JPH0646194B2 - Signal transmission mechanism of ultrasonic flaw detector - Google Patents

Description

The present invention relates to a signal transmission mechanism of an ultrasonic flaw detector, which has a flaw detector main body and a probe, and in which the probe rotates. The present invention relates to a signal transmission method using the mechanism.

[Prior Art] In ultrasonic flaw detectors in which the probe rotates, there is a problem in signal transmission between the rotating probe and a fixed flaw detector main body that analyzes signals from the probe. Becomes

As a conventional signal transmission mechanism, there is one using a slip ring, but it has problems in durability and maintenance because it has a sliding contact.

Therefore, as shown in FIG. 6, it has been considered to use a capacitance to transmit signals in a non-contact manner. That is, in the figure, the hot side 1 and the ground side 2 are arranged in pairs and have the same configuration.

The conductors 1b and 2 are attached to the foundations 1a and 2a which are insulated from the rotary shaft 3.
b is fixed, the bases of the vanes 1c and 2c are supported by the conductors 1b and 2b, and the signal lines 4a and 4b from the probe are connected to the conductors 1b and 2b. And the blade 1c,
Fixed vane plates 5a and 5b on the main body side of the flaw detection device intersect and face 2c.

When this configuration is modeled, as shown in FIG. 7, the probe A has a circuit including a ground-side capacitor C1 and a hot-side capacitor C2. The relationship between the capacities of the capacitors C1 and C2 and the sensitivity in this case is as shown in FIG. Note that FIG. 9 shows the HOT and GN of FIG.
It is a graph which shows the result of having measured the change of the amplitude of a standard defect echo, separating D and 10 sufficiently. By doing this, the eighth
The capacitance of the capacitor, represented as C3 in the figure, can be substantially zero. The horizontal axis represents the capacitance between the vane plates 1c and 2c of the rotating side electrode and the fixed vane plates 5a and 5b. The capacitance can be changed by the number of pairs of the vanes facing each other. Here, when the number of pairs is 1, 2, 3, and 4, the capacitances are C = 250, 500, 750, and 100, respectively.
It becomes 0 pF. The echo amplitude is measured by "Ultrasonic flaw detection test method (JIS Z23
44-1973) "(published by the Japanese Standards Association), Annex 4, the method of measuring the sensitivity margin of the ultrasonic flaw detector.

[Problems to be Solved by the Invention] However, the above-described conventionally conceived signal transmission mechanism has the following drawbacks.

In the above signal transmission mechanism, the transmission efficiency is determined by the gap between the vane plates 1c, 2c and the fixed vane plates 5a, 5b, so that they face each other at an extremely small interval, which makes the structure complicated and costly. In addition to the above, there is a drawback that when rotating at a relatively high speed, a large amount of heat is generated, power loss is large, and the gap cannot be reduced.

Further, although the above mechanism is as shown in FIG. 7 as an ideal model, in reality, many pairs of hot side 1 and ground side 2 are arranged in a narrow space as many as the number of flaw detection channels. , A capacitance is generated between the hot side 1 and the ground side 2 which are close to each other, and the capacitor C3 between them is added as shown in FIG. 8, and the sensitivity is lowered as shown in FIG. There is a drawback that. In addition,
FIG. 10 is a plot of the change in the amplitude of the standard defect echo when the electric capacitances of C1 and C2 in FIG. 8 are fixed and C3 is changed. Further, the electric capacity of C3 is changed by changing the interval between HOT and GND in FIG.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a signal transmission mechanism of an ultrasonic flaw detector which enables non-contact, stable and efficient signal transmission. .

[Means for Solving the Problems] In one aspect of the present invention, an ultrasonic flaw detection apparatus includes a probe, a flaw detection apparatus body, a rotating-side electrode connected to the probe, and the flaw detection apparatus body. And a flaw detection apparatus body side electrode connected to the flaw detection apparatus body side, and an adjusting member for adjusting a gap between the rotation side electrode and the flaw detection apparatus body side electrode. The rotating electrode connected to the probe is formed in a ring shape on the outer peripheral surface of the rotating shaft of the probe, and the flaw detection apparatus body side electrode is made of a flexible metal plate and has the ring shape. It is arranged in a bent state along the rotating-side electrode and is fixed to the flaw detector main body side through the adjusting member.

When the rotating-side electrode is rotated at a high speed by using the signal transmission mechanism of the ultrasonic flaw detector, an air flow is generated, so that the rotating-side electrode and the flaw-detector main body-side electrode are separated from each other. The signal is
It is transmitted through a capacitor composed of the rotating side electrode and the flaw detection apparatus body side electrode which are separated from each other.

[Operation] According to the present invention, the rotating-side electrode and the flaw-detecting-apparatus main body-side electrode face each other on the outer peripheral surface of the rotating shaft of the probe, and the air layer entrained when the rotating shaft rotates becomes the electrode interval, and the capacitor has a minimum clearance. Is formed, the accuracy of the gap is naturally ensured, and no interference occurs between adjacent capacitors.

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

<Structure of Embodiment> FIGS. 1 and 2 show the structure of a signal transmission mechanism of an ultrasonic flaw detector according to the first embodiment of the present invention.

As shown in FIG. 2, the ultrasonic flaw detector 10 has a base 11
A rotary shaft cylinder 13 is supported by bearings 12, 12, and the rotary shaft cylinder 13 is rotatably driven by a motor 14. The probes 15, 15 are integrally formed with the rotary shaft cylinder 13 at the end portion thereof. It is rotatably installed.

A guide cylinder 16 is integrally held at an end of the base 11, and the guide cylinder 16 guides the object W to be inserted into the probes 15 and 15. The guide cylinder 16 is inserted into the core hole 13a of the rotary shaft cylinder 13. There is.
The signal transmission mechanism 20 that connects the probes 15 and 15 to the flaw detection device main body (not shown) includes the intermediate portion of the rotary shaft cylinder 13 and the base 1.
It is provided between 1 and 1.

As shown in FIG. 1, the signal transmission mechanism 20 includes a rotary shaft cylinder 13
The rotating side electrode 30a and the flaw detecting apparatus body side electrode 40a wound around the rotating side electrode 30a face each other to form a hot side, and the rotating side electrode 30b and the rotating side electrode 30b are provided.
The electrode 40b on the main body of the flaw detection device, which is wound around, is opposed to form the ground side. It is usual that a hot side and a ground side are paired and a plurality of probes are provided according to the channels of the probes 15, 15.

The rotating-side electrodes 30a and 30b are formed in a rotating ring shape around the outer circumference of the rotating shaft cylinder 13 and are insulated from others. The rotating-side electrode 30a sends an exciting current to the probes 15 and 15 and transmits a signal. The core wire 21a of the coaxial cable 21 is connected, and the jacket wire 21b of the coaxial cable 21 is connected to the rotating-side electrode 30b.

Since the flaw detector main body side electrodes 40a and 40b have the same configuration, only one of them will be described, the same parts will be denoted by the same reference numerals, and the other description will be omitted.

The flaw detection apparatus body side electrode 40a is mainly composed of a flexible thin metal plate 41 (for example, a foil) around which the rotating side electrode 30a is wound, and the outer periphery of the thin metal plate 41 is covered with molybdenum disulfide which is an insulator. ing.

One end of the thin metal plate 41 is connected to the locking member guide cylinder 16 fixed to the base 11 via a connecting rod 42. The guide tube 16 and the thin metal plate 41 are insulated.

The other end of the thin metal plate is fixed to the probe main body side through an adjusting member for adjusting the gap between the rotating side electrode and the flaw detection apparatus main body side electrode. That is, one end of the tension spring 43 for tensioning is connected to the other end of the metal plate, and the tension spring 4
A connection bracket 44 is connected to the other end of the connection bracket 3, and a tension adjusting bolt shaft 44a fixed to the connection bracket 44 is attached to the locking member 17 fixed to the base 11 by a nut 44b,
They are connected by 44b.

<Operation of Embodiment> Next, the operation of the present embodiment configured as described above will be described.

The rotary shaft cylinder 13 is driven to rotate at a high speed by the motor 14, and the probes 15 and 15 are also rotated at the same time. The inspection object W is sent into the guide hole of the guide cylinder 16 and is flaw-detected when passing between the probes 15 and 15.

The rotation side electrodes 30a and 30b also rotate at high speed due to the rotation of the rotation shaft cylinder 13, whereby air is trapped between the rotation side electrodes 30a and 30b and the flaw detection apparatus body side electrodes 40a and 40b, and the electrodes 40a and 40b rise. , Rotating side electrode 3
0a, 30b face the flaw detection apparatus body side electrodes 40a, 40b with a minimum gap. An exciting current and a signal are transmitted to the coaxial cable 21 by the electrostatic capacitance generated during that time.

This gap is determined by the rotational speed of the rotating electrodes 30a, 30b and the tension of the tension spring 43. The tension of the tension spring 43 is determined by the bolt shaft 44a of the connecting bracket 44 and the nut 44.
It can be set to an appropriate one by changing the position with respect to the locking member 17 with b.

<Experimental example> According to the experiment embodying the present example, the outer diameter of the rotating side electrode 30a is 180 mm, the flaw detection apparatus body side electrode 40a is the phosphor bronze plate thickness for foil spring of 0.15.
mm, width 20 mm, 0.038 mm molybdenum disulfide coating, facing area; 56.52 mm capacitance; stop 1310 pF rotation 801 pF gap g, capacitance C, area S Then, g = 8.854 × 10 ² × S / C, including the thickness of the molybdenum disulfide layer, g = 0.038 mm at stop and g = 0.062 mm at rotation.

10 MHz due to the difference in capacitance between the above-mentioned stop and rotation
The difference in sensitivity is only about -1 dB, which is not a practical problem.

<Other Embodiments> FIGS. 3 to 5 show other embodiments, respectively.

In the structure shown in FIG. 3, the base portion 45 of the electrode 40a on the main body of the flaw detection device is fixed and the tip of the base 45 is rotated in the rotational direction.
0a, and the outer circumference of the flaw detection apparatus body side electrode 40a is
The flaw detection apparatus body side electrode 40a is pressed against the rotation side electrode 30a with an appropriate pressure by a damper spring 46 which is an adjusting member for adjusting the gap between the rotation side electrode and the flaw detection apparatus body side electrode.

FIG. 4 shows a damper spring 4 which is an adjusting member for adjusting the gap between the rotating side electrode and the flaw detection apparatus body side electrode by dividing the flaw detection apparatus body side electrode 40a into three parts.
It is designed to be pressed by 7, 47, 47. There is an advantage that the number of channels can be increased.

In FIG. 5, the guide rollers 48 and 48 for guiding the flaw detection apparatus body side electrode 40a to the outer circumference of the rotation side electrode 30a and the pressing roller 49 for pushing the flaw detection apparatus body side electrode 40a are shown.
And the guide rollers 48, 4 are installed at one place by winding the electrode 40a on the main body of the flaw detection device around these rollers.
8 and a sandwiching section 50 for sandwiching the flaw detection apparatus main body side electrode 40a, and the sandwiching section 50 is pulled by a spring 51 which is an adjusting member for adjusting the gap between the rotating side electrode and the flaw detection apparatus main body side electrode. The apparatus main body side electrode 40a is applied with tension.

[Effects of the Invention] As described above, according to the present invention, the rotating-side electrode and the flaw-detecting-device-body-side electrode are opposed to each other on the outer peripheral surface of the rotating shaft of the probe, and are opposed to each other with a minimum gap due to the entrained air. Since the temperature does not rise excessively even when the rotary shaft is rotated at a high speed and signals can be transmitted stably, the structure is simple and the number of components can be reduced, so that it can be implemented at low cost. There is no interference between channels.

[Brief description of drawings]

1 and 2 show one embodiment of the present invention,
FIG. 1 is a perspective view of an essential part of a signal transmission mechanism, FIG. 2 is a longitudinal sectional view of an ultrasonic flaw detector, and FIGS. 3 to 5 are explanatory views of a signal transmission mechanism according to other embodiments, and FIG. FIG. 8 is a longitudinal sectional view of a main part of a conventional transmission mechanism, FIG. 7 is an ideal model diagram of the conventional transmission mechanism, FIG. 8 is a practical model diagram of the conventional transmission mechanism, and FIG. 9 is a capacitance of C3 substantially. FIG. 10 is a characteristic diagram when the electrostatic capacitances of C1 and C2 are fixed and the electrostatic capacitance of C3 is changed. 10 ... Ultrasonic flaw detector, 11 ... Base 13 ... Rotation shaft cylinder, 15 ... Probe 20 ... Signal transmission mechanism 30a, 30b ... Rotation side electrode 40a, 40b ... Flaw detection apparatus main body side electrode 41 ...... Thin metal plate

Claims (1)

[Claims] 1. A signal of an ultrasonic flaw detector which has a flaw detector main body, a flaw detector main body side electrode connected to the flaw detector main body, a probe, and a rotation side electrode connected to the probe. In the transmission mechanism, an adjusting member for adjusting a gap generated during rotation of the rotating electrode is provided between the rotating electrode and the flaw detection apparatus main body side electrode, and the rotating electrode connected to the probe is A ring-shaped outer peripheral surface of the rotating shaft of the probe, wherein the flaw detection apparatus body-side electrode is made of a flexible metal plate, and is arranged in a bent state along the ring-shaped rotating-side electrode. A signal transmission mechanism for an ultrasonic flaw detector, which is fixed to the main body of the flaw detector through the adjusting member.