JPS5946852A - Inspection device of acoustic rubber - Google Patents

Abstract

PURPOSE:To detect the position and size of the foam or foreign matter included in acoustic rubber by placing the acoustic rubber which is an object to be measured on sheets consisting of electrodes segmented like straps, receiving the transmission acoustic waves transmitted through the sheets and the reflected waves from the object to be measured with the sheets, and measuring the time delay between the transmitted and received waves. CONSTITUTION:A holding plate 4 consists of a flat plate-like synthetic resin plate having excellent acoustic permeability, and is mounted thereof with sheets 1, 1' by means of rubber or a synthetic resin 7. A case 3 contains therein an acoustic oil 6 which propagates the oscillation of an oscillator 2 in the form of an acoustic wave. If it is assumed that the foam 9 in an object to be measured corresponds to the position 9' on the straps C of row in the figure A, the output by the reflection wave therefrom appears at the output terminal Ct of the straps C. Similarly when the straps of line in the figure B are considered, the figure indicates that the strap corresponding to the position 9' is f' and the output by the reflected wave thereof appears at the terminal ft'. In other words, if the outputs of the respective rows and lines are collated, the presence of the reflected waves in the positions where both coincide is known. The resolving power for the position and size is therefore higher as the electrodes are segmented more finely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for acoustic rubber used in a transducer.

When manufacturing acoustic rubber, several sheets of thin rubber are pressed together to form a rubber sheet of a specified thickness. At that time, air bubbles may be mixed in while the thin rubber sheets are pressed together, and may remain as residual air bubbles even after heating and compression molding. When acoustic rubber containing air bubbles is used in audio equipment, particularly in underwater acoustic transducers, it becomes a cause of prevention of sound transmission, resulting in deterioration of the transducer and disturbance of directivity.

In addition, an ultrasonic flaw detector is used to detect air particles and foreign objects inside the acoustic rubber.

Although it can be detected to some extent with X-rays, etc., there are problems with the skill level of the examiner and the X-ray equipment, so it is not easy to judge whether it is necessary.

The present invention is a polymeric piezoelectric material with excellent acoustic transparency.

By using a rubber or synthetic resin holding plate, the present invention provides an apparatus for inspecting the presence or absence of air bubbles and foreign matter in uncrushed rubber, as well as their positions and sizes.

The present invention is for testing acoustic rubber used in wave transducers, and a flat polymer piezoelectric material or its electrodes is placed on the holding plate of a tester that transmits sound waves via rubber or synthetic resin. A sheet divided into straps is installed in one layer or in multiple layers, and an acoustic rubber object to be measured is placed on top of the sheet, and the transmitted sound waves transmitted through the sheet and the reflected waves from the object to be measured are received by the sheet. It has the function of detecting the position and thickness σ of air bubbles or foreign matter mixed in the acoustic rubber by measuring the time delay between the transmitted and received waves.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view for explaining the invention in detail.

1' is a reversible material 11 that is made of a sheet of polymeric piezoelectric material with excellent acoustic transparency and converts acoustic signals or mechanical vibrations into electrical signals. The case of conversion will be explained.

The holding plate 4 is made of a flat synthetic resin plate with excellent acoustic transparency, and the sheets i and t' are attached via rubber or synthetic resin 7 with adhesive or with an insulating solution such as oil to prevent air bubbles from entering. The case 3 houses acoustic oil 6, and the acoustic oil 6 propagates the vibrations of the vibrator 2 as ultrasonic waves. Here, the vibrator 2 is provided with a vibration isolation phase 5 to prevent mechanical vibration from being transmitted to the holding plate 4 through the case 3.

Sanmo molecule 1-E S, 4 used for sheet 1.1'
A' FL i, l, acoustic impedance density (ρC)
<ρ: dense 1 person + 1, <: : speed of sound> is 1.6X10
'~2.3Xl 05 (g/ui2-8), so of course this is a big deal.1. Rubber or synthetic resin board7. As for the acoustic oil 6, one having the same sound η·'r impedance ratio is used [9].

FIG. 2 is a diagram for explaining the principle. It is a diagram with an object to be measured 8 placed on top. Sheets 1 and 1' are used to determine the position and size of air bubbles or foreign matter 9 in #8I and H to be measured.
Or 't'(1') of the sheet, part of the pole d3 diagram (A).

As shown in (13), the sheet is subdivided into strug-like sheets a to l+ and a' to h'. For example, if the bubble 9 in the object to be measured is
If 1 is applied to the position 9' of the column strap C'' in FIG. Same a) 6 to 21'+
If you look at the IT strap in Figure 3 (one),
It can be seen that the strap corresponding to IP¥ at 9' is f', and the output due to its reflected wave appears at the terminal ft/. That is, by comparing the outputs of each column and each row, it can be seen that a reflected wave exists at a position where both coincide. Therefore, the resolution of position and size will improve if the image is subdivided into as many parts as possible. The dimension between the vibrator 2 and the holding plate 4 is a dimension that at least avoids a near sound field. When the sheets 1 and 1' receive sound waves from the vibrator 2, the distance is short, so it is regarded as a spherical wave, and the absolute value of the sound pressure, , and phase difference differ depending on each matrix. Therefore, the phase delay circuit 10 or the like corrects the dimensional difference of 1.1'.

It should be noted that the sheet does not necessarily need to be multi-layered, and can be made of one layer by subdividing the front electrode and the back electrode into orthogonal straps. However, since it is necessary to provide a space for taking out the electrode terminals, if the number of subdivisions is excessively increased, the exclusive surface of the sheet will decrease, and the resolution will tend to decrease.

Further, although the present invention has been described with the sheets 1 and 1' having a circular shape, they may have any shape in accordance with the shape and dimensions of the object to be measured.

The present invention uses reflected sound waves to detect the presence or absence of air bubbles and foreign objects in the acoustic rubber, as well as their positions and sizes.It is possible to easily detect the position and shape of air bubbles and foreign objects that impede acoustic fL in water using a single acoustic rubber. can be inspected.

[Brief explanation of drawings]

FIGS. 1, 2 and 3 are diagrams showing a sectional view, a principle diagram and a sheet of the apparatus according to the invention; FIG. 1.1'... Sheet, 2... Vibrator,
3... Case, 4... Holding plate, 5...
... Vibration proof, 6... Acoustic oil, 7...
・Rubber or synthetic resin, 8...Object to be measured, 9...
... Air bubble or foreign object, 9'... Projection position of air capsule or foreign object, 10... Phase delay circuit. Agent Patent Attorney Shinpaku Uchihara (Sen 5 Z (f3) yq″
Y′

Claims (1)

[Claims] It is attached via rubber or synthetic resin to the holding plate of the tester that transmits sound waves, and consists of a single layer or multilayer sheet made by dividing a planar polymeric piezoelectric material or its electrode into straps, and the object to be measured. The method includes means for receiving the transmitted sound waves transmitted through the sheet on which the object is placed and the reflected waves from the object to be measured by the sheet, and measuring the time delay between the transmitted and received waves, and based on the measurement results. An acoustic rubber inspection device characterized by detecting the position and size of air bubbles or foreign matter mixed in the acoustic rubber.