JP2691617B2 - Ultrasonic motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a so-called ultrasonic motor using ultrasonic vibration of a piezoelectric vibrator used in OA equipment and the like, and particularly to a vertical-torsion vibrator type having a simple structure. It relates to an ultrasonic motor.

[Prior Art] FIG. 8 is a perspective view of a structural example of a vertical-torsion composite oscillator 101 used in a conventional vertical-torsion oscillator ultrasonic motor. The child 103 is joined via a metal hollow cylinder 104, and the metal hollow cylinders 105 and 106 are further joined to both sides thereof.

FIG. 9 is a perspective view showing a structural example of an ultrasonic motor configured by using the vertical-torsion composite oscillator 101 shown in FIG. Axis 107
A rotor 109 rotatably supported by a bearing 108 is pressed against the end face of the vertical-torsion composite oscillator 101 by a coil spring 110 and a nut 111.

FIG. 10 shows an example of the structure of the piezoelectric torsional oscillator shown in FIG. 8, and the ring-shaped piezoelectric torsional oscillator 102 is constructed by joining four fan-shaped piezoelectric ceramic plates 112. Each fan-shaped piezoelectric ceramic plate 112 is polarized in the direction 12a of the fan's chord, as shown in FIG.
Apply electrodes to the upper and lower surfaces of the fan-shaped piezoelectric ceramics plate 112,
When a DC voltage is applied between the upper and lower electrodes, sliding distortion parallel to the plate thickness is generated in the fan-shaped piezoelectric ceramics plate.

As shown in FIG. 10, when four fan-shaped piezoelectric ceramic plates 112 are joined in a ring shape, the slip strains generated in each fan-shaped piezoelectric ceramic plate 112 are combined and the upper and lower surfaces of the rings are It becomes a twisting distortion that can be twisted.

When the conventional piezoelectric torsion oscillator shown in FIG. 10 is manufactured, first, as shown in FIG. 12, a piezoelectric ceramic plate 113 polarized in the width direction is processed into a fan-shaped piezoelectric ceramic plate by ultrasonic machining. A fan-shaped piezoelectric ceramic plate 112 punched out and polarized in the direction of the chord of the fan as shown in FIG.
And make four disks by adhering four of them together, or
As shown in FIG. 13A, a regular square pole 115 whose polarization direction is a diagonal line is cut out from a block 114 of piezoelectric ceramics polarized in the thickness direction, as shown in FIG. As shown in Fig. 13 (c), four regular prisms
After laminating 115 so as to form a loop with a closed polarization direction and adhering them, and polishing the outer circumference and the inner circumference into a hollow cylinder as shown in FIG. 13 (d), as shown in FIG. 13 (e). It is formed by cutting into a ring shape.

FIG. 14 shows an example of the structure of a conventional piezoelectric vertical oscillator 103,
Electrodes are applied to both sides, and a voltage is applied to the piezoelectric ceramics ring 116 polarized in the thickness direction to obtain vibration in the thickness direction (called longitudinal vibration).

In order to obtain a large vibration amplitude with a low applied voltage, a plurality of thin piezoelectric ceramic rings 116 'may be laminated to form the piezoelectric vertical vibrator 103' as shown in FIG.

[Problems to be Solved by the Invention] In the conventional piezoelectric torsional oscillator 102 shown in FIG. 10, since a plurality of piezoelectric ceramics are bonded together, there is a large variation in characteristics due to bonding. Also,
10 and 11. As shown in FIGS. 12 and 13, the process for obtaining the piezoelectric torsional vibrator 102 is complicated and the cost is very expensive. Further, when trying to obtain the torsional vibration and the longitudinal vibration at the same time, the piezoelectric torsional vibrator 102 shown in FIG. 10 and the piezoelectric longitudinal vibrator 103 shown in FIG. 14 or 15 are bonded together. However, there is a problem in that variations in characteristics due to bonding and a cost for bonding are required.

Therefore, the technical problem of the present invention is to eliminate the above-mentioned drawbacks of the conventional piezoelectric torsion oscillator and the longitudinal-twisted composite oscillator, to make the processing easy, without the bonding step, and with little variation in the piezoelectric torsion oscillator. And to provide an ultrasonic motor using the same.

Further, another technical problem of the present invention is to provide an ultrasonic motor using a piezoelectric longitudinal-torsion composite oscillator in which the resonance frequency of the torsional oscillator and the resonance frequency of the longitudinal oscillator can be easily matched. .

[Means for Solving the Problems] According to the present invention, a plurality of oblique electrodes are formed on the outer peripheral surface of a piezoelectric ceramic hollow cylinder so as to extend in a direction intersecting the central axis and be parallel to each other. Piezoelectric torsional vibrators that are polarized by multiple diagonal electrodes and apply an AC voltage to excite torsional vibrations at both ends, and a metal material is bonded to the end faces of the piezoelectric longitudinal vibrators, and stretch vibrations occur in the central axis direction. A piezoelectric vertical-torsion composite oscillator having a rod-shaped Langevin-type vertical oscillator that excites, and the Langevin-type vertical oscillator inserted in the piezoelectric torsion oscillator, and one end side of the piezoelectric vertical-torsion composite oscillator. And a rotor that is pressed into contact with the rotor. The rotor converts the stretching vibration and the torsional vibration into rotational motion around the central axis of the nuclear rotor, thereby obtaining an ultrasonic motor.

[Operation] The ultrasonic motor of the present invention includes a piezoelectric longitudinal-torsion composite oscillator and a rotor.

The piezoelectric longitudinal-torsion composite oscillator has a piezoelectric torsion oscillator and a rod-shaped Langevin type longitudinal oscillator, and the Langevin type longitudinal oscillator is inserted in this piezoelectric torsion oscillator.

A piezoelectric torsion oscillator forms a plurality of diagonal electrodes on the outer peripheral surface of a piezoelectric ceramic hollow cylinder so as to intersect with the central axis and in parallel with each other, polarizes by the plurality of diagonal electrodes, applies an AC voltage, and twists vibration at both ends. Excite.

The rod-shaped Langevin type vertical vibrator is configured by joining a piezoelectric torsional vibrator and a metal material to the end surface of the piezoelectric vertical vibrator, and excites stretching vibration in the central axis direction.

The rotor is pressed against one end of the piezoelectric longitudinal-torsion composite oscillator, and converts the longitudinal vibration and the torsional vibration into rotational motion about the central axis of the rotor.

Embodiment An embodiment of the present invention will be described below in detail 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 will be described later, the piezoelectric torsion oscillator 21
A rotor vertically rotatably supported by a bearing 8 at one end of a piezoelectric vertical-torsion composite oscillator 21, 27 formed by inserting a piezoelectric vertical oscillator 27 having a length substantially equal to that of the rotor. 9 is pressure-contacted via a spring 10.

The piezoelectric vertical vibrator 27 can be supported and fixed by the support frame 30 which is located at the node of resonance of torsional vibration in the piezoelectric torsional vibrator, so that stable support can be achieved.

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

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

In FIG. 2 (b), the broken line arrow indicates the direction of polarization when polarization treatment is performed using such an interdigital electrode, and FIGS. 2 (c) and 2 (d) show FIG. The state of distortion that occurs when a DC voltage is applied to the piezoelectric ceramic plate 17 that has been polarized as shown in b) is shown, and the solid line arrow shows the direction of the electric field.

As shown in FIG. 2 (c), when the voltage polarity is the same as the voltage polarity at the time of polarization, extension strain occurs in the polarization direction,
On the other hand, when the polarity of the voltage is opposite to the polarity of the voltage at the time of polarization as shown in FIG. 2 (d), contraction distortion occurs in the direction of polarization.

FIG. 3 shows a state of strain generated on the outer peripheral surface of the piezoelectric ceramic hollow column 20 when both end faces of the piezoelectric ceramic hollow column 20 are twisted as shown by the arrows in the figure. Expansion and contraction occur in the direction of an angle of 45 ° with respect to the axial direction, and in the direction of the arrow indicated by the broken line, and contraction strain occurs in the direction perpendicular to this and the direction indicated by the dashed-dotted arrow.

Therefore, on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 shown in FIG. 3, the first and second interdigitating electrodes as shown in FIG. 2 are provided, and as shown in FIG. It is formed so as to form an angle of 45 ° with respect to the length direction of the hollow cylinder 20, and polarization treatment is performed using the first and second interdigital electrodes, and when a DC voltage is applied to the same interdigital electrode, If the polarity of the voltage is the same as the polarity of the voltage when polarized,
The piezoelectric ceramic hollow cylinder 20 twists in one direction, and twists in the opposite direction when the polarity of the voltage is opposite to the polarity of the voltage during polarization.

FIG. 4 is a perspective view showing an example of the piezoelectric torsion oscillator used in the ultrasonic motor according to the embodiment of the present invention. In this figure, a plurality of piezoelectric torsion oscillators 21 are formed on the outer peripheral surface of the central portion of the piezoelectric ceramic hollow cylinder 20 'so as to form an angle of 45 ° with respect to the length direction of the piezoelectric ceramic hollow cylinder 20'. Of the first and second diagonal electrodes 22 and 23. The first and second diagonal electrodes 22 and 23 are alternately formed in the direction orthogonal to the lengthwise direction of these electrodes and spaced apart so as to be parallel to each other. The first and second diagonal electrodes 22 and 23 are provided on both ends of the peripheral surface of the piezoelectric ceramic hollow cylinder 20 'along the circumferential direction, and the first and second common electrodes 22' and 23 'are provided. To form a torsional oscillator 21.

In FIG. 4, the first and second common electrodes 22 'and
A DC high voltage is applied across 23 'to perform polarization treatment in a direction orthogonal to the longitudinal direction of the first and second oblique electrodes 22 and 23 of the piezoelectric ceramic hollow cylinder 20', and then the piezoelectric torsion oscillator. When an AC voltage having a frequency equal to the resonance frequency of the portion 21 is applied, the piezoelectric ceramic hollow cylinder 20 'resonates so that both ends are twisted.

FIG. 5 is a perspective view showing one structural example of a Langevin type vertical vibrator 27 used in the ultrasonic motor according to the embodiment of the present invention. In this figure, the Langevin type vertical oscillator 27
Is joined to both ends of the cylindrical piezoelectric vertical oscillator 103, one end of each of the metal cylinders 25, 25 having the same diameter as the piezoelectric vertical oscillator 103,
Further, at the other end of each of the metal cylinders 25, 25, there is a metal cylinder 25 ', 25' for adjusting resonance frequency having a diameter larger than that of the metal cylinder
It is configured by joining each.

The metal column 25 and the metal column 25 'for adjusting the resonance frequency may be integrally formed.

This Langevin type vertical vibrator is widely used in ultrasonic cleaning machines and ultrasonic processing machines. In particular, the diameter in the vicinity of both ends of the Langevin type oscillator is made larger than the diameter of the central portion in order to make the resonance frequency of the torsion oscillator 21 the same as that of the torsion oscillator.

In the ultrasonic motor of the present embodiment, if the diameter of both ends of the vibrator is made thicker than that of the central part, the vibration frequency becomes lower than that of a Langevin type vibrator having a uniform diameter of the same length due to the effect of additional mass. We are using.

FIG. 6 shows a piezoelectric longitudinal axis used in the harmonic wave motor of the present invention.
It is a perspective view showing an example of a torsion oscillator.

In this figure, the Langevin type vertical vibrator 27 is arranged in the hollow portion of the piezoelectric torsional vibrator 21, and the vibration node at the central portion in the lengthwise direction of the piezoelectric vibrator and the center in the longitudinal direction of the vertical vibrator. The vibration nodes of the section are joined by using a thin plate ring 28. In this case, the vibration state of the piezoelectric longitudinal-torsional oscillator is
When expressed in terms of amplitude, it becomes as shown in FIG. That is, for both torsional vibration and longitudinal vibration, the piezoelectric longitudinal-torsional vibrator 2
It vibrates so that the central part of 1,27 becomes a node of vibration.

As can be seen from FIG. 7 (a), a piezoelectric longitudinal-torsion oscillator
Both ends of 21,27 are twisted in opposite directions. As for the longitudinal vibration, if the frequency of the applied voltage is the same as the resonance frequency of the torsion as shown in FIG. 7B, the piezoelectric longitudinal-
Both ends of the torsional oscillators 21 and 27 are synchronized with torsional resonance,
Stretching vibration (longitudinal vibration) in the length direction. Therefore, when the rotor rotatably supported at the ends of the piezoelectric longitudinal-torsional vibration-incorporated 21, 27 is pressed with a certain elasticity, the longitudinal vibrator produces buoyancy.
Torsional oscillators apply torque to the rotor in each half cycle to rotate the rotor. In this case, if the phase of the applied voltage of torsional vibration or the applied voltage of longitudinal vibration is changed by 180 °, the direction of rotation is reversed.

[Effects of the Invention] As described above, according to the present invention, in the piezoelectric torsional vibrator for an ultrasonic motor, a hollow piezoelectric ceramic that can be easily manufactured by a press molding technique that is generally applied. Piezoelectric torsional vibrators can be obtained by using a cylinder and printing electrodes on these outer peripheral surfaces, which is also a general technique, so that it is easy to manufacture and there is no variation in characteristics due to the bonding process or complicated processing process. A small number of piezoelectric torsion oscillators can be obtained.

Further, according to the present invention, a Langevin type vertical oscillator, which has been widely used conventionally as a piezoelectric vertical oscillator, is used.
Further, by constructing the diameter in the vicinity of both ends to be thicker than the diameter in the central portion, it is possible to make the resonance frequency substantially the same as the length of the torsional vibrator, and to make the resonance frequency substantially equal, and to increase the efficiency of the ultrasonic motor. Can be realized.

[Brief description of the 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), (b), (c), and (d) show polarization and voltage using an interdigital electrode. FIG. 3 is an explanatory diagram of a strain generation state when applying a voltage, FIG. 3 is an explanatory diagram of a strain generation state when the piezoelectric ceramic hollow cylinder is twisted, and FIG. 4 is a piezoelectric torsional vibration according to an embodiment of the present invention. FIG. 5 is a perspective view showing the structure of a child, FIG. 5 is a perspective view showing an example of the structure of a pipe-shaped Langevin type vertical vibrator used in the ultrasonic motor of the present invention, and FIG. 6 is a piezoelectric vertical according to an embodiment of the present invention. FIG. 7 (a) is a partially cutaway perspective view showing the structure of the torsional oscillator, FIG. 7 (a) is a diagram showing the relative magnitude of torsional displacement of the piezoelectric longitudinal-torsion composite oscillator of FIG. 6, FIG. 7 (b). 6 is a diagram showing the relative magnitude of extensional displacement of the piezoelectric longitudinal-torsion composite oscillator of FIG. 6, and FIG. 8 is a conventional longitudinal-torsional Langevin. Perspective view showing a structure of a vibrator, 9
FIG. 1 is a perspective view showing the structure of a conventional vertical-torsion ultrasonic motor, FIG. 10 is a perspective view showing an example of the structure of a conventional torsion oscillator, and FIGS. 11 and 12 are conventional torsion oscillators. Explanatory drawing of an example of a manufacturing process, FIG. 13 (a), (b), (c),
(D) and (e) are explanatory views of another example of the manufacturing process of the conventional torsional vibrator, FIG. 14 is a perspective view showing one structural example of the conventional longitudinal vibrator, and FIG. 15 is a conventional longitudinal vibration. It is a perspective view which shows the other structural example of a child. In the figure, 8 ... Bearing, 9 ... Rotor, 10 ... Spring, 17 ... Piezoceramic plate, 18, 19 ... Finger electrodes, 1
8 ', 19' ... Connecting electrode, 20,20 '... Piezoelectric ceramic hollow cylinder, 21 ... Piezoelectric vertical oscillator, 27 ... Piezoelectric torsion composite oscillator, 22,23 ... Slanting electrode, 22', 23 ′ …… Common electrode, 27
...... Langevin type vertical oscillator, 25 …… Metal cylinder, 25 ′…
… Metal cylinder for resonance frequency adjustment, 28… Thin plate ring, 30… Support frame, 101… Piezoelectric vertical-torsion composite oscillator, 1
02 …… Piezoelectric torsion oscillator, 103,103 ′ …… Piezoelectric vertical oscillator, 1
04,105,106 …… Metal hollow cylinder, 107 …… Shaft, 108 …… Bearing, 109 …… Rotor, 110 …… Spring, 111 …… Nut, 112 …… Fan piezoelectric ceramic plate, 113,114 …… Piezoelectric ceramic plate, 115… … Piezoelectric ceramic plate prism, 1
16,116 ′ …… Piezoelectric ceramic ring.

Claims (1)

(57) [Claims] 1. A plurality of oblique electrodes are formed on an outer peripheral surface of a piezoelectric ceramic hollow cylinder so as to extend in a direction intersecting a central axis and are parallel to each other, and are polarized by the plurality of oblique electrodes to generate an AC voltage. Piezoelectric torsional vibrator that excites torsional vibrations at both ends by applying a force, and a rod-shaped Langevin-type longitudinal vibrator that is formed by bonding a metal material to the end faces of the piezoelectric longitudinal vibrators And a piezoelectric vertical-torsion composite oscillator in which the Langevin type vertical oscillator is inserted in the piezoelectric torsion oscillator, and a rotor pressed against one end of the piezoelectric vertical-torsion composite oscillator. The rotor is an ultrasonic motor, wherein the stretching vibration and the torsional vibration are converted into rotational movement about a central axis of the rotor.