JP5129184B2 - Ultrasonic motor - Google Patents

Description

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

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

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

JP-A-9-117168

  However, as shown in FIG. 1, the ultrasonic motor described in 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-described problems, and the object thereof is to eliminate the need for a groove portion, to provide a hole portion in the piezoelectric element, and to easily excite elliptical vibration with a simple structure. It is possible to provide an ultrasonic motor that can rotate a rotor by elliptic vibration generated in an ultrasonic vibrator.

  That is, according to the present invention, an oscillator in which the ratio of each side of the substantially rectangular parallelepiped shape is approximately 1: 1: 0.45 and the generation of the elliptical vibration of the vibrator in contact with the elliptical vibration generation surface of the oscillator An ultrasonic motor including at least a driven body that is driven to rotate about a central axis orthogonal to the surface, and the vibrator is generated on the same surface of the vibrator, and has a short side Contour slip vibration that vibrates both ends in the direction of the rotation axis about the center line of the surface including the surface and flexural vibration that vibrates the both ends in the direction orthogonal to the rotation axis are simultaneously excited with a predetermined phase difference, The driven body is rotationally driven in contact with a generation site of elliptical vibration generated on a surface orthogonal to a surface where the contour sliding vibration and the surface deflection vibration are generated.

  According to the present invention, there is no need for a groove portion, there is no need to provide a hole in the piezoelectric element, elliptic vibration can be easily excited with a simple structure, and the rotor is rotated by elliptic vibration generated in the ultrasonic vibrator. An ultrasonic motor 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 external perspective view of the vibrator, and FIG. 1B is an external perspective view of the vibrator with a friction contact bonded to the vibrator of FIG. . It is a disassembled perspective view which shows the piezoelectric sheet structure of a laminated piezoelectric element. It is sectional drawing of the lamination direction containing the polarization direction shown along the AA 'line of FIG. The vibration state of each vibration mode is shown schematically, (a) schematically shows the vibration state of the contour sliding vibration mode, and (b) schematically shows the vibration state of the surface deflection vibration mode. It is a figure. FIGS. 2A and 2B are diagrams showing a contour sliding vibration mode viewed from a direction perpendicular to the ab surface shown in FIG. 2A, and FIGS. is there. It is the figure which looked at the surface bending vibration mode from the upper surface, (a), (b) is the figure which showed the state from which the phase of vibration mutually shifted | deviated by (pi). It is the figure which showed the center part cross-section 32 part of FIG.5 (b). It is the figure which plotted the c / a value and the resonant frequency of each mode when changing c by setting the side a = b (constant) of the vibrator. It is the figure which showed the mode of distortion (principal distortion) of ab surface at the time of outline sliding vibration generation | occurrence | production. It is the figure which showed the mode of distortion (principal distortion) of ab surface at the time of surface bending vibration generation | occurrence | production. It is a figure for demonstrating the internal electrode pattern for generating a contour sliding vibration and a surface deflection vibration. It is a figure for demonstrating that each vibration mode can be excited from the alternating force F. FIG. It is a disassembled perspective view which shows the structure of the piezoelectric sheet in the 2nd Embodiment of this invention. It is a perspective view which shows the external appearance of the multilayer piezoelectric element in the 2nd Embodiment of this invention. It is a figure for taking out only a piezoelectric sheet (2), and explaining surface deflection vibration. The structure of the vibrator | oscillator concerning the 3rd Embodiment of this invention is shown, (a) is an external appearance perspective view of the surface side, (b) is the top view seen from the back surface side.

  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. 2 (a) is an external perspective view of the vibrator, and FIG. 2 (b) is a diagram of the vibrator with a friction contact bonded to the vibrator of FIG. It is an external perspective view.

  The ultrasonic motor 10 includes a laminated piezoelectric element (vibrator) 11 that constitutes a vibrator, friction contacts 12 a and 12 b, external electrodes 13 (13 a to 13 d), a rotor 15, a bearing 16, and a spring 17. And a spring holding ring 18, a vibrator holder 20, a shaft fixing ring 21, and a shaft 22.

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

  The frictional contacts 12a and 12b are bonded to a surface orthogonal to the longitudinal direction of the laminated piezoelectric element 11, and come into contact with the rotor 15 as a driven body. However, the frictional contacts 12a and 12b are not necessarily required. The external electrodes 13 (13a to 13d) are provided for each phase, the details of which will be described later, in FIGS. 2A and 2B, four locations on the right side of the drawing, and also on the left side although not shown in the drawing. There are four places.

  As shown in FIG. 1, the vibrator 11 is held by a vibrator holder 20 at substantially the center of three side surfaces (in this case, a lower side surface, a right side surface, and a left side surface). From the upper surface portion of the vibrator holder 20, a shaft 22 threaded on the outer periphery toward the central portion of the upper surface of the vibrator 11 is fixedly extended and fixed to the inner surface of the bearing. The outer surface of the bearing 16 is fixed to the inner surface of the rotor 15, and a spring 17 is in contact with the inner portion of the bearing. When the spring holding ring 18 is rotated, the spring 17 is contracted. As a result, the inner surface of the bearing 16 is pressed, and finally, a predetermined pressing force is applied between the rotor 15 and the vibrator 11.

  The vibrator holder 20 is a holding member that is fixed to substantially the center of the vibrator 11 and holds the shaft 22 and the vibrator 11. The vibrator holder 20 is made of an alumite-treated aluminum material or an insulating-treated metal material, and is integrally formed. The vibrator holder 20 connects the upper surface portion 20a through which the shaft 22 penetrates, the side surface portions 20b and 20c disposed so as to cover the side surface of the vibrator 11, and the lower end portions of the side surface portions 20b and 20c. Guide portions 20d and 20e (20e is not shown), and guide portions 20f and 20g (20g are not shown) that are formed to extend from an intermediate portion of the guide portions 20d and 20e in a direction perpendicular to the guide portions 20d and 20e. ), And a bottom surface portion 20h that connects the guide portion 20f and the guide portion 20g.

  Furthermore, the lower end portions of the side surface portions 20b and 20c and the bottom surface portion 20h are geometrically substantially coincided with the node portion of the contour sliding vibration mode and the surface deflection vibration node, as will be described later. The vibrator 11 includes a connection point between the side surface portion 20b and the guide portion 20d, a connection point between the side surface portion 20b and the guide portion 20e, a connection point between the side surface portion 20c and the guide portion 20d, and the side surface portion 20c and the guide portion 20e. Are supported only at the connection point between the guide portion 20f and the bottom surface portion 20h, and the connection point between the guide portion 20g and the bottom surface portion 20h.

  The shaft fixing ring 21 is a member that fixes the vibrator holder 20 and the shaft 22. The longitudinal direction of the shaft 22 is defined as the central axis direction.

  Next, the vibrator 11 will be described in detail.

  As shown in FIG. 2A, the vibrator 11 has a rectangular parallelepiped shape in which the length of each side is a, b, c, and is a laminated piezoelectric element having a laminated structure of piezoelectric ceramics and internal electrodes. Composed.

  In FIG. 2A, an external electrode (A + phase) 13a, an external electrode (B + phase) 13b, an external electrode (C + phase) 13c, and an external electrode (D + phase) 13d are provided on the right side surface. . Although not shown in the figure, the external electrode (A-phase), the external electrode (B-phase), the external electrode (C-phase), and the external electrode (D-phase) are the same on the left side facing the right side. In the position.

  Note that the surface formed by the dimension a and dimension b in front of the figure is defined as the ab surface. Moreover, the back surface opposite to it is defined as ab back surface.

  FIG. 2B shows a state in which the frictional contacts 12 a and 12 b are provided by bonding at a portion where elliptical vibration occurs on the upper surface of the vibrator 11. The frictional contacts 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, elliptical vibrations in the clockwise direction (CW direction) or counterclockwise direction (CCW direction) in the direction of rotating the rotor 16 as shown in the drawing at the positions of the frictional contacts 12a and 12b. Is formed.

  As the outer diameter dimension of the vibrator, for example, a = 10 mm, b = 10 mm, and c = 4.5 mm. The thickness of the friction contact is about 0.1 mm to 1 mm.

  FIG. 3 is an exploded perspective view showing a piezoelectric sheet configuration of the laminated piezoelectric element.

  The laminated piezoelectric element 11 is configured by laminating thin piezoelectric sheets such as lead zirconate titanate (hereinafter referred to as PZT) on which a predetermined internal electrode pattern is formed. The piezoelectric sheet 25 is made of a PZT material having a thickness of about 10 μm to 100 μm. The piezoelectric sheet 1 (hereinafter referred to as a piezoelectric sheet (1)) 25a and the piezoelectric sheet 2 (hereinafter referred to as a piezoelectric sheet (2)) 25b. A piezoelectric sheet 3 (hereinafter referred to as a piezoelectric sheet (3)) 25c, a piezoelectric sheet 4 (hereinafter referred to as a piezoelectric sheet (4)) 25d, and a piezoelectric sheet 5 (hereinafter referred to as a piezoelectric sheet (5)) 25e. It is configured. Among them, the same pattern of the internal electrode 26 is printed on one surface of the piezoelectric sheet (1) 25a, the piezoelectric sheet (2) 25b, the piezoelectric sheet (3) 25c, and the piezoelectric sheet (4) 25d. Only the positions of the extending electrodes on the side surfaces are different. The piezoelectric sheet (5) 25e is a piezoelectric sheet on which no internal electrode is printed.

  In the present embodiment, one piezoelectric sheet (1) 25a is disposed on the outermost side, and a plurality (n) of sheets are provided on the side of the piezoelectric sheet (1) 25a where the internal electrode 26 is provided. A piezoelectric sheet (2) 25b and a plurality (n) of piezoelectric sheets (3) 25c are laminated, and further, one piezoelectric sheet (4) 25d and finally one piezoelectric sheet (5) 25e are arranged. It has been configured. The piezoelectric sheet (1) 25a is provided with an extending electrode 27c for connecting to the external electrode 13c described above, and similarly, the piezoelectric sheet (2) 25b is extended to connect to the external electrode 13a. The electrode 27a is provided on the piezoelectric sheet (3) 25c with an extended electrode 27b for connection to the external electrode 13b, and the piezoelectric sheet (4) 25d is provided with an extended electrode 27d for connection with the external electrode 13d. It has been.

  The internal electrode 26 is made of a silver-palladium alloy and has a thickness of about several μm. The internal electrode 26 has a crossed finger electrode structure as illustrated. Here, the cross finger electrode refers to an electrode in which, for example, + phase electrodes and − phase electrodes are alternately combined. The cross finger electrode is actually formed on one surface of the side surface portion so as to have as large an area as possible on the side surface.

  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. As will be described in detail later, the interdigitated electrodes are provided on substantially the entire surface of the piezoelectric sheet 25 with an inclination of approximately 45 degrees. First, one piezoelectric sheet (1) 25a is laminated. This plays a role of vibration detection. Thereafter, n piezoelectric sheets (2) 25b are stacked (a specific value of n is 21 in the present embodiment, but will be referred to as n hereinafter). This serves as a drive electrode. Next, n piezoelectric sheets (3) 25c are stacked. This also serves as a drive electrode. Thereafter, one piezoelectric sheet (4) 25d is laminated. This plays a role of vibration detection.

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

  One sheet having an internal electrode pattern printed on the piezoelectric sheet (1) 25a before firing, n sheets having the internal electrode pattern printed on the piezoelectric sheet (2) 25b, and an internal electrode on the piezoelectric sheet (3) 25c Prepare n sheets with the printed pattern, one sheet with the internal electrode pattern printed on the piezoelectric sheet (4) 25d, and finally one piezoelectric sheet (5) 25e with no internal electrode printed. And after laminating | stacking these piezoelectric sheets, after pressing and cutting to a predetermined magnitude | size, it bakes at predetermined temperature. Thereafter, the external electrode is printed and baked at a predetermined position. Thereafter, the laminated piezoelectric element 11 is completed by performing polarization.

  Next, polarization will be described with reference to FIG.

  FIG. 4 is a cross-sectional view in the stacking direction including the polarization direction shown along line AA ′ in FIG. 3. The polarization vector indicated by the arrow in FIG. 4 is polarized toward the other pole with a slight bulge from the pole on one side to the center. This vector also coincides with the electric field vector.

  Next, the operation of the vibrator 11 shown in FIG. 2 will be described.

  With respect to the dimensions of the sides a, b, and c of the rectangular parallelepiped vibrator 11 shown in FIG. 2 (a), a = b and c is set to an appropriate value, so that the resonance frequency of the contour sliding vibration can be increased. The resonance frequency of the surface flexural vibration is made to coincide.

  FIG. 5 schematically shows the vibration state of each vibration mode, (a) schematically shows the vibration state of the contour sliding vibration mode, and (b) schematically shows the vibration state of the surface deflection vibration mode. FIG. In (a) and (b), the broken line shows the shape of the stationary state 11a, and the solid line shows the shape of the vibrating modes 11b and 11c in each vibration mode.

  In the contour sliding vibration shown in FIG. 5A, when attention is paid to the upper surface, the end portion has a component that vibrates in the vertical direction. Actually, it vibrates in an oblique direction, but has a vertical vibration component as indicated by an arrow as a component of the vector. However, as is apparent from the figure, the phase of the vertical vibration at both ends of the upper surface is shifted by π. In addition, there are nodal lines 30a, 30b, 30c, and 30d, which are sites that are not displaced or very small, at substantially the center of the four side surfaces.

  Next, in the surface deflection vibration shown in FIG. 5B, when focusing on the upper surface, the end portion has a component that vibrates in the horizontal direction. However, as is clear from the figure, the phases of the horizontal vibrations at both ends of the upper surface are the same phase. In addition, node lines 31a, 31b, 31c, and 31d, which are portions that have no vibration displacement or are very small, exist at substantially the center of the four side surfaces.

  The two vibrations are combined to generate an elliptical vibration at the upper end. However, the nodal lines of the respective vibration modes exist at a common part, and the common line is held when the vibrator 11 is held. Can be held.

  Here, with reference to FIG. 6 thru | or FIG. 8, each vibration mode mentioned above is demonstrated in detail.

FIG. 6 is a view of the contour sliding vibration mode as seen from a direction perpendicular to the ab surface shown in FIG. 2A. FIGS. 6A and 6B show vibration states whose phases are shifted by π. ing. That is, the vibrations 11b ₁ and 11b ₂ indicated by the solid lines represent a state shifted by the phase π. Note that the positions of black circles 33a, 33b, 33c, and 33d shown in FIGS. 6A and 6B substantially correspond to vibration nodes.

FIG. 7 is a view of the surface deflection vibration mode as viewed from above, and (a) and (b) show a state in which the phase of vibration is shifted by π. Here, the vibrations 11c ₁ and 11c ₂ indicated by the solid line represent a state shifted by the phase π. In addition, the illustrated arrow has shown the vibration displacement of each vertex.

  FIG. 8 is a view showing a cross section 32 at the center of FIG. In the cross section at this position, as shown in FIG. 8, both end portions correspond to the positions of the nodal lines 31b and 31d, and the central portion has vibration displacement (bulge). Here, FIGS. 8A and 8B show a state in which the phase of vibration is shifted by π. Such vibration is referred to as a surface deflection vibration mode.

  FIG. 9 is a diagram in which the c / a value and the resonance frequency of each mode are plotted when c is changed with the side a = b (constant) of the vibrator. From this, the resonance frequency of the contour sliding vibration does not depend on c / a and takes a substantially constant value. However, the resonance frequency of surface flexural vibration increases monotonically as the c / a value increases. As a result, it can be seen that the resonance frequency of the contour sliding vibration and the resonance frequency of the surface flexural vibration coincide with each other when the c / a value is approximately 0.45.

  FIG. 10 is a diagram showing a state of distortion (main strain) on the ab surface when the contour sliding vibration is generated. At the time of contour sliding vibration, at a certain moment, as shown in FIG. 10 (a), an elongation distortion occurs in the direction of 45 degrees to the right, and a contraction distortion occurs in a direction perpendicular to it. Has occurred. FIG. 10B is a diagram showing the state of distortion at the moment when the phase of vibration is shifted by π from FIG. In this case, conversely, shrinkage distortion is generated in the direction of 45 degrees to the right, and elongation distortion is generated in the direction orthogonal thereto. Note that 33o represents the center of the ab surface.

  Further, as is clear from FIG. 5A, the distortion on the back side of ab is also distorted by the same sign. In addition, the positive / negative of a strain defines an elongation strain as positive and a shrinkage strain as negative.

  FIG. 11 is a diagram showing a state of distortion (main strain) on the ab surface when surface deflection vibration occurs. At the time of surface deflection vibration, at a certain moment, as shown in FIG. 11 (a), there is an elongation strain in the direction of 45 degrees to the right, and also in the direction perpendicular to it. Similarly, elongation strain occurs. The state of distortion at the moment when the vibration phase is shifted by π is shown in FIG. In this case, conversely, shrinkage distortion occurs in the direction of 45 degrees to the right, and shrinkage distortion similarly occurs in the direction orthogonal thereto.

  As is clear from FIG. 5B, it should be noted that the sign of the distortion on the back surface of the ab is distorted with the sign opposite to the sign of the ab surface.

  Next, an internal electrode pattern for generating such contour sliding vibration and surface deflection vibration will be described with reference to FIG.

  When the internal electrode pattern 26 is a crossed finger electrode inclined by approximately 45 degrees, as shown in FIG. 4, substantially in-plane polarization occurs between the positive and negative crossed finger electrodes. When an alternating voltage corresponding to the resonance frequency is applied to the interdigitated electrode during driving, a tensile force F as shown in FIG. This is a force due to the piezoelectric longitudinal effect, in which electric lines of force work along the direction of the polarization vector. This force is proportional to the piezoelectric constant e33.

  When an alternating voltage is applied, in fact, a piezoelectric lateral effect is also generated at the same time, and is generated in a direction orthogonal to the force F, although not shown in the figure. The force due to the piezoelectric lateral effect is proportional to the piezoelectric constant e31. However, in general piezoelectric ceramics such as PZT, the absolute value of e31 is generally much smaller than the absolute value of e33. In this embodiment, the piezoelectric lateral effect is not considered. .

  FIG. 12B is a diagram showing the force when the phase of the alternating voltage is shifted by π from the state shown in FIG. In this case, the direction is the same as in the example shown in FIG. In this way, by using the crossed finger electrode inclined at 45 degrees as the internal electrode, an alternating stress inclined at 45 degrees can be generated.

  The fact that each vibration mode can be excited from such an alternating force F will be described with reference to FIG.

  As shown in FIG. 3, the vibrator 11 of the present embodiment has a structure in which piezoelectric sheets on which cross finger electrodes inclined by 45 degrees are printed are laminated. When considering only the driving piezoelectric sheet, n sheets of piezoelectric sheets (2) are formed in the rear half area 112 and piezoelectric sheets (3) are disposed in the front half area 111 with the central surface 35 in FIG. The same number of n sheets are stacked, and are electrically connected to the A phase and B phase of the external electrode, respectively. In the back half region 112 shown in FIG. 13, it may be considered that an arrow force F <b> 1 indicated by a broken line acts due to an alternating voltage applied to the A phase. In addition, it may be considered that the force F2 indicated by the solid line is applied to the front half region 111 by an alternating voltage applied to the B phase.

  Now, when an alternating voltage having the resonance frequency of each mode in the same phase is applied to the A phase and the B phase, forces in the same phase are generated in the rear half region 112 and the front half region 111, and FIG. Considering FIG. 11, the surface deflection vibration does not occur, and only the contour slip vibration occurs. On the other hand, when an alternating voltage having the resonance frequency of each mode is applied to the A phase and the B phase in the opposite phase, an antiphase force is generated in the rear half region 112 and the front half region 111, and similarly Considering FIGS. 10 and 11, no contour slip vibration occurs, and only surface deflection vibration occurs.

  Next, the operation of the ultrasonic motor 10 configured as shown in FIG. 1 will be described.

  As described above, when an alternating voltage having the same phase is applied to the A phase (in this case, the A + phase 13a) and the B phase (in this case, the B + phase 13b) shown in FIGS. Occurs. Further, when alternating voltages having opposite phases are applied to the A phase 13a and the B phase 13b, only surface deflection vibration occurs. When an alternating voltage having a phase difference other than the same phase or opposite phase is applied to the A phase 13a and the B phase 13b, the contour sliding vibration and the surface deflection vibration are simultaneously excited. Since they are simultaneously excited with a predetermined phase difference, elliptical vibration is generated at the upper end of the vibrator 11 as shown in FIG.

  As shown in FIG. 5, when attention is paid to both ends of the upper surface, both ends vibrate in opposite phases in the contour sliding vibration, and in the same phase in the surface deflection vibration. Therefore, when elliptical vibration is occurring, the elliptical vibration at the left end and the elliptical vibration at the right end have opposite directions of rotation and their phases are shifted by π.

  In the ultrasonic motor 10 configured as shown in FIG. 1, as described above, the frictional contacts 12 a and 12 b that are elliptically vibrating contact the rotor 15 to apply a force to the rotor 15. Since the elliptical vibrations of the two frictional contacts 12a and 12b are in opposite directions, a rotational force can be applied to the rotor 15 to rotate the rotor 15. When the phase difference between the A phase 13a and the B phase 13b is reversed, the rotor 15 can be rotated in the opposite direction.

  Next, the vibration detection operation by the piezoelectric sheet (1) 25a and the piezoelectric sheet (4) 25d shown in FIG. 3 will be described.

  The piezoelectric sheet (1) 25a and the piezoelectric sheet (4) 25d are arranged symmetrically with respect to the central surface 35 shown in FIG. The driving piezoelectric sheet (2) 25b and the piezoelectric sheet (3) 25c are the same as those arranged symmetrically with respect to the central surface 35. Although the operation principle at the time of driving has been described above, the operation principle of vibration detection can be considered to be completely opposite.

  That is, as shown in FIG. 10, when only the contour sliding vibration is excited, distortion of the same sign occurs in both the back half region 112 and the near half region 111 of the center surface 35 shown in FIG. 13. doing. As a result, due to the piezoelectric effect, voltages having the same phase and the same magnitude are generated in the piezoelectric sheet (1) 25a and the piezoelectric sheet (4) 25d. Therefore, between the terminal connecting the C phase + and the D phase + and the terminal connecting the C phase-and the D phase-(defined as a parallel forward connection), the magnitude and phase of the contour slip vibration are determined. A proportional signal is output.

  On the other hand, as shown in FIG. 11, when only the plane flexural vibration is excited, in the back half region 112 and the front half region 111 of the center surface 35 shown in FIG. It has occurred. As a result, due to the piezoelectric effect, voltages having the same magnitude in opposite phases are generated in the piezoelectric sheet (1) 25a and the piezoelectric sheet (4) 25d. Therefore, between the terminal connecting the C phase + and the D phase-and the terminal connecting the C phase-and the D phase + (defined as parallel reverse connection), the magnitude and phase of the surface deflection vibration are defined. A signal proportional to is output. Therefore, it is possible to independently detect the contour slip vibration or the surface deflection vibration by selecting a connection method (parallel forward connection or parallel reverse connection) 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 predetermined during operation at the resonance frequency of the surface flexural vibration. It is known to take the value Ω. Therefore, in this case, by adjusting the frequency so that the phase difference between the drive phase and the detection phase is always Ω, the temperature is increased due to the heat generated by the motor itself, the resonance frequency changes due to changes in the ambient temperature, and the load. Even when there is a change in the resonance frequency due to fluctuations, it can always be driven near the resonance frequency of the surface flexural vibration, so that it can always be efficiently driven at the optimum frequency. This is also possible with the same concept when driving near the contour slip 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, it can be driven at a low voltage. Further, since a vibration detection phase is also provided, it is possible to always drive at an optimum frequency using the signal.

  In addition, the vibrator according to the present embodiment has a common node for two vibration modes at the center of the four side surfaces, and can therefore hold the node. In this case, not only can the vibrator be firmly fixed, but also leakage of vibrations through the holding member can be minimized, and thus a highly efficient motor can be realized.

  Note that the inclination of the crossed finger electrode is 45 degrees in the present embodiment, but within the range in which the two modes can be excited, that is, in the range possible in principle described in the present embodiment, at an arbitrary angle near 45 degrees. It can be set. As for the vibrator dimensions, a: b: c is 1: 1: 0.45. For example, the resonance frequency may be shifted due to bonding of the vibrator holder or pressing of the rotor. It is necessary to change the ratio somewhat within the range not departing from the principle described above.

  In the present embodiment, two piezoelectric sheets are used for vibration detection. However, the present invention is not limited to this, and an even number such as four or eight may be used.

  Although not described above for the ultrasonic motor according to the first embodiment, the motor output may be taken out by the gear engagement method with the outer peripheral surface of the rotor being uneven, or from the outer peripheral surface of the rotor via a belt. To extract the output.

  In the vibrator of this embodiment, the vibration detecting piezoelectric sheet is disposed so as to sandwich the driving piezoelectric sheet. Conversely, the driving piezoelectric sheet is disposed so as to sandwich the vibration detecting piezoelectric sheet. It doesn't matter. Further, the vibrator of the present embodiment has a configuration in which a driving piezoelectric sheet and a vibration detecting piezoelectric sheet are laminated, but may be configured only by a driving piezoelectric sheet.

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

  In the second embodiment, 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.

  Also in this embodiment, the outer diameter dimensions (a: b: c) of the vibrator are the same as those in the first embodiment described above.

  FIG. 14 is an exploded perspective view showing the configuration of the piezoelectric sheet in the second embodiment of the present invention.

The laminated piezoelectric element 11 _{1 in} the second embodiment includes a total of two piezoelectric sheets (1) 40a, a total of two piezoelectric sheets (2) 40b, and a total of 2n piezoelectric sheets (3 ) 40c, a total of two piezoelectric sheets (4) 40d, a total of two piezoelectric sheets (5) 40e, and a single piezoelectric sheet 6 (hereinafter referred to as a piezoelectric sheet (6)) 40f. It is configured. Among these, the piezoelectric sheet (1) 40a, the piezoelectric sheet (2) 40b, the piezoelectric sheet (4) 40d, and the piezoelectric sheet (5) 40e leave an insulating portion of, for example, 0.2 to 1 mm at their edges, Electrodes are applied to almost the entire surface. However, the piezoelectric sheet (1) 40a, the piezoelectric sheet (2) 40b, the piezoelectric sheet (4) 40d, and the piezoelectric sheet (5) 40e are provided with the extending electrodes 27b ₁ , 27b ₂ , 27b ₁₁ , 27b, respectively. Only ₁₂ positions are different.

Also, the piezoelectric sheet (3) 40c is printed with the cross finger electrodes 26 similar to those in the first embodiment described above, and is an even number (2n in total: n = 18 in this embodiment). 36 sheets). These piezoelectric sheets (3) are provided with extending electrodes 27a ₁ and 27a ₂ . The piezoelectric sheet (6) 40f is a piezoelectric sheet on which internal electrodes are not printed.

  Hereinafter, it demonstrates according to the order in which a piezoelectric sheet is laminated | stacked.

  First, the piezoelectric sheet (1) 40a, the piezoelectric sheet (2) 40b, the piezoelectric sheet (1) 40a, and the piezoelectric sheet (2) 40b are laminated one by one in this order. Next, 2n piezoelectric sheets (3) 40c are laminated. Thereafter, the piezoelectric sheet (4) 40d, the piezoelectric sheet (5) 40e, the piezoelectric sheet (4) 40d, and the piezoelectric sheet (5) 40e are laminated one by one in this order. Finally, one piezoelectric sheet (6) 40f on which no internal electrode is printed is laminated.

The method for creating the multilayered piezoelectric element (vibrator) 11 ₁ of this embodiment is the same as that of the first embodiment described above, and a description thereof will be omitted.

  Next, with reference to FIG. 15, the appearance of the vibrator of the second embodiment will be described.

In FIG. 15, an external electrode is formed on the right side surface. Of these, the external electrode 13a of the A + phase corresponding to the uppermost position of the piezoelectric sheet (3) 40c extending electrodes 27a ₁ of a position corresponding to the piezoelectric sheet (1) 40a is disposed below the B1 + phase The external electrode 13b ₁ is provided with a B2 + phase external electrode 13b ₁₁ at a position corresponding to the piezoelectric sheet (4) 40d. Although not shown in FIG. 15, the left side also has an A-phase external electrode at the uppermost position corresponding to the extending electrode 27a ₂ of the piezoelectric sheet (3) 40c, and the piezoelectric sheet (2 below). ) B1-phase external electrodes are provided at positions corresponding to 40b, and B2-phase external electrodes are provided at positions corresponding to the piezoelectric sheet (5) 40e.

Since Regarding ultrasonic motor configuration using the vibrator 11 ₁ is the same as in the first embodiment described above, description thereof will be omitted here.

Next, description thus configured for operation of the laminated piezoelectric element 11 _1.

  Referring to FIG. 13, the piezoelectric sheet (3) 40c in the second embodiment is symmetrically arranged with respect to the center surface 35 of the vibrator, and all the piezoelectric sheets (3) are in the A phase. It belongs to. When an alternating voltage corresponding to the resonance frequency is applied to the A phase, only the contour slip vibration is excited.

  Next, surface deflection vibration will be described. Prior to that, only the piezoelectric sheet (2) will be described with reference to FIG.

  FIG. 16A shows the piezoelectric sheet (2) 40b, and the internal electrode 26 is provided on the entire surface thereof. Moreover, the same electrode is provided also in the back surface (electrode which piezoelectric sheet (1) 40a contributes). When an alternating voltage is applied after polarization, a vibration that expands and contracts as shown in FIG. 16B is generated due to the piezoelectric lateral effect.

14 and 15, when an alternating voltage having a resonance frequency is applied between the B1 + phase and the B1-phase of the vibrator, the piezoelectric sheet group of the piezoelectric sheet (1) 40a and the piezoelectric sheet (2) 40b. Tries to vibrate as shown in FIG. That is, the displacement between the 11 ₁ b at the maximum displacement at 11 ₁ a minimum displacement relative to the resting 11 _1. However, since the piezoelectric sheet (3) 40c integrated therewith is not displaced, the entire vibrator is subjected to surface deflection vibration as shown in FIG. 5B.

  Similarly, when an alternating voltage having a resonance frequency is applied between the B2 + phase and the B2-phase of the vibrator, the piezoelectric sheet group of the piezoelectric sheets (4) 40d and (5) 40e is shown in FIG. Try to vibrate like this. However, since the piezoelectric sheet (3) 40c integrated therewith is not displaced, the entire vibrator is subjected to the surface deflection vibration shown in FIG. 5B.

  In an actual driving method, the B1 phase and the B2 phase are driven in opposite phases. The reason why the B1 phase and the B2 phase are used as the B phase is to improve the symmetry of the entire vibrator. Hereinafter, the B1 phase and the B2 phase are referred to as the B phase under the condition of driving in the opposite phase.

  As described above, by driving the A phase and the B phase with a predetermined phase difference, elliptical vibration can be excited on the upper surface of the vibrator.

Since respect to the ultrasonic motor driving method using the present vibrator 11 ₁ is the same as in the first embodiment described above, description thereof is omitted.

  Thus, according to the second embodiment, in addition to the effects of the first embodiment described above, the following effects can be obtained.

  That is, since the contour sliding vibration and the surface deflection vibration can be excited independently, the magnitude and phase of both vibrations can be freely changed, and as a result, a highly flexible elliptical vibration can be formed.

  In the second embodiment, the vibration detecting element is not provided, but it can be configured in the same way as the first embodiment described above. Also, the driving method in that case can be realized by the same method as in the first embodiment.

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

  FIGS. 17A and 17B show a configuration of a vibrator according to the third embodiment of the present invention. FIG. 17A is an external perspective view of the front surface side, and FIG. 17B is a plan view viewed from the back surface side.

  Note that the third embodiment differs from the first and second embodiments described above only in the configuration of the vibrator. Therefore, here, the configuration of the vibrator will be described, and the basic configuration and operation of the other ultrasonic motor are the same as those in the first and second embodiments described above. The same parts are denoted by the same reference numerals, and illustration and detailed description thereof are omitted.

  Also in this embodiment, the outer diameter dimensions (a: b: c) of the vibrator are the same as those in the first and second embodiments described above.

  The vibrator of the third embodiment is different from the first embodiment described above in that it does not have a laminated structure.

In FIG. 17A, a cross finger electrode 46 for driving and a cross finger electrode 47 for detecting vibration are separately provided on the surface of the vibrator. The inclination of the interdigital electrodes 46 and 47 is 45 degrees. The driving cross finger electrode 46 is connected to A phase electrical terminals 49a ₁ and 49a ₂ of A + phase and A− phase. External lead wires and the like are connected by these electric terminals 49a ₁ and 49a ₂ . The vibration detecting cross finger electrode 47 is connected to C-phase and C-phase C-phase electrical terminals 50c ₁ and 50c ₂ .

As shown in FIG. 17B, a driving cross finger electrode 46 and a vibration detecting cross finger electrode 47 are similarly provided on the back surface. The inclination of the cross finger electrode is 45 degrees, and the direction of the cross finger electrode is the same as the direction of the cross finger electrode on the surface. The driving cross finger electrode 46 is connected to B-phase and B-phase B-phase electrical terminals 50d ₁ and 50d ₂ . The vibration detecting cross-finger electrode 47 is connected to D-phase and D-phase electrical terminals.

  Since the configuration of the ultrasonic motor using this vibrator is the same as that of the first and second embodiments described above, the description thereof is omitted.

  Next, the operation of the piezoelectric element configured as described above will be described.

  Regarding the operation, the first and second embodiments described above have a laminated structure, but the third embodiment has only a single plate structure, and the other configurations are the first and second embodiments described above. Since it is the same as that of 2nd Embodiment, description is abbreviate | omitted. The same applies to the frequency feedback control using the signal of the vibration detection electrode, and a description thereof will be omitted.

  As described above, according to the third embodiment, the vibrator according to the present embodiment cannot be driven at a low voltage, but the structure becomes very simple and the mass productivity is high.

  In the third embodiment, the driving cross-finger electrode and the vibration detecting cross-finger electrode are divided and printed on the same plane. However, the same printed on the piezoelectric sheet is used. Alternatively, a vibrator having a laminated structure as in the first embodiment may be used.

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

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

  According to the present invention, there is no need for a groove portion, there is no need to provide a hole in the piezoelectric element, elliptic vibration can be easily excited with a simple structure, and the rotor is rotated by elliptic vibration generated in the ultrasonic vibrator. An ultrasonic motor to be obtained is obtained.

DESCRIPTION OF SYMBOLS 10 ... Ultrasonic motor 11, 11 ₁ ... Laminated piezoelectric element (vibrator), 12a, 12b ... Friction contact, 13a, 13b, 13c, 13d ... External electrode, 15 ... Rotor, 16 ... Bearing, 17 ... Spring, DESCRIPTION OF SYMBOLS 18 ... Spring holding ring, 20 ... Vibrator holder, 21 ... Shaft fixing ring, 22 ... Shaft, 25 ... Piezoelectric sheet, 25a ... Piezoelectric sheet 1 (piezoelectric sheet (1)), 25b ... Piezoelectric sheet 2 (piezoelectric sheet (2) )), 25c ... piezoelectric sheet 3 (piezoelectric sheet (3)), 25d ... piezoelectric sheet 4 (piezoelectric sheet (4)), 25e ... piezoelectric sheet 5 (piezoelectric sheet (5)), 26 ... internal electrodes (intersecting finger electrodes) ), 27a, 27b, 27c, 27d ... extending electrodes, 30a, 30b, 30c, 30d, 31a, 31b, 31c, 31d ... nodal lines, 32 ... cross section at the center, 33a, 33b, 33 , 33d ... knurl, 35 ... center plane, 111 ... front half region 112 ... rear half region.

Claims (16)

A substantially rectangular parallelepiped vibrator whose section perpendicular to the central axis has a rectangular length ratio, and a central axis perpendicular to the elliptical vibration generating surface of the vibrator in contact with the elliptical vibration generating surface of the vibrator is rotated. An ultrasonic motor comprising at least a driven body that is rotationally driven as an axis,
The vibrator simultaneously excites a contour slip vibration and a surface deflection vibration generated on the same surface of the vibrator with a predetermined phase difference, and forms a surface orthogonal to the surface on which the contour slip vibration and the surface deflection vibration are generated. An ultrasonic motor characterized in that the driven body is rotationally driven in contact with a portion where the generated elliptical vibration is generated.   It further comprises a holding member that holds the vibrator at a position substantially at the center of the side surface orthogonal to the surface where the contour sliding vibration and the surface flexural vibration are generated. The ultrasonic motor according to claim 1.   The ultrasonic motor according to claim 2, wherein a ratio of each side of the substantially rectangular parallelepiped shape is approximately 1: 1: 0.45.   The ultrasonic motor according to claim 3, wherein a cross-sectional shape of the vibrator perpendicular to the rotation axis direction is a substantially rectangular shape.   3. The ultrasonic motor according to claim 1, wherein the driven body is a rotating body and contacts the vibrator at at least two locations in a plane where the elliptical vibration is generated.   5. The ultrasonic wave according to claim 4, wherein the vibrator is configured by a laminated piezoelectric element in which piezoelectric sheets are laminated in a direction orthogonal to a surface where the contour sliding vibration and the surface deflection vibration are generated. motor.   The ultrasonic motor according to claim 6, wherein the laminated piezoelectric element is formed by laminating a plurality of piezoelectric sheets on which cross finger electrodes whose arrangement direction is inclined by approximately 45 degrees are printed.   The ultrasonic motor according to claim 7, wherein the piezoelectric sheet on which the interdigitated electrodes are printed functions for generating vibration.   9. The ultrasonic motor according to claim 8, wherein the extending portion of the cross finger electrode on the vibration generating piezoelectric sheet to the end of the piezoelectric sheet is different from the central plane in the stacking direction.   The ultrasonic motor according to claim 7, wherein a part of the piezoelectric sheet on which the interdigitated electrodes are printed functions for vibration generation, and another part of the piezoelectric sheet functions for vibration detection.   The vibration generating piezoelectric sheet has a different extension site to the end of the piezoelectric sheet, and the piezoelectric sheet of the crossing finger electrode of the vibration detecting piezoelectric sheet with the central plane in the stacking direction as a boundary. The ultrasonic motor according to claim 10, wherein portions extending to the end portions are different.   The superposition detection piezoelectric sheet on which the cross finger electrode is printed is laminated so as to sandwich the vibration generation piezoelectric sheet on which the cross finger electrode is printed. Sonic motor.   12. The ultrasonic motor according to claim 11, wherein a driving piezoelectric sheet printed with the cross finger electrode is laminated so as to sandwich the vibration detecting piezoelectric sheet printed with the cross finger electrode. .   The laminated piezoelectric element is printed with a piezoelectric sheet printed with a cross finger electrode disposed at an inclination of approximately 45 degrees for exciting the contour sliding vibration and a substantially full surface electrode for exciting the surface flexural vibration. The ultrasonic motor according to claim 6, wherein piezoelectric sheets are laminated.   The vibrator is a single-plate vibrator, and crossed finger electrodes are printed on both surfaces of the contour sliding vibration and the surface bending vibration that are inclined at approximately 45 degrees in the same direction. The ultrasonic motor according to claim 5.   The ultrasonic motor according to claim 15, wherein a part of the cross finger electrode functions as a drive cross finger electrode, and another part of the cross finger electrode functions as a vibration detection cross finger electrode.

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