JP2729829B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a so-called ultrasonic motor using ultrasonic vibration of a piezoelectric vibrator used for office automation equipment and the like, and particularly to a longitudinal-torsional vibrator type having a simple structure. It relates to an ultrasonic motor.

[Prior Art] FIG. 9 is a perspective view of a structural example of a longitudinal-torsional combined vibrator 101 used in a conventional longitudinal-torsional vibrator type ultrasonic motor. The piezoelectric torsional vibrator 102 and the piezoelectric longitudinal vibrator 103 are joined via the metal cylinder 4, and the metal cylinders 5 and 6 are joined on both sides thereof. In this case, a metal cylinder can be used instead of the metal cylinder. FIG. 10 is a perspective view of a structural example of an ultrasonic motor constituted by using the longitudinal-torsion composite vibrator 101 shown in FIG.
At the center of one end of 101 is formed a hole reaching at least a vibration node. A shaft 7 having a diameter smaller than the diameter of the hole is inserted into the hole and fixed to the composite vibrator 101 at the contact point. Further, a rotor 9 rotatably supported by a bearing 8 is pressed against an end face of the longitudinal-torsion composite vibrator 101 by a coil spring 10 and a nut 11. FIG. 11 shows the ninth
This is an example of the structure of the piezoelectric torsional vibrator shown in the figure, in which a disc-shaped piezoelectric torsional vibrator 102 has four fan-shaped piezoelectric ceramic plates 112.
Are joined. Each of the fan-shaped piezoelectric ceramic plates 112 is polarized in the direction of the chord of the fan as shown in FIG. 12, electrodes are provided on the upper and lower surfaces of the fan-shaped piezoelectric ceramic plate, and a DC voltage is applied between the upper and lower electrodes. Is applied, a sliding distortion parallel to the thickness of the fan-shaped piezoelectric ceramic plate is generated. Four fan-shaped piezoelectric ceramic plates 11
When 2 is joined in a disk shape, the slip distortion generated in each of the sector-shaped piezoelectric ceramic plates is combined, resulting in a torsional distortion in which the upper and lower surfaces of the disk are twisted.

In the conventional piezoelectric torsion vibrator shown in FIG. 11, first, as shown in FIG. 13, a fan-shaped piezoelectric ceramics plate is punched out from a piezoelectric ceramics plate 113 which is polarized in an axial direction by ultrasonic processing. Create a fan-shaped piezoelectric ceramics plate 112 polarized in the direction of the chord of the fan as shown in the figure,
Four of them are bonded to each other to form a disk shape, or as shown in FIG. 14, a piezoelectric ceramic block 114 polarized in the thickness direction is used to form a square prism 115 whose polarization direction is a diagonal direction. Are cut out, and four square prisms 115 are overlapped and bonded so as to form a loop having a closed polarization direction, the outer periphery is polished into a pipe shape, and then cut into a disk shape.

FIG. 15 shows an example of the structure of a conventional piezoelectric longitudinal vibrator, in which electrodes are applied to both surfaces and a voltage is applied to a piezoelectric ceramic disk 103 polarized in the thickness direction to obtain vibration in the thickness direction. . In order to obtain a large vibration amplitude at a low applied voltage, a plurality of thin piezoelectric ceramic disks
In some cases, it is configured as in 3 '.

[Problem to be Solved by the Invention] In the conventional piezoelectric torsional vibrator 102 shown in FIG. 11, since a plurality of piezoelectric ceramics are bonded, the characteristic variation due to the bonding is large. Also,
As shown in FIG. 12, FIG. 13 and FIG. 14, the processing for obtaining the piezoelectric torsional vibrator 102 was complicated and very costly.

The technical problem of the present invention is to eliminate the drawbacks of the ultrasonic motor using the conventional piezoelectric torsional vibrator described above, to use a piezoelectric torsional vibrator that is easy to process, has no bonding process, and has little variation. An object of the present invention is to provide an ultrasonic motor.

Another technical problem of the present invention is that, by using a hollow piezoelectric vertical-torsion composite vibrator, two rotors are pressed against both ends of the piezoelectric vertical-torsion composite vibrator by a shaft penetrating the hollow portion. An object of the present invention is to provide a two-rotor ultrasonic motor.

[Means for Solving the Problems] According to the present invention, a piezoelectric torsional vibrator having a first cross-sectional shape orthogonal to a central axis and performing torsional vibration around the central axis, and one end of the torsional vibrator A second end substantially opposite to the first cross-sectional shape.
And a third section having one end joined to the other end of the piezoelectric torsional vibrator and having one end joined to the other end of the piezoelectric torsional vibrator, the third section being substantially equal to the first section shape. A first metal material having a shape, and a second metal material having one end joined to the other end of the piezoelectric longitudinal vibrator and having a fourth cross-sectional shape substantially equal to the first cross-sectional shape. A longitudinal-torsional composite vibrator, and a rotor pressed against at least one of the other ends of the first and second metal materials, wherein the piezoelectric torsional vibrator has a piezoelectric ceramic having an outer peripheral surface; An ultrasonic motor having a plurality of first oblique electrodes and a plurality of second oblique electrodes alternately arranged on the outer peripheral surface in a direction intersecting with the central axis of the piezoelectric ceramic is obtained. Can be

[Operation] The piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor according to the present invention comprises a first and a second piezoelectric vibrator, which are formed on the outer peripheral surface of a piezoelectric ceramic cylinder, preferably in the direction of 45 ° with respect to the longitudinal direction of the piezoelectric ceramic. By applying two interdigital electrodes to form two terminals, and then using the two terminals to polarize the piezoelectric ceramic cylindrical pipe, the polarization direction is perpendicular to the length direction of the first and second interdigital electrodes. Direction.

When a voltage is applied to the two terminals in this state, if the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, stretching strain occurs in the direction of polarization, and the polarity of the voltage is opposite to the polarity of the voltage at the time of polarization. In such a case, shrinkage distortion occurs in the direction of polarization. When an elongation or contraction strain is generated in the polarization direction, a contraction or elongation strain is generated in the direction perpendicular to the polarization direction, respectively.

As a result, torsional displacement occurs in the piezoelectric ceramic cylinder. In the piezoelectric ceramic cylinder, torsional displacement similarly occurs in a piezoelectric ceramic cylinder having a hollow portion.

One end of such a piezoelectric torsional vibrator and a conventional piezoelectric longitudinal vibrator that expands and contracts in the vertical direction are aligned, and one end of a metal material is joined to the other end, respectively. Longitudinal-torsional composite vibration, which is a combination of longitudinal vibration and longitudinal vibration, that is, a Langevin-type longitudinal vibration in which one end performs an elliptical vibration in a plane along an axis.
Form a torsional composite vibrator. When a rotor is pressed against at least one end of the composite vibrator, the longitudinal-torsional composite vibration at the other end of the pressed metal material is converted into a rotational motion of the rotor.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view showing a structure of an ultrasonic motor according to a first embodiment of the present invention, wherein a piezoelectric torsional vibrator 1 shown in FIG. 4 and a piezoelectric longitudinal vibration shown in FIG. In addition, a metal cylinder 5 and 6 are joined on both sides thereof to form a Langevin type vertical-torsional vibrator, and one end face of the Langevin type vertical-torsional vibrator is applied to one end face in the same manner as in FIG. With axis 7
The rotor 9 is fixed to a vibration node of the Langevin type vibrator, and is rotatably supported by a bearing 8. The rotor 9 is pressed against one end face of the Langevin type longitudinal-torsional vibrator by a nut 11 via a spring 10. Have been.

FIG. 2 is an explanatory diagram of the operation principle of the piezoelectric torsional vibrator used in the ultrasonic motor according to the first embodiment of the present invention. Second
In FIG. 1A, a plurality of electrodes 18 and 19 crossing each other are formed on one surface of a piezoelectric ceramic plate 17, and are alternately connected to common electrodes 18 'and 19', respectively. Are formed. In FIG. 2 (b), broken arrows indicate the directions of polarization when the polarization processing is performed using such first and second interdigital electrodes, and FIGS. 2 (c) and (d). ) Shows the state of distortion generated when a DC voltage is applied to the piezoelectric ceramic plate 17 which has been subjected to the polarization treatment as shown in FIG. 2 (b), and the solid line arrows show the direction of the electric field. As can be seen from FIGS. 2 (c) and 2 (d), when the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, stretching strain occurs in the direction of the polarization, and the polarity of the voltage is the same as the polarity of the voltage at the time of polarization. In the opposite case, shrinkage distortion occurs in the direction of polarization. FIG. 3 shows a state of distortion occurring on the outer peripheral surface of the cylinder 20 when both end surfaces of the cylinder 20 are twisted as indicated by arrows in the figure, and shows an angle of 45 ° with respect to the axial direction of the cylinder 20. , And in the direction of the torsional dashed arrow, contraction occurs in the direction of the dashed-dotted arrow perpendicular to this direction.

Accordingly, the first and second interdigital electrodes as shown in FIG. 2 are provided on the outer peripheral surface of the piezoelectric ceramic cylinder so that the direction of the interdigital finger is at an angle of 45 ° to the length direction of the piezoelectric ceramic cylinder. Then, a polarization process is performed using the first and second interdigital electrodes, and a DC voltage is applied to the same interdigital electrode. When the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, the piezoelectric ceramic cylinder is formed. It twists in one direction and twists in the opposite direction if the polarity of the voltage is opposite to the polarity of the voltage during polarization. Also, when the piezoelectric ceramics are cylindrical, similar torsional vibrations are generated.

FIG. 4 is a perspective view showing the structure of one embodiment of the piezoelectric torsional vibrator used in the ultrasonic motor according to the first embodiment of the present invention. A plurality of first and second oblique electrodes 22 and 23 intersecting each other are formed on the surface at an angle of 45 ° with respect to the length direction, and the first and second common electrodes 22 ′ are respectively formed.
And 23 '. In FIG. 4, after applying a DC high voltage between the common electrodes 22 'and 23' to perform polarization processing, and applying an AC voltage having a frequency equal to the resonance frequency of the torsional vibrator, the ring-shaped piezoelectric ceramic 20 can be obtained. ′
Resonates so that both ends are twisted.

Embodiment 2 FIG. 5 is a perspective view of a structural example of an ultrasonic motor according to a second embodiment of the present invention, in which a shaft 26 passes through a hollow portion of a pipe-shaped Langevin type piezoelectric longitudinal-torsional composite vibrator 2. Let the axis 26
Rotors 9, 9 'rotatably supported by bearings 8, 8' at both ends of the nuts 11, 11 'via springs 10, 10'.
And is pressed against the end face of the Langevin type vertical-torsional vibrator.

FIG. 6 is a perspective view showing the structure of a pipe-shaped Langevin type piezoelectric vertical-torsion composite vibrator 2 used in an ultrasonic motor according to a second embodiment of the present invention. The piezoelectric torsional vibrator 1 shown in FIG. 4 and the conventional piezoelectric longitudinal vibrator 103 shown in FIG.
Are bonded by an adhesive such as an epoxy resin, and metal pipes 5 'and 6' are joined to both sides of the adhesive with a similar adhesive. As shown in the figure, the position of the piezoelectric torsional vibrator 1 is such that the center of the torsional vibrator is the Langevin type vibrator 2.
Is arranged at a position approximately 1/4 of the total length l of In this case, the vibration state of the Langevin type vibrator 2 is as shown in FIG. That is, with respect to torsional vibration, the center of the torsional vibrator is located at approximately 1/4 of the total length l of the Langevin-type vibrator, and therefore, approximately 1/4 of the total length l of the Langevin-type vibrator. Resonates in a vibration mode such that the position becomes a node of vibration. As can be seen from FIG. 7, both ends of the Langevin type vibrator 2 are twisted in the same direction around the central axis of the vibrator. As for the longitudinal vibration, if the frequency of the applied voltage is the same as the torsional resonance frequency, both ends of the Langevin type vibrator 2 expand and contract in the central axis direction of the vibrator in synchronization with the torsional resonance. do. Therefore, when the phases of the two applied voltages are adjusted so that the extension vibration becomes maximum at the timing when the amplitude of the torsional vibration becomes large, both surfaces of the Langevin type vertical-torsional vibrator oscillate elliptically in a plane along the central axis. . In this case, the phase of one applied voltage is 180
゜ When changed, the direction of the elliptical vibration is reversed.

FIG. 8 is a perspective view showing another example of the structure of the pipe-shaped Langevin type piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor according to the second embodiment of the present invention. A torsion oscillator 1 and a pipe-like bolt 28 whose outer periphery is threaded around the hollow portion of the piezoelectric longitudinal oscillator 103 shown in FIG.
And threaded metal pipes 5 ″ and 6 ″ which are screwed to the bolts on the inner circumferences on both sides thereof. Also in FIG. 8, when the torsional vibrator is arranged at a position which is approximately / 4 of the total length 1 of the Langevin type vibrator 3, the torsional vibrator vibrates on the same principle as the Langevin vibrator in FIG.

As described above, in the ultrasonic motor shown in FIG. 5, the end faces of the Langevin type longitudinal-torsion composite vibrator are twisted in the same direction, so that the two rotors 9, 9 'rotate in the same direction.

In addition, the Langevin type longitudinal-torsional composite vibrator can support and fix 1/4 position from both ends, which are the nodes of resonance of torsional vibration, with ring-shaped support frames 27, 27 ', and stable support is achieved. It becomes possible.

[Effects of the Invention] As described above, according to the present invention, a piezoelectric ceramic which can be easily manufactured by a press molding technique generally applied as a piezoelectric vertical vibrator for an ultrasonic motor and a torsional vibrator. By applying electrode printing, which is also a common technique, to these outer peripheral surfaces using a cylinder, the piezoelectric torsional vibrator and the piezoelectric longitudinal vibrator can be obtained as an integral shape, making it easy to manufacture, making the bonding process and complicated An ultrasonic motor with less variation in characteristics due to various processing steps can be obtained. Further, a similar ultrasonic motor can be obtained by using a piezoelectric ceramic cylinder instead of a piezoelectric ceramic cylinder.

Further, according to the present invention, it is possible to realize an ultrasonic motor of a system in which a shaft is penetrated through a hollow portion of a pipe-shaped piezoelectric longitudinal-torsion composite vibrator and simultaneously rotates two rotors, and also drives an object wider than between rotors. be able to. As described above, since the ultrasonic motor of the present invention uses this piezoelectric longitudinal-torsion composite vibrator, an ultrasonic motor having a simple structure and a small variation in characteristics can be obtained, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of an ultrasonic motor according to a first embodiment of the present invention, and FIG. 2 is an explanatory diagram of a state of occurrence of distortion when polarization and voltage are applied using interdigital electrodes. , Third
FIG. 4 is an explanatory view of a state in which distortion occurs when the columnar elastic body is twisted. FIG. 4 is a perspective view showing a piezoelectric torsional composite vibrator of the ultrasonic motor according to the first embodiment of the present invention. The figure is a perspective view showing the structure of the ultrasonic motor according to the second embodiment of the present invention,
FIG. 6 is a perspective view showing the structure of a pipe-shaped Langevin composite vibrator used in an ultrasonic motor according to a second embodiment of the present invention, and FIG. 7 is a view showing the displacement of the pipe-shaped Langevin composite vibrator shown in FIG. FIG. 8 is a perspective view showing another example of the structure of a pipe-shaped Langevin type piezoelectric longitudinal-torsional composite vibrator used in the ultrasonic motor according to the second embodiment of the present invention. FIG. 10 is a perspective view showing the structure of a conventional longitudinal-torsional Langevin type vibrator, FIG. 10 is a perspective view showing the structure of a conventional vertical-torsional ultrasonic motor, and FIG. 11 is a diagram showing the structure of a conventional torsional vibrator. FIG. 12 and FIG. 13 are explanatory views of a manufacturing process of a conventional torsional vibrator, FIG. 14 is an explanatory diagram of a manufacturing process of a conventional torsional vibrator, and FIG. FIG. 16 is a perspective view showing a structure, and FIG. 16 is a perspective view showing another structure of a conventional longitudinal vibrator. In the figure, 1: a piezoelectric longitudinal-torsional composite oscillator, 2: a piezoelectric torsional oscillator,
3: Piezoelectric longitudinal vibrator, 4, 5, 5 ', 5 ", 6, 6', 6": metal cylinder,
7: Shaft, 8: Bearing, 9: Rotor, 10: Spring, 11: Nut, 17: Piezoceramic thin plate, 18, 19: Cross finger electrode, 1
8 ', 19': common electrode, 20: columnar elastic body, 20 ': ring-shaped piezoelectric ceramic, 22, 23: interdigital electrode for torsional vibrator,
22 ', 23': common electrode, 24:25, cross finger electrode for longitudinal oscillator, 2
6: shaft, 27, 27 ': support frame, 28: pipe-shaped bolt, 101: piezoelectric vertical-torsion composite vibrator, 102: piezoelectric torsional vibrator, 103: piezoelectric vertical vibrator, 112: fan-type piezoelectric ceramics plate, 113, 114: piezoelectric ceramic plate, 115: piezoelectric ceramic plate prism, 116: piezoelectric ceramic disk.

Claims (1)

(57) [Claims] 1. A piezoelectric torsional vibrator having a first cross-sectional shape orthogonal to a central axis and performing torsional vibration around the central axis, and one end of the piezoelectric torsional vibrator is arranged to face one end of the torsional vibrator. A piezoelectric longitudinal vibrator having a second cross-sectional shape substantially equal to the first cross-sectional shape and performing expansion and contraction vibration in the central axis direction, and one end connected to the other end of the piezoelectric torsional vibrator; A first metal member having a third sectional shape substantially equal to the first sectional shape, and a fourth metal material having one end joined to the other end of the piezoelectric longitudinal vibrator and substantially equal to the first sectional shape. A piezoelectric element comprising: a ranchevan-type longitudinal-torsional composite vibrator having a second metal material having a cross-sectional shape; and a rotor pressed against at least one of the other ends of the first and second metal materials. The torsional vibrator includes a piezoelectric ceramic having an outer peripheral surface, Ultrasonic motor and having a plurality of first oblique electrode and the plurality of second oblique electrodes arranged alternately in a direction intersecting the central axis of the piezoelectric ceramic on the peripheral surface.