JP2010166674A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor which eliminates in 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 a parallelepiped vibrator 11 whose cross section vertical a central axis is almost rectangular, and the rotor 15 which is rotationally driven with the central axis orthogonal to the ellipse vibration generation face as a rotating axis while being in contact with the ellipse vibration generation face of the laminated piezoelectric elements 11. The vibrator 11 is composed of a parallelepiped elastic body 21 whose cross section is vertical with respect to the central axis, and a laminated piezoelectric element 25 arranged so as to oppose one 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 direction of the vibrator 11, 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 elastic body having a side surface including one side and a second side surface that is paired with the first side surface; and a piezoelectric element disposed opposite to the first side surface of the elastic body. Then, 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 or the torsional tertiary resonance vibration having the rotation axis as the torsion axis, the elliptical vibration is reduced. The rotor is formed and rotated.

  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. 1A and 1B show the vibrator of FIG. 1, in which FIG. 1A is an exploded perspective view of the vibrator, FIG. 1B is an external 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 an internal electrode pattern, and FIG. 2B is an intersection formed on a vibrator surface. 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 laminated piezoelectric element shown by (a). FIG. 4 is a cross-sectional view including the polarization direction shown along line AA ′ in FIG. 3A 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. FIG. 7 is an exploded perspective view showing a configuration of a vibrator in a first modification of the first embodiment of the present 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. It is the figure which showed the mode of the polarization by the 3rd modification of the 1st Embodiment of this invention. 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, FIG. 2B is an external perspective view of the vibrator, and FIG. 2C is a top view of the vibrator.

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

  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.

The external electrode 13 is arranged on the side surface of a laminated piezoelectric element 25 (details will be described later) 25 constituting the vibrator 11 in order from the top: A-phase 13a ₂ , C-phase 13c ₂ , B-phase 13b ₂ , D-phase. 13d ₂ is provided. Although not shown, an A + phase, a C + phase, a B + phase, and a D + phase are provided on the opposite side surface of the multilayer piezoelectric element 25.

  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, and an elastic body 21 made of a metal material such as stainless steel or brass, and a rectangular parallelepiped laminated piezoelectric element 25 is bonded to one side surface of the elastic body 21 with an adhesive. It is configured. As shown in FIG. 2B, the elastic body 21 has a through-hole so that the shaft 19 can be inserted into a substantially central portion when the laminated piezoelectric element 25 is bonded to the side surface to constitute the vibrator 11. 22 is formed. That is, the through hole 22 is provided at a position eccentric from the central portion of the elastic body 21.

  A female screw portion 23 for holding the shaft 19 is provided at the axial central portion of the through hole 22, 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 coincides with the node portion of the longitudinal primary vibration of the vibrator 11 and the node portion of the torsional secondary vibration.

  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 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. 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 (first crossed finger electrode (internal electrode) 29 and second crossed finger electrode (internal electrode) 30) 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. Further, a part of the first cross finger electrode 29 and the second cross finger electrode 30 is drawn to the end of the piezoelectric sheet so as to be electrically connected to the external electrodes 13a ₁ , 13a ₂ and 13b ₁ , 13b _2. Electrode lead-out portions 29 ₁ , 29 ₂ and 30 ₁ , 30 ₂ are provided.

  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 between the direction of the central axis (shown by a broken line) and the direction of the finger 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 second interdigitated electrode 30 shown in FIG. 3A is similarly θ as shown. N sheets of the piezoelectric sheets (1) 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. However, the third cross finger electrode 31 and the fourth cross finger electrode 32 are different in the positions of the electrodes extending to the ends. Is provided. The third cross finger electrode 31 and the fourth cross finger electrode 32 are used as electrodes for vibration detection. Part of the third cross finger electrode 31 and the fourth cross finger electrode 32 is drawn out to the end of the piezoelectric sheet so as to be electrically connected to the external electrodes 13c ₁ , 13c ₂ and 13d ₁ , 13d _2. Electrode lead-out portions 31 ₁ , 31 ₂ and 32 ₁ , 32 ₂ are provided.

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 cross finger electrode of the present embodiment is such that the center portion of the upper first cross finger electrode 29 is provided near the upper node position of the torsional secondary vibration, and the center portion of the lower second cross finger electrode 30 is It is provided in the vicinity of the lower node position of the torsional secondary vibration.

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

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

  The laminated piezoelectric element 25 having such a configuration is bonded to the elastic body 21.

  Next, a method for producing the laminated piezoelectric element 25 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 element 25.

  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, 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. 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. Specifically, as described above, a = 6 mm, b = 10 mm, and c = 20 mm.

From the resonance vibration diagram of each mode shown in FIG. 5, the node portion of the longitudinal primary vibration mode is the substantially central portion (node 35 ₁ ) indicated by the alternate long and short dash line in FIG. As for the nodes in the vibration mode, the upper and lower node positions (nodes 35 ₄ and 35 ₅ ) indicated by the alternate long and short dash line in FIG. 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 the present embodiment will be described using the first crossed finger electrode 29 shown in FIG.

  First, the operation of the vibrator 11 using the driving cross finger electrodes (the first cross finger electrode 29 and the second cross finger electrode 30 of the piezoelectric sheet (1) 25a) will be described.

  In the A phase (A + phase, A− phase) and the B phase (B + phase, B− phase) shown in FIG. 2B and FIG. 3B, the resonance frequency of the longitudinal primary vibration or torsional secondary vibration is set. A corresponding alternating voltage is applied.

  In FIG. 3A, the forces generated in the vicinity of the first cross finger electrode 29 and the second cross finger electrode 30 by the inverse piezoelectric effect at that time are displayed as vectors F and F ′, respectively. Forces F and F ′ shown in FIG. 3A are alternating forces. When these forces are vector-decomposed, they become F1 and F2 and F1 ′ and F2 ′. As is apparent from the figure, the forces F1 and F1 ′ become expansion and contraction forces that excite longitudinal vibration. Further, as is apparent from the drawing, the forces F2 and F2 'are torsional forces that generate torsional secondary vibration. The same applies to the laminated piezoelectric elements that are laminated. These laminated piezoelectric elements 25 are bonded to one side surface of the elastic body 12 as described above.

  Returning to FIG.

  When an alternating voltage is applied to the A phase of the laminated piezoelectric element 25, for the reason described above, the alternating force of the vector, which is the force F in the figure, acts. Further, when an alternating voltage is applied to the B phase, 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 vectors F and F ′ is changed. When combined, the torsional 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, since the vectors F and F ′ are generated in opposite phases, the expansion / contraction force is canceled, and on the contrary, the torsional force works, and only the torsional resonance secondary vibration is generated.

  Next, consider a case where a phase difference other than 0 and π is simultaneously applied 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).

  Next, the vibration detection operation by the third cross finger electrode 31 and the fourth cross finger electrode 32 of 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.

  FIG. 7 is an exploded perspective view showing the configuration of the vibrator in the first modification of the first embodiment of the present invention.

  In the first embodiment described above, a laminated piezoelectric element has been used as the piezoelectric element constituting the vibrator. However, in the first modification, a single plate piezoelectric element is used.

  In the first modification described below, only the configuration of the vibrator is different from the first embodiment described above. 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.

  That is, the single-plate piezoelectric element 37 on which the electrode pattern of the interdigitated electrode is printed on one side surface of the elastic body 21 is fixed by adhesion. Here, the surface on which the electrode pattern is printed is opposite to the surface facing the elastic body 21. The electrode pattern of the piezoelectric element is the same as that in the first embodiment. As a cross finger electrode of the single-plate piezoelectric element 37, an upper first cross finger electrode 29 and a lower second cross finger electrode 30 are provided.

  According to the first modification, since a single plate is used as the piezoelectric element, the configuration can be simplified.

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

  Although not shown in the drawings, the second modified example can use a twisted tertiary resonance vibration instead of the twisted secondary resonance vibration. In that case, it is necessary to set the dimensional ratio of the length of the short side / the length of the long side (a / b) of the vibrator 11 to approximately 0.3 (see FIGS. 5 and 6).

  Since the basic configuration and operation of the other ultrasonic motor in the second modification are the same as those in the first modification of the first embodiment described above, they are the same to avoid duplication of explanation. The same reference numerals are assigned to the portions, and illustration and detailed description thereof are omitted.

  According to the second modification, the vibrator can be held without using the shaft described in the first embodiment. That is, the common node of the longitudinal primary resonance vibration and the torsional tertiary resonance vibration is at the center of the outer surface of the vibrator, as is apparent from FIG. It can be carried out.

(Third Modification)
Next, a third modification of 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 third 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 third modification, the piezoelectric sheet (1) 25a includes, for example, a first cross finger electrode 29a ₁ and a second cross finger electrode on one side (right finger cross finger electrode) for A + phase and B + phase. 30b ₁ is provided on the piezoelectric sheet (2) 25b, for example, the first cross finger electrode 29a ₂ and the second cross finger electrode 30b ₂ on the other side (left finger cross finger electrode) for A-phase and B-phase. Are printed. The first cross finger electrodes 29a ₁ and 29a ₂ are shifted in the height direction (c direction in FIG. 2B) so that the finger portions are between the finger portions of the first cross finger electrode 29. Has been placed. Similarly, the second cross finger electrodes 30b ₁ and 30b ₂ are arranged with their height directions shifted so that their finger portions are between the finger portions of the second cross finger electrode 30.

  Such piezoelectric sheets (1) 25a and piezoelectric sheets (2) 25b are alternately stacked, and finally a piezoelectric sheet (3) 25c on which no electrode is printed is stacked.

As shown in FIG. 8B, the external electrodes are provided with only the driving phase A phase and the B phase in the third modification. Here, the A + phase external electrode 13a ₁ and the B + phase external electrode 13b ₁ are shown, but the same applies to the A− phase external electrode 13a ₂ and the B− phase external electrode 13b ₂ .

  FIG. 9 is a diagram showing the state of polarization according to the third 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 the polarization when the electrode protrudes or the like, but in the third modification example, The phenomenon can be prevented.

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

  10A and 10B show the configuration of the vibrator of the ultrasonic motor according to the second embodiment of the present invention. FIG. 10A is an exploded perspective view, and FIG. 10B 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 41 made of stainless steel or brass having a rectangular parallelepiped shape is provided with groove portions 42 in the vertical direction from the upper side surface and the lower side surface to the vicinity of the center portion. And the 1st main-body part 41 ₁ and the 2nd main-body part 41 ₂ which were cut | disconnected by this groove part 42 are comprised integrally by the junction part 41 ₃ of the said center part. In addition, a rectangular shaft 43 extending along the groove 42 is integrally formed with the joint 41 ₃ . Further, a round shaft 44 is formed integrally with the square shaft 43 in the axial direction. That is, the first body portion 41 ₁ , the second body portion 41 ₂ , the joint portion 41 ₃ , the square shaft 43, and the round shaft 44 of the elastic body 41 are all integrally formed.

  And the laminated piezoelectric element 25 is adhere | attached on the one side surface of the elastic body 41 using the adhesive agent similarly to 1st Embodiment mentioned above.

  A surface of the square shaft 43 facing the multilayer piezoelectric element 25 has a gap between the surface of the multilayer piezoelectric element 25. Accordingly, as shown in FIG. 10C, the portion of the square shaft 43 is not in contact with the laminated piezoelectric element 25.

  A part of the round shaft 44 is provided with a screw portion (not shown).

  In addition, the round shaft 44 is formed integrally with the square shaft 43 in this embodiment, but the round shaft 44 and the square shaft 43 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.

  11A and 11B show the configuration of the vibrator of the ultrasonic motor according to the modification of the second embodiment of the present invention. FIG. 11A is an exploded perspective view, and FIG. 11B 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. 11, in this modification, compared with the second embodiment described above, two groove portions 42 are provided only in the upper half of the elastic body 51, and the round shaft 44 formed continuously The square shaft 43 is integrally formed with the elastic body 51 at the joint portion 52.

  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 corresponding to the vicinity range (for example, within ± 0.02). Even in a rectangular ratio in which the frequencies are almost the same, it 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 ... Rotor, 16 ... bearing, 17 ... spring, 18 ... spring retaining ring, 19 ... shaft, 21 ... elastic body, 22 ... through hole, 23 ... female thread, 25 ... laminated piezoelectric element, 25a ... piezoelectric sheet 1 (piezoelectric sheet ( 1)), 25b ... piezoelectric sheet 2 (piezoelectric sheet (2)), 25c ... piezoelectric sheet 3 (piezoelectric sheet (3)), 29 ... first cross finger electrode (internal electrode), 30 ... second cross finger electrode ( Internal electrode), 31... Third cross finger electrode (internal electrode), 32... Fourth cross finger electrode (internal electrode).

Claims (14)

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 elastic body having a substantially rectangular cross section perpendicular to the central axis, a side surface including one side of the substantially rectangular shape, and a second side surface that is paired with the first side surface. And a piezoelectric element disposed to face the first side surface of the elastic body,
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 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
The ultrasonic motor according to claim 1, wherein the ultrasonic motor is configured to satisfy.   The ultrasonic motor according to claim 2, wherein the polarization is formed at two node positions of the torsional secondary resonance vibration.   The ultrasonic motor according to claim 2, wherein the polarization is formed at positions of three nodes of the torsional tertiary resonance vibration.   5. The ultrasonic motor according to claim 2, wherein the polarization of the piezoelectric element is formed by an interdigitated electrode in which a plurality of electrode patterns are arranged to intersect each other.   The ultrasonic motor according to claim 5, wherein the cross finger electrode includes a drive electrode and a vibration detection electrode.   6. The laminated piezoelectric element according to claim 5, wherein the piezoelectric element is a laminated piezoelectric element having a structure in which a plurality of piezoelectric sheets in which the interdigitated electrodes are disposed at a predetermined angle with respect to the central axis are laminated. 6. The ultrasonic motor according to 6.   By applying alternating voltages having different phases between the driving interdigital electrodes of the piezoelectric element, the longitudinal primary resonance vibration and the torsional secondary resonance vibration or torsional tertiary resonance vibration are simultaneously excited, and the elliptical vibration is excited. The ultrasonic motor according to claim 5, wherein the ultrasonic motor is generated and rotates the rotor in a predetermined direction.   The ultrasonic motor according to any one of claims 6 to 8, wherein longitudinal vibration or torsional vibration is detected by a signal from a vibration detection electrode of the 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 9, 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 is approximately perpendicular to the rotation axis of the vibrator. The ultrasonic motor according to any one of claims 1 to 9, wherein a ratio of a short side to a long side of the rectangular cross section is set to about 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 a 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 a 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.

Images