JPH03118780A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To enable stable high efficiency operation by adjusting the voltage so that the oscillation speed of the other oscillation may be maximum when the displacement of one oscillation of two-way oscillation becomes maximum and that the speed may be the shifting speed at which a driving part abuts on the position of nearly the loop of both oscillation amplitude. CONSTITUTION:When the first piezoelectric body 22 is oscillated by applying the AC voltage of frequency f to a positive electrode 41, a first ultrasonic oscillator 20 is excited. When the second piezoelectric body 30 is oscillated by applying the AC voltage of frequency f/2 to a positive electrode 42 at the same time, a second ultrasonic oscillator 40 is excited. When a driving part 26 formed at the end being the loop of the oscillation of the second ultrasonic oscillator 40 at this time, the first ultrasonic oscillator 20 receives driving force in the direction determined by the phase of two-way oscillation. And if the application voltage is adjusted to set speed so that the first ultrasonic oscillator 20 may be at the position of the loop of the second oscillator 40 after oscillation of one cycle, the first ultrasonic oscillator 20 receives the driving force again.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a standing wave type ultrasonic motor.

[Prior art] The operating principle of a standing wave type ultrasonic motor is that a moving element is brought into contact with a predetermined pressure against an ultrasonic vibrator that is excited into an approximately elliptical motion, and each mass point moving approximately in an elliptical manner is connected to the moving element. The movable element is driven by the frictional force.

Since the standing wave type ultrasonic vibrator can easily be configured to achieve highly efficient vibration, the standing wave type motor has the advantage of higher efficiency and larger output than the traveling wave type motor.

The ultrasonic vibrator used in conventional standing wave motors generates unidirectional vibration at the contact surface between the elastic body and the exciting body in order to excite approximately elliptical motion with high efficiency. At the contact surface between the rotor and the mover, approximately elliptical motion is obtained by using a mechanical resonance system having a natural vibration mode that performs elliptical vibration. Such an ultrasonic motor has been proposed in Japanese Patent Application No. 63-234450 and Japanese Patent Application No. 1-46866.

However, since these ultrasonic motors excite vibrations in two directions in a single elastic body, there are large limitations on their shape and dimensions. Furthermore, there is a drawback that the two-way vibrations are likely to be coupled due to structural imperfections.

Therefore, Japanese Patent Application No. 62-292730 proposes an ultrasonic motor that divides the elastic body in each vibration direction and excites each part independently. A conventional example is shown in FIG.

Here, the holder 100 has a cylindrical shape with a bottom, and is fixed to a fixed position member (not shown) such as a machine frame. A rotating shaft 120 is slidably fitted to the bottom of the holder 100, and a nut 1 is screwed onto one end of the rotating shaft 120.
A preloaded coil spring 150 and a thrust bearing 160 are inserted between 40 and the bottom surface of the holder 100, so that the rotating shaft 120 is always urged toward the nut 140 in a rotatable state. There is.

The fixed vibration member 180 is fixed concentrically to the holder 100, has a through hole 200 into which the rotating shaft 120 is loosely fitted, and has a boss portion 220 fixed to the holder 100 with a square cross section. , a rectangular flat plate part 240 that protrudes from four sides of the outer periphery of the boss part 220 by the same length in all directions, and is located in a plane including the axis, and one corner of the outer peripheral side of this flat plate part 240 is interconnected. It is composed of an annular pressure contact portion 260. Further, 280 and 400 are piezoelectric elements, 320 is a movable vibration member, 360 is a flat plate portion, and 380 is an annular pressure contact portion.

[Problem 8 to be solved by the invention] In order to perform stable operation of the above-mentioned ultrasonic motor, the entire vibration surface of the ultrasonic motor must be excited in the same phase. However, in reality, unnecessary vibrations other than excitation vibrations tend to occur on the vibrating surface, making stable and highly efficient operation difficult.

The present invention has been made to solve the above-mentioned problems, and since it is not necessary to excite the entire vibration surface of the ultrasonic motor in the same phase and unnecessary vibrations are less likely to occur, the shape of the ultrasonic vibrator can be changed. The objective is to obtain an ultrasonic motor that has a large degree of freedom and is capable of stable, highly efficient operation.

[Means for Solving the Problems] In order to achieve this object, the ultrasonic motor of the present invention includes a plurality of ultrasonic vibrators that relatively excite substantially elliptical vibrations by combining vibrations in two substantially orthogonal directions. In the standing wave type ultrasonic motor, a first electromechanical transducer is attached,
a first elastic body to which at least bending vibration is excited;
The second elastic body is provided with an electromechanical transducer element attached thereto, and is provided with a second elastic body that is excited at least in longitudinal vibration, and a driver formed at a position approximately at the antinode of one of the elastic bodies.

Further, one of the elastic bodies has a rectangular flat plate shape, and the other elastic body is a rail.

[Operation] In the ultrasonic motor of the present invention having the above configuration, bending vibration is excited in one elastic body, and longitudinal vibration is excited in the other elastic body. At this time, when the vibration displacement of one of the two-directional vibrations is maximum, the vibration speed of the other vibration is maximum, and the driving voltage is adjusted so that the movement speed is such that the two vibrations come into contact at approximately the antinode position. ing. As a result, the two elastic bodies perform relative motion.

C Embodiment] Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings.

1 to 3 show the ultrasonic motor of this embodiment.

The first ultrasonic vibrator 20 used in the ultrasonic motor 100 of this embodiment has a rectangular flat plate shape and a first piezoelectric body 22 attached to an elastic body 21 made of brass material. The first piezoelectric body 22 is polarized in the thickness direction and vibrates in a longitudinal vibration mode, and as a result, longitudinal vibration is excited in the elastic body 21.

The first ultrasonic vibrator 20 is mounted on a yoke 2 by a holder 24 at a support portion 23 formed at the vibration node.
5. Furthermore, a drive section 26 is formed at the end of the elastic body 21.

The yoke 25 is supported at both ends by roller bearings 27, and is press-fitted to a rail 28 made of an elastic material. The rail 28 is fixed to a base 30 with bolts 29. Furthermore, a second piezoelectric body 31 is attached to the rail 28, forming a second ultrasonic transducer 40. The second piezoelectric body 31 is polarized in the thickness direction and vibrates in a longitudinal vibration mode, so that a standing wave of bending vibration is excited in the rail 28.

Further, a positive electrode 41 is attached to the first piezoelectric body 22,
A positive electrode 42 is attached to the second piezoelectric body 31,
The front rail 2B is grounded as a common electrode.

The first ultrasonic transducer 20 is adjusted in shape and dimension so that it longitudinally vibrates in a primary mode with both free ends at a predetermined frequency f. Further, the shape and dimensions of the second ultrasonic vibrator 40 are adjusted so that it bends and vibrates at approximately a frequency of f/2. Since each of these two vibrators only needs to vibrate resonantly with a single vibration, the degree of freedom in their shape and size is large.

The operation of the ultrasonic motor 100 configured as described above will be explained below with reference to FIG. 2.

First, when an AC voltage of frequency f is applied to the positive electrode 41 to vibrate the first piezoelectric body 22, the first ultrasonic vibrator 20 exhibits a velocity distribution as shown in FIG. 2(a-1). The vibrations that it has are excited. At the same time, when an AC voltage with a frequency f/2 is applied to the positive electrode 42 to vibrate the second piezoelectric body 30, the second ultrasonic vibrator 40 has an amplitude as shown in FIG. 2 (a-2). Vibration with a distribution is excited.

At this time, when the driving part 26 formed at the end of the first ultrasonic vibrator 20, which is the antinode of the vibration, is brought into contact with the point A of the antinode of the vibration of the second ultrasonic vibrator 40. , the first ultrasonic transducer 20 receives a driving force in a direction determined by the phase of the two-way vibration. Then, when the first ultrasonic transducer 20 vibrates for one period and reaches the state shown in FIG. , when adjusting the applied voltage to set the speed, the first ultrasonic transducer 20 also receives a driving force.

In this manner, by selecting the speed determined by the frequency of the two-way vibration and the applied voltage, the first ultrasonic transducer 20 continuously receives a driving force in a predetermined direction.

Next, the structure of a rotary ultrasonic motor in which the rail 28 is annular will be explained based on FIG. 3. In this figure, each member with the same reference numeral as in FIG. 1 means the same as each component described in detail above.

The rail 28 forming the second ultrasonic transducer 40 has an annular shape and is rotatably supported by a rubber roller 43.

In the ultrasonic motor 100 configured as described above,
When the ultrasonic transducers 20 and 40 are excited, the rail 28 receives the aforementioned driving force and rotates at a constant speed.

Although the above embodiment has been explained by taking the first-order mode of longitudinal vibration as an example, it is also possible to use higher-order modes.

Furthermore, although the above embodiment uses a piezoelectric material as the driving element of the vibrator, it is not limited to this, and other elements that can convert electrical energy into mechanical energy, such as an electrostrictive element or a magnetostrictive element, may be used. It's okay. In addition, although an example in which the ultrasonic transducer is shaped like a flat plate has been described, the shape is not limited to a flat plate shape, and the shape is not limited to a flat plate shape.
Circular.

A cylindrical shape, a rod shape, a rectangular shape, etc. may also be used. In addition, various modifications are possible without departing from the spirit of the present invention.

[Effects of the Invention] As is clear from the detailed description above, the present invention provides an ultrasonic motor that has a large degree of freedom in the shape of the ultrasonic vibrator and that can operate stably and with high efficiency. A sonic motor can be realized.

[Brief explanation of drawings]

1 to 3 show embodiments embodying the present invention, and FIG. 1 is a side view of the ultrasonic motor of this embodiment;
FIG. 2 is a speed and amplitude distribution diagram of an ultrasonic transducer, FIG. 3 is a plan view of an embodiment of a rotary ultrasonic motor, and FIG. 4 is a side view of a conventional ultrasonic motor. In the figure, 100 is an ultrasonic motor, 20 is a first ultrasonic vibrator, 21 is an elastic body, 22 is a first piezoelectric body, 28 is a rail,
31 is a second piezoelectric body, and 40 is a second ultrasonic vibrator.

Claims (1)

[Claims] 1. In a standing wave ultrasonic motor equipped with a plurality of ultrasonic transducers that relatively excite approximately elliptical vibrations by combining vibrations in two directions that are orthogonal to each other, the first electromechanical conversion a first elastic body to which an element is attached and to which at least bending vibration is excited; a second elastic body to which a second electromechanical transducer is attached and to which at least longitudinal vibration is excited;
An ultrasonic motor comprising: an elastic body; and a driver formed at a position approximately at the antinode of vibration of either one of the elastic bodies. 2. The ultrasonic motor according to claim 1, wherein one of the elastic bodies has a rectangular flat plate shape, and the other elastic body is a rail.