JPH04245111A - Shield deficiency detecting method for shield electric wire - Google Patents

Abstract

PURPOSE:To detect shield defect surely and even on a manufacturing line of a shield electric wire. CONSTITUTION:In manufacturing a shield electric wire by surrounding a core 7 having a conductor 1 covered with an insulator 2 with a shield material 13, an AC signal is applied onto the core insulator 2 before being surrounded with the shield material 13 from a signal applying head 3 and an electric signal is induced to the core conductor 1. A signal detecting head 5 disposed for the shield electric wire after surrounding the core 7 with the shield material 13 detects an electric signal leaked from the core 7 surrounded with the shield material 13.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting shield defects in shielded wires.

0002

2. Description of the Related Art In general, a shielded wire is constructed by placing a shielding material vertically over a signal wire (core) made of a signal conductor coated with an insulator, and then covering the signal wire with a sheath. As a type of shielded wire, as shown in FIG. 3, a core 7 consisting of a core conductor 1 through which a signal flows is covered with a core insulator 2, and a drain wire 15 for the purpose of grounding are arranged in parallel. There is a pressure welding shielded wire whose entire periphery is covered with a shielding tape 13 made of metal such as aluminum or copper, and further provided with a sheath 14 made of an insulator.

Conventionally, the presence or absence of shielding defects during the manufacture of shielded wires has been inspected by connecting an applied signal oscillator 4 to the core conductor 1 at the lower end 18 of the finished shielded wire 12, as shown in FIG. At the same time, the drain wire 15 and the shield tape 13 are grounded, and the product bobbin 1
An AC signal in the audio frequency band (approximately 3 kHz) is placed on the core conductor 1 of the shielded wire 12 sent out from the wire 7, while the signal detection head 5 is brought into contact with the shielded wire 12 on the downstream side in the wire drawing direction shown by the arrow 16. The potential between the head 5 and the ground is monitored by a shield defect detector 6 to detect signals leaking from the shield defect.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the signal must always be applied to the terminal of the core 7, the signal application section (lower terminal 18) and detection unit (detection head 5)
Since the measurement distance between the shields changes and the output of the signal measured by the detector 6 changes accordingly, stable shield defect detection could not be performed. In addition, the lower terminal 1 of the product
The maximum wire distance that can be inspected from 8 to the detection head 5 is about 700 m, and in the case of a production line, the core is long and wound around a drum, making it impossible to detect shield defects on the production line. was.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a detection method that eliminates the above-mentioned drawbacks of the prior art and allows shield defects to be detected accurately and reliably even on a production line.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the shield defect detection method of the present invention provides a shield defect detection method for manufacturing a shielded wire by wrapping a core of a conductor covered with an insulator with a shielding material. An alternating current signal is applied from a signal application head to the core insulator before it is shielded to induce an electrical signal into the core conductor, and after the core is wrapped with a shielding material, a signal detection head installed on the shielded wire is used to detect the shielding. It detects electrical signals leaking from the core wrapped in material.

[0007]

[Operation] The present invention does not input signals to the core conductor of the shielded wire, but inputs electrical signals from the core insulator.
Signal input is performed by inducing a signal into the core conductor. That is, when an alternating current signal is applied to the core insulator from the application head to apply a voltage on the core insulator, a displacement current flows through the insulator and a current is induced in the core conductor based on the same principle as a capacitor. If a shielding defect, such as a sagging shield tape, exists in the shielded wire to be taken, the detection head detects potential leakage from the defective portion.

[0008] Since the signal for shield defect detection is applied not to the core conductor but from the core insulator, it is possible to apply the signal regardless of the core delivery winding amount for manufacturing the shield wire. . Furthermore, the distance between the signal application head and the detection head can always be kept constant, making it possible to perform accurate and reliable defect detection.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the basic configuration. The left side of the figure is a signal application section that targets a signal line (core) 7 consisting of a core conductor 1 and a core insulator 2, and the right side of the figure is a signal application section after applying a shielding tape 13 as a shielding material on this core 7. This is a shield defect detection unit that targets shielded wires (finished products). Although this embodiment deals with shielding by wrapping metal tape such as aluminum tape or copper tape, it can also be applied to shield defect detection in shielding by braiding or horizontal winding. Further, the material of the core insulator 2 may be any thermoplastic resin such as polyvinyl chloride, polyethylene, or polypropylene.

The signal application section includes a signal application head 3 made of brass roll electrodes that contacts the core insulator 2 from above and below, and an oscillator 4 that applies a sinusoidal AC signal between the signal application head 3 and the ground. It is configured. On the other hand, the shield defect detection section detects the shield tape 13 and the insulator sheath 1.
A signal detection head 5 consisting of a brass roll electrode that contacts the shielded wire (finished product) 12 from above and below after step 4 has been applied.
and a signal detector 6 that monitors the potential appearing between the detection head 5 and ground.

When an alternating current signal is applied to the core insulator 2 from the application head 3, the insulator 2 acts as a dielectric, and a displacement current flows through the insulator 2, based on the same principle as a capacitor.
This induces a current in the core conductor 1. If a shielding defect (tape dripping) exists in the shielded wire 12 to be taken over, potential leaks from the defective portion, is detected by the signal detector 6 via the detection head 5, and an alarm is generated.

The frequency of the sinusoidal AC signal applied to the core insulator 2 by the oscillator 4 is 1.5 k in the audible frequency band.
~3kHz is appropriate. This is because low frequencies are more susceptible to noise generated by peripheral equipment, and higher frequencies (~
MHz), the dielectric constant ε of the insulator may vary and the output on the detection side may decrease. Further, it is sufficient that the voltage level of the applied signal is 3 kV or less. The distance from the signal application head 3 to the detection head 5 is suitably 5 to 15 m. Here, an oscillator 4 generates a 1 kV, 3 kHz sinusoidal AC signal, which is applied to the core insulator 2 from the signal application head 3, and the detection head 5 located approximately 10 m away from the application head 3 and the signal The detector 6 detects the signal leaked from the shield defect in terms of potential.

In this shield defect detection method, an audio frequency signal for detecting shield defects is applied not to the core conductor 1 but from the core insulator 2. Inspection for shielding defects can be performed in-line in the shielded wire manufacturing line regardless of the quantity.

FIG. 2 shows this example, in which the core 7 (conductor 1, insulator 2) is sent out from the core delivery drum 9.
are arranged parallel to the drain wire 15 fed out from the drain wire feeding drum 8, and are wrapped and covered with the shield tape 13 fed out from the shield tape feeding drum 10. After that, the extruder crosshead 11
After the sheath 14 made of an insulator is extruded and molded, it is pulled off in the direction of arrow 16 as a finished shielded wire 12. In this production line, the signal application head 3 is provided upstream from the confluence point of the core 7 with the drain wire 15, and the shield defect detection section is installed on the shielded wire 12 after exiting the extruder crosshead 11. It is provided for.

When an alternating current signal is applied from the application head 3 to the core insulator 2 before being wrapped with the shielding tape 13 and a current is applied, the insulator 2 acts as a dielectric and a displacement current flows through the insulator 2, thereby causing the core conductor to A current is induced in 1. Thereafter, the core 7 is shielded with a shield tape 13, and the shield tape 13 is grounded. The signal detection head 5 detects electrical signals leaking from the core wrapped in the shield tape 13 through the shield tape 13. Therefore, when a shielding defect (tape dripping) occurs in the manufactured shielded wire 12, potential leakage from the defective portion is detected by the detection head 5 on the same line, amplified, and an alarm is generated.

In the above embodiment, a contact type detection head 5 using a roll or the like is used, but the detection head 5 can also be configured to perform non-contact detection using electromagnetic wave coupling.

[0018]

In summary, according to the shield defect detection method of the present invention, the signal for shield defect detection is applied not to the core conductor but from the core insulator. Shield defects can be inspected over the entire length of the shielded wire, regardless of the amount of winding. That is, detection of shield defects, which conventionally could only be achieved up to a length of about 700 m, can now be detected even on longer products. As a result, even wires with a core length of 20 to 30 km, such as aluminum one-touch wire, can now be detected in-line during jacket extrusion, which previously required inspection while rewinding the finished jacket product in a separate process. can be omitted. Furthermore, since the interval distance between the signal application section and the shield defect detection section is always constant, accurate and reliable defect detection can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the basic configuration of a shield defect detection method of the present invention.

FIG. 2 is a schematic explanatory diagram showing an embodiment of the shield defect detection method of the present invention.

FIG. 3 is a schematic explanatory diagram showing a conventional shield defect detection method.

[Explanation of symbols]

1 Core conductor 2 Core insulator 3 Signal application head 4 Applied signal oscillator 5 Signal detection head 6 Shield defect detector 7 Core 8 Drain wire delivery drum 9 Core delivery drum 10 Shield tape delivery drum 11 Extruder crosshead 12 Shielded wire (finished product) 13 Shield tape 14 Insulator sheath 15 Drain wire 16 Arrow in line drawing direction 17 Product bobbin 18 Product lower terminal

Claims (1)

[Claims] Claim 1: When producing a shielded wire by wrapping a core of a conductor covered with an insulator with a shielding material, an alternating current signal is applied from a signal application head onto the core insulator before it is wrapped with the shielding material, and the core conductor is After the core is wrapped with a shielding material, a signal detection head provided on the shielded wire is used to detect the electrical signal leaking from the core wrapped in the shielding material. Method for detecting shield defects in shielded wires.