JP2009268242A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor efficiently driven at an optimum frequency without remarkably changing motor characteristics even if an environmental temperature change or a load temperature change occurs. <P>SOLUTION: The ultrasonic motor 10 is provided with an electrode for driving and an electrode for vibration detection. At least the electrode for vibration detection includes: an annular laminated piezoelectric element 20 divided into two portions to be line-symmetric with respect to a line-symmetric axis which is a center line in a plane of the piezoelectric element; an upper elastic body 30 in which a lower face 31 in contact with the laminated piezoelectric element 20 is diagonally cut; a lower elastic body 40 in which a face 42 in contact with the laminated piezoelectric element is diagonally cut; a rotor 52 driven in contact with a part of the upper elastic body 30; and a shaft 58 penetrating through the rotor 52, the upper elastic body 30, the laminated piezoelectric element 20 and the lower elastic body 40. <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, when there is a change in the environmental temperature or a change in the load temperature, the resonance frequency (longitudinal vibration resonance frequency or torsional vibration resonance frequency) generally changes. The ultrasonic motor described in Patent Document 1 described above does not have a means for detecting the longitudinal vibration resonance frequency or the torsional vibration resonance frequency. Therefore, if there is a change in environmental temperature or a change in load, the motor characteristics Has changed significantly and has a problem that it cannot be driven efficiently.

  Therefore, the present invention has been made in view of the above-described problems, and the object thereof is to drive efficiently at an optimal frequency without causing a significant change in motor characteristics even when there are environmental temperature changes or load changes. It is an object to provide an ultrasonic motor capable of performing the above.

  In other words, the present invention has a drive electrode and a vibration detection electrode, and at least the vibration detection electrode 2 is line-symmetrical with respect to a line symmetry axis serving as a center line existing in the plane of the piezoelectric element. The divided annular piezoelectric element and the other surface having one surface in a direction orthogonal to the central axis of the divided piezoelectric element and contacting the first surface of the piezoelectric element with a predetermined angle with the one surface A first columnar elastic body having one surface in a direction perpendicular to the center axis of the first columnar elastic body, and the other surface in contact with the second surface of the piezoelectric element at a predetermined angle with the one surface A second columnar elastic body, and a rotor driven in contact with a part of the first columnar elastic body.

  The present invention also includes an annular piezoelectric element having a driving electrode and a vibration detecting electrode, which is divided into two so as to be line symmetric with respect to a line symmetry axis serving as a center line existing in the plane of the piezoelectric element. The first columnar elastic body having one surface in a direction orthogonal to its central axis and having the other surface in contact with the first surface of the piezoelectric element at a predetermined angle with the one surface And a second columnar elastic body having one surface in a direction orthogonal to its central axis and having the other surface in contact with the second surface of the piezoelectric element at a predetermined angle with the one surface And a rotor driven in contact with a part of the first columnar elastic body, and the piezoelectric element is divided into two parts and has first and second vibration detections having negative polarity. A first sheet provided with an electrode, and first and second vibration detection electrodes divided into two and having positive polarity. Sheet, a third sheet having the first driving electrode among the driving electrodes, and a fourth sheet having the second driving electrode among the driving electrodes. It is characterized by comprising a drive electrode sheet in which a plurality of third sheets and fourth sheets are alternately laminated.

  According to the present invention, it is possible to provide an ultrasonic motor that can be efficiently driven at an optimum frequency without significantly changing motor characteristics even when there is a change in environmental temperature or load.

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

(First embodiment)
1A and 1B show an ultrasonic motor according to a first embodiment of the present invention, in which FIG. 1A is an external view and FIG. 1B is a cross-sectional view.

  The ultrasonic motor 10 includes a laminated piezoelectric element 20, an upper elastic body 30 that is a first elastic body sandwiching the laminated piezoelectric element 20, a lower elastic body 40 that is a second elastic body, and an upper elastic body 30. Friction contact 51 joined to the end, rotor 52 driven in contact with friction contact 51, bearing 53, pressing member 55, spring 56, nut 57, laminated piezoelectric element 20, upper elastic body 30 and a shaft 58 inserted into the hollow portion of the lower elastic body 40.

  The upper elastic body 30 is made of a metal material made of hollow cylindrical brass or aluminum, and its lower surface 31 is cut obliquely with respect to a plane orthogonal to its central axis as shown in the figure. ing. A female screw 32 is formed in the hollow interior so as to be screwed with a male screw 44 of the lower elastic body 40 described later.

  The lower elastic body 40 has a cylindrical shape and is formed of a metal material having a convex portion 41 at the center. And the convex part 41 is formed and the surface 42 on which the laminated piezoelectric element 20 is placed is cut obliquely so as to face the lower surface 31 of the upper elastic body 30 as will be described later. Further, a groove 43 is formed on the outer peripheral surface of the lower elastic body 40. On the upper outer peripheral surface of the convex portion 41 of the lower elastic body 40, a male screw 44 is formed for screwing with the female screw 32 of the upper elastic body 30 described above. Furthermore, a female screw 45 is formed at a predetermined position inside the hollow of the lower elastic body 40, that is, at a position corresponding to a node of longitudinal vibration of the vibrator.

  A male screw 59 for screwing with the female screw 45 of the lower elastic body 40 is formed at a substantially central portion of the shaft 58, and a female screw 60 is also formed at the upper end portion. The friction contact 51 is made of an engineering plastic such as an annular PPS, and is provided between the upper elastic body 30 and the rotor 52. The rotor 52 is composed of hollow alumina ceramics, and an annular bearing 53 is inserted into the hollow.

  Next, an assembly procedure of the ultrasonic motor 10 will be described.

  First, the laminated piezoelectric element 20 is installed between the upper elastic body 30 and the lower elastic body 40. At that time, the upper elastic body 30 and the laminated piezoelectric element 20 are fitted with the convex portions 41 of the lower elastic body 40 from below. Then, the male screw 44 of the convex portion 41 and the female screw 32 of the hollow portion of the upper elastic body 30 are screwed together. Next, the annular frictional contact 51 is bonded to the upper surface of the upper elastic body 30 using an adhesive. Thereafter, the shaft 58 is inserted from above the upper elastic body 30, and the male screw 59 at the substantially central portion of the shaft 58 and the female screw 45 of the lower elastic body 40 are screwed together.

  The component constituted so far is referred to as a vibrator of the ultrasonic motor 10 or an ultrasonic vibrator in the present embodiment. Although details will be described later, the position of the female screw 45 of the lower elastic body 40 is provided at a position that is substantially the node position of the resonance longitudinal vibration mode of the vibrator.

  Thereafter, the rotor 52 into which the bearing 53 is inserted, the pressing member 55 that presses the inner peripheral portion of the bearing 53 downward, the spring 56, and the nut 57 are inserted in this order from above the shaft 58. Thus, the position of the nut 57 is adjusted according to the state of the shaft 58 with the female screw 60 so that the pressing force of the rotor 52 to the frictional contact 51 becomes appropriate.

  Next, details of the laminated piezoelectric element 20 used in the present embodiment will be described with reference to FIGS.

  2 is an external view of the laminated piezoelectric element 20, FIG. 3 is a view of the laminated piezoelectric element 20 of FIG. 2 as viewed from above, and FIG. 4 is a view showing the structure of the internal electrodes of the laminated piezoelectric element 20.

  This laminated piezoelectric element is configured by laminating a plurality of piezoelectric sheets.

First, referring to FIG. 4, will be described piezoelectric sheets 125 ₁ the lowermost surface of the laminated piezoelectric element 20.

  The material of the piezoelectric sheet is, for example, a lead zirconate titanate piezoelectric ceramic element (hereinafter referred to as PZT) having a thickness of about 100 μm. As PZT, a hard material having a large Qm value is selected. The Qm value is about 1800.

On _one side (here, the front surface) side of the annular piezoelectric sheet 125 ₁ , as shown in FIG. 4, one side is divided into two with respect to the line symmetry axis O which is the center line of the piezoelectric sheet 125 ₁ (internal electrode A−). 201a, internal electrode C-201c), and the opposite side divided into two (internal electrode B-201b, internal electrode D-201d). As shown in FIG. 4, a region having no internal electrode is provided from the end, for example, about 0.3 mm. However, a part of each electrode region is drawn out to the end of the piezoelectric sheet and is provided with electrode lead-out portions 201a ₁ , 201b ₁ , 201c ₁ , 201d _{1 in} order to electrically connect with external electrodes to be described later. . The material of the internal electrode is, for example, a silver palladium alloy having a thickness of about 4 μm. Each electrode has a predetermined interval so as to maintain insulation.

Next, the piezoelectric sheet 225 ₂ that is one upper than the lowermost piezoelectric sheet 125 ₁ in the laminated piezoelectric element 20 will be described.

Like the piezoelectric sheets 125 _1, the annular piezoelectric sheet one side is (the surface side), as shown in FIG. 4, with respect to the line symmetry axis O, one bisected (internal electrodes A + 202a, the internal electrode C + 202c) , opposite bisected (internal electrodes B + 202b, the internal electrodes D + 202d) of the point where total four divided internal electrodes are provided on the piezoelectric sheet 225 _{and second} surface, which is similar to the piezoelectric sheet 125 _1. That is, the internal electrode A + 202a is formed on the internal electrode A-201a, the internal electrode B + 202b is formed on the internal electrode B-201b, the internal electrode C + 202c is formed on the internal electrode C-201c, and the internal electrode D + 202d is formed on the internal electrode D-201d. , Respectively. However, only the positions where the electrode lead-out portions 201a ₂ , 201b ₂ , 201c ₂ , 201d ₂ for contacting the external electrodes are different from the piezoelectric sheet 125 ₁ .

The piezoelectric sheets from below, the piezoelectric sheets 125 _1, the piezoelectric sheets 225 _2, the piezoelectric sheets 125 _1, the piezoelectric sheets 225 _2, ..., the piezoelectric sheets 125 _1, are stacked in this order piezoelectric sheets 225 _2, the last of the piezoelectric sheets 225 ₂ An insulating sheet 26 is overlaid thereon. The insulating sheet 26 is made of a piezoelectric material on which internal electrodes are not printed.

  The laminated piezoelectric element 20 thus laminated is sintered at a high temperature after pressing.

Thereafter, as shown in FIG. 2, the internal electrodes A + 202a of external electrodes A + 21a at a position in contact with the electrode lead-out portion 202a _2, the internal electrodes A-201a of the electrode lead portion 201a ₁ and the external electrodes A-21b to a position in contact, internal electrode C + 202c of the electrode lead-out portion 202c ₂ and the contact to the external electrode C + 23a in position, the external electrode C-23b is provided at a position in contact with the electrode lead-out portion 201c ₁ of the internal electrodes C-201c. Similarly, the opposite side of these external electrodes, as shown in FIG. 3, the external electrodes B + 22a at a position in contact with the electrode lead portion 202b ₂ of the internal electrode B + 202b, and the electrode lead portion 201b ₁ of the internal electrode B-201b external electrodes B-22b to a position in contact, the external electrodes D + 24a at a position in contact with the electrode lead-out portion 202d ₂ of the internal electrodes D + 202d, the external electrodes D-24b to a position in contact with the electrode lead-out portion 201d ₁ of the internal electrodes D-201d Provided.

Finally, a high voltage is applied between the + and − poles of each electrode to polarize the piezoelectric element and activate it piezoelectrically. Note that the upper and lower surfaces in contact with the elastic body are wrapped to a state close to a mirror surface.
The external electrodes A + 21a and A-21b, the external electrodes B + 22a and B-22b are driving electrodes for motor driving, the external electrodes C + 23a and C-23b, and the external electrodes D + 24a and D-24b are detection electrodes for vibration detection. To do.

  In the first embodiment, the drive electrode is disposed above the obliquely cut surface 42 of the lower elastic body 40 and the detection electrode is disposed below.

  Next, the operation of the vibrator of the ultrasonic motor 10 in the first embodiment will be described with reference to FIG.

  When the laminated piezoelectric element 20 extends, a force F is applied to the upper elastic body 30 and a force G is applied to the lower elastic body 40 as shown in FIG. Then, considering the component of each force, F1 and G1 are forces that generate torsional vibration, and F2 and G2 are forces that generate longitudinal vibration.

  It can be seen that when the laminated piezoelectric element 20 is contracted, the direction of the vector is reversed, but the force for generating the above-described longitudinal vibration and torsional vibration is also generated. When an alternating voltage having the same phase is applied to the external electrode A (A +, A−) and the external electrode B (B +, B−), only the resonance longitudinal vibration mode is excited as shown in FIG.

  Further, when an alternating voltage having an opposite phase (phase difference π) is applied to the external electrode A (A +, A−) and the external electrode B (B +, B−), the upper elastic body as shown in FIG. Only the resonant torsional vibration mode in which 30 and the lower elastic body 40 rotate in opposite directions is excited.

  Note that by changing the length dimension of the lower elastic body 40 below the groove portion 43 (opposite to the laminated piezoelectric element 20) and setting the relative position of the groove portion 43 to an appropriate position, the resonance longitudinal vibration mode and the resonance torsional vibration are obtained. Are substantially matched.

  As the rotor 52 is pressed, both the longitudinal resonance frequency and the torsional resonance frequency increase. Here, since the rate of change in which the resonance frequency of the resonance longitudinal vibration mode increases is larger, the resonance frequency of the resonance longitudinal vibration mode is slightly lower than the resonance frequency of the resonance torsional vibration mode in a single vibrator that does not press the rotor. deep.

  Now, the phase A (external electrode A (A +, A−)) and phase B (external electrode B (B +, B−)) are applied with a phase difference other than in-phase and anti-phase, for example, ± π / 2. Then, both the resonant longitudinal vibration mode and the resonant torsional vibration mode are excited. Then, as shown in FIG. 5D, an elliptical motion of CW or CCW can be generated in the vicinity of the frictional contact 51 on the upper surface of the vibrator.

  Next, signals obtained from the vibration detection phase C phase (external electrode C (C +, C−)) and the vibration detection phase D phase (external electrode D (D +, D−)) will be described.

  When an alternating voltage having a longitudinal vibration resonance frequency of the same phase is applied to the A phase and the B phase, the C phase and the D phase are connected in parallel in order (the external electrodes C + and D + are connected, and the external electrodes C− and D− are connected). Is defined as a parallel forward connection phase), a signal proportional to the longitudinal vibration is obtained. Further, when the C phase and the D phase are reversely connected in parallel (the external electrodes C + and D− are connected and the external electrodes C− and D + are connected: defined as a parallel reverse connection phase), no signal is output.

  On the other hand, when an alternating voltage having a torsional vibration resonance frequency of opposite phase is applied to the A phase and the B phase, no signal is output from the parallel forward connection phase in which the C phase and the D phase are connected in parallel. However, a signal proportional to torsional vibration is obtained from the parallel reverse connection phase in which the C phase and the D phase are reversely connected in parallel.

  Next, the operation of the ultrasonic motor 10 in this embodiment will be described.

  In the ultrasonic motor 10 shown in FIG. 1, alternating voltages having different phases are applied to the A phase and the B phase, and elliptical vibration is generated at the position of the frictional contact 51 of the vibrator. Then, the rotor 52 rotates in the CW or CCW direction. Here, a signal proportional to the torsional vibration is generated from the parallel reverse connection phase relating to the C phase and the D phase. Therefore, the drive frequency is always fed back so that the magnitude of the signal is maximized, and the drive frequency is driven at an optimum frequency that maximizes the torsional vibration.

  As described above, in the first embodiment, since the vibration detection region is provided in the multilayer piezoelectric element so that only the torsional vibration can be detected, the motor can be driven at a frequency at which the torsional vibration is always maximized. As a result, the motor can always be driven stably even if there are ambient environmental temperatures and load fluctuations applied to the motor.

  In the first embodiment, the signal of the parallel reverse connection phase is extracted with respect to the C phase and the D phase. However, the signal of the parallel forward connection phase is extracted and driven so that the magnitude of the signal is maximized. The frequency may be adjusted.

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

  FIG. 6 is a cross-sectional view of an ultrasonic motor 10a according to a first modification of the first embodiment of the present invention.

  In the first to fifth modifications described below, the basic configuration and operation of the ultrasonic motor are the same as those in the first embodiment described above. The same reference numerals are assigned to the same parts, illustration and detailed description thereof are omitted, and only different parts will be described.

  In the first modification, the lower elastic body 40 of the ultrasonic motor 10a is composed of a first lower elastic body 65 and a second lower elastic body 71, which is different from the first embodiment described above. ing.

  In FIG. 6, the first lower elastic body 65 has a hollow cylindrical shape, and the surface 66 on which the laminated piezoelectric element 20 is placed is cut obliquely so as to face the lower surface 31 of the upper elastic body 30. Further, the second lower elastic body 71 is formed of a metal material having a hollow cylindrical shape and a central portion on which a convex portion 75 is formed. A groove portion 72 is formed on the outer peripheral surface of the portion in contact with the first lower elastic body 65.

  Further, a male screw 74 is formed on the upper outer peripheral surface of the convex portion 75 of the second lower elastic body 71 to be screwed with the female screw 32 of the upper elastic body 30. Furthermore, a female screw 66 is formed at a predetermined position inside the hollow of the second lower elastic body 71, that is, at a position corresponding to a node of longitudinal vibration of the vibrator.

  In the assembling procedure of the ultrasonic motor 10a, the laminated piezoelectric element 20 is first installed between the upper elastic body 30 and the first lower elastic body 65. And the convex part 73 of the 2nd lower elastic body 71 is inserted from the hollow part of the 1st lower elastic body 65, and the external thread 44 of the convex part 75 and the internal thread 32 of the hollow part of the upper elastic body 30 are screwed together. . The subsequent steps are the same as in the first embodiment described above.

  In addition, by changing the length dimension of the maximum diameter portion of the second lower elastic body 71 and setting the relative position of the groove 72 to an appropriate position, the resonant longitudinal vibration mode and the resonant frequency of the resonant torsional vibration are substantially matched. Can do.

  Also according to the first modification, the same operation and effect as those of the first embodiment described above can be exhibited.

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

  FIG. 7 shows a second modification of the first embodiment and is a diagram showing the structure of the internal electrodes of the laminated piezoelectric element.

  The second modification is different from the first embodiment described above in that the vibration detection electrode is provided on the upper side of the drive electrode on one side of the line symmetry axis O.

  That is, the detection electrode is arranged on the upper side of the obliquely cut surface 42 of the lower elastic body 40 and the drive electrode is arranged on the lower side.

On _one side (here, the front surface) side of the annular piezoelectric sheet 1811, as shown in FIG. 7, one of the internal electrode C-205 c and the internal electrode A-205 a is inserted from the upper side with the line symmetry axis O in between. However, on the other side, an internal electrode D-205d and an internal electrode B-205b are respectively arranged from the upper side. Further, the one surface side of the piezoelectric sheet 281 ₂ placed on top of the piezoelectric sheet 1811, across the line symmetry axis O, one of the internal electrodes from an upper C + 206c, the internal electrodes A + 206a, the other, from the upper side An internal electrode D + 206d and an internal electrode B + 206b are respectively arranged.

The internal electrodes A-205a, B-205b, C-205c, D-205d, A + 206a, B + 206b, C + 206c, and D + 206d have electrode lead-out portions 205a ₁ and 205b ₁ that are electrically connected to external electrodes. , 205c ₁ , 205d ₁ , 206a ₁ , 206b ₁ , 206c ₁ , 206d ₁ are provided.

  Also according to the second modification, the same operation and effect as those of the first embodiment described above can be exhibited.

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

  FIG. 8 shows a third modification of the first embodiment, and is a cross-sectional view of the ultrasonic motor 10b.

  In the first modified example described above, the lower elastic body is divided into two, but in the third modified example, the first lower elastic body and the upper elastic body are further divided into two elastic bodies, respectively.

  That is, the upper elastic body is disposed on the friction contact 51 side and has a first upper elastic body 30a having a surface cut on both sides perpendicular to the outer peripheral surface, and the first upper elastic body 30a and the laminated piezoelectric element. 20 and the second upper elastic body 35 disposed between them. Similarly, the first lower elastic body is composed of a first lower elastic body 65a adjacent to the second lower elastic body 71 and a third lower elastic body disposed between the first lower elastic body 65a and the laminated piezoelectric element 20. The body 68 is configured.

  As a procedure for assembling such an ultrasonic motor 10b, the laminated piezoelectric element 20 is previously sandwiched between the second upper elastic body 35 and the third lower elastic body, and the first upper elastic body 30a and the second lower elastic body 71 are sandwiched between them. You may make it pinch | interpose.

  According to the third modification, the same operation and effect as those of the first embodiment described above can be exhibited, and the final assembly of the motor is facilitated.

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

  FIG. 9 shows a fourth modification of the first embodiment and is a diagram showing the structure of the internal electrodes of the laminated piezoelectric element.

  This fourth modification differs from the first embodiment described above in that internal electrodes are provided on both the front surface side and the back surface side of one piezoelectric element.

That is, as shown in FIG. 9A, on the surface side of the piezoelectric element 83, one side is divided into two with respect to the line symmetry axis O (internal electrode A + 210a, internal electrode C + 210c), and opposite side is divided into two (internal). An internal electrode divided into four parts, that is, an electrode B + 210b and an internal electrode D + 210d) is provided. Also, these internal electrodes A + 210a, B + 210b, C + 210c, the D + 210d, while the electrode lead-out portion 210a _2, 210 b ₂ for conducting an external electrode electrically not shown, 210c _2, 210d ₂ are provided, FIG. 9B, on the back side of the piezoelectric element 83, one side is divided into two with respect to the line symmetry axis O (internal electrode A-209a, internal electrode C-209c), and opposite side is divided into two. Internal electrodes (internal electrode B-209b, internal electrode D-209d) divided into four as a whole are provided. And these internal electrodes A-209a, B-209b, C-209c, the D-209d, the electrode lead portions _{209a 1, 209b 1, 209c 1} , 209d 1 is provided.

  In this way, a single-plate piezoelectric element may be used instead of the laminated piezoelectric element. In this case, the driving voltage is increased, but there is an advantage that the configuration is simplified. In the case of the fourth modified example, since there are electrodes on both the front surface side and the back surface side of the piezoelectric element, an annular insulating member is interposed between the upper elastic body and the lower elastic body. Need to be inserted into.

  Also according to the fourth modification, the same operation and effect as those of the first embodiment described above can be exhibited.

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

  FIG. 10 shows a fifth modification of the first embodiment and is a diagram showing the structure of the internal electrodes of the multilayer piezoelectric element.

  In this fifth modification, in this case, the detection electrodes C and D are arranged symmetrically with respect to the axis of line symmetry O, but the point set at the substantially central portion of the half region on one side is the above-mentioned first modification. This is different from the first embodiment.

  That is, the drive electrodes are arranged on the upper and lower sides of the obliquely cut surface 42 of the lower elastic body 40, and the detection electrodes are arranged therebetween.

As shown in FIG. 10, on one side (here, the front surface) side of the annular piezoelectric sheet 184 ₁ , with the line symmetry axis O interposed therebetween, one is the internal electrode A-213a and the internal electrode C-213c from above. The internal electrode A-223a is arranged on the other side, and the B-213b, the internal electrode D-213d, and the internal electrode B-223b are arranged on the other side from the upper side. Also, this piezoelectric sheet 184
1 on one side of the piezoelectric sheet 284 ₂ placed on 1 with the line symmetry axis O in between, one from the top is the internal electrode A + 214a, the internal electrode C + 214c, the internal electrode A + 224a, and the other is from the top to the inside Electrode B + 214a, internal electrode D + 214d, and internal electrode B + 224b are each arrange | positioned.

In each internal electrode, electrode lead-out portions 213a ₁ , 213b ₁ , 213c ₁ , 213d ₁ , 223a ₁ , 223b ₁ , 214a ₁ , 214b ₁ , 214c ₁ , 214d for electrically conducting with the external electrode are provided. ₁ , 224a ₁ , and 224b ₁ are provided. In this case, the resultant force vector of the internal electrode A on the upper side and the internal electrode A on the lower side of the force generated from the drive electrode is Since it comes almost to the center, the driving force can be efficiently transmitted to the elastic body. Therefore, according to the fifth modification, the same operation and effect as those of the first embodiment described above can be exhibited, and longitudinal vibration and torsional vibration can be efficiently generated.

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

  In the first embodiment described above, two types of detection electrodes are provided for detecting longitudinal vibration and for detecting torsional vibration, whereas in this second embodiment, only one type of detection electrode for detecting longitudinal vibration is provided. It has become.

  In the second embodiment, the basic configuration and operation of the ultrasonic motor are the same as those of the first embodiment described above, and only the configuration of the laminated piezoelectric element is different. In order to avoid duplication, the same reference numerals are assigned to the same parts, illustration and detailed description thereof are omitted, and only different parts will be described.

  FIG. 11 shows the structure of the internal electrode of the multilayer piezoelectric element according to the second embodiment of the present invention.

  In FIG. 11, one drive electrode is provided symmetrically with respect to the line symmetry axis O on one side (front side) of the annular piezoelectric sheet, and the detection electrode is provided with respect to the line symmetry axis O. One is provided symmetrically.

That is, the surface side of the piezoelectric sheet 186 ₁ of annular, across the line symmetry axis O, internal electrodes A-217a on the upper side, the internal electrode B-217b is, and the internal electrodes C-217c between the two electrodes, Each is arranged. _On the surface side of the piezoelectric sheet 286 ₂ placed on the piezoelectric sheet 186 ₁ , the internal electrode A + 218a and the internal electrode B + 218b are disposed on the upper side with the line symmetry axis O in between, and the internal electrode C + 218c is interposed between the two electrodes. Are arranged.

As described above, the piezoelectric sheets 186 ₁ and 286 ₂ have the same configuration, but the electrode lead-out portions 217a ₁ and 218a ₁ , 217b ₁ and 218b ₂ , and 217c ₁ for electrically connecting to the external electrodes are used. The positions where 218c ₂ are provided are different. A plurality of such piezoelectric sheets 186 ₁ and 286 ₂ are alternately stacked, and finally an insulating sheet on which an internal electrode made of a piezoelectric element is not printed is stacked.

  Since the assembly procedure of the multilayer piezoelectric element is the same as that of the first embodiment described above, description thereof is omitted.

Further, the external electrodes are not shown, but the electrode lead-out portions 217a ₁ , 218a ₁ , 217b ₁ , 218b ₂ , 217c ₁ , 218c of the internal electrodes A-217a, A + 218a, B-217b, B + 218b, C-217c, C + 218c Corresponding to _2, it is provided at six locations.

  In the multilayer piezoelectric element configured as described above, a signal proportional to longitudinal vibration is output from the detection electrode C for vibration detection. Therefore, the drive frequency is controlled so that the magnitude of this signal is always maximized.

  Since the other operations of the multilayer piezoelectric element and the operation of the ultrasonic motor are the same as those in the first embodiment described above, the description thereof is omitted.

  As described above, according to the second embodiment, the number of divisions of the internal electrodes is reduced and the number of external electrodes is also reduced, so that the configuration is simplified.

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

  In the first and second embodiments described above, both the drive electrode and the detection electrode are arranged as internal electrodes on the same piezoelectric element (piezoelectric sheet). In the third embodiment, the drive electrode and The detection electrodes are arranged on separate piezoelectric elements (piezoelectric sheets).

  In the third embodiment, the basic configuration and operation of the ultrasonic motor are the same as those of the first embodiment described above, and only the configuration of the laminated piezoelectric element is different. In order to avoid duplication, the same reference numerals are assigned to the same parts, illustration and detailed description thereof are omitted, and only different parts will be described.

  Details of the laminated piezoelectric element 20 ′ used in the third embodiment will be described with reference to FIGS.

  12 is an external view of the laminated piezoelectric element 20 ′, FIG. 13 is a view of the laminated piezoelectric element 20 ′ of FIG. 12 as viewed from above, and FIG. 14 is a view showing the structure of the internal electrodes of the laminated piezoelectric element 20 ′.

  This laminated piezoelectric element is configured by laminating a plurality of piezoelectric sheets.

In FIG 14, the piezoelectric sheets 191 _single-sided for detecting electrodes annular (where the front side), across the line symmetry axis O, and is disposed internal electrodes C-231a and the internal electrode D-231b Yes. Then, the front surface side of the piezoelectric sheet 291 _{and second} detection electrodes which are placed on the piezoelectric sheets 191 ₁ across the line symmetry axis O, internal electrode C + 232a and the internal electrode D + 232b are arranged. Further, the positions where the electrode lead-out portions 231a ₁ and 232a ₂ and 231b ₁ and 232b ₂ for electrical connection with the external electrodes are provided are different.

A piezoelectric sheet 192 ₁ for driving electrodes is placed on the piezoelectric sheet 291 ₂ for detection electrodes. The piezoelectric sheet 192 _single-sided for annular drive electrodes (where the front side), across the line symmetry axis O, internal electrodes A-233a and the internal electrode B-233b are arranged. On the surface side of the piezoelectric sheet 292 _{and second} drive electrodes which are placed on the piezoelectric sheet 192 _1, across the line symmetry axis O, internal electrodes A + 234a and the internal electrode B + 234b are arranged.

Further, the positions where the electrode lead-out portions 233a ₁ and 234a ₂ , 233b ₁ and 234b ₂ for electrical conduction with the external electrodes are provided are different from each other. In addition, the electrode lead portion of the internal electrode electrode lead portion of the C-231a 231a ₁ and the internal electrodes A-233a 233a _1, the internal electrode C + 232b of the electrode lead portion 232a ₂ and the internal electrodes A + 234a of the electrode lead-out portion 234a _2, the internal electrodes D -231b electrode lead-out portion 231b ₁ and internal electrode B-233b electrode lead-out portion 233b ₁ , internal electrode D + 232b electrode lead-out portion 232b ₂ and internal electrode B + 234b electrode lead-out portion 234b ₂ are provided at the same position, respectively. .

In this way, after the piezoelectric sheets 191 ₁ and 291 ₂ for detection electrodes are laminated, a plurality of piezoelectric sheets 192 ₁ and 292 ₂ for driving electrodes are alternately laminated on the piezoelectric sheet 291 _2. The Finally, an insulating sheet 26 on which an internal electrode made of a piezoelectric element is not printed is laminated.

  Since the assembly procedure of the multilayer piezoelectric element is the same as that of the first embodiment described above, description thereof is omitted.

  As shown in FIG. 12, the external electrode conducting to the internal electrode drawn out in the same direction is divided into two to form the drive external electrode A + 21a and the vibration detection external electrode C + 23a. Similarly, the external electrode for driving A-21b and the external electrode for vibration detection C-23b are formed.

  Furthermore, as shown in FIG. 13, the external electrode B + 22a (D + 24a) and the external electrode B-22b (D-24b) are positioned opposite to the external electrode A + 21a (C + 23a) and the external electrode A-21b (C-23b). Is provided.

  The operations of the multilayer piezoelectric element 20 ′ and the ultrasonic motor configured as described above are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  As the ultrasonic motor becomes smaller, the laminated piezoelectric element inevitably needs to become smaller. In this case, since the shape of the piezoelectric sheet is also reduced, the four-divided configuration and the three-divided configuration as described in the first and the modified examples and the second embodiment described above cannot be performed, so the third embodiment The internal electrode divided into two is advantageous.

As described above, in the longitudinal torsion motor, only one laminated piezoelectric element is required, and the laminated piezoelectric element also has a function of detecting longitudinal vibration or torsional vibration. Even if the load on the motor fluctuates, the drive frequency can be controlled so as to optimize the vibration, so that stable motor drive is possible. In addition, since a laminated piezoelectric element is used, driving at a low voltage is possible.
In the first to third embodiments described above, the elastic body has a cylindrical shape. However, the elastic body is not limited to this and may have a prismatic shape. In addition, although the piezoelectric element or the laminated piezoelectric element has a cylindrical shape, it may have a prismatic shape.

  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.

The ultrasonic motor which concerns on the 1st Embodiment of this invention is shown, (a) is an external view, (b) is sectional drawing. The details of the multilayer piezoelectric element 20 used in the first embodiment of the present invention will be described, and are external views of the multilayer piezoelectric element 20. FIG. 3 is a diagram illustrating details of the multilayer piezoelectric element 20 used in the first embodiment of the present invention, and is a view of the multilayer piezoelectric element 20 of FIG. 2 as viewed from above. FIG. 2 is a diagram illustrating the details of the multilayer piezoelectric element 20 used in the first embodiment of the present invention, and is a diagram showing the structure of internal electrodes of the multilayer piezoelectric element 20. It is a figure for demonstrating operation | movement of the vibrator | oscillator of the ultrasonic motor 10 in the 1st Embodiment of this invention with reference to FIG. It is sectional drawing of the ultrasonic motor 10a by the 1st modification of the 1st Embodiment of this invention. FIG. 10 is a view showing a second modification of the first embodiment of the present invention and showing a structure of an internal electrode of a laminated piezoelectric element. The 3rd modification of the 1st Embodiment of this invention is shown, and is sectional drawing of the ultrasonic motor 10b. FIG. 10 is a view showing a fourth modification of the first embodiment of the present invention and showing a structure of an internal electrode of a multilayer piezoelectric element. FIG. 10 is a view showing a fifth modification of the first embodiment of the present invention and showing a structure of an internal electrode of a multilayer piezoelectric element. FIG. 7 is a diagram illustrating a structure of an internal electrode of a multilayer piezoelectric element according to a second embodiment of the present invention. The details of the laminated piezoelectric element 20 ′ used in the third embodiment of the present invention will be described, and are external views of the laminated piezoelectric element 20 ′. FIG. 13 is a diagram illustrating the laminated piezoelectric element 20 ′ used in the third embodiment of the present invention in detail, and is a view of the laminated piezoelectric element 20 ′ of FIG. 12 as viewed from above. The details of the laminated piezoelectric element 20 ′ used in the third embodiment of the present invention will be described, and are diagrams showing the structure of the internal electrodes of the laminated piezoelectric element 20 ′.

Explanation of symbols

10 ... ultrasonic motor 20, 20 '... laminated piezoelectric elements, 25 ₁ ... piezoelectric sheets 1,25 ₂ ... piezoelectric sheets 2,30 ... upper elastic member, 31 ... lower surface, 32,45,60 ... female screw, 40 ... lower Elastic body, 41 ... convex part, 42 ... surface, 43 ... groove part, 44, 59 ... male screw, 51 ... friction contact, 52 ... rotor, 53 ... bearing, 55 ... pressing member, 56 ... spring, 57 ... nut, 58 ... shaft, 201a ... internal electrode A-, 201b ... internal electrode B-, 201c ... internal electrodes C-, 201d ... internal electrode _{D-, 201a 1, 201a 2,} 201b 1, 201b 2, 201c 1, 201c 2, 201d ₁ , 201 d _2, electrode lead-out portion, 202 a, internal electrode A +, 202 b, internal electrode B +, 202 c, internal electrode C +, 202 d, internal electrode D +,

Claims (16)

A drive electrode and a vibration detection electrode, and at least the vibration detection electrode is an annular ring divided into two so as to be symmetric with respect to a line symmetry axis that is a center line existing in the plane of the piezoelectric element; A piezoelectric element;
A first columnar elastic body having one surface in a direction perpendicular to its central axis and having the other surface in contact with the first surface of the piezoelectric element at a predetermined angle with the one surface; ,
A second columnar elastic body having one surface in a direction orthogonal to its central axis and having the other surface in contact with the second surface of the piezoelectric element at a predetermined angle with the one surface;
A rotor driven in contact with a part of the first columnar elastic body;
An ultrasonic motor comprising:   2. The ultrasonic motor according to claim 1, wherein the piezoelectric element has a region divided into four in the entire surface, and two of the regions are vibration detection electrodes.   2. The ultrasonic motor according to claim 1, wherein the piezoelectric element has a region divided into three in the entire surface, and one of the regions is a vibration detection electrode.   2. The ultrasonic motor according to claim 1, wherein the piezoelectric element has a region divided into six in the entire surface, and two of the regions are vibration detection electrodes. The piezoelectric element includes first and second vibration detection electrodes, and each of the first and second vibration detection electrodes has a positive electrode and a negative electrode having different polarities,
A positive electrode of the first vibration detection electrode, a positive electrode of the second vibration detection electrode, a negative electrode of the first vibration detection electrode, and a negative electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 2, wherein a vibration detection signal is detected. The piezoelectric element includes first and second vibration detection electrodes, and each of the first and second vibration detection electrodes has a positive electrode and a negative electrode having different polarities,
A positive electrode of the first vibration detection electrode, a positive electrode of the second vibration detection electrode, a negative electrode of the first vibration detection electrode, and a negative electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 4, wherein a vibration detection signal is detected. The piezoelectric element includes first and second vibration detection electrodes, and each of the first and second vibration detection electrodes has a positive electrode and a negative electrode having different polarities,
A positive electrode of the first vibration detection electrode and a negative electrode of the second vibration detection electrode, and a negative electrode of the first vibration detection electrode and a positive electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 2, wherein a vibration detection signal is detected. The piezoelectric element includes first and second vibration detection electrodes, and each of the first and second vibration detection electrodes has a positive electrode and a negative electrode having different polarities,
A positive electrode of the first vibration detection electrode and a negative electrode of the second vibration detection electrode, and a negative electrode of the first vibration detection electrode and a positive electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 4, wherein a vibration detection signal is detected.   The ultrasonic motor according to claim 2, wherein the driving electrode is arranged so as to be line-symmetric with respect to a central axis existing in the plane thereof.   The ultrasonic motor according to claim 3, wherein the driving electrode is arranged so as to be line-symmetric with respect to a center existing in the plane.   The ultrasonic motor according to claim 4, wherein the driving electrode is arranged so as to be line-symmetric with respect to a central axis existing in the plane.   The ultrasonic motor according to claim 1, wherein the driving electrode is provided so as to be line-symmetric with respect to a central axis existing in a plane thereof.   13. The piezoelectric element according to claim 12, wherein the piezoelectric element is a laminated piezoelectric element in which an electrode portion including the driving electrode and a vibration detecting electrode and a piezoelectric sheet that insulates the electrode portion are alternately laminated. Ultrasonic motor. An annular piezoelectric element having a drive electrode and a vibration detection electrode, which is divided into two so as to be line symmetric with respect to a line symmetry axis which is a center line existing in the plane of the piezoelectric element;
A first columnar elastic body having one surface in a direction perpendicular to its central axis and having the other surface in contact with the first surface of the piezoelectric element at a predetermined angle with the one surface; ,
A second columnar elastic body having one surface in a direction orthogonal to its central axis and having the other surface in contact with the second surface of the piezoelectric element at a predetermined angle with the one surface;
A rotor driven in contact with a part of the first columnar elastic body;
Comprising
The piezoelectric element is
A first sheet provided with first and second vibration detection electrodes divided into two and having negative polarity;
A second sheet provided with first and second vibration detection electrodes divided into two and having positive polarity;
A third sheet having a first driving electrode among the driving electrodes, and a fourth sheet having a second driving electrode among the driving electrodes. A drive electrode sheet in which a plurality of sheets and fourth sheets are alternately laminated;
An ultrasonic motor comprising:   A positive electrode of the first vibration detection electrode, a positive electrode of the second vibration detection electrode, a negative electrode of the first vibration detection electrode, and a negative electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 14, wherein a vibration detection signal is detected.   A positive electrode of the first vibration detection electrode and a negative electrode of the second vibration detection electrode, and a negative electrode of the first vibration detection electrode and a positive electrode of the second vibration detection electrode are connected in parallel. The ultrasonic motor according to claim 14, wherein a vibration detection signal is detected.

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