JPS6343796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method and method for eliminating noise signals inherent in a rotating magnetic flaw detection device and extracting only pick-up signals corresponding to flaws in a test material detected by a detector. Regarding equipment.

Rotating magnetic flaw detection equipment detects flaws in the axial direction on and near the surface of magnetic metal materials such as steel bars and steel pipes, and uses the detection signals to mark the flaws or identify flawed test materials. This is a device that performs discrimination.

As shown in Figure 1 a and b, the principle is to rotate a magnet and a detection element around a specimen traveling in the axial direction, magnetize the vicinity of the surface in the circumferential direction, and due to the presence of flaws, the magnetic field lines A detection element detects that a portion of the liquid leaks to the outside. In this type of device, a slip ring is generally used to transmit and receive signals between the rotating body and the outside, as the principle is shown in FIG. 1a.

In FIG. 1a, the signal detected by the detection element 2 rotating around the specimen 1 passes through the slip ring 3 which rotates together with the detection element 2, and is delivered to the carbon brush 4 which is in sliding contact with the slip ring 3. The signal is transmitted and processed by the signal processing device 5.

Furthermore, since the power of the pick-up signal from the detection element 2 corresponding to a flaw on the specimen is generally very small, it must be amplified and conveyed. Power for amplification and transport for this must be sent from the outside using the slip ring 3 as well.

Furthermore, the number of detection elements is generally 4 to 8 in order to increase the inspection processing capacity, but when extracting signals from these elements to the outside, it is possible to provide the same number of slip rings, but the device becomes large-scale. become,
Furthermore, since the cost is high, it is common to perform time-division transmission and reception using a single slip ring.

Another slip ring is required to send a synchronization signal for this time-division transmission and reception to the inside of the rotating body.

FIG. 2 shows an example of this type of device. The test material 1 is held in the direction of the arrow by centering rollers 12 provided at the front and rear of the rotary magnetic flaw detection device so that the center axis thereof does not vary. Around it,
Detection element 2 and electromagnet 1 fixed to rotating body 13
4. The amplifier circuit 6 and the electronic switch 7 rotate together. The rotating body 13 itself is supported by a rotating body support frame 15.
It is held inside by a bearing 15' and is rotationally driven by a motor (not shown) via an appropriate transmission means. The slip ring 3 is a rotating body 13
The slip ring support frame 16 assembled integrally with the
It is fitted around the outer periphery of the The carbon brush 4 is attached to a carbon brush support 17 via a spring, and is in elastic sliding contact with the slip ring 3.
There are three slip rings and three carbon brushes each for extracting signal power to the outside, for transmitting amplification/carrier power to the inside, and for synchronously driving internal and external electronic switches for time-division transmission and reception. Each is used to send signal power.

In the above-mentioned apparatus, in addition to the pick-up signal from the detection element 2, various noise signals are generated within the apparatus, all of which are added to the pick-up signal and sent to the signal processing apparatus, thereby impairing flaw detection accuracy. In particular, a considerable amount of constant noise is generated between the slip ring and the carbon brush, and
A large noise signal may be suddenly generated, which is presumed to be due to foreign matter mixed in between the two. In particular, since the latter can easily be mistaken for a flaw signal, there has been a strong demand for countermeasures against such situations. However, in the past, most of the efforts to improve the noise have been aimed at preventing the generation of the noise itself, and until now no fundamental means for noise cancellation has been found.

The present invention provides a method for eliminating the above-mentioned drawbacks and obtaining highly accurate flaw signals by erasing all signals other than pick-up signals corresponding to flaws from a detection element, that is, carrier power accompanied by noise, and the method. The purpose is to provide a device for carrying out this.

The first invention of the present application is to provide a rotary magnetic flaw detection device with one extra line in addition to the number of detection elements when transmitting and receiving signals from the detection elements in a time-division manner.
Using this line, only the carrier power including noise is transmitted without inputting the pick-up signal from the detection element, and this signal is inverted and added to the signal from each detection element, or this signal is used as it is for each reproduction. This is a noise erasing method characterized by removing unnecessary components other than the pick-up signal from the signals reproduced by each detection element by passing the signals together with a differential circuit, and extracting only the pick-up signal, and the second invention of the present application is an invention of a device for carrying out the first invention, which mainly includes a rotating body formed by fixing a plurality of detection elements and a slip ring to a frame body, and a rotating body that supports the rotation of the rotating body. In a rotary magnetic flaw detection device consisting mainly of a support frame, a rotation drive device for a rotating body, a carbon brush in sliding contact with a slip ring, a time-division signal transmission/reception circuit, and a flaw signal processing circuit, the time-division transmission/reception line is By providing one extra line, only the amplified and carrier power is transmitted and regenerated, and the regenerated signal is added to each regenerated signal from each detection element with the phase reversed, or the phase remains the same and each regeneration signal from each detection element is added. This is a noise canceling device characterized by being provided with a phase inversion addition circuit or a differential circuit for subtracting from a reproduced signal.

Details of the noise erasing method and device according to the present invention will be explained with reference to FIG. A pick-up signal from the detection element 2 is amplified by an amplifier 6 and sent to an electronic switch 7 on a carrier power. on the other hand,
From the amplifier 6', only the amplified carrier power without carrying the signal from the detection element is sent, and also to the electronic switch 7.
to go into. These signals are also accompanied by noise contained in the amplification/carrying power supply.

These signals are then time-divisionally transmitted from electronic switch 7 through slip ring 3 and carbon brush 4 to electronic switch 7', where they are reproduced by reproducing circuits 9 and 9'. The signal reproduced here has additional noise added to it when it passes through the slip ring. Here, only the pickup signal can be extracted by subtracting the carrier power signal accompanied by noise from the reproduced signal containing the pickup signal corresponding to the flaw on the material to be inspected by each detection element. Therefore, the reproduction signal from the reproduction circuit 9' is reversed in positive and negative terms by the phase inversion circuit 10 and added to each reproduction signal, or is subtracted from each reproduction signal by a differential circuit. Thus,
Only the pick-up signal containing no base noise is transmitted to the signal analysis circuit 11, making it possible to identify flaws with high accuracy. In an actual device, level matching circuits and the like for each signal are required, but since they are not directly related to the idea of the present invention, their explanations are omitted.

Photos a and b in FIG. 4 compare the signal waveform obtained by the present invention with the signal waveform obtained when the present invention is not used, and it can be seen that noise has been clearly eliminated in photo a.

In conventional equipment, about 35% of the specimens separated because they were determined to have flaws were erroneously determined due to noise, but with the implementation of the present invention, the number of erroneous determinations has been reduced. This was almost completely eliminated, making it possible to reduce process disruptions and increases in man-hours due to misjudgments.

[Brief explanation of the drawing]

Figures 1a and b are diagrams illustrating the principle of a rotary magnetic flaw detection device, Figure 2 is a diagram illustrating an example of a device to which the present invention is applied, and Figure 3 is a block diagram illustrating the method and device according to the present invention. , FIGS. 4a and 4b are signal waveforms obtained by the present invention and the conventional method. DESCRIPTION OF SYMBOLS 1... Test material, 2... Detection element, 3... Slip ring, 4... Carbon brush, 5... Signal processing device, 6
…Amplifier, 7…Electronic switch, 8…Synchronization circuit, 9
...Waveform reproducing circuit, 10...Phase inversion circuit, 11...Signal analysis circuit.

Claims (1)

[Claims] 1. In a rotating magnetic flaw detection device, when transmitting and receiving signals from the detection elements in a time-division manner through a slip ring, an extra time-division line is provided in addition to the number of detection elements. After loading only the amplified and carrier power, which does not include the pick-up signal from the
A noise erasing method characterized by erasing from each reproduced signal produced by each detection element and extracting only the pickup signal produced by each detection element. 2. A rotating body mainly composed of a plurality of detection elements, a detection element fixing frame, and a slip ring;
The rotating body support frame that supports the rotation of the rotating body, the rotational drive device of the rotating body, the carbon brush that slides into contact with the slip ring, the time-division transmission and reception circuit for signals by the detection element, and the flaw signal processing circuit. type magnetic flaw detection equipment, by providing one extra line for time-division transmission and reception, by which only the amplified and carrier power is transmitted and regenerated, and the regenerated signal is added with phase inversion to each regenerated signal by each detection element, or 1. A noise canceling device comprising a phase inversion addition circuit or a differential circuit that eliminates all signals other than the pickup signal from each reproduction signal from each detection element by subtracting them while keeping the same phase.