JP2010166673A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor which eliminates the formation of a groove, does not need to form a hole at a piezoelectric element, can easily excite vertical resonance vibration and twisted resonance vibration by a simple structure, and rotates a rotor by using an ellipse vibration generated at an ultrasonic vibrator. <P>SOLUTION: The ultrasonic motor comprises parallelepiped laminated piezoelectric elements 25, 26 whose cross sections vertical to a central axis are almost rectangular, and the rotor 15 which contacts with ellipse vibration generation faces of the laminated piezoelectric elements 25, 26, and is rotationally driven with the central axis as a rotating axis which is orthogonal to the ellipse vibration generation faces. The laminated piezoelectric elements 25, 26 are composed of an elastic body 21 whose cross section is vertical to the central axis, and the first laminated piezoelectric element 25 and the second laminated piezoelectric element 26 which are arranged so as to oppose a face in the longitudinal direction of the cross section. Then, there is formed the ellipse vibration by synthesizing the vertical primary resonance vibration which expands and contracts in the rotational axial directions of the laminated piezoelectric elements 25, 26, and the twisted secondary resonance vibration or the tertiary resonance vibration with the central axis as a twisted axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 the above-mentioned Patent Document 1 has to cut the elastic body diagonally. In order to match the frequencies of the longitudinal vibration and the torsional vibration, it is one of the elastic bodies. There was a problem that a groove portion had to be provided in the portion. In addition, since the hole is provided in the center of the piezoelectric element, there is a problem that the piezoelectric element is easily damaged by itself or particularly when touching the shaft.

  Accordingly, the present invention has been made in view of the above problems, and the object thereof is to eliminate the need for a groove and to provide a hole in the piezoelectric element, and to facilitate longitudinal resonance vibration and torsional resonance vibration with a simple structure. It is an object of the present invention to provide an ultrasonic motor that can be excited by the motor and rotates a rotor by elliptic vibration generated in an ultrasonic vibrator.

  That is, the present invention relates to an approximately rectangular parallelepiped vibrator having a substantially rectangular length ratio in a cross section perpendicular to the central axis, and the elliptical vibration generating surface of the vibrator in contact with the elliptical vibration generating surface of the vibrator. And a rotor that is driven to rotate about a central axis orthogonal to the rotation axis, and the vibrator has a substantially rectangular cross section perpendicular to the central axis, and has a substantially rectangular shape. A substantially rectangular parallelepiped-shaped elastic body having a first side surface including one side and a second side surface that forms a pair with the first side surface, and a first surface disposed opposite to the first side surface of the elastic body A longitudinal primary resonance vibration that includes a piezoelectric element and a second piezoelectric element disposed opposite to the second side surface of the elastic body and expands and contracts in the direction of the rotation axis of the vibrator; Torsional secondary resonance vibration or torsional tertiary resonance vibration with the axis as a torsion axis. To form the elliptical vibration by, characterized in that for rotating the rotor.

  According to the present invention, there is no need for a groove portion, and there is no need to provide a hole portion in the piezoelectric element, so that longitudinal resonance vibration and torsional resonance vibration can be easily excited with a simple structure, and an ellipse generated in an ultrasonic transducer. An ultrasonic motor that rotates a rotor by vibration can be provided.

1 is an external perspective view showing an ultrasonic motor according to a first embodiment of the present invention. FIGS. 2A and 2B show the vibrator of FIG. 1, in which FIG. 1A is an exploded perspective view of the vibrator, and FIG. FIGS. 2A and 2B are diagrams illustrating a configuration of a laminated piezoelectric element used in the first embodiment of the present invention, in which FIG. 1A shows an example of a piezoelectric sheet and internal electrode patterns, and FIG. The figure which showed the example of arrangement | positioning of a finger electrode, (c) is the figure which showed the external electrode after lamination | stacking of the lamination | stacking piezoelectric element shown by (b). FIG. 3 is a cross-sectional view including the polarization direction shown along line AA ′ in FIG. 2A 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. 5 represents the resonance frequency of each mode at various rectangular ratios where the side c of the vibrator 11 in FIG. 5 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 according to a first modification of the first embodiment of the present invention, where (a) is an exploded perspective view, and (b) is a leftward direction of the multilayer piezoelectric element of (a). (C) is a view of the laminated piezoelectric element of (a) as viewed from the right direction. The structure of the laminated piezoelectric element in the 2nd modification of the 1st Embodiment of this invention is shown, (a) is a disassembled perspective view, (b) is an external electrode of the laminated piezoelectric element of (a). FIG. It is the figure which showed the mode of the polarization by the 2nd modification of the 1st Embodiment of this invention. The structure of the laminated piezoelectric element in the 3rd modification of the 1st Embodiment of this invention is shown, (a) is a disassembled perspective view, (b) is an external electrode of the laminated piezoelectric element of (a). FIG. The structure of the laminated piezoelectric element in the 4th modification of this invention is shown, (a) is the figure which showed the example of a piezoelectric sheet and an internal electrode pattern, (b) is a piezoelectric sheet (a) ( 3) A perspective view seen from the direction 25c, (c) a view seen from the right side direction, and (d) a view seen from the left side direction. The structure of the vibrator | oscillator in the 4th modification of the 1st Embodiment of this invention is shown, (a) is a disassembled perspective view, (b) is the electrode pattern of the 1st piezoelectric element of (a). (C) is a figure which showed the electrode pattern of the 2nd piezoelectric element of (a). FIGS. 3A and 3B show a configuration of an ultrasonic motor vibrator according to a second embodiment of the present invention, in which FIG. 4A is an exploded perspective view, and FIG. 4B is a perspective view showing a state where the vibrator of FIG. FIG. 4C is a view of the vibrator of FIG. The structure of the vibrator | oscillator of the ultrasonic motor which concerns on the modification of the 2nd Embodiment of this invention is shown, (a) is a disassembled perspective view, (b) shows the state which assembled the vibrator | oscillator of (a). It is the shown perspective view.

  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. 2 shows the vibrator of FIG. 1. FIG. 2A is an exploded perspective view of the vibrator, and FIG. 2B is a perspective view of the vibrator.

  The ultrasonic motor 10 includes a vibrator 11 that constitutes a vibrator, friction contact members 12 a and 12 b, an external electrode 13, a rotor 15, a bearing 16, a spring 17, a spring holding ring 18, and a shaft 19. And at least.

  The friction contact members 12 a and 12 b are bonded to a surface perpendicular to the longitudinal direction of the vibrator 11 so as to come into contact with the rotor 15. The friction contact members 12a and 12b are made of a ceramic material such as alumina or zirconia, or an engineering plastic material such as PPS or PEEK. Although details will be described later, at the positions of the frictional contact members 12a and 12b, as shown in FIG. 2B, elliptical vibration is generated in the clockwise direction (CW direction) or counterclockwise direction (CCW direction). Is generated. However, the friction contact members 12a and 12b are not necessarily required. 1 and 2, four external electrodes 13 are provided on the left side of the drawing, and four are also provided on the right side although not shown in the drawing.

  The rotor 15 rotates by being pressed by the prismatic vibrator 11 and the top surface of the vibrator 11. The bearing 16 has an outer surface fixed to the inner surface of the rotor and rotatably holds the rotor 15. The bearing 16 includes a bearing inner ring to which the shaft 19 is fixed and a bearing outer ring fixed to the inner periphery of the rotor 15. The

  The spring 17 is an elastic member for applying a pressing force to the bearing inner ring, and contacts the inner side of the bearing. The spring holding ring 18 is for controlling the amount of contraction of the spring 17 that contracts the spring 17 and generates a spring force. Furthermore, as described above, the shaft 19 is fixed at substantially the center of the vibrator 11.

  The longitudinal direction of the shaft 19 is defined as the central axis direction.

  The vibrator 11 has a rectangular parallelepiped shape, an elastic body 21 made of a metal material such as stainless steel or brass material, and a rectangular parallelepiped first laminated piezoelectric element 25 and a second laminated piezoelectric element on both side surfaces of the elastic body 21. 26 is constituted by being bonded by an adhesive. The elastic body 21 has a through hole 22 at the center thereof so that the shaft 19 can be inserted therethrough. A female screw portion 23 for holding the shaft 19 is provided at the central portion of the through hole 22 in the axial direction, and a male screw portion (not shown) at the central portion of the shaft 19 is engaged and bonded. As will be described later, the female screw portion 23 geometrically substantially coincides with the node portion of the longitudinal primary vibration of the vibrator 11 and the central node portion of the torsional secondary vibration.

  In addition, external electrodes 13 are provided on both side surfaces of each of the laminated piezoelectric elements 25 and 26 as shown in the figure.

  As the external electrode 13, the first laminated piezoelectric element 25 has an A− phase and a C− phase, and although not shown, an A + phase and a C + phase exist on the opposite side. The second laminated piezoelectric element 26 has a B-phase and a D-phase, and although not shown, there are a B + phase and a D + phase on the opposite side.

  The outer diameter dimensions of the vibrator 11 are a = 6 mm, b = 10 mm, and c = 20 mm. Moreover, the thickness of the friction contact members 12a and 12b is about 0.1 mm to 1 mm.

  Next, with reference to FIG. 3, the structure of the laminated piezoelectric element used in this embodiment will be described.

  FIG. 3A is a diagram showing an example of a piezoelectric sheet and internal electrode patterns.

The laminated piezoelectric element 25 ₁ is formed by laminating thin piezoelectric sheets such as lead zirconate titanate (hereinafter referred to as PZT) on which a predetermined internal electrode pattern is formed. The piezoelectric sheet 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, and the piezoelectric sheet 2 (hereinafter referred to as piezoelectric sheet (2)). The internal electrode pattern 2 is printed on each 25b.

  The internal electrode is made of a silver-palladium alloy and has a thickness of about several μm. As shown in the figure, the piezoelectric sheet (1) 25a has crossed finger electrodes (upper crossed finger electrode (internal electrode) 27 and lower crossed finger electrode (internal electrode) 28) printed at two locations. The width of the interdigital finger electrode 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.

  Here, the cross finger electrode refers to an electrode in which a + phase electrode and a-phase electrode are alternately combined. In FIG. 3 (a), the cross finger electrodes have two pairs of cross finger electrodes for the sake of easy viewing. However, in order to have as large an area as possible in the plane, in practice, FIG. As shown in b), more pairs of crossed finger electrodes may be formed so as to be formed on one surface within the surface.

In FIG. 3 (a), the cross finger electrode has an angle formed by the direction of the central axis (shown by a broken line) and the finger direction of the cross finger electrode.
0 <θ <π / 2
And Since the polarization direction α (indicated by a broken line) is a direction orthogonal to the direction of the fingers of the cross finger electrode,
α = π / 2−θ
0 <α <π / 2
It is. As shown in the figure, α and θ are reversed with respect to the direction in which the angle is measured.

The angle formed by the lower cross finger electrode 28 shown in FIG. 3A is φ, as shown in the figure.
φ = π−θ
π / 2 <φ <π
It has become.

  The lower cross finger electrode 28 is electrically connected to the upper cross finger electrode 27 in parallel, and a part of the lower cross finger electrode 28 extends to the end of the piezoelectric sheet. N sheets of the piezoelectric sheets (a) 25a are stacked, and then the piezoelectric sheet (2) 25b is stacked. The electrode pattern of the piezoelectric sheet (2) 25b is exactly the same as that of the piezoelectric sheet (1) 25a, but only the position of the electrode extending to the end is different. This piezoelectric sheet (2) 25b is used for vibration detection. Finally, a piezoelectric sheet 3 on which no electrode is printed (hereinafter referred to as a piezoelectric sheet (3)) 25c is laminated.

  As will be described later, in this embodiment, when the vibrator 11 is configured, torsional secondary vibration and longitudinal primary vibration generated in the vibrator 11 are used. Therefore, the position of the interdigitated electrode of the present embodiment is such that the central portion of the upper interdigital finger electrode 27 is provided near the upper node position of the torsional secondary vibration, and the central portion of the lower interdigital finger electrode 28 is the lower portion of the torsional secondary vibration. It is provided near the node position.

  FIG. 3C shows an external electrode after the lamination of the laminated piezoelectric element shown in FIG.

In the figure, on the right side, an A + (B +) phase external electrode 13a ₁ (13b ₁ ) electrically connected to the internal electrodes of n piezoelectric sheets (a) 25a and one piezoelectric sheet (2). An external electrode 13c ₁ (13d ₁ ) of C + (D +) phase that is electrically connected to the internal electrode 25b is provided. Although not shown, on the opposite surface, there are A- (B-) phase external electrodes 13a ₂ (13b ₂ ) and C- (D-) phase external electrodes 13c ₂ (13d ₂ ). Is provided.

  When the laminated piezoelectric element 11 having such a configuration is bonded to the elastic body 21 shown in FIG. 2, the first laminated piezoelectric element 25 is bonded to one surface of the elastic body 12, and then the surface facing the elastic body 21. In addition, another second laminated piezoelectric element 26 is turned upside down and bonded to the elastic body 21 while being turned upside down. This is because the same type of laminated piezoelectric elements is used so that the piezoelectric sheet (2) 25b side having the vibration detection phase with respect to the elastic body 21 is located outside the vibrator 11, and the direction of polarization is This is to ensure that they are in the same direction.

  Next, a method for creating the laminated piezoelectric elements 25 and 26 in the present embodiment will be described.

  Prepare n sheets of printed internal electrode patterns on the piezoelectric sheet (1) 25a before firing, and 1 printed sheets of internal electrode patterns on the piezoelectric sheet (2) 25b. First, after n sheets of piezoelectric sheets (1) 25a are stacked, one sheet of piezoelectric sheets (2) 25b is stacked, and one sheet of piezoelectric sheet (3) 25c on which no internal electrode is printed is stacked. .

  Then, after being pressed and cut into a predetermined size, firing is performed at a predetermined temperature. Next, the external electrode 13 is printed and baked at a predetermined position. Thereafter, polarization is performed to complete the laminated piezoelectric elements 25 and 26.

  Here, the polarization will be described with reference to FIG.

  FIG. 4 is a cross-sectional view including the polarization direction shown along the line AA ′ in FIG. 3A and perpendicular to the side surface.

  In FIG. 4, the polarization vector indicated by the arrow P is polarized toward the other pole (−) with a slight bulge from the pole (+) on one side. This vector also coincides with the electric field vector. The distance between adjacent internal electrodes is, for example, 300 μm, and the thickness of the piezoelectric sheet is, for example, 100 μm.

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

  As shown in FIG. 5 (a), the shape of the vibrator 11 is a rectangular parallelepiped shape, and the dimensions of the sides a, b, and c are set to appropriate values, so that the longitudinal primary vibration mode (first order) The resonance frequency of the resonance vibration) and the resonance frequency of the torsional secondary vibration mode (torsional secondary resonance vibration) or the torsional tertiary vibration mode (torsional tertiary resonance vibration) are made to substantially coincide.

5B is a torsional primary vibration mode (torsional primary resonance vibration), FIG. 5C is a longitudinal primary vibration mode, FIG. 5D is a torsional secondary vibration mode, and FIG. FIG. 6 is a diagram schematically showing a vibration state in a torsional tertiary vibration mode. 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, 30 ₁ , 30 ₂ , 30 ₃ , 30 ₄ , 30 ₅ are positions corresponding to the vibration nodes of the vibrator 11, and 30 ₄ , 30 ₅ are the upper node positions of the torsional secondary vibration, 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. 6 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 the present embodiment, the longitudinal primary resonance mode and the torsional secondary resonance mode are used, so that the dimensions of the vibrator 11 are set so that a / b is approximately 0.6.

  In addition, from the figure of the resonance vibration of each mode shown in FIG. 6, the node portion of the longitudinal primary vibration mode is a substantially central portion, the node portion of the torsional secondary vibration mode is an arbitrary portion of the central axis (and the upper node position). Therefore, a substantially central portion on the central axis of the elastic body 12 is a common node. Therefore, if the shaft 19 is held at this node, vibration hardly leaks into the shaft 19 and a highly efficient motor can be obtained.

  Next, the operation of the vibrator 11 in this embodiment will be described using the upper cross finger electrode 26 shown in FIG.

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

  An alternating voltage corresponding to the resonance frequency of the primary longitudinal vibration or torsional secondary vibration is applied to the A phase (A + phase, A-phase) and B phase (B + phase, B-phase) shown in FIG. Is done.

  In FIG. 3A, the force generated in the vicinity of the upper interdigital finger electrode by the inverse piezoelectric effect at that time is displayed as a vector F. The force F shown in FIG. 3A 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 becomes an expansion / contraction force that excites longitudinal vibration. Further, as is apparent from the drawing, the force F2 becomes a torsional force that generates a torsional secondary vibration. The same applies to laminated piezoelectric elements that are laminated. These laminated piezoelectric elements 11 are bonded to both surfaces of the elastic body 12 as described above.

  Returning to FIG.

  When an alternating voltage is applied to the A phase of the first laminated piezoelectric element 25, the alternating force of the vector, which is the force F in the figure, acts for the reason described above. Although not shown, when an alternating voltage is applied to the B phase of the second laminated piezoelectric element 26 on the back surface, an alternating force having a force F in the same vector direction is also generated.

  When an alternating voltage having the same phase and corresponding to the resonance frequency of the longitudinal primary vibration or torsional secondary vibration of the vibrator 11 is applied to the A phase and the B phase, the alternating force of the vector F is synthesized and twisted. The force is canceled and only the longitudinal primary resonance vibration is generated.

  Next, an alternating voltage having the above-mentioned frequency having an opposite phase (phase difference π) is simultaneously applied to the A phase and the B phase. Then, the vector F is generated in the opposite phase in the first laminated piezoelectric element 25 and the second laminated piezoelectric element 26. Therefore, the expansion / contraction force is canceled, and conversely, the torsional force works and only the torsional resonance secondary vibration is generated.

  Next, consider a case where a phase difference other than 0, π, 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. 2 (b), the rotor 15 is rotated to the position of the frictional contact members 12a and 12b of the vibrator 11 in the clockwise direction (CW direction) or counterclockwise direction (CCW). Direction) elliptical vibrations are formed.

  When elliptical vibration is generated at the positions of the frictional contact members 12a and 12b of the vibrator 11, the pressed rotor 15 is clockwise (CW direction) or counterclockwise (in accordance with the rotational direction of the elliptical vibration). The rotation operation is performed in the direction of (CCW direction).

  The remaining pair of lower interdigitated electrodes 27 have their twisting directions reversed so that the directions of the interdigitated electrodes are set to be obtuse, and the other driving principles are described above. Since this is the same as the case of the upper cross finger electrode 26, the description is omitted.

  Next, the vibration detection operation by the piezoelectric sheet (2) 25b shown in FIG. 3 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. In that case, in FIG. 2, 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 strain.

  Therefore, when only the longitudinal primary resonance vibration is generated, the C phase and the D phase are connected in parallel in the forward direction (the C + phase and the D + phase are connected, and the C− phase and the D− phase are connected: the parallel forward connection phase). Then, a voltage proportional to the magnitude and phase of the longitudinal primary resonance vibration can be obtained. 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 secondary vibration is generated, it occurs between the C phase and the D phase connected in reverse (connecting the C + phase and the D− phase and connecting the C− phase and the D + phase). A voltage proportional to the magnitude and phase of the torsional secondary vibration can be 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, it is possible to detect longitudinal primary vibration or torsional secondary vibration independently by selecting a connection method between the C phase and the D phase.

  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 the resonance frequency of the torsional secondary vibration. It is known to take a predetermined value Ω during operation. 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 when there is a change in the resonance frequency due to fluctuations, it is always possible to drive near the torsional secondary resonance frequency. Therefore, it is always possible to efficiently drive at the optimum frequency. This is also possible with the same concept when driving near the longitudinal primary resonance frequency.

  Thus, according to the first embodiment, it is not necessary to provide a groove in a part of the elastic body, and it is not necessary to provide a hole in the piezoelectric element. Therefore, not only the configuration becomes simple and the trial production becomes easy, but also stable motor characteristics can be obtained.

  Furthermore, in this embodiment, since the piezoelectric element has a laminated structure, low voltage driving is possible. In addition, since a vibration detection phase is also provided, it is possible to always drive at an optimum frequency using the signal.

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

  FIGS. 7A and 7B show the configuration of the laminated piezoelectric element in the first modification of the first embodiment of the present invention. FIG. 7A is an exploded perspective view, and FIG. 7B is the laminated piezoelectric element of FIG. The figure which looked at the element from the left direction, (c) is the figure which looked at the laminated piezoelectric element of (a) from the right direction.

  In the modification described below, only the configuration of the laminated piezoelectric element is different from the first embodiment described above. Therefore, here, the configuration of the multilayer piezoelectric element will be described, and the basic configuration and operation of the other ultrasonic motors are the same as those in the first embodiment described above. Parts are denoted by the same reference numerals, and illustration and detailed description thereof are omitted.

  In FIG. 7A, the internal electrodes of the piezoelectric sheet (1) 25a are the same as those in the first embodiment described above, but the end drawing position of the upper cross finger electrode 32 and the lower cross finger electrode 33 are the same. The drawing position to the end is different.

Further, in the first modification, after the n laminated piezoelectric sheet, and a piezoelectric sheet (3) 25c of the internal electrode is not provided finally laminated one, constitutes a laminated piezoelectric element 25 ₂ .

In FIG. 7B, on the right side surface of the laminated piezoelectric element 25 ₂ , an external electrode 33a ₁ (33b ₁ ) having an A + (B +) phase as a driving phase is provided on the upper side, and C + ( An external electrode 33c ₁ (33d ₁ ) of the D +) phase is provided. Similarly, on the left side surface of the laminated piezoelectric element 25 ₂ , an A- (B−) phase external electrode 33a ₂ (33b ₂ ) as a driving phase is provided at the upper portion, and C- (D−) as a vibration detection phase is provided at the lower portion. A phase external electrode 33c ₂ (33d ₂ ) is provided.

Note that the overall configuration and driving method of the multilayer piezoelectric element 25 ₂ are the same as those described in the first embodiment, and a description thereof will be omitted here.

  According to the first modification, all the signals of the lower cross finger electrodes can be used as the vibration detection signal, so that a large vibration detection signal can be obtained.

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

  FIGS. 8A and 8B show the structure of the laminated piezoelectric element according to the second modification of the first embodiment of the present invention. FIG. 8A is an exploded perspective view, and FIG. 8B is the laminated piezoelectric element of FIG. It is the figure which showed the external electrode of the element.

  In the second modified example, the piezoelectric sheet (1) 25a has a cross finger electrode 35 on one side (right finger cross finger electrode) for A + (B +) phase, for example, and the piezoelectric sheet (2) 25b has For example, the cross finger electrode 36 on the other side (left finger cross finger electrode) for the A- (B-) phase is printed. The cross finger electrode 36 is arranged with its height direction (c direction in FIG. 2B) shifted so that the finger portion is between the finger portions of the cross finger electrode 35.

  And the piezoelectric sheet (1) 25a and the piezoelectric sheet (2) 25b are laminated | stacked alternately, and the piezoelectric sheet (3) 25c in which the electrode is not printed is laminated | stacked finally.

As shown in FIG. 8b, the external electrode is provided with only the drive phase A (B) phase in the second modification. Note that the A + (B +) phase external electrode 37a ₁ (37b ₁ ) is shown here, but the same applies to the A− (B−) phase external electrode 37a ₂ (37b ₂ ).

  FIG. 9 is a diagram showing the state of polarization according to the second modification of the first embodiment of the present invention.

  As described above, since the positive electrode (A + (B +) phase) and the negative electrode (A- (B-) phase) of the internal electrode are alternately laminated, the direction of polarization is slightly different as shown in FIG. Formed with an angle ξ. That is, the piezoelectric sheet (1) 25a and the piezoelectric sheet (2) 25b are paired to serve as a cross finger electrode.

  Therefore, in the first embodiment in which the positive electrode and the negative electrode are in the plane, it is assumed that a discharge phenomenon occurs during polarization when the electrode protrudes or the like, but in the second modification example, The phenomenon can be prevented.

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

  FIGS. 10A and 10B show the structure of the laminated piezoelectric element according to the third modification of the first embodiment of the present invention. FIG. 10A is an exploded perspective view, and FIG. 10B is the laminated piezoelectric element of FIG. It is the figure which showed the external electrode of the element.

The difference between the third modification and the second modification described above is that the upper cross finger electrodes 41 and 43 function as drive electrodes and the lower cross finger electrodes 42 and 44 function as vibration detection electrodes. The external electrodes are a driving external electrode 45a ₁ (45b ₁ ) and a detection external electrode 45c ₁ (45d ₁ ).

  According to the third modification, it is possible to add a vibration detection phase as compared with the second modification described above.

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

  In the fourth modification, elliptical vibration is obtained by simultaneously exciting the longitudinal primary vibration mode and the torsional tertiary vibration mode of the vibrator.

  FIG. 11 shows the structure of a laminated piezoelectric element according to a fourth modification of the present invention. (A) is a diagram showing examples of piezoelectric sheets and internal electrode patterns, and (b) is a diagram of (a). The perspective view seen from the direction of the piezoelectric sheet (3) 25c, (c) is the figure seen from the right side direction, (d) is the figure seen from the left side direction.

The piezoelectric sheet (1) 25a is provided with cross finger electrodes 46, 47 and 48 at three locations. Then, after n sheets of piezoelectric sheets (1) 25a having such a configuration are stacked, one sheet of piezoelectric sheet (2) 25b having the same internal electrode pattern and different lead-out position to the end is stacked, and finally the internal electrodes Are laminated to form a laminated piezoelectric element 25 ₄ . In this case, the internal electrode pattern of the piezoelectric sheet (1) 25a is for the drive electrode, and the internal electrode pattern of the piezoelectric sheet (2) 25b is the detection electrode.

  Here, with reference to FIG. 11B, the positions of the three crossed finger electrodes 46, 47 and 48 will be described.

  The position of the upper cross finger electrode 46 is provided at a position corresponding to the upper node position 51 of the torsional tertiary vibration mode. Further, the position of the central cross finger electrode 47 is provided at a position corresponding to the node position in the longitudinal primary vibration mode and the central node position 50 in the torsional tertiary vibration mode. Furthermore, the position of the lower cross finger electrode 48 is provided at a position corresponding to the lower node position 52 of the torsional tertiary vibration mode.

The external electrodes are an A + (B +) phase external electrode 49a ₁ (49b ₁ ) and an A- (B−) phase external electrode 49a at the lead-out position of the end in the portion where the piezoelectric sheet (1) 25a is laminated. ₂ (49b ₂ ) is provided. Further, the lead-out position of the end portion of the piezoelectric sheet (2) 25b has a C + (D +) phase external electrode 49c ₁ (49d ₁ ) and a C- (D−) phase external electrode 49c ₂ (49d ₂ ). Is provided.

That is, as shown in FIGS. 11C and 11D, the detection external electrodes 49c ₁ (49d ₁ ) and 49c ₂ (49d ₂ ) are the drive external electrodes 49a ₁ (49b ₁ ) and 49a. ₂ (49b ₂ ) is provided at a lower position.

When the vibrator is configured using the laminated piezoelectric element 25 ₄ of the fourth modification, the ratio of the short side a to the long side b of the vibrator needs to be set to about 0.3. . Specifically, the dimensions of the vibrator are a = 3 mm, b = 10 mm, and c = 20 mm.

  As described above, according to the fourth modification, the vibrator has the common node (central part) of the longitudinal primary vibration mode and the torsional tertiary vibration mode, and thus the vibrator is held at that position. Is possible.

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

  FIGS. 12A and 12B show the configuration of the vibrator in the fifth modification of the first embodiment of the present invention. FIG. 12A is an exploded perspective view, and FIG. 12B is the first piezoelectric element of FIG. The figure which showed the electrode pattern of (a), (c) is the figure which showed the electrode pattern of the 2nd piezoelectric element of (a).

  In the first embodiment and the first to fourth modifications described above, the piezoelectric element has been a laminated piezoelectric element, but in the fifth modification, a single-plate piezoelectric element is used.

That is, the first piezoelectric element 55 and the second piezoelectric element 56 on which the electrode patterns of the interdigitated electrodes are printed are fixed to both side surfaces of the elastic body 21 by adhesion. The electrode pattern of the piezoelectric element is the same as that of the first modification described above. The interdigital electrodes 57a _1, 57a ₂ of the first piezoelectric element 55 side, A + phase derivation unit 58a ₁ and the A- is derived portion 58a ₂ of the phases provided for the drive electrodes, interdigital 58a _1, The 58a ₂ is provided with a C + phase derivation unit 58c ₁ and a C− phase derivation unit 58c ₂ for the detection electrode. Similarly, the interdigital electrodes 57b ₁ and 57b ₂ on the second piezoelectric element 56 side are provided with a B + phase deriving portion 58b ₁ and a B− phase deriving portion 58b ₂ for driving electrodes. 58b ₁ and 58b ₂ are provided with a D + phase derivation unit 58d ₁ and a D− phase derivation unit 58d ₂ for the detection electrodes.

  According to the fifth modification, although it is not possible to lower the drive voltage, the motor can be configured using a simple piezoelectric element.

  As other modifications, although not shown in the drawing, it is possible to provide all the external electrodes of the laminated piezoelectric element used in the first embodiment described above on one side surface. The effect is that external wiring by a flexible substrate or the like becomes easy.

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

  FIGS. 13A and 13B show the configuration of the vibrator of the ultrasonic motor according to the second embodiment of the present invention. FIG. 13A is an exploded perspective view, and FIG. 13B shows the assembled state of the vibrator of FIG. The perspective view shown, (c) is the figure which looked at the vibrator of (b) from the top.

  The second embodiment differs from the first embodiment described above only in the configuration of the elastic body and the shaft. Therefore, here, the configuration of the elastic body and the shaft will be described, and the basic configuration and operation of other ultrasonic motors are the same as those in the first embodiment described above. The same reference numerals are assigned to the portions, and illustration and detailed description thereof are omitted.

As shown in the figure, the elastic body 61 made of stainless steel or brass having a rectangular parallelepiped shape is provided with grooves 62 in the vertical direction from the upper side and the lower side to the vicinity of the center. The first main body portion 61 ₁ and the second main body portion 61 ₂ cut by the groove portion 62 are integrally configured by the joint portion 61 _{3 at the} central portion. Further, this junction 61 _3, angled shaft 63 that extends along the groove 62 are formed integrally. Further, a round shaft 64 is formed integrally with the square shaft 63 in the axial direction. That is, the first body portion 61 ₁ of the elastic body 61, the second body portion 61 _2, junction 61 _3, the angled shaft 63. round shaft 64 are all integrally formed.

  And the 1st lamination piezoelectric element 65 and the 2nd lamination piezoelectric element 66 are pasted up on both sides of elastic body 61 using adhesives like the 1st embodiment mentioned above.

  The surface of the square shaft 63 facing the first laminated piezoelectric element 65 and the second laminated piezoelectric element 66 has a gap between the surface of the first laminated piezoelectric element 65 and the second laminated piezoelectric element 66. . Accordingly, as shown in FIG. 13C, the portion of the square shaft 63 is not in contact with the laminated piezoelectric elements 65 and 66.

  A part of the round shaft 64 is provided with a screw portion (not shown).

  In addition, the round shaft 64 is formed integrally with the square shaft 63 in this embodiment, but the round shaft 64 and the square shaft 63 may be fastened with a screw or the like, for example.

  According to the second embodiment, the following effects can be obtained.

  When the vibrator becomes smaller, it is difficult to make a through hole in the elastic body and provide a female screw portion at the center as shown in the first embodiment. In that case, as in the second embodiment, the problem is solved by providing a shaft integrally with the elastic body in advance. Further, the shaft can be prevented from vibrating as much as possible by reducing the size of the joint as much as possible.

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

  FIGS. 14A and 14B show the configuration of a vibrator of an ultrasonic motor according to a modification of the second embodiment of the present invention. FIG. 14A is an exploded perspective view, and FIG. 14B is an assembly of the vibrator of FIG. It is the perspective view which showed the state.

  In the modification described below, only the configuration of the vibrator is different from the above-described second embodiment. 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 second embodiment described above. Are denoted by the same reference numerals, and illustration and detailed description thereof are omitted.

  As shown in FIG. 14, in this modification, compared with the second embodiment described above, two groove portions 62 are provided only in the upper half of the elastic body 70, and a round shaft 64 formed continuously is provided. The square shaft 63 is integrally formed with the elastic body 68 at the joint portion 69.

  If comprised in this way, the process area | region of an elastic body will decrease compared with 2nd Embodiment mentioned above, and a simpler elastic body and vibrator | oscillator can be obtained.

  In the above-described embodiment, the electrode provided on the side surface portion of the piezoelectric element has been described as the cross finger electrode. However, the present invention is not limited to this.

  In the above-described embodiment, the dimensions of the sides a × b × c (the length in the central axis direction) are only preferable examples, and are described below according to the device to be applied and the intended use. It can be changed as appropriate. For example, with respect to the ultrasonic motor after completion of production, the rectangular ratio a / b composed of the short side a and the long side b has a longitudinal primary resonance vibration and a torsional secondary (or tertiary) resonance as shown in FIG. A predetermined ratio (rectangular ratio corresponding to the intersection in the figure) in which the resonance frequencies of the vibrations coincide and indicate the same value is most preferable, and each resonance frequency corresponding to the vicinity range (for example, within ± 0.02) is most preferable. Even if the rectangular ratios are almost the same, they can be used almost 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 obtained as an invention.

  According to the present invention, there is no need for a groove portion, and there is no need to provide a hole portion in the piezoelectric element, so that longitudinal resonance vibration and torsional resonance vibration can be easily excited with a simple structure, and an ellipse generated in an ultrasonic transducer. The rotor can be rotated by vibration.

10 ... ultrasonic motor, 11 ... transducer, 12a, 12b ... frictional contact _{member, 13,13a 1, 13a 2, 13b} 1, 13b 2, 13c 1, 13c 2, 13d 1, 13d 2 ... external electrode, 15 ... Shaft, 16 ... rotor, 17 ... spring, 18 ... spring retaining ring, 19 ... shaft, 21 ... elastic body, 22 ... through hole, 23 ... female thread, 25 ... first laminated piezoelectric element, 25a ... piezoelectric sheet 1 (piezoelectric) Sheet (1)), 25b ... Piezoelectric sheet 2 (piezoelectric sheet (2)), 25c ... Piezoelectric sheet 3 (piezoelectric sheet (3)), 26 ... Second laminated piezoelectric element, 27 ... Upper cross finger electrode (internal electrode) , 28. Lower cross finger electrodes (internal electrodes).

Claims (15)

A substantially rectangular parallelepiped vibrator having a substantially 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 comprising at least a rotor that is driven to rotate about the rotation axis,
The vibrator has a substantially rectangular parallelepiped shape having a first side surface including one side of the substantially rectangular shape and a second side surface paired with the first side surface, wherein the cross section perpendicular to the central axis is substantially rectangular. An elastic body, a first piezoelectric element disposed opposite to the first side surface of the elastic body, a second piezoelectric element disposed opposite to the second side surface of the elastic body,
Comprising
The elliptical vibration is formed by synthesizing the longitudinal primary resonance vibration of the vibrator extending and contracting in the rotation axis direction and the torsional secondary resonance vibration or the torsional tertiary resonance vibration having the rotation axis as the torsion axis. And rotating the rotor. The direction of polarization of the first piezoelectric element is substantially in the in-plane direction of the first side surface of the elastic body, and an angle α formed with the central axis when viewing the central axis direction is
0 <α <π / 2
Are joined to satisfy
The direction of polarization of the second piezoelectric element is substantially in the in-plane direction of the second side surface of the elastic body, and an angle β formed with the central axis when the central axis direction is viewed is
β = −α
The ultrasonic motor according to claim 1, wherein the ultrasonic motor is joined so as to satisfy.   The ultrasonic motor according to claim 2, wherein the polarization is formed at a position including at least one of the two nodes of the torsional secondary resonance vibration.   The ultrasonic motor according to claim 2, wherein the polarization is formed at a position including at least one of the three nodes of the torsional tertiary resonance vibration.   5. The polarization of the first piezoelectric element and the polarization of the second piezoelectric element are formed by intersecting finger electrodes in which a plurality of electrode patterns are arranged to intersect with each other. The ultrasonic motor according to item 1.   The ultrasonic motor according to claim 5, wherein the cross finger electrode includes a drive electrode and a vibration detection electrode.   The first piezoelectric element and the second piezoelectric element are stacked piezoelectric elements having a structure in which a plurality of piezoelectric sheets in which the interdigitated electrodes are inclined at a predetermined angle with respect to the central axis are stacked. The ultrasonic motor according to claim 5, wherein the ultrasonic motor is provided.   By applying alternating voltages having different phases to the driving interdigital electrodes of the first piezoelectric element and the interdigital driving electrodes of the second piezoelectric element, the longitudinal primary resonance vibration and the torsional secondary resonance vibration or The ultrasonic motor according to claim 5, wherein a torsional tertiary resonance vibration is simultaneously excited to generate the elliptical vibration, and the rotor is rotated in a predetermined direction.   A signal from the vibration detection electrode of the first piezoelectric element and a signal from the vibration detection electrode of the second piezoelectric element are connected in parallel to detect longitudinal vibration or torsional vibration, respectively. Item 9. The ultrasonic motor according to any one of Items 6 to 8.   The ultrasonic motor according to claim 9, wherein the vibrator detection electrode is formed on the same surface as the driving electrodes of the first piezoelectric element and the second piezoelectric element.   The longitudinal primary resonance vibration of the vibrator extending and contracting in the rotation axis direction and the torsional secondary resonance vibration having the rotation axis as a torsion axis substantially coincide with the rotation axis of the vibrator so as to be approximately the same. The ultrasonic motor according to any one of claims 1 to 10, wherein a ratio of a short side to a long side of the rectangular cross section is set to about 0.6.   The longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis and the torsional tertiary resonance vibration having the rotation axis as a torsion axis substantially coincide with each other so that the resonance frequency of the vibrator is approximately perpendicular to the rotation axis. The ultrasonic motor according to any one of claims 1 to 10, wherein a ratio of a short side to a long side of the rectangular cross section is set to approximately 0.3. A through hole provided in a portion corresponding to the rotation axis of the elastic body;
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 claim 1, further comprising: A shaft integrally provided at a substantially central portion of the elastic body;
A spring that presses against the vibrator the rotor held rotatably with respect to the shaft;
The ultrasonic motor according to claim 1, further comprising:   2. The ultrasonic motor according to claim 1, wherein the first side surface and the second side surface of the elastic body are surfaces including a long side direction of the substantially rectangular cross section of the elastic body.

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