JPH0336772A - Ultrasonic oscillator - Google Patents

Abstract

PURPOSE:To prevent lowering of oscillation generating efficiency even if the oscillation mode of a body coupled to an ultrasonic oscillator is coincident with the oscillation mode of the ultrasonic oscillator by fixing an annular piezoelectric element for radial oscillation to a metal cylinder to construct the ultrasonic oscillator and forming a coupled ember consisting of the ultrasonic oscillator and the body to be oscillated. CONSTITUTION:A piezoelectric element 1 for radial oscillation is formed in annular shape. The outer peripheral surface of one end of a metal cylinder 2 and the inner peripheral surface of the piezoelectric element 1 are brought in close contact with and fixed to each other. When high frequency power is supplied to the piezoelectric element 1, alternating radial stress is generated. If the frequency of the high frequency power is coincident with the resonant frequency of the longitudinal primary oscillation mode of the mechanical oscillating system constructed by the piezoelectric element 1 and the metal cylinder 2, longitudinal oscillation amplitude is made maximum. The piezoelectric element 1 is disposed at the point where the radial stress is maximum to efficiently generate the longitudinal oscillation of the metal cylinder 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a piezoelectric type ultrasonic vibrator that is an ultrasonic vibration generation source.

[Prior Art] FIG. 6(a) is a front view showing a normal Langevin type ultrasonic transducer, (4a) and (4b) are cylindrical piezoelectric elements that vibrate in the axial direction, and (5a) and (5b) are metal cylinders, which are stacked in the axial direction and fixed to each other with an adhesive or the like. In the above configuration, the piezoelectric elements (4a) and (4b) are two stacked members, but the function of the piezoelectric elements may be as a single member, and depending on the method of supplying power to them, etc. It is divided into multiple pieces.

In the ultrasonic transducer configured as above, a piezoelectric element (
When high frequency power is supplied to 4a) and 4b, alternating stress is generated in the axial direction of the piezoelectric elements 4a and 4b (vertical direction of the vibrator). And piezoelectric element (4a)
.

When the frequency of high-frequency power is superimposed on the resonance frequency of the vertical-order vibration mode of the mechanical vibration system composed of (4b) and metal cylinders (5a) and (5b), the amplitude of the vertical vibration becomes maximum. .

FIGS. 6(b) and 6(c) show the longitudinal stress and longitudinal displacement of the ultrasonic transducer in this resonant state. As is clear from these figures, the cylindrical structure serving as the ultrasonic vibrator has vibration displacements in opposite phases at both ends thereof. That is,
When the vibrator is extended, the upper end is displaced upward and the lower end is displaced downward, and when the vibrator is contracted, the upper end is displaced downward and the lower end is displaced upward.

In this way, since the piezoelectric elements (4a) and (4b) are elements that generate force, they are arranged at the center where the longitudinal stress is maximum.

[Problems to be Solved by the Invention] In the conventional ultrasonic vibrator as described above, when coupled to an object that transmits longitudinal vibration, it is difficult to match the vibration mode of the object to be coupled with the vibration mode of the ultrasonic transducer. When manufacturing an object to be coupled, complicated calculations and experience are required to match its natural vibration mode with the vibration mode of the ultrasonic transducer. That is, as shown in FIG. 7(a), piezoelectric elements (4a) and (4b) and a metal cylinder (
5a) and (5b), a metal cylinder (3
), the vibration mode of the entire system is displaced and (b
), (c) As shown in the figure, a piezoelectric element (4a),
There was a problem in that the position (4b) was shifted from the point of maximum longitudinal stress, resulting in poor vibration generation efficiency.

This invention was made to solve the above-mentioned problem, and the vibration generation efficiency does not decrease even if the vibration mode of the object coupled to the ultrasonic vibrator matches the vibration mode of the ultrasonic vibrator. The purpose is to obtain an ultrasonic transducer.

[Means for Solving the Problems] The ultrasonic vibrator according to the present invention has an end portion of a metal cylinder on the inner peripheral surface of a piezoelectric element that is formed in an annular shape and vibrates in the radial direction when supplied with high-frequency power. The outer circumferential surface of the holder is tightly attached to the holder.

[Function] When the radial vibration generated in the annular piezoelectric element in this invention is propagated to the metal cylinder, it becomes an axial vibration of the metal cylinder.

[Embodiment] FIG. 1(a) is a perspective view showing the configuration of an ultrasonic transducer according to an embodiment of the present invention, in which (1) is a piezoelectric element that vibrates in the radial direction and is formed in an annular shape. .

(2) is a metal cylinder, and the outer circumferential surface of one end of the metal cylinder (2) and the inner circumferential surface of the piezoelectric element (1) are closely fixed. Note that FIG. 1(b) is a perspective view showing the vibration direction of the piezoelectric element (1).

Next, the operation of the ultrasonic transducer configured as described above will be explained. When high frequency power is supplied to the piezoelectric element (1) in FIG. 2(a), alternating stress is generated in the radial direction. When the frequency of the high-frequency power is superimposed on the resonance frequency of the vertical-order vibration mode of the mechanical vibration system composed of the piezoelectric element (1) and the metal cylinder (2), the vibration amplitude in the vertical direction becomes maximum. FIGS. 2(b) and 2(c) are diagrams showing the radial stress and longitudinal displacement of the metal cylinder (2) during the vibration state described above,
As is clear from this diagram, the piezoelectric element (1) is placed at the point of maximum radial stress and can efficiently generate longitudinal vibration in the metal cylinder (2).

FIG. 3(a) is a front view of a metal cylinder (3) having a longitudinal vibration mode different from the resonance frequency of the ultrasonic transducer according to the present invention, combined with the piezoelectric element (1) and metal cylinder (2>). FIGS. 3(b) and 3(c) are diagrams showing the radial stress and longitudinal displacement obtained at each point in the axial direction of these bonded bodies, respectively.

As is clear from these diagrams, the longitudinal vibration mode of the ultrasonic vibrator itself and the longitudinal vibration mode of the above-mentioned combined body change, and the maximum point position d of negative direction stress moves, but the piezoelectric element (1)
The radial stress always has a maximum value at the position where the radial stress is placed, and the longitudinal displacement also takes a value in accordance with the change in the radial stress.

In the above embodiment, the case where there is one piezoelectric element (L) was explained, but as shown in Fig. 4, two annular piezoelectric elements (1) are fixed to both ends of a metal cylinder (2). Even in this case, the maximum stress point in the radial direction becomes the placement point of the piezoelectric element (1), and the displacement in the vertical direction also takes a value according to the change in the radial stress. Piezoelectric element (1
) is fixed to one end of the metal cylinder (2), and the other piezoelectric element (
Even in the case where the metal cylinders (2) and (3) are connected by fixing the piezoelectric element (1) to an arbitrary position on the metal cylinder (3), the maximum stress point in the radial direction is the placement of the piezoelectric element (1) at two locations. Three locations are obtained: the point and the lower end of the metal cylinder (3). Moreover, the displacement in the longitudinal direction also takes on a value according to the change in the radial stress.

In this way, when an ultrasonic vibrator is constructed by fixing a plurality of annular piezoelectric elements (1) to a metal cylinder, ultrasonic vibrations with stronger energy than a single piezoelectric element (1) can generate. The same effect as in the above embodiment is obtained.

[Effects of the Invention] As described above, according to the present invention, an annular piezoelectric element that vibrates in the radial direction is fixed to a metal cylinder to constitute an ultrasonic vibrator. By forming a combined body with the vibrating body, even if the vibration mode of the ultrasonic vibrator itself changes, it is possible to efficiently generate ultrasonic vibrations.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view showing the configuration of an ultrasonic transducer according to an embodiment of the present invention, FIG. 1(b) is a perspective view showing the vibration direction of the piezoelectric element shown in FIG. 2(a), and FIG. ,(b). (c) is a diagram showing the ultrasonic transducer according to the present invention and its characteristics of radial stress and longitudinal displacement; FIG. 3(a);
(b) and (c) are diagrams showing the combined body of the ultrasonic transducer and metal cylinder according to the present invention, and its characteristics of radial stress and longitudinal displacement; c) and FIGS. 5(a), (b), and (c) are other embodiments according to the present invention and diagrams for explaining the same, and FIGS. 6(a) and (b). (c) is a diagram showing an example of the configuration of a conventional ultrasonic transducer and its characteristics; FIGS. 7(a), (b), and 2(c) are diagrams showing an example of the configuration of another conventional example and its characteristics. It is. In the figure, (1) is piezoelectric transmission and reception, (2), (3)
is a metal cylinder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] An ultrasonic vibrator in which the inner circumferential surface of a piezoelectric element formed in an annular shape and vibrating in the radial direction and the outer circumferential surface of the end of a metal cylinder are closely attached and fixed.