JP2564741B2 - Thread defect detection method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection method and apparatus for detecting a yarn flaw in a continuous yarn heat treatment step for producing carbon fibers. More specifically, the present invention relates to a yarn flaw detection method and apparatus by fusion of polyacrylonitrile-based carbon fibers or pitch-based carbon fibers or the like in which the occurrence of fusion during the heat treatment stage is inherent in the yarn.

[0002]

2. Description of the Related Art In the present production of carbon fibers, a substance called a precursor, which contains a raw material atom of a final fiber, is spun into a fiber, and the fiber is first heated in an oxidizing atmosphere at a temperature of 150-4.
Infusibilization step of infusibilizing treatment at 00 ° C, and then firing of the infusibilized yarn bundle in the carbonization step performed at 800 to 1200 ° C so that the fiber form is maintained, and the breaking tension is improved. And in the next graphitization step, 150
A temperature of 0 to 3000 ° C. is selected according to the purpose, and high elasticity and high strength are imparted, and a surface treatment step for improving the adhesiveness with the resin when it is made into a composite material is performed. It The infusibilizing step, the carbonizing step, the graphitizing step and the surface treatment step are included in the yarn bundle continuous transfer heat treatment step.

In the infusibilizing treatment, if the precursor fiber is heated as it is, it is melted and does not become fibrous.
Before carbonization, graphitization, etc., the fiber to be treated is subjected to heat treatment at an ignition point (500 ° C.) or lower in an oxidizing atmosphere,
It introduces oxygen into the molecular structure of the fiber to crosslink the carbon atoms and raise the softening point.

However, the reaction in the insolubilization treatment is an exothermic reaction, and the generated heat is stored inside the fiber bundle and causes a rise in temperature, so that it is not possible to completely prevent the melting of the fiber. .

Therefore, there has been a need for a detection method and apparatus for detecting a yarn defect due to melting of fibers in the heat treatment process for continuously conveying a yarn bundle after the infusibilizing process.

However, in the electric type yarn flaw detection (detection of change in electric resistance within a certain section of the yarn bundle), there is a large change due to change in contact resistance, presence or absence of surface finishing (sizing), and degree of drying. In mechanical type flaw detection, when passing through the die, in addition to the increase in contact that causes deterioration of the yarn,
Since it has many problems such as changing its shape due to its flexibility, it could not be adopted when used for implementation.

In the simple optical flaw detection, the yarn flaw is manifested in the outer peripheral portion of the yarn without deteriorating the yarn by catching the change in the light amount (for example, a single yarn break, a fluff lump or a knot). Could be detected.

However, in such an optical detection method, it is not considered to detect even a fusion-bonded portion due to melting of the fibers existing in the yarn bundle, and such a defective portion in the yarn bundle is optically detected. Despite performing expression detection
There was a problem that it was overlooked as it was because there was no abnormal appearance.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a yarn such as a polyacrylonitrile-based carbon fiber or a pitch-based carbon fiber, which is present in the yarn bundle and cannot be found or detected from the appearance of the yarn bundle. A method and an apparatus for detecting a fused defect portion between single yarns in a bundle.

[0010]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention have shown that in a continuous yarn heat treatment step in the production of carbon fibers, a guide roller, which is a minimum required for conveyance, is used as a support roller, By giving the bundle a proper curvature and contact angle, the conveyed yarn is bent at the roller portion, so that the fused portion, which is solidified and loses flexibility, is destroyed, and one end of the fragment is broken. The present invention has been completed based on this knowledge, knowing that the above object can be achieved by projecting from the outer circumference of the striation and detecting a yarn flaw with an optical detection device.

That is, the object of the present invention is to carry a yarn bundle in a continuous heat treatment process for producing a yarn bundle in the production of carbon fibers by bending and delivering the yarn bundle at at least one location, and receiving the amount of light received from the vicinity of the bent portion where light is irradiated. The present invention can be achieved by a yarn flaw detection method characterized by detecting the presence or absence of a defect in the yarn bundle based on the change.

Another object of the present invention is to provide a yarn bundle, which is a defect detection object, on a conveying path, and the yarn bundle has a radius of curvature of 5 to 20 mm and a contact angle of 10 to the conveying direction. 90
At least one support roller that is bent at an angle of 0 ° and the light projecting portion and the light receiving portion are directly aligned so that a detection area is set in the yarn bundle in which the yarn bundle comes into contact with the roller and is bent. And a detection unit for detecting a defect in the yarn bundle by comparing a received light amount of a light receiving portion of the sensor with a preset threshold light amount for defect detection. This can be achieved by a yarn flaw detection device characterized by the above.

[0013]

According to the yarn flaw detecting method used in the present invention, it is possible to detect the fused portion in the yarn which cannot be detected or detected from the appearance of the yarn bundle, and causes fluffing, single yarn breakage, yarn It is also possible to detect a yarn bundle defect portion such as a knot portion at the same time.

The support roller of the yarn flaw detecting device used in the present invention is designed to bend the yarn bundle, which is the defect detection object, with a radius of curvature of 5 to 20 mm and a contact angle of 10 to 90 ° with respect to the conveying direction. At least one yarn bundle is provided on the conveying path. Therefore, a defective portion that does not become exposed to the outside in a normal transport state such as a fused portion existing in the yarn bundle that is the defect detection object is exposed to the surface of the yarn bundle, and the internal defect portion is exposed. It can be easily detected.

Further, according to the present invention, it is necessary to provide at least one support roller in the yarn flaw detection device, but it is more preferable to provide two support rollers. That is, when two support rollers are provided, the first support roller bends the yarn bundle as described above, and fluffs on one surface (outer surface of the first support roller), and A yarn bundle defect portion such as a yarn break or a yarn knot is exposed, and then the second support roller bends the yarn bundle on the side opposite to the first support roller, and the other surface (second A similar defect of the yarn bundle may be exposed on the outer surface of the support roller (1), and the defect may be exposed from both sides of the yarn bundle for confirmation by the sensor.

A detailed description of such an apparatus is as shown in FIGS. 1 and 2. That is, the yarn flaw detection device 1 according to the present invention is configured such that the yarn bundle 2 that has passed through the carbonization furnace (not shown) in the carbon fiber yarn bundle continuous transport heat treatment step is
After passing through the guide rollers 3, 4 and 5, the first support roller 6 is bent at a contact angle α °. in this case,
The guide rollers 3, 4, and 5 have a large radius of curvature such that the defective portion of the yarn bundle is not substantially exposed.

The defective portion exposed by this bending is detected by the first detecting means 7 attached to the first support roller 6. As shown in FIG. 2, the detecting means 7 has a sensor 8 arranged in the rotation axis direction of the support roller 6 (direction orthogonal to the feeding direction of the yarn bundle). The sensor 8 includes, for example, a light projecting section 8a and a light receiving section 8b.
The yarn bundle 2 is provided on a straight line, and the yarn bundle 2 bent by the support roller 6 is arranged in the middle of the straight line so that the yarn bundle 2 passes through the detection area 15. The laser light emitted from the light projecting section 8a is received by the light receiving section 8b, and the change in the yarn bundle is detected to output the comparator.
It is taken out as an analog output, detected and recorded by the first pen recorder 9, and an alarm is issued by the first buzzer 10 when an abnormality occurs.

In this way, the yarn bundle 2 in which the defective portion on one side (the outer surface of the first support roller 6) has been detected has the contact angle β ° at the second support roller 11 on the other side. The defective portion of the yarn bundle is exposed by bending it to the side (the outer surface of the second support roller 11).
Then, as in the case of the first support roller 6, the second support roller 6
The defective portion is detected by the detecting means 14 of FIG. The detecting means 14 is also the same as that shown in FIG. 2, and it detects and records by the second pen recorder 12, and the second buzzer 1
When 3 is abnormal, an alarm is issued.

As described above, the sensor used in the present invention includes the light projecting portion and the light receiving portion so that the yarn bundle comes into contact with the support roller and the detection area is set in the yarn bundle. Are arranged to face each other in a straight line. Therefore, FIG.
As shown in (A), fusion bonding with a stick type internally fixed portion, FIG.
As shown in (B), single yarn breakage and fusion with a fixed portion, and as shown in FIG. 3 (C), an extra load is applied to the yarn while the defective portion such as a single yarn breakage is in non-contact. It can be detected without giving.

Further, the detecting means compares the quantity of light received by the light receiving portion of the sensor with a preset quantity of light for detecting a defect. As a result, defects in the yarn are detected.

As the sensor used here, a photoelectric sensor using a semiconductor laser or the like used as a laser type discrimination sensor can be used. As described above, the sensor may detect a defective portion of the yarn bundle group at the same time by arranging one set of the light emitting portion and the light receiving portion on the axial end of the roller so as to face each other in a straight line. It is also possible to detect a defective portion for each yarn.

The bending of the yarn bundle with respect to the roller has a radius of curvature of usually 5 to 20 mm, preferably 7 to 14 mm,
It is more preferably in the range of 8 to 11 mm, and the contact angles α and β are usually 10 to 90 °, preferably 20 to 6
The angle is 0 °, more preferably 20 to 30 °. By bending so as to have the radius of curvature and the contact angle,
The fused portion inside the yarn bundle breaks and protrudes outward from the yarn bundle body, the thickness of the yarn bundle increases at the bend, and the amount of light received from near the bend is greater than the amount of light received by normal yarn. Therefore, it is possible to easily detect the presence or absence of a defect existing inside the yarn bundle.

The number of support rollers is preferably as small as possible from the viewpoint of deterioration of the yarn due to contact between the yarn and the roller and simplification of work efficiency. Usually, only one machine is sufficient, but the yarn bundle diameter is sufficient. 2-4 in case of large
It is desirable to combine the machines so that the presence or absence of defects can be detected at 2 to 4 locations on the outer surface of the yarn, so that the defective portions existing therein can be more surely exposed to the outside.

The yarn bundle used here is an assembly in which single yarns (long fiber filaments) are bundled as necessary. Note that the individual yarns are not integrated as a whole during the yarn bundle continuous transport heat treatment process, and if an external pressure such as being bent by a support roller is applied, the individual yarns are separated and become free. Therefore, the cross section of the yarn bundle in the bent state is flattened from a circular shape to an elliptical diameter.

Further, the detecting device according to the present invention can be set on the conveying path of each step of the yarn bundle continuous conveying heat treatment step. For example, in the case of a pitch-based carbon fiber manufacturing step, the carbonizing step It can be set on each conveyance path between the graphitization step and the graphitization step, between the graphitization step and the surface treatment step, and between the surface treatment step and the finished product winding step, if necessary.
Preferably, it is possible to reduce the burden of graphitization and surface treatment in the post process and to reduce the burden of the carbonization process by setting it on the transportation route between the carbonization process and the graphitization process. Therefore, it is more preferable, and it is more preferable to perform the process on the transport path between all the steps because the quality is stabilized.

[0026]

EXAMPLES Next, examples of the present invention will be described.

Embodiment 1 FIGS. 1 and 2 show a yarn flaw detection device 1 used in an embodiment of the present invention.
An embodiment is shown.

The yarn obtained by melt spinning the coal tar pitch (13 μm in diameter) was made into 3000 yarns, and the yarn bundle was made infusible and then carbonized at a temperature of about 1100 ° C. in a carbonization furnace. The yarn bundle 2 carbonized in this way is
After passing the guide rollers 3, 4, and 5 at a yarn speed of 4.5 m / min, the first support roller 6 having a radius of curvature of 10 mm was bent at a contact angle α of 20 °. The bent portion was optically detected by the first detecting means 7 to detect the defective portion.

As shown in FIG. 2, the detecting means 7 comprises a light projecting portion 8a and a light receiving portion 8b which are arranged to face each other in a straight line. A semiconductor laser (LX-
130), which was detected by the first pen recorder 9.

Next, the yarn bundle 2 was bent by the second support roller (radius of curvature 10 mm) 11 with the contact angle β being 20 °, and the defective portion was similarly detected by the second detecting means 14.

Using the above device, the yarn defect is detected,
The detection results on the outer surface of the first support roller 6 are shown in Table 1 and FIG. In addition, the second support roller 11
The same detection result (illustration and table are omitted) could be obtained on the outer surface (surface opposite to the first support roller). The detection output range of the received light amount of the light receiving portion of the sensor was set to 1 to 5 V, and this was compared with a preset detection value of the threshold light amount for defect detection = 3.0 V.

[0032]

[Table 1]

From the result of the yarn bundle defect detection, it is possible to detect the fused portion in the yarn bundle which cannot be detected or detected from the appearance of the yarn bundle, and set an appropriate threshold light amount detection set value according to the yarn diameter or the like. It was confirmed that this can be performed by setting, and that the detection of yarn defect sites such as fluffing, single yarn breakage, and yarn knots can also be detected.

[0034]

EFFECTS OF THE INVENTION The method and apparatus for detecting a yarn flaw of the present invention can detect the fused portion in the yarn bundle that cannot be detected or detected from the appearance of the yarn bundle, and also causes fluffing, single yarn breakage, Since it is also possible to detect the yarn defect portion such as the yarn knot portion, it can be widely used in each process, and the quality can be stabilized and the quality control work can be reduced. Furthermore, when detecting multiple yarn bundles at the same time,
It is possible to reduce the cost of detection devices such as sensors. Further, when one detection device is associated with one weight, the detection signal processing enables automatic bobbin exchange, and bobbin package processing that eliminates flaws is possible.

[Brief description of drawings]

FIG. 1 is a schematic view of an entire yarn flaw detection device used in this embodiment of the present invention.

FIG. 2 is a schematic diagram showing a positional relationship between a roller and a sensor of the yarn flaw detection device used in this embodiment of the present invention.

FIG. 3 is an enlarged schematic view of a defective portion of a yarn bundle obtained by the yarn flaw detection device used in the present embodiment of the present invention.

FIG. 4 is a graph showing the detection output of the amount of received light, which is obtained by performing yarn defect detection using the yarn flaw detection device of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thread defect detection device 2 ... Yarn bundle 3, 4, 5 ... Guide roller 6, 11 ... Support roller 7, 14 ... Detecting means 8 ... Sensor 8a ... Sensor light emitting part 8b ... Sensor light receiving part 9, 12 ... Pen Recorder 10, 13 ... Buzzer 15 ... Detection area

 ─────────────────────────────────────────────────── ─── Continuation of the front page Examiner Mitsuo Shiraishi (56) Reference JP 58-214577 (JP, A) JP 54-147255 (JP, A) JP 61-201020 (JP, A) Actual Kai 54-172050 (JP, U)

Claims (2)

(57) [Claims] 1. A yarn bundle continuous conveyance heat treatment step in the production of carbon fibers, wherein the yarn bundle is bent and conveyed at at least one location, and the yarn is based on a change in the amount of light received from the vicinity of the bent portion where light is irradiated. A method for detecting a yarn defect, which comprises detecting the presence or absence of a defect in a bundle. 2. A yarn bundle, which is a defect detection object, is provided on a conveying path of the yarn bundle, and the yarn bundle has a radius of curvature of 5 to the conveying direction.
20 mm, at least one support roller that bends at a contact angle of 10 to 90 °, and light projection so that a detection area is set in the yarn bundle in which the yarn bundle is bent by contacting the roller. Section and the light receiving section are arranged in a straight line so as to face each other, and the light receiving quantity of the light receiving section of the sensor is compared with a preset threshold light quantity for defect detection to detect defects in the yarn bundle. A yarn flaw detecting device comprising: a detecting unit for detecting.