JP2012093268A - Circularity measurement system and pipe-making device with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circularity measurement system which can measure circularity of a measurement object whose circular cross-sectional outer shape is circular in real time.SOLUTION: A circularity measurement system includes: light sources U1a-U4a which irradiate the surface of a measurement object T whose cross-sectional outer shape is circular and which continuously moves with linear light in the right-angled direction to the moving direction P, imaging means and U1b-U4b for picking up an irradiation region of the light in the measurement object T from the angle direction which is not right-angled to the conveyance direction P; and calculation means C for calculating the circularity of the cross-sectional outer shape of the measurement object T based on image information from the respective imaging means U1b-U4b, in which at least two sets of the light sources U1a-U4a and the imaging means U1b-U4b are provided, the two sets of light sources U1a-U4a and the imaging means U1b-U4b are arranged at equal angle intervals from each other regarding a center axis of the measurement object T when the sets are viewed from the direction going from the upstream to the downstream of the moving direction P of the measurement object T.

Description

  The present invention relates to a roundness measuring system and a pipe making apparatus equipped with the same, and more particularly, a system for measuring roundness of a member having a circular cross-sectional outer shape and a machining condition during pipe making using the system. The present invention relates to a tube forming apparatus that can be used.

  In the industry, there is a demand for a member (long member) whose cross-sectional outer shape is precisely circular. For example, a solid iron bar is mainly used as a material for a roller used in a printer or the like. However, there is a demand for replacement of a solid iron bar with a hollow pipe from the viewpoint of energy saving and resource saving during processing. For this reason, it is conceivable to create a hollow pipe-like roller with a pipe making apparatus using a tube mill line that forms a plate-like metal material into a circle.

  However, while the accuracy required for rollers used in printers is very high (roundness within 2/100 mm), in the case of forming with a general tube mill line, it is possible to achieve the accuracy so far. Virtually impossible. For this reason, it is necessary to realize a roundness precision measurement system and a pipe making apparatus capable of improving roundness, particularly over the entire length of a long pipe-shaped member.

  In view of the above problems, the present invention provides a light source that irradiates linearly light on a surface of a measurement object that has a circular cross-sectional outer shape and moves in a direction perpendicular to the movement direction, and the measurement object. The roundness of the cross-sectional outer shape of the measurement object is determined based on the imaging means for imaging the irradiation area of the light from an angle direction that is not perpendicular to the transport direction and image information from each imaging means. A calculating means for calculating, wherein at least two sets of the light source and the imaging means are provided, and the two sets of the light source and the imaging means are viewed from a direction from upstream to downstream in the moving direction of the measurement object; They are arranged at equiangular intervals with respect to the central axis of the measurement object. By taking the above configuration, it is possible to measure a circular shape over the entire circumference of the measurement object in real time.

  In addition, the present invention employs a configuration in which four sets of the light source and the imaging unit are provided and arranged at an angular interval of 90 °.

  In addition, the present invention adopts a configuration in which each set of the light source and the imaging means is arranged at a predetermined distance from each other along the moving direction.

  In the present invention, the calculating means calculates a partial circular shape from image information obtained from each imaging means, combines the partial circular shapes to calculate a circular shape, and based on the calculated circular shape. It has a configuration that determines the roundness and has each function.

  In the present invention, the calculation means plots each partial circle shape in a predetermined two-dimensional coordinate system when calculating the circular shape, and also calculates a partial circle based on the coordinate value of each point in the partial circle shape. Calculating the average curvature radius of the shape, calculating the center point coordinates of each partial circle shape based on the average curvature radius, and having a function of calculating the circle shape by matching the calculated center point coordinates; The structure is adopted.

  The present invention is also a pipe making apparatus comprising the roundness measuring system and a pipe making machine that is arranged upstream of the roundness measuring system and that manufactures the measurement object. The machine has a configuration of having a molding condition correction function for correcting the molding conditions based on the roundness information calculated by the roundness measurement system. By adopting such a configuration, based on the roundness information calculated by the roundness measurement system, it is possible to correct the molding conditions in real time in order to further improve the roundness. .

Moreover, this invention has taken the structure that the said molding condition correction mechanism is performed by correcting the position of the molding die with which the said pipe making machine is equipped.
In addition, the present invention adopts a configuration in which the molding die holds the measurement object in the vertical direction, the horizontal direction, the vertical and horizontal directions, and the oblique 45 ° direction.
Furthermore, the present invention employs a configuration in which the molding die can be corrected in position so as to rotate with respect to the central axis of the measurement object.

1 is a schematic perspective view of a roundness measurement system according to an embodiment of the present invention. It is explanatory drawing explaining computing a circular shape from the partial ellipse form obtained from four optical units. It is the schematic which shows the 1st set of optical unit and the image information obtained by this. It is a figure which shows the partial circular shape calculated based on the image information by each imaging means. It is a figure which shows the fluctuation | variation of the curvature radius in each angle position in each partial circle shape disclosed in FIG. It is a figure explaining the definition of roundness. It is a figure which shows a pipe making apparatus provided with the roundness measuring system of this invention, FIG. 7 (A) shows a top view, FIG.7 (B) shows a side view, FIG.7 (C) shows roundness. It is a figure explaining the sizing process for improving A, and FIG.7 (D) is a figure explaining a welding process.

  Next, a roundness measurement system according to an embodiment of the present invention will be described with reference to the drawings.

[Overview]
FIG. 1 is an overall schematic diagram of a roundness measurement system 1 according to the present embodiment. In this figure, the measuring object T is a circular pipe and continuously moves in the direction from the left to the right in the figure (the direction of arrow P in the figure). That is, a pipe making machine is arranged on the upstream side of the roundness measuring system 1.

  This roundness measurement system 1 includes four sets of optical units U1 to U4 and calculation means C that receives image information output from each of the optical units U1 to U4 and calculates roundness, specifically a computer. It has. Each of the optical units U1 to U4 includes light sources U1a to U4a that output linear light toward the surface of the measurement object T, and imaging means U1b to U4b that image light reflected from the surface of the measurement object T. ing. Here, the light sources U1a to U4a are laser light sources, and the imaging means U1b to U4b are CCD cameras. However, the light sources U1a to U4a and the imaging means U1b to U4b are not limited to these.

[light source]
Next, the light sources U1a to U4a will be described in detail. As described above, the light sources U1a to U4a output laser light. The laser beam that is actually output is fan-shaped, but is linear when the measurement object T is irradiated. Here, the laser beam is directed in such a direction as to cut the cross section of the measurement target T. In other words, the optical axis of the laser light is perpendicular to the moving direction P of the measuring object T, and the longitudinal direction of the linear light is also perpendicular to the moving direction P of the measuring object T. Referring to the X, Y, Z axis coordinate system in FIG. 1, for example, the optical axis of the light source U1a of the first set of optical units U1 is parallel to the Z axis, and the longitudinal direction of the linear light is the Y axis. It is parallel to. A technique for measuring the outer shape of the measurement target T using such a setting of the light source U1a is called a light cutting method.

[Imaging means]
Next, the imaging means U1b to U4b will be described. The imaging means U1b to U4b are CCD cameras, and can capture an area irradiated with laser light as an image. The optical axes of the imaging units U1b to U4b are arranged to be at an angular position inclined α ° (45 °) toward the moving direction P of the measurement target T from the optical axes of the light sources U1a to U4a. That is, the positional relationship is such that linear light formed on the surface of the measurement target T is imaged from an oblique 45 ° direction. Similar to the light sources U1a to U4a, using the X, Y, Z coordinate system in FIG. 1, the optical axis of the imaging means U1b of the first set of optical units U1 is 45 ° from the Z axis toward the X axis. It is in a tilted angular position and is parallel to the X axis. When the measurement target T is imaged using such an optical unit U1, the imaging means U1b can capture a partial elliptical reflected light image as shown in FIG.

[Other optical units]
The other optical units U2 to U4 have the same basic structure as the first set of optical units U1. However, the optical axis of the light source U2a of the second set of optical units U2 is parallel to the Y axis, and the optical axis of the light source U3a of the third set of optical units U3 is parallel to the Z axis and opposite to the first set of optical axes. Furthermore, the optical axis of the light source U4a of the fourth set of optical units U4 is parallel to the Y axis and opposite to the optical axis of the light source U2a of the second set of optical units U2. That is, each of the optical units U1 to U4 has a structure that images the measurement target T, which is a circular tube, from four directions at different angular positions, and can measure the entire surface of the measurement target T. In the present embodiment, due to restrictions on the arrangement of the optical units U1 to U4 of each set, the first set of optical units U1 to the fourth set of optical units U4, in order from the upstream side of the measurement target T. They are spaced apart from each other at a predetermined interval toward the downstream side. For this reason, in order to measure the roundness in a specific section, it is necessary to synchronize the measurement results of the optical units U1 to U4 with the movement of the measurement target T. Details of this point will be described later.

  In the above-described embodiment, four sets of optical units U1 to U4 are used, but the present invention is not limited to this. In other words, theoretically, two sets of optical units are used to irradiate light from two locations in the vertical and horizontal directions on the measurement object, and two images are captured by the imaging means. It is possible to measure a certain degree of roundness. In this case, the two sets of optical units are arranged at an angular position separated from each other by 180 °. However, since there is a possibility that many errors are included in the vicinity of both ends in the partial circle shape of the image, correction calculation processing that cancels this error is necessary. When three sets of optical units are used, the optical units are arranged at angular positions separated from each other by 120 °. Furthermore, when six sets of optical units are used, they are arranged at angular positions separated from each other by 60 °. That is, the number of optical units is not particularly limited as long as the number can be divided into 360 ° equally.

[Calculation means]
Next, calculation means C for calculating roundness will be described. The calculation means C is a computer as the most general example. As shown in FIG. 2, the calculation means C receives four pieces of image information (for example, partial elliptical shapes) 11a to 11d transmitted from the imaging means U1b to U4b, and converts them into partial circular data. It has at least a function and a function of synthesizing the converted partial circular shapes of the respective portions and converting them into circular data 12.

  The above will be described in more detail. FIG. 3 is a diagram illustrating the first set of optical units U1. As shown in this figure, the light source U1a is disposed above the measurement target T, and its optical axis is parallel to the Z axis. On the other hand, the imaging means U1b is installed such that its optical axis is at an angular position of about 45 ° from the X axis or the Z axis in the XZ plane. The imaging means U1b includes a CCD image sensor 13 and can acquire image data 11a having a partial ellipse shape as shown in the figure.

  When the image data 11a as shown in the figure is obtained, the X coordinate axis and the Y coordinate axis are set on the image. In the illustrated example, a position corresponding to the re-top portion of the measurement object is set as the origin O. Then, the coordinate values of arbitrary points of the partial ellipse shape are defined as Xc and Yc. Then, the y-coordinate value and z-coordinate value when converted into a partial circle according to the following formulas 1 and 2 are calculated.

Here, the y coordinate and the z coordinate are coordinate values in the coordinate system after being converted into a partial circle shape, and the definitions of the parameters in the mathematical formula are as follows.
f = 35 mm (focal length of the lens)
α = 45 ° (angle of the optical axis of the imaging means)
a = 0.0052 mm
H = 120 mm (height of the CCD image sensor from the measuring object T)
C = H / cos α · T / (1 + T) −f
T = magnification (ratio between the size on the CCD image sensor and the actual size)

  With the above calculation, the shape of approximately 1/4 circle of the measurement object can be obtained. And a curvature radius can be calculated | required from this shape.

Once the radius of curvature is determined, the center coordinates of this partial circle shape are then determined. Specifically, the point is equidistant from each point of the partial circle. However, since the calculated partial circle shape may include an error, for example, three points of the partial circle shape are selected, and the center coordinates are calculated from the coordinate values of these three points. May be. However, the accuracy may be further improved by performing approximate calculation using the coordinate values of more points. By the processing as described above, a result regarding the partial circular shape and its center by the first set of optical units is obtained.
Next, measurement by the second set of optical units U2 will be described. The measurement by the second set of optical units U2 is substantially the same as the measurement method. However, it is necessary to measure the same cross-sectional position as the cross-section measured by the first set of optical units U1. For this reason, it is necessary to perform measurement at a time point delayed by a predetermined time from the measurement of the first optical unit U1. Specifically, for example, it is assumed that the distance between the first set and the second set of optical units U1 and U2 is 0.1 m and the conveyance speed of the measurement object is 1 m / sec. In this case, it takes 0.1 second in calculation for the cross section measured by the first set of optical units U1 to reach the second set of optical units U2. For this reason, the measurement with the second set of optical units U2 needs to be performed with a delay of 0.1 second from the measurement with the first set of optical units U1.

  However, the actual imaging means U1 to U4 (CCD camera) can capture about 20 frames per second. For this reason, by combining the respective images of 20 frames captured by the first set of optical units U1 and the corresponding images of 20 frames captured by the second set of optical units U2 with a delay of 0.1 seconds, respectively. It is possible to acquire partial circular data of 20 cross sections per second by the two optical units U1 and U2. Then, the acquisition of the image data and the calculation of the partial circle shape as described above are also performed for the third set and the fourth set of optical units U3 and U4.

  FIG. 4 shows each partial circle shape obtained by calculation based on image data obtained for a certain cross section. Here, since the four cameras do not measure the same cross-sectional position at the same time as described above, three-dimensional alignment of the cameras is difficult. In particular, this problem is a serious problem because vibration is applied when the measurement target T is transported. For this reason, in the present embodiment, the calculated partial circle shape is considered to cause a relative displacement of the measurement target T due to vibration or the like, and is based on the absolute coordinates viewed from the respective imaging units U1b to U4b. Instead of calculating the final cross-sectional shape based on the calculated three-dimensional position, it is assumed that the outer cross-section of the measurement target T is always a perfect circle, and for each point that can be calculated from each partial circular shape in the figure. Based on the radius of curvature, the average radius was estimated, and robust measurement was performed with respect to the displacement of the measurement target T. FIG. 5 shows the radius distribution calculated based on this method. The actual diameter of the measurement target T used in the present embodiment is 9.9 mm. As shown in FIG. 5, the radius of curvature is approximately 4.95 mm, although the radius of curvature varies depending on the position of the partial circle. Is estimated.

  Next, a method for calculating a continuous circular shape from the obtained radius distributions of the four partial circular shapes will be described. In this embodiment, (1) In order to suppress the influence of the error due to the surface roughness of the measurement target T, the load average calculation is performed in units of 5 ° along the circumferential direction of the partial circle. (2) Imaging The three-dimensional position correction process for the lens distortion of means U1 to U4 is used, and (3) a connection process for aligning the calculated positions of the four partial circles is used.

  In the processing of (1), in order to eliminate the influence of surface roughness, minute wrinkles, etc., the radius distribution estimation accuracy is improved by calculating the average value of the radius of curvature in units of 5 °. In the processing of (2), the calculation formula in the three-dimensional shape measurement based on the light section method is based on the assumption that the lens system of the imaging means is telecentric, and the calculation is based on the height of a certain reference plane. On the other hand, in the calculation processing according to the present embodiment, since the distance between the lens and the measurement target T is short, telecentricity cannot be assumed. Offset correction was performed using a lookup table in a corresponding form. Furthermore, in the process of (3), the continuity of the cross-sectional shape is assumed so that the four partial circular shapes calculated based on the image information from the four imaging means are not discontinuous at the boundary portions. Thus, offset correction was performed on the radius estimated from the images obtained by the respective imaging means.

  FIG. 6 is a diagram for explaining the definition of the roundness for shape evaluation of the measurement target T. This figure shows a case where the actual measurement target T has an elliptical shape with a large outer diameter in the vertical direction. When the outer diameter target value of the measuring object T is D, the roundness is defined as the difference between the actual outer diameter maximum value dmax and the outer diameter minimum value dmin of the measuring object T. For example, in the case of a roller used in a printer, the diameter is about 10 to 30 mm, and the roundness is assumed to be about 0.05 to 0.02 mm.

  FIG. 7 is a view showing a pipe making apparatus 100 including the roundness measuring system 1 described above. Here, FIG. 7A shows a plan view, FIG. 7B shows a side view, and FIG. 7C is a diagram for explaining a sizing process for increasing the roundness. (D) is a figure explaining a welding process. As shown in the figure, the pipe making apparatus 100 is configured such that an uncoiler 103, a forming section 105, a welded portion 107, from the upstream side (right side in the figure) to the downstream side (left side in the figure) in the material conveyance direction. A cooling section 109, a sizing section 111, a roundness measuring system 1, and a traveling cutting machine 113 are arranged. The uncoiler 103 rewinds and feeds a band-shaped metal material wound in a coil shape, and the forming section 105 forms the band-shaped metal material into a pipe shape. Also, the welded portion 107 welds a seam of a pipe-shaped metal material into a cylinder, and the sizing section 111 is for increasing the roundness of the cross section. The traveling cutting machine 113 cuts to a predetermined length while moving at the same speed as the molded measuring object T. Among these, the roundness measurement system 1 and the sizing section 111 are important in the present invention.

  That is, the roundness measurement system 1 measures the roundness of the measurement target T by the above-described method. And the correction parameter based on roundness is calculated in real time, and the molding conditions of the molding roll which is a molding die in the sizing section 111 are controlled. Specifically, as shown in FIG. 7 (C), the forming roll is brought into contact with the measuring object T from four directions, up, down, left, and right, or is formed by two horizontal directions using a horizontal roll and a vertical roll. Molding is performed by combining the upper and lower directions. At this time, the position of each forming roll is corrected by a correction parameter based on the roundness. Thereby, it is possible to dynamically control the molding conditions online from the roundness information obtained by the roundness measurement system 1. The position correction mentioned here includes not only moving each forming roll up and down and left and right but also including position correction such that these forming rolls are rotated with respect to the central axis of the measuring object T. For this reason, depending on the case, the state in which the four forming rolls hold the measurement object from the oblique 45 ° direction is also assumed. In order to increase the roundness, it is desirable to correct not only the forming rolls of the sizing section 111 but also the forming rolls provided in the forming section 105 and other sections.

  The present invention can be used in a processing line for continuously forming a long member having a circular cross section.

DESCRIPTION OF SYMBOLS 1 Roundness measurement system U1-U4 Optical unit U1a-U4a Light source U1b-U4b Imaging means C Calculation means 11a-11d Partial ellipse image 12 Circular shape T Measurement object 100 Pipe-forming apparatus 103 Uncoiler 105 Forming section 107 Welding part 109 Cooling section 111 Sizing section 113 Traveling cutting machine

Claims (9)

A light source that irradiates linearly light in a direction perpendicular to the moving direction on the surface of a measurement object whose cross-sectional outer shape is continuously moving,
Imaging means for imaging the irradiation region of the light in the measurement object from an angle direction that is not perpendicular to the transport direction;
Based on image information from each imaging means, comprising a calculation means for calculating the roundness of the cross-sectional outer shape of the measurement object,
At least two sets of the light source and the imaging unit are provided, and the two sets of the light source and the imaging unit are related to the central axis of the measurement object when viewed from the upstream to the downstream in the moving direction of the measurement object. A roundness measurement system characterized by being arranged at equiangular intervals.   4. The roundness measurement system according to claim 1, wherein four sets of the light source and the imaging unit are provided and are arranged at an angular interval of 90 °.   3. The roundness measurement system according to claim 1, wherein each pair of the light source and the imaging unit is arranged at a predetermined distance from each other along the moving direction.   The calculation means calculates a partial circular shape from image information obtained from each imaging means, combines the partial circular shapes to calculate a circular shape, and determines roundness based on the calculated circular shape. The roundness measurement system according to any one of claims 1 to 3, wherein each of the functions has a function.   In calculating the circular shape, the calculating means plots each partial circular shape in a predetermined two-dimensional coordinate system, and calculates the average curvature radius of the partial circular shape based on the coordinate value of each point in the partial circular shape. The center point coordinates of each partial circle shape are calculated based on the average radius of curvature, and the circle shape is calculated by matching the calculated center point coordinates. 4. The roundness measurement system according to 4. Roundness measuring system according to claims 1 to 5,
A pipe making apparatus provided with a pipe making machine arranged on the upstream side of the roundness measuring system to manufacture the measurement object,
The said pipe making machine has a molding condition correction function which corrects a molding condition based on the roundness information calculated by the said roundness measurement system, The pipe making apparatus characterized by the above-mentioned.   The pipe forming apparatus according to claim 6, wherein the molding condition correcting mechanism is performed by correcting a position of a molding die provided in the pipe making machine.   8. The pipe making apparatus according to claim 7, wherein the molding die sandwiches the measurement object from an up / down direction, a left / right direction, an up / down / left / right direction, and an oblique 45 ° direction.   9. The pipe making apparatus according to claim 7, wherein the molding die can be corrected in position so as to rotate with respect to a central axis of the measurement object.

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