JP2010210292A - Apparatus and method for measuring screw shape - Google Patents

Abstract

To provide a screw shape measuring device and a screw shape measuring method capable of measuring a screw shape with high accuracy with a simple configuration even for a measuring object such as a screw having a long axial direction.
A light source that emits light parallel to a spiral of a screw, a light receiving optical system that has the same light receiving optical axis as the light source, and a tube of the screw that is disposed in the path of the light receiving optical system. 1 which is obtained by scanning with the reflecting mirror 3, including the reflecting mirror 3 that scans in the axial direction and the imaging device 5 that has a line sensor 5 a that detects a one-dimensional image in a direction orthogonal to the tube axis of the screw 10. The shape of the screw 10 is measured by synthesizing the dimensional image in the tube axis direction.
[Selection] Figure 1

Description

  The present invention relates to a screw shape measuring device and a screw shape measuring method for measuring the shape of a screw, for example, a screw machined on a pipe end of a steel pipe, as well as screw parameters such as a screw height, a lead, and a taper.

  Conventionally, some steel pipe products such as oil well pipes are threaded at the end of the pipe in order to connect the end before shipment. Since troubles such as leakage of the transport medium occur, inspection of the thread shape before shipment or on the threading line is an important quality control item. For this reason, various screw inspection methods and devices have been devised and proposed. For example, API Spec 5B, “Specification for Threading, Gauging, and Thread Inspection of Casing, Tubing, and Line Pipe Threads“ These are disclosed to the users of steel pipes as inspection standards developed independently by each manufacturer.

  Here, as described in the “Special Screw Handbook” and the like, the threaded end of the pipe end is defined in various shapes depending on the thickness and use of the steel pipe. Although the length is several tens of mm and the screw height is slightly less than 2 mm to 5,6 mm, the accuracy of the measurement results is required to be equivalent to general machining tolerances, that is, high-precision measurement of about several tens of μm. From such a background, conventionally used inspection methods that are widely used and recommended in the above standards, such as contact-type shape inspection technology that measures the shape while moving the probe along the screw groove, and a dial gauge It was a mechanical screw inspection technology that combined mechanical measuring means such as a micrometer and a jig with a shape specialized for each measurement item. Here, the dial gauge and the micrometer are used in the order of 10 μm to meet the demand for the measurement accuracy.

  On the other hand, an optical screw shape inspection technique has also been proposed (see Patent Document 1). In this patent document 1, the shape of a screw is measured by a transmitted light method, the laser optical path is set in parallel with the winding of the screw, and the scanning surface created by the laser scanning light is set on the screw. In this method, the shape of the screw is measured while being inclined with respect to the axis. Specifically, the laser scanning direction is the screw height direction, and the screw height information at a certain point in the axial direction of the screw is obtained from the relationship between the laser scanning timing and the change in the amount of light. The cross-sectional shape of the screw is measured by moving the device in the longitudinal direction of the screw.

  In Patent Document 2, a light source is provided on one of the screws, a television camera is provided on the other, and the optical axis is aligned with a horizontal plane passing through the tube axis so that the imaging field of view is vertically long. The mirror is installed between the TV camera and the steel pipe so that the imaging field of view of the TV camera is only the upper and lower outer edges of the screw, and this arrangement allows the steel pipe placed horizontally in the camera field of view. The shape of the screw part on the upper and lower outer edges is projected as a silhouette image.

  Further, Patent Document 3 discloses a silhouette image formed by irradiating light parallel to a thread groove through light that has passed through the thread groove through an enlarged optical system or projecting light transmitted through the thread groove onto the projection plate. Based on the principle that the projection plate is tilted and projected to incline and the silhouette image is magnified to capture the image, each optical element uses a parallel light source as the light source, or the projection plate A parabolic mirror and a mirror scanning device are used as the imaging means for the silhouette image projected on the lens, or a telecentric optical system is used as the optical system between the screw and the projection screen to project the parallel light onto the projection plate. , Etc. are combined.

JP 63-191007 A Japanese Patent Laid-Open No. 58-62505 JP 2007-10393 A

  However, in the method based on mechanical displacement measurement such as API Spec 5B described above, since the measurement is performed by bringing a probe or a jig into contact with the screw, the accuracy and the magnitude and direction of the contact force affect the measurement value. There was a problem. In this method, only representative points such as screw diameter, screw height, and longitudinal span are measured at specific points of a screw profile distributed in the longitudinal direction of several tens to several hundreds of millimeters. There was a problem that the defect of the screw shape was not reflected in the inspection result. Furthermore, in this method, since it takes a measurement time, there is an operational problem that the total number of steel pipes to be processed every tens of seconds to several minutes may not be inspected.

  The laser scanning method described in Patent Document 1 repeats the measurement procedure of scanning and measuring a laser at each measurement pitch in the longitudinal direction of the screw and moving the measuring device to the next measurement point. If the measurement pitch is made finer, there is a problem that the measurement time is accordingly increased.

  Furthermore, in the method described in Patent Document 2, the shape of the screw is projected with a television camera. As described above, the measurement range is about 100 mm in the longitudinal direction and about several mm in the height direction. In addition, since the required measurement accuracy is several tens of μm, the number of pixels (the number of scanning lines) when measuring a silhouette as an image needs to be a large number of about 10,000 in the longitudinal direction, whereas a television The number of scanning lines of a camera or the number of pixels of a two-dimensional camera is at most about 1000, which is insufficient in accuracy, and this problem is caused by a method in which a plurality of cameras are arranged in the longitudinal direction or moved in the longitudinal direction. However, there is a problem that the procedure and apparatus configuration for obtaining a single screw shape are complicated, or that the measurement time is long as in the case of the laser scanning type.

  Further, in Patent Document 3, when a silhouette image is captured through a projection screen, not only flatness defects such as screen contamination and deflection become errors in screw shape measurement, but also silhouette due to the projection screen surface roughness. Although the fine irregularities (jagged edges) generated at the boundary cause noise in the screw profile, and even if the silhouette image is enlarged by tilting the projection screen, the pixel resolution captured by the CCD camera is improved, but the measurement target Since the resolution of the measurement of the screw shape is determined by the optical resolution of the optical system between the screw and the screen, it does not lead to an essential improvement in measurement accuracy, but it is inevitably caused by tilting the projection plate. As a result, there is a difference in the optical path length between the projection plate and the object. But there is a problem that is worse.

  The present invention has been made in view of the above, and a screw shape measuring apparatus capable of measuring a screw shape with high accuracy with a simple configuration, even for a measuring object such as a screw having a long axial direction, and An object is to provide a thread shape measuring method.

  In order to solve the above-described problems and achieve the object, a screw shape measuring apparatus according to the present invention includes a light projecting unit that irradiates light from a light source in parallel with a screw spiral, and the same light reception as the light projecting unit. A light receiving optical system having an optical axis, a scanning means arranged in the path of the light receiving optical system and scanning in the tube axis direction of the screw, and a detection for detecting a one-dimensional image in a direction perpendicular to the tube axis of the screw And measuring the shape of the screw by synthesizing in the tube axis direction a one-dimensional image obtained along with the scanning by the scanning means.

  In the screw shape measuring apparatus according to the present invention as set forth in the invention described above, the light source is a parallel light source.

  In the screw shape measuring apparatus according to the present invention, in the above invention, the light receiving optical system between the screw and the scanning unit is a telecentric optical system, and the scanning unit is a variable angle reflecting mirror. A waveform generator that generates a time waveform of an angle command value proportional to an inverse function of a relationship between an angle of view and an imaging height of the light receiving optical system, and outputs the angle command value to the reflecting mirror; The means sequentially detects one-dimensional images in the tube axis direction at regular time intervals.

  In the screw shape measuring apparatus according to the present invention, in the above invention, the light receiving optical system is proportional to the relationship between the image receiving axis and the angle of view in the light receiving optical system between the screw and the scanning unit. Using an f-θ lens, the scanning means is a variable angle reflecting mirror, and generates a waveform of an angle command value that is a linear function of time and outputs the angle command value to the reflecting mirror. And the detecting means sequentially detects one-dimensional images in the tube diameter direction at regular time intervals.

  The screw shape measuring device according to the present invention is the screw shape measuring device according to any one of the above inventions, wherein the screw at the spiral portion at each angular boundary position divided at equal angles around the tube axis of the screw. A plurality of shapes are arranged at positions to measure the shape, and the shape of the screw is measured by rotating the screw by an angle divided by equal angles.

  Further, the screw shape measuring method according to the present invention irradiates light from a light source parallel to the spiral of the screw, and passes through the gap of the screw spiral to receive light having the same light receiving optical axis as the light source. In a screw shape measuring method for measuring the shape of the screw by detecting a silhouette image of the screw through a system by a detecting means, the passing light is transmitted by the scanning means arranged in the path of the light receiving optical system. The detection means for scanning in the direction of the tube axis and detecting the one-dimensional image in the direction orthogonal to the tube axis of the screw detects the scanned passing light, and the one-dimensional image obtained along with the scanning by the scanning means The shape of the screw is measured by synthesizing in the tube axis direction.

  In the screw shape measuring method according to the present invention as set forth in the invention described above, the light source is a parallel light source.

  In the screw shape measuring method according to the present invention, in the above invention, the light receiving optical system between the screw and the scanning unit is a telecentric optical system, and the scanning unit is a variable angle reflecting mirror. Generating a time waveform of an angle command value proportional to the inverse function of the relationship between the angle of view of the light receiving optical system and the imaging height, and outputting the angle command value to the reflecting mirror. One-dimensional images with respect to the tube axis direction are sequentially detected at intervals.

  In the screw shape measuring method according to the present invention, in the above invention, the light receiving optical system is proportional to the relationship between the image receiving axis and the angle of view in the light receiving optical system between the screw and the scanning unit. An f-θ lens is used, the scanning means is a variable angle reflecting mirror, generates a time waveform of an angle command value as a linear function, outputs the angle command value to the reflecting mirror, and the detecting means However, it is characterized in that a one-dimensional image in the tube diameter direction is sequentially detected at regular time intervals.

  The screw shape measuring method according to the present invention is a screw shape measuring device that realizes any one of the above-described screw shape measuring methods, at each angular boundary position divided by equal angles around the tube axis of the screw. A plurality of screw shapes of the spiral portion are arranged at positions to be measured, and the screw shape is measured by rotating the screw by an equal angle divided angle.

  According to this invention, the light projecting means for irradiating the light from the light source in parallel with the spiral of the screw, and the light receiving optical system having the same light receiving optical axis as the light projecting means, the scanning means includes the light receiving optical system. 1 arranged in the path of the system and scanning in the tube axis direction of the screw, and the detection means detects a one-dimensional image in a direction perpendicular to the tube axis of the screw, and is obtained 1 following the scanning by the scanning means. Since the shape of the screw is measured by synthesizing a dimensional image in the tube axis direction, the screw shape can be measured with a simple configuration and high accuracy even for a measuring object with a long axial direction such as a screw. can do.

FIG. 1 is a schematic diagram showing a schematic configuration of a screw shape measuring apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram showing the relationship between the angle of view and the imaging height in a general lens. FIG. 3 is a schematic diagram showing a schematic configuration of a screw shape measuring apparatus according to Embodiment 2 of the present invention. FIG. 4 is a schematic diagram showing the relationship between the field angle and the imaging height in the f-θ lens. FIG. 5 is a schematic diagram showing a schematic configuration of a screw shape measuring apparatus according to Embodiment 3 of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a screw shape measuring device and a screw shape measuring method according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals.

(Embodiment 1)
First, a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a schematic configuration of a screw shape measuring apparatus according to Embodiment 1 of the present invention. In FIG. 1, a light source 1 as a light projecting unit irradiates light to a screw 10 from a direction substantially perpendicular to a tube axis of the screw 10 to be measured. The light source 1 preferably emits parallel light along the thread groove. Further, the light source 1 preferably has sufficient light receiving sensitivity of the imaging device 5 and has substantially uniform illuminance within the measurement visual field range. Specifically, a halogen lamp, a metal halide lamp, a diffusion plate, a telecentric optical system, and the like What comprises is preferable.

  The light receiving optical system 2 forms an image of the light transmitted through the screw groove portion of the screw 10 on the line sensor 5a of the image pickup device 5, and forms the image of only the component parallel to the optical axis. It is preferable to have a telecentric characteristic arranged at a position.

  The reflecting mirror 3 functions as a scanning unit, and changes the longitudinal position of the screw 10 projected on the imaging device 5, that is, the position in the tube axis direction, out of the light passing through the screw 10 and the light receiving optical system 2. . The reflecting mirror 3 may be composed of a polygon mirror, a rotating mirror, or the like, but is preferably composed of a galvano motor having flexibility in angle control and a plane mirror.

  The waveform generator 6 generates a time waveform of an angle command value (a waveform of an angle command value related to time) for outputting an angle command value at each measurement timing by the line sensor 5a to the reflecting mirror 3, and the reflecting mirror 3 3 is performed. The waveform generator 6 is realized by using a signal generator, a digital communication device, or the like according to the driving mechanism of the reflecting mirror 3, and the time waveform for outputting the angle command value is the inverse of the field angle characteristic of the light receiving optical system 2. The time waveform may be a function.

  That is, as shown in FIG. 2, the imaging height f of the lens L1 generally has a functional relationship of the incident angle θ, for example, a functional relationship represented by f 関 数 tan (θ) in an ideal lens. As the time waveform φ (t), φ (t) = G (t) using the inverse function G (f) of F (φ) and replacing the imaging height f of G (f) with time t. In this case, the longitudinal direction (tube diameter direction) of the synthesized one-dimensional image is substantially equidistant. As a result, the angle of the reflecting mirror 3 is output as a time waveform proportional to the inverse function of f = F (θ), which is the relationship between the incident angle θ to the objective lens in the light receiving optical system 2 and the imaging height f. Thus, when the light intensity waveform, which is a one-dimensional image sequentially captured by the imaging device 5 at regular time intervals, is synthesized, the intervals in the tube diameter direction are substantially equal.

  The imaging lens 4 is an optical system for imaging light that has passed through the rotary mirror 3 onto the line sensor 5 a that is a light receiving unit of the imaging device 5. Note that the imaging lens 4 may be omitted if only the light receiving optical system 4 can form an image on the imaging device 5.

  As described above, the imaging device 5 converts the intensity distribution of the light imaged through the screw groove of the screw 10 into an electric signal or a numerical value corresponding to the light intensity distribution, and is used by the CCD type line sensor 5a. It is done. The line sensor 5a is a one-dimensional sensor in the Z direction. The reflecting mirror 3 scans the tube axis direction of the screw 10 and scans on the XY plane. The line sensor 5a has a number of pixels of about 5000 to 10000 images, a measurement frequency of about 10 kHz to 30 kHz is selected according to the required measurement resolution and measurement speed, and the detected electrical signal or numerical data is a control unit. 11 is output to the image processing unit 12 in the system 11.

  The image processing unit 12 synthesizes a one-dimensional image captured by the imaging device 5 and sequentially sent, that is, a one-dimensional image in the pipe radial direction of the screw 10 along the pipe axis direction, and a silhouette image of the screw 10 is obtained. Then, a shape profile is generated from the silhouette image by edge processing or the like. The shape profile and the like are output to the storage unit 13 or the display unit 14. The control unit 11 controls the reflecting mirror 3 and the imaging device 5, and the input unit 15 inputs a desired instruction signal or the like to the control unit 11.

  Here, when parallel light parallel to the screw groove of the screw 10 is irradiated from the light source 1, a silhouette image of the screw 10 or the screw groove portion is input to the reflecting mirror 3 via the light receiving optical system 2. The light input to the reflecting mirror 3 is reflected by the reflecting mirror 3 whose rotation is controlled based on the angle command value from the waveform generator 6. The reflected light scanned by this reflection is output to the line sensor 5 a of the imaging device 5 through the imaging lens 4. The line sensor 5a sequentially detects and outputs a plurality of one-dimensional images of the screw 10 or the screw groove in the tube axis direction by one scan of the reflecting mirror 3 at regular time intervals. A two-dimensional image of the screw 10 or the screw groove is generated based on the one-dimensional image acquired at substantially equal intervals, and a shape profile is further generated.

  By the way, as described above, parallel light is irradiated from the light source 1 to the screw 10, and a silhouette image of the screw 10 is formed by the light receiving optical system 2 of the telecentric light receiving system having the same optical axis. The line sensor 5a is used to measure the light intensity distribution in the direction) with a fine resolution of about several μm. In order to measure the field of view in the tube axis direction as variable, a reflecting mirror 3 having a variable angle is installed between the light receiving optical system 2 and the imaging device 5. In this case, in order to increase the resolution in the tube axis direction, the scanning speed of the reflecting mirror 3 may be decreased. In other words, the time of the time waveform generated by the waveform generator 6 may be increased.

  In addition, when a diffused light source used in a normal optical measuring device is used as the light source 1, the depth in the light path direction is high on the surface (screw surface or flank surface) of the screw 10, the thread or valley bottom, the outer surface of the steel pipe, and the like. Then, since there may be an optical path that reaches the image forming portion after being reflected there, a ghost overlaps the measured silhouette image and an accurate profile cannot be obtained. Therefore, it is necessary to suppress the non-parallel light component that causes ghost. In the first embodiment, the light source 1 emits parallel light, and the light receiving optical system 2 side is also a component parallel to the optical axis. A telecentric lens that forms an image only is used, and with respect to the reflection suppression of the thread surface, the optical axis of the light projection is made to coincide with the direction of the spiral of the screw.

  In the first embodiment, since the two-dimensional shape related to the tube axis direction and the tube diameter direction of the screw is measured by one measurement operation, the screw shape can be measured in a short time. In this case, in the tube diameter direction, a one-dimensional image is acquired by a high-resolution line sensor, and a two-dimensional image is acquired by scanning in the tube axis direction. Measurement can be realized. In other words, this corresponds to scanning the line sensor extending in the tube diameter direction in the tube axis direction. Furthermore, the measurement is non-contact and the measurement pitch in the tube axis direction is made dense, so that the measurement error due to the contact state of the probe and the pressing force as in the conventional mechanical method and the inspection only for the representative point are denser. Screw shape inspection is possible. Furthermore, since it is easy to increase the measurement resolution in the screw height direction (tube diameter direction), it is possible to perform inspection with a higher resolution than conventional TV monitor systems. In addition, since a structure that does not use a reflective screen or the like, there are no disturbance factors such as screen contamination, deformation, and surface roughness, and there is no problem of tilting at night due to tilting, and more accurate screw shape inspection is possible. .

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the second embodiment, an f-θ lens 22a in which the relationship between the field angle θ and the imaging height f has f-θ characteristics is used in the light receiving optical system 22 corresponding to the light receiving optical system 2. In relation to this, the waveform generator 16 corresponding to the waveform generator 6 converts the time waveform of the angle command value to the reflecting mirror 3 (the waveform of the angle command value related to time) to a linear function (straight line) proportional to time. ).

  That is, as shown in FIG. 4, since the f-θ lens L2 and the imaging height f have a functional relationship proportional to the angle of view θ, that is, a relationship of f∝θ, the waveform generator 26 The time waveform becomes a simple straight line.

  Here, the imaging device 5 acquires a one-dimensional image by the line sensor 5a at regular time intervals, as in the first embodiment. Since the time waveform of the waveform generator 26 is also a linear function (straight line), the rotational speed of the reflecting mirror 3 is also constant.

  In the second embodiment, it is possible to realize a screw shape measuring apparatus having a simpler configuration simply by providing the f-θ lens 22a and the waveform generator 26 corresponding thereto.

(Embodiment 3)
In Embodiment 3 of the present invention, high-speed measurement is performed using a plurality of screw shape measuring devices.

  That is, as shown in FIG. 5, the four screw shape measuring devices 31 a, 31 b, 32 a, 32 b, 33 a, 33 b, 34 a, 34 b are spirals at respective angular boundary positions divided by 90 degrees around the tube axis of the screw 10. The three-dimensional shape of the screw 10 is acquired by arranging the screw shape of the portion at a position to be measured and rotating the screw 10 by 90 degrees.

  In Embodiments 1 to 3 described above, the screw 10 is fixed and the screw shape is measured. However, the present invention is not limited to this, and the screw 10 is rotated to provide a three-dimensional shape in the circumferential direction of the screw 10. May be obtained. Furthermore, the screw 10 may be fixedly arranged, and one or more screw shape measuring devices may be rotated in the circumferential direction.

DESCRIPTION OF SYMBOLS 1 Light source 2,22 Light reception optical system 3 Reflecting mirror 4 Imaging lens 5 Imaging device 5a Line sensor 6,26 Waveform generator 10 Screw 11 Control part 12 Image processing part 13 Storage part 14 Display part 15 Input part 22a f-theta lens

Claims (6)

A light projecting means for irradiating light from the light source parallel to the screw spiral;
A light receiving optical system having the same light receiving optical axis as the light projecting means;
A scanning means disposed in the path of the light receiving optical system and scanning in the tube axis direction of the screw;
Detecting means for detecting a one-dimensional image in a direction perpendicular to the tube axis of the screw;
And measuring the shape of the screw by synthesizing, in the tube axis direction, a one-dimensional image obtained along with the scanning by the scanning means.   The screw shape measuring apparatus according to claim 1, wherein the light source is a parallel light source. The light receiving optical system between the screw and the scanning means is a telecentric optical system,
The scanning unit is a variable angle reflecting mirror,
A waveform generator that generates a time waveform of an angle command value proportional to an inverse function of a relationship between an angle of view of the light receiving optical system and an imaging height, and outputs the angle command value to the reflecting mirror;
The screw shape measuring apparatus according to claim 1, wherein the detection unit sequentially detects one-dimensional images in the tube axis direction at regular time intervals. The light receiving optical system uses an f-θ lens in which the relationship between the image receiving axis and the field angle is proportional to the light receiving optical system between the screw and the scanning unit.
The scanning unit is a variable angle reflecting mirror,
A waveform generator that generates a time waveform of an angle command value that is a linear function of time and outputs the angle command value to the reflecting mirror;
The screw shape measuring apparatus according to claim 1, wherein the detection unit sequentially detects a one-dimensional image in the tube diameter direction at a constant time interval.   A plurality of screw shape measuring devices according to any one of claims 1 to 4 are arranged at positions to measure the screw shape of the spiral portion of each angular boundary position divided equiangularly around the tube axis of the screw, A screw shape measuring apparatus, wherein the screw is rotated by an angle divided by equal angles to measure the shape of the screw. Light from the light source is irradiated in parallel to the screw helix, and the silhouette image of the screw is detected via the light receiving optical system that has the same light receiving optical axis as the light source. In a screw shape measuring method for detecting the shape of the screw detected by means,
Scanning means arranged in the path of the light receiving optical system scans the passing light in the direction of the tube axis of the screw, and the detection means for detecting a one-dimensional image in a direction orthogonal to the tube axis of the screw is scanned. A screw shape measuring method characterized by measuring the shape of the screw by detecting the passing light and synthesizing a one-dimensional image obtained along with the scanning by the scanning means in the tube axis direction.

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