JP2010246347A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor for driving a mover in forward and backward directions by switching electrodes which applies an alternating voltage, and obtains a high driving efficiency. <P>SOLUTION: The alternating voltage is applied to one selected from first or second selection driving electrodes 41c, 41d, and common driving electrodes 41a, 41b in the ultrasonic motor 10. A piezoelectric ceramic plate 101 is resonated along a flat surface direction, by opening the second or first selection driving electrodes 41d, 41c. A biasing unit 103 vibrates in circumferential and radial directions of the piezoelectric ceramic plate 101, with larger displacement in a radial direction than in the circumferential direction. The phase of the circumferential vibration and the radial vibration of the biasing unit 103 is inverted by changing the selection of the first or second selection driving electrodes 41c, 41d. Then, the feed direction of the mover 107 biased by the biasing unit 103 is changed in forward or backward directions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor.

Recently, small ultrasonic motors are widely used for applications such as camera autofocus and lens drive for camera shake correction. Various ultrasonic motors are also used for driving a flat substrate called an XY stage, which is free from the influence of a magnetic field, because it generates less noise and less electromagnetic noise.
In recent ultrasonic motors, in addition to further miniaturization, an easy switching drive of the moving element in the forward direction and the reverse direction is required.

  The principle of driving an ultrasonic motor is that the main surface of a plate-shaped piezoelectric vibrator is divided into a plurality of regions to form electrodes, and an alternating voltage is applied to these electrodes to resonate the piezoelectric vibrator. What drives a child is known. Then, by switching the electrodes to which the alternating voltage is applied, the vibration direction of the piezoelectric vibrator is reversed, and the moving direction of the moving element is switched between forward and reverse.

As this type of ultrasonic motor, one described in Patent Document 1 below has been proposed.
In the motor described in Patent Document 1, electrodes A, B, C, and D are arranged by dividing one main surface of a disk-shaped piezoelectric vibrator polarized in the thickness direction into four equal parts (Patent Document). 1 (see FIG. 1). Electrodes a, b, c, and d are formed on the other main surface of the piezoelectric vibrator at positions facing the electrodes A, B, C, and D, respectively, and electrodes A and c, B and d, and C and a , And D and b are electrically connected so that the electrodes A, B, c, d are equipotential, and the electrodes a, b, C, D are equipotential. The rotor is rotated by applying an alternating voltage in which the polarity of the voltage is reversed to the pair of electrodes A, B, c, and d and the pair of electrodes a, b, C, and D, respectively. To drive. That is, in the motor of Patent Document 1, the direction of the electric field is different between the half area of the piezoelectric ceramic plate and the other half area.
Further, in the motor described in the same document, the combination of electrodes having the same potential is changed by switching the two-circuit four-contact switch connected to the common terminal, and the rotation direction of the rotor is reversed.

Japanese Patent Laid-Open No. 06-98568

  However, in the motor described in Patent Document 1, since an alternating voltage is applied to all the electrodes provided on the main surface of the piezoelectric vibrator, the entire piezoelectric vibrator is electrically short-circuited. Become. For this reason, there is a problem that a sufficient amount of resonance displacement of the piezoelectric vibrator cannot be obtained with respect to the applied alternating voltage, and the driving efficiency of the moving element is low.

  The present invention has been made in view of the problems of the conventional ultrasonic motor described above, and can move the moving element in the forward and reverse directions by switching the electrodes to which the alternating voltage is applied, and has high driving. An ultrasonic motor capable of obtaining efficiency is provided.

The ultrasonic motor of the present invention is a plate-like piezoelectric vibrator polarized in the thickness direction and having one main surface partitioned into a plurality of regions,
First and second selective drive electrodes and common drive electrodes, which are individually formed in the region and applied with an alternating voltage;
An earth electrode formed on the other main surface of the piezoelectric vibrator;
An urging portion provided on an outer periphery of the piezoelectric vibrator,
Applying the alternating voltage between one selected from the first or second selection drive electrode and the common drive electrode and the ground electrode, and opening the second or first selection drive electrode, The piezoelectric vibrator resonates in a plane direction, and the biasing portion vibrates in a circumferential direction and a radial direction of the piezoelectric vibrator with a larger displacement in the radial direction than in the circumferential direction; and
By switching the selection of the first or second selection drive electrode, the phase of the circumferential vibration and the radial vibration of the urging unit is reversed, and the movable element urged by the urging unit The feed direction is switched between the forward direction and the reverse direction.

In the ultrasonic motor of the present invention, as a more specific embodiment, the piezoelectric vibrator has a disk shape,
With one diameter of the circular main surface as the axis of symmetry,
The first selection drive electrode and the second selection drive electrode are arranged at symmetrical positions; and
The common drive electrode has a symmetrical shape;
The urging portion may be provided on the symmetry axis.

Further, in the ultrasonic motor of the present invention, as a more specific embodiment, the first selection drive electrode and the second selection drive electrode are arranged at point-symmetric positions with respect to the center of the main surface,
The urging portion may be provided on both sides of the center on the axis of symmetry.

  Note that the various components of the present invention do not have to be individually independent, that a plurality of components are formed as one member, and one component is formed of a plurality of members. It may be that a certain component is a part of another component, a part of a certain component overlaps a part of another component, and the like.

In the ultrasonic motor according to the present invention, the vibration direction of the urging portion provided on the outer periphery of the piezoelectric vibrator is reversed by the selection of the first or second selective drive electrode. The reverse switching is possible. In the present invention, the elastic modulus of the region of the piezoelectric vibrator can be effectively increased by the piezoelectric reaction by opening the selective drive electrode to which no alternating voltage is applied. For this reason, in the piezoelectric vibrator at the time of resonance, an asymmetric mode shape centering on the urging portion is realized, and the moving element can be suitably driven in the forward direction or the reverse direction.
In the present invention, the urging portion vibrates in the circumferential direction and the radial direction of the piezoelectric vibrator and vibrates with a larger displacement amount in the radial direction than in the circumferential direction. Sufficient urging force is given not only in the circumferential direction of the vibrator but also in the radial direction, and the driving force of the moving element can be obtained stably.

It is the schematic which shows the structure of the ultrasonic motor concerning 1st embodiment of this invention. It is a structural diagram of a piezoelectric ceramic plate. It is a figure which shows the example of a measurement of the frequency characteristic of the impedance between the common earth electrodes at the time of electrically connecting three of the four electrodes of a piezoelectric ceramic board. It is a displacement mode figure which shows the resonance state of the piezoelectric ceramic board obtained by the finite element analysis. It is a displacement mode figure which shows the resonance state of the piezoelectric ceramic board when the electrode of the area | region B is open | released. In the deformation | transformation figure of the points ah on the outer periphery of a piezoelectric ceramic board at the time of forming a common drive electrode in the area | regions B and C, and forming the 1st selection drive electrode and the 2nd selection drive electrode in the area | regions A and D, respectively. is there. It is a schematic diagram which shows the state which provided the urging | biasing part in the point e of the piezoelectric ceramic board of FIG. It is a schematic diagram which shows the state which provided the urging | biasing part in the point a of the piezoelectric ceramic board of FIG. In the deformation | transformation figure of the points ah on the outer periphery of a piezoelectric ceramic board at the time of forming a common drive electrode in area | region A and C, and forming the 1st selection drive electrode and the 2nd selection drive electrode in area | region B and D, respectively. is there. FIG. 10 is a schematic diagram illustrating a state in which a biasing portion is provided at a point f of the piezoelectric ceramic plate in FIG. FIG. 10 is a schematic diagram illustrating a state in which a biasing portion is provided at a point b of the piezoelectric ceramic plate in FIG. It is a figure which shows the deformation | transformation direction and deformation amount in the points ah on the outer periphery of the piezoelectric ceramic board which concerns on a comparison aspect with a line segment. It is the schematic which shows the structure of the ultrasonic motor concerning 2nd embodiment. It is the schematic which shows the structure of the ultrasonic motor concerning 3rd embodiment.

<First embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.
FIG. 1 is a schematic view showing the structure of an ultrasonic motor 10 according to the first embodiment of the present invention.
First, the outline | summary of the ultrasonic motor 10 of this embodiment is demonstrated.

The ultrasonic motor 10 includes a piezoelectric vibrator (piezoelectric ceramic plate 101), first and second selective drive electrodes 41c and 41d, common drive electrodes 41a and 41b, a ground electrode (common ground electrode 102), and a biasing unit. 103.
The piezoelectric ceramic plate 101 has a plate shape and is polarized in the thickness direction, and one main surface (main surface 30) is partitioned into a plurality of regions A, B, C, and D.
The first and second selective drive electrodes 41c and 41d and the common drive electrodes 41a and 41b are electrodes that are individually formed in the regions A, B, C, and D and to which an alternating voltage is applied.
The ground electrode (common ground electrode 102) is formed on the other main surface (main surface 31) of the piezoelectric ceramic plate 101.
The urging portion 103 is provided on the outer periphery of the piezoelectric ceramic plate 101.
In the ultrasonic motor 10, an alternating voltage is applied to one selected from the first or second selection drive electrodes 41c and 41d and the common drive electrodes 41a and 41b, and the second or first selection drive electrodes 41d and 41c are opened. As a result, the piezoelectric ceramic plate 101 resonates in the plane direction, and the urging portion 103 vibrates in the circumferential direction and radial direction of the piezoelectric ceramic plate 101 with a larger displacement in the radial direction than in the circumferential direction.
In the ultrasonic motor 10 of the present embodiment, the phase of the circumferential vibration and the radial vibration of the urging unit 103 is reversed by switching the selection of the first or second selection drive electrodes 41c and 41d. The feeding direction of the moving element 107 urged by the urging unit 103 is switched between the forward direction and the reverse direction.

  Here, the radial direction of the piezoelectric ceramic plate 101 means a direction connecting the vibration center of the piezoelectric ceramic plate 101 that resonates in the in-plane direction and a predetermined position. The circumferential direction of the piezoelectric ceramic plate 101 is a direction orthogonal to the radial direction. For example, when the piezoelectric ceramic plate 101 has a disk shape, the radial direction of the piezoelectric ceramic plate 101 is a radial direction, and the circumferential direction is a tangential direction. The same applies when the piezoelectric ceramic plate 101 has a non-circular shape such as a rectangle.

  In the present embodiment, the fact that the piezoelectric ceramic plate 101 is divided into regions means that the piezoelectric ceramic plate 101 includes a plurality of electrodes on its main surface 30. It is not always necessary that a section display for indicating each area is explicitly formed on 101 itself.

Next, the ultrasonic motor 10 of this embodiment will be described in detail.
The piezoelectric ceramic plate 101 of the present embodiment has a disk shape, and a circular hole 42 (see FIG. 2) having a predetermined diameter penetrating in the thickness direction is formed in the center. That is, the piezoelectric ceramic plate 101 of the present embodiment has an annular plate shape.

  The piezoelectric ceramic plate 101 may be a single plate or may be a laminated piezoelectric ceramic plate in which piezoelectric ceramic layers and electrode layers are alternately stacked. When the piezoelectric ceramic plate 101 is a laminated piezoelectric ceramic plate, every other electrode layer is divided into four like the regions A to D shown in FIG. 1 to drive electrodes (common drive electrodes 41a and 41b or selective drive electrodes 41c). , 41 d), and the other electrode layer is the common ground electrode 102. The drive electrodes stacked in the same region may be electrically connected to each other.

The regions A, B, C, and D have a fan shape formed by dividing the circular main surface 30 with a plurality of radii. Here, the central angles in the fan-shaped areas A to D may be equal to or different from each other. The fan shape referred to in this embodiment includes a fan shape having a central angle of 180 degrees, that is, a semicircular shape.
More specifically, the areas A, B, C, and D of the present embodiment are substantially fan-shaped by dividing the annular main surface 30 into four parts with mutually orthogonal diameters, and the central angle of each area Are each 90 degrees.

In the regions A, B, C, and D of the main surface 30, drive electrodes (divided electrodes) are deposited and formed individually in each region or across a plurality of regions.
In the ultrasonic motor 10 of this embodiment, electrodes 41a to 41d are formed on substantially the entire surface of each of the substantially fan-shaped regions. The electrodes 41a and 41c formed in the regions A and C are connected to each other, and are electrically separated from the electrodes 41b and 41d formed in the regions B and D, respectively.

Hereinafter, in the present embodiment, the electrode 41c is referred to as a first selection drive electrode, the electrode 41d is referred to as a second selection drive electrode, and the electrodes 41a and 41b are referred to as a common drive electrode.
That is, in the ultrasonic motor 10 of the present embodiment, the common drive electrodes 41a and 41b are formed in two of the regions A, B, C, and D, and the first and second selective drive electrodes 41c and 41d are , Regions A, B, C, and D, respectively. More specifically, the common drive electrodes 41a and 41b of the present embodiment are formed in two opposing regions A and C, and the first and second selective drive electrodes 41c and 41d are connected to the other two regions B. D is formed.

  One of the first selection drive electrode 41c and the second selection drive electrode 41d is selected, an alternating voltage is applied, and the other is opened. The common drive electrodes 41a and 41b are electrodes to which an alternating voltage is constantly applied.

A ground electrode is provided on the other main surface 31 of the piezoelectric ceramic plate 101. The ground electrode may be individually formed facing the electrodes 41a to 41d, or may be formed across two or more of the regions A to D. The ground electrode of the present embodiment is formed as a common ground electrode provided across the four regions A to D on the other main surface 31 of the piezoelectric ceramic plate 101.
Further, the common ground electrode 102 of the present embodiment is formed on almost the entire main surface 31.
In the present embodiment, an alternating voltage having a predetermined resonance frequency is provided between the one selected from the first selection drive electrode 41 c or the second selection drive electrode 41 d and the common drive electrodes 41 a and 41 b and the common ground electrode 102. Is applied. As a result, the piezoelectric ceramic plate 101 resonates in the planar direction (vertical and horizontal directions in FIG. 1).

  In the ultrasonic motor 10 according to the present embodiment, the first selection drive electrode 41c and the second selection drive electrode 41d are defined with one diameter of the circular main surface 30 of the disk-shaped piezoelectric ceramic plate 101 as the axis of symmetry AX. The common drive electrodes 41a and 41b are arranged symmetrically and have a symmetrical shape. The urging portion 103 is provided on the symmetry axis AX.

  In the case of this embodiment, the urging portion 103 is provided in the vicinity of the intersection of the bisector (symmetric axis AX) of the regions A and C where the common drive electrodes 41 a and 41 b are formed and the outer periphery of the piezoelectric ceramic plate 101. ing.

In the present embodiment, the first selection drive electrode 41c and the second selection drive electrode 41d are arranged at symmetrical positions with respect to the symmetry axis AX, and the common drive electrodes 41a and 41b are symmetrical. This means that when the electrodes are switched, the vibration direction of the urging unit 103 is practically reversed about the symmetry axis AX, and geometrically strict symmetry is not required.
Similarly, that the urging portion 103 is provided on the symmetry axis AX means that the symmetric portion AX passes through a part of the urging portion 103 in plan view, and that the oscillating direction of the urging portion 103 is reversed. As long as the feed direction of the moving element 107 can be switched practically, the biasing portion 103 is included in the vicinity of the symmetry axis AX.

In the present embodiment, the urging portion 103 provided on the outer periphery of the piezoelectric ceramic plate 101 and driving the moving element 107 is an element that applies a driving force to the moving element 107 by a frictional force.
The feeding direction of the moving element 107 by the urging unit 103 is not particularly limited, but in this embodiment, the circumferential direction of the piezoelectric ceramic plate 101 is the feeding direction.

The urging portion 103 of this embodiment is configured as a friction element provided on the outer peripheral surface of the piezoelectric ceramic plate 101.
Although the material of the urging | biasing part 103 is not specifically limited, Ceramic materials, such as an alumina, can be mentioned as an example. Alternatively, the urging portion 103 may be formed by roughening the outer peripheral surface of the piezoelectric ceramic plate 101. That is, the urging portion 103 may be manufactured as a separate member from the piezoelectric ceramic plate 101 or may be formed by processing the piezoelectric ceramic plate 101 itself.
More specifically, the biasing portion 103 of the present embodiment is provided by attaching an alumina pad-like friction element to a part of the outer peripheral surface of the annular plate-like piezoelectric ceramic plate 101. .

The moving element 107 is supported in a state in which it can freely move on the base 109 by a sliding mechanism 108 such as a roller.
The surface of the moving element 107 facing the piezoelectric ceramic plate 101 is roughened so as to frictionally engage the urging portion 103.
In the piezoelectric ceramic plate 101 of this embodiment shown in FIG. 1, a biasing portion 103 is provided in the vicinity of the center of the outer peripheral edge of the region C corresponding to the lower end thereof. The moving direction of the moving element 107 permitted by the sliding mechanism 108 is the left-right direction in FIG. 1 by setting the feeding direction of the urging portion 103 due to the resonance of the piezoelectric ceramic plate 101 to the circumferential direction of the piezoelectric ceramic plate 101. It becomes.

  Although FIG. 1 illustrates horizontal movement as the moving direction of the moving element 107, the present invention is not limited to this. By using the moving element 107 as a rotor and the sliding mechanism 108 as a rotating shaft of the moving element 107, the ultrasonic motor 10 of this embodiment operates as a drive device that rotates the moving element 107 as a rotor (FIGS. 7 and 8). See).

The ultrasonic motor 10 further includes a support portion (support tool 105) that supports the piezoelectric ceramic plate 101. In this embodiment, the support 105 is attached to the central circular hole 42 (see FIG. 2) of the piezoelectric ceramic plate 101, and the center of the main surface 30 of the piezoelectric ceramic plate 101 cannot be rotated and translated with respect to the space. It is rigidly fixed to.
The support 105 is formed of a resin material such as hard rubber having a Young's modulus lower than that of the piezoelectric ceramic plate 101 at least on the outer surface in contact with the piezoelectric ceramic plate 101. As a result, even when the inner diameter of the circular hole 42 at the center of the main surface 30 is enlarged or reduced when an alternating voltage is applied to elastically resonate the piezoelectric ceramic plate 101, the piezoelectric ceramic plate 101 is stably suppressed without suppressing vibration. The ceramic plate 101 can be supported.

The support 105 is connected to the base 109 via the elastic member 106. The urging portion 103 is pressed against the surface of the moving element 107 by receiving the urging force of the elastic member 106.
Thereby, the piezoelectric ceramic plate 101 resonates in a state where the urging portion 103 and the moving element 107 are always in contact.

Then, when the alternating voltage is applied and the piezoelectric ceramic plate 101 resonates, the urging portion 103 vibrates in the radial direction along with the circumferential direction of the piezoelectric ceramic plate 101, and a predetermined vertical drag against the surface of the moving element 107. Is pressed. The vertical drag from the urging unit 103 to the moving element 107 periodically varies according to the vibration mode of the piezoelectric ceramic plate 101. In this state, the urging portion 103 vibrates with a circumferential component of the piezoelectric ceramic plate 101, so that the moving element 107 is driven in the forward direction or the reverse direction.
Furthermore, when the selection of the first or second selection drive electrodes 41c and 41d is switched, the phase of the vibration in the circumferential direction and the vibration in the radial direction of the urging unit 103 are reversed. As a result, the feed direction of the moving element 107 is switched to the normal direction (left side in FIG. 1) or the reverse direction (the same direction, right direction) while maintaining the vertical drag on the moving element 107 at a predetermined level.

The switch SW1 switches the electrode to which the drive voltage is applied. The common terminal S0 of the switch SW1 is always connected to the output terminal 111 of the oscillator 110, and is electrically connected to the common drive electrodes 41a and 41b at the same time.
The terminal S1 is connected to the first selection drive electrode 41c, and the terminal S2 is connected to the second selection drive electrode 41d.

The power supply of the oscillator 110 is an alternating voltage of the internal resistance R0 and the output voltage V0, specifically a sine wave voltage. The frequency of the sine wave is set to the resonance frequency of the piezoelectric ceramic plate 101. That is, the ultrasonic motor 10 of this embodiment is a separately excited system to which a sine wave voltage having a frequency adjusted by the oscillator 110 is applied.
As shown in FIG. 1, when the switch SW1 is tilted toward the terminal S1, the drive voltage is applied to the common drive electrodes 41a and 41b and the first selection drive electrode 41c.
On the other hand, when the switch SW1 is tilted toward the terminal S2, the drive voltage is applied to the common drive electrodes 41a and 41b and the second selection drive electrode 41d.

  In the ultrasonic motor 10 of this embodiment, the total area of the first selection drive electrode 41c and the common drive electrodes 41a and 41b and the total area of the second selection drive electrode 41d and the common drive electrodes 41a and 41b are both main. It is greater than one half of the area of the surface 30. More specifically, these total areas are approximately three-quarters of the area of main surface 30.

  As will be described later, in the ultrasonic motor 10 of this embodiment, among the four regions A to D connected in a ring shape, any two regions are used as a common drive electrode, and the remaining two regions are selected drive electrodes. In this case, at least one axis of symmetry AX can be set. Then, by reversing the region to which the drive voltage is applied with respect to the symmetry axis AX, the mode shape of the resonating piezoelectric ceramic plate 101 is reversed with respect to the symmetry axis AX. Thereby, the feed direction of the moving element 107 urged by the urging unit 103 arranged on the symmetry axis AX is switched between the forward direction and the reverse direction.

<Operating principle>
Hereinafter, the resonance mode that occurs when a sine wave voltage is applied to the piezoelectric ceramic plate 101 of the present embodiment and the displacement of the outer periphery of the piezoelectric ceramic plate 101 will be described in detail.

FIG. 2 is a structural diagram of the piezoelectric ceramic plate 101 used in the ultrasonic motor 10 of this embodiment. 2A is a plan view of the piezoelectric ceramic plate 101, and FIG. 2B is a sectional view taken along line II-II in FIG.
As shown by the arrow in FIG. 2B, the annular plate-shaped piezoelectric ceramic plate 101 is polarized in the thickness direction, and a circular hole 42 is formed in the center of the main surface 30. The following description does not depend on the size of the inner diameter of the circular hole 42. That is, the thickness of the annular ring of the piezoelectric ceramic plate 101 is arbitrary, and the same operation principle will be explained even if the piezoelectric ceramic plate 101 is a solid disc shape.

The main surface 30 of the piezoelectric ceramic plate 101 is divided into four equal parts by two orthogonal diameters to form regions A to D, and electrodes 41a to 41d are provided on substantially the entire surface of each region. A common ground electrode 102 is formed on the entire other main surface 31 of the piezoelectric ceramic plate 101.
FIG. 2A illustrates the piezoelectric ceramic plate 101 at the boundary portion between the electrodes 41a to 41d and the central portion of the outer peripheral arc of the electrodes 41a to 41d in order to explain the deformation amount of the outer peripheral portion of the piezoelectric ceramic plate 101. For convenience, symbols a to h are attached to the positions of the points that divide the outer periphery of each into eight equal parts.
Then, three of the four divided electrodes are used as drive electrodes, the remaining one divided electrode is used as an open electrode, and an AC voltage having a predetermined frequency is applied between the common ground electrode 102.

  In FIG. 3, the piezoelectric ceramic plate 101 shown in FIG. 2 has dimensions of an outer diameter of 60 mm, an inner diameter of 20 mm, and a thickness of 3 mm, and three of the four electrodes 41a to 41d are electrically connected to face each other. It is a figure which shows the example of a measurement of the frequency characteristic of the impedance between the earth electrodes. FIG. 3 shows that the piezoelectric ceramic plate 101 of this embodiment resonates at 29.6 kHz. Hereinafter, the resonance frequency of the piezoelectric ceramic plate 101 is fr.

FIG. 4 is a displacement mode diagram showing the resonance state of the piezoelectric ceramic plate 101 obtained by finite element (FEM) analysis. This figure shows that the electrodes 41a, 41b and 41c formed in the regions A, B and C, respectively, of the main surface 30 of the piezoelectric ceramic plate 101 are electrically connected to each other as drive electrodes and formed in the remaining region D. The displacement mode of the piezoelectric ceramic plate 101 when the electrode 41d is opened is shown. The piezoelectric ceramic plate 101 resonates in the in-plane direction by applying an alternating voltage with a frequency fr between the drive electrode on the main surface 30 and the common ground electrode 102 on the other main surface 31.
FIG. 4 (a) shows the piezoelectric ceramic plate 101 during contraction deformation, and FIG. 4 (b) shows the expansion deformation. In the displacement mode diagrams shown in FIGS. 4A and 4B, a portion with a large amount of displacement is shown in dark color, and a portion with a small amount of displacement is shown in light color.
From FIGS. 7A and 7B, the resonance deformation of the piezoelectric ceramic plate 101 is asymmetrical with respect to the symmetry axis AX, and the deformation amount of the region D where the open electrode 41d is formed is particularly small. Recognize.

FIG. 5 shows a displacement indicating a resonance state of the piezoelectric ceramic plate 101 when the electrodes 41a, 41c and 41d formed in the regions A, C and D are used as drive electrodes and the electrode 41b formed in the region B is opened. FIG. 4 and 5, the conditions are the same except that the electrode to which the AC voltage is applied is changed from the electrode 41b to the electrode 41d. FIG. 5A shows the time of contraction deformation, and FIG. 5B shows the time of expansion deformation.
From FIGS. 9A and 9B, the resonance deformation of the piezoelectric ceramic plate 101 is asymmetrical with respect to the symmetry axis AX, and the deformation amount of the open electrode 41b formation region (region B) is particularly small. I understand that.

  Here, when FIG. 4 and FIG. 5 are compared, it can be seen that the deformed shapes of contraction and expansion are reversed with respect to the symmetry axis AX. Therefore, among the four electrodes 41a to 41d, the electrodes 41a and 41c are always used as a common drive electrode, and the drive voltage is always applied, and the drive voltage is applied only to one of the electrodes 41b and 41d selected as the selected drive electrode. By opening the other, it can be seen that the large displacement region in the piezoelectric ceramic plate 101 is reversed with respect to the symmetry axis AX.

  When this is utilized, the moving direction of the moving element 107 (see FIG. 1) in pressure contact with a specific position on the outer peripheral portion of the piezoelectric ceramic plate 101 is reversed by selectively switching the electrode to which the AC voltage is applied. It shows that you can.

Here, in order to realize the drive efficiency in the ultrasonic motor 10 satisfactorily, in addition to the large deformation amount of the urging portion 103, the deformation direction of the urging portion 103 and the tangential direction of the piezoelectric ceramic plate 101 are The angle formed is preferably 45 degrees or more and close to 45 degrees.
This is because the urging force applied from the urging unit 103 to the moving element 107 is applied according to the resonance period of the piezoelectric ceramic plate 101 in order to continuously apply the driving force to the moving element 107 by the urging unit 103. This is because it preferably varies periodically. Therefore, as a vibration mode of the piezoelectric ceramic plate 101, it is preferable that the vicinity of the urging portion 103 vibrates in the approaching and retracting directions with respect to the moving element 107 as well as the feeding direction of the moving element 107. For this reason, it is preferable that the deformation direction of the urging portion 103 intersects with the tangential direction of the piezoelectric ceramic plate 101 at approximately 45 degrees.

  As described above, in the ultrasonic motor 10 of this embodiment, not only the circumferential direction of the piezoelectric ceramic plate 101 corresponding to the feeding direction of the moving element 107 but also the radial direction of the piezoelectric ceramic plate 101 corresponding to the approaching direction to the moving element 107. In addition, the biasing portion 103 is deformed, and the displacement amount of the biasing portion 103 is larger in the radial direction than in the circumferential direction.

Further, in the ultrasonic motor 10 of the present embodiment, when the moving direction of the moving element 107 is reversed by switching the selection driving electrodes 41c and 41d to which the driving voltage is applied, the moving element 107 is moved in the direction opposite to the forward direction. It is preferable to make the movement speed uniform. For this purpose, when the selection drive electrodes 41c and 41d to which the drive voltage is applied are switched, the deformation amount of the urging portion 103 is the same, and the deformation direction of the urging portion 103 and the tangent line of the piezoelectric ceramic plate 101 are It is recommended that the sign of the angle is reversed.
Therefore, in the ultrasonic motor 10 of the present embodiment shown in FIG. 1, each of the selective drive electrodes 41c and 41d and the common drive electrodes 41a and 41b has one diameter of the annular plate-shaped piezoelectric ceramic plate 101 as the axis of symmetry AX. Are arranged symmetrically, and the urging portion 103 is provided on the symmetry axis AX. With this configuration, the deformation generated in the urging portion 103 when switching between application and release to the selective drive electrodes 41c and 41d is symmetric with respect to the symmetry axis AX, and the moving speed of the moving element 107 is equal in the forward direction and the reverse direction. It has become.

  Further, in the ultrasonic motor 10 of the present embodiment, the piezoelectric ceramic plate 101 is formed in a disc shape, and the moving element 107 is driven in the tangential direction of the piezoelectric ceramic plate 101 by an urging portion 103 provided on the outer periphery thereof. For this reason, even when the piezoelectric ceramic plate 101 resonates with a predetermined amplitude, the portion of the piezoelectric ceramic plate 101 other than the biasing portion 103 does not interfere with the moving element 107 because the piezoelectric ceramic plate 101 is circular.

  Moreover, in the ultrasonic motor 10 of this embodiment, since the drive voltage is applied to three of the regions that divide the piezoelectric ceramic plate 101 into four equal parts, the input impedance of the ultrasonic motor 10 is reduced. And good electro-mechanical conversion efficiency can be obtained.

  Hereinafter, displacement at points a to h on the outer periphery when the piezoelectric ceramic plate 101 shown in FIG. 2 is resonated at the frequency fr will be described.

6A and 6B, common drive electrodes 41a and 41b are formed in the regions B and C of the piezoelectric ceramic plate 101 shown in FIG. 2, and the first selection drive electrode 41c and the first drive electrode 41c are formed in the regions A and D, respectively. FIG. 6 is a modified view of points a to h on the outer periphery of the piezoelectric ceramic plate 101 when a two-select drive electrode 41d is formed. Each drawing of FIG. 6 illustrates a state in which the piezoelectric ceramic plate 101 of FIG. 2 is rotated 45 degrees clockwise.
The extending direction of the line segment indicated by each point a to h represents the deformation direction of the point a to h at the time of resonance of the piezoelectric ceramic plate 101, and the length of each line segment is the magnitude of the deformation of the point a to h. It shows.

As shown in FIGS. 6A and 6B, the piezoelectric ceramic plate 101 is configured symmetrically with respect to the symmetry axis AX in the regions A and B and the regions C and D. In other words, in the piezoelectric ceramic plate 101, the first selection drive electrode 41c and the second selection drive electrode 41d are switched symmetrically across the symmetry axis AX, and the common drive electrodes 41a and 41b sandwich the symmetry axis AX. It is formed symmetrically.
Hereinafter, the piezoelectric ceramic plate 101 shown in each drawing of FIG.

  In the same figure, among the areas A to D, the reference numerals of the areas to which the drive voltage is applied are circled. That is, FIG. 6A means a state in which a drive voltage is applied to the common drive electrodes 41a and 41b and the second selection drive electrode 41d, and FIG. 5B shows the common drive electrodes 41a and 41b and the first selection drive electrode 41d. This means that a drive voltage is applied to the drive electrode 41c.

  Table 1 below shows the relative deformation amount at each point a to h of the outer peripheral portion of the piezoelectric ceramic plate 101 shown in FIG. 6, the deformation direction at each point a to h, and the piezoelectric ceramic plate 101 at each point a to h. The angle formed with the outer peripheral edge (that is, the tangent line of the piezoelectric ceramic plate 101) is shown.

  From FIG. 6 and Table 1, the points a and e switch the selection drive electrodes 41c and 41d to which the drive voltage is applied and the angle between the deformation direction and the tangential direction of the piezoelectric ceramic plate 101 is 45 degrees or more. This is a point that satisfies the condition that the sign of the angle is reversed. Therefore, by providing the urging portion 103 at the point a or the point e, the movable element 107 (see FIG. 1) can be driven appropriately. From Table 1, it can be seen that the point a is most suitable as the installation position of the urging unit 103 from the viewpoint that the angle is close to 45 degrees.

7A and 7B, common drive electrodes 41a and 41b are formed in regions B and C, selective drive electrodes 41c and 41d are formed in regions A and D, and a piezoelectric ceramic plate is formed as in FIG. FIG. 10 is a schematic diagram showing a state in which an urging portion 103 (not shown in FIG. 7) is provided at a point e 101 and the moving element 107 is pressed against it.
FIGS. 8A and 8B are schematic views showing a state in which the urging portion 103 (not shown in FIG. 8) is provided at the point a of the piezoelectric ceramic plate 101 and the moving element 107 is pressed against the urging portion 103.
7A and 8A, the drive voltage is applied to the regions B, C, and D, and the drive voltage is applied to the regions A, B, and C in FIGS. 7B and 8B. is doing.

  7 and 8 exemplify a rotor as the moving element 107. The moving element 107 has a disk shape or a cylindrical shape in contact with the outer periphery of the piezoelectric ceramic plate 101, and a sliding mechanism 108 is attached to the shaft center and can be rotated in both directions around the axis.

In FIG. 7A in which a drive voltage is applied to the regions B, C, and D, the point e of the piezoelectric ceramic plate 101 vibrates from the radially inner left side toward the radially outer right side. For this reason, the rotation direction of the moving element 107 is clockwise in FIG.
On the other hand, in FIG. 7B in which a driving voltage is applied to the regions A, B, and C, the point e of the piezoelectric ceramic plate 101 vibrates from the radially inner right side toward the radially outer left side. For this reason, the rotation direction of the moving element 107 is counterclockwise in FIG.

8A and 8B in which the moving element 107 is pressed against the point a of the piezoelectric ceramic plate 101, the rotation direction of the moving element 107 is inverted upside down from the case of each figure in FIG.
Specifically, in FIG. 8A in which the drive voltage is applied to the regions B, C, and D, the point a of the piezoelectric ceramic plate 101 vibrates from the radially inner left side toward the radially outer right side. . For this reason, the rotation direction of the moving element 107 is counterclockwise in FIG.
On the other hand, in FIG. 8B in which the drive voltage is applied to the regions A, B, and C, the point a of the piezoelectric ceramic plate 101 vibrates from the radially inner right side to the radially outer left side. For this reason, the rotation direction of the moving element 107 is clockwise in FIG.

  As described above, in the piezoelectric ceramic plate 101 that is symmetric with respect to the symmetry axis AX (see FIG. 6), the urging portion 103 is selected by disposing it at the point a or point e on the outer periphery of the piezoelectric ceramic plate 101 and the symmetry axis AX. By switching the drive electrodes 41c and 41d, the moving element 107 can be driven at a moving speed equal to the forward and reverse directions.

  6 to 8 exemplify a mode in which the first and second selective drive electrodes 41c and 41d are formed in the adjacent regions A and D, but the present invention is not limited to this.

9 shows the piezoelectric ceramic plate 101 when the common drive electrodes 41a and 41b are formed in the regions A and C, and the first selection drive electrode 41c and the second selection drive electrode 41d are formed in the regions B and D, respectively. It is a deformation | transformation figure of the points ah on the outer periphery.
That is, unlike the piezoelectric ceramic plate 101 shown in FIGS. 6A and 6B, the selective driving electrodes 41c and 41d are formed in regions facing each other in the piezoelectric ceramic plate 101 of FIG.
Hereinafter, the mode of the piezoelectric ceramic plate 101 shown in each drawing of FIG. 9 is referred to as a second mode.

  FIG. 9A shows a state in which a drive voltage is applied to the second selection drive electrode 41d together with the common drive electrodes 41a and 41b, and the first selection drive electrode 41c is opened, and FIG. 9B shows the common drive electrode 41c. The drive voltage is applied to the first selection drive electrode 41c together with 41a and 41b, and the second selection drive electrode 41d is opened.

  The following Table 2 shows the relative deformation amount at each point a to h of the outer peripheral portion of the piezoelectric ceramic plate 101 and the deformation direction at each point a to h and the outer peripheral edge of the piezoelectric ceramic plate 101 as in Table 1. The angle to make is shown.

  Here, also in the case of FIG. 9, the piezoelectric ceramic plate 101 is configured symmetrically with respect to the symmetry axis AX. When the selective drive electrodes 41c and 41d are formed in regions (regions B and D) facing each other across the center of the piezoelectric ceramic plate 101 as shown in FIG. 9, the drive voltage application region is changed by switching the selective drive electrodes 41c and 41d. The axis of symmetry AX serving as a reference for reversal is a diameter passing through the centers of the regions A and C.

  9 and Table 2, in this case, the point b and the point f have an angle formed by the deformation direction and the tangential direction of the piezoelectric ceramic plate 101 of 45 degrees or more, and the selection drive electrodes 41c, This is a point that satisfies the condition that the sign of the angle is reversed when 41d is switched.

10A and 10B, common drive electrodes 41a and 41b are formed in regions A and C, selective drive electrodes 41c and 41d are formed in regions B and D, and a piezoelectric ceramic plate is formed as in FIG. FIG. 10 is a schematic diagram showing a state where an urging portion 103 (not shown in FIG. 10) is provided at a point f 101 and the moving element 107 is pressed against this.
FIGS. 11A and 11B are schematic views showing a state in which the urging portion 103 (not shown in FIG. 11) is provided at the point b of the piezoelectric ceramic plate 101 and the moving element 107 is in pressure contact therewith.
10 (a) and 11 (a), a drive voltage is applied to the regions A, C, and D, and in FIGS. 10 (b) and 11 (b), a drive voltage is applied to the regions A, B, and C. is doing.

  10 and 11 exemplify a slider that moves horizontally on a flat base 109 as the moving element 107. The moving element 107 can be translated in the left-right direction in each figure by a sliding mechanism 108. The configurations of the piezoelectric ceramic plate 101 and the mover 107 shown in FIG. 10 correspond to the ultrasonic motor 10 shown in FIG.

As indicated by arrows in FIG. 10, when a drive voltage is applied to the regions A, C, and D, the urging unit 103 (not shown in the figure) provided at the point f Drive linearly. On the other hand, when a driving voltage is applied to the regions A, B, and C, the urging unit 103 provided at the point f linearly drives the moving element 107 to the left in the drawing.
The same applies to FIG. 11, and when a drive voltage is applied to the regions A, C, and D, the urging unit 103 (not shown in the figure) provided at the point b causes the moving element 107 to move to the right in the figure. Drive linearly. On the other hand, when a driving voltage is applied to the regions A, B, and C, the urging unit 103 provided at the point b linearly drives the moving element 107 to the left in the drawing.

  Further, unlike the relationship between the points a and e shown in Table 1 and FIG. 6, the displacement amounts and angles at the points b and f shown in Table 2 and FIG. 9 are equal to each other. Therefore, as will be described later with reference to FIG. 14, in the case of the piezoelectric ceramic plate 101 shown in FIGS. 9 to 11, the urging portions 103 are respectively provided at two opposing points (point b and point f) of the piezoelectric ceramic plate 101. Thus, a linear ultrasonic motor that linearly drives the movable element 107 at two points can be realized.

  Here, for comparison with the ultrasonic motor 10 of the present embodiment, a modified view when the piezoelectric ceramic plate is resonated by applying a driving voltage to a half region of the main surface of the piezoelectric ceramic plate. Is shown in FIGS. 12 (a) and 12 (b).

  FIG. 12 shows each of the points a˜ on the outer periphery based on the result of FEM analysis of the piezoelectric ceramic plate 101 in which the common drive electrode is formed in the region A, the selective drive electrodes are formed in the regions B and D, and the region C is always open. The deformation direction and deformation amount at h are illustrated by line segments.

  The following Table 3 shows the relative deformation amount at each point a to h of the outer peripheral portion of the piezoelectric ceramic plate 101 and the deformation direction at each point a to h and the outer peripheral edge of the piezoelectric ceramic plate 101 as in Tables 1 and 2. The angle formed by is shown.

Hereinafter, the mode in which the moving element is driven using the deformation of the point b in the piezoelectric ceramic plate 101 shown in FIGS. 12A and 12B is referred to as a first comparative mode.
In addition, a mode in which the moving element is driven using the deformation at the point c in the piezoelectric ceramic plate 101 shown in FIGS. 12A and 12B is referred to as a second comparative mode.

The results of the first and second comparative modes shown in FIG. 12 and Table 3 are compared with the results of the first mode (FIGS. 6 and 1) and the second mode (FIGS. 9 and 2) of the present embodiment.
First, in the case of the first comparison mode, the deformation (0.34: Table 3) at the point b corresponding to the drive point is the position (point a or point e) of the urging portion 103 in the first mode of the present embodiment. About half of the amount of deformation (0.63 or 0.75: Table 1) and the amount of deformation (0.73: Table 2) at the position of the biasing portion 103 (point b or point f) in the second mode It is. For this reason, in the motor of a 1st comparison aspect, the drive speed of a slider cannot be obtained equivalent to the ultrasonic motor 10 concerning the 1st or 2nd aspect of this embodiment.
Further, since the angle formed by the deformation direction at the point b shown in Table 3 and the tangential direction of the piezoelectric ceramic plate 101 is less than 45 degrees (19 degrees), when the urging portion and the moving element are arranged at the point b, The urging unit cannot sufficiently obtain an approach direction component from the urging unit toward the moving element.

  The same applies to the motor of the second comparison mode. The deformation amount (0.46: Table 3) at the point c corresponding to the driving point of the moving element is smaller than the deformation amount at the position of the urging portion 103 in the first or second aspect of the present embodiment, and the point c. The angle at is 0 degrees. Therefore, the motor of the second comparison mode also cannot obtain a sufficient driving speed of the moving element and cannot stably drive the moving element as compared with the ultrasonic motor 10 of the present embodiment.

  On the other hand, in the ultrasonic motor 10 of the present embodiment, as drive electrodes, common drive electrodes 41a and 41b to which an alternating voltage is always applied, and selective drive electrodes 41c and 41d to which an alternating voltage is selectively applied, Is included. As a result, an alternating voltage can be applied to the main surface 30 of the piezoelectric ceramic plate 101 with respect to an area of about 3/4, so that a large piezoelectric deformation can be caused in the piezoelectric ceramic plate 101.

<Second embodiment>
FIG. 13 is a schematic diagram showing the configuration of another embodiment of the ultrasonic motor of the present invention.
The ultrasonic motor 10 of this embodiment drives the moving element 107 using the piezoelectric ceramic plate 101 according to the first aspect shown in FIGS. 7 (a) and 7 (b).

That is, in the ultrasonic motor 10 of the present embodiment, the piezoelectric ceramic plate 101 has an annular plate shape, and the regions A, B, C, and D are divided into two annular main surfaces 30 with two orthogonal diameters. It has a general fan shape. The common drive electrodes 41a and 41b are formed in two adjacent regions B and C, and the first and second selective drive electrodes 41c and 41d are formed in the other two regions A and D, respectively. A common ground electrode 102 is provided on the other main surface (not shown) of the piezoelectric ceramic plate 101.
The biasing portion 103 is provided in the vicinity of the intersection between the boundary line between the two regions B and C where the common drive electrodes 41 a and 41 b are formed and the outer periphery of the piezoelectric ceramic plate 101.
The mover 107, the support 105, the elastic member 106, and the sliding mechanism 108 placed on the base 109 are the same as those in the first embodiment shown in FIG.

In FIG. 13, a switch SW2 is for switching electrodes for applying a driving voltage of two circuits and four contacts, and the common terminal S00 of the first circuit C1 is always connected to the output terminal 113 of the feedback oscillator (amplifier) 112. At the same time, they are connected to the common drive electrodes 41a and 41b. Here, the common drive electrodes 41 a and 41 b are electrically connected to each other by an electrode pattern on the piezoelectric ceramic plate 101.
The selective drive electrodes 41c and 41d are insulated from each other.

The terminal S01 is connected to the first selection drive electrode 41c, and the terminal S02 is connected to the second selection drive electrode 41d. The input terminal 114 of the feedback oscillator 112 is connected to the common terminal S10 of the second circuit C2 of the switch SW2.
The terminal S11 is provided between resistors R11 and R12 connected between the second selection drive electrode 41d and the ground terminal 115. The terminal S12 is provided between resistors R21 and R22 connected between the first selection drive electrode 41c and the ground terminal 116.
The oscillation frequency of the feedback oscillator 112 is set to the frequency fr.

  Here, the values of the series resistances of the resistors R11 and R12 and the series resistances of the resistors R21 and R22 are high resistances that effectively open the first or second selection drive electrodes 41c and 41d to which no drive voltage is applied. Value. Note that the values of the voltage dividing resistors R12 and R22 can be appropriately selected so that an appropriate voltage is fed back to the feedback oscillator 112.

  In this state, when the switch SW2 is tilted upward, the drive voltage is applied to the common drive electrodes 41a and 41b and the first selection drive electrode 41c, and the regions A, B, and C of the piezoelectric ceramic plate 101 are energized. Therefore, as shown in FIG. 7B, the vicinity of the boundary between the regions B and C (the point e in the figure) is deformed in the circumferential direction and the radial direction of the piezoelectric ceramic plate 101, and thus formed in the same part. The moving element 107 protrudes to the left in FIG. 13 by the urging unit 103 and moves to the left.

On the other hand, when the switch SW2 is tilted downward, the drive voltage is applied to the regions B, C, and D, so that the vicinity of the boundary between the regions B and C is deformed as shown in FIG. The moving element 107 is protruded rightward in FIG. 13 by the urging portion 103 formed in the same portion and moves rightward.
That is, the moving element 107 can be selectively moved in the left-right direction simply by switching the switch SW2.

Here, the first or second selective drive electrodes 41c and 41d to which no alternating voltage (drive voltage) is applied are opened. In the ultrasonic motor 10 of the present embodiment, the opened selective driving electrode is used as a feedback electrode for the self-excited oscillation circuit.
Thus, even when the resonance frequency changes due to a change in the mechanical load state or a change in the ambient temperature, the resonance frequency is automatically tracked, so that a stable drive circuit can be configured.

<Third embodiment>
FIG. 14 is a schematic diagram showing the configuration of another embodiment of the ultrasonic motor of the present invention.
The ultrasonic motor 10 of the present embodiment has a linear guide type structure configured by utilizing two deformations that occur in the piezoelectric ceramic plate 101. In the figure, a drive circuit for applying a drive voltage to the piezoelectric ceramic plate 101 is not shown.

  In the ultrasonic motor 10 of the present embodiment, the regions A to D are substantially fan-shaped by dividing the annular main surface 30 into four parts with mutually perpendicular diameters, as in the respective drawings in FIG. Common drive electrodes 41a and 41b are formed in C, and first and second selective drive electrodes 41c and 41d are formed in regions B and D, respectively.

  Further, in the ultrasonic motor 10 of the present embodiment, the first selection drive electrode 41c and the second selection drive electrode 41d are disposed at point-symmetrical positions with respect to the center CP of the main surface 30, and the biasing portion 103 is the piezoelectric ceramic plate 101. Are provided opposite to both sides of the outer periphery of the outer periphery of the optical axis on the symmetry axis AX and sandwiching the center CP.

  Specifically, urging portions 103 (the urging portions 103 in the region C are not shown) are provided at the centers of the outer peripheral edges of the regions A and C, respectively.

On the other hand, the moving element 107 driven by the ultrasonic motor 10 according to the present embodiment includes a substrate 121 and a pair of parallel standing plates 122 and 123 that are erected on the substrate 121 and sandwich the piezoelectric ceramic plate 101. Yes. That is, as shown in FIG. 14, the moving element 107 is a member having an upper opening and a U-shaped cross section.
The movable element 107 is provided with an elastic plate 124 on the inner side of the opposed standing plates 122 and 123 and a friction plate 125 on the inner side. The facing interval between the friction plates 125 is slightly smaller than the distance between the outer edges of the urging portion 103.
That is, the piezoelectric ceramic plate 101 is sandwiched between the opposing friction plates 125 with a predetermined pressing force.

  The substrate 121 is formed with an oval hole 126 penetrating through the center. The major axis direction of the hole 126 coincides with the extending direction of the opposing friction plate 125. Hereinafter, the major axis direction of the hole 126 is referred to as the longitudinal direction of the moving element 107, and the interval direction of the friction plates 125 facing each other is referred to as the width direction of the moving element 107.

The support 105 of the piezoelectric ceramic plate 101 has a rod shape, passes through the center CP of the piezoelectric ceramic plate 101, protrudes downward in the direction perpendicular to the surface of the piezoelectric ceramic plate 101, and is inserted into the hole 126.
The inner diameter of the hole 126 in the minor axis direction is slightly larger than the shaft diameter of the support tool 105.

The base guide 130 is a rail member that holds the movable element 107 so as to be slidable in the longitudinal direction. The substrate 121 of the moving element 107 is fitted in the groove 131 of the base guide 130 so as to be slidable in the longitudinal direction.
The lower end of the support 105 of the piezoelectric ceramic plate 101 is fixed to the bottom surface 132 of the groove 131.

  When an alternating voltage having a frequency fr is applied as a drive voltage to one of the piezoelectric ceramic plate 101 selected from the first or second selective drive electrodes 41c and 41d and the common drive electrodes 41a and 41b, the piezoelectric ceramic plate 101 resonates as shown in FIGS.

As a result, as shown in Table 2, at the point b and point f where the urging portion 103 is provided in the piezoelectric ceramic plate 101, the same angle and the same amount of deformation that causes the mover 107 to move in the same direction occurs. .
Here, since the elastic plate 124 attached to the moving element 107 is configured to always press the friction plate 125 against the piezoelectric ceramic plate 101, it is provided at the center of the partial arcs of the areas A and C of the piezoelectric ceramic plate 101. The urging portion 103 is engaged with a predetermined frictional force.
The moving element 107 is driven on the base guide 130 by receiving a frictional force in the longitudinal direction by the elastic deformation of the urging portion 103 generated by the application of the driving voltage.
Further, by switching the selection of the first or second selection drive electrodes 41c and 41d to which the drive voltage is applied, the vibration direction of the urging unit 103 is reversed in the longitudinal direction, and the feed direction of the moving element 107 is switched between forward and reverse. It is done.

The present invention is not limited to the above-described embodiments, and includes various modifications and improvements as long as the object of the present invention is achieved.
In the said embodiment, although the piezoelectric ceramic board 101 is made into disk shape and this is divided into four area | regions AD by two diameters, this invention is not limited to this.

  For example, FIGS. 4 and 5 show vibration mode diagrams in the case where the piezoelectric ceramic plate 101 has a disc shape (annular plate shape), but the piezoelectric ceramic plate 101 has a geometrically strict disc shape. In addition, if it is substantially disk-shaped, the moving element 107 can be driven using the same vibration mode. That is, in this embodiment, the piezoelectric ceramic plate 101 is disc-shaped as long as the movable element 107 can be practically switched in the forward and reverse directions as in the above embodiment, for example, a part of the disc. This includes a case where the shape is substantially disc-shaped, such as a shape obtained by deleting or a shape in which corners or other parts are partially added to the disc.

Moreover, although the biasing part 103 and the moving element 107 have always been described in the above embodiment, the present invention is not limited to this. For example, the urging unit 103 and the moving element 107 may be temporarily separated in the resonance period of the piezoelectric ceramic plate 101.
Further, the urging unit 103 may urge the moving element 107 when the piezoelectric ceramic plate 101 is expanded in the resonance period of the piezoelectric ceramic plate 101 or urge the moving element 107 when the piezoelectric ceramic plate 101 is reduced in diameter. May be.

  Moreover, although the embodiment and the modification have described the aspect in which the urging portion 103 is provided only on the symmetry axis AX, the present invention is not limited to this. For example, in addition to the axis of symmetry AX, the urging unit 103 may be further provided in other parts.

  Further, when the main surface 30 of the piezoelectric ceramic plate 101 is divided into a plurality of regions, the area of each region may be equal or different from each other. In addition, the shape of each region may be the same as or different from each other with respect to the plurality of regions.

  Furthermore, the drive circuits shown in FIGS. 1 and 13 are merely examples, and similar functions can be satisfied by various circuit configurations such as a digital signal processing circuit.

The above-described embodiments of the present invention and modifications thereof include the following technical ideas.
(1) A plate-like piezoelectric vibrator that is polarized in the thickness direction and has one main surface partitioned into a plurality of regions, and an alternating voltage that is individually formed in the region and applied with an alternating voltage. A selection drive electrode and a common drive electrode, a ground electrode formed on the other main surface of the piezoelectric vibrator, and an urging portion provided on an outer periphery of the piezoelectric vibrator, the first or second By applying the alternating voltage between one selected from the selection drive electrodes and the common drive electrode and the ground electrode, and opening the second or first selection drive electrode, the piezoelectric vibrator is in a plane direction The biasing portion vibrates in a circumferential direction and a radial direction of the piezoelectric vibrator with a larger displacement in the radial direction than in the circumferential direction, and the first or second selective drive electrode By switching the selection of Circumferential direction vibration and the phase is inverted vibration in the radial direction of the ultrasonic motor feeding direction of the moving element which is biased in the urging portion is characterized in that it is switched to the forward or reverse direction;
(2) The piezoelectric vibrator has a disk shape, the first selection drive electrode and the second selection drive electrode are arranged at symmetrical positions with one diameter of the circular main surface as an axis of symmetry, and The ultrasonic motor, wherein the common drive electrode has a symmetrical shape, and the urging portion is provided on the symmetry axis;
(3) The first selection drive electrode and the second selection drive electrode are arranged at point-symmetrical positions with respect to the center of the main surface, and the biasing portion is on the symmetry axis and sandwiches the center The ultrasonic motor described above, wherein the ultrasonic motor is provided opposite to the motor;
(4) The ultrasonic motor according to any one of the above, wherein the urging unit applies a driving force to the moving element by a frictional force, and the moving direction of the moving element is the circumferential direction of the piezoelectric vibrator;
(5) The total area of the first selection drive electrode and the common drive electrode and the total area of the second selection drive electrode and the common drive electrode are both greater than one half of the area of the main surface. Any one of the above-described ultrasonic motors;
(6) The ultrasonic motor according to any one of the above, wherein the piezoelectric vibrator has a disk shape and the region has a fan shape formed by dividing the circular main surface with a plurality of radii.
(7) The piezoelectric vibrator has a disk shape, and the region has a fan shape formed by dividing the main surface of the circle into four parts with mutually orthogonal diameters, and the common drive is performed in two of the regions. Any one of the above ultrasonic motors in which an electrode is formed and the first and second selective drive electrodes are formed in each one of the regions;
(8) The piezoelectric vibrator has an annular plate shape, and the region has a substantially fan shape formed by dividing the annular main surface into four parts with mutually orthogonal diameters, and the two adjacent regions. The common drive electrode is formed on the other two regions, and the first and second selective drive electrodes are formed on the other two regions, respectively, and the ground electrode is formed on the four other main surfaces of the piezoelectric vibrator. A common earth electrode provided over a region, and the biasing portion is provided in the vicinity of an intersection between a boundary line between the two regions where the common drive electrode is formed and the outer periphery of the piezoelectric vibrator, Any one of the above-described ultrasonic motors, wherein the alternating voltage is applied between one selected from the first or second selection drive electrode and the common drive electrode and the common ground electrode;
(9) The piezoelectric vibrator has an annular plate shape, and the region has a substantially fan shape formed by dividing the annular main surface into four parts with mutually perpendicular diameters, and the two regions facing each other. The common drive electrode is formed on the other two regions, and the first and second selective drive electrodes are formed on the other two regions, respectively, and the ground electrode is formed on the four other main surfaces of the piezoelectric vibrator. A common earth electrode provided across a region, wherein the biasing portion is provided in the vicinity of an intersection of a bisector of the region where the common drive electrode is formed and the outer periphery of the piezoelectric vibrator, Any one of the above-described ultrasonic motors, wherein the alternating voltage is applied between one selected from the first or second selection drive electrode and the common drive electrode and the common ground electrode.

DESCRIPTION OF SYMBOLS 10 Ultrasonic motor 30,31 Main surface 41a, 41b, 41e Common drive electrode 41c, 41f 1st selection drive electrode 41d, 41g 2nd selection drive electrode 42 Circular hole 101 Piezoelectric ceramic board 102 Common earth electrode 103 Energizing part 105 Support Tool 106 Elastic member 107 Moving element 108 Sliding mechanism 109 Base 110 Oscillator 111, 113 Output terminal 112 Feedback oscillator (amplifier)
114 Input terminal 115, 116 Ground terminal 121 Substrate 122, 123 Standing plate 124 Elastic plate 125 Friction plate 126 Hole 130 Base guide 131 Concave groove 132 Bottom surface A to D, E to G Region AX Symmetry axis CP Center SW1, SW2 switch

Claims (3)

A plate-like piezoelectric vibrator polarized in the thickness direction and having one main surface partitioned into a plurality of regions;
First and second selective drive electrodes and common drive electrodes, which are individually formed in the region and applied with an alternating voltage;
An earth electrode formed on the other main surface of the piezoelectric vibrator;
An urging portion provided on an outer periphery of the piezoelectric vibrator,
Applying the alternating voltage between one selected from the first or second selection drive electrode and the common drive electrode and the ground electrode, and opening the second or first selection drive electrode, The piezoelectric vibrator resonates in a plane direction, and the biasing portion vibrates in a circumferential direction and a radial direction of the piezoelectric vibrator with a larger displacement in the radial direction than in the circumferential direction; and
By switching the selection of the first or second selection drive electrode, the phase of the circumferential vibration and the radial vibration of the urging unit is reversed, and the movable element urged by the urging unit The ultrasonic motor is characterized in that the feed direction is switched between the forward direction and the reverse direction. The piezoelectric vibrator has a disk shape,
With one diameter of the circular main surface as the axis of symmetry,
The first selection drive electrode and the second selection drive electrode are arranged at symmetrical positions; and
The common drive electrode has a symmetrical shape;
The ultrasonic motor according to claim 1, wherein the biasing portion is provided on the axis of symmetry. The first selection drive electrode and the second selection drive electrode are arranged in a point-symmetrical position with respect to the center of the main surface,
The ultrasonic motor according to claim 2, wherein the urging portion is provided opposite to both sides of the symmetric axis and sandwiching the center.

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