JP2000228886A - Supersonic motor and piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor capable of obtaining high output, even if the drive voltage of the ultrasonic motor is lowered, and to attain high drive efficiency. SOLUTION: A piezoelectric element 2 constituting a vibrator 3 of an ultrasonic motor is formed into a layered structure, where a piezoelectric material and a conductive body are layered in the thickness direction. The vibration of displacement obtained by adding the displacement generated at respective piezoelectric material layers can be given to the piezoelectric body 2. As a result, since large displacements can be obtained with low applied voltage, the drive efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor driven by elastic vibration excited by a piezoelectric body and a vibrator which can be suitably used for notifying the operating state of equipment by vibration.

[0002]

2. Description of the Related Art A conventional ultrasonic motor will be described below with reference to the drawings.

[0003] Among the ultrasonic motors, those in which the excited elastic wave for driving the moving body of the ultrasonic motor is a standing wave are disclosed in Japanese Patent Application Laid-Open No. 63-69472. ing.

[0004] As described in the above-mentioned conventional example, the moving body that is brought into pressure contact with the vibrating body receives the friction of the contacting portion between the protruding section and the moving body via the protruding section provided on the vibrating body. The vibrating body is driven by the elastic standing wave excited by the force.

FIG. 10 is a view showing an example of an ultrasonic motor, FIG. 10 (a) is a perspective view of the ultrasonic motor, and FIG. 10 (b) is a circumferential development of a vibrating body of the ultrasonic motor. FIG. 4 shows a cross-sectional view and a positional relationship between a standing wave excited in a vibrating body and a protrusion. FIG. 11 shows the operation of the projection when the projection is installed on the neutral surface of the vibrating body.

In FIGS. 10 and 11, reference numeral 21 denotes an elastic body;
21a is a protrusion provided on the elastic body 21, 22P is a piezoelectric layer made of a piezoelectric material, 22a is an electrode for applying a voltage to the piezoelectric layer 22P in the thickness direction, and 22 is a piezoelectric layer 22P and an electrode 22a. The piezoelectric body 23 is a vibrating body composed of the elastic body 21 including the protrusion 21a and the piezoelectric body 22, and the moving body 24 is provided on the protrusion 21a.

When a standing wave having a wavelength of λ and a wave number of n is excited in the vibrating body 23, the position of the node is iλ / 2 (i is from 0 to 2n).
And the position of the abdomen is (2j-1) λ / 4 (j is an integer from 1 to 2n).

At this time, if the protrusion 21a is provided on the abdomen of the standing wave, the displacement in the vertical direction becomes maximum as shown in FIG. 11A, but the displacement in the horizontal direction is generated only by the displacement in the vertical direction. Absent. Therefore, the protrusion 21a installed at this position does not displace in the lateral direction only by moving the contacting moving body 24 in the vertical direction.

When a projection 21a is provided at the node, FIG.
As shown in FIG. 1B, the displacement in the horizontal direction is maximum, but no displacement in the vertical direction occurs. For this reason, the protrusion 21a installed at this position cannot move the moving body 24 constantly but only by moving the contacting moving body 24 right and left around the neutral surface.

Therefore, the projection 21 is provided on the neutral surface of the vibrating body 23.
In the case where a is provided, in order to constantly rotate the moving body 24 in a fixed direction, as shown in FIG.
3 between the node and the abdomen of the standing wave having the wavelength λ and the wave number n to be excited in (3), and (2q−1) λ which is the center of the node and the abdomen
/ 8 (q is an integer from 1 to 4n).
a may be set. FIG. 10B shows the positional relationship between the displacement of the standing wave when the wave number n of the standing wave to be excited in the vibrating body 23 is 3 and the protrusion 21 a provided on the vibrating body 23.

Next, regarding a vibrator, an electromagnetic motor is widely used to realize a function of notifying a user of an operation state of a device such as an incoming call of a cellular phone or the like by vibrations. Causes the entire device or a part of the device to vibrate.

FIG. 12 is a schematic diagram of a vibrator using an electromagnetic motor. As shown in FIG.
By installing the eccentric weight 102 with the rotational symmetry broken on one axis, the electromagnetic motor itself is vibrated by the centrifugal force of the eccentric weight 102, and further, the device on which the electromagnetic motor is installed is vibrated.

[0013]

If an AC voltage having a frequency near the resonance frequency of the flexural vibration of the vibrating body of the ultrasonic motor is applied, distortion is generated by the piezoelectric body constituting the vibrating body, and the vibrating body undergoes flexural vibration. Is excited.

Therefore, the impedance is determined by the shape and material of the vibrator. For example, for vibrators with different diameters,
When voltages near the respective resonance frequencies are applied with the same amplitude, the amplitude of the flexural vibration excited by the vibrating body becomes smaller in the vibrating body having a smaller diameter. Therefore, in order to obtain the same amplitude, it is necessary to increase the voltage applied to the ultrasonic motor of the vibrating body having a smaller diameter. In addition, the impedance of the vibrating body changes depending on the pressure of the moving body, the ratio of output transmission between the protrusion provided on the vibrating body and the moving body, and the like. Therefore, in order to obtain a stable output, there is a problem that the amplitude must be set to be relatively large and the voltage applied to the ultrasonic motor must be increased.

Further, when an ultrasonic motor is incorporated in a system in which the power supply voltage must be set low, there is a problem that a booster circuit must be provided in a drive circuit of the ultrasonic motor.

An object of the present invention is to solve the above problems and to provide an ultrasonic motor capable of improving driving efficiency by lowering a voltage applied to the ultrasonic motor. Another object of the present invention is to provide an ultrasonic motor which can be operated by a simple drive circuit having no booster circuit.

Further, regarding a vibrator using an electromagnetic motor, in order to increase the vibration of the device by the vibrator, the rotational kinetic energy of the electromagnetic motor is increased by increasing the weight of the eccentric weight or increasing the rotation speed of the eccentric weight. Should be increased.

However, as the weight, size, and operation time of a device such as a mobile phone using the vibrator are reduced, the weight, size, and power consumption of the vibrator itself are demanded. Therefore, for example, by increasing or increasing the eccentric weight, the rotational kinetic energy of the electromagnetic motor can be increased. However, if the eccentric weight is increased, the weight can be reduced. In order to rotate, power consumption must be increased. Further, if the volume of the core is increased or the number of windings wound around the core is increased in order to increase the magnetic flux density in the electromagnetic motor, there is a problem that it is difficult to reduce the weight and size of the electromagnetic motor. .

The present invention solves the above-mentioned problems by using a piezoelectric vibrator, and realizes a piezoelectric vibrator having a high driving efficiency by stably operating at a low driving voltage even if the size and weight are reduced. Aim.

[0020]

Means for Solving the Problems To achieve the above object, the present invention has the following constitution.

That is, the ultrasonic motor of the present invention drives the piezoelectric body with an AC voltage to excite an elastic wave of bending vibration to a vibrating body composed of the piezoelectric body and the elastic body.
An ultrasonic motor for moving a moving body installed in contact with a protrusion on the vibrating body, wherein the piezoelectric body has a laminated structure in which a piezoelectric material and a conductive body are laminated in a thickness direction. It is characterized by the following. According to the above configuration, the piezoelectric body has a configuration in which the piezoelectric material and the conductor are laminated in a layered manner in the thickness direction, so that a large displacement can be obtained at a low driving voltage. A sonic motor can be obtained.

Further, the piezoelectric vibrator of the present invention drives a piezoelectric body with an AC voltage to excite an elastic wave of bending vibration to a disk-shaped or ring-shaped vibrating body composed of the piezoelectric body and the elastic body. A piezoelectric vibrator that generates vibration by rotating an eccentric weight installed in contact with the protrusion on the vibrating body, wherein the piezoelectric body moves a piezoelectric material and a conductor in a thickness direction. It has a laminated structure in which layers are stacked. According to the above configuration, since the piezoelectric body has a configuration in which the piezoelectric material and the conductor are stacked in layers in the thickness direction, the eccentric weight can be rotated with a low driving voltage even if the size and weight are reduced. . As a result, a piezoelectric vibrator having good driving efficiency can be obtained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a perspective view showing a schematic appearance of an ultrasonic motor according to Embodiment 1 of the present invention. FIGS. 2A and 2B are diagrams showing a schematic configuration of a vibrating body of the ultrasonic motor according to Embodiment 1 of the present invention, wherein FIG. 2A is a plan view, and FIG. A schematic cross-sectional view in which the cross-section at the circle Y is developed clockwise starting from the point X;
FIG. 4 is a diagram showing a displacement distribution diagram of a standing elastic wave excited in a vibrating body in a circumferential direction. FIG. 3 is a diagram showing an example of a piezoelectric body constituting a vibrating body of the ultrasonic motor according to Embodiment 1 of the present invention;
(A) is a plan view, (b) is a cross-sectional view of the line (a) taken along the line II, and (c) is a bottom view. FIG. 4 is an exploded perspective view showing a laminated structure of the piezoelectric body shown in FIG. FIG. 5 is an operation explanatory diagram of a vibrating body generated when a voltage is applied to the piezoelectric body of the ultrasonic motor according to Embodiment 1 of the present invention.

1 to 5, reference numeral 1 denotes an elastic body, 1a
Is a protrusion provided on the elastic body 1, 2P is a piezoelectric layer, 2P
a, 2b, 2c are electrodes for applying a voltage to the piezoelectric layer 2P in the thickness direction, and 2 is a piezoelectric layer 2P and the electrodes 2a, 2b, 2c.
Is a vibrating body composed of an elastic body 1 including a projection 1a and a piezoelectric body 2, and 4 is a moving body installed on the projection 1a.

As shown in FIGS. 1 and 2, a projection 1a is provided on one main surface of the elastic body 1, and a piezoelectric body 2 is bonded to the other main surface. As shown in FIG. 3, the piezoelectric body 2 includes three piezoelectric layers 2P1, 2P2, and 2P3 made of a piezoelectric material such as a piezoelectric ceramic, and four electrode layers made of a metal or the like. A layer in which small electrodes 2a and 2b whose center angles are equivalent to １ ／ wavelength of the wavelength of the standing wave excited in the vibrating body 3 and whose areas are almost equal are radially arranged, and a solid electrode 2c. It is composed of layers.

Further, as shown in FIG. 4, the structure of the layer composed of the small electrodes and the layer composed of the solid electrodes is such that the center angle of one main surface of the piezoelectric layer 2P1 is excited by the vibrator 3 as shown in FIG. A small electrode 2 which is equivalent to a half wavelength with respect to the wavelength of the wave and has almost the same area.
a11,2b11,2a12,2b12,2a13,2
b13 are arranged radially in this order, and an electrode 2c1 which is a solid electrode is installed between the other main surface and the piezoelectric layer 2P2. Further, the piezoelectric layer 2P2 and the piezoelectric layer 2P3
Between the center electrode and the small electrode 2 having a substantially equal area with respect to the wavelength of the standing wave excited by the vibrating body 3,
a21,2b21,2a22,2b22,2a23,2
b23 are arranged radially in this order, and the other main surface of the piezoelectric layer 2P3 is provided with an electrode 2c2 which is a solid electrode.

Small electrode 2a11 and small electrode 2a21, small electrode 2a12 and small electrode 2a22, small electrode 2a13 and small electrode 2
Reference numerals a23 are installed at substantially the same position in the thickness direction of the piezoelectric body 2, and they are all electrically connected. Further, the small electrode 2b11, the small electrode 2b21, and the small electrode 2b12
The small electrode 2b22 and the small electrode 2b13 and the small electrode 2b23 are also respectively installed at substantially the same position in the thickness direction of the piezoelectric body 2, and they are all electrically connected. Further, the solid electrodes 2c1 and 2c2 are also electrically connected. The piezoelectric layers 2P1, 2P2, and 2P3 are polarized in the thickness direction, and the polarization directions are opposite to each other in regions corresponding to adjacent small electrodes.

At this time, when a voltage is applied to the piezoelectric body 2, a vibration of displacement as shown in FIG. In FIG. 5, white arrows indicate the polarization direction of each piezoelectric layer.

As shown in FIG. 5A, the solid electrode 2c
1, 2c2 are installed on the ground, and the small electrodes 2a11, 2a2
The voltage V is applied to the small electrodes 2b11 and 2b21.
V is applied. At this time, the piezoelectric layers 2P1, 2P2, 2
In the regions corresponding to the small electrodes 2a11 and 2a21 of P3, the direction of polarization and the direction of the applied voltage are the same, so that a strain of elongation occurs in the thickness direction as indicated by the black arrow. On the other hand, the small electrodes 2 of the piezoelectric layers 2P1, 2P2, 2P3
In the regions corresponding to b11 and 2b21, the direction of polarization and the direction of the applied voltage are opposite, so that contraction distortion occurs in the thickness direction as indicated by black arrows. Since the piezoelectric body 2 is bonded to the elastic body 1, the vibrating body 3 has a structure shown in FIG.
A displacement vibration as shown in FIG. Similarly, as shown in FIG. 5B, when a voltage -V is applied to the small electrodes 2a11 and 2a21 and a voltage V is applied to the small electrodes 2b11 and 2b21, the vibration of the displacement having a phase opposite to that of FIG. Body 3
Occurs.

As described above, the piezoelectric layers 2P1, 2P2, 2P
3, a displacement corresponding to the voltage V is generated in each of the piezoelectric layers 2P1, 2P2, and 2P3. Therefore, the displacement generated by adding the displacements generated in the piezoelectric layers to the piezoelectric body 2 is added to the piezoelectric body 2. Can be excited (see FIG. 1B).

In the above description, the ultrasonic motor in which three standing waves are excited in the circumferential direction has been described. However, if the configuration of the first embodiment is used, the number of waves in the circumferential direction is particularly limited. Not something. Further, the present invention can be applied not only to the standing wave but also to the traveling wave as the elastic wave to be excited in the vibrator. Further, the rotary drive type ultrasonic motor has been described. However, it is needless to say that the linear drive type can also be implemented by forming a piezoelectric body having a laminated structure similar to that of the first embodiment.

As described above, according to the structure of the vibrating body as in the first embodiment of the present invention, a large displacement can be obtained with a low applied voltage, so that an ultrasonic motor with good driving efficiency can be realized. .

(Embodiment 2) FIG. 6 is a perspective view showing a schematic appearance of a piezoelectric vibrator according to Embodiment 2 of the present invention. FIG. 7 is a diagram showing a schematic configuration of a vibrating body of a piezoelectric vibrator according to Embodiment 2 of the present invention;
(A) is a plan view, (b) is a schematic cross-sectional view in which a cross section taken along a circle Y indicated by a dashed line in (a) is developed clockwise starting from a point X, and an elastic standing that excites the vibrating body. It is a displacement distribution figure of a wave in a peripheral direction. FIG. 8 is a view showing an example of a piezoelectric body constituting a vibrating body of a piezoelectric vibrator according to Embodiment 2 of the present invention, where (a) is a plan view and (b) is a II- of (a).
FIG. 3C is a cross-sectional view as viewed from the direction of the arrow along the line II, and FIG. FIG. 9 is an exploded perspective view showing a laminated structure of the piezoelectric body shown in FIG.

6 to 9, reference numeral 11 denotes an elastic body, 1
Reference numeral 1a denotes a protrusion provided on the elastic body 11, 12P denotes a piezoelectric layer, 12a, 12b, and 12c denote electrodes for applying a voltage to the piezoelectric layer 12P in the thickness direction, and 12 denotes the piezoelectric layer 12P and the electrodes 12a and 12b. , 12c, 13 is a vibrating body composed of the elastic body 11 including the projection 11a and the piezoelectric body 12, and 14 is an eccentric weight installed on the projection 11a.

As shown in FIGS. 6 and 7, a projection 11a is provided on one main surface of the elastic body 11, and a piezoelectric body 12 is bonded to the other main surface. Piezoelectric body 12
As shown in FIG. 8, three piezoelectric layers 12P1, 12P2, and 12P3 made of a piezoelectric material such as a piezoelectric ceramic are provided.
And four electrode layers made of metal or the like. Of these, the electrode layer is a small electrode whose center angle is equivalent to 波長 wavelength with respect to the wavelength of a standing wave to be excited in the vibrating body 13 and whose area is almost equal. 1
It is composed of a layer in which 2a and 12b are radially arranged and a layer composed of a solid electrode 12c.

Further, as shown in FIG. 9, the configuration of the layer composed of the small electrodes and the layer composed of the solid electrodes is such that the center angle of one main surface of the piezoelectric layer 12P1 is excited by the vibrator 13 as shown in FIG. The small electrodes 12a11, 12b11, 12a12, 12b12,
12a13 and 12b13 are installed radially in this order,
An electrode 12c1 which is a solid electrode is provided between the other main surface and the piezoelectric layer 12P2. Further, the piezoelectric layer 12
The central angle between P2 and the piezoelectric layer 12P3 is
The small electrodes 12a21, 12b21, 12a are equivalent to one-half the wavelength of the standing wave to be excited at 3, and have substantially the same area.
Reference numerals 22, 12b22, 12a23, and 12b23 are radially provided in this order, and an electrode 12c2, which is a solid electrode, is provided on the other main surface of the piezoelectric layer 12P3.

The small electrodes 12a11 and 12a21, the small electrodes 12a12 and 12a22, and the small electrodes 12a13
And the small electrode 12a23 are respectively installed at substantially the same position in the thickness direction of the piezoelectric body 12, and they are all electrically connected. Further, the small electrode 12b11 and the small electrode 12b2
1, small electrode 12b12 and small electrode 12b22, small electrode 12
The b13 and the small electrode 12b23 are also respectively installed at substantially the same position in the thickness direction of the piezoelectric body 12, and they are all electrically connected. Further, the solid electrodes 12c1 and 12c2 are also electrically connected. Piezoelectric layers 12P1, 12P
2, 12P3 are polarized in the thickness direction, and the polarization directions are opposite to each other in regions corresponding to adjacent small electrodes.

When a voltage is applied to each electrode of the piezoelectric vibrator thus configured in the same manner as in the first embodiment (see FIG. 5), the voltage is applied in the same manner as in the vibrator of the ultrasonic motor of the first embodiment. The displacement according to V is applied to the piezoelectric layers 12P1, 12P1
P2 and 12P3 are generated in each of the piezoelectric bodies 12
Can excite the vibration of the displacement obtained by adding the displacements generated in the respective piezoelectric layers.

As described above, according to the structure of the vibrator according to the second embodiment of the present invention, a large displacement can be obtained with a low applied voltage, so that a piezoelectric vibrator having good driving efficiency can be realized.

[0041]

As described above, according to the ultrasonic motor of the present invention, a large displacement can be obtained with a low driving voltage, so that an ultrasonic motor with good driving efficiency can be realized.

Further, according to the piezoelectric vibrator of the present invention, the eccentric weight can be rotated with a low driving voltage even if the size and weight are reduced, so that a piezoelectric vibrator with good driving efficiency can be realized.

The piezoelectric vibrator of the present invention can be used, for example, by assembling it into a device and vibrating the whole or a part of the device to notify the operating state of the device. The present invention can be suitably used for a small device, for example, used for an incoming call notification function for notifying a user of an incoming call.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic appearance of an ultrasonic motor according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a vibrating body of the ultrasonic motor according to Embodiment 1 of the present invention, where (a) is a plan view,
(B) is a schematic cross-sectional view in which the cross-section at the circle Y indicated by the dashed line (a) is developed clockwise starting from the point X, and the displacement distribution in the circumferential direction of the elastic standing wave to be excited in the vibrating body. FIG.

FIG. 3 is a diagram showing an example of a piezoelectric body constituting a vibrating body of the ultrasonic motor according to Embodiment 1 of the present invention;
(A) is a plan view, (b) is a cross-sectional view of the line (a) taken along the line II, and (c) is a bottom view.

FIG. 4 is an exploded perspective view showing a laminated structure of the piezoelectric body shown in FIG.

FIG. 5 is an operation explanatory diagram of a vibrating body generated when a voltage is applied to the piezoelectric body of the ultrasonic motor according to Embodiment 1 of the present invention.

FIG. 6 is a perspective view showing a schematic external appearance of a piezoelectric vibrator according to Embodiment 2 of the present invention.

FIGS. 7A and 7B are diagrams showing a schematic configuration of a vibrating body of a piezoelectric vibrator according to Embodiment 2 of the present invention, wherein FIG. 7A is a plan view and FIG. 7B is a circle shown by a dashed line in FIG. A schematic cross-sectional view in which the cross-section at Y is developed clockwise starting from point X;
FIG. 4 is a diagram showing a displacement distribution diagram of a standing elastic wave excited in a vibrating body in a circumferential direction.

FIG. 8 is a diagram showing an example of a piezoelectric body constituting a vibrating body of a piezoelectric vibrator according to Embodiment 2 of the present invention;
(A) is a plan view, (b) is a cross-sectional view taken along the line II-II in (a), and (c) is a bottom view.

FIG. 9 is an exploded perspective view showing a laminated structure of the piezoelectric body shown in FIG.

10A and 10B are views showing an example of a conventional ultrasonic motor, in which FIG. 10A is a schematic perspective view, FIG. 10B is a sectional view of the vibrating body developed in a circumferential direction, and FIG. It is explanatory drawing which showed an example of the positional relationship between a standing wave and a protrusion part.

FIG. 11 is an explanatory view showing an operation state of the projection when the projection is installed on a neutral surface of the vibrating body of the ultrasonic motor of FIG. 10;

FIG. 12 is a schematic perspective view showing an example of a conventional vibrator using an electromagnetic motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Elastic body 1a Protrusion part 2 Piezoelectric body 2P Piezoelectric layer 2a, 2b, 2c Electrode 3 Vibration body 4 Moving body 11 Elastic body 11a Protrusion part 12 Piezoelectric body 12P Piezoelectric layer 12a, 12b, 12c Electrode 13 Vibration body 14 Eccentric weight DESCRIPTION OF SYMBOLS 21 Elastic body 21a Projection part 22 Piezoelectric body 22P Piezoelectric layer 22a Electrode 23 Vibration body 24 Moving body 101 Electromagnetic motor 102 Eccentric weight

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Kawakita 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Norihiro Takimoto 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (Reference) DD66 DD84 DD85 DD92 DD95 FF08 FF26 FF32 FF36

Claims (3)

[Claims] 1. A piezoelectric body is driven by an AC voltage to excite an elastic wave of bending vibration to a vibrating body composed of the piezoelectric body and an elastic body so that the vibrating body comes into contact with a protrusion on the vibrating body. An ultrasonic motor for moving a moving body placed in a position, wherein the piezoelectric body has a laminated structure in which a piezoelectric material and a conductor are laminated in a layered manner in a thickness direction. 2. The ultrasonic motor according to claim 1, wherein the vibrating body has a disk shape or an annular shape, and rotates the moving body. 3. A piezoelectric body is driven by an AC voltage to excite an elastic wave of bending vibration to a disk-shaped or toroidal-shaped vibrating body composed of the piezoelectric body and an elastic body. A piezoelectric vibrator that generates vibration by rotating an eccentric weight installed in contact with the protrusion, wherein the piezoelectric body has a laminated structure in which a piezoelectric material and a conductor are laminated in a layered manner in a thickness direction. A piezoelectric vibrator comprising: