WO2022220061A1

WO2022220061A1 - Ultrasonic motor

Info

Publication number: WO2022220061A1
Application number: PCT/JP2022/014304
Authority: WO
Inventors: 光城寺沢
Original assignee: 株式会社村田製作所
Priority date: 2021-04-13
Filing date: 2022-03-25
Publication date: 2022-10-20

Abstract

Provided is an ultrasonic motor with which rotational efficiency can be increased.　An ultrasonic motor according to the present invention is provided with: a stator 2 comprising a plate-shaped vibrating body 3 including a first main surface 3a and a second main surface 3b that oppose one another, and first to fourth piezoelectric elements 13A to 13D provided on the first main surface 3a of the vibrating body 3; and a rotor which is in contact with the second main surface 3b of the vibrating body 3. The vibrating body 3 vibrates in B (1, N) modes. A groove portion 5 is provided in at least one of the first main surface 3a and the second main surface 3b of the vibrating body 3. In a plan view of the first main surface 3a, the groove portion 5 has a circular shape, and is closer to a center of gravity G of the vibrating body 3 than the first to fourth piezoelectric elements 13A to 13D.

Description

ultrasonic motor

The present invention relates to ultrasonic motors.

Conventionally, various ultrasonic motors have been proposed that vibrate the stator using a piezoelectric element. Patent Document 1 below discloses an example of an ultrasonic motor in which a plurality of piezoelectric vibrators are arranged on a vibrating body in a stator. In this ultrasonic motor, the plurality of piezoelectric vibrators vibrate the vibrator in B(1, n) mode (n is a natural number). This produces a traveling wave in the stator. A rotor is in contact with the stator. The traveling wave rotates the rotor.

WO2010/061508

In recent years, there has been a demand for further improvements in the rotational efficiency of ultrasonic motors. However, in the ultrasonic motor of Patent Document 1, it was difficult to sufficiently improve the rotational efficiency.

An object of the present invention is to provide an ultrasonic motor that can improve rotational efficiency.

An ultrasonic motor according to the present invention includes a plate-like vibrating body including first and second main surfaces facing each other, and a piezoelectric element provided on the first main surface of the vibrating body. and a rotor in contact with the second main surface of the vibrating body, the vibrating body vibrating in a B (1, N) mode and the first main surface of the vibrating body and a groove is provided in at least one of the second main surface, and in a plan view of the first main surface, the groove has a circular shape and is more likely to vibrate than the piezoelectric element. Close to the center of gravity of the body.

According to the ultrasonic motor according to the present invention, it is possible to increase the rotation efficiency.

FIG. 1 is a front cross-sectional view of an ultrasonic motor according to a first embodiment of the invention. FIG. 2 is a bottom view of the stator in the first embodiment of the invention. FIG. 3 is a schematic diagram for explaining each vibration mode. FIG. 4 is a diagram showing the relationship between the distance from the center of the vibrating body and the Z component of displacement in a comparative example. FIG. 5 is a diagram showing the relationship between the distance from the center of the vibrating body and the Z component of displacement in the ultrasonic motor according to the first embodiment of the present invention. FIG. 6 is a front sectional view of the first piezoelectric element in the first embodiment of the invention. 7(a) to 7(c) are schematic bottom views of the stator for explaining traveling waves excited in the first embodiment of the present invention. FIG. 8 is a bottom view of a stator in a modification of the first embodiment of the invention. FIG. 9 is a plan view of a stator according to a second embodiment of the invention. FIG. 10 is a front sectional view of a stator according to a third embodiment of the invention. FIG. 11 is a schematic control circuit diagram of an ultrasonic motor system according to a fourth embodiment of the invention.

Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

It should be noted that each embodiment described in this specification is an example, and partial replacement or combination of configurations is possible between different embodiments.

FIG. 1 is a front cross-sectional view of an ultrasonic motor according to the first embodiment of the present invention.

The ultrasonic motor 1 has a stator 2 and a rotor 4. The stator 2 and rotor 4 are in contact. A traveling wave generated in the stator 2 causes the rotor 4 to rotate. A specific configuration of the ultrasonic motor 1 will be described below.

The stator 2 has a vibrating body 3. The vibrating body 3 is disc-shaped. The vibrating body 3 has a first main surface 3a and a second main surface 3b. The first main surface 3a and the second main surface 3b face each other. In this specification, the axial direction Z is a direction connecting the first main surface 3a and the second main surface 3b and along the rotation center axis. Note that the shape of the vibrating body 3 is not limited to a disk shape. The shape of the vibrating body 3 viewed from the axial direction Z may be, for example, a regular polygon such as a regular hexagon, regular octagon, or regular decagon. The vibrating body 3 is made of an appropriate metal. However, the vibrating body 3 does not necessarily have to be made of metal. The vibrating body 3 may be composed of other elastic bodies such as ceramics, silicon material, or synthetic resin, for example.

In this specification, the direction viewed from the axial direction Z may be referred to as plan view or bottom view. Note that the plan view is the direction viewed from above in FIG. 1, and the bottom view is the direction viewed from below. For example, the direction seen from the second main surface 3b side of the vibrating body 3 to the first main surface 3a side is the plan view, and the direction seen from the first main surface side 3a to the second main surface 3b side is the bottom surface. It is sight.

FIG. 2 is a bottom view of the stator in the first embodiment.

A plurality of piezoelectric elements are provided on the first main surface 3 a of the vibrating body 3 . More specifically, the plurality of piezoelectric elements are a first piezoelectric element 13A, a second piezoelectric element 13B, a third piezoelectric element 13C and a fourth piezoelectric element 13D. The plurality of piezoelectric elements are distributed along the circulating direction of the traveling wave so as to generate a traveling wave circulating around an axis parallel to the axial direction Z. As shown in FIG. When viewed from the axial direction Z, the first piezoelectric element 13A and the third piezoelectric element 13C face each other across the axis. The second piezoelectric element 13B and the fourth piezoelectric element 13D face each other across the axis.

Note that the stator 2 may have one piezoelectric element divided into a plurality of regions. In this case, for example, each region of the piezoelectric element may be polarized in different directions. Therefore, in this specification, one piezoelectric element and a plurality of piezoelectric elements having different polarization directions for each region may be referred to as a plurality of polarized piezoelectric elements.

A groove 5 is provided on the first main surface 3a of the vibrating body 3. In plan view, the groove portion 5 has a circular shape. However, the groove portion 5 does not necessarily have to be a perfect circle, and may contain an error that does not affect the performance of the ultrasonic motor 1 . Furthermore, in a plan view, the groove portion 5 is provided inside the plurally polarized piezoelectric element. In other words, the groove portion 5 is closer to the center of gravity G of the vibrating body 3 than the piezoelectric element polarized in plural. In this embodiment, the center of gravity G of the vibrating body 3 is positioned at the center of the vibrating body 3 . In addition, the groove part 5 should just be provided in at least one of the 1st main surface 3a and the 2nd main surface 3b. Here, the plurally polarized piezoelectric elements vibrate the vibrating body 3 in vibration modes including nodal lines extending in the circumferential direction and the radial direction.

FIG. 3 is a schematic diagram for explaining each vibration mode. Specifically, FIG. 3 shows the phase of vibration in each region of the vibrating body 3 when viewed from above. Regions marked with a + sign and regions marked with a - sign indicate that the vibration phases are opposite to each other.

When the number of nodal lines extending in the circumferential direction is M and the number of nodal lines extending in the radial direction is N, the vibration mode can be expressed as a B (M, N) mode. In this embodiment, the B(1,N) mode is used. That is, the number M of nodal lines extending in the circumferential direction should be 1, and the number N of nodal lines extending in the radial direction should be 0 or any natural number.

As shown in FIG. 1, the rotor 4 is in contact with the second main surface 3b of the vibrating body 3. The rotor 4 has a rotor body 4a and a rotating shaft 4b. The rotor body 4a is disc-shaped. One end of the rotating shaft 4b is connected to the rotor body 4a. The rotor body 4a is in contact with the second main surface 3b of the vibrating body 3. As shown in FIG. In addition, the shape of the rotor main body 4a is not limited to a disc shape. The shape of the rotor main body 4a in plan view may be, for example, a regular polygon such as a regular hexagon, a regular octagon, or a regular decagon.

A feature of this embodiment is that the vibrating body 3 has the groove portion 5 described above. By providing the groove portion 5 in the stator 2 in this way, the vibration energy can be increased by concentrating the vibration energy on the outside of the groove portion 5 . As a result, the coupling coefficient of the plurally polarized piezoelectric elements in the ultrasonic motor 1 can be increased, and the amplitude of the vibrating body 3 can be increased. Therefore, the rotor 4 can be efficiently rotated, and the rotation efficiency of the ultrasonic motor 1 can be improved. The details will be shown below by comparing the present embodiment and a comparative example. Note that the comparative example differs from the present embodiment in that the vibrating body is not provided with grooves.

In the ultrasonic motor 1 having the configuration of the first embodiment and the ultrasonic motor of the comparative example, the relationship between the position of the vibrating body and the Z component of the displacement was obtained by simulation. The Z component of displacement is the axial Z component of the displacement. In the following description, the position on the vibrating body is shown as the distance from the center of the vibrating body. FIG. 5 shows the results when the width of the groove 5 is 0.5 mm and the depth is 1.2 mm in the ultrasonic motor 1 having the configuration of the first embodiment. Note that the vibrating body in the first embodiment and the comparative example has a radius of 19 mm and a thickness of 1.4 mm.

FIG. 4 is a diagram showing the relationship between the distance from the center of the vibrating body and the Z component of displacement in a comparative example. FIG. 5 is a diagram showing the relationship between the distance from the center of the vibrating body and the Z component of displacement in the ultrasonic motor according to the first embodiment. In FIGS. 4 and 5, the 0 mm position on the horizontal axis is the center of the vibrator. The larger the Z component of the displacement of the vibrating body shown on the vertical axis, the larger the amplitude of the vibrating body.

As shown in FIG. 4, in the comparative example, the Z component of the displacement reaches its maximum value near the distance of 11.1 mm from the center of the vibrating body. The maximum value is 211.9 nm. Let r be the radial dimension of the portion of the vibrating body where the Z component of the displacement is 210 nm or more. In the comparative example, the dimension r is approximately 0.5 mm.

On the other hand, as shown in FIG. 5, in the first embodiment, the Z component of the displacement reaches its maximum value near the distance of 10.3 mm from the center of the vibrating body. The maximum value is 223.6 nm. It can be seen that the amplitude can be made larger in the first embodiment than in the comparative example. Furthermore, the dimension r is widened to about 3.4 mm. In this way, the amplitude can be increased over a wide range of the vibrating body 3 .

In the comparative example, a plurality of piezoelectric elements vibrate the entire vibrating body. On the other hand, in the first embodiment, the vibrating body 3 is provided with the groove portion 5 . As a result, the vibration is less likely to be transmitted to the inner side of the groove portion 5, and the outer side of the groove portion 5 is more likely to vibrate. That is, the vibration energy generated by the plurality of piezoelectric elements is concentrated on the outside of the groove portion 5 . Therefore, in the stator 2, the coupling coefficient of the plurality of piezoelectric elements can be increased, and the amplitude of the vibrating body 3 can be increased. As described above, the stator 2 is in contact with the rotor 4 and causes the rotor 4 to rotate by traveling waves. Since the amplitude of the traveling wave in the stator 2 can be increased, the rotor 4 can be efficiently rotated. Therefore, the rotational efficiency of the ultrasonic motor 1 can be enhanced.

In addition, in the first embodiment, it is possible to widen the area of the portion of the vibrating body 3 where the amplitude is large. Thereby, the area of the portion where the stator 2 propagates the traveling wave to the rotor 4 can be widened. Therefore, it is possible to suppress the occurrence of local friction between the stator 2 and the rotor 4 due to the propagation of the traveling wave, and the wear of the stator 2 and the rotor 4 can be suppressed. Therefore, fluctuations in torque can be suppressed, and driving of the ultrasonic motor 1 can be stabilized. Furthermore, the life of the ultrasonic motor 1 can be extended.

In addition, since the area of the portion of the vibrating body 3 where the amplitude is large can be increased, the rotational efficiency of the ultrasonic motor 1 can be sufficiently increased even if the stator 2 is small. Therefore, the ultrasonic motor 1 can be miniaturized.

Here, when the width of the groove portion 5 is Wg and the radius of the vibrating body 3 is Rs, the ratio of the width Wg to the radius Rs is in the range of 0.05%≦(Wg/Rs)×100≦15.78%. preferably within As a result, the area of the large-amplitude portion can be further increased. In the first embodiment, the width Wg corresponding to the above range is 0.01 mm or more and 3 mm or less, and the radius Rs is 19 mm. However, the range of width Wg and radius Rs are not limited to the above. It is sufficient that the groove portion 5 is provided at a position that does not include the center of vibration.

When the depth of the groove 5 is Dg and the thickness of the stator is Ts, the ratio of the depth Dg to the thickness Ts is within the range of 14.28%≦(Dg/Ts)×100≦85.71%. is preferred. As a result, the area of the large-amplitude portion can be further increased. In the first embodiment, the range of depth Dg corresponding to the above range is 0.1 mm or more and 1.2 mm or less, and the thickness Ts is 1.4 mm. However, the range of depth Dg and thickness Ts are not limited to the above.

By the way, as shown in FIG. 1, the groove portion 5 has an outer peripheral edge 5a. When the distance between the outer peripheral edge 5a and the center of the vibrating body 3 is Lg, the ratio of the distance Lg to the radius Rs of the vibrating body 3 is 30.63%≦(Lg/Rs)×100≦43. It is preferably in the range of 0.79%. As a result, the plurally polarized piezoelectric elements can be more reliably arranged at positions where the vibrating body 3 can be suitably vibrated. Therefore, the amplitude can be increased more reliably. The distance between each piezoelectric element and the groove portion 5 in plan view should be 0 mm or more.

In this embodiment, the rotor 4 is in direct contact with the second main surface 3b of the vibrating body 3 of the stator 2. A friction material may be fixed to the surface of the rotor 4 on the stator 2 side. In this case, the rotor 4 is in indirect contact with the second main surface 3b via the friction material. Thereby, the frictional force applied between the oscillator 3 of the stator 2 and the rotor 4 can be stabilized. Thereby, the rotor 4 can be rotated more efficiently.

The specific configuration and traveling wave of the piezoelectric element in the first embodiment will be described below.

FIG. 6 is a front sectional view of the first piezoelectric element in the first embodiment.

The first piezoelectric element 13A has a piezoelectric body 14. The piezoelectric body 14 has a third principal surface 14a and a fourth principal surface 14b. The third main surface 14a and the fourth main surface 14b face each other. The first piezoelectric element 13A has a first electrode 15A and a second electrode 15B. A first electrode 15A is provided on the third main surface 14a of the piezoelectric body 14, and a second electrode 15B is provided on the fourth main surface 14b. The second piezoelectric element 13B, the third piezoelectric element 13C, and the fourth piezoelectric element 13D are configured similarly to the first piezoelectric element 13A. Each piezoelectric element has a rectangular shape in plan view. Note that the shape of each piezoelectric element in a plan view is not limited to the above, and may be, for example, an elliptical shape.

Here, the first electrode 15A is attached to the first main surface 3a of the vibrating body 3 with an adhesive. The thickness of this adhesive is very thin. Therefore, the first electrode 15A is electrically connected to the vibrating body 3. As shown in FIG.

In order to generate a traveling wave, the stator 2 should have at least the first piezoelectric element 13A and the second piezoelectric element 13B. Alternatively, it may have one piezoelectric element divided into a plurality of regions. In this case, for example, each region of the piezoelectric element may be polarized in different directions.

A structure in which a plurality of piezoelectric elements are distributed in the circumferential direction in the stator 2 and driven to generate a traveling wave is disclosed, for example, in Patent Document 1 (International Publication No. 2010/061508). In addition, about the structure which generates this traveling wave, suppose that not only the following description but the structure of international publication 2010/061508 is used for this specification, and detailed description is abbreviate|omitted.

FIGS. 7(a) to 7(c) are schematic bottom views of the stator for explaining traveling waves excited in the first embodiment. In FIGS. 7(a) to 7(c), in the gray scale, the closer to black, the greater the stress in one direction, and the closer to white, the greater the stress in the other direction.

Fig. 7(a) shows a three-wave standing wave X, and Fig. 7(b) shows a three-wave standing wave Y. Assume that the first to fourth piezoelectric elements 13A to 13D are arranged with a central angle of 90°. In this case, since three standing waves X and Y are excited, the central angle with respect to the wavelength of the traveling wave is 120°. The central angle is determined by multiplying the angle of one wave of 120° by 3/4 to determine the angle of 90°. The first piezoelectric element 13A is arranged at a predetermined place where the amplitude of the three-wave standing wave X is large, and the second to fourth piezoelectric elements 13B to 13D are arranged at intervals of 90° of the central angle. In this case, three standing waves X and Y having vibration phases different by 90° are excited, and the two are combined to generate the traveling wave shown in FIG. 7(c).

Note that A+, A−, B+, and B− in FIGS. 7(a) to 7(c) indicate the polarization directions of the piezoelectric body 14. FIG. + means that it is polarized from the third main surface 14a toward the fourth main surface 14b in the thickness direction. - indicates that it is polarized in the opposite direction. A indicates the first piezoelectric element 13A and the third piezoelectric element 13C, and B indicates the second piezoelectric element 13B and the fourth piezoelectric element 13D.

Although an example of three waves has been shown, it is not limited to this, and in the case of six waves, nine waves, twelve waves, etc., two standing waves having phases different by 90° are similarly excited, and a traveling wave is synthesized by combining the two standing waves. occurs. In the present invention, the configuration for generating traveling waves is not limited to the configurations shown in FIGS. 7A to 7C, and various conventionally known configurations for generating traveling waves can be used.

By the way, in the first embodiment shown in FIG. 1, the rotor 4 has a rotor body 4a and a rotating shaft 4b. However, a shaft member that is separate from the rotor 4 may be provided. In this case, the rotor 4 may be a member corresponding to the rotor main body 4a. When the shaft member is provided, the vibrator of the stator and the rotor may each be provided with a through hole. A shaft member may be inserted through each of the through holes. In this case, each of the through-holes should be located in a region including the center in the axial direction.

FIG. 8 is a bottom view of the stator in the modified example of the first embodiment.

In this modified example, a first groove portion 25 and a second groove portion 26 are provided on the first principal surface 3a of the vibrating body 23 . The first groove portion 25 is the groove portion 5 in the first embodiment. Therefore, the first groove portion 25 is provided inside the piezoelectric element that is polarized in a plurality of ways in plan view. On the other hand, the second groove portion 26 is provided outside the plurally polarized piezoelectric element in plan view. The second groove portion 26 has a circular shape in plan view. Also in this case, as in the first embodiment, it is possible to increase the coupling coefficient of the plurally polarized piezoelectric elements and increase the amplitude of the vibrating body 23 . Therefore, the rotation efficiency of the ultrasonic motor can be enhanced.

As shown in FIG. 1, in the first embodiment, the main surface on which the grooves 5 are provided is the same as the main surface on which the plurally polarized piezoelectric elements are provided. However, the main surface on which the grooves 5 are provided may be different from the main surface on which the plurally polarized piezoelectric elements are provided. An example of this is illustrated by the second embodiment below.

FIG. 9 is a plan view of the stator in the second embodiment.

This embodiment differs from the first embodiment in that the groove 5 is provided on the second main surface 3b of the vibrating body 33 and the groove 5 is not provided on the first main surface 3a. Except for the above points, the ultrasonic motor of this embodiment has the same configuration as the ultrasonic motor 1 of the first embodiment.

Also in the present embodiment, as in the first embodiment, the vibration energy generated by the piezoelectric element polarized in plural can be concentrated on the outside of the groove portion 5 . Therefore, the coupling coefficient of the plurally polarized piezoelectric elements can be increased, and the amplitude of the vibrating body 33 can be increased. Therefore, the rotational efficiency of the ultrasonic motor can be enhanced. Furthermore, the area of the portion of the vibrating body 33 where the amplitude is large can be widened.

As in the first embodiment, a simulation was performed by changing the width Wg and depth Dg of the groove portion 5, and the range in which the area of the large amplitude portion can be further increased was obtained. A ratio of the width Wg to the radius Rs of the vibrating body 33 is preferably within the range of 10.52%≦(Wg/Rs)×100≦15.78%. As a result, the area of the large-amplitude portion can be further increased. On the other hand, the ratio of the depth Dg to the stator thickness Ts is preferably within the range of 7.14%≦(Dg/Ts)×100≦85.71%. Also in this case, the area of the portion with large amplitude can be further increased.

The ratio of the distance Lg between the outer peripheral edge 5a of the groove 5 and the center of the vibrating body 33 to the radius Rs of the vibrating body 33 is in the range of 30.63%≦(Lg/Rs)×100≦43.79%. preferably within As a result, the plurally polarized piezoelectric elements can be more reliably arranged at positions where the vibrating body 33 can be vibrated appropriately. Therefore, the amplitude can be increased more reliably. The distance between each piezoelectric element and the groove portion 5 in plan view should be 0 mm or more.

It should be noted that, in the present embodiment, the plurally polarized piezoelectric elements and the grooves 5 are provided on different main surfaces. In this case, the distance between the piezoelectric element and the groove portion 5 in plan view is the distance between the groove portion 5 and the projection of the piezoelectric element on the main surface on which the groove portion 5 is provided in plan view. is.

　In the modification of the first embodiment shown in FIG. However, the first groove portion 25 and the second groove portion 26 shown in FIG. 8 may be provided on the second main surface 3b of the vibrating body 33 shown in FIG. Alternatively, the first groove portion 25 and the second groove portion 26 may be provided on different main surfaces. In these cases, similarly to the second embodiment, it is possible to increase the coupling coefficient of the plurally polarized piezoelectric elements and increase the amplitude of the vibrator. Therefore, the rotation efficiency of the ultrasonic motor can be enhanced.

FIG. 10 is a front sectional view of the stator in the third embodiment.

This embodiment differs from the first embodiment in that grooves are provided on both the first main surface 3a and the second main surface 3b of the vibrating body 43. FIG. Except for the above points, the ultrasonic motor of this embodiment has the same configuration as the ultrasonic motor 1 of the first embodiment. The groove provided on the first main surface 3 a is the first groove 25 , and the groove provided on the second main surface 3 b is the third groove 47 . The first groove portion 25 corresponds to the groove portion 5 in the first embodiment, and the third groove portion 47 corresponds to the groove portion 5 in the second embodiment.

In this embodiment, the first groove portion 25 and the third groove portion 47 overlap in plan view. However, in plan view, the first groove portion 25 and the third groove portion 47 do not have to overlap. In plan view, both the first groove portion 25 and the third groove portion 47 need only be arranged inside the piezoelectric element that is polarized in plurality.

Even in the case where the vibrating body 43 is provided with the first groove portion 25 and the third groove portion 47, the energy of the vibration generated by the piezoelectric element polarized in multiple ways is transferred to the first groove portion 25 as in the first embodiment. and outside the third groove 47 . Therefore, the coupling coefficient of the plurally polarized piezoelectric elements can be increased, and the amplitude of the vibrating body 43 can be increased. Therefore, the rotational efficiency of the ultrasonic motor can be enhanced. Furthermore, the area of the portion of the vibrating body 43 where the amplitude is large can be widened.

Here, an example of an ultrasonic motor system using the ultrasonic motor according to the present invention is shown below.

FIG. 11 is a schematic control circuit diagram of the ultrasonic motor system according to the fourth embodiment.

The ultrasonic motor system 50 has an ultrasonic motor 51 and a drive control device 52 . The ultrasonic motor 51 differs from the first embodiment in that it has a speed detection terminal 53A and a capacitance detection terminal 53B. Except for the above points, the ultrasonic motor 51 of this embodiment has the same configuration as the ultrasonic motor 1 of the first embodiment. The speed detection terminal 53A and the capacitance detection terminal 53B are provided on the piezoelectric body 14 of the first piezoelectric element 13A shown in FIG.

The drive control device 52 has a filter section 54A, a speed detection section 55, a control section 56, a drive circuit section 57, a capacitance detection section 58, a filter section 54B, and a temperature calculation section 59. A speed detection terminal 53A of the ultrasonic motor 51 is connected to a speed detection section 55 via a filter section 54A. The speed detector 55 is connected to the controller 56 . A capacity detection terminal 53B of the ultrasonic motor 51 is connected to the capacity detection section 58 . The capacitance detection section 58 is connected to the temperature calculation section 59 via the filter section 54B. The temperature calculator 59 is connected to the controller 56 . The control section 56 is connected to the drive circuit section 57 . Furthermore, the drive circuit section 57 is connected to each piezoelectric element of the ultrasonic motor 51 .

The speed detection terminal 53A of the ultrasonic motor 51 outputs a signal corresponding to the driving speed of the ultrasonic motor 51 to the speed detection section 55. The filter section 54A filters the signal output from the speed detection terminal 53A to the speed detection section 55. FIG. The speed detector 55 detects the driving speed of the ultrasonic motor 51 .

The capacitance detection terminal 53B of the ultrasonic motor 51 outputs a signal corresponding to the capacitance of the first piezoelectric element 13A in the ultrasonic motor 51 to the capacitance detection section 58. The capacitance detector 58 detects the capacitance of the first piezoelectric element 13A. Capacitance detector 58 outputs a signal corresponding to the detected capacitance to temperature calculator 59 . The filter section 54B filters the signal output from the capacitance detection section 58 to the temperature calculation section 59 .

The control unit 56 sets driving conditions for the ultrasonic motor 51 . The drive circuit section 57 applies a drive voltage to each piezoelectric element of the ultrasonic motor 51 based on the drive conditions set by the control section 56 .

The stator of the ultrasonic motor 51 is constructed in the same manner as in the first embodiment. Therefore, in the ultrasonic motor 51 as well, grooves are provided inside the piezoelectric elements that are polarized in a plurality of ways in a plan view. Therefore, similarly to the first embodiment, it is possible to increase the coupling coefficient of the plurally polarized piezoelectric elements and increase the amplitude of the vibrating body. Therefore, the rotation efficiency of the ultrasonic motor can be enhanced. Furthermore, the area of the portion of the vibrating body where the amplitude is large can be widened.

Since the ultrasonic motor system 50 has the ultrasonic motor 51 according to the present invention, it is possible to increase the area of the portion of the vibrating body of the stator where the amplitude is large, thereby suppressing the wear of the stator and rotor. can. Therefore, torque fluctuations can be suppressed, and driving of the ultrasonic motor 51 in the ultrasonic motor system 50 can be stabilized. Furthermore, the life of the ultrasonic motor system 50 can be extended.

In this embodiment, the ultrasonic motor 51 has a speed detection terminal 53A and a capacitance detection terminal 53B. Therefore, an angular velocity sensor and a temperature sensor are unnecessary. Therefore, the number of parts can be reduced. However, the ultrasonic motor system 50 is an example, and the configuration is not limited to the above. Ultrasonic motor system 50 may have an angular velocity sensor or a temperature sensor. The ultrasonic motor system 50 is not limited to the ultrasonic motor 51 as long as it has an ultrasonic motor according to the present invention.

DESCRIPTION OF SYMBOLS 1... Ultrasonic motor 2... Stator 3... Vibrating

body

3a, 3b... First and second main surfaces 4... Rotor 4a... Rotor main body 4b... Rotating shaft 5... Groove part 5a... Outer peripheral edge 13A to 13D... First to first Piezoelectric elements of 4 14

Piezoelectric bodies

14a, 14b Third and fourth

main surfaces

15A, 15B First and second electrodes 23 Vibrating

bodies

25 and 26 First and second grooves 32

Stator

33 , 43... Vibrating body 47... Third groove 50... Ultrasonic motor system 51... Ultrasonic motor 52... Drive control device 53A... Speed detection terminal 53B...

Capacitance detection terminal

54A, 54B... Filter section 55... Speed detection section 56... Control section 57 Drive circuit section 58 Capacitance detection section 59 Temperature calculation section G Center of gravity

Claims

a stator having a plate-like vibrating body including first and second main surfaces facing each other; and a piezoelectric element provided on the first main surface of the vibrating body;
a rotor in contact with the second main surface of the vibrating body;
with
The vibrating body vibrates in B (1, N) mode,
A groove is provided in at least one of the first main surface and the second main surface of the vibrating body, and the groove has a circular shape in plan view of the first main surface. and located closer to the center of gravity of the vibrator than the piezoelectric element.
the groove is a first groove,
A second groove is provided in at least one of the first main surface and the second main surface of the vibrating body, and the second groove has a circular shape in plan view. , and located outside the piezoelectric element.
The ultrasonic motor according to claim 1 or 2, wherein the grooves are provided on both the first main surface and the second main surface.