JPH0462518B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to fish finders, echo sounders, acoustic detectors, underground buried object searchers, ultrasonic flaw detectors, ultrasonic diagnostic devices, etc. The present invention relates to a honeycomb-shaped vibrator used in an ultrasonic transducer for the purpose of transmitting and receiving waves.

Prior Art This type of conventional piezoelectric vibrator is generally formed into a flat plate shape such as a disk shape or a square plate shape using barium titanate-based or lead zirconate-based piezoelectric ceramics, as shown in FIG. The piezoelectric ceramic body 1 had a structure in which electrodes 2 and 3 were formed on both sides in the thickness or longitudinal direction. The polarization direction P ₁ of the piezoelectric ceramic body 1 is
Usually, the direction is the same as the direction of the electric field from the electrodes 2 and 3, that is, the thickness or longitudinal direction, and the vibration mode in the thickness or longitudinal direction is utilized.

Disadvantages of the Prior Art However, in the conventional honeycomb-shaped vibrator shown in Fig. 5, in addition to the longitudinal vibration mode, a large transverse vibration mode or radial vibration mode and its harmonic vibration mode occur, resulting in large spurious waves. Moreover, when used in acoustic equipment such as fish finders or transducers for the purpose of transmitting and receiving pulsed ultrasonic waves such as ultrasonic diagnostic equipment, the mechanical quality factor Qm is high, the ultrasonic pulse width becomes long, and the distance There was a problem that the resolution deteriorated.

Purpose of the present invention The present invention solves the above-mentioned conventional problems,
It reduces the transverse vibration mode, radial vibration mode, and its harmonic vibration mode to reduce spurious vibrations, lowers the mechanical quality factor Qm under load, and shortens the ultrasonic pulse width in water or in living tissue. It is an object of the present invention to provide a honeycomb-shaped vibrator that improves distance resolution and is suitable for use in underwater acoustic equipment such as fish finders, ultrasonic diagnostic probes, and the like.

Structure of the Present Invention In order to achieve the above object, a honeycomb-shaped vibrator according to the present invention provides a piezoelectric ceramic body with a large number of holes in the thickness or in the longitudinal direction, and electrodes are formed on both sides of the thickness or in the longitudinal direction. However, it is characterized in that an electrode gap is formed between the periphery of this electrode and the outer periphery of the piezoelectric ceramic body.

Embodiment FIG. 1 is a plan view of a honeycomb-shaped vibrator according to the present invention, and FIG. 2 is a front sectional view of the same. In the figure, the same reference numerals as in FIG. 5 indicate the same components. In this embodiment, the thickness or longitudinal direction of the piezoelectric ceramic body 1 formed in the shape of a disk is
A large number of through holes 4 are formed with appropriate cross-sectional area ratios. Although the holes 4 are circular in this embodiment, they may be formed in a rectangular shape such as a square, hexagon, or octagon. In addition, piezoelectric ceramic element 1
is not limited to a disk shape, but may be a square plate shape. Furthermore, circular holes and square holes may be mixed.

Electrodes 2 and 3 are formed on both sides in the thickness or vertical direction where the holes 4 are opened. The electrodes 2 and 3 are formed to have a planar area smaller than the piezoelectric ceramic body 1 so that an annular electrode gap G ₁ is created between the entire periphery thereof and the outer periphery of the piezoelectric ceramic body 1. be.

By providing the holes 4 as described above, it is possible to impart characteristics similar to anisotropy to the honeycomb-shaped vibrator, reduce transverse vibration mode or radial vibration mode, and reduce spurious waves.

In addition, when forming the electrodes 2 and 3, they are not provided over the entire thickness of the piezoelectric ceramic body 1 or on both end faces in the longitudinal direction, but between the periphery of the electrodes 2 and 3 and the outer periphery of the piezoelectric ceramic body 1. By forming an annular electrode gap _G1 smaller than the planar area of the piezoelectric ceramic body 1, the driving force in the circumferential direction and the radial direction is reduced, and the transverse vibration mode or the radial vibration mode is further reduced. This makes it possible to further reduce spurious signals.

The holes 4 are set so that the maximum diameter thereof is smaller than the wavelength λ of the sound wave in the sound field medium at the natural resonant frequency f ₀ of the thickness longitudinal vibration of the honeycomb-shaped vibrator. That is, when the mouth shape of the hole 4 is circular, the diameter l thereof is selected to be smaller than the wavelength λ of the resonance frequency f ₀ . In addition, when the mouth shape of the hole 4 is formed into a square shape, as shown in FIGS. 3 and 4, the diagonal length l is the maximum diameter, and l<λ
Select so that

As mentioned above, if the hole 4 is formed so that its maximum diameter l is smaller than the wavelength λ of the resonant frequency f ₀ and is pulse-driven when emitting ultrasonic waves into the water, the mechanical quality in the water will be improved. It was found that the coefficient Qm is lower than that of conventional honeycomb-shaped transducers, the ultrasonic pulse width is shortened, and the distance resolution is improved.

Effects of the Invention As described above, the honeycomb-shaped vibrator according to the present invention has a large number of holes in the thickness or in the vertical direction of the piezoelectric ceramic body, and electrodes are formed on both sides of the thickness or in the vertical direction. , since an electrode gap is formed between the periphery of this electrode and the outer periphery of the piezoelectric ceramic body, the transverse vibration mode or radial vibration mode and its harmonic vibration mode are reduced, and spurious waves are reduced. At the same time, it reduces the mechanical quality factor Qm under load, shortens the ultrasonic pulse width underwater or in biological tissue, and improves distance resolution, making it suitable for underwater acoustic equipment such as fish finders or ultrasonic diagnostics. A honeycomb-shaped vibrator suitable for use in a probe or the like can be provided.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a honeycomb-shaped vibrator according to the present invention, FIG. 2 is a front sectional view, and FIGS.
The figure is a diagram illustrating a method for determining the maximum diameter when the hole is made into a rectangular shape, and FIG. 5 is a perspective view of a conventional piezoelectric vibrator. 1... Piezoelectric ceramic body, 2, 3... Electrode, 4... Hole,
G ₁ ...electrode gap.

Claims (1)

[Scope of Claims] 1. A large number of holes are provided in the thickness or the longitudinal direction of the piezoelectric ceramic body, and electrodes are formed on both sides of the thickness or in the vertical direction, and the periphery of the electrode and the outside of the piezoelectric ceramic body are formed. A honeycomb-shaped vibrator characterized by having an electrode gap formed between the electrode and the periphery. 2. The honeycomb-shaped vibrator according to claim 1, wherein the holes have a diameter smaller than the wavelength of the resonant frequency. 3. The honeycomb-shaped vibrator according to claim 1 or 2, wherein the holes penetrate through the piezoelectric ceramic body in the thickness or longitudinal direction.