JPS5910499B2 - Magnetic flaw detection equipment for steel cables using magnetically sensitive elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic flaw detection device for steel cables using magnetically sensitive elements for inspecting the damaged state of stationary steel cables and moving cables.

The steel cable magnetization methods used in conventional magnetic flaw detection devices for steel cables can be roughly divided into two types: a direct current method and an alternating current method.

In addition, as a method for detecting the extent of internal damage to steel cables,
(■ A method for determining the self-inductance of the coil, that is, the condition of the steel cable, by making a coil with the steel cable to be measured as the iron core and measuring the impedance drop when an alternating current is passed through the coil. (3) A method in which a type of transformer is formed with an iron core, and the degree of damage to the steel cable is detected as the induced voltage in the secondary coil.
The steel cable is strongly magnetized to near the saturation point by a detection coil using a direct current, and the steel cable is moved through the detection coil to detect the magnetic flux leaking to the outside from the damaged part of the steel cable. A system that can be considered a type of generator that obtains a signal voltage through relative movement with a coil.
(4) There is a method of detecting magnetic flux leaked to the outside from a damaged part of a steel cable using a magnetically sensitive element such as a Hall element or an SMD. FIG. 1 shows a magnetic flaw detection device according to the method (4) above, in which the steel cable 1 to be measured is excited almost to the saturation point by a permanent magnet 4, and a magnetic flux 5 is generated within the steel cable 1. .

If the steel cable 1 has a damaged point 6 such as a wire breakage, a leakage magnetic flux T is generated in a direction perpendicular to the axis of the steel cable, and the leakage magnetic flux 7
By the action of the magnetically sensitive element 8 such as a Hall element or an SMD, a voltage is induced in the magnetically sensitive element 8 or the resistance value of the magnetically sensitive element 8 is changed. This amount of change is amplified by a signal amplification device 9 connected to the magnetically sensitive element 8, and then recorded on a recording paper in a recorder 10 with a thermal pen or the like, so that the output waveform recorded on the recording paper Damage signals can be determined by

However, magnetic flaw detection devices applying the above principle have drawbacks such as low sensitivity and poor signal-to-noise ratio, and the devices are large and complex, requiring a high degree of skill in handling.

The only system currently in practical use is one that applies the principle (3) above, but in principle, this system requires that the steel cable be moved relative to the detection coil. Steel cables that are stationary or move at very low speed (
For example, it has the disadvantage that it cannot be applied to steel cables with a moving speed of 0.1 m/Sec or less.

Further, in the case of the conventional method (4), (a) the outer shape is affected by the pitch of the steel cable.

(Example) Since the detection sensitivity is affected by the relative positional relationship between the damaged area and the magnetically sensitive element, there are drawbacks such as being easily affected by lateral vibration of the steel cable. This invention provides the above (4)
Based on the basic principle of this method, steel cables are developed using magnetically sensitive elements that can conduct magnetic flaw detection of steel cables with high sensitivity, regardless of whether the steel cable is moving or stationary, and without being affected by the twist pitch or lateral vibration of the steel cable. The purpose of this invention is to provide a magnetic flaw detection device.

Next, the present invention will be explained in detail using illustrated examples.

2 to 5 show an embodiment of the present invention, in which a split holding cylinder 2 with a circular cross section made of a non-magnetic material such as synthetic resin is constituted by a pair of semi-cylindrical bodies 11, A plurality of locking pins 12 are integrally provided at one end in the circumferential direction of each semi-cylindrical body 11, and a plurality of engagement holes 13 are provided at the other end in the circumferential direction of each semi-cylindrical body 11. The holding cylinder 2 is assembled by inserting and fitting the locking pins 12 at the opposing ends of each semi-cylindrical body 11 into the engagement holes 13.

Magnetically sensitive elements 14A, 14B to 18A, 18B each consisting of a pair of SMD elements are fixed to one side of the outer surface of the holding tube 2 at positions dividing the circumference into five equal parts. On the other side, the magnetically sensitive elements 14A, 1
SMD in the same phase as 4B to 18A and 18B, respectively
Magnetically sensitive elements 19A, 19B to 23A consisting of pair elements of
, 23B are fixed, and the detector 3 is constituted by the holding cylinder 2, each magnetically sensitive element, and the protective cover 30.

Annular magnetic poles 24 arranged on both sides of the detector 3 are fixed to both ends of an iron core 26 around which an excitation coil 25 is wound, and the center of the detector 3 and the center of each magnetic pole 24 are on the center line of the steel cable 1. Further, the excitation coil 25 is connected to a DC power source, and the steel cable 1 is magnetically excited to near the saturation point.

According to the magnetic flaw detection device configured in this way, even if the steel cable 1 is moving at an extremely low speed (0.1 m/Sec or less), the damage state can be measured with a constant sensitivity regardless of the moving speed of the steel cable 1. If the steel cable is completely stationary, the detector 3 and the exciter can be moved in the length direction of the steel cable 1 by a guide roller or the like configured to be able to move the detector 3 and the exciter together along the steel cable 1. It is possible to measure the damage state of the steel cables by just using this method.

When performing magnetic flaw detection on a steel cable, the relative positional relationship between each magnetically sensitive element in the detector 3 and each strand of the steel cable is such that the detector 3 is at the same position 30 times during one relative rotation around the steel cable 1. take a relationship.

That is, since 360 intervals ÷ 30 = 12th place, the same positional relationship is taken every 12 rotations. From this, in order to reduce the effect of unevenness on the steel cable surface caused by the twist pitch of the steel cable 1, when the detector 3 makes one relative rotation around the steel cable, it is necessary to The more times there is a relative positional relationship, the better.

While the detector 3 rotates about 360 times around the steel cable, the number of times the magnetically sensitive element and the strand of the steel cable assume the same relative positional relationship is equal to the least common multiple of both.

This relationship is shown in Table 1. It is sufficient that the least common multiple of the number of wires and the number of strands of the steel cable is 10 or more.

From this, the number of strands is 2, 3, 4, 6, 8, 10.
The number of magnetically sensitive elements that can cover all of the steel cables is 5,
There are 7, 9, and 10 pieces. From a practical point of view, the smaller the number of magnetically sensitive elements, the easier the manufacture and the higher the reliability, so it is optimal to set the number of magnetically sensitive elements to five.

In addition, in order to offset the effects of changes in the relative positional relationship between the magnetically sensitive element and the steel cable, the distance between adjacent magnetically sensitive elements in the axial direction of the holding cylinder is set to approximately 10 to 30W! It is preferable to set it to I. FIG. 5 shows a circuit for amplifying magnetic changes captured by magnetically sensitive elements, 14A and 14B.
~23A, 23B are magnetically sensitive elements (SMD pair elements),
27 is a differential amplifier, 28 is a power supply, and 29 is a terminal for extracting magnetic changes to the outside, and a display device such as an oscilloscope is connected to this terminal 29.

Also, the same number is A. Items with the suffix B are magnetically sensitive elements (SMD pair elements) housed in the same case.
It is. According to the present invention, there is provided a magnetic flaw detection apparatus for steel cables, which includes an excitation means for exciting the steel cable with a DC magnetic field to the extent that the steel cable is magnetically saturated, and a leakage magnetic flux detection means for detecting leakage magnetic flux due to internal damage of the steel cable. , in this magnetic flaw detection device, the leakage magnetic flux detection means includes a holding tube 2 surrounding the steel cable 1.
and a magnetically sensitive element attached around the detector 3, and five magnetically sensitive elements are arranged at equal angular intervals around the circumference of the holding cylinder, and at equal angular intervals in the axial direction of the holding cylinder. Since the steel cables are arranged in multiple rows, magnetic flaw detection of the steel cables can be performed with high sensitivity using an economical device, without being affected by the twist pitch of the strands of the steel cables 1 or lateral vibrations, etc., and regardless of the speed of movement of the steel cables 1. The effect that can be achieved is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing a conventional magnetic flaw detection apparatus for steel cables using magnetically sensitive elements. 2 to 5 show a magnetic flaw detection device for steel cables using a magnetically sensitive element according to an embodiment of the present invention, in which FIG. 2 is a perspective view showing the whole, and FIG. 3 is a front view of the detector. , FIG. 4 is an exploded perspective view showing the detector with the protective cover removed, and FIG. 5 is an enlarged circuit diagram. In the figure, 1 is a steel cable, 2 is a holding cylinder, 3 is a detector, 11 is a semi-cylindrical body, 12 is a locking pin, 1
3 is an engagement hole, 14A, 14B to 23A, 23B are magnetically sensitive elements, 24 is a magnetic pole, 25 is an exciting coil, 26 is an iron core, 2
7 is a differential amplifier, 28 is a power supply, and 29 is an external signal output terminal.

Claims (1)

[Claims] 1. A magnetic flaw detection device for steel cables, which is equipped with an excitation means that excites the steel cable with a DC magnetic field to the extent that it is magnetically saturated, and a leakage magnetic flux detection means that detects leakage magnetic flux due to internal damage of the steel cable, and the leakage magnetic flux detection means The means has a detector 3 consisting of a holding cylinder 2 surrounding the steel cable 1 and a magnetically sensitive element attached around the holding cylinder 1, and five magnetically sensitive elements are arranged at equal angular intervals in the circumferential direction of the holding cylinder. Also, a magnetic flaw detection device for steel cables using magnetically sensitive elements, characterized in that a plurality of rows are arranged at intervals in the axial direction of the holding cylinder.