JPS634642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for a threaded member having a thread formed at one end, and detects, in a non-contact manner, the presence or absence of an incompletely threaded part with black skin attached to the top of the thread. Or, find at least one of the length of the complete thread without black skin attached to the thread (complete thread length), the length of the incomplete thread (incomplete thread length), and the total length of the thread. The present invention relates to an inspection device for screw members that can be used to inspect screw members.

Conventionally, for example, inspections such as detecting black scale and measuring the complete thread length of a pipe thread formed at the end of a pipe have relied on visual inspection by an inspector, which has caused the following problems.

(1) There is a possibility of overlooking the black skin on a screw thread with a small amount of black skin remaining, and incomplete threads are often misjudged as complete threads.

(2) Since the work is simple and requires attentiveness, inspectors are highly fatigued and cannot continue working for long periods of time.

(3) It takes a very long time to strictly perform black scale detection and complete peak length measurement.

In order to solve the above problems, the following screw inspection device for screw members has been proposed.

(a) Screw black skin detection device described in Japanese Patent Publication No. 53-45708: The contents of this device are as follows. That is, a movable ring that is movable in the direction of the screw axis and rotates in the circumferential direction of the screw is equipped with a black skin detection sensor (spot light projector and light receiving device), and a measuring element that confirms that the black skin detection sensor is correctly located at the top of the screw thread. is fixed. Prior to measurement, the moving ring is first moved until the measuring head touches the screw flank. When the probe contacts the screw flank, the spot light projector and light receiving device are set on the top of the screw thread, and the reflectance can be measured.
Next, when the measurement is started, the moving ring moves along the screw thread while rotating, and at the same time, the presence or absence of black skin is detected by the difference in the amount of reflected light using a spot light projector and a light receiving device. At this time, the position where the black crust is detected for the first time is considered to be the boundary position between the fully threaded part and the incompletely threaded part, and the complete thread length is calculated from the movement of the moving ring at that time and the thread end face position detected separately by a contactor. .

However, the following problems are listed as problems with the black scale detection device for screws described in this publication.

(1) Black skin is detected using a spot-shaped sensor, and when measuring the complete thread length, it is necessary to trace all the threads while rotating the black skin detection sensor along the thread. Therefore, the time required for measurement is long.

(2) Since the black skin detection sensor and tracing sensor (measuring element) must be installed close to or in contact with the screw surface, they are susceptible to positional fluctuations on the screw surface due to bending of the pipe nose, etc. during measurement. Furthermore, it is difficult to inspect various types of screws with different diameters using a single device.

(3) The distance between the black skin detection sensor and the copying sensor is semi-fixed, so it is difficult to inspect various types of screws with different screw pitches with a single device.

(b) Automatic inspection device for screw members described in JP-A-54-150163: The contents of this device are as follows. In other words, it is a device that automatically inspects the external appearance of threaded parts such as bolts and pipe fittings, including the finished state of threaded parts and the presence or absence of burrs at the ends. A photoelectric conversion device is used to image the illuminated surface from an angle perpendicular to the screw axis to obtain an electric signal with a brightness distribution along the screw axis. At this time, if the threaded portion is normal, the obtained brightness distribution has low brightness at that portion because there is no reflection from the threaded valley, resulting in a pattern having only maximum points corresponding to the threaded threaded portion. On the other hand, for uneven thickness defects and single thread defects, diffuse reflection occurs from the unthreaded part (black skin), so the distance between the maximum points in the brightness distribution is the maximum point when the thread part is normal. Different from interval. The presence or absence of melasma is detected by measuring the maximum point interval and comparing it with the reference interval. Furthermore, by rotating the screw member at a constant speed and repeating the above process, the presence or absence of black skin is detected over the entire area of the screw member.

However, the automatic inspection device for screw members described in this publication has the following problems.

(1) By illuminating the threaded part from an angle that is not perpendicular to the screw axis, a shadow is created on the threaded valley, making it possible to observe the threaded part without light reflected from the threaded valley. This is the method based on the premise. Near the end of thread cutting, the thread valley is generally shallow, so light enters the thread valley and the reflected light is observed, which may be mistakenly recognized as a complete thread.

(2) On both shoulders of the thread of an incomplete thread, burr-like protrusions are likely to occur during thread cutting, and by observing reflections from the burr-like protrusions, it is possible to convert an incomplete thread to a complete thread. There is a risk of misunderstanding.

(3) Uneven illuminance tends to occur in the light reflected from the screw surface, and furthermore, there is a high possibility that the boundary between a fully threaded part and an incompletely threaded part will be mistakenly recognized due to the influence of the unbalanced illuminance, so stable measurements cannot be achieved. is difficult.

Therefore, the present invention has been made to solve the above-mentioned problems.The present invention has been made in order to solve the above-mentioned problems.The present invention is directed to a screw member having a screw formed at one end thereof, and an illumination lamp disposed at a position where the illumination light directly hits the top and bottom of the screw. and an imaging means disposed at a position where reflected light of the illumination light from the top and bottom of the screw directly enters the screw member, further comprising: By means of binarizing the obtained reflected light detection signal, measuring an interval between the binarized signals, and detecting a binarized signal having an interval corresponding to the pitch of the screw, Detection means for detecting that the screw has an incompletely threaded portion, or (a) end face position measuring means for measuring the position of one end face of the screw member with respect to a reference position; (b)
means for binarizing the reflected light detection signal obtained by the imaging means; and a binarized signal having an interval corresponding to 1/2 of the pitch of the screw with respect to the reference position and corresponding to the pitch of the screw. The boundary position between the binarized signal and the interval
and a position measuring circuit for measuring at least one of the cutting end positions corresponding to the cutting ends of the screw, based on a position measuring signal from the position measuring circuit and an end face position measuring signal from the end face position measuring means. , a complete thread length from one end surface of the threaded member corresponding to the interval between the boundary position and the end face position, and a length of one of the threaded members corresponding to the interval between the end face position and the cut end position. A screw member inspection device comprising a signal processing means having an arithmetic circuit for calculating at least one of the total length of the screw from the end face and the length of the incomplete thread corresponding to the interval between the cut end position and the boundary position. It is characterized by the following.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of a screw member inspection device according to the present invention. In the figure,
Reference numeral 1 denotes a pipe with a thread formed at one end, and 1a is the threaded part of the pipe. It is stopped by one end of the pipe hitting a stopper that does not hold the pipe (one end of the pipe 1 may come into contact with the stopper and stop, but it may also stop with a certain distance from the stopper). ). 2 is a pipe rotation device in contact with the lower surface of the pipe, and 3 is a screw (pipe) rotation angle detection device connected to a roller 3a in contact with the lower surface of the pipe.By driving the pipe rotation device 2, the pipe 1 is moved around its axis. It rotates (rotates) around the center, and the rotation angle is detected by the screw rotation angle detection device 3. Reference numeral 4 denotes a contact of a micrometer. After the pipe 1 stops moving, the contact 4 moves until it contacts one end surface of the pipe 1. Thus, the micrometer detects a reference stopper (not shown). The position (distance) of one end surface of the pipe 1 with respect to the pipe 1 is measured, and the result is converted into an electrical signal by the end surface position detection device 5. Reference numeral 6 denotes a diffused illumination device as an illumination means arranged at a position where the illumination light directly hits the top and bottom of the threaded portion 1a of the pipe 1. That is, the pipe threaded portion 1a is illuminated by the pipe 1 by the diffused illumination device 6 having a wide illumination surface 6a.
is illuminated from a direction in which the axis l ₁ of the lamp and the illumination center axis l ₂ of the diffused illumination device 6 substantially form a 90° angle, and the illumination light directly hits the top and bottom of the screw (the surface to be illuminated is ).

Reference numeral 7 denotes a photoelectric conversion device as an imaging means, which is arranged at a position where reflected light of the illumination light from the top and bottom of the thread of the threaded portion 1a of the pipe 1 directly enters. The image is taken from a direction in which the axis l ₃ and the axis l ₁ of the pipe 1 substantially form an angle of 90°.

Note that by using the above-mentioned lighting, lighting that satisfies the following two conditions can be realized.

(1) A strip-shaped illuminated surface 6b that is wide in the circumferential direction of the screw and uniform in the axial direction can be obtained.

(2) Very little uneven lighting.

Therefore, even when using a photoelectric conversion device that captures images in a straight line, such as a line sensor, it is possible to capture images with sufficiently high stability against fluctuations in the imaging position of the screw portion. Further, the central axis l ₂ and the optical axis l ₃ of the illumination device 6 are separated from each other to such an extent that the diffused illumination device 6 and the photoelectric conversion device 7 do not overlap.

FIG. 2 shows an example of the reflection brightness distribution in the axial direction of the threaded portion 1a of the reflected light detection signal obtained when illuminating and imaging with the above configuration, and will be described below. Curve 8 in the figure is the profile of the screw, with 8a representing the flank, 8b the top, 8c the bottom, and 8d the black skin. Since the threaded portion 1a is illuminated and imaged from a direction 90° with respect to the axis of the pipe 1, there is no reflection from the flank portion 8a of the thread, and the brightness of that portion is low. Furthermore, since the reflectance of the black skin 8d is extremely low, the brightness of the remaining screw thread of the black skin 8d, that is, the top portion 8b of the screw that is an incomplete threaded portion, is also low. On the other hand, the thread of the fully threaded portion has a high reflectance, so the brightness is high, and the bottom portion 8c has high brightness regardless of whether it is a fully threaded portion or an incompletely threaded portion. Therefore, in the brightness distribution pattern shown in FIG. 2, the brightness peak interval is 1/2 the pitch of the screw in the fully threaded portion, whereas it is an interval corresponding to the pitch of the screw in the incompletely threaded portion.

Focusing on this feature, as shown in FIG.
The reflected light detection signal of a is binarized, the presence or absence of black skin (incomplete threaded part) is detected based on this binarized signal, and the completeness of the end face position is detected based on the signal from the end face position detection device 5. At least one of the complete thread length, the incomplete thread length, and the total thread length is determined by calculating the boundary position between the threaded part and the incompletely threaded part and the thread cutting end position.

As a means for binarizing the reflected light detection signal of the threaded portion 1a, a well-known binarization circuit (comparator) can be used. In this example,
As shown in FIG. 3A and FIG. 3B, the signal processing device 10 is configured to perform processing that eliminates the influence of noise during binarization.

As shown in the figure, the signal processing device 10 consists of a preprocessing circuit 16 and a main processing circuit 17, and is characterized in that the preprocessing circuit 16 is arranged before the binarization circuit 18, which is a well-known technique of the main processing circuit 17. has.
The pre-processing circuit 16 has a function of emphasizing the pulses caused by the reflected light from the top and bottom of the screw from the reflected light detection signal to obtain a stable screw signal emphasis signal, and the main processing circuit 17 processes this signal. Therefore, it has a function of detecting whether or not there is a black crust on the threaded portion 1a of the pipe 1. Details of the processing method of the preprocessing circuit 16 are shown in FIGS. 4A to 4E, and will be described below. FIG. 4A shows an example of an image obtained by the photoelectric conversion device 7, in which 11a is a reflected light receiving section, 11b is
The screw flank portion 11c is a black skin portion, and 11d is a sampling line in the circumferential direction of the screw. As a first step, the moving average circuit 13 performs moving average processing in the direction of the screw axis to remove high frequency noise in the reflected light detection signal (FIG. 4C). As a second step, the two-point averaging circuit 14 averages the signal values of two points having an interval corresponding to 1/2 of the screw pitch, and performs two-point averaging processing in which the average value is used as the signal value of the center point of the two points. (Figure 4 d). Furthermore, as a third step, the two-point average signal is subtracted from the previously obtained moving average signal by the difference calculation circuit 15 to obtain a screw signal emphasis signal. As a result of the above processing, abnormal reflections due to the screw surface shape, illumination unevenness, and brightness level fluctuations due to changes in illumination intensity are removed from the reflected light detection signal obtained by the photoelectric conversion device 7. It is possible to obtain a stable signal in which only the pulse signal due to reflection from the bottom of the cell is emphasized. However, regarding the addition average width and moving average width during the above processing,
An average width that can sufficiently remove noise shall be used.

Next, the screw signal emphasis signal obtained by the above processing is input to the main processing circuit 17, and is first binarized by the binarization circuit 18. The pulse signal obtained at this time is sequentially measured by the detection circuit 19, starting from the pulse corresponding to one end of the pipe 1. Pulses at intervals corresponding to the thread pitch of the threaded portion 1a (that is, black skin portions) are detected and output as black skin detection signals.

Next, the signal processing device 10 for screw length detection (measurement) shown in FIG. 3B will be explained. 2 of the processing circuit 16 and main processing circuit 17
The value conversion circuit 18 is exactly the same as described above.

The pulse signal binarized by the binarization circuit 18 is sequentially measured by the pulse interval measuring circuit 20 starting from the pulse corresponding to one end of the pipe 1, and is determined to have at least one of the following two pulse intervals. Two processes are performed. Completely threaded portions and incompletely threaded portions are separated based on the difference in their pulse intervals, and their boundary positions relative to the reference position (relative to the stopper) are output. Alternatively, since there is no pulse after the threading end point, the pulse interval measuring circuit 20 determines and outputs the threading end position with respect to the reference position.

The first arithmetic circuit 21 receives these position measurement signals and
Based on the end face position measurement signal from the end face position detection device 5, the complete thread length (full thread length) from one end face of the pipe 1 corresponding to the interval between the boundary position and the end face position, and the end face Calculate at least one of the total thread length from one end surface of the pipe 1 corresponding to the interval between the cutting end position and the cutting end position, and the incomplete thread length corresponding to the interval between the cutting end position and the boundary position. and output the result.

Next, a second embodiment of the present invention will be described. In the second embodiment, in addition to the first embodiment, the pipe rotation device 2 is used to rotate the threaded portion, and the above-mentioned measurements are performed at multiple points in the circumferential direction of the thread, thereby determining the complete thread length of the thread as a whole. , at least one of the incomplete thread length and the total thread length is measured. The above series of processing (excluding black skin detection processing)
At this time, the controller 9 in FIG. 1 controls the timing of sampling in the circumferential direction of the screw and measurement of the screw as a whole. That is, the controller 9 instructs the signal processing device 10 to input a reflected light detection signal and an end face position detection signal every time the screw rotation angle obtained by the screw rotation angle detection device 3 reaches a predetermined sampling angle. At the same time, the start of signal processing is commanded, and when the screw makes one rotation, at least one of the complete thread length, incomplete thread length, and overall thread length of the thread as a whole is measured from the processing and calculation results at each sampling angle.

That is, the second arithmetic circuit 22 in FIG. calculates the maximum value to determine and output the complete thread length and total thread length of the screw as a whole. Furthermore, by subtracting the complete thread length from the total thread length, the incomplete thread length (length of the incomplete thread portion) is calculated and output.

In addition to this, by using the averaging process in the screw circumferential direction, it is also possible to reduce noise due to abnormal reflection within a small area in the circumferential direction.
That is, in FIG. 3A, an adding and averaging circuit 12 is placed before the moving averager circuit 13, and the reflected light detection signal data obtained by detection in accordance with the rotation of the pipe 1 is added and averaged in the circumferential direction of the screw. Remove noise. The additive average width is the same as the moving average width mentioned above.
An average width that can sufficiently remove noise shall be used.

The present invention provides the following effects.

(1) Not limited by the outer diameter of the screw to be measured or the type of screw, and by fully dealing with disturbance factors such as bending of the screw part, it is possible to detect black skin, complete thread length, etc. It is possible to measure the total screw length, incomplete thread length, etc.

(2) Since it is a non-contact type, there are fewer failures of the device and it is easy to operate and maintain the device.

(3) Complete thread length during one rotation of the target screw,
It is possible to measure the length of an incomplete thread and the total length of a screw, and the time required for measurement is short.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a screw member inspection device according to the present invention, FIG. 2 is a diagram showing a brightness distribution pattern of a reflected light detection signal, and FIG. 3 A and B are blocks of a signal processing device. Figure 4A shows an example of an image produced by a photoelectric conversion device;
E is a diagram showing an example of signal waveforms in each part of the preprocessing circuit. DESCRIPTION OF SYMBOLS 1...Pipe, 1a...Thread part, 2...Pipe rotation device, 3...Screw rotation angle detection device, 3a...
Roller, 4... contact, 5... end face position detection device, 6... diffused illumination device, 7... photoelectric conversion device,
8...Curve, 9...Controller, 10...Signal processing device, 12...Additional averaging circuit, 13...Moving average circuit, 14...2-point averaging circuit, 15...Difference calculation circuit, 16...Previous Processing circuit, 17... Main processing circuit, 18... Binarization circuit, 19... Detection circuit, 2
0... Pulse interval measuring circuit, 21... First arithmetic circuit, 22... Second arithmetic circuit.

Claims (1)

[Scope of Claims] 1. For a screw member having a screw formed at one end thereof, an illumination means disposed at a position where the illumination light directly hits the top and bottom of the screw; an imaging means disposed at a position where the reflected light of the illumination light from the top and bottom of the screw directly enters; means for binarizing the reflected light detection signal obtained by the imaging means; and detecting means for detecting that the screw has an incompletely threaded portion by measuring the interval between the encoded signals and detecting a binary signal having an interval corresponding to the pitch of the screw. An inspection device for screw members, characterized in that: 2. For a screw member having a screw formed at one end, an illumination means arranged at a position where the illumination light directly hits the top and bottom of the screw; an imaging means disposed at a position where the reflected light of the illumination light directly enters; an end face position measuring means for measuring the position of one end surface of the screw member with respect to a reference position; and a reflection obtained by the imaging means. means for binarizing a photodetection signal, and a boundary between a binarized signal having an interval corresponding to 1/2 of the pitch of the screw and a binarized signal having an interval corresponding to the pitch of the screw with respect to the reference position; and a position measuring circuit that measures at least one of a cutting end position corresponding to the cutting end of the screw, a position measuring signal from the position measuring circuit, and an end face position measuring signal from the end face position measuring means. Based on the complete thread length from one end surface of the threaded member corresponding to the distance between the boundary position and the end face position, and the threaded member corresponding to the distance between the end face position and the cut end position. and a signal processing means having an arithmetic circuit for calculating at least one of the total length of the screw from one end surface and the length of the incomplete thread corresponding to the interval between the cutting end position and the boundary position. Features: Inspection device for screw members.