JPH033679A - Ultrasonic motor apparatus - Google Patents

Abstract

PURPOSE:To simplify an apparatus and the like by applying an alternating current to either one of a pair of vibrators. CONSTITUTION:An ultrasonic motor is composed of a platelike piezoelectric vibrator 10, electrodes 11a and 12a attached to one side faces of the vibrator 10, a movable extraction unit 20, a switch mechanism 14, and a single-phase power source 15. the vibrator 10 is so formed as to have a length and a thickness that a longitudinal wave generated by applying a voltage to the electrodes 11a, 12a coincides with a resonance frequency of a bending wave generated therewith. The electrodes 11a, 12a are selectively excited to forward or reversely turn the moving direction of the unit 20.

Description

[Detailed Description of the Invention] [Industrial Field of Application] "The present invention relates to an ultrasonic motor device, and particularly relates to an ultrasonic motor device that is driven and controlled by a single-phase power source." [Prior Art] Conventionally, ultrasonic motor devices Ultrasonic motor devices that use vibration can be classified based on the type of vibration generated in an elastic vibrating body: standing wave type ultrasonic motor devices that use standing waves, and traveling wave type ultrasonic motor devices that use traveling waves. It is roughly divided into two types.

Among the above, standing wave type ultrasonic motor devices include:
A flat plate-shaped ultrasonic motor device is known that excites a single bending standing wave in an elastic vibrating body using a single-phase power supply and utilizes the driving force directed toward the nodes of this standing wave via a motion extractor. (For example, Japanese Patent Application No. 62-1 filed by the same applicant as the present application)
37395).

In addition, the elastic vibrator has two independent vibration modes on each side: longitudinal vibration (vibration spread in the length direction of the elastic vibrator) and natural vibration with a vibration component perpendicular to one surface of the elastic vibrator. A flat-plate ultrasonic motor device is known that generates elliptical motion on the surface of an elastic vibrating body by exciting it with a power source (two-phase power source), transmits this elliptical motion to a motion extracting body, and uses it as driving force. It is being This type of flat ultrasonic motor device driven by a two-phase power source excites two vibration modes with a temporal phase difference.
By switching the rotational direction of the elliptical motion generated on the surface of the elastic vibrating body, the direction of motion of the motion extracting body can be switched between forward and reverse directions.

[Problem to be solved by the invention]

Among the conventional technologies, the planar ultrasonic motor device using a single bending standing wave generated by a single-phase power supply has an extremely simple structure, but at the same frequency, This method has a control problem in that the direction of motion of the motion extractor that is in contact with the elastic vibrator cannot be reversed.

In addition, a flat ultrasonic motor device driven by a two-phase power supply has two
Since different types of independent vibration modes are used, an excitation source is required for each vibration mode, and compared to an ultrasonic motor device driven by a single-phase power source, both the ultrasonic motor device itself and the power source are less complex. There was a problem that it was unavoidable.

The present invention has been made in view of these problems of the conventional technology, and its purpose is to control the direction of motion of a motion extractor by driving a single-phase power source, and to generate ultrasonic waves. The present invention aims to provide an ultrasonic motor device in which the structure of the motor device main body and the power source are simplified.

That is, a plate-shaped ultrasonic motor device that has the simplicity of an ultrasonic motor device driven by a single-phase power source and the controllability that allows forward and reverse rotation like an ultrasonic motor device driven by a two-phase power source, The aim is to achieve this goal.

[Means to resolve the issue]

“In order to achieve the above object, the ultrasonic motor device of the present invention includes a plate-shaped piezoelectric vibrator and a pair of electrode elements that generate longitudinal waves and bending waves of a certain wavelength on one surface of this elastic vibrator. , one surface of the piezoelectric vibration is formed with a length and thickness that match the resonance frequencies of the longitudinal wave and the bending wave, and the electrode element is provided at a position corresponding to the node of the longitudinal wave, and at least one motion extractor is provided. [Operation] The resonant frequency of one longitudinal vibration (vibration in the spreading direction) of a plate-shaped elastic vibrator and the vibration component in the vertical direction (bending vibration) on the surface of the elastic vibrator. When the resonance frequency of the natural vibration mode of the elastic vibration body matches the resonance frequency, when longitudinal vibration is excited, the natural vibration with a vibration component perpendicular to the surface of the elastic vibrator is also excited, and these two vibrations are generally coupled. Are known.

In other words, when a plate-shaped elastic vibrating body is an ideal plane, there is a coupling between mutually independent vibration modes: longitudinal vibration and a natural vibration mode with a vibration component perpendicular to the longitudinal vibration. does not occur. However, an actual elastic vibrating body has an asymmetry with respect to a plane horizontal to longitudinal vibration, and due to this asymmetry, when longitudinal vibration is excited, a natural vibration with a vibration component in a direction perpendicular to the longitudinal vibration is excited. It is known that these compounds bond easily.

The ultrasonic motor device according to the present invention utilizes the above-mentioned effect, and by applying an alternating current to either one of the pair of electrodes, it controls the asymmetry of the piezoelectric vibrator and also controls the piezoelectric vibrator. Excite longitudinal vibration. This longitudinal vibration excites bending vibration, and by combining these two vibrations, elliptical motion is generated on the surface of the piezoelectric vibrator. This elliptical motion is transmitted to the motion extractor, and the motion extractor is driven in a fixed direction.

By selectively applying an alternating current to either one of the pair of electrodes, the phase of the coupling between the longitudinal vibration and bending vibration generated in the piezoelectric vibrator changes, and the driving direction of the motion extractor can be controlled. It will be done.

That is, by switching the excitation position of the plate-shaped piezoelectric vibrator, a 180 degree phase difference is created in the combined phase of longitudinal vibration and bending vibration, and the direction of rotation of the elliptical motion generated on the surface of the piezoelectric vibrator is reversed. You can switch as follows.

[Principle of the present invention]

In the case of simple bending vibration, as shown in FIG. 9, if both ends are open, the nodes of vibration are distributed symmetrically with respect to the center of the plate-shaped vibrating body 10, and each point has a direction of the arrow pointing to the nearby node. The driving force is generated. The driving force is therefore distributed symmetrically about the center and is independent of the position of the excitation source.

On the other hand, in the case of a combination of longitudinal vibration and bending vibration, if both ends of the vibrating body are open, the bending vibration is considered to be symmetrical with respect to the center, so two cases are possible: a case where the longitudinal vibration is symmetrical and a case where it is asymmetrical. .

In Figure 9, the displacement in the X direction (spreading direction) is x,
If the displacement in the direction (direction perpendicular to the surface) is Y, the above two cases are expressed as the following equations.

(1) X=a cos(klx) cos(Wt),
Y=b cos(k2x) 5in(Wt+d)(
2) X=a cos(klx) cos(Wt),
Y=b cos(k2x) 5in(Wt+d)(k
l: Wave number of longitudinal wave k2: Wave number of bending wave W: Angular frequency)
If the longitudinal wave in equation (1) is symmetrical, the point X on the plate-like vibrating body and -
It can be seen that it performs elliptical vibration rotating in the same direction as the point X.

That is, unlike the case of simple bending vibration described above, it is possible to generate a driving force in the same direction at the point X and the point -X.

If the longitudinal vibration in equation (2) is asymmetric, then the point X on the flat plate and the point
It performs elliptical vibration in the opposite direction to the point , and the driving force is in the opposite direction.

In addition, since each point in equations (1) and (2) is an elliptical vibration, the driving forces on the front and back sides of the plate-shaped vibrating body 100 are opposite to each other, which is also different from the case of simple bending vibration.

In view of the above, an ultrasonic motor device driven by a single-phase power source and capable of forward and reverse rotation can be configured as follows.

■ When the driving forces at points X and -X are in the same direction (Fig. 10 (
a)) Assuming that a longitudinal wave has one wavelength on the vibrating body 10, excitation sources A and B are placed at nodes of the longitudinal wave, for example, as shown in FIG. 10(a).

Assume that the driving force shown in FIG. 10(a) is obtained by the excitation source A. Next, considering the case of excitation by excitation source B, this is nothing but a case in which the excitation of excitation source A is rotated by 180 degrees with respect to the center line O, and the excitation of excitation source B causes the first
It can be seen that a driving force in the opposite direction to that in Figure 0 (a) can be obtained.

That is, when the length of the vibrating body 10 is an integral multiple of the wavelength of the longitudinal wave, if the longitudinal wave excitation sources are installed at centrally symmetrical positions on the same plane of the vibrating body 10, they can be selectively driven one by one. By controlling the combined phase of the longitudinal vibration and bending vibration generated in the vibrating body, it is possible to control the forward and reverse directions of the driving force.

(2) The driving forces at the points X and -X are in opposite directions (Fig. 10, etc.) In this case, forward and reverse control is possible with the configuration shown in Fig. 10 (b). That is, assuming that a longitudinal wave has a wavelength of 1.5 on the vibrating body 10, its excitation requires, for example, the first
As shown in Figure 0 (b), the excitation source A is placed at the node of the longitudinal wave that occurs to the left of the center line 0, and the node of the longitudinal wave that occurs to the right of the center line O on the surface facing the excitation source A is placed. Excitation source B is located at
Place. It is assumed that the driving force shown in FIG. 10 is obtained by the excitation source A. Next, considering the case of excitation by excitation source B, the phase of the longitudinal wave is the same as in the case of excitation by excitation source A, but the phase of the bending wave component is different by 180 degrees. A driving force in the opposite direction to that shown in FIG. 6(b) is obtained.

In other words, the length of the vibrating body 10 is the wavelength of the longitudinal wave (n+1.A
) times (n: any positive integer), the vibrating body 100
By installing longitudinal wave excitation sources on each of the opposing surfaces, by selectively driving them one by one, the coupling phase of the longitudinal vibration and bending vibration generated in the vibrating body can be controlled.
This means that the forward and reverse directions of the driving force can be controlled.

Here, if we assume that the vibration mode with a vibration component perpendicular to the plane to be coupled to the longitudinal vibration is bending vibration, then in order to couple the bending wave to one wavelength of the longitudinal wave, the dimensions of the plate-shaped vibrating body should be calculated as follows: Just take it.

That is, t; plate thickness l; plate length α is 5 inches (α/2) cosh (α/2) + cos (cr
/2) sinh(cr/2) = root of 0, which corresponds to the order of the resonance mode of symmetrical bending vibration from the smallest order.

The resonant frequency f is is given by

The present invention is based on the above item (1), and as shown in FIG. 1, piezoelectric ceramics, etc. The electrode 11a (first electrode) and the electrode 12a (second electrode), which are excitation sources, may be bonded together.

By exciting either one of the electrodes 11a and 12a provided on the same surface of the piezoelectric vibrator 10, the asymmetry of the piezoelectric vibrator 10 is controlled.
The bending waves generated by a and 12a have a phase of 180
° Become different.

That is, when the electrode 11a is excited, a slight bending vibration component is generated due to the asymmetry of this part. - If a bending vibration component occurs each time, the piezoelectric vibrator 10 is considered to be asymmetrical, and a combination of longitudinal vibration and bending vibration occurs.

Further, considering the case where the electrode 12a is excited, the longitudinal waves have the same phase, but the situation in which the bending wave component occurs is 180° different in phase than when the electrode 11a is excited. Therefore, the combination of the longitudinal vibration and the bending vibration has a phase different by 180° from that when the electrode 11a is excited, and the direction of the elliptical motion is reversed. That is, in the case of FIG. 1, since the longitudinal wave has one wavelength, the electrode 11a.

12a generates in-phase longitudinal waves (in-phase longitudinal waves for deformation in the same direction), but the phase of the coupled bending wave is 180
°They are different.

〔Example〕

Hereinafter, the ultrasonic motor device according to the present invention will be explained in detail based on the drawings.

The right side of FIG. 1 and FIG. 2 show an embodiment of an ultrasonic motor device according to the present invention, in which an electrode 11a (hereinafter, a first electrode ) and an electrode 12a (hereinafter referred to as a second electrode) are attached. One end of a line 13a is connected to the electrode 11a, and one end of a line 13b is connected to the electrode 12a.

The other ends of these lines 13a and 13b are connected to terminals 14a and 14C of the switch mechanism 14, respectively. Route 13
C has one end connected to the piezoelectric vibrator 10 and the other end connected to the single-phase power supply 15.

The single-phase power supply 15 is connected to a switch 14C of the switch mechanism 14 by a line 13d.

Further, a motion extractor 20 is disposed on the surface of the piezoelectric vibrator 10 on the side where the electrodes 11a and 12a are provided.

The piezoelectric vibrator 10 is formed to have a length and thickness such that the resonance frequency of a longitudinal wave generated by applying a voltage to each electrode 11a and 12a and a bending wave generated by this longitudinal wave match. .

First electrode (lla) and second electrode (12a')
are arranged across the center of the longitudinal axis of the piezoelectric vibrator.

The single-phase power supply 15 applies an alternating current of a specific frequency to the first electrode 11a or the second electrode 12a by switching the switch 14c. This generates bending waves.

The motion extracting body 20 is a roller-shaped body that is positioned on the piezoelectric vibrator 10 by any means, pressurizes the vibrating body 10 by any means, and is rotatable in any direction.

To explain the operation of the above configuration, FIG. 1 shows a case where a longitudinal wave of one wavelength and a bending wave of two wavelengths are generated. These excitations will generate in-phase longitudinal waves (in-phase longitudinal waves for deformation in the same direction), but depending on which of the electrodes 11a and 12a is excited, the effect of the combined bending wave will be phase is 18
The difference will be 0°. For this reason, electrode 113.12a
By selectively exciting the piezoelectric vibrator 10, the direction of motion of the elliptical vibration generated on the surface of the piezoelectric vibrator 10 changes, and the motion extractor 2
The direction of the motion taken out to zero can be reversed forward or reverse as shown by solid line arrows and broken line arrows in FIGS. 1 and 2.

As another example, the present invention is not limited to a pair of electrodes, but may include a plurality of electrode rows. For example, FIG. 3 shows two pairs of electrodes. The parts that overlap with the numbers in Figure 1 are omitted, but the first electrode (lla, 1lb) and the second electrode (12a, 12b) are arranged alternately at symmetrical positions with respect to the center of the diaphragm. .

In this way, the electrode 11a (llb) or 12a
By selectively exciting either one of (12b), the direction of motion of the elliptical vibration generated on the surface of the piezoelectric vibrator 10 changes, and the direction of the motion taken out to the motion extractor 20 can be reversed. .

Therefore, if an object to be transported, such as a card-like object or paper sheet, is brought into contact with the movement extractor 20, the object can be transported in any direction by switching the switch 14C.

4 and 5 show other application examples of the present invention, and FIG. 4 shows a case where a roller 31 is used on the back side of the diaphragm 10 of FIG. 1 with a paper sheet 30 interposed therebetween. It shows.

Furthermore, FIG. 5 shows a device in which a convex motion extractor 32 is used in place of the roller shown in FIG. 4, and a moving plate 33 is disposed so as to be in contact with this motion extractor 32.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

It is possible to provide an ultrasonic motor device in which the current applied to the vibrator is single-phase and the vibrator drive circuit is simple.

Furthermore, by switching and applying an alternating current of a specific frequency to either one of the pair of electrodes, the direction of motion of the motion extracting body can be controlled.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing one embodiment of the present invention, FIG. 2 is a perspective view of what is shown in FIG. 1, FIG. 3 is a schematic side view showing another embodiment, and FIGS. 4 and 5 6 is a schematic side view showing an application example of the present invention, FIG. 6 is an explanatory diagram showing the driving direction by bending waves, and FIG. 7 is an explanatory diagram showing the driving direction by combined vibration of longitudinal vibration and bending vibration. 10... Vibrating body 12a, 12b... Vibrator 15... Single phase power supply 31... Roller

Claims (2)

[Claims] (1) A plate-shaped piezoelectric vibrator polarized in the thickness direction, an electrode element that generates a longitudinal wave and a bending wave of a certain wavelength in the vibrator by applying an alternating current of a specific frequency, and vibration of the bending wave. a motion extractor in contact with at least one surface of the vibrator perpendicular to the direction; The electrode element includes a common electrode disposed on one of the opposing surfaces of the vibrator, and at least a pair of electrodes disposed on the other surface of the vibrator, the pair of electrodes extending along the longitudinal axis of the vibrator. An ultrasonic motor device characterized in that the ultrasonic motor device is provided at a position corresponding to a node of the longitudinal wave generated at a symmetrical position with respect to an axial midpoint. (2) The ultrasonic motor device according to claim 1, further comprising switching means for switching and applying the alternating current of the specific frequency to either one of the pair of electrodes.