JP2012170255A - Piezoelectric element and ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element being utilized in an ultrasonic motor that can perform driving at multi degrees of freedom, and detecting a vibration state, and having a simple configuration, and to provide an ultrasonic motor having the piezoelectric element.SOLUTION: A piezoelectric element 10 for use in an ultrasonic vibrator driving a driven body by a plurality of vibration modes excited by application of a predetermined driving signal, is configured to have vibration detection electrode layers 3 and 4 including internal electrodes 3d-1, 3d-2, 4d-1, 4d-2, 3d-1', 3d-2', 4d-1', and 4d-2' configuring a vibration detection electrode detecting a vibration component in a propulsion direction at driving of the driven body in a plurality of axial directions among vibrations in the plurality of vibration modes. The vibration detection electrode layers 3 and 4 are provided in the vicinity of an antinode in a flexural vibration mode in directions orthogonal to each other at the same frequency.

Description

  The present invention relates to a piezoelectric element and an ultrasonic motor using the piezoelectric element as an ultrasonic vibrator.

  In recent years, ultrasonic motors using vibrations of vibrators such as piezoelectric elements have attracted attention as new motors that replace electromagnetic motors. Compared with conventional electromagnetic motors, this ultrasonic motor has low speed and high thrust without gears, high holding force, long stroke and high resolution, quietness, magnetic There are advantages such as no noise and no influence of magnetic noise.

In an ultrasonic motor, an ultrasonic vibrator provided with a driving element that is a friction member is pressed against a driven member that is a relative motion member via the driving element. Then, the driven member is driven by a frictional force between the driver and the driven member.
Currently, an ultrasonic motor using a piezoelectric element that can be driven with multiple degrees of freedom has been developed as one of ultrasonic motors with higher added value. And as a technique relevant to such an ultrasonic motor, the following techniques are disclosed by patent document 1, for example.

That is, Patent Document 1 discloses an ultrasonic motor that can be driven with multiple degrees of freedom by a single piezoelectric element. In the ultrasonic motor disclosed in Patent Document 1, a columnar piezoelectric element having a plurality of active regions is used as a vibrating body.
The piezoelectric element disclosed in Patent Document 1 includes two substantially rectangular parallelepiped laminated portions (first laminated portion and second laminated portion) in which piezoelectric sheets are laminated. External electrodes are disposed on the side surfaces of the first stacked portion and the second stacked portion, respectively.

  By the way, in the piezoelectric element disclosed in Patent Document 1, the piezoelectric active region corresponds to the position of two internal electrodes formed in such a manner that the main plane of each piezoelectric sheet is divided into two. Specifically, the piezoelectric active region in the first stacked unit, the piezoelectric active region in the second stacked unit, and the boundary active sheet that forms the boundary between the first stacked unit and the second stacked unit, However, internal electrodes are formed on each piezoelectric sheet so that they are in a positional relationship of 90 degrees rotated (90 degrees horizontally with respect to the boundary sheet).

  By configuring as described above and inputting predetermined alternating signals to each piezoelectric active region, longitudinal primary vibration and bending secondary vibration are excited in the piezoelectric element. As a result, a driving force in two directions (a driving force in the X direction component and a driving force in the Y direction component) is generated. Then, by using the driving force, the spherical driven body held so as to be in pressure contact with the end face in the longitudinal direction of the piezoelectric element can be moved in two directions (XY directions).

Japanese Patent Laid-Open No. 2004-282841

By the way, at present, even when the vibration state of the ultrasonic motor changes due to external factors (for example, load fluctuation or temperature fluctuation), the ultrasonic motor capable of performing correction to stabilize the driving of the ultrasonic motor. Is desired.
However, the piezoelectric element disclosed in Patent Document 1 is not provided with means for detecting a change in resonance frequency caused by an external factor. Therefore, according to the technique disclosed in Patent Document 1, unless a special detection means is provided, when the vibration state of the piezoelectric element changes due to the external factors as described above, the motor of the ultrasonic motor is concerned. Corrections that stabilize the characteristics cannot be performed. In addition, providing a special detection means separately leads to the complication and enlargement of the structure of the ultrasonic motor.

  The present invention has been made in view of the above circumstances, and is a piezoelectric element used in an ultrasonic motor that can be driven with multiple degrees of freedom, and can detect a vibration state and has a simple configuration. And an ultrasonic motor including the piezoelectric element.

In order to achieve the above object, a piezoelectric element according to the first aspect of the present invention comprises:
A piezoelectric element used in an ultrasonic transducer that drives a driven body by a plurality of vibration modes excited by applying a predetermined drive signal,
Among vibrations in the plurality of vibration modes, comprising a vibration detection electrode layer including a vibration detection electrode for detecting a vibration component in a propulsion direction when driving the driven body in a plurality of axial directions,
The vibration detection electrode layer is provided in the vicinity of the abdomen in a plurality of bending vibration modes in the direction orthogonal to each other at the same frequency.

In order to achieve the above object, an ultrasonic motor according to the second aspect of the present invention comprises:
A driven body having a substantially spherical shape;
A piezoelectric element that drives the driven body in multiple degrees of freedom by a plurality of vibration modes excited by applying a predetermined driving signal;
A friction contact provided on a surface of the piezoelectric element facing the driven body;
A pressing member that applies a pressing force to the piezoelectric element and press-contacts the piezoelectric element to the driven body via the friction contact;
A support member for rotatably supporting the driven body around a plurality of axes;
A controller for driving the piezoelectric element by outputting a two-phase alternating signal as the driving signal and detecting a vibration state of the piezoelectric element;
Comprising
The piezoelectric element includes a vibration detection electrode layer including a vibration detection electrode that detects a vibration component in a propulsion direction when driving the driven body in a plurality of axial directions among vibrations in the plurality of vibration modes.
The vibration detection electrode is provided in the vicinity of the abdomen in a plurality of flexural vibration modes in the direction orthogonal to each other at the same frequency.

  According to the present invention, a piezoelectric element used in an ultrasonic motor capable of driving with multiple degrees of freedom, capable of detecting a vibration state and having a simple configuration, and an ultrasonic wave including the piezoelectric element A motor can be provided.

FIG. 3 is an exploded perspective view showing a configuration example of the piezoelectric element according to the first embodiment of the present invention. 1 is a perspective view of a piezoelectric element according to a first embodiment of the present invention. The figure which shows an example of the detailed formation position and shape of the internal electrode formed in the electrode formation surface of the piezoelectric sheet which comprises a detection electrode layer. The figure which shows the vibration direction which concerns on the detection signal canceled in the vibration detection by the piezoelectric active region group of a 1st laminated part. The figure which shows the vibration direction which concerns on the detection signal which is not canceled in the vibration detection by the piezoelectric active region group of a 1st laminated part. The figure which shows an example of the detailed formation position and shape of an internal electrode formed in the electrode formation surface of the piezoelectric sheet which comprises the detection electrode layer in a 2nd laminated part. The figure which shows the vibration direction which concerns on the detection signal canceled in the vibration detection by the piezoelectric active region group of a 2nd laminated part. The figure which shows the vibration direction which concerns on the detection signal which is not canceled in the vibration detection by the piezoelectric active region group of a 2nd lamination | stacking part. The figure which shows one structural example of the external electrode provided with respect to each exposed part of the both sides | surfaces (surface seen from the direction shown by arrow A1, A2 in FIG. 2) in the "1st direction" of a piezoelectric element. The figure which shows one structural example of the external electrode provided with respect to each exposed part of the both sides | surfaces (surface seen from the direction shown by arrow A1, A2 in FIG. 2) in the "1st direction" of a piezoelectric element. The figure which shows one structural example of the external electrode provided with respect to each exposed part of the both sides | surfaces (surface seen from the direction shown by arrow A3, A4 in FIG. 2) in the "2nd direction" of a piezoelectric element. The figure which shows one structural example of the external electrode provided with respect to each exposed part of the both sides (surface seen from the direction shown by arrow A3 in FIG. 2) in the "second direction" of a piezoelectric element. The figure which shows the drive concept of the ultrasonic motor which drives the to-be-driven body which exhibits a substantially spherical shape with multiple degrees of freedom using the piezoelectric element which concerns on 1st Embodiment of this invention. The figure which shows the vibration direction of the longitudinal primary vibration which is a vibration of a piezoelectric element to a "3rd direction". The figure which shows the vibration direction of the bending secondary vibration which is a vibration of the piezoelectric element to a "1st direction". The figure which shows the example of 1 structure of the detection circuit for detecting the vibration of the piezoelectric element at the time of the drive of the ultrasonic motor which concerns on 1st Embodiment of this invention. The figure which shows the graph of an example of the phase difference of the drive signal applied to the external electrode of the drive electrode formation layer of a piezoelectric element, and the detection signal detected from the external electrode of a vibration detection electrode formation layer. The disassembled perspective view which shows one structural example of the piezoelectric element which concerns on 2nd Embodiment of this invention. FIG. 14 is a diagram showing a configuration example of an external electrode provided for each exposed portion on both side surfaces (surfaces viewed from directions indicated by arrows A1 and A2 in FIG. 2) in the “first direction” of the piezoelectric element shown in FIG. FIG. 14 is a diagram illustrating a configuration example of an external electrode provided for each exposed portion on both side surfaces (surfaces viewed from directions indicated by arrows A3 and A4 in FIG. 2) in the “second direction” of the piezoelectric element illustrated in FIG. 13.

Hereinafter, a piezoelectric element and an ultrasonic motor according to embodiments of the present invention will be described with reference to the drawings. An “ultrasonic transducer” can be configured by providing a predetermined piezoelectric element, a holder member, and the like in the “piezoelectric element” according to the embodiment of the present invention. An ultrasonic motor can be configured by providing a predetermined control system and a driven body in the “ultrasonic transducer”.
[First embodiment]
FIG. 1 is an exploded perspective view showing a configuration example of the piezoelectric element 10 according to the first embodiment. FIG. 2 is a perspective view of the piezoelectric element according to the first embodiment.

  As shown in FIGS. 1 and 2, the piezoelectric element 10 includes a first stacked unit 1 including piezoelectric active region groups 11 and 12 (details will be described later) and piezoelectric active region groups 21 and 22 (details will be described later). And a second laminated portion 2 provided. As shown in FIG. 1, the first stacked unit 1 and the second stacked unit 2 are insulated by an insulating sheet 100. Insulating sheets 100 are also disposed at the uppermost and lowermost positions of the piezoelectric element 10. Hereinafter, each laminated part will be described in detail.

  In the first embodiment, a “first direction”, a “second direction”, and a “third direction” are defined as a three-axis orthogonal coordinate system as shown in FIG. That is, the piezoelectric element 10 according to the first embodiment is a piezoelectric element having a structure in which “sheet-like piezoelectric elements (detailed later)” are stacked in the “third direction”.

  The first stacked unit 1 includes a drive electrode formation layer 1-A, a vibration detection electrode formation layer 3, and a drive electrode formation layer 1-B in order from the upper layer side. Similarly, the second stacked portion 2 includes a drive electrode formation layer 2-A, a vibration detection electrode formation layer 4, and a drive electrode formation layer 2-B in order from the upper layer side.

  The drive electrode formation layer 1-A and the drive electrode formation layer 1-B are formed until the piezoelectric sheet 1-1 and the piezoelectric sheet 1-2 on which internal electrodes constituting the drive electrode are formed have a predetermined thickness. It is a layer formed by alternately laminating. The configuration of each piezoelectric sheet will be described in detail later. Here, it is assumed that the drive electrode formation layer 1-A and the drive electrode formation layer 1-B have substantially the same thickness.

  The vibration detection electrode forming layer 3 is a layer in which the piezoelectric sheets 3-1 and the piezoelectric sheets 3-2 constituting the vibration detection electrode are alternately stacked until a predetermined thickness is obtained. The vibration detection electrode formation layer 3 is provided in a form sandwiched between the drive electrode formation layer 1-A and the drive electrode formation layer 1-B described above.

  Similarly, the drive electrode formation layer 2-A and the drive electrode formation layer 2-B have a predetermined thickness of the piezoelectric sheet 2-1 and the piezoelectric sheet 2-2 on which internal electrodes constituting the drive electrode are formed. It is a layer formed by alternately laminating until exhibiting. The configuration of each piezoelectric sheet will be described in detail later. It is assumed that the drive electrode formation layer 2-A and the drive electrode formation layer 2-B have substantially the same thickness.

  The vibration detection electrode forming layer 4 is a layer in which the piezoelectric sheets 4-1 and the piezoelectric sheets 4-2 constituting the vibration detection electrode are alternately stacked until a predetermined thickness is obtained. The vibration detection electrode formation layer 4 is provided in a form sandwiched between the drive electrode formation layer 2-A and the drive electrode formation layer 2-B.

  By the way, the above-described vibration detection electrode forming layers 3 and 4 excite bending vibration (vibration component contributing to driving of the driven body when the piezoelectric element 10 is used in an ultrasonic motor) in the piezoelectric element 10. In this case, it is provided so as to be located in the vicinity of the abdomen of the bending vibration. These vibration detection electrode forming layers 3 and 4 can detect a vibration component related to driving out of vibrations of the piezoelectric element 10. Then, by correcting the vibration state of the piezoelectric element 10 using the detection signal of the bending vibration component, it becomes possible to always perform stable driving without deteriorating the driving characteristics of the motor (details will be described later). ).

Hereinafter, the piezoelectric sheet constituting each layer will be described in detail.
The piezoelectric sheets 1-1, 1-2, 2-1, 2-2, 3-1, 3-2, 4-1, 4-2 are rectangular sheet-like piezoelectric elements. Examples of these materials include hard lead zirconate titanate piezoelectric ceramic elements (PZT).

  Although details will be described later, the piezoelectric sheets 1-1, 1-2, 2-1, 2-2, 3-1, 3-2, 4-1, 4-2 are polarized in the thickness direction. An internal electrode constituting the activation region is provided. As this internal electrode, for example, a silver palladium alloy having a thickness of 4 μm can be mentioned.

First, the piezoelectric sheets 1-1 and 1-2 constituting the drive electrode formation layers 1-A and 1-B, and the piezoelectric sheets 2-1 and 2-2 constituting the drive electrode formation layers 2-A and 2-B. Will be described in detail.
On the electrode formation surface of the piezoelectric sheet 1-1, the internal electrode 1d-1 and the internal electrode 1d-2 are symmetrical with respect to a line that bisects the electrode formation surface in the “first direction”. (In parallel with the “first direction” and in substantially the same shape). The internal electrode 1d-1 is provided with an exposed portion 1d-1e extending toward an edge portion (one edge portion in the “first direction”) of one side of the piezoelectric sheet 1-1. . The internal electrode 1d-2 is provided with an exposed portion 1d-2e extending toward an edge portion on the other side of the piezoelectric sheet 1-1 (an edge portion on the opposite side of the one edge portion). .

  Similarly, on the electrode formation surface of the piezoelectric sheet 1-2, the internal electrode 1d-1 ′ and the internal electrode 1d-2 ′ are lines that bisect the electrode formation surface in the “first direction”. Symmetrically (in parallel with the “first direction” and in substantially the same shape). The internal electrode 1d-1 ′ is provided with an exposed portion 1d-1′e extending toward an edge portion (one edge portion in the “first direction”) of one side of the piezoelectric sheet 1-2. It has been. The internal electrode 1d-2 ′ is provided with an exposed portion 1d-2′e extending toward an edge portion on the other side of the piezoelectric sheet 1-2 (an edge portion on the opposite side of the one edge portion). It has been.

  Here, the exposed portion 1d-1e of the internal electrode 1d-1 formed on the piezoelectric sheet 1-1 and the exposed portion 1d-1'e of the internal electrode 1d-2 formed on the piezoelectric sheet 1-2 are: Although it is provided on the side that overlaps at the time of lamination, the exposed portions 1d-1e and 1d-1′e are provided by being shifted by a predetermined interval so as not to overlap each other.

  Similarly, the exposed portion 1d-2e of the internal electrode 1d-2 formed on the piezoelectric sheet 1-1 and the exposed portion 1d-2′e of the internal electrode 1d-2 formed on the piezoelectric sheet 1-2 are: Although it is provided on the side that overlaps when stacked, the exposed portions 1d-2e and 1d-2′e are provided by being shifted by a predetermined interval so as not to overlap each other.

  As described above, the piezoelectric sheet 1-1 and the piezoelectric sheet 1-2 are piezoelectric sheets having the same pattern of the formed internal electrodes and different patterns for drawing the internal electrodes to the outside. By the way, the polarization direction of the piezoelectric sheet 1-1 and the polarization direction of the piezoelectric sheet 1-2 are opposite to each other (having opposite polarities).

  On the electrode formation surface of the piezoelectric sheet 2-1, the internal electrode 2d-1 and the internal electrode 2d-2 are symmetrical with respect to a line that bisects the electrode formation surface in the “second direction”. (In parallel with the “second direction” and in substantially the same shape). The internal electrode 2d-1 is provided with an exposed portion 2d-1e extending toward an edge portion (one edge portion in the “second direction”) of one side of the piezoelectric sheet 2-1. . The internal electrode 2d-2 is provided with an exposed portion 2d-2e extending toward an edge portion on the other side of the piezoelectric sheet 2-1 (an edge portion on the opposite side of the one edge portion). .

  Similarly, on the electrode formation surface of the piezoelectric sheet 2-2, the internal electrode 2d-1 ′ and the internal electrode 2d-2 ′ are lines that bisect the electrode formation surface in the “second direction”. Symmetrically (in parallel with the “second direction” and substantially in the same shape). The internal electrode 2d-1 ′ is provided with an exposed portion 2d-1′e extending toward an edge portion (one edge portion in the “second direction”) of one side of the piezoelectric sheet 2-2. It has been. The internal electrode 2d-2 ′ is provided with an exposed portion 2d-2′e extending toward an edge portion on the other side of the piezoelectric sheet 2-2 (an edge portion on the opposite side of the one edge portion). It has been.

  Here, the exposed portion 2d-1e of the internal electrode 2d-1 formed on the piezoelectric sheet 2-1 and the exposed portion 2d-1'e of the internal electrode 2d-1 ′ formed on the piezoelectric sheet 2-2 are: The exposed portions 2d-1e and 2d-1'e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  Similarly, the exposed part 2d-2e of the internal electrode 2d-2 formed on the piezoelectric sheet 2-1 and the exposed part 2d-2'e of the internal electrode 2d-2 'formed on the piezoelectric sheet 2-2 The exposed portions 2d-2e and 2d-2'e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  As described above, the piezoelectric sheet 2-1 and the piezoelectric sheet 2-2 are piezoelectric sheets having the same pattern of the formed internal electrodes and different patterns for drawing the internal electrodes to the outside. By the way, the polarization direction of the piezoelectric sheet 2-1 and the polarization direction of the piezoelectric sheet 2-2 are opposite to each other (having opposite polarities).

  It can be said that the piezoelectric sheets 1-1 and 1-2 and the piezoelectric sheets 2-1 and 2-2 have the following relationship. That is, when the piezoelectric sheets 1-1 and 1-2 are rotated by 90 degrees from the “first direction” toward the “second direction”, the same configurations as the piezoelectric sheets 2-1 and 2-2, respectively. This is a piezoelectric sheet. Therefore, the piezoelectric sheets 1-1, 1-2, 2-1, and 2-2 can be obtained by substantially manufacturing only two types of piezoelectric sheets.

Hereinafter, the piezoelectric sheets 3-1 and 3-2 constituting the vibration detection electrode forming layer 3 and the piezoelectric sheets 4-1 and 4-2 constituting the vibration detection electrode forming layer 4 will be described in detail.
On the electrode formation surface of the piezoelectric sheet 3-1, the internal electrode 3d-1 and the internal electrode 3d-2 are symmetrical with respect to a line that bisects the electrode formation surface in the “first direction”. (In parallel with the “first direction” and in substantially the same shape). The internal electrode 3d-1 is provided with an exposed portion 3d-1e extending toward an edge portion (one edge portion in the “first direction”) of one side of the piezoelectric sheet 3-1. . The internal electrode 3d-2 is provided with an exposed portion 3d-2e extending toward an edge portion on the other side of the piezoelectric sheet 3-1 (an edge portion on the opposite side of the one edge portion). .

  On the electrode formation surface of the piezoelectric sheet 3-2, the internal electrode 3d-1 ′ and the internal electrode 3d-2 ′ are in relation to a line that bisects the electrode formation surface in the “first direction”. They are provided symmetrically (in parallel with the “first direction” and in substantially the same shape). The internal electrode 3d-1 ′ is provided with an exposed portion 3d-1′e extending toward an edge portion (one edge portion in the “first direction”) of one side of the piezoelectric sheet 3-2. It has been. The internal electrode 3d-2 ′ is provided with an exposed portion 3d-2′e extending toward an edge portion on the other side of the piezoelectric sheet 3-2 (an edge portion on the opposite side of the one edge portion). It has been.

  Here, the exposed portion 3d-1e of the internal electrode 3d-1 formed on the piezoelectric sheet 3-1 and the exposed portion 3d-1′e of the internal electrode 3d-1 ′ formed on the piezoelectric sheet 3-2 are: The exposed portions 3d-1e and 3d-1′e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  Similarly, the exposed portion 3d-2e of the internal electrode 3d-2 formed on the piezoelectric sheet 3-1 and the exposed portion 3d-2′e of the internal electrode 3d-2 ′ formed on the piezoelectric sheet 3-2 are as follows. The exposed portions 3d-2e and 3d-2'e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  As described above, the piezoelectric sheet 3-1 and the piezoelectric sheet 3-2 are piezoelectric sheets having the same pattern of the formed internal electrodes and different patterns for drawing the internal electrodes to the outside. By the way, the polarization direction of the piezoelectric sheet 3-1 and the polarization direction of the piezoelectric sheet 3-2 are opposite to each other (having opposite polarities).

  On the electrode formation surface of the piezoelectric sheet 4-1, the internal electrode 4d-1 and the internal electrode 4d-2 are symmetrical with respect to a line that bisects the electrode formation surface in the “second direction”. ((In parallel with the “second direction” and substantially in the same shape)). The internal electrode 4d-1 is provided with an exposed portion 4d-1e extending toward an edge portion (one edge portion in the “second direction”) of one side of the piezoelectric sheet 4-1. . The internal electrode 4d-2 is provided with an exposed portion 4d-2e extending toward an edge portion on the other side of the piezoelectric sheet 4-1 (an edge portion on the opposite side of the one edge portion). .

  On the electrode forming surface of the piezoelectric sheet 4-2, the internal electrode 4 d-1 ′ and the internal electrode 4 d-2 ′ are divided with respect to a line that bisects the electrode forming surface in the “second direction”. They are provided symmetrically (in parallel with the “second direction” and in substantially the same shape). The internal electrode 4d-1 ′ is provided with an exposed portion 4d-1′e extending toward an edge portion (one edge portion in the “second direction”) of one side of the piezoelectric sheet 4-2. It has been. The internal electrode 4d-2 ′ is provided with an exposed portion 4d-2′e extending toward an edge portion on the other side of the piezoelectric sheet 4-2 (an edge portion opposite to the one edge portion). It has been.

  Here, the exposed portion 4d-1e of the internal electrode 4d-1 formed on the piezoelectric sheet 4-1 and the exposed portion 4d-1′e of the internal electrode 4d-1 ′ formed on the piezoelectric sheet 4-2 are as follows. The exposed portions 4d-1e and 4d-1'e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  Similarly, the exposed portion 4d-2e of the internal electrode 4d-2 formed on the piezoelectric sheet 4-1 and the exposed portion 4d-2'e of the internal electrode 4d-2 ′ formed on the piezoelectric sheet 4-2 are as follows. The exposed portions 4d-2e and 4d-2′e are provided so as to be shifted from each other by a predetermined interval so as not to overlap each other.

  As described above, the piezoelectric sheet 4-1 and the piezoelectric sheet 4-2 are piezoelectric sheets having the same pattern of the formed internal electrodes and different patterns for drawing the internal electrodes to the outside. By the way, the polarization direction of the piezoelectric sheet 4-1 and the polarization direction of the piezoelectric sheet 4-2 are opposite to each other (having opposite polarities).

  It can be said that the piezoelectric sheets 3-1 and 3-2 and the piezoelectric sheets 4-1 and 4-2 have the following relationship. That is, when the piezoelectric sheets 3-1 and 3-2 are rotated by 90 degrees from the “first direction” toward the “second direction”, the same configurations as the piezoelectric sheets 4-1 and 4-2, respectively. This is a piezoelectric sheet. Accordingly, the piezoelectric sheets 3-1, 3-2, 4-1 and 4-2 can be obtained by substantially manufacturing only two types of piezoelectric sheets.

  The exposed portions 3d-1e and 3d-1′e and the exposed portions 1d-1e and 1d-1′e of the piezoelectric sheets 1-1 and 1-2 described above are provided on the sides that overlap when stacked. However, the exposed portions 1d-1e, 1d-1'e, 3d-1e, 3d-1'e are provided so as to be shifted by a predetermined interval so as not to overlap each other.

  Similarly, the exposed portions 4d-1e and 4d-1'e and the exposed portions 2d-1e and 2d-1'e of the piezoelectric sheets 2-1 and 2-2 are provided on sides that overlap when stacked. However, the exposed portions 2d-1e, 2d-1'e, 4d-1e, and 4d-1'e are provided by being shifted by a predetermined interval so as not to overlap each other.

The piezoelectric element 10 according to the first embodiment adopts the above-described laminated structure, and is manufactured, for example, by integral firing. And in the 1st lamination | stacking part 1 and the 2nd lamination | stacking part 2, a piezoelectric active region group is provided as follows.
In the first laminated portion 1, the internal electrode 1d-1 of the piezoelectric sheet 1-1, the internal electrode 1d-1 'of the piezoelectric sheet 1-2, and the internal electrode 3d-1 of the piezoelectric sheet 3-1. And the area | region corresponding to the internal electrode 3d-1 'of the said piezoelectric sheet 3-2 comprises the piezoelectric active area group 11 activated piezoelectrically. Similarly, the internal electrode 1d-2 of the piezoelectric sheet 1-1, the internal electrode 1d-2 'of the piezoelectric sheet 1-2, the internal electrode 3d-2 of the piezoelectric sheet 3-1, and the piezoelectric sheet 3 -2 corresponding to the internal electrodes 3d-2 'constitute a piezoelectrically active region group 12 that is piezoelectrically activated.

  In the second laminated portion 2, the internal electrode 2d-1 of the piezoelectric sheet 2-1, the internal electrode 2d-1 'of the piezoelectric sheet 2-2, and the internal electrode 4d-1 of the piezoelectric sheet 4-1. And the area | region corresponding to the internal electrode 4d-1 'of the said piezoelectric sheet 4-2 comprises the piezoelectric active area group 21 activated piezoelectrically. Similarly, the internal electrode 2d-2 of the piezoelectric sheet 2-1, the internal electrode 2d-2 'of the piezoelectric sheet 2-2, the internal electrode 4d-2 of the piezoelectric sheet 4-1, and the piezoelectric sheet 4 -2 corresponding to the internal electrodes 4d-2 'constitute a piezoelectric active region group 22 that is piezoelectrically activated.

FIG. 3 is a diagram illustrating an example of detailed formation positions and shapes of the internal electrodes 3d-1 and 3d-2 formed on the electrode formation surface of the piezoelectric sheet 3-1 constituting the detection electrode layer 3.
For convenience of explanation, as shown in FIG. 3, the “first direction axis” and the “second direction axis” are set so that each side of the piezoelectric sheet 3-1 is divided into two equal parts. The internal electrode 3d-1 is formed symmetrically with respect to the “first direction axis” and includes the “first direction axis”. Similarly, the internal electrode 3d-2 is formed symmetrically with respect to the “first direction axis” and includes the “first direction axis”. Here, the internal electrode 3d-1 and the internal electrode 3d-2 are formed symmetrically with respect to the “second direction axis”.

By forming the internal electrodes 3d-1 and 3d-2 in the shape and position as described above on the piezoelectric sheet 3-1, driving in the "second direction" (around the "first direction axis") During the expansion and contraction of the piezoelectric element 10 for driving), one side and the other of the internal electrodes 3d-1 and 3d-2 in the piezoelectric active region groups 11 and 12, respectively, with the first direction axis as a boundary. Stretching in the opposite direction to each side. As a result, charges having opposite polarities are generated in the respective surfaces of the internal electrodes 3d-1 and 3d-2. Then, the charges having opposite polarities are canceled (cancelled) in each surface of the internal electrodes 3d-1 and 3d-2 (see FIG. 4A).
On the other hand, at the time of expansion / contraction of the piezoelectric element 10 for driving in the “first direction” (driving around the “second direction axis”), the internal electrodes 3d-1, 3d− in the piezoelectric active region groups 11, 12 respectively. In each of the two planes, expansion and contraction in one direction is performed. As a result, a charge of one polarity (positive or negative) is generated in each surface of the internal electrodes 3d-1, 3d-2. Then, this electric charge is detected as a vibration detection signal (see FIG. 4B). The relationship between the charge generated in the internal electrode 3d-1 and the charge generated in the internal electrode 3d-2 is opposite to each other.

In other words, the piezoelectric active region groups 11 and 12 of the first stacked unit 1 can detect vibration only for driving in the “first direction” (driving around the “second direction axis”).
As described above, the piezoelectric sheet 3-2 is different only in the position of the exposed portion, and the vibration detection is the same as that of the piezoelectric sheet 3-1, and thus the description thereof is omitted here.

FIG. 5 is a diagram showing an example of detailed formation positions and shapes of the internal electrodes 4d-1 and 4d-2 formed on the electrode formation surface of the piezoelectric sheet 4-1 constituting the detection electrode layer 4. As shown in FIG.
For convenience of explanation, as shown in FIG. 4, the “first direction axis” and the “second direction axis” are set so that each side of the piezoelectric sheet 4-1 is divided into two equal parts. The internal electrode 4d-1 is formed symmetrically with respect to the “second direction axis” and includes the “second direction axis”. Similarly, the internal electrode 4d-2 is formed symmetrically with respect to the “second direction axis” and includes the “second direction axis”. Here, the internal electrode 4d-1 and the internal electrode 4d-2 are formed symmetrically with respect to the “first direction axis”.

By forming the internal electrodes 4d-1 and 4d-2 in the shape and position as described above on the piezoelectric sheet 4-1, driving in the "first direction" (around the "second direction axis") During the expansion and contraction of the piezoelectric element 10 for driving), one side and the other of the internal electrodes 4d-1 and 4d-2 in the piezoelectric active region groups 21 and 22, respectively, with the second direction axis as a boundary. Stretching in the opposite direction to each side. As a result, charges having opposite polarities are generated in the respective surfaces of the internal electrodes 4d-1 and 4d-2. The charges having opposite polarities are canceled (cancelled) in the respective surfaces of the internal electrodes 4d-1 and 4d-2 (see FIG. 6A).
On the other hand, during expansion / contraction of the piezoelectric element 10 for driving in the “second direction” (driving around the “first direction axis”), the internal electrodes 4d-1, 4d− are respectively provided in the piezoelectric active region groups 21, 22. In one plane, expansion and contraction in one direction is performed. As a result, a charge of one polarity (positive or negative) is generated in each surface of the internal electrodes 4d-1 and 4d-2. Then, this charge is detected as a vibration detection signal (see FIG. 6B). Note that the charge generated in the internal electrode 4d-1 and the charge generated in the internal electrode 4d-2 have opposite polarities.

That is, the piezoelectric active region groups 21 and 22 of the second stacked unit 2 can detect vibrations only for driving in the “second direction” (driving around the “first direction axis”).
As described above, the piezoelectric sheet 4-2 is different only in the position of the exposed portion, and the vibration detection is the same as that of the piezoelectric sheet 4-1.

  As described above, in the piezoelectric element 10 according to the first embodiment, the vibration for detecting the vibration only in the “first direction” in the first stacked unit 1 (piezoelectric active region groups 11 and 12). The detection electrode formation layer 3 is provided, and the vibration detection electrode formation layer 4 for detecting vibration only in the “second direction” in the second stacked portion 2 (piezoelectric active regions 21 and 22) is employed. Thereby, vibration detection can be performed separately for the bending vibration in the “first direction” and the bending vibration in the “second direction”.

7A and 7B show an example of the configuration of the external electrodes provided for the exposed portions on both side surfaces (the surfaces viewed from the directions indicated by arrows A1 and A2 in FIG. 2) in the “first direction” of the piezoelectric element 10. FIG. In FIG. 2, the surface viewed from the direction indicated by the arrow A1 (hereinafter referred to as the first side surface) and the surface viewed from the direction indicated by the arrow A2 (hereinafter referred to as the second side surface) are apparent. The configuration of is the same. Therefore, in FIG. 7A and FIG. 7B, reference numerals corresponding to the above-described both side surfaces are given in each drawing, and each component will be described.
The exposed portions 1d-1e corresponding to the internal electrode 1d-1 on the first side surface are short-circuited by the external electrode 1d-1E.
The exposed portions 1d-2e corresponding to the internal electrode 1d-2 on the second side surface are short-circuited by the external electrode 1d-2E.
The exposed portions 3d-1′e corresponding to the internal electrodes 3d-1 ′ on the first side surface are short-circuited by the external electrodes 3d-1′E.
The exposed portions 3d-2′e corresponding to the internal electrodes 3d-2 ′ on the second side surface are short-circuited by the external electrodes 3d-2′E.
The exposed portions 1d-1′e corresponding to the internal electrodes 1d-1 ′ on the first side surface are short-circuited by the external electrodes 1d-1′E.
The exposed portions 1d-2′e corresponding to the internal electrodes 1d-2 ′ on the second side surface are short-circuited by the external electrodes 1d-2′E.
The exposed portions 3d-1e corresponding to the internal electrode 3d-1 on the first side surface are short-circuited by the external electrode 3d-1E.
The exposed portions 3d-2e corresponding to the internal electrode 3d-2 on the second side surface are short-circuited by the external electrode 3d-2E.

  It should be noted that the external electrodes 1d-1E, 1d-2E, 1d-1′E, and 1d-2′E need only be provided for the corresponding exposed portions, as shown in FIG. 7A. The shape may be a substantially “U” shape, or may be a substantially “I” shape as shown in FIG. 7B.

FIG. 8A and FIG. 8B show a configuration example of the external electrode provided for each exposed portion on both side surfaces (surfaces viewed from the directions indicated by arrows A3 and A4 in FIG. 2) in the “second direction” of the piezoelectric element. FIG. In FIG. 2, the surface viewed from the direction indicated by the arrow A3 (hereinafter referred to as the third side surface) and the surface viewed from the direction indicated by the arrow A4 (hereinafter referred to as the fourth side surface) are apparent. The configuration of is the same. Therefore, in FIG. 8A and FIG. 8B, the reference numerals corresponding to the both side surfaces described above are attached in each drawing, and each component will be described.
The exposed portions 2d-2e corresponding to the internal electrode 2d-2 on the third side surface are short-circuited by the external electrode 2d-2E.
The exposed portions 2d-1e corresponding to the internal electrode 2d-1 on the fourth side surface are short-circuited by the external electrode 2d-1E.
The exposed portions 4d-2′e corresponding to the internal electrodes 4d-2 ′ on the third side are short-circuited by the external electrodes 4d-2′E.
The exposed portions 4d-1′e corresponding to the internal electrodes 4d-1 ′ on the fourth side surface are short-circuited by the external electrodes 4d-1′E.
The exposed portions 4d-2e corresponding to the internal electrode 4d-2 on the third side surface are short-circuited by the external electrode 4d-2E.
The exposed portions 4d-1e corresponding to the internal electrode 4d-1 on the fourth side surface are short-circuited by the external electrode 4d-1E.
The exposed portions 2d-2′e corresponding to the internal electrodes 2d-2 ′ on the third side surface are short-circuited by the external electrodes 2d-2′E.
The exposed portions 2d-1′e corresponding to the internal electrodes 2d-1 ′ on the fourth side surface are short-circuited by the external electrodes 2d-1′E.

  It should be noted that the external electrodes 2d-2E, 2d-1′E, 2d-2′E, and 2d-1′E have only to be provided to the corresponding exposed portions, as shown in FIG. 8A. As shown in FIG. 8B, it may have a substantially “U” shape or a substantially “I” shape.

Hereinafter, an example of the vibration excited by the piezoelectric element 10 will be described in detail. FIG. 9 is a diagram showing a driving concept of an ultrasonic motor that drives a driven body having a substantially spherical shape with multiple degrees of freedom using the piezoelectric element according to the first embodiment.
As shown in FIG. 9, when driving signals (AC signals AC) having a predetermined phase difference are input to the piezoelectric active region group 11 and the piezoelectric active region group 12 of the piezoelectric element described above, Is a combination of longitudinal primary vibration that is vibration in the “third direction” as shown in FIG. 10A and bending secondary vibration that is vibration in the “first direction” as shown in FIG. 10B. A complex vibration is excited. The end face 10c of the piezoelectric element 10 in the resonance state in which the composite vibration is excited vibrates so as to draw an elliptical locus.

  Here, a predetermined pressing member (not shown) is used for the spherical driven body 50 that can be rotated in multiple degrees of freedom (that is, in any of the x, y, and z directions shown in FIG. 9). When the end face 10c of the piezoelectric element 10 is brought into pressure contact, the driven body 50 rotates around the axis in the “second direction” (in the direction of the arrow y).

  In the same principle, when an AC signal is input to the piezoelectric active region groups 21 and 22 (not shown in FIG. 9) of the second stacked portion 2, resonance vibration is excited in the piezoelectric element 10 and the end face 10c. The driven body 50 that is in pressure contact with the head performs a rotational motion around the axis in the “first direction” (arrow x direction).

  Although not shown, a friction contact (driving element) for frictionally driving the driven body 50 is provided on the end face 10c of the piezoelectric element 10, and the piezoelectric element 10 is interposed via the friction contact. In contact with the driven member 50. Similarly, although not shown, a support member for rotatably supporting the driven body 50 with the above-described multiple degrees of freedom (around a plurality of axes) is provided.

  Then, the rotational movement around the axis in the “first direction” (arrow x direction) and the rotational movement around the axis in the “second direction” (arrow y direction) described above are executed in combination. The driving body 50 can be rotated around the axis in the “third direction” (arrow z direction). In the ultrasonic motor using the piezoelectric element 10 according to the first embodiment, by inputting a drive signal as described above, the spherical driven body 50 can be moved in multiple degrees of freedom (that is, x shown in FIG. 9). Driving in any direction, y-direction or z-direction).

  Hereinafter, the vibration detection method when the ultrasonic motor according to the first embodiment is driven by the above-described driving method will be described in detail. FIG. 11 is a diagram illustrating a configuration example of a detection circuit for detecting the vibration of the piezoelectric element when the ultrasonic motor according to the first embodiment is driven. FIG. 12 is a graph illustrating an example of a phase difference between a drive signal applied to the internal electrode of the drive electrode formation layer of the piezoelectric element 10 and a detection signal detected from the internal electrode of the vibration detection electrode formation layer. .

In the example shown in FIG. 11, the detection circuit includes a control unit 122 including a known generator 122a, phase converter 122b, calculator 122c, and clock 122d, phase difference detection circuits 128-1 and 128-2, and a drive circuit. 130-1, 130-2, buffers 135-1, 135-2, and comparators 140-1, 140-2.
The drive circuit 130-1 is connected to the external electrodes 1d-1E. The buffer 135-1 is connected to the external electrode 3d-1′E. The drive circuit 130-2 is connected to the external electrode 2d-1′E. The buffer 135-2 is connected to the external electrode 4d-2′E.

  That is, the detection circuit of the example shown in FIG. 11 performs vibration detection on the piezoelectric active region group 11 in the first stacked unit 1 and the piezoelectric active region group 22 in the second stacked unit 2. A circuit for performing the operation. In other words, the detection circuit of the example shown in FIG. 11 includes a circuit for detecting vibration in the “first direction” and a circuit for detecting vibration in the “second direction”.

  Specifically, vibration detection and drive control are performed as follows. First, an electrical signal generated in the internal electrode 3d-1′e of the vibration detection electrode formation layer 3 during driving is input from the external electrode 3d-1′E to the comparator 140-1 via the buffer 135-1 and is supplied to the A / A D-converted and output to the phase difference detection circuit 128-1.

On the other hand, the drive signal applied to the internal electrodes 1d-1 of the drive electrode formation layers 1-A and 1-B by the drive circuit 130 via the external electrodes 1d-1E under the control of the control unit 122 is a phase difference phase difference. It is also output to the detection circuit 128-1.
Then, a drive signal applied to the internal electrode 1d-1 of the drive electrode formation layers 1-A and 1-B and an electric signal generated in the internal electrode 3d-1′e of the vibration detection electrode formation layer 3 The phase difference is detected by the phase difference detection circuit 128-1.

  Further, the control unit 122 performs control to change the frequency of the drive signal so that the phase difference detected by the above-described processing becomes a predetermined value (so as to keep the predetermined value). By such vibration detection and drive control, even when the vibration state changes due to an external factor, for example, the ultrasonic motor is stably driven.

  More specifically, the control unit 122, as shown in FIG. 12, has two-phase drive signals having a predetermined phase difference (in this example, an A-phase input signal indicated by a solid line and a B-phase input signal indicated by a broken line). The phase difference between the falling pulse of the signal whose phase is advanced (B-phase input signal in this example) and the rising pulse of the detection signal indicated by the alternate long and short dash line keeps a predetermined phase relationship (this example Then, control is performed to change the frequency of the drive signal so that the phase difference is maintained at 45 [deg]; that is, the phase difference between the two rising pulses is maintained at 130 [deg].

The ultrasonic motor according to the first embodiment includes a control system that performs such correction processing for each of the two vibration detection electrode forming layers 3 and 4 for detecting two bending vibrations. And it controls individually.
As described above, according to the first embodiment, the piezoelectric element is used in an ultrasonic motor capable of driving with multiple degrees of freedom, and can detect a vibration state and has a simple configuration. In addition, an ultrasonic motor including the piezoelectric element can be provided.

  Specifically, vibration detection is performed between the drive electrode formation layer 1-A and the drive electrode formation layer 1-B in the first laminated portion 1 and at a position near the abdomen in the bending vibration of the piezoelectric element 10. An electrode forming layer 3 is provided. Similarly, vibration detection is performed between the vibration detection electrode formation layer 2-A and the vibration detection electrode formation layer 2-B in the second laminated portion 2 and at a position near the abdomen in the bending vibration of the piezoelectric element 10. An electrode forming layer 4 is provided.

  With this configuration, it is possible to individually detect the vibration component related to the bending vibration in the “first direction” of the piezoelectric element 10 and the vibration component related to the bending vibration in the “second direction”. Thus, correction control using the detection signal becomes possible. That is, by detecting a change in the vibration state due to an external factor (for example, temperature change, load fluctuation, etc.) and performing correction control based on the detection result, the multi-degree-of-freedom driving ultrasonic wave including the piezoelectric element 10 is performed. The motor can always be driven stably.

In the first embodiment, in addition to the laminated structure piezoelectric element obtained by integrally firing, a piezoelectric element having a structure in which a plurality of single-plate piezoelectric elements are integrally combined, or a plurality of piezoelectric elements in a metal having a recess. Needless to say, the present invention can also be applied to a piezoelectric element or the like having an integrated structure. In addition, the stacking direction of the piezoelectric elements 10 may be any one of “first direction”, “second direction”, “third direction”, and “direction combining them”.
[Second Embodiment]
Hereinafter, a piezoelectric element and an ultrasonic motor according to a second embodiment of the present invention will be described. In order to avoid duplication of explanation, only differences from the first embodiment will be described. One of the main differences from the first embodiment is the configuration of the vibration detection electrode forming layer and the configuration of the external electrode.

  FIG. 13 is an exploded perspective view showing a configuration example of the piezoelectric element according to the second embodiment of the present invention. 14A is a configuration example of an external electrode provided for each exposed portion on both side surfaces (surfaces viewed from directions indicated by arrows A1 and A2 in FIG. 2) in the “first direction” of the piezoelectric element shown in FIG. FIG. FIG. 14B is a configuration example of the external electrode provided for each exposed portion on both side surfaces (the surface viewed from the directions indicated by arrows A3 and A4 in FIG. 2) in the “second direction” of the piezoelectric element shown in FIG. FIG.

  In the piezoelectric element 10 according to the second embodiment, a vibration detection electrode forming layer 5 described later is provided in place of the vibration detection electrode forming layer 3 in the first stacked unit 1 of the piezoelectric element 10 according to the first embodiment. ing. Similarly, a vibration detection electrode forming layer 5 described later is provided instead of the vibration detection electrode forming layer 4 in the second stacked portion 2 of the piezoelectric element 10 according to the first embodiment.

Hereinafter, the vibration detection electrode forming layer 5 will be described in detail. The vibration detection electrode forming layer 5 is formed by alternately stacking piezoelectric sheets 5-1 and piezoelectric sheets 5-2.
On the electrode formation surface of the piezoelectric sheet 5-1, the internal electrode 5d-1 and the internal electrode 5d-2 are symmetrical with respect to a line that bisects the electrode formation surface in the “first direction”. (In parallel with the “first direction” and in substantially the same shape). The internal electrode 5d-1 is provided with an exposed portion 5d-1e extending toward an edge portion (one edge portion in the “first direction”) of one side of the piezoelectric sheet 5-1. . The internal electrode 5d-2 is provided with an exposed portion 5d-2e extending toward an edge portion on the other side of the piezoelectric sheet 5-1 (an edge portion on the opposite side of the one edge portion). .

  Furthermore, on the electrode formation surface of the piezoelectric sheet 5-1, the internal electrode 5d-3 and the internal electrode 5d-4 are arranged with respect to a line that bisects the electrode formation surface in the “second direction”. They are provided symmetrically (in parallel with the “second direction” and in substantially the same shape). The internal electrode 5d-3 is provided with an exposed portion 5d-3e extending toward an edge portion of one side of the piezoelectric sheet 5-1 (one edge portion in the “second direction”). . The internal electrode 5d-4 is provided with an exposed portion 5d-4e extending toward the edge portion of the other side in the “second direction” of the piezoelectric sheet 5-1.

Similarly, on the electrode forming surface of the piezoelectric sheet 5-2, the internal electrodes 5d-1 ′ to 5d corresponding to the internal electrodes 5d-1 to 5d-4 in the piezoelectric sheet 5-1, respectively. -4 'are formed at the corresponding positions.
The exposed portions 5d-1'e to 5d-4'e of the internal electrodes 5d-1 'to 5d-4' are respectively extended from the corresponding exposed portions 5d-1e to 5d-4e. It is provided toward the side corresponding to the side that has been set. However, the exposed portions 5d-1′e to 5d-4′e are provided at positions that do not overlap with the corresponding exposed portions 5d-1e to 5d-4e in the stacked state.

  As described above, the piezoelectric sheet 5-1 and the piezoelectric sheet 5-2 are piezoelectric sheets having the same internal electrode pattern and different patterns for drawing the internal electrodes to the outside. By the way, the polarization direction of the piezoelectric sheet 5-1 and the polarization direction of the piezoelectric sheet 5-2 are opposite to each other (having opposite polarities).

  Here, the ultrasonic motor according to the second embodiment is provided with a detection circuit for two bending vibration modes separately, so that a drive signal can be simultaneously transmitted to the first stacked unit 1 and the second stacked unit 2. Simultaneously applied, it is possible to perform correction control with higher accuracy for two bending vibrations. That is, it is possible to perform correction control using signals from individual detection electrodes for each of the two bending vibration modes. In this case, for example, a so-called “differential input” can amplify a minute signal during minute driving. Therefore, the ultrasonic motor can be driven more stably.

  As described above, according to the second embodiment, the same effect as that of the piezoelectric element and the ultrasonic motor according to the first embodiment can be obtained. A piezoelectric element and an ultrasonic motor capable of highly accurate vibration detection can be provided.

The present invention has been described based on the first to second embodiments. However, the present invention is not limited to the above-described embodiments, and within the scope of the present invention, for example, the following Of course, variations and applications are possible.
Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention can be achieved. In the case of being obtained, a configuration from which this configuration requirement is deleted can also be extracted as an invention.

    DESCRIPTION OF SYMBOLS 1 ... 1st laminated part, 2 ... 2nd laminated part, 1-A, 1-B, 2-A, 2-B ... Drive electrode formation layer, 1-1, 1-2, 2-1, 2 -2, 3-1, 3-2, 4-1, 4-1, 5-1 ... piezoelectric sheet, 1d-1, 1d-2, 2d-1, 2d-2, 3d-1, 3d-2, 4d-1, 4d-2, 5d-1, 5d-2, 5d-3, 5d-4, 1d-1 ', 1d-2', 2d-1 ', 2d-2', 3d-1 ', 3d -2 ', 4d-1', 4d-2 ', 5d-1', 5d-2 ', 5d-3', 5d-4 '... internal electrodes, 1d-1e, 1d-2e, 2d-1e, 2d -2e, 3d-1e, 3d-2e, 4d-1e, 4d-2e, 5d-1e, 5d-2e, 5d-3e, 5d-4e, 1d-1'e, 1d-2'e, 2d-1 'E, 2d-2'e, 3d-1'e, 3d-2'e, 4 -1′e, 4d-2′e, 5d-1′e, 5d-2′e, 5d-3′e, 5d-4′e... Exposed portions, 1d-1E, 1d-2E, 2d-1E, 2d-2E, 3d-1E, 3d-2E, 4d-1E, 4d-2E, 5d-1E, 5d-2E, 5d-3E, 5d-4E, 1d-1'E, 1d-2'E, 2d- 1'E, 2d-2'E, 3d-1'E, 3d-2'E, 4d-1'E, 4d-2'E, 5d-1'E, 5d-2'E, 5d-3 ' E, 5d-4′E: external electrode, 10: piezoelectric element, 3, 4, 5 ... vibration detection electrode forming layer, 11, 12, 21, 22 ... piezoelectric active region group, 50 ... driven body, 100 ... insulation Sheet, 122 ... Control unit, 128 ... Phase difference detection circuit, 128 ... Phase difference phase difference detection circuit, 130 ... Drive circuit, 135 ... Buffer, 140 ... Comparator Ta.

Claims (9)

A piezoelectric element used in an ultrasonic transducer that drives a driven body by a plurality of vibration modes excited by applying a predetermined drive signal,
Among vibrations in the plurality of vibration modes, comprising a vibration detection electrode layer including a vibration detection electrode for detecting a vibration component in a propulsion direction when driving the driven body in a plurality of axial directions,
The piezoelectric element is characterized in that the vibration detection electrode layer is provided in the vicinity of the abdomen in a plurality of bending vibration modes in the direction orthogonal to each other at the same frequency. In the three-axis orthogonal coordinate system including the first direction, the second direction, and the third direction, the piezoelectric element has the third direction as a longitudinal direction,
At least two first piezoelectric active regions disposed in parallel in the first direction on one side portion of the piezoelectric element that is substantially divided into two in the third direction;
At least two second piezoelectric active regions arranged in parallel in the second direction in the other side portion of the piezoelectric element that is substantially divided into two parts in the third direction;
Comprising
The first piezoelectric active region and the second piezoelectric active region are:
The vibration detection electrode layer;
A drive electrode layer disposed so as to sandwich the vibration detection electrode layer from the third direction, to which the predetermined drive signal is applied;
The piezoelectric element according to claim 1, comprising: The vibration detection electrode layer provided in the first piezoelectric active region detects a vibration component in a propulsion direction in the first direction,
The piezoelectric element according to claim 2, wherein the vibration detection electrode layer included in the second piezoelectric active region detects a vibration component in a propulsion direction in the second direction. The vibration detection electrode layer included in the first piezoelectric active region further includes a piezoelectric active region disposed in parallel with the second direction, and the vibration component in the propulsion direction in the first direction and the second The vibration component in the propulsion direction in the direction of
The vibration detection electrode layer included in the second piezoelectric active region further includes a piezoelectric active region disposed in parallel with the first direction, and the vibration component in the propulsion direction in the first direction and the second The piezoelectric element according to claim 3, wherein a vibration component in the propulsion direction is detected. A driven body having a substantially spherical shape;
A piezoelectric element that drives the driven body in multiple degrees of freedom by a plurality of vibration modes excited by applying a predetermined driving signal;
A friction contact provided on a surface of the piezoelectric element facing the driven body;
A pressing member that applies a pressing force to the piezoelectric element and press-contacts the piezoelectric element to the driven body via the friction contact;
A support member for rotatably supporting the driven body around a plurality of axes;
A controller for driving the piezoelectric element by outputting a two-phase alternating signal as the driving signal and detecting a vibration state of the piezoelectric element;
Comprising
The piezoelectric element includes a vibration detection electrode layer including a vibration detection electrode that detects a vibration component in a propulsion direction when driving the driven body in a plurality of axial directions among vibrations in the plurality of vibration modes.
The ultrasonic motor is characterized in that the vibration detection electrode is provided in the vicinity of the abdomen in a plurality of bending vibration modes in the direction orthogonal to each other at the same frequency. In the three-axis orthogonal coordinate system including the first direction, the second direction, and the third direction, the piezoelectric element has the third direction as a longitudinal direction,
At least two first piezoelectric active regions disposed in parallel in the first direction on one side portion of the piezoelectric element that is substantially divided into two in the third direction;
At least two second piezoelectric active regions arranged in parallel in the second direction in the other side portion of the piezoelectric element that is substantially divided into two parts in the third direction;
Comprising
The first piezoelectric active region and the second piezoelectric active region are:
The vibration detection electrode layer;
A drive electrode layer disposed so as to sandwich the vibration detection electrode layer from the third direction, to which the predetermined drive signal is applied;
The ultrasonic motor according to claim 5, comprising: The vibration detection electrode layer provided in the first piezoelectric active region detects a vibration component in a propulsion direction in the first direction,
The ultrasonic motor according to claim 6, wherein the vibration detection electrode layer included in the second piezoelectric active region detects a vibration component in a propulsion direction in the second direction. The vibration detection electrode layer included in the first piezoelectric active region further includes a piezoelectric active region disposed in parallel with the second direction, and the vibration component in the propulsion direction in the first direction and the second The vibration component in the propulsion direction in the direction of
The vibration detection electrode layer included in the second piezoelectric active region further includes a piezoelectric active region disposed in parallel with the first direction, and the vibration component in the propulsion direction in the first direction and the second The ultrasonic motor according to claim 7, wherein a vibration component in the propulsion direction is detected. The control unit includes a phase of a signal output from the vibration detection electrode layer included in the first piezoelectric active region and a phase of the drive signal output from the vibration detection electrode layer included in the second piezoelectric active region. The ultrasonic motor according to claim 6, wherein the frequency of the drive signal is controlled so that the phase difference becomes a predetermined value.

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