JP2874174B2 - Ultrasonic transducer and ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic vibrator in which substantially elliptical vibration is excited and an ultrasonic motor using the ultrasonic vibrator.

[Prior Art] Conventionally, the above-described ultrasonic vibrator is mainly used for a standing wave type ultrasonic motor.

The operating principle of a standing wave type ultrasonic motor is as follows. It drives the mover. The standing wave type ultrasonic transducer has a merit of high efficiency and large output as compared with the traveling wave type motor, because a configuration realizing high efficiency vibration is easily obtained.

Ultrasonic transducers used in conventional standing wave motors are:
In order to excite nearly elliptical motion with high efficiency, it has a natural vibration mode that causes unidirectional vibration at the contact surface between the elastic body and the exciter, and elliptical vibration at the contact surface between the elastic body and the moving element. A substantially elliptical motion is obtained by using a mechanical resonance system.

Such an ultrasonic vibrator has been proposed by referring to the specification and drawings attached to Japanese Patent Application Nos. 63-97151 and 63-97152.

[Problems to be Solved by the Invention] Since strain is concentrated on a fixing portion for fixing the ultrasonic vibrator, it is difficult to completely fix or match impedance,
In addition, there are problems such as instability of boundary conditions in the fixed portion, and it has been difficult to perform a stable operation.

Further, since the vibration profile of the elastic body is changed by the fixing portion, it cannot be said that a desired vibration is always obtained, and it has been difficult to perform a highly efficient operation.

Therefore, a conventional ultrasonic motor using an ultrasonic vibrator cannot obtain kinetic energy with high efficiency.

The present invention has been made in order to solve the above-described problems, and has as its object to provide an ultrasonic vibrator that is stable in operation and capable of achieving high efficiency.

It is another object of the present invention to provide an ultrasonic motor having stable operation and high efficiency by suitably using the ultrasonic transducer.

[Means for Solving the Problems] To achieve the above object, an ultrasonic vibrator according to claim 1 includes: an elastic body having a first plane and a second plane substantially orthogonal to the first plane; First excitation means mounted on a first plane of the elastic body and exciting bending vibration to the elastic body; and second excitation means mounted on a second plane of the elastic body and exciting longitudinal vibration to the elastic body. At a position that is a node of a standing wave of bending vibration generated by excitation by the first excitation unit and a node of a standing wave of longitudinal vibration generated by excitation by the second excitation unit. Fixing means for fixing the elastic body.

Further, in the ultrasonic motor according to the second aspect, the mover is brought into contact with the ultrasonic transducer according to the first aspect.

[Operation] In the ultrasonic vibrator of the present invention having the above configuration, the first exciter applies bending vibration to the elastic body. At the same time, the second exciter excites longitudinal vibration in the elastic body. For the standing waves of the above two vibrations, the vibration modes are selected so that the nodes of the vibration coincide at at least one place.

Since there is no vibration displacement at the overlap of the nodes of each vibration in the elastic body, no distortion is caused by the fixing, and the vibration is not hindered.

Further, the ultrasonic motor moves the mover by the action of the vibration of the ultrasonic transducer.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 to 3 show an ultrasonic transducer according to the present embodiment. In the ultrasonic vibrator 11 of the present embodiment, a first piezoelectric body 22 for exciting bending vibration of the elastic body 21 is attached to an upper surface of an elastic body 21 having a rectangular flat plate shape. In the elastic body 21, second piezoelectric bodies 23a and 2b for exciting longitudinal vibration to the elastic body 21 are provided on a side surface substantially orthogonal to the mounting surface.
3b is installed.

The longitudinal center of the elastic body 21 is fixed by fixing bolts 24a and 24b for fixing the elastic body 21.
The other ends of the fixing bolts 24a and 24b are connected to bases 25a and 25b.
It is fixed to.

An electrode 26 is mounted on the upper surface of the first piezoelectric body 22. Also, electrodes 27a are provided on the upper surfaces of the second piezoelectric bodies 23a and 23b.
And 27b are installed. The elastic body 21 itself
The elastic body also serves as a ground electrode,
Grounded to bases 25a and 25b via a and 24b.

Further, as shown in FIG. 3, the elastic body 21 bends and vibrates in the thickness direction at a predetermined frequency f in a free mode at both ends free ends, and at the same frequency f at both ends free ends 1 in the length direction. The shape and dimensions are adjusted so as to vibrate longitudinally in the next mode.

In general, the resonance frequency of longitudinal vibration propagating in an elastic body is
It depends on the length of the elastic body. The resonance frequency of the bending vibration in the thickness direction of the elastic body depends on the length and the thickness.
Therefore, since it is easy to design the elastic body 21 as described above, details thereof are omitted.

The operation of the ultrasonic vibrator 11 configured as described above will be described below.

First, when the AC voltage having the frequency f is applied to the first piezoelectric body 22 to vibrate, the elastic body 21 resonates in a bending vibration secondary mode, and has a constant amplitude distribution as shown in FIG. 3 (c). The standing wave is excited.

Next, when an AC voltage having a frequency f is applied to the second piezoelectric bodies 23a and 23b and vibrated, the elastic body 21 vibrates in a primary longitudinal vibration mode and has an amplitude distribution as shown in FIG. 3 (b). A standing wave is excited. That is, the position fixed by the fixing bolts 24a and 24b is a node of each standing wave.

At this time, the first piezoelectric body 22 and the second piezoelectric bodies 23a and 23b
By adjusting the amplitude and phase of the voltage applied to the elastic body 21, it is possible to generate a substantially elliptical vibration of an arbitrary shape in the elastic body 21.

Next, a configuration of a linear ultrasonic motor that suitably uses the above-described ultrasonic transducer 11 will be described with reference to FIG. In this figure, the members denoted by the same reference numerals as those in FIGS. 1 to 3 are the same as the respective constituent members described in detail above.

In the linear ultrasonic motor 31, the ultrasonic vibrator 11 is fixed to a yoke 32, and a driving unit 33 is formed at one end of the elastic body 21 of the ultrasonic vibration 11.

A mover 34 is pressed against the drive unit 33 by a rubber roller 35, and the mover 34 is supported by linear bearings 36 a and 36 b fixed to the yoke 32.

In the linear ultrasonic motor 31 configured as described above, when the ultrasonic vibrator 11 is excited, the mover 34 receives a driving force due to the substantially elliptical vibration of the elastic body 21, and an arrow A in FIG.
Move in the direction of. This driving force is generated by a frictional force between the driving section 33 formed on the elastic body 21 and the mover 34.

In the above embodiment, the longitudinal vibration primary mode and the bending vibration secondary mode have been described as examples. However, the resonance frequencies of the longitudinal vibration and the bending vibration substantially coincide with each other. If matched, it is possible to use higher order modes.

Further, in the above embodiment, the piezoelectric element was used as the driving element of the vibrator, but the invention is not limited to this. Other elements that can convert electric energy into mechanical energy, such as an electrostrictive element and a magnetostrictive element, are used. Is also good. Further, in the embodiment, the example in which the shape of the ultrasonic transducer is a flat plate has been described, but if the vibration is excited in the longitudinal direction and the bending vibration in the axial direction and substantially elliptical motion is generated, the shape is a flat plate The shape is not limited, and for example, a rod shape, a square shape, and the like can be considered. 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 above description, according to the present invention, the ultrasonic vibration is generated at a position where the nodes of the two-way vibration coincide with each other and the displacement of the elastic body in the excitation direction is extremely small. Since the transducer is fixed, it is possible to provide an ultrasonic transducer which is stable in operation and capable of changing with high efficiency.

In addition, the ultrasonic motor of the present invention has stable operation and high efficiency by suitably using the above-mentioned ultrasonic vibrator.

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a diagram showing the upper surface of an ultrasonic vibrator to which the present invention is applied, and FIG. 2 is the above ultrasonic vibrator. FIG. 3 is an explanatory view of a vibration mode of the ultrasonic transducer,
FIG. 4 is a sectional view of an embodiment of a linear ultrasonic motor using the ultrasonic transducer. In the figure, 21 is an elastic body, 22 is a first piezoelectric body corresponding to the first excitation means, 23a and 23b are second piezoelectric bodies corresponding to the second excitation means, 24a and 24b are fixing bolts corresponding to the fixing means, 34 is a mover.

Claims (2)

(57) [Claims] An elastic body having a first plane and a second plane substantially orthogonal to the first plane; and an elastic body mounted on the first plane of the elastic body for exciting bending vibration to the elastic body. A first exciting means, a second exciting means mounted on a second plane of the elastic body, and exciting a longitudinal vibration to the elastic body; a standing wave of bending vibration generated by the excitation by the first exciting means And a fixing means for fixing the elastic body at a position serving as a node of a standing wave of longitudinal vibration generated by excitation by the second excitation means. Child. 2. An ultrasonic motor, wherein a movable element is brought into contact with the ultrasonic vibrator according to claim 1.