JPH073327B2 - Method and apparatus for automatic measurement of tubular products - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for automatically measuring various dimensions of tubular products such as small diameter and medium diameter pipes.

[Prior art and problems to be solved by the present invention]

It is necessary to measure whether the manufactured pipe has an inside diameter, outside diameter, wall thickness, roundness, etc. within the allowable range.
For small and medium diameter tubes (outer diameter 20-250 mm), there was no other method than manual measurement using a micrometer and calipers.

However, such manual measurement has the following problems.

(I) The standard pass / fail must be determined by the Max and Min values, but it is difficult to reliably detect Max and Min.

(Ii) There is variability among measurers, and reproducibility is low even for the same person. In one study (5 people each measured 10 times), the outer diameter Max: 21.60-22.81 Min: 21.08-21.28 results.

(Iii) Since it is not possible to efficiently meet the online manufacturing speed, it is the actual situation that sampling inspection is the only thing that can be done, but in the case of small diameter pipes, it reaches 4000 P / Hr depending on the size, the sampling frequency decreases, and there is a problem in quality control. Becomes

(Iv) For the determination of the inner surface shape, for example, in the case of undercut, for the sake of convenience, the definition as shown in FIG. 7 cannot be avoided. That is, Max-Min within 15 ° including beads
= Uneven thickness of 0.40 mm or less is passed. However, with this method, it is impossible to differentiate between a steep shape and a relatively smooth portion. For example, when using as a drawn steel pipe,
Even if the thickness deviation value is within the allowable range, a sharp streak shape remains as a streak even after drawing.

(V) Regarding the so-called diaper-shaped shape as shown in FIG. 8, there are many Max of the outer diameter, and although it is different from a perfect circle, it is difficult to detect an abnormal value by the manual method. Is.

(Vi) Even with a tubular product having a so-called nose bend as shown in FIG. 10, accurate shape measurement cannot be performed.

(Vii) One of the practical uses of steel pipes is to insert a PVC pipe for lining into the steel pipe,
In this case, the conventional inaccurate Min value of the inner diameter cannot be guaranteed, so the inspection is carried out by a plug-through test as shown in Fig. 9, but the work is extremely troublesome and many types of plugs are used. I have to prepare.

As a means for automatically measuring various dimensions of the pipe, JP-A-58-160805 discloses that a laser displacement meter is moved relative to a large-diameter steel pipe to measure the shape and groove portion near the weld. A method for measuring the shape, Japanese Patent Laid-Open No. 63-58132, 58137 discloses an apparatus for measuring the shape of the inner surface of a pipe by an optical displacement meter that moves along the pipe axis and rotates around the pipe axis. ,
Japanese Utility Model Laid-Open No. 60-8810 proposes a device in which a turning arm is provided so as to face the end surface of the pipe, and a distance sensor is attached to the turning arm so as to be movable in the radial direction of the pipe.

However, these means are measurement of welds and grooves of large diameter pipes, or measurement of the inner or outer surface of the pipe,
It cannot be directly applied to automatic measurement of small-diameter and medium-diameter pipes that have different purposes and requirements.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an automatic measuring method for a tubular product and an apparatus thereof capable of accurately and quickly measuring various dimensions of small-diameter / medium-diameter pipes. To do.

[Means for Solving the Problems]

In the method for automatically measuring a tubular article according to the present invention, as shown in FIG. 1, the outer surface side laser displacement meter 1A for detecting the displacement of the outer surface of the tubular article and the tubular article P are inserted into one measuring section. The outer side laser displacement meter by the optical path changing mirror 2
The inner surface side laser displacement meter 1B capable of detecting the displacement of the inner surface of the tubular product at the same position as the detection position in the circumferential direction of the tubular product of 1A is provided, and the outer surface side laser displacement meter is moved by moving this measuring unit.
1A and the optical path changing mirror 2 are positioned so as to face the outer surface and the inner surface of the tubular product P, respectively, and the measuring portion is swung about the central axis l of the tubular product P so that the laser displacement gauges 1A, 1B The detected displacement values over the entire circumference of the inner surface and the entire circumference of the outer surface of the laser are stored in the arithmetic processing unit 3 in association with the rotational position thereof, and in the arithmetic processing unit 3, the turning center O ′ of the laser displacement meter is detected from the detected displacement values and rotational position. Find the data string (x _i , y _i ) of the coordinate system with the origin as
A virtual center O of the tubular product is obtained from this data string (x _i , y _i ) by using the least squares estimation method of a circle, and an axis deviation value (a between the virtual center O and the turning center O ′ of the laser displacement meter is calculated. , b) is used to correct the data string, and the correction value is compared with an evaluation reference value to make a pass / fail judgment, or the measurement profile is displayed using the correction value. The correction values are the pipe outer diameter, the pipe inner diameter, the wall thickness, the maximum value, the minimum value, the roundness, which are obtained from the corrected data sequence (X _i , Y _i ) with the virtual center O as the origin.
Steepness.

Further, as shown in FIGS. 10 and 11, a plurality of outer surface side laser displacement gauges 1A are arranged in the axial direction of the tubular product P to form the tubular product P.
Of the virtual center O ₁ , O ₂ , at different positions from the pipe end of the pipe and the nose bend of the pipe end from the installation distance L of the laser displacement gauge on the outer surface, or using the nose bend angle θ ′. The correction data sequence (X _i , Y _i ) with O as the origin is corrected.

A specific example of the least squares estimation method for the circle is shown below, where:
A data string (x _i , y _i ) whose origin is the turning center O ′ is obtained from displacement detection values (raw data) from the laser displacement meters 1A and 1B. The distance from the turning center O ′ to each laser displacement meter 1A, 1B (zero point of displacement detection value) is obtained by detecting the displacement position of the laser displacement meter 1A, 1B, that is, the measuring unit in the radial direction of the tubular product with a linear sensor or the like. To be

The data string (x _i , y _i ) i = 1, ..., N is approximated by (xa) ² + (yb) ² = r ² (1) to obtain a, b, r. To do this, L = Σ [(x _i
-a) ² + (y _i -b) ² −r ² ] ² can be determined by determining a, b, and r that are the minimum.

That is, Reduce to solving the algebraic equation of. These equations can be simplified as follows.

Σ [x _i (x _i -a) ² + x _i (y _i -b) ² −x _i · r ² ] = 0 ...
(2 ′) Σ [y _i (x _i -a) ² −y _i (y _i -b) ² −y _i · r ² ] = 0
(3 ′) Σ [(x _i −a) ² + (y _i −b) ² −r ² ] = 0 (4 ′) The data string (x _i , If y _i ) is subjected to coordinate conversion, a correction value (X _i , Y _i ) in a coordinate system with the virtual center O of the tubular product as the origin can be obtained.

Further, for a steep shape as shown in FIG. 7, it is possible to determine the pass / fail by using the correction value to obtain (maximum value-minimum value) within an angle of 5 °, for example. The raw data (displacement detection value) can be used for evaluation by the following multipoint moving average method.

The moving data is averaged with different orders, and the difference is calculated.

The raw data R (*) is calculated based on the general definition of difference Δ = R (i + M) −R (i−M). Usually, M = 1 is too close and the change is small, so M = 3 to 5 is selected.

Furthermore, for the shape with a bent nose as shown in FIG. 10 and FIG. 11, two laser displacement gauges 1 and 2 are used.
A, 1A is rotated in the tube circumferential direction, the virtual centers O ₁ and O ₂ of both a and b cross sections are determined by the CPU calculation, and the difference Δd ′ between the distances d _i ′ and d ₂ ′ from the reference is calculated as “nasal curve”. Value ".

Then, according to the nose bending value = Δd ′ thus obtained,
The angle (nose bending angle) θ ′ between the line connecting the virtual centers O ₁ and O ₂ and the reference is Ask in. Here, L is the distance between the first and second laser displacement gauges 1A, 1A.

Further, the accuracy of the shape is improved by correcting and calculating the shape of the cross section a (tube end) by this θ '. That is, the correction calculation r ² = [(xa) ² − (yb) ² ] cos θ ′ is performed, and the first
The correction data (X _i , Y _i ) that has been subjected to the axis deviation correction described above is corrected from the copy measurement shape shown in FIG. 3 to the corrected shape shown in FIG.

As an apparatus for carrying out the above-described method, as shown in FIG. 1 or FIG. 10, it is located in the radial direction outward of the tubular product P and detects the displacement of the outer surface of the tubular product in the axial direction of the tubular product. The same as one outer surface displacement detection position of the outer surface side laser displacement meter 1A by a plurality of outer surface side laser displacement meters 1A and an optical path changing mirror 2 which is located facing the end surface of the tubular product P and is inserted into the tubular product. A laser displacement meter 1B on the inner surface side capable of detecting the displacement of the inner surface of the tubular product at a position, and a measuring section equipped with these laser displacement meters 1A and 1B are movably mounted in the radial direction of the tubular product P, and the center of the tubular product A support member 4 rotatable about a turning center axis l'parallel to the axis l, a drive motor 5 for rotating the support member 4, and an inner circumference and an outer circumference of the laser displacement meters 1A and 1B. Captures displacement detection values over the range corresponding to the rotational position , The data string of the coordinate system with its rotation center O 'of the origin of the laser displacement meter from the displacement detection value and the rotation position (x _i, y _i) determine the minimum circle from the data sequence (x _i, y _i) The virtual center O of the tubular product is obtained using the square estimation method, and the data string is corrected using the axis deviation value (a, b) between the virtual center O and the turning center O ′ of the laser displacement meter, Further, the nose bend of the pipe end is obtained from the coordinates of the virtual centers O ₁ , O ₂ , ... at different positions from the pipe end of the tubular product and the installation interval L of the laser displacement meter on the outer surface side, or the nose bend angle θ'is used. Then, the one provided with the arithmetic processing unit 3 for correcting the correction data (X _i , Y _i ) whose origin is the virtual center O is used. In addition, as shown in Fig. 12, the inner side laser displacement meter
In order to ensure that the optical path changing mirror 2 of 1B can be inserted into the tubular product, a protection mechanism 19 including a laser displacement meter for detecting the presence or absence of an obstacle is provided facing the end surface of the tubular product P.

A commercially available laser displacement meter can be used as the outer surface side laser displacement meter 1A, but the commercially available laser displacement meter cannot be applied as it is because the inner surface side is limited by the inner diameter of the tube.
Therefore, by making the optical path changing mirror 2 project inside the tube and changing the optical path, it is possible to apply to a size of 15 A or more.

The drive motor 5 may be a servo motor and controlled by the rotary encoder 6, or a pulse motor may be used alone.

[Action]

One measuring unit, that is, the laser displacement gauges 1A and 1B is rotated about a rotation center axis l'which is substantially coincident with the center axis l of the tubular product P so that 1000 to 2000 detection points can be obtained by one rotation. The rotation control and the detection control are performed.

The displacement of the outer surface of the tube is taken into the CPU of the arithmetic processing unit 2 by the outer side laser displacement meter 1A, and the displacement of the inner surface of the tube is taken into the CPU by the inner side laser displacement meter 1B via the optical path changing mirror 3. FIG. 3 shows an example of raw data when 1000 measurement points are used.

The data string (x _i , y _i ) obtained from this raw data is processed by the method of least squares to correct the deviation from the central axis l, and the corrected value after this correction is displayed on the CRT, and the required result is displayed. Print out. FIG. 4 shows an emphasized figure in which the correction value is a pie chart, and it is possible to easily determine whether or not the measurement profile is within the allowable range. It goes without saying that the pass / fail judgment can be made by extracting the Max and Min values and comparing them with the evaluation reference value. In addition, the pass / fail judgment is also performed based on the nose bending value shown in FIG. Further, by correcting the correction data (X _i , Y _i ) using the nose bending angle θ ′, a more accurate result can be obtained.

Next, FIG. 5 shows the steepness of the inner surface calculated and displayed by using the above-mentioned multipoint moving average method, and the steep shape of the inner surface can be easily detected.

Further, regarding the rice ball shape, it is possible to differentiate it from a perfect circle by using the radius from the center of the virtual circle as shown in FIG. Further, even when a vinyl chloride pipe for lining or the like is inserted, it can be easily determined by the inscribed circle Min value whether insertion is possible.

〔Example〕

The one shown in FIGS. 1 and 2 is based on trigonometry,
Measurement range: 10 mm, resolution: 1 μm, accuracy: 10 μm, using a laser displacement meter 1 applied to small and medium diameter pipes with an outer diameter of 20 to 250 mm and a wall thickness of 2.00 to 10.0 mm. Total
1A is attached to the support member 4 such that its light projecting axis is in the radial direction of the steel pipe P and the inner surface side laser displacement meter 1B is such that its light projecting axis is along the central axis direction of the steel pipe P.

The laser displacement meter 1 includes a semiconductor laser 7, a linear array photodetector 8, a light projecting lens 9, and a light receiving lens 10.
In the inner surface side laser displacement meter 1B, the optical path changing mirror 2 is provided via the projecting piece 11 so that the projected laser beam is sequentially reflected by the mirror, the inner surface of the steel pipe and the mirror, and is received by the light detecting element 8. To

These laser displacement gauges 1A and 1B are attached to the support member 4 via a slide mechanism 12 so that the position adjustment with the steel pipe P in the radial direction can be performed.

In addition, the inner side laser displacement meter 1B (see FIG. 12) has a protection mechanism including a laser displacement meter that detects the presence / absence of an obstacle so that the optical path changing mirror 2 can be reliably inserted into the tubular article.
19 are equipped.

The protection mechanism 19 is arranged so that the laser light is emitted from the optical path changing mirror 2 at a position displaced by the distance t toward the steel pipe P side. Then, the laser light is transmitted in the tube axis direction to ensure that there is no reflection from obstacles such as tube meat, burrs, and chip remnants.
Check before inserting the optical path changing mirror 2.

The support member 4 is rotatably attached by a support frame 15 by means of a rotary shaft 13 and a cross roller bearing 14, and a servo motor 5 is connected to the rotary shaft 13. The support frame 15 is supported by a base 16 so as to be movable in the axial direction of the steel pipe, and is moved by an appropriate means so that the displacement can be measured at a position of about 5 mm from the end face of the steel pipe.

The base 16 can be moved up and down by an appropriate means, and is adjusted up and down according to the pipe size so that the steel pipe center axis 1 and the rotation center coincide with each other. Since the center deviation can be corrected, this adjustment can be performed easily and quickly. The steel pipe P is lifted and supported from the line position by a pipe receiver 18 which is vertically moved by a cylinder 17.

Next, an example of actual measurement is shown.

(1) Reproducibility The 80 A pipe was measured 10 times and its reproducibility was investigated. Table 1 shows the deviation (maximum value-minimum value) of the values measured 10 times.

(2) Correspondence with manual measurement results Manual measurement was performed with a micrometer (resolution 0.01 mm) in 8 directions of the pipe. Table 2 shows the correspondence of the average value results.

(3) Influence of deviation between the axis of the pipe to be measured and the center of rotation The deviation was corrected by data processing, but the effect was confirmed.

Further, FIG. 6 shows an example in which the measurement result of the automatic measurement of the present invention is printed out.

From the above, it was found that in the present invention, it is possible to perform measurement with a high efficiency of 1 minute / cycle (1P) and an error of 0.05 mm or less on the inspection online.

In addition, the data can be fed back to the upper process and reflected in the control of the upper process.

〔The invention's effect〕

As described above, according to the present invention, the displacements of the inner surface and the outer surface of the tubular product can be simultaneously detected by the laser displacement meter, and the displacement detection value is taken into the arithmetic processing unit in correspondence with its rotational position to correct the center deviation. However, the correction value and the evaluation reference value are compared and judged, or the measurement profile is displayed, so that various dimensions of the small diameter and medium diameter pipes can be detected with good reproducibility, accuracy, and speed.

Further, by disposing a plurality of laser displacement meters for measuring the outer circumference and measuring locations at different positions from the tube end, so-called "nose bending" can be measured to make a pass / fail judgment. Therefore, it is possible to obtain more accurate results by utilizing the data at the time of measuring the "nose bend" to correct the pipe end shape value measured at an angle with the pipe axis.

Furthermore, a protection mechanism consisting of a laser displacement meter that detects the presence of obstacles is provided so that the optical path changing mirror that can detect the displacement of the inner surface of the tubular product by the inner side laser displacement meter can be inserted securely into the tubular product. ing. Therefore, the pipe meat,
The optical path changing mirror can be surely inserted into the tubular product without being interfered with by obstacles such as burrs and cutting dust.

[Brief description of drawings]

FIG. 1 (a) is a schematic diagram showing an automatic measuring device according to the present invention, FIG. 1 (b) is a graph showing the relationship between the detected value and axis deviation correction, and FIG. 2 is the laser displacement on the inner surface side. Fig. 3 is a schematic diagram showing the meter, Fig. 3 is a graph showing raw data by a laser displacement meter, Fig. 4 is a circle graph showing a measurement profile by the correction value, Fig. 5 is a graph showing steepness, and Fig. 6 is a measurement result. 7 is a schematic diagram showing a conventional measurement example of the inner surface shape, FIG. 8 is a schematic diagram showing a measuring method of the diaper shape, and FIG. 9 is a schematic diagram showing a plug-through test. 10 and 11 are schematic views showing a method for measuring the shape of nose bend, FIG. 12 is a schematic view showing a protection mechanism, and FIGS. 13 and 14 are schematic views showing a shape correction state. 1A …… Laser displacement sensor on the outer surface 1B …… Laser displacement sensor on the inner surface 2 …… Optical path changing mirror 3 …… Computing device 4 …… Supporting member 5 …… Drive motor 6 …… Rotary encoder 7 …… Semiconductor laser 8 …… Linear array light detecting element 9 …… Projecting lens, 10 …… Receiving lens 11 …… Projecting piece, 12 …… Slide mechanism 13 …… Rotating shaft 14 …… Cross roller bearing 15 …… Supporting base, 16… … Base 17 …… Cylinder, 18 …… Pipe receiver 19 …… Protection mechanism.

Claims (4)

[Claims] 1. An outer surface side laser displacement meter for detecting displacement of an outer surface of a tubular article and a light path changing mirror inserted in the tubular article in one measuring section in the circumferential direction of the tubular article of the outer surface side laser displacement meter. An inner surface side laser displacement meter capable of detecting the displacement of the inner surface of the tubular product at the same position as the detection position is provided, and the outer surface side laser displacement meter and the optical path changing mirror are moved to the outer surface and the inner surface of the tubular product, respectively, by moving the measuring unit. In addition to positioning so as to face, the measurement part is rotated about the central axis of the tubular product, and the displacement detection values from the laser displacement meters over the entire inner surface and outer surface are calculated in correspondence with the rotational position. This data is taken into a processing device, and in this arithmetic processing device, a data string of a coordinate system whose origin is the turning center O ′ of the laser displacement meter is obtained from the displacement detection value and the rotational position. The virtual center O of the tubular product is obtained from the row by using the least squares estimation method of the circle, and the data row is corrected using the axis deviation value between the virtual center O and the turning center O ′ of the laser displacement meter, An automatic measuring method for a tubular article, characterized by comparing the correction value with an evaluation reference value to determine acceptance or rejection, or displaying the measurement profile using the correction value. 2. The automatic measuring method according to claim 1, wherein a plurality of outer surface side laser displacement gauges are arranged in the axial direction of the tubular product, and virtual centers at different positions from the pipe end of the tubular product.
Obtaining the nose bend at the tube end from the coordinates of O ₁ , O ₂ , ... And the installation distance L of the laser displacement meter on the outer surface, or correcting the correction data with the virtual center O as the origin using the nose bend angle θ ′. A method for automatically measuring a tubular product, characterized by: 3. A plurality of outer surface side laser displacement gauges located axially outward of the tubular article for detecting displacement of the tubular article outer surface, and located opposite to the end surface of the tubular article, An inner surface side laser displacement meter capable of detecting displacement of the inner surface of the tubular product at the same position as one outer surface displacement detection position of the outer surface side laser displacement meter by an optical path changing mirror inserted into the tubular product, and each of these laser displacement meters. The measuring unit provided is movably mounted in the radial direction of the tubular product, and the support member is rotatable about a central axis of rotation parallel to the central axis of the tubular product, a drive motor for rotating the support member, and The displacement detection values from the laser displacement meter over the entire circumference of the inner surface and the entire circumference of the outer surface are taken in correspondence with the rotational position, and the data of the coordinate system with the turning center O ′ of the laser displacement meter as the origin from the displacement detection value and the rotational position. Then, the virtual center O of the tubular product is obtained from this data string by using the least squares estimation method of the circle, and the data is obtained by using the axis deviation value between the virtual center O and the turning center O ′ of the laser displacement meter. The row is corrected, and the nose bend of the tube end is obtained from the coordinates of the virtual centers O ₁ , O ₂ , ... at different positions from the tube end of the tubular product and the installation interval L of the outer surface side laser displacement meter, or the nose. An automatic measuring device for tubular articles, comprising an arithmetic processing device for correcting correction data having an origin at an imaginary center O using a bending angle θ '. 4. The automatic measuring device according to claim 3, further comprising a laser displacement meter for detecting the presence or absence of an obstacle so that the optical path changing mirror of the inner surface side laser displacement meter can be surely inserted into the tubular article. An automatic measuring device for a tubular product, wherein a protection mechanism is provided so as to face an end surface of the tubular product.