JPH0284080A - Oscillator and ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic motor equipped with high efficient and large capacity of output and that easy to control the approximately elliptic movement locus by providing to an oscillator a tabular elastic substance and the first exciting body to excite the telescopic movement inside a plane to the elastic substance and the second exciting body to excite flexural oscillation to the direction different from the first oscillating direction. CONSTITUTION:If AC voltage of frequency f1 is applied to a piezoelectric body 26 to oscillate, then a tabular elastic substance 24 will oscillate the end section in the same direction as shown in a figure (a) in the minimum order mode. The end section may also be oscillated in the reverse direction as shown in a figure (b). Then in the exciting action of flexural oscillation in the direction of thickness of an oscillator 21, when the voltage of frequency f1 is applied to a piezoelectric body 22 to oscillate as shown in the figure (a), the elastic substance oscillates the end section in the same direction as shown in a figure (c) in the secondary mode of flexural oscillation. In case the piezoelectric body 22 is oscillated as shown in the figure (b), the flexural oscillation excites the end section in the reverse direction as shown in a figure (d). Here, if both ends of (a) and (b) excite the oscillation in the same direction at the same time, approximately elliptical oscillation in the same direction will be excited at both ends of the elastic substance 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a vibrator that is excited with approximately elliptical motion and an ultrasonic motor that uses the vibrator.

[Prior art] A standing wave type ultrasonic motor brings a movable element into contact with an ultrasonic vibrator under a predetermined pressure against an ultrasonic vibrator that is excited in approximately elliptical motion, and the mass points of the stator and the movable element which are in approximately elliptical motion are brought into contact with each other. The movable element is driven by the frictional force between the movable element and the movable element.

Conventionally, as a method of exciting a standing wave of the traveling direction component of this approximately elliptical motion, there is a method using an elastic body having a shape such as a cantilever vibrator or a flat plate vibrator, and the vibration mode is also bending. Various vibrations such as vibration and shear vibration are used. These are JP-A-61-129077, Sho-62-262676 and Japanese Patent Application Sho-63-97152.
The specification and drawings attached to the application can be found in the Institute of Electrical Information and Communication Engineers, Proceedings of Lectures (A224.225), 1988.

[Problems to be Solved by the Invention] However, in the cantilever vibrator of JP-A-61-129077, the equilibrium point of vibration is at the end of the resonator, so the equilibrium point cannot be considered as a completely fixed end. There were problems in that it was difficult to excite efficiently. Also,
Even if shear vibrations are excited in a flat plate of finite length, the boundary conditions at the fixed ends become unstable, causing bending distortion in some parts, making it difficult to generate -like shear vibrations in the flat plate, and causing large-scale shear vibrations. There was a problem in that it was difficult to obtain high amplitude vibrations with high efficiency. Furthermore, in the above-mentioned Japanese Patent Application Laid-open No. 62-262676, since one type of standing wave is used, one type of standing wave is used.
The direction of movement cannot be controlled with a single motor.

In addition, the ultrasonic motor seen in the paper "Paper feeding device using flat piezoelectric vibrator (1), (U)" in the above collection uses the plane-perpendicular bending vibration mode, so the piezoelectric element There was a problem in that torsional strain was added to the structure, inhibiting vibration and reducing excitation efficiency.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a vibrator that can easily control approximately elliptical vibration and can generate large-amplitude and highly efficient vibration.

Furthermore, by appropriately utilizing the vibrator, high efficiency and
It is an object of the present invention to provide an ultrasonic motor which has a characteristic of high output and whose approximately elliptical motion trajectory can be easily controlled.

[Means for Solving the Problem] In order to achieve this object, the vibrator of the present invention includes a plate-like elastic body, at least a first excitation body that excites in-plane stretching vibration in the elastic body, and a first excitation body that excites in-plane stretching vibration in the elastic body. 1. A 2nd part that excites bending vibration in a direction different from the direction of the stretching vibration excited by the first excitation body.
The present invention is characterized by being provided with an excitation body.

Furthermore, the ultrasonic motor of the present invention is characterized in that a movable element is brought into contact with the elastic body of the vibrator.

[Operation] The elastic body in the vibrator of the present invention having the above configuration is excited by the first excitation body and the second excitation body. At this time, vibrations in two directions, stretching vibration and bending vibration, are combined in the elastic body, and approximately elliptical vibration is generated.

Further, in the ultrasonic motor of the present invention, the movable element is brought into contact with this substantially elliptical vibrating surface, whereby the movable element is rotated by frictional force.

[Example 1] Hereinafter, an example embodying the present invention will be described with reference to the drawings. FIG. 1 shows the vibrator of this embodiment. In the vibrator 21 of this embodiment, the first piezoelectric body 22 is fixed to a stand 23. Electrodes (not shown) are arranged on both sides of the first piezoelectric body 22.

Further, the first piezoelectric body 22 is polarized in the vertical direction in the figure and vibrates in the thickness direction. A plate-shaped elastic body 24 is fixed to the upper surface of the first piezoelectric body 22 with bolts 25 so as to have a symmetrical structure.

On the lower surface of the elastic body 24, second piezoelectric bodies 26a to 26 are provided.
h is installed. Electrodes (not shown) are arranged on both sides of the second piezoelectric body 26. The second piezoelectric body 26
vibrates by stretching and contracting in the direction of the arrow in Figure 2.

Furthermore, output portions 24a and 24b are provided at both ends of the elastic body 24.

The second piezoelectric bodies 26a to 26h are formed as follows. As shown in FIG. 2(a), a piezoelectric plate 26 polarized in the direction of the arrow in the figure is aligned with the polarization direction, and the elastic body 26 is
Arrange 8 pieces in a circle near the fixing part 4. Electrodes are attached to both surfaces of the piezoelectric body 2.6 manufactured in this manner, and by applying an alternating current voltage to these electrodes, stretching vibration is generated in the length direction of the piezoelectric body 2.6. Furthermore, this elastic body 24 resonates at a predetermined frequency f in the mode of bending vibration in the thickness direction. Also, with the same frequency f,
It also resonates with stretching vibrations in the length direction. At this time, the natural frequency of the stretching vibration that generally occurs in the elastic body is 2
It depends on the length of 4. Further, the natural frequency of bending vibration in the thickness direction of the plate-like elastic body 24 depends on the length and thickness. Therefore, it is easy to design the plate-shaped elastic body 24 in which both resonance frequencies match as described above. The operation of the vibrator configured as above will be explained below.

First, a case where the vibrator 2.1 excites stretching vibration will be described with reference to FIG. 3. In the figure, the shape of the plate-like elastic body 25 when the vibrator 21 is not excited is shown by a dotted line. Here, the vibration frequency due to the same vibration mode is hereinafter expressed as f. When an alternating current voltage of frequency f is applied to the piezoelectric body 26 to cause it to vibrate, the plate-like elastic body 24
For example, in the lowest order mode, the ends vibrate in the same direction as shown by the solid line in FIG. 3(a). Alternatively, the end portion may be vibrated in the opposite direction as shown by the solid line (b).

Next, the effect of exciting bending vibration in the thickness direction of the vibrator 21 will be described. When applying an alternating current voltage of frequency f1 to the piezoelectric body 22 to cause it to vibrate as shown in (a) in the above-mentioned vibration, the elastic body in the second-order bending vibration mode follows the solid line in FIG. 3(c). Excite the ends in the same direction as shown. Also, when vibrating as shown in (b),
The bending vibration is excited at the end in the opposite direction as shown by the solid line in (d). Here, when both ends of FIGS. 3(a) and 3(c) are simultaneously excited to vibrate in the same direction, substantially elliptical vibrations in the same direction are excited at both ends of the elastic body 24. Furthermore, even if both ends of FIGS. 3(b) and 3(d) utilize vibrations in opposite directions, substantially elliptical vibrations in the same direction are excited at the ends of the elastic body. The user is the first
The AC voltage applied to the electrodes on the upper and lower surfaces of the piezoelectric body 22 and the second
By adjusting the phase difference with the AC voltage applied to the electrodes on the upper and lower surfaces of the piezoelectric body 26 and the amplitude of each voltage, substantially elliptical vibration of an arbitrary shape is obtained.

Next, a fourth explanation will be given regarding the configuration of a linear ultrasonic motor that suitably utilizes the vibrator 21 excited with ultrasonic vibrations as described above.
This will be explained based on the diagram. In this figure, each member given the same reference numeral as in FIG. 2 means the same as each component described in detail above. The linear ultrasonic motor 31 is
The ultrasonic transducer 21 is fixed on the table 23, and the movable element 3 is connected to the output parts 24a and 24b of the elastic body 24.
2 is crimped. When this ultrasonic transducer 21 is excited as described above, the movable element 3
2 receives a driving force due to approximately elliptical vibration of the elastic body 24,
It moves in the direction of arrow B in the figure. This driving force is applied to the elastic body 2
4 and the movable element 32 changes.

Next, an embodiment of a rotary ultrasonic motor 41 using the present invention is shown in FIG. In the ultrasonic motor of this embodiment, a rotor 42 is disposed on the upper surface of the output section 24 of the ultrasonic vibrator 21 in a direction perpendicular to the expansion/contraction direction and in contact with the output section 24 . This rotor 42 is fixed at both ends by support rods 43 and is rotatable by a bearing (not shown). According to the rotary ultrasonic motor 41 configured as described above, when the vibrator 21 is excited with stretching vibration and bending vibration to cause a substantially elliptical motion in its peripheral portion, the rotor 42 has a substantially elliptical motion. The rotational force caused by this is transmitted and rotational movement occurs. Moreover, as described above, the approximately elliptical motion excited by the vibrator is caused by the first piezoelectric body 22 and the second piezoelectric body 24.
It can be controlled to form an arbitrary trajectory by controlling the alternating current voltage applied to and. Therefore, the rotational force generated in the rotor 42 can be freely controlled, and motor characteristics such as the rotational direction, rotational speed, and output torque can be arbitrarily adjusted. Therefore, highly efficient operation is achieved over a wide range of load fluctuations.

Although the above embodiment uses a piezoelectric material as the driving element of the vibrator, it is not limited to this, and other elements capable of converting electrical energy into mechanical energy, such as an electrostrictive element, a magnetostrictive element, etc., may be used. Good too. In addition, in the embodiment, an example in which the ultrasonic vibrator is shaped like a flat plate is explained, but stretching vibration is excited in the length direction and bending vibration is excited in the axial direction.
The shape is not limited to a flat plate shape as long as approximately elliptical motion occurs. Further, the second piezoelectric body 26 may be formed by arranging a plurality of second piezoelectric bodies 26 in a direction perpendicular to the stretching vibration, as shown in FIG. 3(b). In addition, various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, it is possible to stably excite stretching vibration and bending vibration in the vibrator, and as a result, control of approximately elliptical vibration is possible. It is possible to provide an ultrasonic transducer that can easily generate large amplitude and highly efficient vibrations. Furthermore, since the elastic body has a symmetrical structure with respect to the fixed part, it is possible to set the equilibrium point of vibration at the completely fixed end, and as a result, efficient excitation can be achieved.

Furthermore, since the excitation body is installed near the fixed part,
As a result of being able to excite the exciter without inhibiting its vibration, excitation efficiency can be increased. By suitably utilizing the ultrasonic vibrator, it is possible to provide an ultrasonic motor that has characteristics of high efficiency and large output, and can easily control a substantially elliptical motion locus.

[Brief explanation of the drawing]

1 to 5 show embodiments embodying the present invention. FIG. 1 is an exploded perspective view of a vibrator to which the present invention is applied, and FIG. 2 is an explanation of an excitation body to which the present invention is applied. Figure 3 is an explanatory diagram of the vibration shape of the elastic body of the vibrator, with the steady state shape shown by broken lines, Figure 4 is a side view of an embodiment of the linear ultrasonic motor to which the present invention is applied, and Figure 5 1 is a top view of an embodiment of a rotary ultrasonic motor; FIG. In the figure, 21 is a vibrator, 22 is a piezoelectric body, 24 is a plate-shaped elastic body, and 26 is a piezoelectric body.

Claims (4)

[Claims] 1. a plate-shaped elastic body; at least a first excitation body that excites in-plane stretching vibration in the elastic body; and a second excitation body that excites bending vibration in a direction different from the direction of the stretching vibration excited by the first excitation body. A vibrator characterized by being provided with an excitation body. 2. The vibrator according to claim 1, wherein the plate-like elastic body is fixed at at least one fixing part, and at least one of the first excitation body or the second exciter is attached to the elastic body in the vicinity of the fixation part. A vibrator characterized by being attached. 3. 3. The vibrator according to claim 1, wherein the elastic body has a symmetrical structure with respect to a fixed portion thereof. 4. An ultrasonic motor characterized in that a movable element is brought into contact with the elastic body of the vibrator according to any one of claims 1 to 3.