal voltage V2 having a phase of π / 2 with respect to the voltage V1 is applied to 0n, the voltage body portion under each electrode expands and contracts, and the surface wave (traveling A bending vibration that causes a wave is generated to rotate the rotor 20. The rotation direction of this rotor 20 is the voltage with respect to the voltage V1.
It depends on whether the phase of V2 is advanced or delayed by π / 2.

Next, the ultrasonic motor proposed by the applicant of the present invention for the purpose of improving the driving efficiency will be described with reference to FIGS. 9 and 10.
Although only the front view of the ultrasonic motor is shown in FIG. 9, like the ultrasonic motor shown in FIGS. 6 and 7, the ring-shaped piezoelectric body 30 and the ring-shaped elastic body 10 are used. Is bonded with a conductive adhesive, and the rotor 20 is pressed against the elastic body 10 by a mechanism (not shown).

On the surface of the ring-shaped piezoelectric body 30, an electrode group consisting of segment electrodes 6α, 6a to 6z electrically arranged independently of each other is fired, and the segment electrode 6α is shown in FIG. Similar to the segment electrode 40a shown, it is electrically connected to the elastic body 10 by the conductive adhesive 42 and is grounded. This segment electrode 6α is 1 / the wavelength λ of the surface wave.
2 and the segment electrodes 6a to 6z each correspond to 1/4 of the wavelength λ. Two adjacent electrodes 6a
・ 6b, 6c ・ 6d, …… and 6y ・ 6z each as a unit,
Piezoelectric portions (piezoelectric units) under each unit are alternately polarized and arranged in opposite directions as indicated by directions B and T. FIG. 10 is a diagram in which FIG. 9 is linearly expanded for convenience, in which a sine wave voltage V1 is applied to every other segment electrode of the electrode group and the voltage between the electrodes to which the voltage V1 is applied. A sine wave voltage V2 having a phase difference of π / 2 with respect to the voltage V1 is applied to the segment electrodes.

As shown in FIG. 10, each segment electrode 6a, 6c, 6e, 6g, 6i, 6
At k, 6m, 6o, 6q, 6s, 6u, 6w, 6y, the sine wave voltage V1 is also applied to each segment electrode 6b, 6d, 6f, 6h, 6j, 6l, 6n, 6p, 6r, 6t, 6v, 6x, A sine wave voltage V2 is applied to 6z. In this way, when the sine wave voltages V1 and V2 are applied to each segment electrode, the voltage body portion under each electrode expands and contracts, and the surface wave (traveling wave) that propagates in one direction to the ring-shaped elastic body 10 is generated. ) Occurs, and the rotor 20 rotates. The rotating direction of the rotor 20 depends on whether the phase of the voltage V2 with respect to the voltage V1 is advanced or delayed by π / 2.

If the piezoelectric body portion under each segment electrode arranged on the piezoelectric body 30 of this ultrasonic motor or the piezoelectric body portion distinguished by the polarization direction of the piezoelectric body 30 is called an active unit portion, the active unit portion The boundary line of (1) may be indicated by the boundary between the electrodes, or it may be indicated by the boundary of the piezoelectric material parts showing different polarization directions. In the ultrasonic motor, each active unit part of the piezoelectric body vibrates ultrasonically and flexurally vibrates together with the elastic body to generate a surface wave on the surface of the elastic body. It can be seen that if the lengths 1 and 12 in the longitudinal direction of the active unit portion are set to be long, flexural vibration is likely to occur, that is, the driving efficiency of the ultrasonic motor depends on the length in the longitudinal direction of the active unit portion.

Therefore, in FIG. 8 and FIG. 10, since the lengths 1 and 12 in the longitudinal direction are not sufficiently long with respect to the width W of the active unit portion, flexural vibration of the active unit portion cannot be efficiently obtained. There was a flaw. Further, this drawback has been a major obstacle when the frequency of the surface wave is set to a high value or when the width of the piezoelectric body is widened to obtain a large torque. Also, the length of the active unit in the longitudinal direction 1, l2
To lengthen the length, lengthen the ultrasonic motor by lengthening the length 1, l2,
Although it is conceivable to shorten the two wavelengths and lengthen the lengths 1 and 12 relative to each other, however, there is a new drawback of increasing the size or controlling the wavelength λ.

(Object of the Invention) The present invention aims to improve the driving efficiency of an ultrasonic motor.

(Summary of the Invention) In order to achieve the above object, in the present invention, the boundary line between adjacent active unit portions is configured to be inclined with respect to the direction perpendicular to the traveling direction of the surface wave. The technical point is to enable highly efficient flexural vibrations without changing the above, and to improve the driving efficiency as an ultrasonic motor.

(Embodiment) FIGS. 1 and 2 show a preferred embodiment of the present invention. The ultrasonic motor of FIG. 1 is based on the ultrasonic motor described in FIGS. 6 to 8, and The ultrasonic motor shown in FIG. 2 is based on the ultrasonic motor described with reference to FIGS. 9 and 10. Therefore, regarding the ultrasonic motor of the embodiment, only the structure different from the conventional ultrasonic motor will be described. 1 (A) and 2 (A) are front views of the ultrasonic motor, and FIGS. 1 (B) and 2 (B) are segment electrodes 100a to 100n and segment electrodes for convenience of explanation. The development view in which each piezoelectric body 30 to which 101a to 101z and 101α are adhered is linearly developed is shown.

In FIG. 1, a ring-shaped piezoelectric body 30 is adhered to the elastic body 10 while electrically conducting, and the entire surface of the piezoelectric body 30 on the elastic body side is dropped to the ground. Sine wave voltage V1 is applied to 100g and electrodes 100i to 10
The fact that the sine wave voltage V2 is applied to 0n is the same as in FIG. It is also the same that the polarization directions under each electrode are alternately opposite. The difference in the configuration is that the segment electrodes 100a to 100n are spirally formed on the piezoelectric body 30, and needless to say, the polarization of the piezoelectric body 30 is also spirally formed so as to correspond to the segment electrodes, and the adjacent active electrodes are arranged. The boundary line of the unit portion is configured to be inclined with respect to the direction perpendicular to the traveling direction of the surface wave. Therefore, as shown in FIG. 1 (B), it can be seen that the length 1'in the longitudinal direction with respect to the width W of the active unit portion is longer than the length 1 in FIG. The wavelength of the surface wave of this ultrasonic motor is the same as the conventional one, but the length 1'in the longitudinal direction of the active unit portion becomes longer, so that the piezoelectric body 30 becomes easier to bend, and bending vibration of the elastic body is easier than in the past. To be done.

In FIG. 2, the ring-shaped piezoelectric body 30 is adhered to the elastic body while electrically conducting, the entire surface of the piezoelectric body on the elastic body side is dropped to the ground, and the electrode 101α is grounded by the electrodes 101a, 101c, 101e …… The sine wave voltage V1 is applied to 101y and the electrode 10
The fact that the sine wave voltage V2 is applied to 1b, 101d, 101f, ... 101z is the same as in FIG. Where the configuration is different,
Similar to the configuration shown in FIG. 1, the boundary line between adjacent active unit portions is configured to be inclined with respect to the direction perpendicular to the traveling direction of the surface wave. Therefore, as shown in FIG. 2 (B), it is understood that the length l2 'in the longitudinal direction with respect to the width W of the active unit portion is longer than the length l2 in FIG. Therefore, the bending vibration of the elastic body is easily performed in the same manner as described above.

Therefore, by tilting the boundary line of the active unit portion of the ultrasonic motor, it becomes easier to bend than the conventional piezoelectric body, so that bending vibration of the elastic body easily occurs, and the driving efficiency of the ultrasonic motor can be improved.

The present invention is not limited to the above-described embodiments, and can be appropriately modified, and may be a linear type ultrasonic motor, and the piezoelectric body has a plurality of independent piezoelectric elements arranged in a ring shape or a linear shape. It is also possible that each of the piezoelectric elements is one or a plurality of piezoelectric elements is an active unit portion. Further, in the present embodiment, the active unit portion is divided by the electrode, but it may be divided by the difference in the polarization direction of the piezoelectric body under the electrode as described above.

(Effect of the invention) As described above, according to the present invention, since the boundary line of each adjacent active unit portion is inclined with respect to the direction perpendicular to the traveling direction of the surface wave, the wavelength of the surface wave can be reduced. The effective length of the piezoelectric body in the longitudinal direction can be made long without any change, and bending vibration can be performed more easily than in the past, and as a result, an ultrasonic motor with high driving efficiency can be obtained.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention, and FIGS. 1 (A) and 2 (A) are front views of an ultrasonic motor, FIG.
Drawing (B) and Drawing 2 (B) show the development view which developed the above-mentioned each front view in the shape of a straight line. 3 to 5 are principle diagrams of the ultrasonic motor, FIG. 3 is an explanatory diagram of a linear ultrasonic motor, FIG. 4 is an explanatory diagram of a rotary ultrasonic motor, and FIG. (C) shows a state diagram of the excitation of the ultrasonic motor. FIGS. 6 to 8 show a conventional ultrasonic motor, FIGS. 9 and 10 show an ultrasonic motor proposed by the applicant, and FIG. 6 shows a perspective view of the ultrasonic motor. 7 and 9 show a front view of the ultrasonic motor, and FIGS. 8 and 10 show a developed view in which each of the front views is linearly developed. (Explanation of symbols of main parts) 1,10 ...... Elastic body 2, 20 ...... Moving body (rotor) 3, 30 ...... Piezoelectric body 40a-40n; 6α, 6a-6z; 100a-100n; 101α, 101a- 101z ...... Segment electrode

Claims (1)

[Claims] 1. An ultrasonic motor utilizing ultrasonic vibration, comprising: an elastic body; and a piezoelectric body which is composed of a plurality of active unit portions divided by electrodes or polarization directions and excites the elastic body. An ultrasonic motor using ultrasonic vibration, wherein a boundary line between the active unit portions is inclined with respect to a direction perpendicular to a traveling direction of the vibration wave.