JP2010158143A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor, capable of driving a moving a member in the forward and the reverse direction on an AC voltage of single phase, at a high driving efficiency. <P>SOLUTION: In a piezoelectric ceramic square plate 101 of an ultrasonic motor 10, the mode shape due to resonance is asymmetric at a first corner 23 and a second corner 24. By having an AC voltage applied between any one of split electrodes 41a-41d formed on one main surface 30 of the piezoelectric ceramic square plate 101 and a common grounding electrode 102 of the other main surface 35, the corner where a maximum displacement occurs due to resonance is switched between the first corner 23 and the second corner 24. Then a frictional element 103 for driving the moving member 107 in the forward direction and a frictional element 104 for driving the moving member 107 in reverse direction are provided respectively to the first corner 23 and the second corner 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor that drives a moving element using a piezoelectric vibrator.

Recently, a small ultrasonic motor is widely used for driving a lens for camera autofocus and 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.

In Patent Document 1 (see FIG. 3 in particular), electrodes that divide one surface of a piezoelectric ceramic rectangular plate polarized in the thickness direction into four equal parts in a rectangular array are formed at diagonal positions. An ultrasonic motor is disclosed in which electrodes are electrically connected to form a drive electrode and the other surface is provided with a full-surface electrode.
The piezoelectric ceramic rectangular plate is selected to have a width dimension and a length dimension that substantially match the resonance frequency of the primary resonance mode of longitudinal vibration in the longitudinal direction and the resonance frequency of the secondary resonance mode of in-plane width direction bending vibration.

In the present invention, a first sine wave voltage equal to the resonance frequency is applied between one drive electrode and the common ground electrode, and a first sine wave voltage is applied between the other drive electrode and the common ground electrode. A second sine wave voltage having a phase difference of 90 degrees is applied. Then, the longitudinal vibration in the length direction and the bending vibration in the width direction of the piezoelectric ceramic rectangular plate are generated at the same time, and as a synthesis, elliptical vibration is generated in the central portion of both short sides of the piezoelectric ceramic rectangular plate, The mover that presses the protrusion formed on is moved in the short side direction of the piezoelectric ceramic rectangular plate.
By changing the phase of the drive voltage and one of the drive voltages by 180 degrees, or by switching the electrode to which the drive voltage is applied, the direction of the elliptical vibration generated in the protrusion is reversed, and as a result, the movement of the slider The direction can be reversed.

  However, in the conventional ultrasonic motor disclosed in Patent Document 1 below, since the driving force is applied to the moving element using elliptical vibration, it is necessary to match the resonance frequencies of two orthogonal vibration modes with high accuracy. There is a problem that high-precision processing is required and manufacturing is difficult. Further, in the case of such a conventional ultrasonic motor, since the longitudinal vibration and the transverse vibration are used as vibration modes, the temperature characteristics of the resonance frequency are different, and a difference occurs in these resonance frequencies due to changes in the ambient temperature. There is a problem that the characteristics of the ultrasonic motor deteriorate.

Further, in Patent Document 2 below, a rectangular piezoelectric plate is divided into two identical parts by a section screen extending in the vertical direction, and an asymmetric two-dimensional standing wave is generated on one of the two parts to generate a piezoelectric film. An ultrasonic motor is described in which kinetic energy is transmitted to the mover by a friction element located in the center of the long end face of the plate.
Since this invention is a system in which a single-phase sine wave is applied to a piezoelectric plate and driven using a single resonance frequency, the characteristics of the ultrasonic motor do not deteriorate due to changes in ambient temperature.

Japanese Patent Laid-Open No. 05-3688 Special table 2007-538484 gazette

  However, in the invention described in Patent Document 2, in order to obtain a driving force that can be switched between the normal direction and the reverse direction by an asymmetric two-dimensional standing wave of a piezoelectric plate that is divided into left and right by a section screen. It is essential to place the friction element at the center of the long side. This is because, as shown in FIG. 6 of the same document, when attention is paid only to the divided portion (active side) on one side of the section screen, the resonance mode is a simple surface expansion / contraction vibration. This is because the driving force capable of switching between the forward direction and the reverse direction is generated at the center of the long side corresponding to the boundary portion by using the rigidity of the divided portion on the passive side. Therefore, in the above invention, the displacement at the center of the long side cannot be obtained by the restraining force due to the rigidity on the passive side, and it is difficult to secure a sufficient stroke of the friction element. There was a problem with efficiency.

  The present invention has been made in view of the problems of the conventional ultrasonic motor described above, and is capable of driving the moving element in the forward and reverse directions by a single-phase alternating voltage and obtaining high driving efficiency. It is an object of the present invention to provide an ultrasonic motor.

The ultrasonic motor according to the present invention includes a movable body that is elastically resonated by applying an alternating voltage to a piezoelectric vibrator that is polarized in the thickness direction and has a plate shape having at least a first corner portion and a second corner portion. An ultrasonic motor that drives the motor in the forward and reverse directions,
In the piezoelectric vibrator, a mode shape by the resonance is asymmetric between the first corner portion and the second corner portion,
In the piezoelectric vibrator, one main surface is divided into a plurality of regions, drive electrodes are individually formed in the regions, and a ground electrode is formed on the other main surface.
When the alternating voltage is applied between any one of the plurality of drive electrodes selected from the plurality and the ground electrode, the corner portion causing the maximum displacement due to the resonance is the first corner portion or the second corner portion. As well as
A first urging portion that drives the moving element in the forward direction and a second urging portion that drives the moving element in the reverse direction are provided in the first corner portion and the second corner portion, respectively. It is characterized by that.

  In the ultrasonic motor of the present invention, as a more specific embodiment, the drive electrode includes a common drive electrode to which the alternating voltage is constantly applied, and a selective drive electrode to which the alternating voltage is selectively applied. And may be included.

  Further, in the ultrasonic motor of the present invention, as a more specific embodiment, the selective drive electrodes are respectively formed in a region where the first corner portion is formed and a region where the second corner portion is formed. May be.

  The common drive electrode may be formed in a region where the first corner portion is formed and a region where the second corner portion is formed.

  In the ultrasonic motor of the present invention, as a more specific embodiment, the one main surface is divided into four regions divided by a straight line parallel to the side of the rectangular piezoelectric vibrator. The common drive electrode or the selective drive electrode may be formed in each of the regions.

  In the ultrasonic motor of the present invention, as one more specific embodiment, the one main surface is divided into four regions by two diagonal lines of the rectangular piezoelectric vibrator, and is adjacent to the region. The common drive electrodes and the selective drive electrodes may be alternately arranged in the matching regions.

Moreover, in the ultrasonic motor of the present invention, as a more specific embodiment, the first urging portion is provided in two first corner portions sandwiching one of the selection drive electrodes,
The second urging portion may be provided in the two second corner portions sandwiching the other selective drive electrode.

In the ultrasonic motor of the present invention, as a more specific embodiment, the piezoelectric vibrator has a rectangular shape, the first corner portion and the second corner portion adjacent to each other, and the other two Including corners,
The one selective drive electrode for driving the first urging portion is formed in a region different from the region in which the first corner portion is formed,
The other selective drive electrode for driving the second urging portion may be formed in a region different from the region in which the second corner portion is formed.

  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 of the present invention, the corner portion that causes the maximum displacement due to the resonance of the piezoelectric vibrator is switched by the selection of the drive electrode. Therefore, it is possible to provide an ultrasonic motor that does not have a problem of deterioration of characteristics due to temperature changes.
Furthermore, in the ultrasonic motor of the present invention, the urging portion for driving the moving element is provided at the corner portion where the maximum displacement due to resonance occurs, so that the stroke of the urging portion is sufficiently ensured and high driving efficiency is achieved. Obtainable.

It is the schematic which shows the structure of the ultrasonic motor concerning 1st embodiment of this invention. It is a structural diagram of the piezoelectric ceramic square plate of the first embodiment. It is a figure which shows an example of the simulation result regarding the frequency characteristic of the impedance between the common earth electrodes when three of the four divided electrodes of the piezoelectric ceramic square plate are electrically connected. It is a displacement mode figure of the piezoelectric ceramic square board obtained by FEM analysis at the time of impressing sine wave voltage of frequency fr1 between division electrodes 41a, 41c, and 41d, and a common earth electrode. It is a displacement mode figure of a piezoelectric ceramic square board obtained by FEM analysis when a sine wave voltage with a frequency of fr2 is applied between divided electrodes 41a, 41c and 41d and a common earth electrode. It is explanatory drawing of the operation principle of the ultrasonic motor of this invention. It is the schematic which shows the structure of the ultrasonic motor concerning 2nd embodiment of this invention. It is the schematic which shows the structure of the ultrasonic motor concerning 3rd embodiment of this invention. It is a structural diagram of the piezoelectric ceramic square plate of the third embodiment. It is a figure which shows an example of the simulation result regarding the frequency characteristic of the impedance between the common earth electrodes when three of the four divided electrodes of the piezoelectric ceramic square plate are electrically connected. It is a displacement mode figure of a piezoelectric ceramic square board obtained by FEM analysis at the time of impressing sine wave voltage of frequency fr3 between division electrodes 41a, 41b, and 41c, and a common ground electrode. It is a displacement mode figure of a piezoelectric ceramic square board obtained by FEM analysis at the time of impressing sine wave voltage of frequency fr3 between division electrodes 41a, 41c, and 41d, and a common earth electrode. It is the schematic which shows the structure of the ultrasonic motor concerning 4th embodiment of this invention. (A) is the schematic which shows the structure of the ultrasonic motor of 5th embodiment of this invention, (b) is a top view of a piezoelectric ceramic square plate.

<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 elastically applies a piezoelectric vibrator (piezoelectric ceramic square plate 101) that is polarized in the thickness direction and has a plate shape having at least a first corner portion 23 and a second corner portion 24 by applying an alternating voltage. By resonating, the movable element 107 is driven in the forward direction and the reverse direction.
In the piezoelectric ceramic square plate 101, the mode shape due to resonance is asymmetric between the first corner portion 23 and the second corner portion 24.
One main surface (main surface 30) of the piezoelectric ceramic square plate 101 is divided into a plurality of regions A, B, C, and D, and drive electrodes (divided electrodes 41a to 41d) are individually formed in each region, A ground electrode (common ground electrode 102) is formed on the other main surface (main surface 35).
The ultrasonic motor 10 applies the alternating voltage between any one of the divided electrodes 41a to 41d selected from a plurality (four of the regions A to D) and the common ground electrode 102, thereby reducing the maximum displacement due to resonance. The resulting corner portion is switched to the first corner portion 23 or the second corner portion 24.
The first urging portion (friction element 103) that drives the moving element 107 in the forward direction and the second urging portion (friction element 104) that drives the moving element in the reverse direction are the first corner portion 23 and the first urging portion. The two corner portions 24 are provided.

In the present embodiment, the corner portion means a region having a predetermined spread including the apex of the piezoelectric ceramic square plate 101.
The divided electrodes 41a to 41d may be formed on the entire surfaces of the regions A, B, C, and D, or may be formed on partial regions thereof.
In the present embodiment, the fact that the piezoelectric ceramic square plate 101 is divided into regions means that the piezoelectric ceramic square plate 101 has a plurality of electrodes on its main surface 30. It is not always necessary that the ceramic square plate 101 itself has an explicit section indication.

  In addition, the mode shape of the piezoelectric ceramic square plate 101 at the time of resonance is asymmetric between the first corner portion 23 and the second corner portion 24 means that an alternating voltage at the resonance frequency is used as a drive voltage with respect to the piezoelectric ceramic square plate 101. This means that when applied, the amounts of displacement generated in the first corner portion 23 and the second corner portion 24 are different from each other.

Next, the ultrasonic motor 10 of this embodiment will be described in detail.
Piezoelectric ceramic square plate 101 has a rectangular shape, and more specifically, its main surface 30 is square. And the 1st corner part 23 and the 2nd corner part 24 which adjoin each other, and the other two corner parts 21 and 22 are included.

  The main surface 30 of the piezoelectric ceramic square plate 101 is divided into regions A, B, C, and D divided into four equal parts by straight lines parallel to the sides 31 to 34, and four drive electrodes (divided electrodes 41a to 41d) are provided. Is formed.

The ground electrode formed on the main surface 35 of the piezoelectric ceramic square plate 101 may be individually formed so as to face the regions A to D, or may be formed across two or more of the regions A to D. It may be. The ground electrode of the present embodiment is formed as a common ground electrode 102 provided across the four regions A to D on the other main surface 35 of the piezoelectric ceramic square plate 101.
The common ground electrode 102 is formed on the entire surface of the other main surface 35 of the piezoelectric vibrator (piezoelectric ceramic square plate 101).

The urging unit (the first urging unit and the second urging unit) for driving the moving element 107 is not particularly limited as long as it engages with the moving element 107 and drives it.
The biasing portion may be manufactured by attaching an engagement element such as a friction element to a predetermined corner portion of the piezoelectric ceramic square plate 101. In this case, the material of the friction element is not particularly limited, but a ceramic material such as alumina can be given as an example. Alternatively, the urging portion may be produced by roughening the side surface of the corner portion. That is, the urging portion may be manufactured as a separate member from the piezoelectric ceramic square plate 101 or may be formed by processing the piezoelectric ceramic square plate 101 itself.

In addition, an engaging element may be provided on the moving element 107 side by roughening the moving element 107 or the like. In this case, the first corner portion 23 and the second corner portion 24 of the piezoelectric ceramic square plate 101 can be used as an urging portion with a base.
That is, in the present embodiment, the first or second urging portion is provided at the corner portion of the piezoelectric ceramic square plate 101 when the engagement element is provided at the corner portion and when the corner portion is left as a base. Including the case of using as an urging unit.

  The urging portion of the present embodiment projects the friction elements 103 and 104 made of alumina in a diagonal direction from the lower first corner portion 23 and the second corner portion 24 shown in FIG. Attached. Then, by switching the friction element 103 or 104 and pressing against the friction surface of the moving element 107, the moving element 107 is driven in the forward direction or the reverse direction.

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 ultrasonic motor 10 further includes a support portion (support 105) that supports the piezoelectric ceramic square plate 101. In this embodiment, the support 105 is attached to the center circular hole 42 of the piezoelectric ceramic square plate 101, and the center G (see FIG. 2) of the main surface 30 of the piezoelectric ceramic square plate 101 is rotated and rotated with respect to the space. It is rigidly fixed so that it cannot be translated.
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 square plate 101 at least on the outer surface in contact with the piezoelectric ceramic square plate 101. As a result, even when the alternating voltage is applied and the piezoelectric ceramic square plate 101 elastically resonates, the inner diameter of the circular hole 42 is enlarged or reduced, so that the vibration of the piezoelectric ceramic square plate 101 is suppressed without being suppressed. Thus, the piezoelectric ceramic square plate 101 can be supported.

  The support 105 provided at the center of the piezoelectric ceramic square plate 101 is connected to the base 109 via the elastic member 106. The friction elements 103 and 104 are in contact with the surface of the moving element 107 by receiving the urging force of the elastic member 106, or are always in contact by being pressed with a predetermined pressing force.

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 simultaneously connected to the divided electrodes 41a and 41b. Here, the divided electrodes 41 a and 41 b are electrically connected to each other by an electrode pattern on the piezoelectric ceramic square plate 101.
The terminal S1 is connected to the divided electrode 41c, and the terminal S2 is connected to the divided 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 square 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.
In this state, when the switch SW1 is tilted toward the terminal S1, the drive voltage is applied to the divided electrodes 41a, 41b, and 41c. On the other hand, when the switch SW1 is tilted toward the terminal S2, the drive voltage is applied to the divided electrodes 41a, 41b, and 41d.

That is, the ultrasonic motor 10 of the present embodiment includes, as drive electrodes (divided electrodes 41a to 41d), a common drive electrode to which an alternating voltage is constantly applied and a selective drive electrode to which the alternating voltage is selectively applied. Contains.
In the ultrasonic motor 10 of the present embodiment, the divided electrodes 41a and 41b are common drive electrodes, and the divided electrodes 41c and 41d are selective drive electrodes.

  As will be described later, in the ultrasonic motor 10 of this embodiment, the piezoelectric ceramic square plate 101 is applied by applying a drive voltage to the regions A, B, and C, that is, the divided electrodes 41a, 41b, and 41c in an L shape. Resonates, and the second corner portion 24 which is the corner portion of the region D exhibits the maximum displacement. Further, by applying the drive voltage to the regions A, B, and D, that is, the divided electrodes 41a, 41b, and 41d in an L shape, the resonance mode of the piezoelectric ceramic square plate 101 is reversed in the left-right direction in FIG. A first corner portion 23 which is a corner portion of C shows the maximum displacement.

In this embodiment, the selective drive electrodes are formed in the region C where the first corner portion 23 is formed and the region D where the second corner portion 24 is formed.
That is, the divided electrode 41c formed in the region C and the divided electrode 41d formed in the region D are used as first and second selective drive electrodes to which a drive voltage is applied alternatively.

Moreover, in the ultrasonic motor 10 of this embodiment, it is a 2nd selection drive electrode (divided electrode 41d) that drives a 1st biasing part (friction element 103). The second selective drive electrode is formed in the region D where the second corner portion 24 is formed. The first selective drive electrode (divided electrode 41c) is formed in the region C where the first corner portion 23 is formed.
That is, in the present embodiment, the second selective drive electrode (divided electrode 41d) that drives the first biasing portion (friction element 103) is a region different from the region (region C) in which the first corner portion 23 is formed. Is formed. Further, the first selective drive electrode (divided electrode 41 c) for driving the second urging portion (friction element 104) is formed in a region different from the region D in which the second corner portion 24 is formed.

<Operating principle>
Hereinafter, the resonance mode that occurs when a sine wave voltage is applied to the piezoelectric ceramic square plate 101 of the present embodiment and the displacement of the corner portions 21 to 24 will be described in detail.

FIG. 2 is a schematic structural diagram of the piezoelectric ceramic square plate 101 used in the ultrasonic motor 10 of the present embodiment. FIG. 4A is a plan view of the piezoelectric ceramic square plate 101, and FIG. 4B is an elevation view. As indicated by arrows in FIG. 4B, the piezoelectric ceramic square plate 101 is polarized in the thickness direction.
Four divided electrodes 41a to 41d are formed on one surface of regions A, B, C, and D obtained by dividing the piezoelectric ceramic square plate 101 into four equal parts by straight lines parallel to the sides, and the entire surface electrode is formed on the other surface. To form a common ground electrode 102. In FIG. 2, for convenience, the divided electrodes 41a to 41d are illustrated as being electrically separated from each other. However, as illustrated in FIG. 1, the divided electrodes 41a and 41b may be connected to each other.
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 the present embodiment, the deformation amount in the direction connecting the center G of the piezoelectric ceramic square plate 101 and the corner portion of the region where the central divided electrode among the three drive electrodes is formed is This utilizes the phenomenon that the amount of deformation in the direction connecting the center G and other vertices is significantly larger.

  In other words, the present embodiment relates to the center line CL that passes through the center G of the piezoelectric ceramic square plate 101 and bisects the entire common drive electrode (divided electrodes 41a and 41b). By utilizing the fact that the displacement mode is asymmetrical, the moving element 107 is switched and driven in the forward and reverse directions.

FIG. 3 shows an example of a simulation result regarding the frequency characteristics of the impedance with the common earth electrode 102 when any three of the four divided electrodes of the piezoelectric ceramic square plate of FIG. 2 are electrically connected. FIG.
As can be seen from FIG. 3, two frequencies at which the impedance has a minimum value appear. The lower resonance frequency is fr1, and the higher resonance frequency is fr2.

  4A and 4B show FEMs when a sine wave voltage having a frequency fr1 is applied between the divided electrodes 41a, 41c and 41d as drive electrodes and the common ground electrode 102 (see FIG. 2). It is a displacement mode figure which shows the state of a deformation | transformation of the piezoelectric ceramic square plate 101 obtained by analysis. FIG. 4A shows the state of maximum elongation deformation, and FIG. 4B shows the state of maximum contraction 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.

  As can be seen from FIG. 4, in the vicinity of the second corner portion 24 of the region D (see FIG. 2) where the central divided electrode 41 d of the three divided electrodes 41 a, 41 c and 41 d arranged in an L shape is formed. Is significantly larger than the displacement in the vicinity of the other corner portions 21 to 23.

On the other hand, in FIGS. 5A and 5B, the resonance frequency of the sine wave voltage applied between the three divided electrodes 41a, 41c and 41d and the common ground electrode 102 is set to the higher frequency fr2. It is a displacement mode figure which shows the state of a deformation | transformation of the piezoelectric ceramic square plate 101 obtained by the FEM analysis in the case. FIG. 4A shows the state of maximum elongation deformation, and FIG. 4B shows the state of maximum contraction deformation.
As can be seen from FIG. 5, in this case, the deformation in the vicinity of the corner portion 22 in the region B of the divided electrode 41b to which the drive voltage is not applied is compared with the displacement in the vicinity of the other corner portions 21, 23, 24. It is noticeably larger.

That is, three of the four divided electrodes are electrically connected, and a sine wave voltage of either the lower frequency fr1 or the higher frequency fr2 is connected to the common ground electrode 102. By applying, large deformation in the direction connecting the apex and the center G of the piezoelectric ceramic square plate 101 can be generated in the vicinity of one corner portion of the piezoelectric ceramic square plate 101.
In the case of the piezoelectric ceramic square plate 101 of the present embodiment, when a sine wave voltage having a frequency fr1 is applied to the three divided electrodes and the common ground electrode 102, the central electrode is formed among the three drive electrodes. It can be seen that the displacement at the corner of the region is maximized.
On the other hand, when a sine wave voltage having a frequency fr2 is applied to the three divided electrodes and the common ground electrode 102, the corner of the region where the sine wave voltage is not applied, in other words, the center of the three drive electrodes. It can be seen that the displacement becomes maximum at the corner portion of the region located on the opposite side of the center G with respect to the region where the electrode is formed.

Here, when the center G is the origin and the regions A to D are arranged in the first to fourth quadrants of the XY plane, the piezoelectric ceramic square plate 101 of this embodiment has mirror symmetry with respect to the X axis and the Y axis. . Therefore, referring to FIG. 4, when a sinusoidal voltage having a frequency fr1 is applied to the divided electrodes 41b, 41c and 41d, the displacement mode diagram is reversed left and right. That is, in this case, the displacement at the first corner portion 23 is significantly larger than the displacement at the other corner portions 21, 22, 24.
Referring to FIG. 5, the displacement mode diagram is also reversed left and right when a sine wave voltage of frequency fr2 is applied to the divided electrodes 41b, 41c and 41d. That is, in this case, the displacement in the corner portion 21 is significantly larger than the displacement in the other corner portions 22, 23, 24.

  In the case of FIG. 4 and FIG. 5, a voltage is generated in the divided electrode to which no drive voltage is applied. By using this voltage as a feedback voltage, a self-excited oscillation circuit is configured as described later. can do.

FIGS. 6A to 6D are explanatory views of the operation principle of the ultrasonic motor 10 of this embodiment.
FIGS. 4A and 4B show the case where the divided electrodes 41a, 41b and 41c are drive electrodes, and a sine wave voltage of the frequency fr2 in FIG. 3 is applied between these electrodes and the common ground electrode 102 on the back surface. FIG. 3 is a mode diagram showing the state of maximum elongation deformation (FIG. 1A) and maximum contraction deformation (FIG. 2B) of the piezoelectric ceramic square plate 101. FIG.
As described above, when a sinusoidal voltage having a frequency fr2 is applied to the three divided electrodes, a maximum displacement occurs in the corner portion of the region where the divided electrodes to which the voltage is not applied are formed. In this case, since the voltage is not applied to the divided electrode 41d, the displacement at the second corner portion 24 is maximized.
On the other hand, (c) and (d) in the figure show that the divided electrodes 41a, 41b and 41d are drive electrodes, and a sinusoidal voltage having a frequency fr2 is applied between these electrodes and the common ground electrode 102 on the back surface. It is a mode figure which shows the state of the maximum expansion deformation | transformation (the figure (c)) and maximum shrinkage deformation (the figure (d)) of the piezoelectric ceramic square plate 101.
In this case, since the voltage is not applied to the divided electrode 41c, the displacement at the first corner portion 23 is maximized.

  In the case of FIG. 6, other corner portions (first corner portion 23 and second corner) adjacent in the left-right direction with respect to the corner portion (second corner portion 24 and first corner portion 23) having the maximum displacement. The displacement in the vicinity of the part 24) is very small.

Therefore, in the case of FIG. 6, when the divided electrodes 41 c and 41 d are selected drive electrodes and the divided electrodes 41 a and 41 b are common drive electrodes, the corner portion that is maximum displaced can be switched by switching the selected drive electrodes. Is possible.
More specifically, when a sine wave voltage is always applied to the common drive electrodes (divided electrodes 41a and 41b) and the first selective drive electrode (divided electrode 41c) is further energized, As shown in (b), the second corner portion 24 where the divided electrode 41d to which no voltage is applied is formed is driven in a direction to advance and retreat with respect to the center G substantially on the diagonal line of the piezoelectric ceramic square plate 101. be able to.

  Similarly, when a sine wave voltage is always applied to the common drive electrodes (divided electrodes 41a and 41b) and the second selected drive electrode (divided electrode 41d) is selected and energized, the same figure (c). And as shown in (d), the 1st corner part 23 in which the division electrode 41c in which a voltage is not applied is formed is driven in the direction which advances / retreats with respect to the center G on the substantially diagonal line of the piezoelectric ceramic square plate 101. can do.

And the setting of this common drive electrode and selection drive electrode is common to the ultrasonic motor 10 of this embodiment shown in FIG.
Therefore, the friction elements 103 and 104 are formed on the first corner portion 23 and the second corner portion 24, respectively, and are in contact with the surface of the moving element 107, and either one of the selective drive electrodes and the common By applying a sine wave voltage of frequency fr2 to the drive electrode, either one of the friction elements 103 or 104 advances and retreats in an oblique direction, dominantly over the other.

  In the ultrasonic motor 10 of the present embodiment, the friction element 103 vibrates in a direction connecting the support tool 105 and the first corner portion 23 due to resonance of the piezoelectric ceramic square plate 101, and the friction element 104 is connected to the support tool 105 and the second corner. It vibrates in the direction connecting the corner portion 24.

For example, in the case of the displacement mode of the piezoelectric ceramic square plate 101 in which the second corner portion 24 shows the maximum amount of displacement as shown in FIGS. 6A and 6B, the piezoelectric ceramic square plate 101 as shown in FIG. 1 extends, the friction element 104 protrudes in the lower left direction in FIG. 1, and applies a left frictional force to the surface of the moving element 107. While the piezoelectric ceramic square plate 101 is contracted as shown in FIG. 6B, the friction element 104 is not in contact with the surface of the moving element 107, so that the moving element 107 moves to the left according to inertia. Continue the exercise. When the piezoelectric ceramic square plate 101 extends again as shown in FIG. 6A, the mover 107 is pushed by the friction element 104 and further moves to the left.
On the other hand, when the switch SW1 is switched from the terminal S1 to the terminal S2 and the selection drive electrode is switched from the divided electrode 41c to the divided electrode 41d, the displacement modes of the piezoelectric ceramic square plate 101 are as shown in FIGS. . In this case, the friction element 103 applies an urging force in the right direction in FIG. Therefore, it is possible to obtain the ultrasonic motor 10 in which the moving element 107 can be switched between forward and reverse traveling by operating the switch SW1.

  The piezoelectric ceramic square plate 101 is connected to the base 109 by an elastic member 106. Therefore, even if the reaction force of the friction element 103 or 104 that urges the moving element 107 is loaded upward on the piezoelectric ceramic square plate 101, the piezoelectric ceramic square plate 101 recovers to the reference position by the elastic restoring force of the elastic member 106. However, the friction element 103 or 104 and the moving element 107 are not in contact with each other.

Further, when the friction element 103 or 104 is driven by the maximum displacement of the piezoelectric ceramic square plate 101, even if the other friction element comes into contact with the moving element 107, the displacement of the other friction element is extremely small. The desired feed force of the child 107 is not affected.
Specifically, in the case of FIG. 6A, the amount of displacement of the first corner portion 23 is slight with respect to the second corner portion 24 showing the maximum displacement. Further, the displacement direction of the first corner portion 23 is substantially perpendicular to the feed direction of the moving element 107 (in this case, the left side in the figure), and no frictional force is applied in the direction opposite to the feed direction. Therefore, the first corner portion 23 does not adversely affect the feed force of the moving element 107.

The effects of the ultrasonic motor 10 of the present embodiment will be described.
According to the ultrasonic motor 10 of the present embodiment, the corner portions 21 to 24 that cause the maximum displacement due to the resonance of the piezoelectric ceramic square plate 101 are switched by selecting the drive electrode. For this reason, the moving direction of the moving element 107 can be switched between forward and reverse by a single-phase alternating voltage, and there is no problem of deterioration of the characteristics of the ultrasonic motor 10 due to temperature change or the like.
Further, in the ultrasonic motor 10 of the present embodiment, the friction element 103 or 104 that drives the moving element 107 is provided in the first corner portion 23 or the second corner portion 24 where the maximum displacement due to resonance occurs. Thereby, high driving efficiency of the moving element 107 can be obtained.
In addition, the ultrasonic motor 10 of the present embodiment can be easily machined with high accuracy because the piezoelectric ceramic square plate 101 has a rectangular shape.

Moreover, in the ultrasonic motor 10 of this embodiment, the drive electrode includes a common drive electrode to which an alternating voltage is constantly applied and a selective drive electrode to which the alternating voltage is selectively applied. As a result, an alternating voltage can be applied to the main surface 30 of the piezoelectric ceramic square plate 101 with respect to an area of about ¾, so that a large amount of displacement can be obtained for the friction element 103 or 104.
Further, when the piezoelectric ceramic square plate 101 is square as in the present embodiment, voltage is applied using two of the quarter regions divided by line segments connecting the midpoints of the opposing sides as selection electrodes. By switching the opening and using the other two as a common electrode, the area of the voltage application region and the area of the opening region are appropriately balanced, and the friction elements 103 and 104 can be driven very efficiently.

  Moreover, in the ultrasonic motor 10 of this embodiment, an alternating voltage is applied with respect to the area | region containing three of four corner parts. And an alternating voltage is applied to the division | segmentation electrode of the area | region where the urging | biasing part to drive is not provided, and the said urging | biasing part is driven. Therefore, since the distortion of the piezoelectric ceramic square plate 101 around the three corner portions is synthesized and the urging portion is displaced, a large amount of displacement can be obtained.

  In the ultrasonic motor 10 of this embodiment, the friction element 103 or 104 vibrates in the direction connecting the center G of the piezoelectric ceramic square plate 101 and the first corner portion 23 or the friction element 104 due to resonance of the piezoelectric ceramic square plate 101. To do. As a result, the biasing force applied to the moving element 107 from the friction element 103 or 104 balances the pressing force in the direction perpendicular to the moving element 107 and the pushing force in the in-plane direction. Therefore, it is possible to realize suitable driving efficiency in the friction element 103 or 104 that obtains a driving force by a frictional force with the moving element 107.

<Second embodiment>
FIG. 7 is a schematic view showing the structure of another embodiment of the ultrasonic motor 10 of the present invention.
In the figure, 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 divided electrodes 41c and 41d. Here, the divided electrodes 41 c and 41 d are connected by an electrode pattern on the piezoelectric ceramic square plate 101.
The divided electrodes 41a and 41b are insulated from each other.

The terminal S01 is connected to the divided electrode 41b, and the terminal S02 is connected to the divided electrode 41a. 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 in the middle of resistors R11 and R12 connected between the divided electrode 41a and the ground terminal 115. The terminal S12 is provided in the middle of the resistors R21 and R22 connected between the divided electrode 41b and the ground terminal 116.
The oscillation frequency of the feedback oscillator 112 is set to the lower frequency fr1 in FIG.
Here, the values of the series resistances of the resistors R11 and R12 and the series resistances of the resistors R21 and R22 are set to a high resistance value that effectively opens the divided electrode to which no drive voltage is applied. 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 divided electrodes 41b, 41c and 41d. Therefore, as described above, the maximum displacement occurs in the corner portion (first corner portion 23) of the region C corresponding to the center of the three drive electrodes. Therefore, the moving element 107 is protruded by the friction element 103 attached to the first corner portion 23, and the moving element 107 moves rightward.
On the other hand, when the switch SW2 is tilted downward, the drive voltage is applied to the divided electrodes 41a, 41c, and 41d, and the vicinity of the second corner portion 24 is deformed. Therefore, the friction element attached to the second corner portion 24 The mover 107 is projected by 104, and the mover 107 moves to the left.

That is, in the ultrasonic motor 10 of the present embodiment, common drive electrodes are formed at the first corner portion 23 and the second corner portion 24, and the divided electrodes 41c and 41d are common drive electrodes. Further, the divided electrodes 41a and 41b are selective drive electrodes.
The ultrasonic motor 10 of the present embodiment can be switched so as to move the mover 107 in the forward and reverse directions by simply switching the switch SW2.

Here, the selective drive electrode (divided electrode 41c or 41d) to which no alternating voltage (sine wave voltage) is applied is opened. The opened selective drive 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. 8 is a schematic view showing the structure of the ultrasonic motor 10 according to the present embodiment.
The ultrasonic motor 10 of the present embodiment is different from the first embodiment in the divided shapes of the regions A to D and the shapes of the divided electrodes.
That is, in the ultrasonic motor 10 of this embodiment, one main surface 30 of the piezoelectric vibrator (piezoelectric ceramic square plate 101) is divided into four regions A to D by two diagonal lines, and adjacent regions. In addition, common drive electrodes (divided electrodes 41a and 41c) and selective drive electrodes (divided electrodes 41b and 41d) are alternately arranged.

Hereinafter, the ultrasonic motor 10 of this embodiment will be described in detail.
One main surface 30 of the piezoelectric ceramic square plate 101 is square, and includes a first corner portion 23 and a second corner portion 24 that are adjacent to each other, and two other corner portions 21 and 22.

The regions A to D of the present embodiment have a substantially right-angled isosceles triangle shape with the sides 31 to 34 of the piezoelectric ceramic square plate 101 as the bottom and the center G of the piezoelectric ceramic square plate 101 as the apex.
The regions A to D have substantially the same shape, and the divided electrodes 41a to 41d are formed on almost the entire surface of each of the regions A to D.
On the other main surface 35 of the piezoelectric ceramic square plate 101, a common ground electrode 102 is formed on the entire surface.

  In the corner portions 21 to 24 of the piezoelectric ceramic square plate 101, the base angles of the two divided electrodes 41a to 41d adjacent to each other are arranged close to each other and apart from each other.

In the ultrasonic motor 10 of the present embodiment, a pair of divided electrodes 41a and 41c facing each other across the center G are used as a common drive electrode, and the other pair of divided electrodes 41b and 41d are used as a selective drive electrode.
That is, an alternating voltage having a predetermined frequency is applied between one of the selected drive electrodes (divided electrode 41 b or 41 d) and the common drive electrode (divided electrodes 41 a and 41 c) and the common ground electrode 102.
The common drive electrodes (divided electrodes 41a and 41c) are electrically connected to each other.
The selection drive electrode to which the alternating voltage is applied is switched to the divided electrode 41b or 41d by the operation of the switch SW1.

  The friction elements 103 and 104 are provided on both sides of the divided electrode 41c which is a common drive electrode. More specifically, the friction elements 103 and 104 are provided at the first corner portion 23 and the second corner portion 24 on both sides of the side 33 constituting the region C where the divided electrode 41c is formed.

  The circuit configuration including the moving element 107, the sliding mechanism 108, the base 109, the support member 105, the elastic member 106, and the oscillator 110 of this embodiment is the same as that of the first embodiment.

  The resonance mode that occurs when a sine wave voltage is applied to the piezoelectric ceramic square plate 101 of the present embodiment and the displacement of the corner portions 21 to 24 will be described in detail.

FIGS. 9A and 9B are schematic structural diagrams of the piezoelectric ceramic square plate 101 used in the ultrasonic motor 10 of the present embodiment. 2A is a plan view of the piezoelectric ceramic square plate 101, and FIG. 2B is a sectional view taken along line II-II. As indicated by arrows in FIG. 4B, the piezoelectric ceramic square plate 101 is polarized in the thickness direction.
Four divided electrodes 41a to 41d are formed in substantially right-angled isosceles triangular regions A, B, C, and D obtained by dividing one main surface 30 of the piezoelectric ceramic square plate 101 into four equal parts by two diagonal lines. A full-surface electrode is formed on the other main surface 35 to form a common ground electrode 102.
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 the present embodiment, the displacement mode at the time of resonance of the piezoelectric ceramic square plate 101 is asymmetric with respect to the center line CL that bisects the common drive electrodes (divided electrodes 41a and 41c) through the center G of the piezoelectric ceramic square plate 101. By utilizing this, the moving element 107 is switched and driven in the forward and reverse directions.

FIG. 10 shows a simulation of the frequency characteristics of the impedance with the common ground electrode 102 when any three of the four divided electrodes 41a to 41d of the piezoelectric ceramic square plate of FIG. 9 are electrically connected. It is a figure which shows an example of a result.
Even if any three of the four divided electrodes 41a to 41d are selected, the three divided electrodes are arranged in a U-shape.

  As can be seen from FIG. 10, two frequencies at which the impedance of the piezoelectric ceramic square plate 101 shows a minimum value appear in the vicinity of 200 kHz (specifically, 204 kHz and 206 kHz). The lower resonance frequency is fr3 and the higher resonance frequency is fr4.

  11A and 11B show FEMs when a sine wave voltage of frequency fr3 is applied between the divided electrodes 41a, 41b and 41c as drive electrodes and the common ground electrode 102 (see FIG. 2). It is a displacement mode figure which shows the state of a deformation | transformation of the piezoelectric ceramic square plate 101 obtained by analysis. FIG. 4A shows the state of maximum elongation deformation, and FIG. 4B shows the state of maximum contraction deformation. In the displacement mode diagram shown in each drawing of FIG. 11, 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.

As shown in FIG. 11, the corners at both ends of the side 32 constituting the region B (see FIG. 9) in which the central divided electrode 41b is formed among the three divided electrodes 41a, 41b and 41c arranged in a U-shape. The amount of displacement of the portions 22 and 23 is significantly larger than the amount of displacement in the vicinity of the other corner portions 21 and 24.
The displacement amounts of the corner portions 22 and 23 are substantially equal to each other, and the displacement amounts of the corner portions 21 and 24 are also approximately equal to each other.
Further, the displacement mode shape of the piezoelectric ceramic square plate 101 is vertically symmetrical in the figure. In other words, the piezoelectric ceramic square plate 101 resonates mirror-symmetrically with respect to a center line (a center line that bisects each of the regions B and D) perpendicular to the center line CL (see FIG. 9).

  12A and 12B show FEM analysis when a sinusoidal voltage of frequency fr3 is applied between the three divided electrodes 41a, 41c and 41d as drive electrodes and the common ground electrode 102. FIG. It is a displacement mode figure which shows the state of a deformation | transformation of the obtained piezoelectric ceramic square plate. FIG. 4A shows the state of maximum elongation deformation, and FIG. 4B shows the state of maximum contraction deformation.

As can be seen from FIG. 12, also in this case, the region D in which the central divided electrode 41d is formed among the three divided electrodes 41a, 41d and 41c arranged in a U-shape (inverse U-shape) (see FIG. 9). The amount of displacement of the corner portions 21 and 24 at both ends of the side 34 that constitutes () is significantly larger than the amount of displacement in the vicinity of the other corner portions 22 and 23.
The displacement mode shape of the piezoelectric ceramic square plate 101 is vertically symmetric in the same figure. Therefore, the displacement amounts of the corner portions 22 and 23 are substantially equal to each other, and the displacement amounts of the corner portions 21 and 24 are also approximately equal to each other.

From FIGS. 11 and 12, by applying the sine wave voltage by selectively switching the divided electrodes 41b and 41d as the selective drive electrodes while constantly applying the sine wave voltage with the divided electrodes 41a and 41c as the common drive electrodes, It can be seen that the mode shape of the piezoelectric ceramic square plate 101 is reversed with respect to the center line CL (see FIG. 9).
Thereby, the corner part which shows the maximum displacement of the piezoelectric ceramic square plate 101 is switched to the corner parts 22 and 23 or the corner parts 21 and 24.

  In the case of the piezoelectric ceramic square plate 101 of the present embodiment, as shown in FIG. 8, one friction element 103 is provided in one or both of the corner portions 22 or 23, and the other is provided in one or both of the corner portions 21 or 24. The friction element 104 is provided. Thereby, the movable element 107 can be switched and driven in the forward and reverse directions by selecting the selection drive electrode (divided electrode 41b or 41d) to which the drive voltage is applied.

In addition, regarding the ultrasonic motor 10 of the present embodiment, a sine wave voltage having a frequency fr4 (see FIG. 10) may be applied to the piezoelectric ceramic square plate 101 instead of the above-described aspect.
In this case, when a sinusoidal voltage is applied to one of the common drive electrode (divided electrodes 41a and 41c) and the selective drive electrode (divided electrode 41b or 41d), the displacement at resonance is released (no voltage applied). It is clear that the maximum is obtained at the corners on both sides of the selected drive electrode. Specifically, when a sinusoidal voltage having a frequency fr4 is applied to the divided electrodes 41a, 41b and 41c, the maximum displacement occurs in the vicinity of the corner portions 21 and 24, and the same is applied to the divided electrodes 41a, 41c and 41d. The maximum displacement occurs near the corners 22 and 23.
Therefore, even when a sinusoidal voltage with a frequency fr4 is used as the drive voltage, the ultrasonic motor 10 of this embodiment can drive the moving element 107 while switching between the forward and reverse directions.

<Fourth embodiment>
FIG. 13 is a schematic view showing the structure of another embodiment of the ultrasonic motor 10 of the present invention. The ultrasonic motor 10 of this embodiment is obtained by applying the piezoelectric ceramic square plate 101 of the third embodiment to the ultrasonic motor 10 of the second embodiment having a feedback transmission circuit.

The feedback oscillator 112, resistors R11 to R22, switch SW2, and ground terminals 115 and 116 are common to the ultrasonic motor 10 of the second embodiment shown in FIG.
The common terminal S00 of the first circuit C1 is always connected to the output terminal 113 of the feedback oscillator (amplifier) 112 and is simultaneously connected to the divided electrode 41a. Here, the divided electrodes 41 a and 41 c are electrically connected by an electrode pattern on the piezoelectric ceramic square plate 101.

The terminal S01 is connected to the divided electrode 41b, and the terminal S02 is connected to the divided 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 in the middle of resistors R11 and R12 connected between the divided electrode 41d and the ground terminal 115. The terminal S12 is provided in the middle of the resistors R21 and R22 connected between the divided electrode 41b and the ground terminal 116.
The oscillation frequency of the feedback oscillator 112 of this embodiment is set to the lower frequency fr3 in FIG.

In this state, when the switch SW2 is tilted upward, the drive voltage is applied to the divided electrodes 41a, 41b and 41c. Therefore, as shown in FIG. 11, the maximum displacement occurs in the corner portion (first corner portion 23) of the region B which is the center of the three drive electrodes. Therefore, the moving element 107 is protruded by the friction element 103 attached to the first corner portion 23, and the moving element 107 moves rightward.
On the other hand, when the switch SW2 is tilted downward, the drive voltage is applied to the divided electrodes 41a, 41c and 41d. Therefore, as shown in FIG. 12, the maximum displacement occurs in the vicinity of the corner portion (second corner portion 24) of the region D. Therefore, the moving element 107 is protruded by the friction element 104 attached to the second corner portion 24, and the moving element 107 moves leftward.

That is, the ultrasonic motor 10 of the present embodiment can also be switched so as to move the mover 107 in the forward and reverse directions simply by switching the switch SW2.
Here, the selective drive electrode (divided electrode 41b or 41d) to which no alternating voltage (sine wave voltage) is applied is opened. The opened selective drive electrode is used as a feedback electrode for the self-excited oscillation circuit.

<Fifth embodiment>
In the ultrasonic motors 10 according to the third and fourth embodiments, the maximum displacement occurs simultaneously at the two corner portions of the resonating piezoelectric ceramic square plate 101. Specifically, when an alternating voltage having a frequency fr3 is applied to the divided electrodes 41a, 41b, and 41c, the maximum displacement occurs equally at the corner portions 22 and 23 as shown in FIG. Further, when an alternating voltage having a frequency fr3 is applied to the divided electrodes 41a, 41c and 41d, the maximum displacement occurs equally at the corner portions 21 and 24 as shown in FIG.
The ultrasonic motor 10 of this embodiment drives the moving element 107 by using two corner portions 21 to 24 at the same time.

  In the ultrasonic motor 10 of the present embodiment, the first urging portion is provided at two first corner portions (corner portions 22 and 23) sandwiching one selective drive electrode (divided electrode 41b), and the second urging portion is provided. Are provided at two second corner portions (corner portions 21 and 24) sandwiching another selective drive electrode (divided electrode 41d).

  That is, in the ultrasonic motor 10 according to the present embodiment, the first urging portions that drive the mover 107 in the forward direction at the corner portions 22 and 23 on both sides of the side 32 constituting the region B where the divided electrode 41b is formed. Used as Then, the corner portions 21 and 24 on both sides of the side 34 constituting the region D in which the divided electrode 41d is formed are used as a second urging portion that drives the moving element 107 in the reverse direction.

FIG. 14A is a schematic view showing the configuration of the ultrasonic motor 10 of this embodiment, and FIG. 14B is a plan view of the piezoelectric ceramic square plate 101.
The ultrasonic motor 10 of the present embodiment includes a linear guide type structure configured by utilizing two resonance deformations generated in the piezoelectric ceramic square plate 101. In the figure, a drive circuit for applying a drive voltage to the piezoelectric ceramic square plate 101 is not shown.

  In the ultrasonic motor 10 of the present embodiment, the regions A to D of the piezoelectric ceramic square plate 101 have a right-angled isosceles triangle shape formed by dividing the square main surface 30 into four diagonal lines, as in FIG. ing. Divided electrodes 41a and 41c as common electrodes are formed in regions A and C, and divided electrodes 41b and 41d as selective drive electrodes are formed in regions B and D.

  In the ultrasonic motor 10 of the present embodiment, the first selection drive electrode (divided electrode 41b) and the second selection drive electrode (divided electrode 41d) are arranged mirror-symmetrically with respect to the center line CL of the main surface 30. . Further, the common drive electrodes (divided electrodes 41a and 41c) are each divided into two equal parts by the center line CL.

  When a sine wave voltage of frequency fr3 (see FIG. 10) is applied between one of the first or second selective drive electrodes and the common drive electrode and the common ground electrode 102 (see FIG. 9), the piezoelectric ceramic The square plate 101 resonates. In the mode shape, as shown in FIGS. 11 and 12, the corner portions 22 and 23 or the corner portions 21 and 24 exhibit maximum displacement at the same time. Specifically, when the first selection drive electrode (divided electrode 41b) is selected as the drive electrode, the corner portions 22 and 23 exhibit the maximum displacement. When the second selection drive electrode (divided electrode 41d) is selected as the drive electrode, the corner portions 21 and 24 exhibit the maximum displacement.

  Here, the displacement mode shape of the piezoelectric ceramic square plate 101 is vertically symmetrical in FIG. Therefore, the movable element 107 is arranged vertically symmetrically with respect to the piezoelectric ceramic square plate 101, in other words, the movable element 107 is arranged so as to face the region A and the region C, respectively. The child 107 can be driven.

  Therefore, according to the ultrasonic motor 10 of the present embodiment, the two movable elements 107 can be simultaneously driven by disposing the two movable elements 107 separately from the areas A and C, respectively. As shown in FIG. 14A, in the ultrasonic motor 10 of this embodiment, one movable element 107 that accommodates the piezoelectric ceramic square plate 101 may be driven with the area A and the area C interposed therebetween.

The mover 107 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 square plate 101. That is, as shown in FIG. 14A, the moving element 107 is a member having a U-shaped cross section that is open upward.
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 side 31 and the side 33 of the piezoelectric ceramic square plate 101.
That is, the piezoelectric ceramic square 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 square plate 101 has a rod shape, passes through the center G of the piezoelectric ceramic square plate 101, protrudes downward in the direction perpendicular to the surface of the piezoelectric ceramic square plate 101, and is inserted into the hole 126. The support 105 can slide substantially only in the longitudinal direction with respect to the hole 126.

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 square plate 101 is fixed to the bottom surface 132 of the groove 131.

When an alternating voltage having a frequency fr3 is applied as a drive voltage to the first selective drive electrode (divided electrode 41b) and the common drive electrodes (divided electrodes 41a and 41c) of the piezoelectric ceramic square plate 101, the corner portions 22 and 23 are applied. 11 resonates and drives the friction plate 125 in the positive direction as shown in FIG.
Further, when an alternating voltage having a frequency fr3 is applied as a drive voltage to the second selection drive electrode (divided electrode 41d) and the common drive electrode (divided electrodes 41a and 41c), the corner portions 21 and 24 are shown in FIG. Thus, the friction plate 125 is driven in the reverse direction.

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 square plate 101, the corner portions 21 to 24 (biasing portions) of the piezoelectric ceramic square plate 101. Is engaged with a predetermined frictional force.
Then, due to the elastic deformation of the corner portions 22 and 23 or 21 and 24 (biasing portions) caused by the application of the driving voltage, the moving element 107 is driven on the base guide 130 by receiving a frictional force in the longitudinal direction.
Further, by switching the selection of the first or second selection drive electrode (divided electrodes 41b and 41d) to which the drive voltage is applied, the vibration direction of the urging portion is reversed in the longitudinal direction, and the feed direction of the moving element 107 is correct. Conversely, it can be switched.

The present invention is not limited to the above-described embodiment, and includes various modifications and improvements as long as the object of the present invention is achieved.
In the above embodiment, an alternating voltage is applied to the three regions of the piezoelectric ceramic square plate 101 divided into the four regions A to D. However, the present invention is not limited to this.
That is, for example, by applying an alternating voltage to only one of the four regions A to D, the mode shape by resonance can be changed to the first corner portion 23 and the second corner with respect to the piezoelectric ceramic square plate 101. It can be asymmetric with the part 24. More specifically, when an alternating voltage is applied only to the divided electrode 41c in the region C including the first corner portion 23, the displacement at the first corner portion 23 or the corner portion 21 is maximized, and the other corners are It is possible to suppress the displacement in the part.
Therefore, by switching the drive electrode (selective drive electrode) from 41c to 41d and applying an alternating voltage, the friction elements 103 and 104 can be switched in the forward and reverse directions also by this mode.

  In other words, in the present invention, one selective drive electrode (divided electrode 41c) for driving the first biasing portion (friction element 103) is formed in the region C including the first corner portion 23, and the second biasing force is formed. Another selective drive electrode (divided electrode 41 d) for driving the portion (friction element 104) may be formed in the region D including the second corner portion 24.

  For example, in the above-described embodiment, the case where a single plate-shaped piezoelectric ceramic plate is used as the piezoelectric vibrator has been described. However, the present invention is not limited to this. The piezoelectric vibrator is a laminated piezoelectric ceramic plate in which piezoelectric ceramic layers and electrode layers are alternately laminated, and every other electrode layer is divided into four divided electrodes as shown in FIG. 2, for example, and every other layer. These electrode layers may be used as the common ground electrode 102. Then, the divided electrodes stacked in the same region may be electrically connected to each other. Accordingly, the same effect can be obtained with a lower driving voltage as compared with the case where a single plate-like piezoelectric vibrator is used.

  Moreover, although the case where the shape of the piezoelectric vibrator was a square plate was exemplarily described in the above embodiment, the present invention is not limited to this. When a rectangular piezoelectric vibrator is used, the shape of the main surface may be a rectangle, a rhombus, a parallelogram, or an isosceles trapezoid. Further, the piezoelectric vibrator is not necessarily provided with other corner portions except for the corner portion where the urging portion is provided, and may have a curved shape such as an arc shape.

In dividing the piezoelectric vibrator into a plurality of regions, the areas of the regions may be equal or different from each other. Each region does not necessarily include one or more corner portions. For example, when a rectangular piezoelectric vibrator is used, other regions may be provided in the vicinity of the center where the support tool 105 is formed in addition to the four regions including each corner portion. Further, regarding the shape of each region, it is an example that it is rectangular as in the above embodiment, and it may be a triangle, a hexagon, a shape including a curve, or a combination thereof. It may be different.
When the two urging members are provided on both sides of one side of the piezoelectric vibrator, the shape of each region is preferably symmetrical with respect to the vertical bisector of the one side.

  Furthermore, the drive circuits shown in FIGS. 1, 7, 8 and 13 are merely examples, and similar functions can be satisfied by various circuit configurations such as a digital signal processing circuit.

In the above-described embodiment, the driving direction of the moving element 107 is exemplified by linear advance / retreat driving, but the present invention is not limited to this. By engaging the urging portion with the curved surface portion of the movable element 107, the movable element 107 can be driven to rotate.
Further, when the moving element 107 is driven, it may be driven simultaneously by a plurality of urging units, or may be driven by a plurality of ultrasonic motors 10.

The above-described embodiments of the present invention and modifications thereof include the following technical ideas.
(1) A piezoelectric vibrator that is polarized in the thickness direction and has a plate shape having at least a first corner portion and a second corner portion is elastically resonated by application of an alternating voltage, so that the movable element is moved in the forward and reverse directions. An ultrasonic motor driven in a direction, wherein the piezoelectric vibrator has an asymmetric mode shape due to the resonance between the first corner portion and the second corner portion, and the piezoelectric vibrator has a plurality of principal surfaces on one side. Drive electrodes are individually formed in each of the regions, and a ground electrode is formed on the other main surface, and the alternating electrode is provided between any one of the plurality of drive electrodes selected from the plurality and the ground electrode. When a voltage is applied, the corner portion causing the maximum displacement due to the resonance is switched to the first corner portion or the second corner portion, and the moving element is driven in the positive direction. Ultrasonic motor for the one urging portion, the second urging unit for driving the moving element in the reverse direction, characterized in that provided respectively between the first corner portion and the second corner portion;
(2) The ultrasonic motor, wherein the drive electrode includes a common drive electrode to which the alternating voltage is constantly applied and a selective drive electrode to which the alternating voltage is selectively applied;
(3) The ultrasonic motor as described above, wherein the selective drive electrodes are respectively formed in a region where the first corner portion is formed and a region where the second corner portion is formed;
(4) The ultrasonic motor described above, wherein the common drive electrode is formed in both the region where the first corner portion is formed and the region where the second corner portion is formed;
(5) The one main surface is divided into four equal areas by straight lines parallel to the sides of the rectangular piezoelectric vibrator, and the common drive electrode or the selective drive electrode is formed in the area. The above ultrasonic motor;
(6) The one main surface is divided into four regions by two diagonal lines of the rectangular piezoelectric vibrator, and the common drive electrode and the selective drive electrode are alternately arranged in the adjacent regions. An ultrasonic motor as described above arranged in;
(7) The first urging portion is provided at the two first corner portions sandwiching one of the selection drive electrodes, and the second urging portion is disposed at the two second portions of the other selection drive electrode. The ultrasonic motor as described above, wherein the ultrasonic motor is provided at two corners;
(8) The piezoelectric vibrator has a rectangular shape and includes the first corner portion and the second corner portion adjacent to each other, and the other two corner portions, and drives the first biasing portion. The selective driving electrode is formed in a corner portion other than the first corner portion, and the other selective driving electrode for driving the second urging portion is formed in a corner portion other than the second corner portion. An ultrasonic motor as described above,
(9) One of the selective drive electrodes that includes the first corner portion and the second corner portion adjacent to each other and another corner portion and drives the first biasing portion is other than the first corner portion. The other drive electrode for driving the second biasing portion is provided in the region where the corner portion other than the second corner portion is formed. Said ultrasonic motor characterized;
(10) The ultrasonic motor as described above, wherein the ground electrode is formed on the entire other main surface of the piezoelectric vibrator;
(11) It further includes a support portion that supports the piezoelectric vibrator, and the first urging portion vibrates in a direction connecting the support portion and the first corner portion due to resonance of the piezoelectric vibrator, The ultrasonic motor as described above, wherein the second urging portion vibrates in a direction connecting the support portion and the second corner portion;
(12) One selection drive electrode for driving the first biasing portion is provided in a region where the first corner portion is formed, and the other selection drive electrode for driving the second biasing portion is The ultrasonic motor as described above, wherein the ultrasonic motor is provided in a region where the second corner portion is formed;
(13) The one selective drive electrode that drives the first biasing portion is provided in a region where the second corner portion is formed,
The ultrasonic motor as described above, wherein the other selective driving electrode for driving the second urging portion is provided in a region where the first corner portion is formed;
(14) The above ultrasonic motor in which the selective drive electrode to which the alternating voltage is not applied is opened;
(15) The ultrasonic motor as described above, wherein the opened selective driving electrode is a feedback electrode for a self-excited oscillation circuit.

10 Ultrasonic motor 21-24 Corner
30 main surface 31-34 sides
35 Main surfaces 41a to 41d Split electrodes
42 circular hole 101 piezoelectric ceramic square plate 102 common ground electrode 103, 104 friction element 105 support tool 106 elastic member 107 moving element 108 sliding mechanism 109 base 110 oscillator 111 output terminal 112 feedback oscillator (amplifier)
113 Output terminal 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 A to D region
C1 first circuit
C2 Second circuit
CL center line
G center
R0 Internal resistors R11 to R22 Resistors S0, S00, S10 Common terminals S01, S02, S1, S2, S11, S12 Terminals SW1, SW2 switch

Claims (8)

A piezoelectric vibrator that is polarized in the thickness direction and has a plate shape having at least a first corner and a second corner is elastically resonated by applying an alternating voltage to drive the moving element in the forward and reverse directions. An ultrasonic motor that
In the piezoelectric vibrator, a mode shape by the resonance is asymmetric between the first corner portion and the second corner portion,
In the piezoelectric vibrator, one main surface is divided into a plurality of regions, drive electrodes are individually formed in the regions, and a ground electrode is formed on the other main surface.
When the alternating voltage is applied between any one of the plurality of drive electrodes selected from the plurality and the ground electrode, the corner portion causing the maximum displacement due to the resonance is the first corner portion or the second corner portion. As well as
A first urging portion that drives the moving element in the forward direction and a second urging portion that drives the moving element in the reverse direction are provided in the first corner portion and the second corner portion, respectively. An ultrasonic motor characterized by that.   The ultrasonic motor according to claim 1, wherein the drive electrode includes a common drive electrode to which the alternating voltage is constantly applied and a selective drive electrode to which the alternating voltage is selectively applied.   The ultrasonic motor according to claim 2, wherein the selective drive electrodes are formed in a region where the first corner portion is formed and a region where the second corner portion is formed.   The ultrasonic motor according to claim 2, wherein the common drive electrode is formed in both the region where the first corner portion is formed and the region where the second corner portion is formed.   The one main surface is divided into four regions divided by a straight line parallel to the side of the rectangular piezoelectric vibrator, and the common drive electrode or the selective drive electrode is formed in the region, respectively. The ultrasonic motor according to claim 2.   The one main surface is divided into four regions by two diagonal lines of the rectangular piezoelectric vibrator, and the common drive electrodes and the selective drive electrodes are alternately arranged in the adjacent regions. The ultrasonic motor according to any one of claims 2 to 4. The first urging portion is provided at two first corner portions sandwiching one of the selective drive electrodes,
The ultrasonic motor according to claim 6, wherein the second urging portion is provided at two second corner portions sandwiching the other selected drive electrode. The piezoelectric vibrator has a rectangular shape, and includes the first corner portion and the second corner portion adjacent to each other, and the other two corner portions,
The one selective drive electrode for driving the first urging portion is formed in a region different from the region in which the first corner portion is formed,
The other selection drive electrode that drives the second urging portion is formed in a region different from a region in which the second corner portion is formed. The described ultrasonic motor.

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