JPH067715B2 - Acoustic transducer - Google Patents

Description

TECHNICAL FIELD The present invention relates to new and improved acoustic transducers, and more particularly to point-contact acoustic transducers having sharpened or conical elements.

BACKGROUND OF THE INVENTION In acoustic detectors conventionally used to detect sound waves and ultrasonic waves emitted from the surface of a given material,
Damped resonators are commonly used to establish the effective frequency range of operation.

However, the level of attenuation obtained in such a detector is such that the level of broadband response indication that covers the full frequency range of primary interest, including, for example, the kilohertz and megahertz frequency range, is the exact level required. It is insufficient.

Furthermore, the conventionally used structures generally rely on receiving acoustic signals over a large contact area by the velocity sensitive sensing elements. Such a configuration greatly deforms the received acoustic information.

Therefore, one object of the present invention is to provide a compact wideband point contact type acoustic transducer which reduces the contact area and improves the sensitivity in the case of surface deviation.

Another object of the present invention is to provide an acoustic transducer as described above, which does not require a coupling medium to detect displacement indications.

DISCLOSURE OF THE INVENTION The point-contact acoustic transducer of the present invention is characterized by having a sharp or conical piezoelectric sensing element made of an effective piezoelectric material and having an improved transducer tip. The detection element is mounted on a conductive damping weight, and is formed in a conical shape or a sharp shape so as to eliminate high-frequency ultrasonic waves propagating backward.

According to the present invention, the tip of the detection element has a convex shape,
According to one embodiment, an electrical ground connection for the converter is provided. The electrical connection on the high potential side is provided by a conductive damping weight. The tip of the sensing element extends below the rest of the transducer so that it can contact the acoustic vibrating surface to be measured.

According to one embodiment of the present invention, a flexible sheet of conductive material transforms to seal the transducer and thereby protect the transducer from adverse environmental and electrical effects. It covers the receiving end of the detector including the tip of the detecting element protruding downward from the detector. The tip of the sensing element is physically connected to the sheet of conductive material.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows an acoustic transducer 10 including a sharp sensing element 11 which receives an acoustic signal from a surface 10 'to be measured for acoustic indication. The detection element 11 is an acoustic vibration surface 10 '.
It may be in direct contact with the acoustic vibrating surface, or via a flexible sheet (17 ') of electrically conductive material as shown. The tip of the detecting element 11 is located on the surface 1 of the transducer 10.
It projects toward 0 '.

The detection element 11 is preferably formed in a sharp or conical shape in order to prevent acoustic reflections on the surface 10 'to be measured. The lower end of the detector element 11, that is the receiving end, is directed towards the surface 10 'to be detected. By virtue of the sharpened shape of the detection element 11, the acoustic transducer 10 works effectively even on relatively rough surfaces and does not have to be precisely aligned with the surface to be measured.

The detection element 11 is a piezoelectric element, which makes it possible to convert acoustic energy into an electrical signal which reflects the frequency of the disturbance applied to the surface 10 'to be measured. The preferred piezoelectric material in this case is PZT-4. Other materials which have relatively high acoustic losses and which function, if not better, than the piezoelectric elements described above, include lead zirconate titanate, lead metaniobate, and many similar ceramics. These materials are first machined to the preferred conical shape and then electrically polarized in a manner well known in the art.

The preferred conical apex angle of the tip of the sensing element 11 is about 60 °.
The diameter of the base portion is 6.00 mm, the height is 5.00 mm, the diameter of the tip is 1.50 mm, and the width and thickness of the wear shoe are 1 mm and 0.10 mm, respectively.

The detection element 11 is mounted, for example, by adhering it onto a conductive damping weight, preferably silver epoxy, in which case the damping weight 12 is preferably cylindrical and made of brass. .

Due to its conductivity, the weight 12 can transmit the electric signal generated in the detection element 11 to the coaxial cable connector 14 including the inner conductor 141 and the outer conductor 142.

The damping weight 12 is appropriately mounted by, for example, a method such as interference fitting in the insulating member 16. The insulating member 16 is preferably cylindrical so that it can effectively retain the cylindrical damping weight 12 without slipping axially.

The insulating member 16 has an inner flange 161 at the upper edge thereof, which acts as a stopper for holding the damping weight 12 at a predetermined position. The insulating member 16 is held in an outer shielding case 17 which is preferably made of steel and is closed by an upper end element 171 preferably of the same material to ensure shielding from above.

The coaxial cable connector 14 extends through the case 17 made of steel in a screwed state. Further, the coaxial cable connector 14 is an insulating material 14 effective for electrically insulating the inner conductor 141 and the outer conductor 142.
Contains 0.

As shown in FIG. 2, a conductive overlay 33 is appropriately provided on the lower end, that is, the tip of the detection element 11. The overlay 33 is, for example, a silver metallic layer sprayed on the tip of the detection element 11. This overlay 33 is preferably formed to include a tab 34 extending upwardly away from the surface 10 'to be measured. The size of the tab 34 is about 0.5 mm × 0.5 mm so that its area is relatively small compared to the total area of the tip 35.

Furthermore, the overlay 33 is provided with a wear tip 35 which will be described in detail later. As shown, the wear tip 35 is convex so that it can function effectively on rough surfaces without precise alignment.

In FIG. 1, the insulating member 16 allows a suitably electrically insulated wire 67 to extend through the insulating member 16 to electrically connect the overlay 33 to the coaxial cable connector 14. The duct 66 is bounded. In particular, in accordance with one preferred embodiment of the present invention, conductor 67 connects tab 34 of overlay 33 to conductor 141 or 142. FIG. 1 shows such a configuration and one embodiment. The tab 34 is connected to the outer conductor 142 of the coaxial cable connector 14. Coaxial cable connector 14
The inner conductor 141 of FIG.
It is connected to the.

The coaxial cable connector 14 is configured to process a radio frequency signal in view of the shielding effect of the outer conductor 142. This ensures a wideband signal frequency provided by the converter 10.

The wear tip 35 is a convex disc of a hardened silver-copper alloy brazed in place on the overlay 33. The wear tip 35 provides a convex smooth contact surface,
This brazes it into place so that it can effectively make point contact with the surface to be measured.

The outer shielding case 17 has a hole on the lower side thereof so that the detection element 11 can measure the acoustic vibration surface 1 to be measured.
It can extend toward 0 '. Further, the outer shield case 17 includes an upper end member 171 for ensuring a completely shielded operation from above, for example.

The measurement is started when the detection element 11 directly or indirectly contacts the acoustic vibration surface. No lubricant, solvent, gel, or other material needs to be applied to the surface being measured to perform the action.

The lubrication medium does not have to be applied because the tip 35 of the transducer 10 extends beyond the body of the transducer and can thereby come into contact with the acoustic vibrating surface 10 'to be measured. The tip 35 causes the flexible sheet 17 'to curve uniformly,
This causes the surface 10 'to bulge downward. This allows the surface 10 'to be measured to be even rougher.

For the purpose of electrically shielding, it is preferable that the partial shielding member 88 is attached to the lower surface of the outer shielding case 17 in a state of being in contact therewith. In this case, the shielding member 88 has a central hole 188 which allows the detection element 11 to extend beyond the plane of the lower end of the outer shielding case 17 so that it can come into contact with the surface 10 ′. A lock ring 99 is used to fix the shielding member 88 to the case 17.

The transducer 10 is used in a state where it is arranged on an arbitrary selected acoustic vibration surface. In order to ensure that the transducer 10 is in contact with the selected surface, it is often the case that the transducer 10
It suffices to tap in place on the surface to be measured.

In this operation, the coaxial cable connector 14 is the third
Display device or processor 1 as shown
13 is connected. Such a device is useful for properly analyzing and providing a wide band signal provided by setting the transducer 10 on the acoustic vibration surface 10 'to be measured.

With such a configuration, at least 50 kHz to about 1.5
A very wide bandwidth converter frequency response range of mHz can be ensured.

Although the present invention has been described in detail above with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a transducer of the present invention showing a conductive damping member and a sharp transducer tip projecting from the member and extending toward an acoustic vibration surface to be measured. FIG. 2 is a schematic enlarged partial perspective view of the tip of the converter seen obliquely from below. FIG. 3 is a block diagram of an arrangement including a signal processing and display device that may be employed in combination with the converter of the present invention. 10 ... Acoustic transducer, 10 '... Surface to be measured (acoustic vibration surface), 11 ... Detection element, 12 ... Damping weight, 14 ... Coaxial cable connector, 16 ... Insulating member, 17 ... Outer shielding case, 17' … Flexible sheet, 33… Overlay,
34 ... Tab, 35 ... Tip, 66 ... Duct, 67 ... Conductor,
88 ... Shielding member, 99 ... Lock ring, 113 ... Display device or processing device, 121 ... Conducting wire, 140 ... Insulating material, 141, 142 ... Conductor, 161 ... Inner flange, 171 ... Top member, 188 ... Central hole

Claims (1)

[Claims] 1. A piezoelectric transducer configured to contact an acoustic vibrating surface to be measured, which is an acoustic transducer for detecting an acoustic signal and generating an electric signal indicating the acoustic signal, and the piezoelectric means from the rear side. A conductive weight means for supporting, a shielding means for supporting the conductive weight means and the piezoelectric means in an electrically insulated state, and generated in the piezoelectric means in response to the vibration of the acoustic vibrating surface. Electrical means for detecting the generated electric signal, the piezoelectric means having a conductive tip extending below the shielding means so as to come into contact with the acoustic vibrating surface. An acoustic transducer that does.