JPS63191007A - Method of screw inspection and measurement - Google Patents

Abstract

PURPOSE:To facilitate inspection and measurement regardless of a larger shape of screws, by setting an optical path of a laser parallel with the spiral of a screw while the shape thereof is measured inclining a scanning surface formed by a scan light of the laser to the axis of the screw. CONSTITUTION:A scanning surface S of a laser beam is at an angle theta to the axis A-1 of a pipe A so as to obtain an optical path T to a light receiver 3 from a laser projector 2. To prevent reflection otherwise caused by flanks 31 and 32 of a screw 30, the optical path T to the light receiver 3 from the laser projector 2 is inclined at an angle alpha to the axis A-1 of the pipe A in such a manner as to be parallel with the direction of spiral of the crest or bottom of the screw 30. Thus, this secures the measurement of flank faces 31 and 32 by setting the scanning surface S and the optical path T of the laser while preventing measuring errors due to reflection of the laser beam with the flank faces 31 and 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inspecting and measuring the shape of a large-diameter screw, such as an oil country tubular goods.

[Conventional technology]

BACKGROUND ART Conventionally, as a method for inspecting threads cut into the end of a pipe or the like, a contact measuring method has been adopted in which the shape is determined while moving a probe along a thread groove.

However, the diameters of the pipes manufactured vary from small diameter pipes to large diameter pipes, and the types of threads also differ, so in order to be able to measure these types of pipes, many types of measurement jigs are required. shall be. For this reason, it is necessary to replace the jig for each inspection item, which makes it difficult to automate the inspection.

In order to solve this problem, in recent years, as a means to automate the inspection and measurement of screws, for example, Japanese Patent Application Laid-Open No. 55-11
As described in Japanese Patent No. 3907, there is a method that uses contact type sensors equal in number to the number of required inspection items.

However, even if a plurality of contact sensors are used to increase the number of inspection items, the data actually obtained will have discontinuous points, so it remains difficult to judge whether the overall screw shape is good or bad. In addition, as with conventional contact-type inspections, the position of the sensor must be changed using a jig that holds the sensor depending on the diameter of the pipe and the type of thread, so there are limits to efficient inspection processing. . Furthermore, since there are large errors due to the limitations of the measurement surface by contact-type mechanical means and individual differences among operators, it is inevitable that undesirable results in terms of accuracy will occur.

On the other hand, instead of determining the shape of the contact distance, for example,
As described in Japanese Patent Publication No.-24362 and Japanese Patent Publication No. 5B-15041, a method of performing inspection using an optical system has recently come into use. In inspection and measurement using this optical system, the shape of the object to be measured is measured by irradiating the object with a beam of light, converting it into a video signal using an imaging device, and manually inputting it to a computer.

[Problem that the invention seeks to solve]

In such non-contact inspection and measurement using an optical system, the greatest advantage of the optical method is that surface measurements can be performed relatively easily.

Furthermore, when the object to be measured is a small-shaped screw or the like, data on the entire screw can be obtained by one photographing. Therefore, the position of the imaging device with respect to the object to be measured can be fixed, and the ratio between the size of the screw and the resolution of the imaging device can be kept small, making it possible to perform highly accurate inspection and measurement.

However, when the shape of the object to be measured is large, it is unavoidable that the ratio of measurement range to resolution increases, so the measurement range must be subdivided or the distance from the object to be measured must be maintained, making it impractical. It is not suitable for inspection measurements.

In other words, if you reduce the resolution to increase accuracy,
Since the imaging area becomes smaller accordingly, it is necessary to increase the number of times of imaging. Furthermore, when the imaging area is made smaller, strict accuracy is required in adjusting the focal length and setting the imaging position when changing the position of the imaging device. Furthermore, in addition to this, it is susceptible to the influence of illumination, and ti image defects often occur, resulting in a hindrance to the efficiency of processing.

In this way, even though optical measurement is capable of highly accurate inspection and measurement, this type of measurement is recommended when the object to be measured is large and the entire shape of the object is to be accurately grasped in a short period of time. There was a problem in that it was difficult to apply the method as it was.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that makes it possible to inspect and measure screws in large-diameter pipes by fully utilizing the advantages of lasers.

[Means for solving problems]

In order to achieve the above object, the present invention provides an inspection and measurement method in which the shape of a screw is measured using a laser transmission method, in which the optical path of the laser is set parallel to the winding of the screw, and the scanning surface created by the scanning light of the laser is used. The feature is that the screw shape is measured while tilting the screw with respect to the axis of the screw.

〔Example〕

Hereinafter, features of the present invention will be specifically explained based on embodiments shown in the drawings.

FIG. 1 schematically shows the screw inspection and measurement system of the present invention.

For pipe 8 with a male thread carved into the end, Robo 7) H
An inspection device connected to arm C is set. This inspection device freely changes its position and posture according to the movement of the robot B and the movement of the arm C, and is extrapolated to the end of the pipe A. In addition, various data regarding the screws obtained by the inspection bag WD are input to the computer E, which calculates the measurement items while making corrections, and outputs the pass/fail judgment of the screws and the calculated dimensions to the display F and printer G. do.

As shown in FIG. 2, the inspection apparatus includes a laser projector 2 and a light receiver 3 for measuring the shape of a screw in a frame 1 connected to an arm C of a robot B. These laser projector 2 and light receiver 3 are placed on a base 4 that moves in the axial direction of the pipe A. This base 4 is supported by two guide shafts 5, and is moved in the axial direction of the pipe A by a drive shaft 7 directly connected to a drive motor 6 as described above, so that the pipe A is scanned by the laser projector 2. . In addition, 2nd open mountain) and 2nd figure tc+ are the views taken from the 1-1 line arrow view and the ■-■ line arrow view of FIG. 2+a), respectively.

In addition, the laser projector 2 and receiver 3 are shown in Fig. 2+a+
As shown in FIG. 3, an example of a tilting mechanism for the laser projector 2 and receiver 3 is shown.

In FIG. 3, a laser projector 2 and a light receiver 3 are rotatably attached to a pair of bases 4 that are movable in the axial direction of the pipe by a drive motor 6 and a drive shaft 7, respectively. On the other hand, a tilting drive motor 8 is attached within the frame 1, and a bolt shaft 9 is connected to the output shaft of the tilting drive motor 8. Two substantially U-shaped blocks 10 are screwed onto the bolt shaft 9, and pins 11 protruding from the laser projector 2 and the light receiver 3 are loosely fitted into the grooves of the blocks 10.

In this rotating structure, when the bolt shaft 9 is rotated by the tilt drive motor 8, the block 10, which is restrained by the pin 11, moves left and right while maintaining the illustrated attitude. Due to this movement, rotational force is transmitted from the pin 11 engaged with the block 10 to the laser projector 2 and the light receiver 3. Therefore, the laser projector 2 and receiver 3 can be tilted to a required oblique angle, and the laser scanning plane can be set so as to enable measurement of the shape of the flank surface of the screw as described later.

Furthermore, in order to prevent the reflection of the laser beam that occurs when measuring the shape of the flank surface of a screw and to accurately measure the flank surface, the pipe is positioned so that the laser optical path follows the thread line of pipe A. It is possible to tilt with respect to A. FIG. 4 shows an outline of this tilting mechanism.

In FIG. 4, in the frame 1, upper and lower two plates H2 and 13 are arranged so as to be rotatable with each other, and the upper plate 12 has a small-diameter roller 14 that moves around the circumferential surface of the vibrator A.
is installed. The lower play eye 3 is integrated with the frame 1 and has a tilting drive motor 15 fixed thereto. A bolt shaft 16 is connected to the output shaft of the drive motor 15, and a support shaft 17 is provided which moves forward and backward in the direction of the pipe A by rotation of the bolt shaft 16.

By the way, when the shape of the screw is constant, the angle of inclination of the screw with respect to the axis of the vibrator A increases as the outer diameter of the vibrator A increases, that is, it rises in a direction perpendicular to the axis. Therefore, the inclination angle of the screw is determined by the outer diameter of the vibrator A. Utilizing this fact, when the distance is X from the center W of the thread line as shown in FIG. 4 fc), the position Y of the thread line is uniquely determined by the outer diameter of the pipe A. Therefore, conversely, by knowing the position NY of the screw wire, the distance 1liI
The distance from IX and the axis to position Y is obtained, from which the inclination of the thread line can be calculated.

Using this measurement principle, the inclination angle of the screw is calculated by the support shaft 17, and the upper plate 12 is rotated accordingly. By this operation, move frame 1 to vibe A.
When extrapolated to , the optical path of the laser can be set along the screw line by rotating the upper plate 12.

Furthermore, in FIG. 2, two types of contact sensors 18 and 19 for mechanically inspecting and measuring the shape of the screw are installed on the vibrator A.
Placed so that it can move forward and backward toward the center of the

These contact sensors 1B and 19 have a function of correcting data values obtained by optical measurement using a laser projector 2 and a light receiver 3.Furthermore, the frame 1 on the side where the vibrator A enters has a sensor around the vibrator A. Support roller 2 that transfers the surface
Two 0s are placed. The support rollers 20 are set so that the frame 1 can be fixed to the pipe A after the frame 1 is extrapolated onto the pipe A. Note that the frame 1 can also be provided with an inner diameter measuring device 21 for measuring the inner diameter of the pipe at the same time as inspecting and measuring the shape of the screw.

Here, the items for measuring the shape of the screw include the screw length, taper, hide, runout, etc., as well as the shape of the flank surfaces 31 and 32 of the screw 30 as shown in FIG. Measure the angle, lead and pitch of the mountain. Therefore, inspection and measurement of the flank surfaces 31 and 32 are extremely important measurement items. However, when inspecting and measuring the flank surfaces 31 and 32 by laser scanning, the measurement accuracy is low when the scanning direction is perpendicular to the screw axis, that is, the axis A-1 of the pipe A, as shown in Figure 5 (bl). becomes lower.

In other words, since the flank surfaces 31 and 32 are in a positional relationship parallel to the laser scanning direction, there are fewer measurement points as shown by the circles in the figure. Therefore, this flank surface 3
1.32 with high precision, it is necessary to shorten the measurement pitch by the laser, which results in a longer measurement time.

In addition, in the case of shape measurement using a laser, accurate shape determination cannot be made if the laser beam path between the laser emitter 2 and receiver 3 is orthogonal to the axis of the pipe A, as shown in FIG. 6 (aJ). This is because the laser light that has reached the flank surfaces 31 and 32 is reflected and is detected as a bulged shape as shown by the broken line, compared to the true thread shape shown by the solid line of the sixth open thread. Therefore, if the optical path of the laser beam is set to be almost parallel to the winding direction of the crests (or valleys) of the screw, as shown in FIG. 6 (C1), the flank surface 31.3
Accurate shape can be detected without reflection at 2.

Therefore, in the present invention, the scanning laser beam is set to run obliquely with respect to the flank surfaces 31 and 32, and at the same time, the optical path from the laser projector 2 to the light receiver n3 is made parallel to the winding of the screw 30. Perform accurate shape detection and measurement.

FIG. 7 shows a laser beam scanning system for a pipe A having a screw 30 carved therein.

First, the shape measurement of the screw 30 using a laser is performed using the same i +
As shown in a), the basic principle is to scan the transmitted laser light from the laser projector 2 to the receiver 3 in the direction of the center of the pipe. Then, by moving the laser projector 2 and the light receiver 3 in the axial direction of the pipe A, the shape of the screw 30 is continuously formed, and the screw shape is determined based on the obtained data.

In this measurement, a common method is to set a reference point P and measure the distance from this reference point P to the surface of the screw 30, as shown in FIG.

That is, the time from when the laser beam that has been blocked by the reference point P is transmitted to the receiver 3 until it is blocked by the screw 30 again is measured, and the distance between the reference point P and the surface of the screw 30 is used as data. This allows shape measurement to be performed. However, when the base 4 on which the laser projector 2 and the receiver 3 are mounted moves, the position of the reference point P may fluctuate due to the influence of vibrations, etc., and this amount of fluctuation causes an error in measurement. For this reason, when the reference point P is incorporated into the frame 1 of the inspection device, it is preferable to place it in a dynamic system that is not affected by the movement of the base 4 and other movable members.

Further, in order to inspect the flank surfaces 31 and 32, the laser scanning surface is set to be inclined with respect to the axis of the pipe A so that many measurement points can be obtained by laser scanning. That is, as shown in the schematic diagram of FIG. 7 (C1), the scanning surface S of the laser beam forms an angle θ with respect to the axis A-1 of the pipe A, and the optical path T from the laser projector 2 to the receiver 3 is In order to prevent reflection from the flanks 31 and 32, the laser projector 2 is installed as shown in Figure 7+d+.
The pipe A is inclined at an angle α with respect to the axis A-1 of the pipe A so that the optical path T from the pipe A to the light receiver 3 is parallel to the direction of the @ line of the ridge or valley of the screw 30. In other words, as shown by the dashed line in FIG. The laser projector 2 and the receiver 3 are in the state shown by the solid line with their postures twisted so that they have an angle of
Set.

By setting the scanning plane S and the optical path T as described above, the flank surface 3
1.32 can be measured reliably, and measurement errors due to reflection of laser light by these flank surfaces 31, 32 can be prevented.

FIG. 8 shows the detection of the shape of the screw 20.

In the fat shown in the same figure, first, the scanning plane S is moved toward the pipe in the direction of the axis A-1 with an inclination of angle θ to the axis A-1 of the pipe A as shown in FIG. 7 (C1). By this operation, the scanning plane S is sequentially moved as shown by ■, ■, ■, and ■ in the figure, and the shape of the screw 30 excluding the flank surface 32 is measured as shown in FIG. 8 Tbl. When the shape including the right end side of the screw 30 has been measured, the scanning plane S
The inclination angle is changed so that the base 4 faces the other side flank surface 32, and the moving direction of the base 4 is reversed. By this operation, the shape including the flank surface 32 is measured by the operation surface S facing in the directions of ■, ■, and ■ in FIG. 8(a), and
The entire shape of the screw 30 is detected as shown in Figure (C1).

According to the measurement principle as described above, it is possible to accurately detect and measure the shape of the screw 30 including the flank surfaces 31 and 32.

The actual measurement method using the inspection device is to first insert the frame l from the end of the pipe A, and hold the circumferential surface of the pipe with the support rollers 20. Next, the frame 1 is rotated around the axis of the pipe by the driving force of the arm C of the robot B. At this time, the laser projector 2 and receiver 3 scan the cylindrical seal portion 33 (see FIG. 5 fa) at the end of the vibrator A, and at the same time, the contact sensor 18, 19 performs a shape inspection. The inspection items for this seal portion 33 include the outer diameter, axial length, taper, etc., and the measurement results are used as a reference for measuring the shape of the screw 30.

Note that in measuring the seal portion 33, there is no need to tilt the scanning plane S and the optical path T between the laser projector 2 and the light receiver 3.

Next, based on the data measured on the seal portion 33, the screw 3
An origin is set when measuring the shape of the screw 30, and the shape of the screw 30 is detected by making the axial direction and the outer diameter position of the pipe correspond to this origin. In detecting the shape of the screw 30, as described above, the optical path T of the laser is made parallel to the winding drawn by the peaks or valleys of the screw 30, and at the same time, the flank surface 3
For the measurement of 1.32, scan plane S is set to axis A-1 of pipe A.
tilt against.

Then, when the setting of the optical path T and the attitude of the scanning surface S is completed, screw 3 is tightened according to the procedure shown in FIG.
Measure the shape of 0. That is, - the flank surface 31 of the example
With the scanning plane S set in a measurable posture, the base 4 is moved in a direction away from the seal portion at the tube end, and at the same time, the frame 1 is rotated around the axis A-1 of the pipe A. By this movement of the base 4 and rotation of the frame 1, the screw 3
Shape data regarding the shape of the entire circumference of 0 can be obtained.

Furthermore, after measuring the screw 30 to the right end, the scanning plane S
The position of the base 4 is changed so that the other side flank surface 32 can be measured, and the base 4 is moved to its original position.

During the above reciprocating movement of the base 4, the screw 3o is
Data regarding the overall shape is collected as shown in C1,
The shape of the screw 30 at each position can be measured. Then, as a result of inputting and calculating these data to the calculation 41E, the shape of the screw 30 is displayed as an image on the display F, and is output to the printer G.

In the above-described shape measurement of the screw 30, the shape inspection data obtained by laser transmission using the laser projector 2 and receiver 3 is corrected with the data obtained by the contact sensor 18 and 19, and the final result is obtained. Determine the shape.

〔Effect of the invention〕

As explained above, in the inspection and measurement of screws of the present invention, when measuring the shape by passing the laser, the scanning plane of the laser is crossed with the flank surface so that the measurement of the flank surface can be performed with high precision, and the optical path of the laser is is parallel to the winding of the screw. Therefore, the shape of the screw including the flank surface can be accurately inspected and measured, and important items such as the pitch of the screw can be inspected with high accuracy. Furthermore, since the transmitted laser is not reflected from the flank surface, the shape of the flank surface can be measured with even higher accuracy.

Furthermore, since it is a transmission method using a laser, inspection and measurement can be easily performed even if the shape of the screw is large.Compared to the conventional optical method that includes an In image process, the equipment is less expensive, and it can also be used for large pipes. can.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the screw inspection system of the present invention, Fig. 2 is a diagram showing an example of the inspection device, Fig. 3 is a diagram showing an example of the tilting mechanism of the laser projector and receiver, and the fourth part is a diagram showing the laser A diagram showing the tilting mechanism for aligning the light projection path along the screw line, Figure 5 is a diagram showing the screw shape and the distribution of measurement points by the laser scanning plane perpendicular to the screw axis, and Figure 6 is a diagram showing the slope of the screw winding. A diagram showing the laser optical path and the deviation of the screw shape due to reflection on the flank surface, Figure 7 is an explanatory diagram showing the setting of the laser scanning plane and optical path, and Figure 8 is the screw inspection method and the screw shape obtained by the inspection. This shows that.

Claims (1)

[Claims] 1. In an inspection and measurement method that measures the shape of a screw using a laser transmission method, the laser beam path is set parallel to the screw winding, and the scanning surface created by the laser scanning light is tilted with respect to the axis of the screw. A screw inspection and measurement method characterized by measuring the shape.