JPS6070352A - Electromagnetic ultrasonic transducer - Google Patents

Abstract

PURPOSE:To propagate an ultrasonic wave only to one direction, by combining a plurality of high frequency current coils provided on a permanent magnet and a condenser. CONSTITUTION:A permanent magnet 21 having N and S poles povided to both side end surfaces thereof generates a magnetic field B in a direction vertical to the surface of a body to be inspected. A plurality of divided high frequency current coils L1-L4 are arranged at constant pitches so as to cross the direction of the magnetic field B at right angles and respectively connected in series. Condensers C1-C3 are respectively interposed between the respective connection parts of the coils L1-L4 and the terminal parts thereof and the values of the coils L1-L4 and the condensers C1-C3 are set to predetermined relation and time difference is respectively generated to currents flowing to the coils L1-L4. By this mechanism, an ultrasonic wave can be propagated only to one direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an i+i magnetic ultrasonic transducer for a flaw detection device for flaw detection of metallic structural members such as ship hulls.

For example, in order to detect welding conditions inside a hull weld using ultrasonic waves, a transducer as shown in FIG. 1(a) is used to generate ultrasonic waves. This transducer uses, for example, a U-shaped permanent magnet 11, and between the N and S poles of this magnet 11 there is a coil 12 having a plurality of straight portions perpendicular to the direction in which the magnetic field is generated. It is arranged and configured.

In other words, as shown in FIG. 6(b), when a high-frequency electric current is passed through this coil 12, eddy currents 1 to 17 are generated in the object 13 to be inspected corresponding to the hull welds, and these eddy currents The currents 11 to 7 are caused by the siren flux Fl to F7 due to the interaction with the magnetic flux B, ~B7, which is generated inside the test object 13 from the N pole to the S pole direction by the permanent magnet 1.
occurs. The direction of these Lorentz forces F1 to F7 changes by 1800 degrees in the form of a longitudinal wave at the interval To of the coil nozzle 2 along with the above-mentioned eddy currents 11 to 7.
Ultrasonic waves are generated inside the object to be inspected 13 in response to the direction change of -F7.

Here, the direction θ in which the ultrasonic wave forms the composite wavefront 14 and propagates is set to an angle that satisfies the following.

In addition to the U-shaped permanent magnet 1 as described above, a transmagnet using a rectangular permanent magnet 15 having N and S poles on both end faces as shown in FIG. Sa is considered. The coil 12 is arranged so as to face the north pole of the magnet 15 and whose straight portion crosses the coil 12.

That is, as shown in FIG. 2(b), this transducer generates Lorentz forces F1 to F8 by changing them by 180° in the form of transverse waves, and the Lorentz forces F1 to F8 in the form of transverse waves change by 180 degrees.
At F8, an ultrasonic composite wavefront 14 is formed in the same propagation direction θ as described above.

Here, the composite wavefront 14 of the ultrasonic waves is formed not only in the θ direction but also in one θ direction as shown by the broken line even in the case of the tilt shown in FIGS. 1 and 2.

In other words, if there is a flaw or the like inside the subject's body 13, the ultrasonic wave will be reflected at the position where the flaw exists, and this reflected wave will be transmitted to the transducer in the reverse process as described above. This is converted into a stain signal and detected.

However, in such a transducer, the ultrasonic composite wavefront 14 is formed in both the θ direction and the 10 direction. It is not possible to determine whether the flaw exists in the θ or -θ direction, and at the same time, the ultrasonic wave propagates outside the flaw detection area, which may lead to erroneous determination.

For this reason, for example, as shown in FIGS. 3(a) and 3(b), a transducer configured to propagate ultrasonic waves only in the θ direction.
-Sa is considered. In other words, this transday
The high frequency current coils 16a to 16d are divided into multiple parts.
Each of the coils 16a to 16d
By delay-controlling the high-frequency currents (H1 to (H4)) flowing at fixed time intervals, a composite wavefront 14 of ultrasonic waves is formed only in one direction (the θ direction). In this case, the incident angle (propagation direction) of the ultrasonic wave is θ, and the sound speed is 1.
Coil J6bT is 2T-s stone θ/■, coil 16c is 4T-6Inθ/■, coil 16d is 6
When T-slnθ/■, a super-fi wave composite wavefront 14 is formed only in the θ direction.

However, the high frequency current coil 16 divided into multiple parts like this
If the high-frequency currents IH1 to H4 are delayed and controlled at fixed time intervals t without flowing to the coils a to 16d, the above coil 1
A plurality of current transmitting devices and receiving devices corresponding to each of 6a to 16d become a huge number, and the overall structure of this transducer becomes large.

This invention was made in view of the problems mentioned above.
For high-frequency current coils divided into multiple parts, it is not necessary to have separate time transmitting and receiving devices.
It is an object of the present invention to provide an electromagnetic ultrasonic run stage user that can propagate ultrasonic waves in only one direction with a simple configuration.

That is, the frost magnetic ultrasonic transducer according to the present invention includes a magnetic circuit that generates a magnetic field perpendicular or parallel to the surface to be measured, and a magnetic circuit that is arranged at a constant pitch at a plane angle with the direction of the magnetic field generated by this magnetic circuit. A plurality of high-frequency current coils are connected in series, and a plurality of capacitors are interposed between the connection portions of the plurality of high-frequency current coils and their terminal ends, and each of the high-frequency current coils and the capacitors are The values of and are set in a predetermined relationship.

An embodiment of the present invention will be clearly explained below with reference to Figure m1.

FIG. 4 shows its configuration, and this transducer is equipped with a rectangular permanent magnet 21 having, for example, N and S poles on both end faces.

This permanent magnet 21 generates a magnetic field B sound in a direction perpendicular to the surface of the object to be inspected, and double-acts at a constant pitch T at right angles to the direction of the magnetic field B generated by this magnet 2. The high-frequency current coils divided into 1 to L4 are arranged, and each of them is connected in series. A plurality of capacitors C1 to C3 are interposed in parallel between the connection portions of the plurality of high-frequency current coils 1 to L4 and their terminal ends, and furthermore, a plurality of capacitors C1 to C3 are interposed in parallel to the terminal ends of the coils 1 to L4. is constructed by connecting an anti-reflection resistor R.

Here, FIG. 5 shows the plurality of high frequency current coils L1 to L.
4 i, multiple capacitors C1 to C3, and resistor R. The values of these multiple coils L1 to L4, capacitors C1 to C3, and resistor R are set in the following predetermined relationship. Decide.

L2=L3 =L4= -・= Ln, = L -=
1 equation + = Ln = L/ 2 ・= 2 equation 2T
- Corridor θ/V = 'rc... Type 3 R-J Ro door...
・Type 4 However, ■ The speed of sound, that is, in the transducer configured in this way, the high frequency current coils L1 to L4 in Fig. 5 above
, capacitors C1 to C3, and resistor R, respectively, can be replaced with an equivalent circuit as shown in FIG. Here, each of the circuit networks shown surrounded by broken lines A-C is a constant type delay circuit network based on a lumped constant system as shown in FIG. In this case, the following time difference td occurs between the currents i1 and i2 flowing through each coil Lz/2.

td≧J琵-...52tJ), the currents IIN~■H4 flowing through the respective coils L and ~L4 in FIGS. 4 and 5 above necessarily have the time difference td in the above equation 5. An eddy current ■! similar to that shown in FIG. 3(b) occurs.
.about.8 and transverse wave-like Lorentz forces F and .about.F8 are generated within the object to be inspected I3.

That is, as mentioned above, the high frequency current coils L1 to L
Since each of the high-frequency currents H1 to IH4 flowing through the channel 4 is controlled by a delay control source at a fixed time interval t, the ultrasonic wave propagates only in the θ direction, similar to the case in FIG. 3(b). A composite wavefront 14 of ultrasonic waves is formed only in a thousand directions. In this case, multiple coils L
By connecting the anti-reflection resistor R to the end of the 1-L4 rows, no current is caused to flow through the coils L1-L4 again.

Therefore, the transducer configured in this manner has a simple circuit configuration similar to that of North Korea, which combines a plurality of high-frequency current coils L1 to L4 and capacitors to C3, and reliably transmits ultrasonic waves in one direction θ. can only be propagated to

In the above embodiment, the two rectangular permanent magnets
The magnetic field B was generated in a direction perpendicular to the surface of the object to be inspected 130. For example, as shown in FIGS. 8(a) and 8(b)
As shown in K, yokes 22h and 22b may be provided on both end surfaces of the rectangular permanent magnet 21 to generate a magnetic field Bf in a direction parallel to the surface of the object to be inspected 130.

In this case, a thin wave-like Lorentz force F exists within the rose test object 13.
1 to F8 are generated, and this longitudinal wave-like Lorentz force Fl-FB forms an ultrasonic composite wavefront 14 in the same propagation direction θ as in the above embodiment.

As described above, according to the present invention, ultrasonic waves can be transmitted in one direction only by a simple combination configuration with multiple capacitors, without requiring separate transmitting and receiving devices for multiple high-frequency current coils. It becomes possible to propagate it. As a result, ultrasonic flaw detection can be performed that accurately corresponds to the flaw detection area, without making the overall structure of the transducer complicated or large.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams explaining a conventional transducer, respectively, and FIGS. 3(a) and 3(b) are block diagrams showing a transducer that propagates ultrasonic waves only in one direction, respectively. FIG. 4 is a configuration diagram showing an electromagnetic ultrasonic transducer according to an embodiment of the present invention, and FIG. 5 is a diagram showing the state of propagation of the ultrasonic waves. A circuit configuration diagram showing a combination of a high-frequency current coil and a capacitor of a magneto-ultrasonic transducer. Figure 6 is a circuit configuration diagram equivalent to the circuit network shown in Figure 5 (V) above. Figure 7 is an equivalent circuit diagram showing the circuit network shown in Figure 5 above. A diagram showing a constant-type delay network corresponding to the equivalent circuit in FIG.
The figure shows another embodiment of the invention. 13... Test object, 14... Ultrasonic composite wavefront, 2
1...Permanent magnet, 22a, 22b-yoke, Ll~L4...High frequency current coil, Self~C3...capacitor. Patent attorney Takehiko Suzue Figure 1 (a) (b) Figure 2 (a) Figure 3 (a) Figure 4 Figure 6 A B C

Claims (1)

[Claims] A magnetic circuit that generates a magnetic field perpendicular or parallel to the surface to be inspected, a plurality of high-frequency current coils that are arranged at a constant pitch and connected at right angles to the direction of the magnetic field generated by this magnetic circuit, and It is characterized by comprising a plurality of capacitors interposed between the connection portions of each of the plurality of high-frequency current coils and their terminal ends, and the values of the respective high-frequency current coils and the capacitors are set in a predetermined relationship. m, a magnetotransducer.