JP5124429B2 - Ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor that drives a driven body using ultrasonic vibration as a driving force source.

  For example, Patent Document 1 below proposes an ultrasonic motor that rotates a rotor by synthesizing longitudinal vibration and torsional vibration of a vibrator to generate elliptical vibration. FIG. 1 of Patent Document 1 below shows an exploded perspective view of the vibrator, in which a plurality of piezoelectric elements are inserted between elastic bodies cut obliquely with respect to the vibrator axis direction. It has become. In addition, the positive electrode of the piezoelectric element is divided into two parts, which are referred to herein as A phase and B phase, respectively.

Here, by applying an alternating voltage having the same phase to the A phase and the B phase, longitudinal vibration can be generated in the rod-shaped vibrator. Further, torsional vibration can be generated in the rod-shaped vibrator by applying alternating voltages having opposite phases to the A phase and the B phase. The groove position of the vibrator is adjusted so that the resonance frequency of the longitudinal vibration and the resonance frequency of the torsional vibration are substantially matched. When alternating voltages having different π / 2 phases are applied to the A phase and the B phase, longitudinal vibration and torsional vibration are generated simultaneously, and elliptical vibration can be generated on the upper surface of the rod-shaped elastic body. By pressing the rotor against the upper surface of the rod-shaped elastic body, the rotor can be rotated clockwise (CW direction) or counterclockwise (CCW direction).
JP-A-9-117168

  However, as shown in FIG. 1, the ultrasonic motor described in Patent Document 1 requires a piezoelectric element and an elastic body. The elastic body must be cut obliquely. There was a problem such as having to provide a groove portion. Therefore, there is a problem that the configuration of the vibrator becomes very complicated as a whole.

  Therefore, the present invention has been made in view of the above-mentioned problems, and the object thereof is a single member, has a simple structure, does not require a groove or the like, and can be driven at a low voltage. To provide an ultrasonic motor that can easily excite longitudinal vibration and torsional vibration, forms elliptical vibration by synthesizing the longitudinal vibration and torsional vibration, and rotates the rotor by the elliptical vibration. .

  That is, the present invention provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. An ultrasonic motor including at least a rotor that is driven to rotate about the vibrator, wherein the vibrator is composed of a single piezoelectric element, and the direction of polarization of the piezoelectric element includes the direction of the central axis Is substantially in the in-plane direction, and the angle ε formed with the direction of the central axis is set so as to satisfy 0 <ε <π / 2 and expands and contracts in the rotational axis direction of the vibrator. The longitudinal primary resonance vibration and the torsional tertiary resonance vibration having the rotation axis as the torsion axis are combined to form the elliptical vibration to rotate the rotor.

  The present invention also provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. An ultrasonic motor including at least a rotor that is driven to rotate about the vibrator, wherein the vibrator is composed of a single piezoelectric element, and the direction of polarization of the piezoelectric element includes the direction of the central axis The angle ε between the side surfaces of the vibrator and the direction of the central axis is set so as to satisfy 0 <ε <π / 2, and the longitudinal direction of the vibrator expands and contracts in the rotational axis direction. By combining the primary resonance vibration and the torsional secondary resonance vibration having the rotation axis as the torsion axis, the elliptical vibration is formed to rotate the rotor.

  Furthermore, the present invention provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. An ultrasonic motor comprising at least a rotor that is driven to rotate about a rotary shaft, wherein the vibrator is formed by laminating a plurality of piezoelectric sheets each having an interdigitated electrode pattern formed thereon, In this case, a first driving cross finger electrode is provided in the vicinity of the first node position of the torsional vibration of the plane parallel to the rotation axis, and the finger direction of the cross finger electrode and the central axis The angle θ with respect to the direction is provided under the condition of 0 <θ <π / 2, and is electrically connected in parallel with the driving electrode in the vicinity of the second node position of the torsional vibration of the plane parallel to the rotation axis. A second driving cross finger electrode is provided, and the finger direction of the cross finger electrode and the above An angle φ formed with the direction of the core axis is provided under the condition of π / 2 <φ <π, and a vibration detecting cross finger thunder pole is provided in the vicinity of the third node position of the torsional vibration in the plane parallel to the rotation axis. An angle Ψ formed by the finger direction of the second driving cross-finger electrode and the direction of the central axis is provided under a condition other than 0, π / 2, π, and The elliptical vibration is formed by synthesizing the longitudinal primary resonance vibration expanding and contracting in the rotation axis direction and the torsional tertiary resonance vibration having the rotation axis as a torsion axis.

  The present invention provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. In an ultrasonic motor including at least a rotor that is driven to rotate as a rotating shaft, the vibrator is formed by laminating a plurality of first piezoelectric sheets on which a driving interdigital electrode pattern is formed. In the first piezoelectric sheet, a first driving cross finger electrode is provided in the vicinity of a first node position of torsional vibration of a plane parallel to the rotation axis. An angle θ between the finger direction and the direction of the central axis is provided under the condition of 0 <θ <π / 2, and a vibration detection intersection is provided in the vicinity of the second node position of the torsional vibration of the plane parallel to the rotation axis. Finger electrodes are provided, the finger direction of the vibration detecting cross finger electrode and the direction of the central axis Is provided under conditions other than 0, π / 2, and π, and a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional secondary with the rotation axis as a torsion axis. The elliptical vibration is formed by synthesizing resonance vibration.

  The present invention provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. At least a rotor driven to rotate as a rotation axis, and by synthesizing a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional tertiary resonance vibration having the rotation axis as a torsion axis. In the ultrasonic motor formed with elliptical vibration, the vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which driving internal electrode patterns are formed. In the first piezoelectric sheet, the left finger side of the driving cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the left finger internal electrode Between the longitudinal direction of the shaft and the direction of the rotation axis. An angle θ is provided under the condition of 0 <θ <π / 2. In the second piezoelectric sheet, the right side of the driving interdigital electrode is located near the node position of torsional vibration of a plane parallel to the rotation axis. A finger side is provided, and an angle formed by a longitudinal direction of the internal electrode on the right finger side and the direction of the rotation axis is provided at the same angle as the internal electrode on the left finger side, and the first piezoelectric sheet The driving internal electrodes of the second piezoelectric sheet and the driving internal electrodes of the second piezoelectric sheet substantially form a pair of cross finger electrodes, and the driving internals of the first piezoelectric sheet and the second piezoelectric sheet are formed. A part of the electrode extends to the end portion of each piezoelectric sheet, is electrically connected to each external electrode, and extends from the substantially central portion in the stacking direction to the extending portion of the driving internal electrode of the first piezoelectric sheet And the extending portions of the driving internal electrodes of the second piezoelectric sheet are different from each other. Characterized in that it comprises connected to the poles.

  Further, the present invention provides a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a center that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. At least a rotor that is driven to rotate about an axis as a rotation axis, and a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional secondary resonance vibration that uses the rotation axis as a torsion axis. In the ultrasonic motor formed by the above elliptical vibration, the vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which driving internal electrode patterns are formed. In the first piezoelectric sheet, the left finger side of the driving cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the left Longitudinal direction of the internal electrode on the finger side and the rotation axis The angle θ formed with the direction is provided under the condition of 0 <θ <π / 2. In the second piezoelectric sheet, the driving intersection is located near the node position of the torsional vibration of the plane parallel to the rotation axis. The right finger side of the finger electrode is provided, and the angle formed by the longitudinal direction of the internal electrode on the right finger side and the direction of the rotation axis is provided at the same angle as the internal electrode on the left finger side. A pair of interdigital electrodes are substantially formed by the driving internal electrode of one piezoelectric sheet and the driving internal electrode of the second piezoelectric sheet, and the first piezoelectric sheet and the second piezoelectric sheet. A portion of the internal electrodes of the first piezoelectric sheet extend to the end portions of the piezoelectric sheets, and are electrically connected to the external electrodes. The internal electrodes for driving the first piezoelectric sheet extend from the substantially central portion in the stacking direction. The protruding portion and the extending portion of the driving internal electrode of the second piezoelectric sheet are different from each other. Characterized by comprising connected to the external electrode.

  The present invention also relates to a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a center that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. At least a rotor that is driven to rotate about an axis as a rotation axis, and synthesizing a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional tertiary resonance vibration that uses the rotation axis as a torsion axis. In the ultrasonic motor configured to form the elliptical vibration, the vibrator includes a plurality of first piezoelectric sheets and a plurality of second piezoelectric sheets on which vibration detection internal electrode patterns are formed. In the first piezoelectric sheet, the left finger side of the vibration detecting cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, The longitudinal direction of the internal electrode on the left finger side and the The angle θ formed with the direction of the axis of rotation is provided under the condition of 0 <θ <π / 2. In the second piezoelectric sheet, in the vicinity of the node position of the torsional vibration of the plane parallel to the rotation axis The right finger side of the vibration detecting cross finger electrode is provided, and the angle formed by the longitudinal direction of the internal electrode on the right finger side and the direction of the rotation axis is provided at the same angle as the internal electrode on the left finger side. A vibration detection internal electrode of the first piezoelectric sheet and a vibration detection internal electrode of the second piezoelectric sheet substantially forming a pair of vibration detection cross finger electrodes, A part of the vibration detection internal electrode of the piezoelectric sheet and the second piezoelectric sheet extends to the end of each piezoelectric sheet, and is electrically connected to each external electrode. Vibration detection of the extension part of the drive electrode of the first piezoelectric sheet and the second piezoelectric sheet Extending portions of use internal electrodes is characterized by comprising respectively connected to different external electrodes.

  Furthermore, the present invention relates to a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and a central axis that is in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator. The elliptical vibration is synthesized by synthesizing a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional secondary resonance vibration having the rotation axis as a torsion axis. In the formed ultrasonic motor, the vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets each having a vibration detection internal electrode pattern formed thereon. In the first piezoelectric sheet, the left finger side of the vibration detecting cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the length of the left finger internal electrode is long. The angle between the direction and the direction of the axis of rotation θ is provided under the following conditions: 0 <θ <π / 2 In the second piezoelectric sheet, the vibration detecting cross finger is located near the node position of the torsional vibration of the plane parallel to the rotation axis. The right finger side of the electrode is provided, the angle formed by the longitudinal direction of the right finger internal electrode and the direction of the rotation axis is provided at the same angle as the left finger internal electrode, and the vibration of the first piezoelectric sheet The detection internal electrode and the vibration detection internal electrode of the second piezoelectric sheet substantially form a pair of vibration detection cross finger electrodes, and vibrations of the first piezoelectric sheet and the second piezoelectric sheet are formed. A part of the detection internal electrode extends to the end of each piezoelectric sheet, and is electrically connected to each external electrode, and the drive electrode of the first piezoelectric sheet extends from the substantially central portion in the stacking direction. And the extension part of the internal electrode for vibration detection of the second piezoelectric sheet are further separated from each other. It is connected to the external electrodes, characterized by comprising.

  According to the present invention, it is composed of a single member, has a simple structure, does not require a groove, etc., can be driven at a low voltage, and can easily excite longitudinal vibration and torsional vibration. By combining the longitudinal vibration and the torsional vibration, elliptical vibration is formed, and an ultrasonic motor that rotates the rotor by the elliptical vibration can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is an external perspective view showing an ultrasonic motor according to the first embodiment of the present invention. 2A and 2B show the laminated piezoelectric element in a state in which the friction contact member is bonded, in which FIG. 2A is an external perspective view, and FIG. 2B is a top view. 3A and 3B show the configuration of the laminated piezoelectric element 11. FIG. 3A is a plan view seen from above, FIG. 3B is an exploded perspective view, and FIG. 3C is a perspective view seen from the α direction of FIG. (D) is a view of the laminated piezoelectric element 11 as viewed from the γ direction of (a), (e) is a view of the laminated piezoelectric element 11 as viewed from the δ direction of (a), and (f) is a view of (d). The figure which showed the state where the external electrode was attached to the laminated piezoelectric element, (g) is the figure which showed the state where the external electrode was attached to the laminated piezoelectric element of (e), (h) is the laminated piezoelectric element of (d). The figure which showed the other example in which the external electrode was attached to the element, (i) is the figure which showed the other example in which the external electrode was attached to the laminated piezoelectric element of (e).

  The ultrasonic motor 10 includes a laminated piezoelectric element (vibrator) 11 constituting a vibrator, friction contact members 12a and 12b, an external electrode 13, a rotor 15, a bearing 16, a spring 17, and a spring holding ring. 18, a vibrator holder 20, a shaft fixing ring 21, and a shaft 22.

  In all the following embodiments including the first embodiment, the vibrator 11 is configured by laminating a plurality of piezoelectric elements.

  The friction contact members 12 a and 12 b are bonded to a surface orthogonal to the longitudinal direction of the laminated piezoelectric element 11 so as to come into contact with the rotor 15. However, the friction contact members 12a and 12b are not necessarily required. 1 and 2A, four external electrodes 13 are provided on the left side of the drawing, and four external electrodes 13 are also provided on the right side although not shown.

  The rotor 15 rotates by being pressed by the prismatic vibrator 11 and the top surface of the vibrator 11. The bearing 16 includes a bearing inner ring to which the shaft 22 is fixed, and a bearing outer ring that is fixed to the inner periphery of the rotor 15. The spring 17 is an elastic member for applying a pressing force to the bearing inner ring. The spring retaining ring 18 is for controlling the amount of contraction of the spring 17.

  The vibrator holder 20 is fixed to the substantially central portion of the vibrator 11 and holds the shaft 22. As will be described later, this central portion geometrically substantially coincides with the node of the longitudinal primary vibration of the vibrator 11 and the node of the center of the torsional tertiary vibration. The vibrator holder 20 is made of an alumite-treated aluminum material or an insulating-treated metal material, and is integrally formed. The lower part of the vibrator holder 20 has a U-shape so as to sandwich the vibrator 11 from the side surface thereof, and the upper surface has a flat plate shape with a through hole formed in the center. A shaft 22 having a screw thread in part is inserted from the through hole.

  The shaft fixing ring 21 is for fixing the shaft 22 to the vibrator holder 20. As described above, the shaft 22 is inserted into the bearing 16, the spring holding ring 18, and the shaft fixing ring 21. A rotor 15 is rotatably fixed to the outer periphery of the bearing 16. Further, a spring 17 is inserted between the spring holding ring 18 and the bearing 16, and the spring holding ring 18 is rotated and adjusted so that an appropriate pressing force acts between the rotor 15 and the vibrator 11. Yes. After this adjustment, the spring retaining ring 18 is fixed to the shaft 22 using an adhesive.

  Next, the internal electrode configuration of the laminated piezoelectric element 11 of the ultrasonic motor 10 in the first embodiment will be described.

  The laminated piezoelectric element 11 is configured by laminating thin piezoelectric sheets such as lead zirconate titanate (hereinafter referred to as PZT) on which a predetermined internal electrode pattern is formed.

  FIG. 3A is a view of the multilayer piezoelectric element 11 as viewed from above, and side surfaces in four directions are indicated by arrows as α, β, γ, and δ, respectively. FIG. 3B shows an example of a piezoelectric sheet and internal electrode patterns.

  Each of the piezoelectric sheets is made of a PZT material having a thickness of about 10 μm to 100 μm. The piezoelectric sheet 1 (hereinafter referred to as piezoelectric sheet (1)) 25a has an internal electrode pattern 1 (hereinafter referred to as internal electrode pattern (1)). The internal electrode pattern 2 (hereinafter referred to as internal electrode pattern (2)) 26b is printed on the piezoelectric sheet 2 (hereinafter referred to as piezoelectric sheet (2)) 25b. On the piezoelectric sheet (1) 25a, as shown in the drawing, crossed finger internal electrodes are printed at three locations as the internal electrode pattern (1) 26a.

  The material of the interdigitated internal electrode is made of, for example, a silver palladium alloy, the width is set to a range of about 0.1 mm to 1 mm, and the insulation width therebetween is also set to a range of about 0.1 mm to 1 mm. Moreover, thickness is 2-3 micrometers, for example.

  Here, the cross finger electrode refers to an electrode in which a + phase electrode and a-phase electrode are alternately combined. In FIG. 3 (b), the cross finger electrodes have two pairs of cross finger electrodes for ease of viewing. However, in order to make the area as large as possible in the plane, in FIG. As shown, more pairs of crossed finger electrodes may be configured to be formed on one side of the plane. In the present invention, the cross finger electrode is referred to as a cross finger internal electrode because it is provided inside the laminated piezoelectric element.

In FIG. 3B, the cross finger electrode has an angle formed by the height direction (indicated by a broken line) and the finger direction of the cross finger internal electrode. Finger electrode)
0 <θ <π / 2
And Since the polarization direction ε is a direction orthogonal to the direction of the fingers of the cross finger electrode, as indicated by the broken line in the figure,
0 <| ε | <π / 2
It is.

Also, the angle formed by the second cross finger electrode (second cross finger electrode) from the top of the figure is φ, as shown in the figure,
π / 2 <φ <π
It has become.

  The second cross finger electrode is electrically connected to the first cross finger electrode in parallel, and a part of the second cross finger electrode extends to the end of the piezoelectric sheet. These cross finger electrodes function as drive cross finger electrodes. The angles θ and φ may be set in the opposite range.

As shown in the figure, the angle formed by the third cross finger electrode (third cross finger electrode) from the top in the figure is ψ, which is a value other than 0, π / 2, and π. In form,
0 <ψ <π / 2
It is said. The third cross finger electrode has a function as a vibration detection electrode.

  The n piezoelectric sheets (1) 25a on which the internal electrode patterns (2) 26a are printed are stacked, and then the piezoelectric sheets (2) 25b on which the n internal electrode patterns (2) 26b are similarly printed. Laminated. The difference between the piezoelectric sheet (2) 25b and the piezoelectric sheet (1) 25a is the position of the electrode extending to the end as shown in FIG. 3 (b). The configuration and position of the interdigital electrode itself are exactly the same. Finally, a piezoelectric sheet 3 (hereinafter referred to as a piezoelectric sheet (3)) 25c on which no electrodes are printed is laminated on the piezoelectric sheet (2) 25b.

  Therefore, the total number of laminated piezoelectric elements 11 is 2n + 1, which is an odd number.

  FIG. 3C is a view of the multilayer piezoelectric element 11 as viewed from the front.

As will be described later, in this embodiment, torsional tertiary vibration and longitudinal primary vibration are used. Central portion of the upper interdigital electrode is provided in the upper section positions 35 ₂ near the torsional tertiary vibration, the central portion of the central portion interdigital electrodes, and the longitudinal primary vibration at the center section located near the torsional tertiary vibration provided node position ₃₅₁ near the central portion of the lower interdigital electrode is provided on the lower section position 35 ₃ near the torsional tertiary vibration.

3D and 3F are views of the vibrator 11 viewed from the γ direction of FIG. In FIG. 3B, the upper cross finger electrode and the central cross finger electrode 27a _{1 of} the internal electrode pattern (1) 26a are extended to the end in the left direction to form the internal electrode exposed portion 29a _1. ing. The internal electrode exposed portion 29a ₁ is joined to the external electrode A + phase 13a ₁ . Similarly, in FIG. 3B, the upper cross finger electrode and the central cross finger electrode 27b _{1 of} the internal electrode pattern (2) 26b are extended to the end in the left direction, and the internal electrode exposed portion 29b _1. Is formed. The internal electrode exposed portion 29b ₁ is joined to the external electrode B + phase 13b ₁ .

Further, the lower cross finger electrode 28a _{1 of} the internal electrode pattern (1) 26a is extended to the end in the left direction to form an internal electrode exposed portion 30a ₁ . This internal electrode exposed portion 30a ₁ is joined to the external electrode C + phase 13C ₁ . Further, the lower cross finger electrode 28b _{1 of} the internal electrode pattern (2) 26b extends to the end in the left direction to form an internal electrode exposed portion 30b ₁ . The internal electrode exposed portion 30b ₁ is joined to the external electrode D + phase 13d ₁ .

FIGS. 3E and 3G are views of the vibrator 11 viewed from the δ direction of FIG. In FIG. 3B, the upper cross finger electrode and the central cross finger electrode 27a _{2 of} the internal electrode pattern (1) 26a are extended to the end in the right direction to form an internal electrode exposed portion 29a _2. ing. The internal electrode exposed portion 29a ₂ is joined to the external electrode A-phase 13a ₂ . Similarly, in FIG. 3B, the upper cross finger electrode and the central cross finger electrode 27b _{2 of} the internal electrode pattern (2) 26b are extended to the right end to the inner electrode exposed portion 29b _2. Is formed. The internal electrode exposed portion 29b ₂ is joined to the external electrode B-phase 13b ₂ .

Further, the lower interdigital electrode 28a _{2 of} the internal electrode pattern (1) 26a is extended to the end in the right direction to form an internal electrode exposed portion 30a ₂ . This internal electrode exposed portion 30a ₂ is joined to the external electrode C-phase 13C ₂ . Further, the lower cross finger electrode 28b _{2 of} the internal electrode pattern (2) 26b extends rightward to the end portion to form an internal electrode exposed portion 30b ₂ . The internal electrode exposed portion 30b ₂ is joined to the external electrode D-phase 13d ₂ .

  Thus, if the electrode pattern is designed to provide equivalent vibration characteristics with a cross section cut by a virtual center line as a boundary, the position of the external electrode is as shown in FIGS. 3 (f) and 3 (g). Even if they are arranged at different positions, the vibration characteristics are not changed, so that they are substantially symmetrical.

  Next, a method for producing the multilayer piezoelectric element 11 will be described.

Plural sheets of the internal electrode pattern (1) 26a printed on the piezoelectric sheet (1) 25a before firing, and similarly, a plurality of sheets of the internal electrode pattern (2) 26b printed on the piezoelectric sheet (2) 25b. A sheet is prepared. First, after n sheets of piezoelectric sheets (1) 25a are stacked, n sheets of piezoelectric sheets (2) 25b are stacked, and further one sheet of piezoelectric sheet (3) 25c with no internal electrodes printed thereon is stacked. . Then, after being pressed and cut into a predetermined size, firing is performed at a predetermined temperature. Thereafter, the external electrodes 13a ₁ , 13a ₂ , 13b ₁ , 13b ₂ , 13c ₁ , 13c ₂ , 13d ₁ and 13d ₂ are printed and baked at predetermined positions.

The external electrode is not limited to the example described above. In the above-described example, the internal electrodes exposed portions 29a ₁ , 29a ₂ , 29b ₁ , 29b ₂ , 30a ₁ , 30a ₂ , 30b ₁ , 30b ₂ and the external electrodes 13a ₁ , 13a ₂ , 13b ₁ having substantially the same width. , 13b ₂ , 13c ₁ , 13c ₂ , 13d ₁ , 13d ₂ are provided. However, for example, as shown in FIGS. 3 (h) and 3 (i), the laminated piezoelectric element 11 may be provided over the entire short side direction.

  FIG. 3 (h) is a view of the main vibrator 11 viewed from the γ direction of FIG. 3 (a), and FIG. 3 (i) is a view of the main vibrator 11 viewed from the δ direction of FIG. 3 (a).

That is, for the internal electrode exposed portions 29a ₁ , 29a ₂ , 29b ₁ , 29b ₂ , 30a ₁ , 30a ₂ , 30b ₁ , 30b ₂ , the external electrodes 13a ₃ , 13a ₄ , 13b including the internal electrode exposed portions are used. ₃ , 13 b ₄ , 13 c ₃ , 13 c ₄ , 13 d ₃ , and 13 d ₄ are provided to be joined.

  Next, polarization will be described with reference to FIG.

  FIG. 5 is a cross-sectional view including the polarization direction shown along line BB ′ in FIG. 3B and perpendicular to the side surface.

  In FIG. 5, the polarization vector indicated by the arrow P is polarized toward the other pole (−) with a slight bulge from the pole (+) on one side to the center. This vector also coincides with the electric field vector. Further, the distance between adjacent internal electrodes is, for example, 300 μm, and the distance between the + and − poles (in the thickness direction of the piezoelectric sheet) is, for example, 100 μm.

  Next, the operation of the vibrator 11 will be described.

  As shown in FIG. 6A, the shape of the vibrator 11 is a rectangular parallelepiped, and the dimensions of the sides a, b, and c are set to appropriate values, so that the resonance frequency of the longitudinal primary vibration mode is The resonance frequency of the torsional secondary vibration mode or the torsional tertiary vibration mode is made to substantially coincide.

6B shows the torsional primary vibration mode, FIG. 6C shows the longitudinal primary vibration mode, FIG. 6D shows the torsional secondary vibration mode, and FIG. 6E shows the torsional tertiary vibration mode. It is the figure which showed the vibration state schematically. A solid line indicates the shape of the vibrator 11 before vibration, and a broken line indicates the shape of the vibrator 11 after vibration. In the figure, 35 ₁ , 35 ₂ , 35 ₃ , 35 ₄ , and 35 ₅ are positions corresponding to the vibration nodes of the vibrator 11, and 35 ₄ and 35 ₅ are the upper node positions of the torsional secondary vibration and the torsion. This is the lower node position of the secondary vibration.

  Here, each side a, b, and c of the rectangular parallelepiped is defined. Now, let the direction of the side c be the direction of vibration in the longitudinal primary vibration mode and the axial direction of torsion of torsional vibration. Further, the direction orthogonal to the side c is defined as the direction of the side a and the direction of the side b. Here, the length ratio of each rectangular cross section perpendicular to the axis parallel to the side c along the side c is a <b <c, a is referred to as a short side, and b is referred to as a long side. This will be described below.

  FIG. 7 is a diagram showing the resonance frequency of each mode in various rectangular ratios in which the side c is constant and the horizontal axis is the length of the short side / the length of the long side (a / b). is there. As can be seen from the figure, when a / b is changed, the resonance frequency of the longitudinal primary vibration mode does not depend on a / b and takes a substantially constant value. However, the resonance frequency of torsional vibration monotonously increases as the a / b value approaches 1. The resonance frequency of the torsional primary vibration mode has no condition that matches the resonance frequency of the longitudinal primary vibration mode regardless of the value of a / b.

  However, it is clear that the resonance frequency of the torsional secondary vibration mode matches when the a / b value is around 0.6. Further, it is clear that the resonance frequency of the torsional tertiary vibration mode matches when the a / b value is around 0.3. Therefore, in this embodiment, each dimension of the vibrator 11 is set so that a / b is approximately 0.3.

  In the present embodiment, the dimension of each side a × b × c of the vibrator 11 is, for example, 10 × 3 × 20 mm.

  As shown in FIG. 3 (b), the first vibration, which is the outermost layer of the piezoelectric sheet (1), and the piezoelectric sheet (2) of the outermost layer laminated at the end of the piezoelectric sheet (2) are used for this vibration. A method for driving the child 11 will be described.

  First, the operation of the vibrator 11 using the driving cross finger electrodes will be described.

  First, an alternating voltage corresponding to the resonance frequency of longitudinal primary vibration or torsional tertiary vibration is applied to the A phase (A + phase, A− phase). In FIG. 3B, the force generated in the vicinity of the upper cross finger electrode due to the inverse piezoelectric effect at that time is displayed as a vector.

  The force F shown in FIG. 3B is an alternating force, and when the force is vector-decomposed, F1 and F2 are obtained. As is clear from the figure, the force F1 is a force that excites longitudinal vibration. Further, as apparent from the figure, the force F2 becomes a force that generates a torsional tertiary vibration.

  Next, an alternating voltage having the same frequency as that of the A phase is also applied to the B phase (B + phase, B− phase). In FIG. 3 (b), the force generated in the vicinity of the upper cross finger electrode of the piezoelectric sheet (2) 25b located at the outermost surface at that time is displayed as a vector.

  The force F ′ shown in FIG. 3B is an alternating force, and when the force is vector-decomposed, F1 ′ and F2 ′ are obtained. The force F1 ′ is a force that excites the longitudinal vibration as is apparent from the figure. Further, as apparent from the figure, the force F2 'becomes a force that generates a torsional tertiary vibration.

  Next, only the power generated when an alternating voltage of the above-mentioned frequency having the same phase is simultaneously applied to the A phase and the B phase will be considered. In this case, as shown in FIG. 3B, the forces F2 and F2 'cancel each other, and the torsional tertiary vibration does not occur, but only the longitudinal primary vibration occurs.

  Further, when an alternating voltage having the above-mentioned frequency having the opposite phase (phase difference π) is applied to the A phase and the B phase at the same time, the forces F1 and F1 ′ cancel each other, no longitudinal primary vibration occurs, and the torsional tertiary Only vibration will occur.

  Next, consider a case where a phase difference between 0 and π is simultaneously given to the A phase and the B phase. In this case, the longitudinal primary vibration and the torsional tertiary vibration occur simultaneously, and these vibrations are synthesized. At this time, as shown in FIG. 2, the rotor 15 is rotated to the adhesion position of the frictional contact members 12a and 12b of the vibrator 11 in the clockwise direction (CW direction) or the counterclockwise direction (CCW direction). The elliptical vibration is formed. When elliptical vibration is generated at the position of the frictional contact members 12a and 12b of the vibrator 11, the pressed rotor 15 uses the shaft 22 as a rotation axis (or central axis) according to the rotation direction of the elliptical vibration. The rotating operation is performed in the clockwise direction (CW direction) or counterclockwise direction (CCW direction).

  In addition, since the direction of twist is reversed about the remaining pair of driving interdigital electrodes, the direction of the interdigital electrodes is set to be an obtuse angle. Since the driving principle is the same, the description is omitted.

  Next, the operation of the lower vibration detecting cross finger electrode shown in FIG. 3B will be described.

  When longitudinal primary vibration or torsional tertiary vibration occurs, electric charges are generated on the surface of the interdigitated electrode due to the piezoelectric effect. The charge is observed as a voltage of the C phase (between the C + phase and the C− phase) or a voltage of the D phase (between the D + phase and the D− phase). In the operation with the driving cross-finger electrode, force is generated by the driving voltage due to the above-described reverse piezoelectric effect, but on the contrary, a charge or voltage is generated by mechanical distortion.

  Therefore, when only longitudinal primary vibration is occurring, the C phase and the D phase are connected in parallel in order (the C + phase and the D + phase are connected, and the C− phase and the D− phase are connected: defined as a parallel forward connection phase). As a result, a signal proportional to the magnitude and phase of the longitudinal primary vibration is obtained as the voltage generated in the meantime. However, when the C phase and the D phase are reversely connected in parallel (the C + phase and the D− phase are connected and the C− phase and the D + phase are connected: defined as a parallel reverse connection phase), no signal is output.

  On the other hand, when only the torsional tertiary vibration occurs, the C phase and D phase are connected in reverse (C + phase and D− phase are connected, and C− phase and D + phase are connected). As the voltage, a signal proportional to the magnitude and phase of the torsional tertiary vibration is obtained. However, when the C phase and the D phase are connected in parallel in order (the C + phase and the D + phase are connected, and the C− phase and the D− phase are connected), no signal is output.

  Therefore, by selecting the connection between the C phase and the D phase, it is possible to independently detect the longitudinal primary vibration or the torsional tertiary vibration.

  Next, a method of driving a motor using such a vibration detection phase (C phase, D phase) will be described.

  The phase difference between the phase of the A-phase or B-phase signal that is the driving phase and the phase of the vibration detection phase (for example, the C-phase and the D-phase are reversely connected in parallel) is predetermined during the resonance frequency operation of the torsional tertiary vibration It is known to take the value Ω. Therefore, in this case, by adjusting the frequency so that the phase difference between the drive phase and the detection phase is always Ω, the temperature is increased due to the heat generated by the motor itself, the resonance frequency changes due to changes in the ambient temperature, and the load. Even if there is a change in the resonance frequency due to fluctuations, it can always be driven near the torsional third-order resonance frequency. Therefore, it is possible to drive efficiently at always the optimum frequency. This is also possible with the same concept when driving near the longitudinal primary resonance frequency.

  As described above, according to the first embodiment, a vibrator can be configured by a single layered piezoelectric element, and the motor has a simple shape such as a rectangular parallelepiped. Furthermore, since this embodiment has a laminated structure, low voltage driving is possible. Further, in the conventional vertical / torsion motor, the groove for adjusting the frequency of the torsional vibration is indispensable, but this is not necessary in the present embodiment. In addition, since a vibration detection electrode is also provided, it is possible to always drive at an optimum frequency.

  Furthermore, the vibrator according to the present embodiment has a rectangular parallelepiped shape in which a cross section perpendicular to the rotation axis has a predetermined ratio, and therefore, a multilayer piezoelectric element can be created using a piezoelectric element laminating technique that is usually used. It can be done easily.

(First modification)
Next, a first modification of the first embodiment of the present invention will be described.

  FIGS. 8A and 8B show the configuration of the laminated piezoelectric element 11 according to the first modification of the first embodiment of the present invention. FIG. 8A is an exploded perspective view, and FIG. The figure which looked at the piezoelectric element 11 from the left direction, (c) is the figure which looked at the laminated piezoelectric element 11 of (a) from the right direction.

As shown in FIG. 8 (a), the electrode pattern shapes of the internal electrode pattern (1) 26a and the internal electrode pattern (2) 26b in the first embodiment described above are shown in FIG. Cross finger electrodes 37a ₁ and 37a ₂ , upper cross finger electrodes and central cross finger electrodes 37b ₁ and 37b ₂ , and lower cross finger electrodes 38a ₁ and 38a ₂ and lower cross finger electrodes 38b ₁ and 38b ₂ , They are exactly the same. In this case, as shown in FIGS. 8B and 8C, the external electrode is divided into two equal parts at exactly half positions, and the external electrodes 40a ₁ , 40a ₂ , 40b ₁ , 40b ₂ , 40c ₁ , 40c ₂ , 40d ₁ , 40d ₂ are formed.

  According to the first modification, there is an effect that only one type of internal electrode pattern is required.

(Second modification)
Next, a second modification of the first embodiment of the present invention will be described.

  FIGS. 9A and 9B show a configuration of the laminated piezoelectric element 11 according to the second modification of the first embodiment of the present invention. FIG. 9A is an exploded perspective view, and FIG. 9B is a laminated view of FIG. It is the figure which looked at the piezoelectric element 11 from the bottom face side.

  This second modified example is a configuration example in the case where all of the three pairs of crossed finger electrodes are drive electrodes when focusing on, for example, one piezoelectric sheet of the first embodiment described above.

These three pairs of cross finger electrodes 42a ₁ , 42a ₂ and 42b ₁ , 42b ₂ are electrically connected in parallel, and the angles formed with the longitudinal direction of the upper cross finger electrodes are an acute angle, an obtuse angle, and an acute angle, respectively. This is because, as shown in FIG. 6, the torsional directions of the third torsional vibration are in the order of normal (reverse), reverse (normal), and normal (reverse) from the top.

Further, in the second modification, the external electrodes 43a ₁ , 43a ₂ , 43b ₁ , 43b are provided corresponding to the positions where the internal electrodes are led out only at the lower part of FIG. ₂ is provided only on the lower surface of the vibrator 11 as shown in FIG.

  According to the second modified example, since all the internal electrodes are used as driving electrodes, a motor with high power can be realized. Further, since the external electrode is provided only on the bottom surface, for example, when connecting a flexible substrate (not shown), there is an advantage that the configuration is simple because only one surface is required.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  FIG. 10 is an exploded perspective view showing the configuration of the multilayer piezoelectric element of the ultrasonic motor according to the second embodiment of the present invention.

  This second embodiment differs from the first embodiment described above only in the configuration of the vibrator. Therefore, the configuration of the vibrator will be described here, and the basic configuration and operation of other ultrasonic motors are the same as those in the first embodiment described above. Are denoted by the same reference numerals, and illustration and detailed description thereof are omitted.

  In the present embodiment, the dimension of each side a × b × c of the vibrator is, for example, 10 × 3 × 20 mm.

In FIG. 10, the internal electrode pattern of the piezoelectric sheet (1) 25a is printed with only the right finger of the cross finger electrode. This is called a crossed finger right finger electrode. As shown in the figure, the cross finger right finger electrode is an upper cross finger right finger electrode, a central cross finger right finger electrode 45a ₁ , and a lower cross finger right finger electrode 46a ₁ from the top of the figure. The center positions of these crossed finger right finger electrodes substantially correspond to the node positions of the torsional tertiary vibration (details will be described later). In addition, the inclination of the upper cross finger right finger electrode is set in the same manner as in the first embodiment described above. The inclination of the center intersecting finger right finger electrode is also set in the same manner as in the first embodiment.

The upper cross finger right finger electrode and the central cross finger right finger electrode 45a ₁ function as drive internal electrodes, and are connected by electrodes as shown in the drawing, and a part thereof is led out to the end. Further, a lower cross finger right finger electrode 46a ₁ is laid out as shown in the figure below, and the angle formed is the same as in the first embodiment described above. The lower crossing finger right finger electrode 46a ₁ functions as a vibration detection electrode, and a part thereof is led out to the end of the piezoelectric sheet.

  On the other hand, the internal electrode pattern of the piezoelectric sheet (2) 25b is printed with only the left finger of the interdigitated electrode. This is referred to as a cross finger left finger electrode. The cross finger left finger electrode of the piezoelectric sheet (2) 25b is positioned so as to form a pair of cross finger electrodes with the cross finger right finger electrode of the piezoelectric sheet (1) 25a when the vibrator 11 is seen through from the front. And printed.

As shown in the figure, the cross finger left finger electrode is an upper cross finger left finger electrode, a center cross finger left finger electrode 45a ₂ , and a lower cross finger left finger electrode 46a ₂ from the top of the figure. The center position of these cross finger left finger electrodes is made to correspond to the node position of the torsional tertiary vibration.

In the present embodiment, the upper cross finger left finger electrode and the central cross finger left finger electrode 45a ₂ function as drive internal electrodes and are connected by electrodes as shown in the drawing, and a part thereof is led out to the end. ing. Further, a lower cross finger left finger electrode 46a ₂ is laid out as shown in the figure and functions as a vibration detection electrode. A part of the electrode is led to the end of the piezoelectric sheet (2) 25b.

  The piezoelectric sheets (1) 25a and the piezoelectric sheets (2) 25b are alternately stacked. After the n (even number) sheets are stacked, the piezoelectric sheet 4 (hereinafter referred to as the piezoelectric sheet (4)) 25d and the piezoelectric sheet 5 ( Hereinafter, n sheets of piezoelectric sheets (5) are alternately stacked, and finally, a piezoelectric sheet (3) 25c without an electrode pattern is stacked on the top.

  Note that the piezoelectric sheet (4) 25d and the piezoelectric sheet (5) 25e have the same electrode pattern except for the positions where they are drawn to the end portions.

  Thereafter, external electrodes are formed, which are the same as those in the first embodiment described above, and thus description thereof is omitted here.

  The production method of the multilayer piezoelectric element 11 is also the same as that in the first embodiment described above, and thus the description thereof is omitted.

  FIG. 11 is a view showing a cross section including a direction perpendicular to the finger direction of the intersecting finger electrode and a lamination direction in order to show a polarization state inside the laminated piezoelectric element according to the second embodiment.

  Polarization is formed in the direction of ξ from one pole. The polarization vector has a slight bulge in the center and goes to the other pole. This vector also matches the vector of the electric field. Furthermore, by making this inclination ξ as small as possible, a vibrator with higher electromechanical conversion efficiency is obtained.

  In the second embodiment, both the method of driving the laminated piezoelectric element and the ultrasonic motor by the driving phase, and the method of detecting the vibration from the vibration detection and driving the motor at the optimum driving frequency are described above. Since this is the same as that of the above embodiment, the description of the operation is omitted here.

  As described above, according to the second embodiment, the same effect as that of the second embodiment described above is obtained, but the following effect is further obtained.

  That is, in the first embodiment described above, since the positive electrode and the negative electrode are present in the same layer, if there is a place where the electrode thickness is somewhat thick at the time of lamination, the portion is deformed at the time of pressing, and the gap between the electrodes is reduced. In the worst case, the electrodes may be short-circuited and the polarization operation may become impossible due to the high voltage. However, in the second embodiment, only electrodes of the same polarity exist in the same layer. , Such trouble can be eliminated.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.

  FIG. 12 is an external perspective view of an ultrasonic motor according to a third embodiment of the present invention, FIG. 13 is an external perspective view of a vibrator with a friction contact member bonded thereto, and FIG. 14 is an exemplary perspective view of the third embodiment. 1A is a plan view as viewed from above, FIG. 2B is an exploded perspective view, and FIG. 3C is a view when the multilayer piezoelectric element 11 is viewed from the γ direction of FIG. FIG. 4D is a view of the laminated piezoelectric element 11 as viewed from the δ direction of FIG.

  The ultrasonic motor 50 is formed in a longitudinal direction of the vibrator 51, a laminated piezoelectric element (vibrator) 51, friction contact members 53a and 53b bonded to a surface orthogonal to the longitudinal direction of the vibrator 51, and the vibrator 51. The shaft 56 is inserted into a through hole 52 to be described later, and includes a rotor 57, a bearing 58, a spring 59, and a spring holding ring 60 that are driven in contact with the frictional contact members 53a and 53b.

  A through hole 52 through which the shaft 56 is inserted is provided at the center of the vibrator 51 in the longitudinal direction (vertical direction in the figure). The shaft 56 has a substantially cylindrical shape, and is fixed with an adhesive at a substantially central portion of the through hole 52 of the vibrator 51 (not shown). The shaft 56 is formed such that only the central portion is slightly larger in diameter than the other portions. The shaft 56 is fixed in contact with the vibrator 51 only at the central portion of the through hole 52 of the vibrator 51, and other shaft portions are not in contact with the wall surface inside the through hole 52.

  Friction contact members 53a and 53b are bonded to one end face of the vibrator 51 (the face on which the rotor 57 is disposed). These frictional contact members 53a and 53b are formed in a rectangular parallelepiped shape, and are bonded to one end face of the vibrator 51 and to two portions where elliptical vibration is generated.

  The rotor 57 is made of alumina ceramics, and a bearing 58 is fitted in the center thereof. Therefore, the rotor 57 is placed in a state where a pressing force is applied to the frictional contact members 53 a and 53 b of the vibrator 51. The spring 59 is compressed by rotating the spring holding ring 60, whereby an appropriate pressure is applied between the rotor 57 and the frictional contact members 53 a and 53 b of the vibrator 51. The spring 59 is in contact with the inside of the bearing 58 only.

  Although not shown in the drawing, a screw is formed on a part of the shaft 56, and is coupled to the spring holding ring 60, which is also formed with a screw.

  As shown in FIGS. 12 and 13, external electrodes 54 are provided at four locations on the side surface of the vibrator 51, but external electrodes are provided at four locations on the side facing the transducer 51 (not shown). .

  In the third embodiment, the dimension of each side a × b × c of the vibrator 51 is, for example, 10 × 6 × 20 mm.

  Next, the configuration of the laminated piezoelectric element (vibrator) 51 in the third embodiment will be described.

  FIG. 14A is a view of the laminated piezoelectric element 51 as viewed from above, and side surfaces in four directions are indicated by arrows, α, β, γ, and δ, respectively. FIG. 14B shows an example of a piezoelectric sheet and internal electrode patterns.

  The vibrator 51 includes n thin piezoelectric sheets 1 (hereinafter referred to as piezoelectric sheet (1)) 61 on which a predetermined internal electrode pattern is formed, and n-1 having the same configuration as the piezoelectric sheet (1) 61. A thin piezoelectric sheet 2 (hereinafter referred to as a piezoelectric sheet (2)) 62 is laminated on both sides of a single piezoelectric sheet 3 (hereinafter referred to as a piezoelectric sheet (3)) 63 in which a through hole 52 is formed. Further, a thin piezoelectric sheet 4 (hereinafter referred to as a piezoelectric sheet (4)) 64 in which no internal electrode pattern is formed is laminated outside the piezoelectric sheet 62.

  Hereinafter, differences from the above-described first embodiment will be described.

  On the piezoelectric sheet (1) 61 and the piezoelectric sheet (2) 62, as shown in FIG. 14B, the interdigitated electrodes are printed at two locations as internal electrode patterns. In FIG. 14 (b), two pairs of crossed finger electrodes are used for ease of viewing. However, in order to make the area as large as possible in the plane, actually, as shown in FIG. Further, a plurality of pairs of cross finger electrodes may be formed so as to be formed on one surface in the plane.

The cross finger electrodes 65a ₁ and 65a ₂ , 65b ₁ and 65b ₂ are arranged such that the angle between the height direction (shown by a broken line) in FIG. In the electrode,
0 <θ <π / 2
And Since the polarization direction is a direction orthogonal to the direction of the fingers of the cross finger electrode, as shown by the broken line in the figure.
0 <| ε | <π / 2
It is. This upper interdigitated electrode serves as a drive electrode.

The angle formed by the _second interdigital electrodes 66a ₁ and 66a ₂ , 66b ₁ and 66b ₂ from the top of the figure is φ, as shown in the figure, and is a value other than 0, π / 2, and π. In this embodiment,
π / 2 <φ <3π / 2
It is said. The second cross finger electrodes 66a ₁ and 66a ₂ , 66b ₁ and 66b ₂ have a function as vibration detection electrodes.

  The n piezoelectric sheets (1) 61 are laminated, and then the piezoelectric sheet (3) 63 on which the internal electrode having the through hole 52 provided in the center is printed is laminated, and then (n-1). One sheet of piezoelectric sheet (2) 62 is laminated. Finally, the piezoelectric sheet (4) 64 with no electrodes printed thereon is laminated. Therefore, the total number of stacked sheets is 2n + 1, which is an odd number.

  The reason why a thick piezoelectric sheet (piezoelectric sheet (3) 63) is prepared in the center is to provide a through hole 52 in the central length direction.

  As will be described later, in the third embodiment, torsional secondary vibration and longitudinal primary vibration are used. The central portion of the upper cross finger electrode is provided near the upper node position of the torsional secondary vibration, and the central portion of the lower cross finger electrode is provided near the lower node position of the torsional secondary vibration.

  FIG. 14C is a view of the vibrator 51 viewed from the γ direction of FIG.

The left finger electrode 65a ₁ of the upper cross finger electrode of the internal electrode pattern is joined to the A + phase external electrode 67a ₁ . Similarly, the left finger electrode 65b ₁ of the upper cross finger electrode of the internal electrode pattern is joined to the B + phase external electrode 67b ₁ . The left finger electrode 66a ₁ of the lower cross finger electrode of the internal electrode pattern is joined to the C + phase external electrode 68a ₁ . The left finger electrode 66b ₁ of the lower cross finger electrode of the internal electrode pattern is joined to the D + phase external electrode 68b ₁ .

  FIG. 14D is a diagram of the vibrator 51 viewed from the δ direction of FIG.

The right finger electrode 65a ₂ of the upper intersecting finger electrode of the internal electrode pattern is joined to the A-phase external electrode 67a ₂ . Similarly, the right finger electrode 65b ₂ of the upper cross finger electrode of the internal electrode pattern is joined to the B-phase external electrode 67b ₂ . The right finger electrode 66a ₂ of the lower cross finger electrode of the internal electrode pattern is joined to the C-phase external electrode 68a ₂ . The right finger electrode 66b ₂ of the lower cross finger electrode of the internal electrode pattern is joined to the D-phase external electrode 68b ₂ .

  Note that the method of creating the laminated piezoelectric element in the third embodiment is the same as that in the first embodiment described above, and thus the description thereof is omitted.

  Next, the operation of the multilayer piezoelectric element 51 will be described.

  By setting the dimensions of the sides a, b, and c of the rectangular parallelepiped shape as shown in FIG. 6A to appropriate values, in the third embodiment, the longitudinal primary vibration mode and the torsional secondary vibration mode are used. Is used. Therefore, the value of a / b is set in the vicinity of 0.6. For example, the size of a × b × c is set to 10 × 6 × 20 mm.

  As shown in FIG. 14B, the first layer which is the outermost layer of the piezoelectric sheet (1) 61 and the outermost layer piezoelectric sheet (2) 62 laminated at the end of the piezoelectric sheet (2) 62 are used. Now, a method for driving the vibrator 51 will be described.

  First, the operation of the vibrator 51 using the driving cross finger electrode will be described.

An alternating voltage corresponding to the resonance frequency of longitudinal primary vibration or torsional secondary vibration is applied to the external electrodes 67a ₁ and 67a ₂ of the A phase (A + phase, A− phase) shown in FIGS. 14 (c) and (d). Applied. In the piezoelectric sheet (1) 61 shown in FIG. 14B, the force generated in the vicinity of the upper cross finger electrode by the inverse piezoelectric effect at that time is displayed as a vector.

  The force F shown in FIG. 14B is an alternating force, and when the force F is vector-decomposed, F1 and F2 are obtained. As is clear from the figure, the force F1 is a force that excites longitudinal vibration. Further, the force F2 becomes a force that generates a torsional secondary vibration, as is apparent from the drawing.

Next, an alternating voltage having the same frequency is also applied to the B-phase (B + phase, B− phase) external electrodes 67b ₁ and 67b ₂ shown in FIGS. 14 (c) and (d). In FIG. 14B, the force generated in the vicinity of the upper cross finger electrode of the piezoelectric sheet (2) 62 located on the other outermost surface at that time is displayed as a vector.

  The force F ′ shown in FIG. 14B is an alternating force, and F1 ′ and F2 ′ are obtained by vector decomposition of the force F ′. The force F1 ′ is a force that excites longitudinal vibration, as is apparent from the figure. Further, the force F2 'is a force that generates a torsional secondary vibration, as is apparent from the drawing.

  Next, when considering only the force generated when an alternating voltage of the same phase is applied to the A phase and the B phase at the same time, the forces F2 and F2 ′ are considered by referring to FIG. Cancel each other, no torsional secondary vibration occurs, and only longitudinal primary vibration occurs. When an alternating voltage having the above-mentioned frequency of opposite phase (phase difference π) is applied to the A phase and the B phase at the same time, the forces F1 and F1 ′ cancel each other, and no longitudinal primary vibration is generated, resulting in torsion. Only secondary vibration will occur.

  Next, consider a case where a phase difference between 0 and π is simultaneously given to the A phase and the B phase. In this case, the longitudinal primary vibration and the torsional secondary vibration occur simultaneously, and these vibrations are synthesized. At this time, as shown in FIG. 13, clockwise or counterclockwise elliptical vibration is formed in such a direction as to rotate the rotor 57 to the adhesion position of the frictional contact members 53a and 53b of the vibrator 51. . When elliptical vibration is generated at the positions of the frictional contact members 53a and 53b of the vibrator 51, the pressed rotor 57 rotates in the clockwise direction or the counterclockwise direction according to the rotational direction of the elliptical vibration. Will do.

  Next, the operation of the lower vibration detecting cross finger electrode shown in FIG. 14B will be described.

  When longitudinal primary vibration or torsional secondary vibration occurs, electric charges are generated on the surface of the interdigitated electrode due to the piezoelectric effect. The charge is observed as a voltage of C phase (between C + and C−) or a voltage of D phase (between D + and D−). In the operation with the driving cross-finger electrode, force is generated by the driving voltage due to the reverse piezoelectric effect described above, but on the contrary, a charge or voltage is generated by mechanical strain. Therefore, when only longitudinal primary vibration has occurred, C phase and D phase are connected in parallel in order (C + phase and D + phase are connected, and C- phase and D- phase are connected). As the voltage, a signal proportional to the magnitude and phase of the longitudinal primary vibration is obtained. In this case, when the C phase and the D phase are reversely connected in parallel (the C + phase and the D− phase are connected and the C− phase and the D + phase are connected), no signal is obtained.

  On the other hand, when only the secondary torsional vibration has occurred, the C phase and the D phase are connected in reverse (the C + phase and the D− phase are connected, and the C− phase and the D + phase are connected). As the voltage, a signal proportional to the magnitude and phase of the torsional secondary vibration can be obtained. In this case, no signal is obtained when the C phase and the D phase are connected in parallel in order (the C + phase and the D + phase are connected and the C− phase and the D− phase are connected).

  Therefore, by selecting the connection between the C phase and the D phase, it is possible to independently detect the longitudinal primary vibration or the torsional secondary vibration.

  Hereinafter, a method of driving a motor using such a vibration detection phase (C phase, D phase) will be described.

  The phase difference between the phase of the A-phase or B-phase signal that is the driving phase and the phase of the vibration detection phase (for example, a phase reversely connected in parallel with the C-phase and the D-phase) is predetermined during the resonance frequency operation of the torsional secondary vibration. It is known to take the value Ω. Therefore, in this case, by adjusting the frequency so that the phase difference between the drive phase and the detection phase is always Ω, the temperature rises due to the heat generated by the motor itself and the resonance frequency changes due to changes in the ambient environment temperature. Even when there is a change in the resonance frequency due to load fluctuations, it is always possible to drive near the torsional secondary resonance frequency, so that it is always possible to drive efficiently at the optimum frequency. This is also possible with the same concept when driving near the longitudinal primary resonance frequency.

  Thus, according to the third embodiment, in addition to the first and second embodiments described above, the vibrator holder that is necessary in the first and second embodiments is not necessary, and the number of parts is reduced. The number of degrees of freedom increases in the space occupied by the vibrator holder.

(First modification)
15A and 15B show a configuration of a multilayered piezoelectric element 71 according to a first modification of the third embodiment of the present invention, in which FIG. 15A is a plan view seen from above, FIG. 15B is an exploded perspective view, (c) is the figure which looked at the lamination piezoelectric element 71 from (gamma) direction of (a), (d) is the figure which looked at the lamination piezoelectric element 71 from (delta) direction of (a).

  In the first modification of the third embodiment, the piezoelectric sheet (3) having a thickness as in the third embodiment described above is not used, and a plurality of piezoelectric sheets (1) 61 and one sheet are used. The piezoelectric sheet (4) 64 is laminated. And after all the piezoelectric sheets are laminated | stacked, the through-hole 52 for inserting the shaft 56 in the center part is formed.

Thereby, a part of the internal electrode is removed by the through hole 52, but the exposed part of the internal electrode of the piezoelectric sheet from which the part of the internal electrode has been removed is not connected to the external electrode. That is, as shown in FIGS. 15C and 15D, between the A + phase external electrode 67a ₁ and the B + phase external electrode 67b ₁ , between the C + phase external electrode 68a ₁ and the D + phase external electrode 68b _1. Similarly, between the A-phase external electrode 67a ₂ and the B-phase external electrode 67b ₂ and between the C-phase external electrode 68a ₂ and the D-phase external electrode 68b ₂ , Since it is a portion of the piezoelectric sheet from which a part of the electrode is removed, a gap is provided.

  Thus, according to the 1st modification of 3rd Embodiment, it is possible to comprise a cross finger electrode with two types of piezoelectric sheets similarly to 2nd Embodiment. In this case, similarly, since only electrodes having the same polarity exist on the same plane, there is no problem of short circuit between the electrodes.

(Second modification)
Further, although not shown as a second modification of the third embodiment, all of the cross finger electrodes are used as driving cross finger electrodes, as in the second modification of the first embodiment described above. can do.

  If comprised in this way, an ultrasonic motor with big power is realizable.

  In the above-described embodiment, the dimensions of the sides a × b × c (the length in the central axis direction) are only suitable examples, and are described below according to the device to be applied and the intended use. It can be changed as appropriate. For example, as shown in FIG. 7, the rectangular ratio a / b regarding the ultrasonic motor after completion of the production is the same because the resonance frequencies of the longitudinal primary resonance vibration and the torsional secondary (or tertiary) resonance vibration coincide with each other. A predetermined ratio (a rectangular ratio corresponding to an intersection in the figure) is most preferable, and even at a rectangular ratio where the resonance frequencies substantially correspond to each other in the vicinity range (for example, within ± 0.02). Can be used equally. Moreover, if it is in any effective range (for example, within ± 0.05) with respect to a predetermined rectangular ratio in which the resonance frequencies coincide with each other, the above-described operational effects of the present invention can be enjoyed.

  The length in the rotation axis direction (side c: 20 mm) only needs to be long enough to arrange the electrodes for vibrating along the vertical direction and the torsional direction and generating these vibrations. Therefore, it is not necessary to set the length of the side c to a predetermined ratio with respect to the other lengths (side a and side b), but also a length for adjusting vibration through a groove as conventionally required. Since this portion is unnecessary, there is an advantage that a simple and small ultrasonic motor can be provided with a large degree of design freedom. Further, if the dimensional ratios a / b and a / c (or b / c) in these three directions are enlarged or reduced at various similar ratios according to the purpose, an ultrasonic motor having an arbitrary dimension can be provided. It can be applied to large and small objects.

  As mentioned above, although embodiment of this invention was described, in the range which does not deviate from the summary of this invention other than embodiment mentioned above, this invention can be variously modified.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

1 is an external perspective view showing an ultrasonic motor according to a first embodiment of the present invention. 1A and 1B show a laminated piezoelectric element in a state where a frictional contact member is bonded in the ultrasonic motor 10 of FIG. 1, wherein FIG. 1A is an external perspective view, and FIG. 1 shows a configuration of a laminated piezoelectric element 11, (a) is a plan view seen from above, (b) is an exploded perspective view, (c) is a perspective view seen from the α direction of (a), (d). Is a view of the laminated piezoelectric element 11 as viewed from the γ direction of (a), (e) is a view of the laminated piezoelectric element 11 as viewed from the δ direction of (a), and (f) is an external view of the laminated piezoelectric element of (d). The figure which showed the state in which the electrode was attached, (g) is the figure which showed the state in which the external electrode was attached to the laminated piezoelectric element of (e), (h) was the external electrode in the laminated piezoelectric element of (d). The figure which showed the other example attached, (i) is the figure which showed the other example to which the external electrode was attached to the laminated piezoelectric element of (e). It is the figure which showed the example of arrangement | positioning of the cross finger electrode formed in the vibrator | oscillator surface. FIG. 4 is a cross-sectional view including the polarization direction shown along the line BB ′ in FIG. 3B and perpendicular to the side surface. It is a figure for demonstrating matching of the natural frequency of the vibrator | oscillator 11 used for the ultrasonic motor 10 of the 1st Embodiment of this invention. 6 represents the resonance frequency of each mode at various rectangular ratios where the side c of the vibrator 11 in FIG. 6 is constant and the horizontal axis is the length of the short side / the length of the long side (a / b). FIG. 1 shows a configuration of a multilayer piezoelectric element 11 according to a first modification of the first embodiment of the present invention, where (a) is an exploded perspective view, and (b) is a diagram of the multilayer piezoelectric element 11 of (a). The figure seen from the left direction, (c) is the figure which looked at the laminated piezoelectric element 11 of (a) from the right direction. The structure of the laminated piezoelectric element 11 in the 2nd modification of the 1st Embodiment of this invention is shown, (a) is a disassembled perspective view, (b) shows the laminated piezoelectric element 11 of (a). It is the figure seen from the bottom face side. It is the disassembled perspective view which showed the structure of the laminated piezoelectric element of the ultrasonic motor which concerns on the 2nd Embodiment of this invention. It is the figure which showed the cross section containing the direction orthogonal to the direction of the finger | toe of a cross finger electrode, and a lamination direction, in order to show the mode of polarization inside the lamination piezoelectric element by the 2nd Embodiment of this invention. It is an external appearance perspective view of the ultrasonic motor which concerns on the 3rd Embodiment of this invention. FIG. 13 is an external perspective view of a vibrator in a state where a frictional contact member is bonded in the ultrasonic motor of FIG. 12. The structure of the laminated piezoelectric element 11 in 3rd Embodiment is shown, (a) is the top view seen from the upper surface, (b) is a disassembled perspective view, (c) is the laminated piezoelectric element 11 (a (D) is a view of the laminated piezoelectric element 11 viewed from the δ direction of (a). The structure of the laminated piezoelectric element 71 by the 1st modification of the 3rd Embodiment of this invention is shown, (a) is the top view seen from the upper surface, (b) is an exploded perspective view, (c) is laminated | stacked. The figure which looked at the piezoelectric element 71 from (gamma) direction of (a), (d) is the figure which looked at the laminated piezoelectric element 71 from (delta) direction of (a).

Explanation of symbols

10,50 ... ultrasonic motor 11 laminated piezoelectric element (vibrator), 12a, 12b ... frictional contact _{member, 13,13a 1, 13a 2, 13b} 1, 13b 2, 13c 1, 13c 2, 13d 1, 13d 2 DESCRIPTION OF SYMBOLS ... External electrode, 15 ... Rotor, 16 ... Bearing, 17 ... Spring, 18 ... Spring retaining ring, 20 ... Vibrator holder, 21 ... Shaft fixing ring, 22 ... Shaft, 25a ... Piezoelectric sheet 1 (piezoelectric sheet (1)) 25b ... Piezoelectric sheet 2 (piezoelectric sheet (2)), 25c ... Piezoelectric sheet 3 (piezoelectric sheet (3)), 26a ... Internal electrode pattern 1 (internal electrode pattern (1)), 26b ... Internal electrode pattern 2 (internal electrode pattern _{(2)), 27a 1,} 27a 2, 27b 1, 27b 2 ... upper interdigital and central _{interdigital, 28a 1, 28a 2, 28b} 1, 28b 2 ... lower cross _{Electrodes, 29a 1, 29a 2, 29b} 1, 29b 2, 30a 1, 30a 2, 30b 1, 30b 2 ... inner electrode exposed portion, and the primary longitudinal vibration in 35 ₁ ... central section located near the torsional tertiary vibration , 35 ₂ ... Upper node position, 35 ₃ ... Lower node position of torsional tertiary vibration.

Claims (23)

A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis In an ultrasonic motor comprising at least a driven rotor,
The vibrator is composed of a single piezoelectric element, the polarization direction of the piezoelectric element is substantially in the in-plane direction of the side surface of the vibrator including the direction of the central axis, and an angle ε formed with the direction of the central axis But,
0 <ε <π / 2
Is set to meet
By synthesizing the longitudinal primary resonance vibration of the vibrator extending and contracting in the rotation axis direction and the torsional tertiary resonance vibration having the rotation axis as a torsion axis, the elliptical vibration is formed to rotate the rotor. Features an ultrasonic motor.   The longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis is orthogonal to the rotation axis of the vibrator so that the resonance frequency of the torsional tertiary resonance vibration having the rotation axis as the torsion axis substantially coincides. The ultrasonic motor according to claim 1, wherein a ratio of a short side to a long side of the substantially rectangular cross section is approximately 0.3. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis In an ultrasonic motor comprising at least a driven rotor,
The vibrator is composed of a single piezoelectric element,
The direction of polarization of the piezoelectric element is substantially in the in-plane direction of the side surface of the vibrator including the direction of the central axis, and an angle ε formed with the direction of the central axis is
0 <ε <π / 2
Is set to meet
By combining the longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis and the torsional secondary resonance vibration having the rotation axis as a torsion axis, the elliptical vibration is formed to rotate the rotor. Features an ultrasonic motor.   The longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis is orthogonal to the rotation axis of the vibrator so that the resonance frequency of the torsional secondary resonance vibration having the rotation axis as the torsion axis is substantially the same. The ultrasonic motor according to claim 3, wherein a ratio of a short side to a long side of the substantially rectangular cross section is approximately 0.6.   The ultrasonic motor according to claim 1, wherein the polarization is formed at a position including at least one node portion among the three cylindrical portions of the torsional tertiary resonance vibration.   5. The ultrasonic motor according to claim 3, wherein the polarization is formed at a position including at least one nodal portion of the two portions of the torsional secondary resonance vibration. 6. An internal electrode that includes the central axis and is divided into at least two groups with a plane parallel to the outer surface of the vibrator as a boundary, and a plurality of internal electrodes that are provided on the outer surface of the vibrator and connected to the inner electrode External electrodes, and
The polarization is formed between the internal electrodes, and by applying an alternating voltage to the plurality of external electrodes, the elliptical vibration is excited to rotate the rotor. The ultrasonic motor according to any one of 6.   The vibrator includes a first piezoelectric sheet on which a plurality of first interdigitated internal electrode patterns are formed with a plane parallel to the outer surface of the vibrator including the central axis, and a plurality of second piezoelectric sheets. The ultrasonic motor according to claim 7, wherein a plurality of second piezoelectric sheets each having a cross finger internal electrode pattern formed thereon are laminated.   At least one of the plurality of first cross finger electrode patterns of the first piezoelectric sheet and at least one of the plurality of second cross finger electrode patterns of the second piezoelectric sheet are drive cross finger electrodes. The ultrasonic motor according to claim 8.   At least one of the plurality of first cross finger electrode patterns of the first piezoelectric sheet and at least one of the plurality of second cross finger electrode patterns of the second piezoelectric sheet are vibration detection cross finger electrodes. The ultrasonic motor according to claim 8, wherein the ultrasonic motor is provided. A first laminated body in which a first piezoelectric sheet on which a first right finger internal electrode pattern is formed and a second piezoelectric sheet on which a second left finger electrode pattern is formed are alternately laminated;
A second laminated body in which a third piezoelectric sheet on which a third right finger internal electrode pattern is formed and a fourth piezoelectric sheet on which a fourth left finger electrode pattern is formed are alternately laminated;
Further comprising
The vibrator includes the central axis, and the first laminated body and the second laminated body are integrally formed with a plane parallel to the outer surface of the vibrator as a boundary. The ultrasonic motor according to claim 7.   Consists of at least one of a plurality of interdigitated electrode patterns composed of internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet, and internal electrodes of the third piezoelectric sheet and the fourth piezoelectric sheet. The ultrasonic motor according to claim 11, wherein at least one of the plurality of crossed finger electrode patterns is a driving crossed finger electrode.   Consists of at least one of a plurality of interdigitated electrode patterns composed of internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet, and internal electrodes of the third piezoelectric sheet and the fourth piezoelectric sheet. The ultrasonic motor according to claim 11, wherein at least one of the plurality of crossed finger electrode patterns is a vibration detecting crossed finger electrode. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis In an ultrasonic motor comprising at least a driven rotor,
The vibrator is formed by laminating a plurality of piezoelectric sheets on which crossed finger electrode patterns are formed,
In the piezoelectric sheet, the first driving cross finger electrode is provided in the vicinity of the first node position of the torsional vibration of the plane parallel to the rotation axis. The angle θ with the direction of the central axis is
0 <θ <π / 2
Provided
A second driving cross-finger electrode electrically connected in parallel with the driving electrode is provided in the vicinity of the second node position of the torsional vibration on the plane parallel to the rotation axis, and a finger of the cross-finger electrode is provided. The angle φ between the direction and the direction of the central axis is
π / 2 <φ <π
Provided
Near the third node position of the torsional vibration of the plane parallel to the rotation axis, a vibration detecting cross finger electrode is provided, and the finger direction of the second driving cross finger electrode and the direction of the central axis are Is provided under conditions other than 0, π / 2, and π,
An ultrasonic motor characterized in that the elliptical vibration is formed by synthesizing a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional tertiary resonance vibration having the rotation axis as a torsion axis. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates around the central axis orthogonal to the elliptical vibration generating surface of the vibrator. In an ultrasonic motor comprising at least a driven rotor,
The vibrator is formed by laminating a plurality of first piezoelectric sheets on which a driving cross-finger electrode pattern is formed,
In the first piezoelectric sheet, a first driving cross-finger electrode is provided in the vicinity of a first node position of torsional vibration of a plane parallel to the rotation axis, and a finger of the cross-finger electrode is provided. The angle θ between the direction and the direction of the central axis is
0 <θ <π / 2
Provided
A vibration detecting cross finger electrode is provided in the vicinity of the second node position of the torsional vibration on the plane parallel to the rotation axis, and the finger direction of the vibration detecting cross finger electrode and the direction of the central axis are formed. The angle ψ is set under conditions other than 0, π / 2, and π,
An ultrasonic motor characterized in that the elliptical vibration is formed by synthesizing a longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis and a torsional secondary resonance vibration having the rotation axis as a torsion axis. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis The elliptical vibration is formed by synthesizing a longitudinal primary resonance vibration that extends and contracts in the direction of the rotation axis of the vibrator and a torsional tertiary resonance vibration having the rotation axis as a torsion axis. In the ultrasonic motor consisting of
The vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which driving internal electrode patterns are formed,
In the first piezoelectric sheet, the left finger side of the driving cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the length of the left finger internal electrode is long. The angle θ between the direction and the direction of the rotation axis is
0 <θ <π / 2
Provided
In the second piezoelectric sheet, the right finger side of the driving cross finger electrode is provided in the vicinity of the node position of the torsional vibration of the plane parallel to the rotation axis, and the length of the internal electrode on the right finger side is long. The angle formed between the direction of the rotation axis and the direction of the rotation axis is the same angle as the internal electrode on the left finger side,
A pair of interdigital electrodes are formed substantially by the driving internal electrode of the first piezoelectric sheet and the driving internal electrode of the second piezoelectric sheet,
A part of the driving internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet are extended to the end portions of the respective piezoelectric sheets, are electrically connected to the respective external electrodes, and have a substantially central portion in the stacking direction as a boundary. The extending portion of the driving internal electrode of the first piezoelectric sheet and the extending portion of the driving internal electrode of the second piezoelectric sheet are connected to different external electrodes, respectively. Sonic motor. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis The elliptical vibration is formed by synthesizing a longitudinal primary resonance vibration that extends and contracts in the direction of the rotation axis of the vibrator and a torsional secondary resonance vibration having the rotation axis as a torsion axis. In the ultrasonic motor consisting of
The vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which driving internal electrode patterns are formed,
In the first piezoelectric sheet, the left finger side of the driving cross-finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the inside of the left finger side The angle θ between the longitudinal direction of the electrode and the direction of the rotation axis is
0 <θ <π / 2
Provided
In the second piezoelectric sheet, the right finger side of the driving cross finger electrode is provided in the vicinity of the node position of the torsional vibration of the plane parallel to the rotation axis, and the length of the internal electrode on the right finger side is long. The angle formed between the direction of the rotation axis and the direction of the rotation axis is the same angle as the internal electrode on the left finger side,
A pair of interdigitated electrodes are substantially formed by the driving internal electrode of the first piezoelectric sheet and the driving internal electrode of the second piezoelectric sheet,
A part of the internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet are extended to the end of each piezoelectric sheet, are electrically connected to the respective external electrodes, and have a substantially central portion in the stacking direction as a boundary. The ultrasonic motor, wherein the extending portion of the driving internal electrode of the first piezoelectric sheet and the extending portion of the driving internal electrode of the second piezoelectric sheet are connected to different external electrodes, respectively. . A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio, and is in contact with the elliptical vibration generating surface of the vibrator and rotates about the central axis perpendicular to the elliptical vibration generating surface of the vibrator as a rotation axis The elliptical vibration is formed by synthesizing a longitudinal primary resonance vibration that extends and contracts in the direction of the rotation axis of the vibrator and a torsional tertiary resonance vibration having the rotation axis as a torsion axis. In the ultrasonic motor consisting of
The vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which vibration detection internal electrode patterns are formed,
In the first piezoelectric sheet, the left finger side of the vibration detecting cross finger electrode is provided in the vicinity of at least one node position of the torsional vibration of the plane parallel to the rotation axis, and the inside of the left finger side is provided. The angle θ between the longitudinal direction of the electrode and the direction of the rotation axis is
0 <θ <π / 2
Provided
In the second piezoelectric sheet, the right finger side of the vibration detecting cross-finger electrode is provided in the vicinity of the node position of the torsional vibration of the surface parallel to the rotation axis, and the internal electrode on the right finger side is provided. The angle formed by the longitudinal direction and the direction of the rotation axis is provided at the same angle as the internal electrode on the left finger side,
A vibration detection internal electrode of the first piezoelectric sheet and a vibration detection internal electrode of the second piezoelectric sheet substantially form a pair of vibration detection inter-finger electrodes,
Part of the vibration detection internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet extends to the end of each piezoelectric sheet, and is electrically connected to each external electrode, and has a substantially central portion in the stacking direction. As a boundary, the extending portion of the driving electrode of the first piezoelectric sheet and the extending portion of the vibration detecting internal electrode of the second piezoelectric sheet are connected to different external electrodes, respectively. Ultrasonic motor. A vibrator whose cross section perpendicular to the central axis has a rectangular length ratio and the elliptical vibration generating surface of the vibrator and the central axis perpendicular to the elliptical vibration generating surface of the vibrator are driven to rotate. A supersonic wave composed of at least a rotor and combined with a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and a torsional secondary resonance vibration having the rotation axis as a torsion axis. In the sonic motor,
The vibrator is formed by alternately laminating a plurality of first piezoelectric sheets and second piezoelectric sheets on which vibration detection internal electrode patterns are formed, and the first piezoelectric sheet has the rotation. The left finger side of the vibration detecting cross-finger electrode is provided in the vicinity of at least one node position of torsional vibration of a plane parallel to the axis, and the angle formed by the longitudinal direction of the left finger internal electrode and the direction of the rotation axis θ is provided under the following conditions:
0 <θ <π / 2
In the second piezoelectric sheet, the right finger side of the vibration detecting cross finger electrode is provided in the vicinity of the node position of the torsional vibration of the plane parallel to the rotation axis, and the longitudinal direction of the right finger internal electrode The angle formed by the direction of the rotation axis is the same as that of the left finger internal electrode, and the vibration detection internal electrode of the first piezoelectric sheet and the vibration detection internal electrode of the second piezoelectric sheet are substantially the same. A pair of vibration detecting interdigitated electrodes, and part of the vibration detecting internal electrodes of the first piezoelectric sheet and the second piezoelectric sheet are extended to the end of each piezoelectric sheet, The extension portion of the driving electrode of the first piezoelectric sheet and the extension portion of the internal electrode for vibration detection of the second piezoelectric sheet are further connected to each external electrode and at the substantially central portion in the stacking direction. Supersonic sound characterized by being connected to separate external electrodes Motor.   The ultrasonic motor according to claim 7, wherein the external electrode is provided only on one side surface of the vibrator. A vibrator holder fixed at substantially the center of the vibrator;
A shaft held by the vibrator holder;
A spring that presses against the vibrator the rotor held rotatably with respect to the shaft;
The ultrasonic motor according to any one of claims 1, 2, 5, 14, 16, and 18, further comprising: A through hole provided in a portion corresponding to the rotation axis of the vibrator;
A shaft fixed to a substantially central portion of the through hole;
A spring that presses against the vibrator the rotor held rotatably with respect to the shaft;
The ultrasonic motor according to any one of claims 3, 4, 6, 15, 17, and 19, further comprising:   In the cross section orthogonal to the central axis, the arrangement of the vibrators is substantially symmetric with respect to a virtual center line parallel to the rectangular short side or long side passing through the central axis. The ultrasonic motor according to any one of claims 1 to 22.

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