JPH0340764A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic motor employing a piezo-electric torsional oscillator having small variabilities by a method wherein the motor is provided with a piezo-electric composite longitudinal-torsional oscillator, into which a Langevin type longitudinal oscillator is inserted, and a rotor to convert expanding oscillation as well as torsional oscillation into a rotating motion about the central axis of the rotor. CONSTITUTION:A rotor 9, supported by a bearing 8, is welded by pressure to one end of a piezo-electric composite longitudinal torsional oscillator 21, 27, into which a piezo-electric longitudinal oscillator 27, having the same length as a piezo-electric torsional oscillator 21 substantially, is inserted into the piezo-electric torsional oscillator 21, through a spring 10. The piezo-electric longitudinal oscillator 27 is fixed by a supporting frame 30 at the position of the node of the resonance of torsional oscillation. According to this method, an ultrasonic motor, having the piezo-electric torsional oscillator 21 having small variabilities, may be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called ultrasonic motor that uses ultrasonic vibration of a piezoelectric vibrator used in OA equipment, etc., and particularly relates to a vertical-torsion vibrator type that has a simple structure. Regarding ultrasonic motors.

[Prior Art] FIG. 8 is a perspective view of a structural example of a vertical-torsional composite vibrator 101 used in a conventional vertical-torsional vibrator type ultrasonic motor, in which a piezoelectric torsional vibrator 102 and a piezoelectric longitudinal vibration Child 103
are joined via a metal hollow cylinder 104, and metal hollow cylinders 105 and 106 are further joined on both sides thereof.

FIG. 9 is a perspective view showing an example of the structure of an ultrasonic motor configured using the longitudinal-torsional compound vibrator 101 shown in FIG. A shaft 107 is erected, and a rotor 109 rotatably supported by a bearing 108 is attached to a coil spring 110 and a nut 1.
11 is pressed against the end face of the vertical-torsion composite vibrator 101.

FIG. 10 shows an example of the structure of the piezoelectric torsional vibrator shown in FIG. 8, and the ring-shaped piezoelectric torsional vibrator 102 is constructed by joining four fan-shaped piezoelectric ceramic plates 112. Each fan-shaped piezoelectric ceramic plate 112 is polarized in the chord direction 112a of the fan, as shown in FIG. When a DC voltage is applied to the fan-shaped piezoelectric ceramic plate, a sliding strain parallel to the plate thickness occurs.

As shown in FIG. 10, when four fan-shaped piezoelectric ceramic plates 112 are joined in a ring shape, the sliding strain generated in each fan-shaped piezoelectric ceramic plate 112 is combined, and the upper and lower surfaces of the ring are It becomes a twisting distortion.

When manufacturing the conventional piezoelectric torsional vibrator shown in FIG. 10, first, as shown in FIG. 12, a fan-shaped piezoelectric ceramic plate is formed by ultrasonic processing from a piezoelectric ceramic plate 113 that has been polarized in the width direction. Punch out a fan-shaped piezoelectric ceramic plate 112 polarized in the direction of the chord of the fan as shown in FIG. 11, and then glue four pieces together to form a disk-like structure, as shown in FIG. 13(a). From the piezoelectric ceramic block 114 polarized in the thickness direction as shown in FIG.
As shown in b), cut out regular square prisms 115 so that the polarization direction is in the diagonal direction, and as shown in FIG. After gluing them together and polishing the outer and inner peripheries into a hollow cylindrical shape as shown in FIG. 13(d),
), it is formed by cutting it into a ring shape.

FIG. 14 shows an example of the structure of a conventional piezoelectric vertical vibrator 103, in which a voltage is applied to a piezoelectric ceramic ring 116 that has electrodes on both sides and is polarized in the thickness direction, and vibrates in the thickness direction (
(called longitudinal vibration).

In order to obtain a large vibration amplitude with a low applied voltage, a piezoelectric longitudinal vibrator 103' may be constructed by laminating a plurality of thin piezoelectric ceramic rings 116' as shown in FIG.

[Problems to be Solved by the Invention] Since the conventional piezoelectric torsional vibrator 102 shown in FIG. 10 is configured by bonding a plurality of piezoelectric ceramics, there are large variations in characteristics due to bonding. Also,
As shown in FIG. 10, FIG. 11, FIG. 12, and FIG. 13, the processing to obtain the piezoelectric torsional vibrator 102 is complicated and extremely expensive. Furthermore, when trying to obtain torsional vibration and longitudinal vibration at the same time, the first
The piezoelectric torsional vibrator 102 shown in FIG.
Since the piezoelectric longitudinal vibrator 103 or 103' shown in FIG. 5 is bonded, there are also problems of variations in characteristics due to bonding and high bonding costs.

Therefore, the technical problem of the present invention is to eliminate the drawbacks of the conventional piezoelectric torsional vibrators and longitudinal-torsional composite vibrators as described above, and to create a piezoelectric torsional vibrator that is easy to process, does not require a bonding process, and has little variation. and an ultrasonic motor using the same.

Furthermore, another technical object of the present invention is to provide an ultrasonic motor using a piezoelectric longitudinal-torsional composite vibrator in which it is easy to match the resonance frequency of the torsional vibrator and the resonance frequency of the longitudinal vibrator. .

[Means for Solving the Problems] According to the present invention, a plurality of diagonal electrodes are formed on the outer peripheral surface of a piezoelectric ceramic hollow cylinder in parallel to each other and intersecting the central axis,
Polarized by the plurality of diagonal electrodes and applying an alternating current voltage,
It has a piezoelectric torsional vibrator that excites torsional vibration at both ends, and a rod-shaped Langevin type longitudinal vibrator that is formed by bonding a metal material to the end face of the piezoelectric vertical vibrator and excites stretching vibration in the central axis direction, A piezoelectric longitudinal-torsional composite vibrator in which the Langevin type longitudinal vibrator is inserted into a piezoelectric torsional vibrator, and a rotor that is pressed against one end side of the piezoelectric longitudinal-torsional composite vibrator, and the rotor is configured to expand and contract. An ultrasonic motor is obtained, which is characterized in that it converts vibrations and the torsional vibrations into rotational motion about the central axis of the rotor.

[Function] The ultrasonic motor of the present invention includes a piezoelectric region-torsion composite vibrator,
It is equipped with a rotor.

The piezoelectric region-torsion composite vibrator has a piezoelectric torsion vibrator and a rod-shaped Langevin type longitudinal vibrator, and the Langevin type longitudinal vibrator is inserted into the piezoelectric torsion vibrator.

A piezoelectric torsional oscillator has a plurality of diagonal electrodes formed on the outer peripheral surface of a piezoelectric ceramic hollow cylinder in parallel with each other and intersecting the central axis, polarized by the plurality of diagonal electrodes, and applied with an alternating current voltage to produce torsional vibration at both ends. excite.

A rod-shaped Langevin-type vertical vibrator is a piezoelectric torsional vibrator,
It is constructed by bonding a metal material to the end face of a piezoelectric vertical vibrator, and excites stretching vibration in the direction of the central axis.

The rotor is pressed against one end of this piezoelectric region-torsion composite vibrator, and converts these longitudinal vibrations and torsional vibrations into rotational motion about the central axis of the rotor.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an ultrasonic motor according to an embodiment of the present invention. As described later, the piezoelectric torsional vibrator 21
A piezoelectric region-torsion composite vibrator 21 is formed by inserting a piezoelectric longitudinal vibrator 27 of approximately the same length into the piezoelectric region-torsion composite vibrator 21.
A rotor 9 rotatably supported by a bearing 8 is pressed into contact with one end of the rotor 27 via a spring 10.

The piezoelectric vertical vibrator 27 can be supported and fixed at the support frame 30, which is the position of the resonance node of torsional vibration within the piezoelectric torsional vibrator, and can be stably supported.

FIGS. 2(a), (b), (c) and (d) are explanatory views of the operating principle of a piezoelectric torsional vibrator used in an ultrasonic motor according to an embodiment of the present invention.

In FIG. 2(a), a plurality of first and second finger electrodes 18, 19 are formed on one surface of the piezoelectric ceramic plate 17, and the first and second finger electrodes 18, 19 intersect with each other. It is connected to the connecting electrodes 18' and 19' to form interdigital electrodes.

In Fig. 2(b), the dashed arrow indicates the direction of polarization when polarization processing is performed using such interdigital electrodes, and Fig. 2(e) and (d) indicate the direction of polarization in Fig. It shows the state of distortion that occurs when a DC voltage is applied to the polarized piezoelectric ceramic plate 17 as shown in b), and the solid arrow indicates the direction of the electric field.

As shown in Figure 2 (C), when the polarity of the voltage is the same as the polarity of the voltage during polarization, an elongation strain occurs in the direction of polarization, while as shown in Figure 2 (d), the polarity of the voltage If the polarity is opposite to the polarity of the voltage during polarization, shrinkage distortion occurs in the direction of polarization.

FIG. 3 shows the state of distortion that occurs on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 when both end surfaces of the piezoelectric ceramic hollow cylinder 20 are twisted as shown by the arrows in the figure. 45 in the axial direction
Expansion and contraction occur in the direction of the angle ``, moreover, in the direction of the dashed arrow, and shrinkage distortion occurs in the direction perpendicular to this, as shown by the dashed-dotted arrow.

Therefore, first and second interdigital electrodes as shown in FIG. 2 are placed on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 shown in FIG. The hollow cylinder 20 is formed at an angle of 45'' with respect to the length direction, polarization is performed using the first and second interdigital electrodes, and a DC voltage is applied to the same interdigital electrodes. When the polarity of the voltage is the same as the polarity of the voltage during polarization, the piezoelectric ceramic hollow cylinder 20 is twisted in one direction, and when the polarity of the voltage is opposite to the polarity of the voltage during polarization, it is twisted in the opposite direction.

FIG. 4 is a perspective view showing an example of a piezoelectric torsional vibrator used in an ultrasonic motor according to an embodiment of the present invention. In this figure, the piezoelectric torsion oscillators 21 extend on the outer peripheral surface of the center portion of the piezoelectric ceramic hollow cylinder 20- at an angle of 45° with respect to the length direction of the piezoelectric ceramic hollow cylinder 20', and mutually A plurality of intersecting first and second oblique electrodes 22 and 23 are formed alternately in a direction intersecting the length direction of the electrodes, and are arranged at both ends of the circumferential surface of the piezoelectric ceramic hollow cylinder 20''. It is connected to first and second common electrodes 22' and 23' along the direction to form a torsional vibrator 21.

In FIG. 4, a high direct current voltage is applied between the first and second common electrodes 22' and 23', so that the electrodes are perpendicular to the length direction of the first and second diagonal electrodes of the piezoelectric ceramic hollow cylinder 20'. After polarization treatment in the direction, the piezoelectric composite vibrator section 2
When an alternating current voltage with a frequency equal to the resonance frequency of 1 is applied, the piezoelectric ceramic hollow cylinder 20' resonates so that both ends thereof are twisted.

FIG. 5 is a perspective view showing an example of a Hitotsubashi structure of a Langevin type longitudinal vibrator 27 used in an ultrasonic motor according to an embodiment of the present invention. In this figure, a Langevin type longitudinal oscillator 27
, one end of each metal cylinder 25.25 having the same diameter as this piezoelectric vertical vibrator 103 is joined to both ends of the cylindrical piezoelectric vertical vibrator 10B, and further, one end of each of the metal cylinders 25.25 is joined to the other end of each of the metal cylinders 25.25. ,
It is constructed by joining together metal cylinders 25'' and 25- for resonance frequency adjustment, which have a larger diameter than this metal cylinder.

In addition, the metal cylinder 25 and the metal cylinder 25' for adjusting the resonance frequency
It may be formed integrally with.

This Langevin type longitudinal vibrator is widely used in ultrasonic cleaning machines and ultrasonic processing machines. In particular, in order to achieve the resonance frequency of the torsional oscillator 21 with the same length as the torsional oscillator, the diameter near both ends of the Langevin type oscillator is made larger than the diameter at the center.

In the ultrasonic motor of this example, if the diameter of both ends of the vibrator is made larger than that of the center, the resonant frequency will be lower than that of a Langevin type vibrator of the same length and uniform diameter due to the effect of the added mass. We are using.

FIG. 6 is a perspective view showing an example of a piezoelectric longitudinal-torsional vibrator used in the ultrasonic motor of the present invention.

In this figure, the Langevin type vertical vibrator 27 is arranged in the hollow part of the piezoelectric torsional vibrator 21, and the vibration node at the center in the longitudinal direction of the piezoelectric vibrator and the longitudinal direction of the Okina vertical vibrator The vibration nodes in the center are connected using a thin plate-like ring 28. In this case, the vibration state of the piezoelectric longitudinal-torsional vibrator is expressed in terms of amplitude as shown in FIG. 7(a).

That is, in both torsional vibration and longitudinal vibration, the center part of the piezoelectric vertical-torsional vibrator 21°27 vibrates as a node of vibration.

As can be seen from FIG. 7(a), the piezoelectric longitudinal-torsional vibrator 2
Both ends of 1.27 are twisted in opposite directions.

Regarding longitudinal vibration, as shown in FIG. 7(b), if the frequency of the applied voltage is the same as the torsional resonance frequency, both ends of the piezoelectric longitudinal-torsional vibrator 21 and 27 In synchronization with torsional resonance, it causes longitudinal vibration (longitudinal vibration). Therefore, when a rotor rotatably supported at the end of the piezoelectric longitudinal-torsional oscillator 21.27 is pressed with a certain elasticity, the longitudinal oscillator applies buoyancy and the torsional oscillator applies torque to the rotor in half a period, respectively. Rotate the rotor. In this case, the phase of the applied voltage for torsional vibration or longitudinal vibration is set to 180".
If you change it, the direction of rotation will be reversed.

[Effects of the Invention] As shown above, according to the present invention, in a piezoelectric torsional vibrator for an ultrasonic motor, a piezoelectric torsion vibrator that can be easily manufactured by a press molding technique normally applied to fishing boats is used. Piezoelectric torsional oscillators can be obtained by using ceramic hollow cylinders and printing electrodes on their outer peripheral surfaces, which is also a common technique, so manufacturing is easy and the characteristics cannot be changed by bonding or complicated processing steps. A piezoelectric torsional vibrator with little variation can be obtained.

Further, according to the present invention, a Langevin-type vertical vibrator, which has been widely used in the past as a piezoelectric vertical vibrator, is used, and the diameter near both ends is configured to be larger than the diameter of the central portion. It is possible to achieve a highly efficient ultrasonic motor with the same length and approximately the same resonance frequency.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a structural example of an ultrasonic motor according to an embodiment of the present invention, and FIGS. 2(a) and (b). (c) and (d) are explanatory diagrams of how distortion occurs when polarization and voltage are applied using interdigital electrodes, and Figure 3 shows how distortion occurs when a piezoelectric ceramic hollow cylinder is twisted. An explanatory diagram, FIG. 4 is a perspective view showing the structure of a piezoelectric torsional vibrator according to an embodiment of the present invention, and FIG. 5 is a structural example of a pipe-shaped Langevin type longitudinal vibrator used in the ultrasonic motor of the present invention. A perspective view, FIG.
Partially cutaway perspective view showing the structure of a torsional oscillator, FIG. 7(a)
is a diagram showing the relative magnitude of the torsional displacement of the piezoelectric longitudinal-torsional compound vibrator in FIG. 6, and FIG. 7(b) is a diagram showing the relative magnitude of the elongation displacement of the piezoelectric longitudinal-torsional compound vibrator in FIG. 8 is a perspective view showing the structure of a conventional vertical-torsional Langevin type vibrator; FIG. 9 is a perspective view showing the structure of a conventional vertical-torsional ultrasonic motor; FIG. 10 is a diagram showing the size. 11 is a perspective view showing an example of the structure of a conventional torsional oscillator, FIGS. 11 and 12 are explanatory diagrams of an example of the manufacturing process of the conventional torsional oscillator, and FIG. 13(a). (b), (c), (d), and (e) are explanatory diagrams of other examples of the manufacturing process of a conventional torsional oscillator, and FIG. 14 is a perspective view showing an example of the structure of a conventional longitudinal oscillator. FIG. 15 is a perspective view showing another structural example of a conventional longitudinal vibrator. In the figure, 8...Bearing, 9...Rotor 10...
Spring, 17... Piezoelectric ceramic plate, 18.1
9... finger electrode, 18-. 19-... Connection electrode, 20
゜20=...Piezoelectric ceramic hollow cylinder, 21...
Piezoelectric longitudinal vibrator, 27...Piezoelectric torsion composite vibrator, 22°23...Oblique electrode, 22-. 23-... common electrode,
27... Langevin type longitudinal vibrator, 25... Metal cylinder, 25'... Metal cylinder for adjusting resonance frequency, 28.
...Thin ring, 30...Support frame, 101...
Piezoelectric longitudinal-torsional composite vibrator, 102...Piezoelectric torsional vibrator, 103.103-...Piezoelectric longitudinal vibrator, 104°10
5.106...metal hollow cylinder, 107...shaft, 10
8... Bearing, 109... Rotor 110... Spring, 111... Nut, 112... Fan-shaped piezoelectric ceramic plate, 113, 114... Piezoelectric ceramic plate, 115... Piezoelectric ceramic plate Prismatic, 1161
16゛...Piezoelectric ceramic ring. Figure 9 Corrugated iron Figure 10 Figure 11 Figure 12 (e) Figure 13 Shimato 102

Claims (1)

[Claims] 1. A plurality of diagonal electrodes are formed on the outer circumferential surface of a piezoelectric ceramic hollow cylinder in parallel with each other and intersecting the central axis, polarized by the plurality of diagonal electrodes, and an alternating voltage is applied to both ends. The piezoelectric torsion vibrator has a piezoelectric torsional vibrator that excites torsional vibration, and a rod-shaped Langevin type longitudinal vibrator that is formed by bonding a metal material to the end face of the piezoelectric vertical vibrator and excites stretching vibration in the central axis direction. A piezoelectric longitudinal-torsional composite vibrator in which the Langevin type longitudinal vibrator is inserted, and a rotor that is pressed against one end side of the piezoelectric longitudinal-torsional composite vibrator, and the rotor is configured to perform the stretching vibration and the torsional vibration. An ultrasonic motor characterized in that the torsional vibration is converted into rotational motion about the central axis of the rotor.