JPS6269113A - Inspection instrument for surface of screw - Google Patents

Abstract

PURPOSE:To inspect the surface of a screw and to discriminate simply the position of a tube end by projecting and scanning luminous flux in the axial direction with respect to the tube on the end of which the screw is processed and catching reflected light from a screw part. CONSTITUTION:The titled instrument is provided with a follow-up mechanism to make a photodetector follow up a directional change of the reflected light from the screw part, a tube end photodetector 16 to photodetect rays of light deviated from the tube end and a signal processor. Then, a photodetection part is followed up with the follow-up mechanism to that the photodetection part catches the reflected light under a prescribed condition based on the output electrical signals from plural photodetectors 14l and 14r for follow-up provided at both sides of the photodetection part. Further, the luminous flux projected on the position exceeding the tube end is photodetected with the photodetector 16. Then, the reflected light from the screw part is caught with the photodetection part and the electrical signal which is converted photoelectrically from the light is subjected to binarization processing with a waveform shaper 21 and a pulse train obtained as the output of the shaper 21 is received to measure the pulse width with time width measuring instruments 24 and 25. The existence or nonexistence of a defect of the screw surface is decided based on the pulse width. Further, the output of the photodetector 16 is inputted to a deciding device 26 and used for deciding the existence or nonexistence of the defect of the screw surface.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an apparatus for inspecting the surface of threads cut into pipe ends.

[Prior art]

As a method for optically inspecting defects on the surface of a threaded portion, there is a method in which a beam of light is scanned in the axial direction, reflected light from the threaded portion is captured, photoelectrically converted, and the output signal waveform diagram is inspected. FIG. 6 is a schematic diagram showing the basic optical system of this type of surface inspection apparatus, and FIG. 7 is a waveform diagram of the output signal of the photoelectric element. In FIG. 6, °ζ61a is a threaded portion cut at the end of the steel pipe 61, G2. G2 supports the steel pipe 61 to be inspected and
This is a rotating roll for rotating the shaft. The steel pipe 61 is rotated by a rotating roll G2.62, and the projected radar light 64 is scanned in the axial direction of the steel pipe 61 from the light emitting means 63 in the axial direction of the threaded part 61a. Project to lI.

Then, the reflected light 65 from the threaded portion Gla is sent to the receiver 66.
The surface of the threaded portion 61a is inspected by detecting ζ and analyzing the photoelectric conversion output signal.

If the surface of the threaded part 61.1 is a normal round thread, the waveform will be constant as shown in Fig. 7(a), but if there is a surface defect in the threaded part 61.1, the corresponding part will be The reflected light is disturbed, and as a result, the corresponding signal waveform becomes a low-level abnormal waveform, as shown by the arrow in Figure 7. By detecting this, it is possible to extract the surface defect of the screw. .

[Problems that the invention attempts to solve]

Although it is possible to perform optical surface inspection of threads using the device described above, there are some practical problems when applying it to threads cut at the end of large-diameter seamless pipes such as oil country tubular goods. be.

Large-diameter seamless steel pipes such as oil country tubular goods are manufactured by hot rolling, so they have some bends. Moreover, the cross section may not be a perfect circle. When performing a C-inspection on the entire circumference of a thread cut at the end of such a tube, as the tube rotates, the angle of the projected light to the threaded portion changes, and the angle of reflection from the threaded portion also changes. However, since the light receiver of the above-mentioned device is fixed, it cannot follow the changes in the reflected light in the six directions, and if the light receiver cannot accurately capture the reflected light, it may misidentify it as a defect signal. There was a problem.

Furthermore, since there is no means for accurately determining the position of the tube end, there may be no reflected light because the projected light has deviated from the tube end, or there may be no reflected light because the projected light is scattered due to the presence of a defect. It was difficult to determine the 'PI'.

Furthermore, photoelectric conversion is performed (the resulting signal waveform exhibits a complex waveform, so it was not easy to extract defects from this complex waveform).

[Means for solving problems]

The present invention has been made in view of the above circumstances, and its purpose is to project and scan a beam of light in the axial direction onto a tube with a screw threaded at its end, and to detect the reflected light from the threaded portion. The device that detects the light, processes the signal, and inspects the surface of the screw is equipped with a mechanism that makes the receiver follow the change in the direction of the reflected light from the thread, and a receiver that receives the light that deviates from the tube end. By being equipped with a signal processing device, it is possible to inspect the surface of threads cut into non-straight pipes such as large-diameter seamless pipes, and the position of the pipe end can be easily determined, and defect signals can be discriminated. The object of the present invention is to provide a screw surface inspection device that is easy to use.

The thread surface inspection device according to the present invention scans a light beam in the axial direction of a pipe with a thread machined at the end of the pipe, captures the reflected light from the threaded part in the light receiving part, and converts it into a photoelectric sensor. In an apparatus that processes converted electrical signals and inspects the surface of a a tracking mechanism that causes a light receiving section to follow the reflected light so as to capture the reflected light under a certain condition C; a tube end receiver that receives the light beam projected to a position beyond the tube end; and a waveform shaper that binarizes the electric signal. and a time width measuring device for receiving the pulse train obtained as the output of the waveform shaper and measuring the pulse width; It is characterized by what was done to judge.

〔Example〕

The present invention will be described below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram of an inspection head section according to the present invention, and FIG. 2 is a block diagram of the present invention. In Fig. 1, there is a threaded portion 1 at the end of the tube. A steel pipe to be inspected that has been processed; 2.
Reference numeral 2 denotes a rotating roll for supporting the steel pipe 1 to be inspected and rotating it around the ζ axis. The steel pipe 1 to be inspected is transported to an inspection device equipped with a plurality of pairs of rotating rolls 2, 2, and subjected to a C-thread inspection.

An inspection head storage box 4 is provided at the bottom of the steel pipe 1 to be inspected, and the bottom of the inspection head storage box 4 has an area approximately half of the bottom of the box 4. There is a long rectangular opening 3 at the top. Inside the inspection head storage box 4, there is a radar tube 5 that emits a radar beam, a collimator lens 6 that adjusts the diameter of the beam, a mirror 7 that changes the optical path, and a constant speed that keeps the angular velocity of the beam constant. A rotating vibrating scanner 8, an F-θ lens 9 for keeping the linear velocity of the light beam constant at the threaded portion 1a, and a reflecting mirror 1O for changing the optical path.
is provided.

The laser tube 5 and the collimator lens 6 are arranged so that their optical axes coincide with each other, and the beam emitted from the laser tube 5 passes through the collimator lens 6 so that it has an optimal beam diameter on the back surface of the object to be inspected. . If the diameter of the beam is large, the detection ability for minute defects will be reduced.On the other hand, if the diameter of the beam is too small, the machining marks generated on the surface during screw machining will also disturb the reflected light, which will reduce the S/N ratio. decreases. In the case of inspecting a screw cut at the end of a steel pipe, the diameter of the luminous flux is approximately 100 μm.

The light beam that has passed through the collimator lens 6 is reflected by a mirror 7 provided in the direction of its advancing force, and its optical path is changed by 90°. The light beam whose optical path has been changed by the mirror 7 is reflected by the vibration type scanner 8 and scanned at a constant angular velocity. Next, the light beam is reflected by a vibration type scanner 8 and scanned at a constant angular velocity. Next, the light beam passes through an F-θ lens 9 provided in front of the vibrating scanner 8. F-theta lens 9
converts the linear velocity of the light beam on the surface to be inspected to be constant. The light flux that has passed through the F-θ lens 9 is reflected by the reflection &R1O, and is projected onto the threaded portion 1a while being scanned in the direction of the axial force of the screw from the bottom opening 3 of the inspection head storage box 4. In order to cover the entire length of the threaded portion 1a, the scanning range of the projected light is required from a position beyond the tube end to a position beyond the end of the threaded upward portion.

In order to increase the inspection density of the threaded portion, this scanning needs to be performed at a speed that is sufficiently faster than the circumferential movement i1+ caused by the rotation of the tube.

In the above manner, as shown by the arrow in FIG. The light is reflected by the reflecting mirror IO and projected onto the threaded portion 1a.

In addition, in the bottom opening 3 of the inspection head storage box 4, the tips of the optical fiber bundles 11 are arranged in a long rectangular shape in the axial direction of the steel pipe l. 12, and the proximal end of the fiber bundle 11 has a circular shape with a photomultiplier tube 13 for focusing.

Two tracking light receivers 14 jl and 14 r are fixed to both sides of the center of the main light receiver end 12 in the longitudinal direction. A bend following motor 15 is installed on the inner surface of the bottom of the head storage box 4. A screw 7 is coaxially fixed to the output shaft of the bend following motor 15, and a moving shaft 18, one end of which is fixed to the main receiver end 12, is screwed perpendicularly to the screw 17. The main receiver ends 12 are connected to each other, and the main receiver end portion 12 moves within the opening 3 to both sides in the width direction thereof by the driving rotation of the bend following motor 15.

Furthermore, for the purpose of detecting the position of the tube end, a tube end receiver is placed below the steel tube slightly beyond the frontmost position that the tube end may reach when the tube end moves in the axial direction due to conveyance. 16 are provided.

Next, based on Fig. 2, we will explain the tracking mechanism of the inspection head section.
explain. The reflected light of the luminous flux irradiated onto the threaded portion 1a passes through the optical fiber bundle 11 from the main receiver end 12 and enters into the photomultiplier tube 3. Here, if the pipe end of the steel pipe 1 to be inspected is not straight, the direction of the reflected light changes, and the two tracking light receivers 141° 14r fixed on both sides of the center in the longitudinal direction of the main receiver end 12 There will be a difference in the amount of light received. The amount of light received by the tracking receivers 1, B, and 14r is transmitted to the comparison amplifier 30, and both tracking receivers 1411 and 14r
There is a configuration in which the bend following motor 15 is driven based on the difference in the amount of received light r.

This moves the main receiver end 12 to both sides in its width direction.

For example, the amount of light received by the tracking receiver 1i is different from the amount of light received by the tracking receiver 14r.
If the amount of light received is greater than the amount of light received by the following light receiver 14j of the main receiver end 12, the reflected light reaches the following light receiver 14j! Since the curve is biased to the side, the curve following motor 15 is driven and both the following light receivers 141
, 14r, the main receiver end 12 is moved toward the tracking receiver 14r so that the amount of light received by each of the receivers 14r becomes equal. Follow °
ζ Even if the steel pipe to be inspected l is bent, the reflected light can be reliably captured by the tracking mechanism described above.

Next, the function of the tube end light receiver 16 will be explained. When scanning the luminous flux in the axial direction and projecting it onto the °C screw portion 1a, the tube end receiver 16 is disposed at a position beyond the tube end, so
When the light beam leaves the tube end, the tube end receiver 16 receives the scanned light beam. The output of the tube end light receiver 16 is input to a determining device 26, which will be described later, and is used to determine the presence or absence of a defect.

That is, by using the presence or absence of light reception by the tube end light receiver 16, if the tube end light receiver 16 is receiving light, a luminous flux is projected onto the threaded portion 1a. There is no need to misidentify this as a defect signal.

In Figure 3, (A) is a schematic diagram showing the shape of the thread of a buttress screw, and (B) is a schematic diagram showing the shape of the thread of a buttress screw, and (B) is a diagram of the photomultiplier tube 13 when a healthy buttress screw is subjected to "ζ inspection" in the optical system shown in Figure 1. The signal waveform diagram (1) is the signal waveform diagram shown by the broken line in (A)'!l, which is binarized at the threshold level.
is a signal waveform diagram of the photomultiplier tube 13 for a typical defect in Buff 1 Helles Kaya, (O) is the signal waveform FgJ
is shown by the broken line in (1) - J threshold level 2 (represents the pulse train obtained by converting into It is roughly divided into low level signals such as C. Therefore, a defect can be detected by detecting the signal change shown in Fig. 3 (1). "The time width (T1 (hereinafter referred to as II width and abbreviated as J) at the level (Fig. 5) and the pulse are "
1. It is possible to detect that the time width in Luher (TL in FIG. 5, hereinafter referred to as I-width and approximately 1) is smaller than a predetermined value. The signal b can be detected by the pulse l (width smaller than a predetermined value) in the pulse train (o) and the width of 1 being larger than a predetermined value. It can be detected if it is larger than a predetermined value.

Similarly, in Figure 4, °ζ (force) is a schematic diagram showing the shape of the thread of a round screw, and (t) is a photoelectronic monk when a healthy round screw is inspected with an optical system (not shown in Figure 1). tube 1
3 signal waveform diagram, (ri) is a pulse train obtained by binarizing the signal waveform diagram at the bottom level with a broken line in (g), and (ke) is a photoelectronic monk tube 13 for a typical defect in a round screw. The signal waveform diagram (C) represents the pulse train obtained by binarizing the signal waveform diagram at the dark value level shown by the broken line in (C).

Here, the difference between the waveform shown in FIG. 4(g) and the waveform shown in FIG. 7 is based on the difference in the angle at which the light beam is irradiated. In other words, when the angle formed with the normal to the screw surface is approximately the same as shown in Figure 6, the difference in radius between the thread crest and the trough is large, so the reflected light from each part goes in different directions. The light receiver receives signals from only the threaded portion, as shown in FIG. 7, for example.

The defect signals in FIG. 4(e) are roughly divided into dip signals such as d, signals with a reduced pulse width on one side such as e, and signals with reduced pulse widths on both sides such as f.

Therefore, defects can be detected by detecting the signal changes shown in FIG. 4(e). A signal like d is a pulse train (
The signal e can be detected when the pulse 0 width and 12 width in the pulse train (g) are smaller than the predetermined value (tA).The signal e can be detected when the pulse 0 width and the L width in the pulse train
It can be detected by being larger. The f signal can detect that the pulse H62 in the pulse train (a) is smaller than a predetermined value and that the L width is larger than a predetermined value.

As a result, the presence or absence of defects is inspected every time the signal changes from a to r by checking whether the L width and Lllg of the corresponding pulse to be inspected are within predetermined value ranges.

A second signal processing mechanism is installed to realize the above processing.
ζ will be explained based on the figure. The reflected light from the threaded portion 1a enters the photomultiplier tube 13 from the main receiver end 12 and undergoes photoelectric conversion. 21 in the figure is the signal waveform after photoelectric conversion (A)
22 is a positive edge detector that detects the rising edge of the binary waveform (2) or ↓, and 23 is the binary waveform (2). ) or (ri) negative electrode edge detector for detecting the falling edge of (ri), 24
is the time width from when the positive edge detector 22 generates the output to when the negative edge detector 23 generates the output (Fig. 5 T ++
), 25 is a time width measuring device that measures the time width (FIG. 5 TL) from the output generation time of the negative electrode edge detector 23 to the output generation time of the positive electrode edge detector 22;
26 receives the outputs of the time width measuring devices 24 and 25.

In FIG. 2, a predetermined value of the C pulse H width (upper limit T, . . .

Lower limit TH2), pulse 17, predetermined width value (-1, limit T,
The 1° lower limit TL2) is given to the determiner 26 in advance as a set value.

In such a configuration, the LI width and L width of a pulse train such as (e) or (e) are sequentially measured by time width measuring devices 24 and 25. The output TH of the time width measuring device 24 is taken into the timing judgment device 26 of the output generation of the negative pole top/7-stage detector 23, and is judged in magnitude between TH1+TH2, and whether the measured value is larger than THl or TH2 If it is smaller, a defect occurrence signal 27 and a signal 28 indicating pulse H width abnormality are output. Similarly, the output T of the time width measuring device 25 is taken into the determiner 26 at the timing when the output of the positive edge detector 22 is generated, and the magnitude is determined between 'rLl + 'rL2, and the measurement point 16 is determined. If it is larger than TLI or smaller than TL2, a defect occurrence signal 27 and a pulse L@1 signal 29 indicating abnormality are output. Therefore, defect determination is easy.

〔effect〕

As detailed above, in the present invention, a tracking mechanism is provided to follow the reflected light from the threaded portion 1a, so it is possible to detect surface defects in threads cut into a steel pipe whose pipe end is not straight. In addition, since the tube end light receiver is installed at a position beyond the tube end, the absence of reflected light from the threaded portion 1a will not be mistaken as a defect signal.Furthermore, it is possible to obtain a simple pulse signal as a signal waveform diagram. Therefore, the present invention has excellent effects such as being able to easily identify defective signals.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the inspection head according to the present invention, Figure 2 is a block diagram of the present invention, Figure 3 is a signal waveform diagram for a buttress screw, Figure 4 is a signal waveform diagram for a round screw, and Figure 4 is a signal waveform diagram for a round screw. Figure 5 is a schematic diagram showing the time width of the binarized signal.
FIG. 6 is a schematic diagram of a conventional inspection device, and FIG. 7 is a signal waveform diagram obtained by the device shown in FIG. l...Steel pipe 2...Rotating roll 5...Laser tube 6...Collimator lens 8...Vibrating scanner 9...F-θ lens 10...
Reflector 13...Photomultiplier tube 14/, 14
r...Following receiver 15...Bending following motor
lG...tube end receiver missing 3 Fig. 4 Mouth and ear 5 Fig. Time calculation T'7 Fig. z Fig. 6

Claims (1)

[Claims] 1. A light beam is scanned in the axial direction of a tube whose end is threaded, and a light receiving portion captures the reflected light from the threaded portion,
A device for inspecting the surface of a screw by processing an electric signal obtained by photoelectrically converting the photoelectric signal, which comprises: a plurality of tracking light receivers disposed on both sides of the light receiving section; a tracking mechanism that causes the light receiving section to follow the reflected light so that the light receiving section captures the reflected light under certain conditions; a tube end light receiver that receives the light beam projected to a position beyond the tube end; and a binarization of the electric signal. It is equipped with a waveform shaper and a time width measuring device that receives a pulse train obtained as an output of the waveform shaper and measures the pulse width, and is designed to determine the presence or absence of defects on the screw surface based on the pulse width. A screw surface inspection device characterized by: