JPH04121071A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain a highly efficient and small size ultrasonic motor without changing the fundamental construction of the motor by a method wherein at least the effective part of a piezoelectric device where electrode patterns are provided is formed into an annular shape having a certain width from the outer circumference and the rigidity of the part of a vibrating unit inside the annular part is smaller than the rigidity of the annular part of the vibrating unit. CONSTITUTION:A vibrating unit 1 has a disc-shape and the thickness T1 of its annular circumferential part is larger than the thickness T2 of its inner part. A plurality of protrusions 1a are formed on the annular circumferential part. A piezoelectric device 2 has approximately the same shape as the annular thick part of the vibrating unit 1 and attached to the surface of the annular part opposite to the surface on which the protrusions 1a are provided by bonding, etc. The vibrating unit 1 is unified with a center shaft 4 which is planted in a support plate 3 by pushing the center shaft 4 into the center part of the vibrating unit 1. A moving unit 5 is supported by the center shaft 4 with the center shaft 4 as the center of rotation and pressed against the top parts of the protrusions 1a of the vibrating unit 1 by a pressing spring 6. Lead wires 7 are bonded to the electrode patterns of the piezoelectric device by soldering, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor that generates driving force using the piezoelectric action of a piezoelectric element.

[Summary of the invention]

The present invention provides an ultrasonic motor that generates a driving force using the piezoelectric action of a piezoelectric element, in which an effective part of the piezoelectric element including at least an electrode pattern is formed in an annular shape, and the rigidity of the vibrating body of the annular part is lower than the rigidity of the vibrating body of the annular part. By reducing the rigidity of the vibrating body inside the shape, it is possible to make the ultrasonic motor smaller, stabilize its performance, and increase its efficiency.

[Conventional technology]

Conventionally, an ultrasonic motor having a structure as shown in FIG. 12 has been known. In the conventional ultrasonic motor, the center of the vibrating body 1 is fixedly supported on a central shaft 4 installed on a support plate 3. Then, the vibrating body l is set with the central axis 4 as a guide for the center of rotation.
A movable body 5 is provided which comes into pressure contact with the outer periphery of. Further, as a pressurizing mechanism for the movable body 5, a pressurizing spring 6 is fixed on the central axis with a washer 8 and a stopper 9. Vibrating body 1 and vibrating body 1
The piezoelectric element 2 bonded to the piezoelectric element 2 has a disk shape with only a guide hole in the center. By applying a high frequency voltage to this piezoelectric element 2, a deflection vibration wave is excited in the vibrating body 1,
The moving body 5 rotates through the frictional force with the vibrating body 1. For example, such a conventional structure is disclosed in Japanese Patent Application Laid-Open No. 63-305770.

[Problem to be solved by the invention]

In an ultrasonic motor as shown in FIG. 12, a case where the radial vibration mode of the vibrating body is primary and a case where the vibration mode is secondary will be compared. When the vibration mode is first order, the resonance frequency is approximately χ compared to the second order, and when compared in size, the size can be reduced by about 2 times. That is, the use of the radial-order mode is advantageous for downsizing and lowering the frequency. - In the next mode, the amplitude is maximum at the outer periphery of the vibrating body, and from the side of the moving body being driven, it is higher torque to obtain rotational force at the outer periphery, so in order to increase the efficiency of the motor, it is necessary to It is preferable to provide the pressure contact portion of the body on the outer periphery. However, as shown in Figure 12 (by pressing the moving body with the outer periphery of the vibrating body, the deformation of the vibrating body is suppressed and the internal strain of the vibrating body is not released, so it is not sufficient as a vibrator. However, the problem was that proper excitation could not be obtained, and as a result, the performance of the motor deteriorated.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to obtain a small and highly efficient ultrasonic motor without changing the basic structure of the motor.

[Means to solve the problem]

In order to solve the above problems, in the present invention, the effective part of the piezoelectric element having at least the electrode pattern is formed into an annular shape having a constant width from the outer periphery, and the rigidity of the vibrating body of the annular part is inside the annular shape. By reducing the rigidity of the vibrating body in this area, making it easier to release the strain in the vibrating body in this region, and obtaining sufficient excitation as a vibrator, it has become possible to make the ultrasonic motor more compact and highly efficient.

[Effect]

In the ultrasonic motor configured as described above, even if the vibrating body that vibrates in the following mode is pressed by the moving body on the outer periphery,
Since strain is released in the inner part of the annular shape with low rigidity, sufficient excitation can be obtained as a vibrator. Furthermore, as mentioned above, in the case of the primary mode, it is possible to reduce the size and lower the frequency, and furthermore, because of the outer periphery pressure welding, high torque can be obtained. This makes it possible to realize a compact ultrasonic module with high performance stability and high efficiency.

(Example〕 Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram of a first embodiment of an ultrasonic motor according to the present invention. The vibrating body 1 has a disk shape, and the thickness T+ of the annular portion on the outer periphery is thicker than the thickness T2 of the inner portion, and a plurality of protrusions 1a are formed in this annular portion. The piezoelectric element 2 has substantially the same shape as the annular plate thickness portion of the vibrating body 1, and is bonded to the surface opposite to the protrusion 1a by adhesive or the like.

The vibrating body 1 is integrated at its center with a central shaft 4 set on a support plate 3 by pressing or the like. The movable body 5 is rotatably supported around a central axis 4, and is pressed against the upper surface of the projection 1a of the vibrating body 1 by a pressure spring 6. A lead wire 7 is connected to the electrode pattern of the piezoelectric element 2 by soldering or the like.

By applying a high frequency voltage to the piezoelectric element 2 via the lead vA7, the vibrating body 1 generates a deflection vibration wave, and the movable body 5 pressed against the vibrating body 1 rotates by frictional drive. There are various vibration modes of flexural vibration waves, but compared to the radial second-order mode, the resonance frequency of the first-order moat is approximately A, and the diameter is about 2 when compared on a frequency basis. The following modes are advantageous: The ultrasonic motor shown in Fig. 1 is also in the following mode in the radial direction, but the outer peripheral plate r\T
Since the inner plate thickness T2 is thinner than the part 1, even if the maximum amplitude part of the outer periphery is pressed against the moving body 1, the stiffness of the inner thin plate part is low, so the strain is released and sufficient excitation is not achieved. can get. This makes it possible to realize a compact ultrasonic motor with high efficiency and stable performance. Furthermore, there are two types of flexural vibration waves: a traveling wave type and a standing wave type, and the same effect can be obtained in either case as long as the configuration is as described above.

FIG. 2 shows a second embodiment of the present invention, in which the vibrating body l
Although it has a disk shape and has a constant thickness over the entire surface, an annular piezoelectric element 2 is bonded to the outer periphery by adhesive or the like, and a plurality of protrusions 1a are formed where the annular portion overlaps. The other structures are the same as those in the first embodiment. In this case, the rigidity of the vibrating body 1 alone is uniform, but the rigidity of the vibrator including the piezoelectric element 2 is the same as that of the piezoelectric element 2.
The inner portion is smaller than the annular portion joined together, and the same effect as in the first embodiment can be obtained with a simpler shape of the vibrating body.

FIG. 3 shows a third embodiment of the present invention, in which the vibrating body l
has a disk shape, and the plate thickness T1 of the annular portion on the outer periphery is thicker than the plate thickness T2 of the inner portion, and a plurality of protrusions 1a are formed in this annular portion. The piezoelectric element 2 has a disk shape, and is joined to the vibrating body 1 while being guided by a protrusion 1b provided at the center. The other structure is the same as that of the first embodiment. In this case, the difference in rigidity between the annular part and the inner side is smaller because the piezoelectric element 2 is bonded to the entire surface, but since the thickness of the vibrating body 1 is different, the inner stiffness is smaller, and it is the same as in the first embodiment. have an effect. Further, since the piezoelectric element 2 is disk-shaped, the piezoelectric element itself has high rigidity and is easy to handle. t+T
Since guidance is possible, it has the effect of improving the workability of bonding, etc.

The fourth example shows the fourth embodiment of the present invention.
is thicker than the plate thickness T2 of the inner portion, and a plurality of protrusions 1a are formed in this annular portion. Piezoelectric element 2
has a disc shape, and has a protrusion 1b provided at the center of the vibrating body 1.
It is joined as guided by. The electrode pattern 2a of the piezoelectric element 2 is formed only on a portion corresponding to the annular thick plate portion of the vibrating body 1, and no electrode pattern is provided on the inner portion of the annular portion. The other structure is the same as that of the first embodiment. In this case, the stiffness of the vibrating body 1 is reduced on the inside, so the effect is similar to that of the fourth embodiment, but since no electrode pattern is provided on the inner part where the stiffness is small and strain is easily released, the output/input ratio is improved, making it possible to realize a more efficient ultrasonic motor. Furthermore, the protrusion 1b of the vibrating body 1 in the third and fourth embodiments is not necessarily necessary, and there is no problem with a mere flat surface.

FIG. 5 shows a fifth embodiment of the present invention, in which the vibrating body l has a disk shape, and the plate thickness T1 of the annular portion on the outer periphery is thicker than the plate thickness Tz of the central portion, and is gradually thickened from the inside to the outside, and a plurality of protrusions 1a are formed on the outer periphery. The piezoelectric element 2 is a vibrating body l
It has an annular shape along the outer periphery of the projection 1a and is joined to the surface opposite to the projection 1a. The rest of the structure is the same as in the first embodiment. By reducing the thickness of the inner plate of the 6 vibrating bodies,
Although the rigidity is reduced and strain relief is facilitated, the rigidity of the entire structure is also reduced. On the other hand, in the case of - next vibration mode, the strain is maximum at the center, so by making the center thinner and thicker at the outer periphery, the internal strain can be reduced while maintaining the overall rigidity. This has the effect that the opening can be carried out efficiently.

FIG. 6 shows a sixth embodiment of the present invention, (4)
0 is a plan view, and 0 is a sectional view. The vibrating body 1 has a disk shape,
A plurality of protrusions 1a are arranged at equal intervals in an annular shape on the outer periphery,
The inner portion of the ring is provided with a plurality of rings (Ic) extending radially from the center at equal intervals in the circumferential direction. The piezoelectric element 2 has substantially the same annular shape as the arrangement portion of the protrusion 1a of the vibrating body 1, and is joined across the surface on the opposite side of the protrusion 1a.

Electrode patterns 2a and 2b of piezoelectric element 2 are fixed 1
After forming the electrode pattern divided into two parts, as shown in the figure (+
) or (=) direction, and then formed so that every other electrode is connected with an electrode pattern,
Two glues F'H1a and 7b are connected by soldering or the like. The other structure is the same as that of the first embodiment. Here, 9 is connected via lead wires 7a and 7b.
High frequency voltages with different 0' phases are applied to electrode patterns 2a and 2b.
By applying this, a flexural traveling wave having three peaks in the circumferential direction is generated, and the movable body 5 pressed against the protrusion 1a of the vibrating body 1 rotates. In this case, the traveling wave method is used, and since the deflection progresses in the circumferential direction, it is desirable to maintain uniformity in the circumferential direction, so the slits lc are arranged at equal intervals and as many as possible to reduce the rigidity. It is effective to provide For example, in this slit method, the vibrating body 1
This is effective as a means of reducing rigidity in cases where the plate thickness is thin and it is difficult to make the inner part even thinner. This provides the same effect as the first embodiment.

FIG. 7 shows a seventh embodiment of the present invention, in which the vibrating body 1
has a disk shape, and an annular piezoelectric element 2 is bonded to the outer periphery. The electrode pattern 2a of the piezoelectric element is divided into four parts, each of which is polarized as shown. Vibrating body 1
On the surface opposite to the piezoelectric element bonding, four protrusions 1a are provided at equal intervals at an angle as shown in the figure, and four protrusions 1a are provided at equal intervals at the angle shown in the figure in the part overlapping the annular shape of the piezoelectric element 2. Four slits extending radially from the center are formed in the portion at angles that match the boundaries of the electrode pattern of the piezoelectric element. The other structures are the same as those in the first embodiment. When a high frequency voltage is applied to the electrode pattern 2a, a flexural standing wave having two peaks in the circumferential direction is generated, and the movable body 5 pressed against the protrusion 1a of the vibrating body 1 rotates. In this case, it is a standing wave method, and the boundary line of the electrode pattern 2a becomes a node, and the stress is distributed around this area, so it is necessary to provide a slit on the inner side near this boundary line. As a result, the strain is released, and the same effect as in the first embodiment is obtained.

FIG. 8 shows an eighth embodiment of the present invention, in which two waves of the third-order moat in the circumferential direction are overlapped with a shift of X wavelength, and the waves are overlapped on the boundary line of the electrode pattern that generates each mode. A protrusion 1a is provided on the annular portion along the outer periphery, and a slit 1C is provided on the inner portion of the annular ring. In this case as well, since stress is concentrated on the boundary line of the piezoelectric element electrode pattern, by providing the slit lc here, the strain is released, so that the same effect as in the first embodiment can be obtained.

In the cases of FIGS. 5 to 8, the piezoelectric element 2 is annular, but the same effect can be obtained even when a disc-shaped piezoelectric element 2 is used as in the cases of FIGS. 3 and 4. Needless to say, the effect can be obtained, and furthermore, the effect as a disk shape can be obtained.

9, FIG. 1.0, and FIG. 1I show a ninth embodiment, a disciple embodiment, and a disciple-embodiment according to the present invention, and the cases of FIGS. 6, 7, and 8, respectively. It is almost the same, but a fan-shaped window 1d is provided in place of the sulin) lcO of the vibrating body 1 to reduce the rigidity.

C Effects of the Invention] As explained above, the present invention provides that, for a disc-shaped vibrating body, at least the effective portion of the piezoelectric element having an electrode pattern is annular along the outer circumference G of the vibrating body, and the annular portion is By making the rigidity of the vibrating body inside the annular shape smaller than that of the vibrating body, even if the moving body is pressed against the outer periphery of the vibrating body, the strain at the center of the vibrating body can be easily released. A strong excitation can be obtained. As a result, it is compact and has stable performance.
This has the effect of realizing a highly efficient ultrasonic motor.

[Brief explanation of the drawing]

Fig. 1 shows a first embodiment of the present invention, Fig. 2 shows a second embodiment, Fig. 3 shows a third embodiment, Fig. 4 shows a fourth embodiment, Fig. 5 shows a fifth embodiment, and a sixth embodiment. The diagram shows the sixth embodiment, Figure 7 shows the seventh embodiment, the eighth leap shows the eighth embodiment, Figure 9 shows the ninth embodiment, and Figure 10 shows the disciple example. 121E] is a diagram showing a conventional ultrasonic motor. 1... Vibrating body 2... Piezoelectric element 3... Support plate 4... Central shaft 5... Moving body 6... Pressure spring 7... Lead wire 8... Washer 9...・More than stopper

Claims (1)

[Claims] An ultrasonic motor comprising at least a piezoelectric element, a vibrating body that generates a mechanical deflection vibration wave due to the piezoelectric action of the piezoelectric element, and a movable body that makes frictional contact with the vibrating body, wherein at least an electrode pattern of the piezoelectric element is provided. An ultrasonic motor characterized in that an effective part having a ring shape is annular, and the rigidity of the vibrating body is made smaller at an inner part of the annular shape than in the annular part.