JPH0429410Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application The invention is applicable to the outer periphery of ferrous materials such as steel bars and steel pipes having a circular cross-sectional shape, and non-ferrous metal materials such as aluminum, copper and alloy bars and pipes. The present invention relates to a rotary flaw detection device that detects defects by electromagnetic induction (eddy current) flaw detection, leakage magnetic flux flaw detection, or the like.

Conventionally, in order to detect defects on the surface of a material to be inspected having a circular cross section, the material to be inspected is transported in the axial direction and a sensor is rotated at high speed along the outer periphery of the material to be inspected. Flaws are detected using a spiral scanning trajectory around the outer circumference of the test material. At this time, the smaller the lift-off (distance) change between the inspected material and the sensor, the more reproducible and stable defect detection ability can be obtained, and the smaller the absolute value of lift-off, the more sensitive it is to detect minute defects. It has been known. However, not only does the material to be inspected have a bend or a difference in diameter, but also mechanical vibrations are applied during transportation, which inevitably causes changes in the lift-off between the material to be inspected and the sensor. Therefore, in conventional flaw detection equipment, in order to restrict the passage center position of the inspected material as much as possible and to suppress mechanical vibrations, inlet guide sleeves are installed immediately before and after the rotating sensor in the traveling direction of the inspected material. In addition to providing an exit guide sleeve, the hole diameter value of the sleeve is very closely approximated to the outer diameter of the material to be inspected to greatly limit the amount of vibration amplitude of the material to be inspected, and the rotation sensor is made non-contact to reduce the amount of lift-off change. We aim to reduce the
Efforts were made to keep the lift-off value constant by using a contact shoe or mechanical roll on the sensitive part of the rotating sensor.

An example of such a conventional rotary flaw detection device will be described with reference to FIGS. 6 and 7 of the accompanying drawings. FIG. 6 is a schematic cross-sectional view of a rotary probe flaw detection mechanism of a conventional rotary flaw detection device, and FIG.
FIG. 2 is a schematic diagram of the rotating disk section on the front side of the rotating probe flaw detection mechanism shown in the figure. This conventional rotary probe flaw detection mechanism 100 is fixed to a base plate 101 and has a bearing 10.
It is equipped with a rotating disk 104 supported by 2 and 103. This rotating disk 104 is rotated by applying a rotational force to a rotational drive pulley 105 from the outside via a V-belt or a timing belt (not shown). Further, the rotary disk 104 is provided with a signal transmission slip ring 106, and the external fixed frame 108 is provided with a signal transmission brush 107. Electric power and electrical signals can be exchanged through rotating contact with the device. The rotating disk 104 includes an exciter 1 for generating leakage magnetic flux in the defective part of the test material.
09, and a sensor for defect detection (for example, a probe coil or a magnetically sensitive element such as a Hall element) 1
10 are provided. The exciter 109 includes an exciting coil 109A and an exciting magnetic pole 109B. Power is supplied to the exciter 109 and signals are exchanged with the sensor 110 using the signal transmission slip ring 106 and the signal transmission brush 1, as described above.
07.

These rotating disks 104, exciter 109,
Since the relationship with the sensor 110 is clearly shown in the front view of FIG. 7, it will be described below with reference to FIG. The inspected material 10 is made to travel straight in a direction perpendicular to the paper plane of FIG. 7, and the rotating disk 104 is rotated clockwise or counterclockwise. Two exciters 109 are disposed on the rotating disk 104 so as to surround the material 10 to be inspected, and each excitation magnetic pole 109B is arranged close to the outer peripheral surface of the material 10 to be inspected. These exciting magnetic poles 109B are C
An annular or U-shaped body that is made of materials for forming magnetic circuits, such as magnetic yoke for DC leakage magnetic flux testing, magnetic steel plate laminates for AC leakage magnetic flux testing, and electromagnetic induction (eddy current). ) For flaw detection, it is made of a suitable material depending on the frequency of the applied excitation magnetic flux, such as a laminate of electromagnetic steel sheets or a ferrite core. In addition, the excitation magnetic pole 109B includes an excitation coil 1
A plurality of excitation coils 109A are each wound around each exciter 109.
are connected in series or in parallel so that the magnetic fluxes leaking to the outside from the open end of the excitation magnetic pole 109B strengthen each other. As described above, the open end of the excitation magnetic pole 109B is arranged to face the circumferential surface of the material to be inspected 10,
At that time, the mutual gap is several mm, and the inspected material 10
When the test material is conveyed in a direction perpendicular to the paper plane of FIG. 7, the excitation magnetic pole is prevented from being mechanically damaged due to the bending, roundness, etc. of the test material.

The exciter 109 is coupled to a size adjustment mechanism 111, and the size adjustment mechanism 111 is provided with a size adjustment knob 111A. Exciter 1
09 can be moved in the direction of arrow A by rotating and adjusting the size adjustment knob 111A. This size adjustment mechanism 111
When the outer diameter of the test piece is changed, that is, the present mechanism can be used for various materials to be inspected having different outer diameters. Size adjustment mechanism 111
A sensor support rod 112 is mechanically coupled to the
A pivot 113 is attached to the tip of this sensor support rod 112.
A movable arm 114 is provided so as to be able to rotate around this pivot 113. An exciter 1 is attached to one end of this movable arm 114.
A sensor 110 is coupled and fixed so as to be located in the centripetal direction of the inspected material 10 from the open end of the inspection target 10 . A balance weight 115 is attached to the other end of the movable arm 114. In this case, when the rotating disk 104 rotates, for example, clockwise, the sensor 110 and the balance weight 115 are adjusted so that the balance weight 115 is appropriately balanced.
15's weight has been adjusted. And sensor 1
10 and the circumferential surface of the material to be inspected 10 are brought into mechanical profiling contact using a contact shoe or the like.

Problems to be Solved by the Invention In the conventional rotary probe flaw detection mechanism as described above, the sensor and the circumferential surface of the material to be inspected are in mechanical contact with each other. The sensor 110 may temporarily jump due to irregular or unexpected mechanical vibrations in the vertical or horizontal direction of the material to be inspected, and the vibration may generate a false defect signal, or the sensor 110 may cause the material to be inspected to jump. There was a problem that the flaw detection function deteriorated while separated from the target. Furthermore, since the sensor is in constant contact with the surface of the material to be inspected, it is subject to wear, making it difficult to maintain a long sensor life, and causing problems such as the need to replace the contact shoe. Moreover, in this industrial field, there is an increasing demand for improved flaw detection accuracy and throughput, and therefore, to improve flaw detection accuracy, lift-off changes must be further suppressed, and In order to improve processing capacity, it is becoming necessary to increase the rotational speed of the sensor and increase the flaw detection scanning speed. However, like the conventional mechanism mentioned above,
Contact shoes and tracing rolls are constantly in contact with the material to be inspected, which can damage the surface of the material to be inspected, generate heat due to friction, and generate false defect signals due to mechanical vibration that accompanies contact. Due to these problems, there is a limit to increasing the flaw detection peripheral speed (flaw detection relative speed) by increasing the rotation speed of the sensor.

Therefore, an object of the present invention is to solve the problems of the prior art as described above and to provide a rotary flaw detection device that can perform flaw detection with high accuracy even at high speeds without shortening the service life.

Means for Solving the Problems According to the present invention, a rotary disk that rotates around the central axis of a material to be inspected having a circular cross section, and a sensor attached to the rotary disk are provided. In a rotary flaw detection device that detects defects on the surface of the material to be inspected by rotating the sensor around the material to be inspected by rotating a disk, the sensitive part of the sensor faces the surface of the material to be inspected. a sensor holder that holds the sensor in a manner that allows the sensor to be inspected and has an opening capable of ejecting high-pressure fluid onto the facing surface of the object to be inspected; a mounting member for mounting the holder; a high-pressure fluid supply means for supplying high-pressure fluid to the opening of the sensor holder; and a restraining force applying means applied to the holder so that the sensitive part of the sensor is held close to the surface of the inspected material, and the mounting member is a support rod having one end attached to the rotary disk. and a movable arm having an intermediate portion pivotably attached to the other end of the support rod, the sensor holder being attached to one end of the movable arm, and the high pressure fluid supply means comprising: It includes a fluid passageway up to the rotary disk and a flexible pipe that fluidly connects the fluid passageway and the opening of the sensor holder, and the suppressing force applying means is attached to the other end of the movable arm. and a shock absorber associated with the other end of the movable arm.

Next, the present invention will be described in more detail with regard to embodiments of the present invention based on FIGS. 1 to 5 of the accompanying drawings.

FIG. 1 is a schematic cross-sectional view similar to FIG. 6 showing a rotary flaw detection device as an embodiment of the present invention, and FIG. FIG. 7 is a schematic diagram similar to FIG. 7; 1st
In Figures 6 and 2, the above-mentioned Figures 6 and 7
Parts that are similar to the conventional device shown in the figures are designated by the same reference numerals and will not be described again, and only the improvements made by the present invention will be described in detail below.

In the rotary flaw detection apparatus 200 according to this embodiment of the present invention, air passages 202 and 203 are formed in the rotary drum 201 provided on the left side of the rotary disk 104. Furthermore, on the left side of the external fixing frame 108,
An air passage forming body 204 is provided, and air passages 205 and 206 communicating with air passages 202 and 203, respectively, are formed in this air passage forming body 204. Air seals 207, 208, and 209 are provided between the air passage forming body 204 and the rotating drum 201 for air sealing. Air passages 202 and 203 and air passage 2
05 and 206 refer to rotating disk 1 from the external fixed frame.
The air supply path up to 04 is configured.

FIG. 3 is a perspective view showing the detailed structure of the rotating drum 201. As clearly shown in FIG. 3, an annular groove 210 is formed in the rotating drum 201 at a position always facing the air passage 205. , an annular groove 211 is formed at a position always facing the air passage 206. The depth of the annular groove 210 is greater than the depth of the annular groove 211. Air passage 20
2 has one end opened 202A in the side wall of the annular groove 210.
and the other end is opened 202 at the right end of the rotating drum 201.
The air passage 203 is formed through the circumferential wall of the rotating drum 201 as shown in FIG. , are formed through the peripheral wall of the rotating drum 201.

The opening 202B of the air passage 202 is connected to a flexible air hose 21 as clearly shown in FIG.
0 and is connected to one end 210A of the air passage 20.
The opening 203B of No. 3 is connected to one end 211 of a flexible air hose 211 as clearly shown in FIG.
It is communicated with A.

The other ends 210B and 211B of each of the air hoses 210 and 211 are connected to one end of an air passage (not shown) of a sensor holder 213 holding a sensor 212, respectively. The air passage of the sensor holder 213 is open at a position facing the surface of the material to be inspected 10, and high pressure fluid can be ejected therefrom. These sensor holders 213 are attached to one end of a movable arm 114 movable around a pivot 113 and hold the sensing portion of the sensor 212 so as to face the surface of the material 10 to be inspected.

A piston rod 214A of a shock absorber 214 is coupled to the other end of the movable arm 114 near a balance weight 115 provided there.
is fixed to the support rod 112.

Compressed air is supplied to the air passages 205 and 206 from the outside, and the supplied compressed air is supplied to the air passages 202 and 203 and the air hoses 210 and 21.
1 and the air passage of the sensor holder 213, and is ejected from an opening (not shown) of the sensor holder 213 facing the surface of the inspected material 10. This air jet causes the surface of the inspected material 10 and the sensor 2 to
A gap between the sensor and the sensing section 12 is maintained. On the other hand, by adjusting the balance weight 115, the above-mentioned gap caused by the ejected air is kept as small as possible, and the movable arm 114 and the balance weight 115
In order to flatten the transfer function, mechanical excessive vibrations are absorbed by the operation of shock absorber 214. In this embodiment, the shock absorber 214 is a double-action cylinder oil damper using high viscosity oil and an orifice (relief groove), but the mass of the moving parts around the sensor is small and mechanical resonance is used. If designed to be outside the area, seismic rubber may be used instead.

The rotary flaw detection device 200 of this embodiment of the present invention is as follows:
Although the structure is as described above, in order to perform flaw detection with this device 200, the material to be inspected,
For example, a material to be inspected 10 having a finite length such as a steel pipe or a steel bar is rotated at a constant speed by a roller conveyor or the like through the center opening 104A of the rotating disk 104 (see FIG. 2).
It is transported through the inside. At this time, the outer surface of the material to be inspected 10 is scanned in a spiral trajectory by the rotational action of the plurality of (two in the above embodiment) sensors 212 of the rotary flaw detection device 200, and the flaw detection is automatically performed. is to be carried out.

Next, in order to evaluate the ability of the non-contact sensor according to the present invention to follow the surface of the inspected material, a distance sensor was embedded in the sensor holder, and the sensor holder was rotated to measure the temporal change in the output of the distance sensor. When I recorded the results, I obtained results as illustrated in FIG. In Fig. 5, Δ ₀ indicates the minimum gap between the opposing surface of the sensor holder and the surface of the material to be inspected, which is 0.7 mm in this example, and Δ ₁ indicates the maximum variation width of that gap. In the example, 0.25mm
Met.

On the other hand, in order to compare with this, the results of investigating the temporal change in the gap between the sensor facing surface and the surface of the inspected material when using conventional mechanical contact are shown in the fourth section.
An example is shown in the figure. In FIG. 4, Δ ₂ indicates the gap between the sensor facing surface and the surface of the material to be inspected, that is, the maximum change in lift-off, and in this example, it was 0.5 mm. The measurement results shown in Figures 4 and 5 are based on the circumferential speed of the sensor of 1.8m/
The measurement results shown in FIG. 5 were obtained at an air pressure of 3.0 Kg/cm ² .

Results of the invention According to the rotary flaw detection device of the invention, the following effects can be obtained.

(1) As is clear from the comparison of the measurement results in Figures 4 and 5, with the device of the present invention, the amount of change in lift-off can be reduced to about half of that of the conventional one. Not only can changes in flaw detection sensitivity due to changes be suppressed, but also changes in S/N due to lift-off changes can be minimized to maintain high detection accuracy. In general, electronic circuit compensation for sensitivity due to lift-off changes is a common practice in the prior art, but it is difficult to compensate for the latter change in S/N due to lift-off changes using electronic circuits. The effect of reducing the absolute value of the amount of change in lift-off is significant.

(2) In this invention, the flaw detection sensor is levitated using fluid pressure such as air pressure or hydraulic pressure, so the sensor part does not come into mechanical contact with the material to be inspected.
It can have a long life without causing wear, and there is no risk of damaging the material to be inspected.

(3) In this invention, the mechanical braking action is activated by the physical viscosity of the fluid, so as shown in the measurement results in Figure 5, the flaw detection circumferential speed/flaw detection speed is 2.0 m/sec. Despite the high speed, there is little vibration, that is, the _Δ1 value, and smooth, stable, and reproducible flaw detection can be performed.

(4) In the present invention, the surface of the sensor facing the material to be inspected can be cooled by the cooling effect of the high-pressure fluid.
That is, when the high-pressure fluid is pressurized compressed air, when the compressed air is ejected from the fluid opening of the flaw detection sensor, its volume rapidly expands and increases, and the pressure also decreases. At this time, Boyle
Combined with the synergistic effect of lowering the temperature of the gas according to Charle's law, a cooling effect is obtained.
Due to such a cooling effect, automatic flaw detection is possible even if the outer surface of the ferromagnetic material to be inspected exhibits a high temperature, for example, 300°C or 800°C.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a rotary flaw detection device as an embodiment of the present invention, FIG. FIG. 4 is a perspective view showing the detailed structure of the rotating drum of the rotary flaw detection device shown in FIG. A diagram showing an example of recording the amount of change, FIG. 6 is a schematic cross-sectional view of a rotating probe flaw detection mechanism of a conventional rotary flaw detection device, and FIG. 7 is a schematic diagram of the rotating disk portion in front of the rotary probe flaw detection mechanism of FIG. 6. It is. 101...Base plate, 102, 103...Bearing, 104...Rotating disk, 105...Rotation drive pulley, 106...Slip ring for signal transmission,
107... Signal transmission brush, 108... External fixed frame, 109... Exciter, 109A... Exciting coil, 109B... Exciting magnetic pole, 111... Size adjustment mechanism, 111A... Size adjustment knob, 112
...Sensor support rod, 113...Pivot, 114...
Movable arm, 115...Balance weight, 20
0... Rotating flaw detection device, 201... Rotating drum, 2
02, 203... Air passage, 204... Air passage forming body, 205, 206... Air passage, 210,
211...Air hose, 212...Sensor, 21
3...Sensor holder, 214...Shock absorber.

Claims (1)

[Scope of utility model registration request] It is equipped with a rotary disk that rotates around the central axis of the material to be inspected having a circular cross section, and a sensor attached to the rotary disk, and by rotating the rotary disk, the sensor is attached to the material to be inspected. In a rotary flaw detection device that detects defects on the surface of the material to be inspected by rotating it around a a sensor holder having an opening capable of spouting high-pressure fluid on a facing surface of a material; a mounting member for mounting the sensor holder to the rotary disk in a manner that allows the sensor holder to float; A high-pressure fluid supply means for supplying high-pressure fluid to the opening; and a suppressing force that resists the reaction force of the ejecting force of the high-pressure fluid and the rotational centrifugal force to the sensor holder, so that the sensitive part of the sensor a restraining force imparting means for holding the inspection material close to the surface thereof, and the mounting member is pivotable to a support rod having one end attached to the rotary disk and the other end of the support rod. the sensor holder is attached to one end of the movable arm, and the high-pressure fluid supply means is provided with a fluid passage up to the rotary disk and a movable arm with an intermediate portion attached thereto, and the sensor holder is attached to one end of the movable arm, and the high-pressure fluid supply means and a flexible pipe fluidly connected to the opening of the sensor holder, and the suppressing force applying means includes a balance weight attached to the other end of the movable arm, and a A rotary flaw detection device comprising a shock absorber associated with the shock absorber.