JPH0736709B2 - Bolt tightening ultrasonic elliptical transducer for piezoelectric motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric ultrasonic motor, and more particularly to an improvement of an ultrasonic elliptical vibrator that constitutes a stator thereof.

[Conventional technology]

The present inventor has made many proposals regarding a piezoelectric ultrasonic motor and an ultrasonic elliptical vibrator for driving the piezoelectric ultrasonic motor. Among them, a motor using a cantilever ultrasonic ellipsoidal vibrator shows excellent characteristics in practical use, so we have filed more than 20 applications including Japanese Patent Application No. 59-172429. This cantilever ultrasonic motor has a feature of being capable of outputting a low speed and a large torque with high efficiency, and thus has high practical value. Since a sine wave voltage that matches the resonance frequency of the ultrasonic elliptical oscillator is applied to drive the motor, a high voltage is required to obtain a high output. With the motors we have proposed so far, at least regardless of the size of the motor,
The disadvantage is that it requires a voltage of about 50 V, and even if a voltage of less than 50 V is applied, an effective output cannot be obtained, and low voltage driving cannot be performed.

[Problems to be solved by the invention]

The present invention solves the drawback that a piezoelectric motor using a conventional cantilever ultrasonic elliptical vibrator cannot drive at a low voltage, and is a highly practical piezoelectric that can obtain a large output at a low voltage drive. An object is to provide an ultrasonic elliptical oscillator used for a motor.

[Means for solving problems]

Most of the ultrasonic transducers currently in practical use are oscillators that generate longitudinal vibration, called bolted Langevin type transducers. The role of the bolt in the Langevin type vibrator is to actuate the vibration generated at the same time as tightening the piezoelectric element to the resonator made of a metal rod. The vibration strength of the resonator is determined by the cross-sectional area of the round bar, but in general, the round bar is thicker than the bolt, and therefore the strength is too strong. For this reason, the strength of the round bar is adjusted by forming the end of the bar into a hollow cylinder. However, in the ultrasonic elliptical oscillator that is the subject of the present invention, instead of directly tightening the longitudinal oscillator, the torsional connector is fixedly supported and passed through the disk of the torsional connector,
Tighten the vertical vibrator and piezoelectric element. Therefore, the oscillator strength is determined by the strength of the bending mode of the disk,
Since the bending mode has a small strength, it is sufficient to use a thinner bolt to perform strength matching than in the case of the Langevin vibrator.

The vibration strength of the torsional connector is almost determined by the thickness and diameter of the disk, and the details are determined by the groove width, beam thickness, beam height, etc. On the other hand, the resonance frequency is generally designed to be around 40 KHz. Therefore, it can be considered that the vibration intensity is determined by the diameter of the disk of the torsional connector. Thick bolts are used for disks with a large diameter, and thin bolts are used for disks with a small diameter.

[Examples] Hereinafter, the present invention will be described with reference to Examples.

Example 1 FIG. 1 is a structural explanatory view of a piezoelectric vibrator using a cantilever ultrasonic elliptical pendulum showing an example of the present invention.

Since the structure itself is not different from the structure of the conventional ultrasonic motor of this type, detailed description thereof will be omitted. The different point is that the thickness of the cap bolt 8 is selected to be the thickness corresponding to the diameter of the torsion connector disk 7, and therefore the difference from the conventional example cannot be illustrated. In other words, the configuration is Pb (ZrT
i) The positive electrodes of the O ₃ -based piezoelectric ceramics 1 and 2 are opposed to each other,
After passing through the cap bolt 8 set on the aluminum washer 5 over the terminal plates 3 and 4, and further stacking the aluminum disc 6, the tip of the cap bolt is fitted into the screw hole of the torsion connector 7 and tightened to form an ultra-high wave. An elliptical oscillator was constructed.

By using this oscillator as a stator, a support bolt of the rotor 9 was screwed into an end face, that is, a screw hole at the center of the upper surface of the beam portion of the torsional connector 7, thereby exerting a crimping force on the rotor. A sine wave voltage having a resonance frequency of about 40 WHz was applied to the lead wires of the terminal plates 3 and 4, the rotor 9 was rotated, and the motor was operated.

Here, the operating characteristics of the motor were investigated when various diameters of the piezoelectric ceramic oscillator, the bolt, and the torsional connector were changed.

The following table shows the above-mentioned measurement results, that is, the influence of the thickness of the tightening bolts on various sizes of the ceramic oscillator and the torsional connector forming the oscillator for the cantilever ultrasonic ellipse. Among the three types of bolts in the table, ○ indicates that the rotation is smooth at low voltage, which is the optimum condition, △ indicates the usable limit, and × indicates that it is not suitable for use. ing.

The ceramic diameter in the table is the diameter of the piezoelectric vibrator.
In the above table, the ratio (D2 / D1) of the diameter (D2) of the bolt to the diameter (D1) of the piezoelectric vibrator is summarized as follows.

As is clear from the table of measurement results, when the diameter (D1) of the piezoelectric vibrator is as small as 25 mm and the diameter (D2) of the bolt is as large as 8 mm, that is, D2 / D1 is 1 If it is / 3, it is a limit to drive at a voltage lower than 50 V (△
Yes), if the diameter of the bolt becomes larger than that, that is, if D2 / D1 becomes larger than 1/3, a voltage of 50 volts or more is required as in the conventional case.

On the other hand, when the diameter (D1) of the piezoelectric vibrator is 50 mm as large as the diameter of the bolt (D2) as small as 6 mm, that is, when D2 / D1 is 1/8, low piezoelectric drive is achieved. Is the limit of rotation torque (with △), and when D2 / D1 becomes smaller than that, that is, when the diameter (D1) of the piezoelectric vibrator is 35 mm and the diameter (D2) of the bolt is 4 mm (D2 / If the diameter (D1) of the piezoelectric vibrator is 50 mm and the diameter of the bolt (D2) is 4 mm (D2 / D1 = 1/13), sufficient rotation torque will be obtained. I can't get it. For this reason D2
By regulating / D1 within the range of 1/3 to 1/8, it is possible to obtain a low voltage and sufficient rotation torque.

〔The invention's effect〕

As described above, in the present invention, the piezoelectric vibrator and the torsional connector are tightened with bolts, and in the ultrasonic elliptical vibrator integrated, the thickness of the tightening bolt is 1/3 to 1 of the diameter of the piezoelectric vibrator. In the range of / 8, we selected a thickness that matches the oscillator strength of the torsional connector. Therefore, the atommittance can be maximized. Therefore, when it is used for the stator of the ultrasonic motor, it is possible to apply a lower voltage and obtain a larger rotation output. There is an effect that it can be applied to a stator of an ultrasonic motor driven by a low voltage.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a bolted ultrasonic elliptical vibrator for a piezoelectric motor according to the present invention. 1,2 …… Piezoelectric ceramic resonator, 3,4 …… Terminal plate, 5 ……
Wash bolt washers, 6 ... Aluminum disc, 7 ...
… Torsion connector, 8 …… Cap bolt, 9 …… Rotor, 10 …… Output shaft.

Claims (1)

[Claims] 1. A longitudinal vibration generated by a piezoelectric vibrator is converted into a torsional vibration by a torsional connector, ultrasonic elliptical vibration is generated at an end face of the torsional connector, and a rotor is rotated by the elliptical vibration. An acoustic wave elliptical oscillator, wherein the piezoelectric oscillator is formed of a disk-shaped ceramic body, and at least the side of the torsional connector facing the piezoelectric oscillator is in the shape of a disk, and from the center of the piezoelectric oscillator. In the one in which the piezoelectric vibrator and the torsional connector are integrated by tightening with one bolt inserted through the central portion of the torsional connector, the diameter is smaller than 1/3 of the diameter of the piezoelectric oscillator, and is smaller than 1/8. A bolted ultrasonic ellipsoidal oscillator for a piezoelectric motor, characterized in that the bolt having a larger diameter is used.