JPS63236958A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To eliminate need for skillfulness for inspection and to improve the reliability of a inspection result by providing a bank and an ultrasonic-wave shield layer which surround a fitting surface between the fitting surface for ultrasonic-wave transmitting and receiving elements and the surface of a body to be inspected. CONSTITUTION:A sensor main body 31 is constituted by assembling the blocks 33 and 34 of the ultrasonic-wave transmitting element 11 and reflected wave receiving element 12 integrally by a member 36 across the ultrasonic-wave shielding layer 35, and the supply of driving pulses to the element 11 and the transmission of a received signal from the element 12 are performed through coaxial connectors 37 and 38. A plate 39 made of an elastic material is fitted outside each block by a metallic band 40 so that its end part 39a surrounds the fitting surface 31a and projects from the surface 31a and is also the bank surrounding the surface 31a. An injection opening 41 provided to the surface 31a is communicated with an intake 42 in the main body 31 and the intake 42 is connected to a feeder for contact medium supply. This sensor 1 is applied to a coating film provided on the surface of a concrete-based structure material to inspect a defect the adhesion of the coating film. etc., from a decrease in reflected signal level.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an ultrasonic sensor.

[Background technology]

Structural materials made of non-metallic materials such as concrete in buildings, such as concrete walls, mortar walls, walls with a mortar layer on top of a concrete layer, slate boards containing asbestos, molded boards such as cement, etc. The surface is coated with vinyl chloride, acrylic, urethane,
A coating of architectural exterior paint such as inorganic paint such as cement is applied. Several years after a building is completed, adhesion failures occur, such as the paint film starting to peel off from the non-metallic structural materials such as concrete. If the defective adhesion is left as it is, the defect will spread to the entire surface of the paint film, so it is necessary to find the defective point and repair it before that happens. Traditionally, when investigating poor adhesion of a paint film, one has to carefully look for abnormalities visually, or hit or rub the paint film with a jig with a steel ball about 20 m in diameter attached to the tip of a metal pole about 1 m long. This is done by making judgments based on the audible frequency of the sound, which is not only expensive as it requires a lot of time and effort from experienced workers, but also depends on the operator's intuition, which makes the test results less reliable. is also not enough. Therefore, it has been desired to improve the reliability of inspection results by reducing the number of dead lines in such inspections.

[Purpose of the invention]

In view of the above-mentioned circumstances, the present invention provides an ultrasonic sensor that has a structure suitable for inspection of such buildings, etc., and that can reduce the number of dead lines during inspection and improve the reliability of the results. (Disclosure of the Invention) In order to achieve the above object, the present invention provides an ultrasonic device comprising an element that transmits ultrasonic waves toward a subject and an element that receives reflected waves of the ultrasonic waves. The sonic sensor includes a sensor main body provided with both of the elements, and the sensor main body includes a bank surrounding the mounting surface so as to create a contact medium groove between the element mounting surface and the surface of the subject. The gist of the present invention is an ultrasonic sensor, characterized in that an ultrasonic blocking layer is provided between the two elements.

Hereinafter, an embodiment of the ultrasonic sensor according to the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1(a) to (C) show the appearance of an embodiment of the ultrasonic sensor according to the present invention, with FIG. 1(a) being a front view, FIG. 1(b) being a partial side view, and FIG. C1 is a bottom view.

FIG. 1(d) shows a schematic configuration of an ultrasonic element in this sensor.

The ultrasonic sensor l includes a sensor body 31 and a grip portion 32. The grip portion 32 consists of a U-shaped metal fitting 32a and a knob 32b. When using the ultrasonic sensor 1, hold the knob 32 and touch the mounting surface 31 of both elements 11 and 12 of the sensor body 31.
a to the surface of the subject.

The sensor main body 31 includes an element 11 for transmitting ultrasonic waves and an element 12 for receiving reflected waves. The spacing between the elements 11 and 12 depends on how the sensor 1 is used, but for example, in the case of detecting poor adhesion of a paint film applied to the surface of a structural material made of non-metallic materials such as concrete, it is usually 0. .5C11~5.
Selected during Oam.

Elements 11 and 12 have basically the same construction but are used differently. As shown in FIG. 1(d), the element 11.12 has a piezoelectric material 51, such as a pzT material, fixed to the tip of a metal cylinder 50 with adhesive or the like, and the cylinder 5 is a metal conductor.
A cable 52 is connected to one end of the piezoelectric body 51 and one end of the piezoelectric body 51. The piezoelectric body 51 and the cable 52 are fixed to the cylinder 50 using resin 53. Element 1
In the case of 1, when the electric energy of the drive pulse is applied to the piezoelectric body 51, the piezoelectric body 51 causes mechanical vibration, and an ultrasonic wave is sent out along with the vibration. In the case of the element 12, vibration occurs in the piezoelectric body 51 in response to the reflected wave, and a voltage is generated in the piezoelectric body 51 in response to the vibration.

In the sensor body 31, a block 33 in which the element 11 is provided and a block 34 in which the element 12 is provided are provided with an ultrasonic blocking layer (a material with a high Poisson's ratio such as a silicone rubber layer or a raw rubber layer) 35 between them. They are integrally assembled by a stopper member 36 with the two sides in between. The drive pulses are supplied to the element 11 via the coaxial connector 37, and the received signals generated at the element 12 are transmitted via the coaxial connector 38.

The outside of the blocks 33, 34 is made of elastic material (e.g. rubber).
The metal band 4 is arranged such that the end portion 39a of the plate 39 surrounds the mounting surface 31a and projects from the mounting surface 31a.
It is stopped at 0. The protruding end 39a of the slope 39 is
This serves as a bank surrounding the mounting surfaces 31a of both elements 11 and 12. As shown in FIG. 2, this bank (end 39a) is located between the mounting surface 3]a and the surface of the object 0 when the ultrasonic sensor 1 is pressed against the surface of the object 0. A contact medium groove P shown by a dashed line is formed. Element 1
If there is an air layer between 1.12 and the surface of the object 0, there will be problems such as blocking the entry of ultrasonic waves or causing reflections. I try not to do that.

The mounting surface 31a has an inlet 41.41 for supplying a contact medium.
is provided. This injection port 41 communicates with an introduction port 42 within the sensor body 31 . The inlet 42 is connected to a feeder for supplying a coupling medium. The contact medium from the feeder exits through the inlet 41.

In the ultrasonic sensor 1, the elements 11 and 12 are not separated, but are provided in one sensor body 31.

Therefore, the elements 11, 1 and 2 can be set simply by applying the sensor 1 to the surface of the object 0, so the sensor 1 can be easily set, especially on a vertical wall of a building.

In the ultrasonic sensor 1, transmission of ultrasonic waves and reception of reflected waves are performed by separate elements, and an ultrasonic blocking layer 35 is provided between the elements 11 and 12. In particular, low frequency ultrasonic waves are used for inspecting structural materials of buildings. Low frequency ultrasonic waves have little directivity and propagate laterally, so interference between elements 11 and 12 is likely to occur. However, in this ultrasonic sensor 1, since there is an ultrasonic blocking layer 35, interference between the elements 11 and 12 can be prevented and accurate inspection can be performed.

In this ultrasonic sensor 1, the contact medium injected into the contact medium groove P is held in a closed space surrounded by the mounting surface 31a, the surface of the object 0, and the end (bank) 39a. Even if the specimen surface is vertical, such as a vertical wall of a building, the coupling medium does not easily leak out and remains between the element 11.12 and the specimen zero surface. Therefore, since no air layer is formed between the elements 11, 12 and the coating film 70, accurate inspection can be performed. Furthermore, if the bank is made of an elastic material, it will better follow the unevenness of the surface of the subject and will come into closer contact with it, improving the degree of sealing of the contact medium groove P. However, it is not necessary that the embankment be an elastic material.

Next, a system that uses this ultrasonic sensor 1 to detect poor adhesion of a coating film provided on the surface of a concrete structural material of a building will be explained.

Figure 3 shows the schematic configuration of the system. Figure 4 shows
Partial hail appears around the installation location of the ultrasonic sensor l in this paint film inspection system. Figure 5 shows the waveforms of the main signals in this system, and Figure 6 shows the paint film inspection process.

The coating film inspection system includes an ultrasonic sensor 1, an excitation device 2, a preamplifier 3, a signal processing device 4, and an autofeeder 5 for supplying a contact medium.

When using the ultrasonic sensor I, a liquid contact medium 8 is injected into the contact medium groove P from the feeder 5 via the vibrator 5a. 5b and 5c are valves for adjusting the injection amount.

Water or oil is generally used as the contact medium 8, but water and oil have low viscosity and are difficult to use in areas such as vertical walls. In this invention, as the contact medium 8, for example, polyvinyl alcohol or a liquid medium containing glycerin is used. These liquid media have so-called thixotropic properties, and when ultrasound is not applied,
Since it has a high viscosity, it tends to stay between the ultrasonic sensor 1 and the coating film 7, and when ultrasonic waves are applied, the viscosity decreases and spreads sufficiently between the ultrasonic sensor 1 and the coating film 7 to prevent the formation of an air layer. . Specifically, for example, there is Nichirei Acetylene Sonicote (trade name). This liquid medium also has the advantage that even if it remains on the wall after the inspection, it will eventually be washed away by rainwater.

The frequency range used for the ultrasonic sensor 1 is from 100 to
A frequency between 500kHz is selected.

The resonant frequency of the element 11 is selected within this range. Normally, in nondestructive testing using ultrasonic waves (for example, detecting flaws in metal materials), ultrasonic waves with a frequency of IM to 2 MHz or more are used. Compared to metal materials, etc., materials in which air-drying architectural paint is applied to the surface of non-metallic structural materials such as concrete to a thickness of 100 to 500 μm (micrometers), the paint film and Due to the acoustic properties of the structural materials, sufficient reflected waves (echoes)
is not obtained. For ultrasonic waves with frequencies in the above range, the 0 frequency is 1, which has little absorption and provides sufficient reflected waves for inspection.
In the region below 00k)lz, vibrations as a natural phenomenon occur in the surroundings, and these vibrations are also received and become noise, making accurate inspection impossible.

As shown in FIG. 4 or 6, the ultrasonic sensor 1 is connected to
1iI7, and once the coupling medium has been injected, the measurement begins. 6a is a primer layer provided to improve the adhesiveness of the coating film 7.

Receiving the electrical energy of the drive pulse shown in the first row of FIG. 5 from the excitation device (hereinafter referred to as "balsa") 2, the element 11 causes mechanical vibration, as shown in the second row of FIG. As such, the element 12 that transmits ultrasonic waves of a predetermined frequency and receives zero reflected waves is usually one that has high sensitivity to the same frequency as the transmission frequency. Element 12
converts the received reflected wave into an electrical signal and sends it to the preamplifier 3. The signal amplified by the preamplifier 3 is sent to the signal processing device 4
sent to. On the other hand, a low-level synchronization pulse shown in the fourth row of FIG. 5 is sent from the pulser 2 to the signal processing device 4 at the same time as the drive pulse.

On the other hand, the signal processing device 4 includes a cathode ray tube oscilloscope. At the same time as the drive pulse is generated, time T
3, the synchronization pulse causes the oscilloscope to:
It is swept horizontally and also swept vertically by the received signal sent from the preamplifier 3. Therefore, as shown in Figure 3 or the third row of Figure 5, the color 1j! A reflected wave received by the element 12 is displayed after a certain period of time after the ultrasonic wave is incident into the interior of the element 7, and its signal strength Vp can be measured. The signal processing device 4 is also equipped with a recorder, and is capable of recording reflected waves on a recording paper 4b to measure the signal strength Vp.

Note that the actual received signal is a high frequency signal as shown by the broken line in the third row of FIG. 5, but in the signal processing bag Wt4,
Contour signals are displayed through signal processing.

Compared to the signal strength Vp when the adhesion of the coating film 7 is normal, as shown in FIG. low. Although it is not clear why the signal strength -Vp of the received reflected wave decreases when there is a defective adhesion point, if the coating film 7 is peeled off, the coating film 7 does not reflect the ultrasonic waves. We speculate that this may be because the waves change their own vibrations and absorb them, or they cause mode conversion, changing the frequency of the reflected waves to a frequency different from the transmission frequency. - Therefore, in this system, poor adhesion of the coating film 7 can be easily detected based on the decrease in the signal strength Vp without requiring any skill. The reliability of the test results is also high because there is no reliance on the operator's intuition.

Next, the results obtained when a test piece was prepared and a coating film was actually inspected using the coating film inspection system described above will be explained.

Figure 7(a), mountain) shows the test piece. Vertical 7
01, 150 cranes wide, 31m thick sled! A large number of test pieces 15 were prepared by applying a paint manufactured by Fujikura Kasei ■ (trade name: Tonecrete) to a thickness of approximately 0.4 mm on the surface of the test piece 16.

This test piece 15 was immersed in water at 10° C. for 2 hours to forcibly cause poor adhesion of the coating film 17.
It is coated with an accelerated treatment that involves a continuous freezing and thawing cycle by leaving it in the air at 20°C for 2 hours! The process was continued until *17 was completely peeled off.

Test piece 15 was inspected using the above-mentioned paint film peeling system, and the adhesive strength of the inspected portions was also measured using a Kenken type adhesive strength tester. The frequency of the ultrasonic waves used was 140 kHz, and the driving pulse had a repetition frequency o, 5 kHz, and a pulse width of 0.1 microsecond or less.

The measurement principle of the Kenken type adhesive strength test is as follows. The surface of a jig with a predetermined surface area (in this example, a jig with a diameter of 35 mm was used) is adhered to the coating surface using an adhesive, and a cut is made in the coating film along the adhesive point to reach the base material. A tensile force is applied to the jig, and the tensile force is measured when the coating film at the bonded area is peeled off along with the jig. The value obtained by dividing the tensile force at this time by the surface area is the adhesive strength.

After starting the acceleration process, five test pieces 15 were taken out every 24 hours, and the signal strength Vp was measured by the paint film inspection system, and the adhesive strength W was measured by the Kenken type adhesive strength tester. I did it. 15 test pieces each
As shown in FIG. 7(a), there were two measurement locations: point a (near the center of the test piece) and point b (near the short side). The measurement results are shown in Table 1 and Fig. 8 (al, (b)). The displayed values are the average of the measured values of five test pieces 15. Signal strength ■
Regarding p, each measurement result is a ratio based on the signal strength before the start of the promotion process.

As is clear from Table 1 and Figure 8(a),
It can be seen that a decrease in the signal strength Vp is associated with a poor adhesion state of the paint film, and that when the ultrasonic sensor according to the present invention is used, it is possible to accurately detect locations of poor adhesion of the paint film.

The present invention is not limited to the above embodiments, and the structure of the ultrasonic sensor and the material of the contact medium may be other than the exemplified materials. The configuration of the bank may also be such that, for example, only the upper part of the bank is made of an elastic material. The use of ultrasonic sensors is not limited to detecting poor adhesion of paint films.

〔Effect of the invention〕

The ultrasonic sensor according to the present invention has the configuration described above. That is, since the transmitting and receiving elements are provided in one sensor body, the ultrasonic sensor can be easily installed. Furthermore, the sensor body is provided with a bank that surrounds the mounting surface to create a reservoir of contact medium between both element mounting surfaces and the test object surface, so that the contact medium is retained between the test object surface and the sensor. It will definitely be done. Furthermore, since the ultrasonic blocking layer is provided between both elements, both elements do not interfere with each other. Therefore, it has become possible to easily and accurately inspect paint films on vertical wall surfaces of buildings.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(C) show the external appearance of an embodiment of the ultrasonic sensor according to the present invention, in which FIG. 1(a) is a front view, FIG. ) is a bottom view. FIG. 1 (dl is a sectional view showing the schematic configuration of the ultrasonic element of this ultrasonic sensor, and FIG. 2 is an explanation of the contact state between the ultrasonic sensor and the subject. Figure 3 is a schematic configuration diagram of a system when inspecting the adhesion state of a paint film using the ultrasonic sensor, and Figure 4 is a diagram of the installation location of the ultrasonic sensor in this paint film inspection system. Partial cross section, 5th
The figure is a waveform diagram of the main signals in this system, Figure 6 is an explanatory diagram showing the state of paint film inspection work, and Figure 7 (a)
l, (b) shows the test piece, and Fig. Tal
is a plan view, and the figure (bl is a front view. FIG. 8(a) is
FIG. 8 is a graph showing the relationship between the elapsed time of acceleration processing of the test piece and the signal strength (BL is a graph showing the relationship between the elapsed time of acceleration processing of the test piece and adhesive strength.) Ultrasonic sensor 11 ...Element for transmitting ultrasonic waves 1?...Element for receiving reflected waves 31...Sensor body 31a...Mounting surface 39a...Tsutsumi Attorney Patent Attorney Takehiko Matsumoto 2 Figure 4 Figure! 5 ~ 沁 6 ~ Table 7 Figure 8 (a) 1K1Chofusho (self-initiation April 16, 1985 2, Title of invention ln-, Lua'/Ultrasonic sensor 3, correction Relationship with Hanyu Patent applicant Location 2-1-2 Oyodo-kita, Oyodo-ku, Osaka Name Name: Nippon Paint Co., Ltd. Representative Masao Suzuki 4, Agent” Filed on March 25, 1988 Patent side (1) 6, Specification subject to amendment 7, Contents of amendment■ In the first line of page 12 of the specification, "Time T3J" is changed to "
Correct the time to TIJ.

Claims (3)

[Claims] (1) An ultrasonic sensor that includes an element that transmits ultrasonic waves toward a subject and an element that receives reflected waves of the ultrasonic waves, including a sensor body that is provided with both of the elements, and The sensor body is provided with an embankment surrounding the mounting surface so as to create a coupling medium reservoir between the element mounting surface and the surface of the subject, and an ultrasonic blocking layer located between the two elements. Features of ultrasonic sensor. (2) The ultrasonic sensor according to claim 1, wherein an injection port for supplying a coupling medium is provided on the element mounting surface. (3) The ultrasonic sensor according to claim 1 or 2, wherein the bank is made of an elastic material.