JPH079450B2 - Shield cable defect detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect detecting device for a shielded cable, and more specifically, a defect occurs in a shield member formed on the outer periphery of a coated core wire to obtain a predetermined shielding effect. The present invention relates to an improvement of a device for detecting that it is no longer possible.

[Prior Art] In a shielded cable, when a shield member formed of metal tape or the like is formed on the outer periphery of a coated core wire due to a manufacturing defect and the covered core wire is exposed, the shielding effect of this portion is extremely deteriorated. Resulting in. For this reason, a defect detecting device for a shielded cable is inserted in the manufacturing line.

The basic principle of such a defect detecting device for a shielded cable is to supply a test signal to the conductor of the coated core wire that is running, and at the portion of the cable where the shield member and the jacket are molded on the outer periphery of the coated conductor, A detector is provided for detecting the presence or absence of a defect in the shield member by comparing the level of the leakage signal generated in the cable with a preset defect presence / absence determination level. This detection determines that there is no defect when the detected leak signal level does not exceed the predetermined defect presence / absence determination level, and determines that there is a defect when the leak signal level exceeds the defect presence / absence determination level. Has been done.

As a specific example of such a defect detecting device for a shielded cable, as an example of the defect detecting device applied when the shield member of the shielded cable is a metal tape, the one configured as shown in FIG. 2 is used. is there.

That is, the shielded cable 100 is manufactured as follows. That is, the coated core wire 1a drawn out from the coated core wire winding drum 1 is wrapped with a shield tape 2a made of a metal thin film drawn out from the shield member winding drum 2 by an appropriate means, and the outer periphery of the wound shield tape is wound. By molding the insulating sheath with the extruder 3, the shielded cable 100 is manufactured while traveling in the direction of arrow a.

The shaft of the drum 1 is connected to the slip ring 4,
A brush 5 is electrically contacted with the slip ring 4. The electrode terminals of this slip ring 4 are
It is electrically connected to the starting end of the conductor of the coated core wire 1a.

The shaft of the drum 2 is also connected to the slip ring 14, and the brush 15 is electrically contacted with the slip ring 14. Similarly to the above, the electrode terminal of the slip ring 14 is also electrically connected to the starting end of the shield tape 2a, and the electrode terminal of the brush 15 is grounded.

Further, the brush 5 has a test of the output of the amplifier 7 for amplifying the reference signal S ₀ of the reference signal generator 6 for generating an AC signal to a predetermined level with respect to the potential (ground potential) of the shield tape 2a. Signal Ri is provided.

In addition, the test signal Ri is transmitted via the slip ring 4 and the brush 5.
The coated core wire 1a, to which is supplied, passes through the monitor sensor 8, and the supply monitor signal Fi of the output of this monitor sensor 8 becomes the reference signal S _{1 which} is an AC signal of the reference level preset in the alarm setting device 9. If the output level of the supply monitor signal Fi is higher than the level of the reference signal S ₁ compared by the comparator 10, it is determined that the normal defect detection operation is performed, and the output level of the supply monitor signal Fi is If the level is lower than the level of the reference signal S ₁ , the signal form associated with the judgment that the conductor defect of the coated core wire 1a or the like occurs and the normal defect detection operation is not performed (for example, H level during normal operation). In case of abnormality, L level monitor signal M _NG
Will be sent to the appropriate next stage circuit.

The above-described comparator 10 is configured to have a function of once rectifying each input and converting it into DC and then comparing the DC signals because both the reference input signal and the comparison input signal are AC signals. There is.

On the other hand, the shielded cable 100 in which the shield member and the sheath are formed is passed through the sensor 11 for detecting a shield defect that detects a leak signal generated around the shielded cable 100 and then wound up on a winding drum (not shown) as a finished product. It has become.

The leak signal Di output from the sensor 11 is compared with the defect presence / absence detection signal S ₂ preset in the detection level setting device 12 by the comparator 13. Like the above-mentioned comparator 10, this comparator 13 is also configured to have a function of comparing DC signals.

The output level of the leakage signal Di is the defect detection signal S ₂
If smaller than the level, so completely covered core wire 1a with the shield member is covered with a discrimination result that no defect exists, when the output level of the leakage signal Di is greater than the defects in the detection signal S ₂ , There is a defect in the shield member, and the leakage of the signal supplied to the coated core wire 1a exceeds a predetermined value. Therefore, the signal form associated with the judgment that there is a shield defect (for example, at the normal H level (L level when abnormal)
The defect signal S _NG is sent to an appropriate next stage circuit.

[Problems to be Solved by the Invention] However, in the conventional example as described above, the drum 1
The wound core length of the coated core wire 1a wound on is different depending on the work content and wire type, and the wound length varies from several hundred Km to zero m even at the start and end of the work.

Therefore, the resistance component and the capacitance component of the winding length are not uniform, so that when the test signal Ri of the output of the amplifier 7 is supplied to the conductor of the coated core wire 1a, a substantial amount of the sensor 11 does not exist. The test signal application level changes. For this reason, the level of the leak signal Di detected by the sensor 11 also changes, and stable defect detection may not be possible.

Also, if the winding length is extremely long, the test signal Ri output from the amplifier 7 is significantly attenuated in the drum 1, and the cable in which this attenuated signal is supplied to the conductor of the coated core wire 1a is a sensor.
Since it is located at position 11, the substantial leakage signal level is extremely reduced, and even if the leakage signal is generated due to the defect of the shield member, the level of the leakage signal Di is the detection level setting unit 12 The reference signal S ₂ of
There is a possibility that the comparator 13 may determine that the operation is normal, and as a result, detection becomes impossible.

Incidentally, such various problems are not limited to the case where the shield member is formed of the shield tape 2 as shown in FIG. 2 and the case where the shield member formed of the braided wire or the like is formed is similar to the above. It happens.

Therefore, an object of the present invention is to provide a shielded cable capable of performing stable and reliable defect detection even if there is a change in resistance component or a change in electrostatic capacitance based on the winding length of a cable wound around a drum. It is to provide a defect detection device.

[Means for Solving Problems] A defect detecting device for a shielded cable according to the present invention includes a signal supply means for supplying a test signal to one end of a housed covered conductor, and a portion where the housed covered conductor is drawn out. And a shield member and an outer jacket on the outer periphery of the coated conductor which has passed through the first detection means and which detects the supply monitor signal level based on the leakage signal generated in the coated conductor of the same portion. And a second detecting means which is disposed at a portion of the molded cable and which detects the presence or absence of a defect in the shield member by comparing the level of the leakage signal generated in the cable with a preset defect presence / absence determination level. Controlling the output of the signal supply means so that the supply monitor signal level becomes constant, and supplying the signal when the supply monitor signal level exceeds a predetermined upper limit value. And a control means for limiting the output of the feeding means to control the defect presence / absence determination level of the second detection means to be low.

[Operation] The supply monitor signal level of the stored coated conductor is detected, and the supply monitor signal level to the defect detection portion in the coated conductor is made constant, thereby changing the winding length and the wire type of the stored coated conductor. It is possible to perform a reliable defect detection without being affected by the change of the resistance component and the change of the electrostatic capacitance based on the above mode.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIG. The present embodiment applies the present invention to the defect detection of a shielded cable in which a shield member is formed of a shield tape.

Since the region A surrounded by the broken line in FIG. 1 is the same as the member in FIG. 2 described above, its description is omitted and the same reference numerals are given.

In the figure, the brush 5 electrically connected to the starting end of the conductor of the coated core wire 1a via the slip ring 4 is supplied with the reference signal S ₁₀ of the AC output of the reference signal generator 21 from the potential of the shield tape 2a (ground potential). ) Is amplified to a predetermined level, and its gain is controlled (in this case, increased control) by a control signal T ₁ supplied via a switch 23a described later, which is an output of a test signal Ri. Is being supplied. The amplifier 22 is formed so that the output level thereof is limited to a predetermined upper limit value when the control signal T ₁ is circuitically separated and is not applied. this is,
This is because the safety to the human body was taken into consideration.

Then, the coated core wire 1a to which the test signal Ri is supplied is passed through the monitor sensor 8 which is the first detection means, and the output monitor signal of the output of the monitor sensor 8 is supplied.
Fi is the reference signal S ₂₀ preset in the setter 24 and the comparator 2
5, the control signal T ₁ corresponding to the difference level between the output level of the supply monitor signal Fi and the output level of the reference signal S ₂₀
Is created. This control signal T ₁ is supplied to the control end of the above-mentioned amplifier 22 via the switch 23a.

Therefore, when the switch 23a is turned on, the gain of the amplifier 22 is lowered when the supply monitor signal Fi is high,
Since the gain is increased when it is low, as a result, the signal supply level to the conductor of the coated core wire 1a at the portion of the monitor sensor 8 is kept constant. In addition, the gain of the amplifier 22 is set to a predetermined upper limit value when the switch 23a is turned on.

On the other hand, the supply signal Ri of the output of the amplifier 22 is
Is compared with the reference signal S ₃₀ previously set in the comparator 27,
When the output level of the test signal Ri exceeds the level of the reference signal S ₃₀ , it is determined that a dangerous voltage is applied to the conductor of the coated core wire 1a, the switch 23a is turned off, and the gain of the amplifier 22 is increased. Is maintained at a predetermined upper limit.

Now, the completed shielded cable 100 is wound as a finished product on a winding drum (not shown) after a leak signal generated around the sensor 11 which is the second detecting means is detected. It has become.

The leak signal Di of the output of the sensor 11 is the above-mentioned comparator 13
It is supplied to the comparison signal input terminal of the comparator 31 formed in the same manner as in FIG. 2 and compared with the reference signal S ₄₀ of the output of the amplifier 30 by the comparator 31. The reference signal S ₄₀ is generated by amplifying the reference signal S ₅₀ output from the detection level setting unit 29 with the amplifier 30. The reference signal S ₄₀ is normal when an applied signal to the conductor of the coated core wire 1 a (an applied signal in which the test signal Ri is controlled to be constant by the output of the monitor sensor 8) is given. Shielded cable 100
It is set to correspond to the allowable leakage level amount that will occur in.

On the other hand, the above-mentioned supply monitor signal Fi is supplied to one input of the divider 28 and the above-mentioned reference signal S is supplied to the other input.
₄₀ is supplied, and the same divider 28 divides the reference signal S ₄₀ / supply monitor signal Fi to obtain the control signal T ₂ .

The control signal T ₂ is supplied as a control input to the amplifier 30 via the switch 23b, and the amplifier 30
Causes the gain to decrease when the switch 23b is turned on and the control signal T ₂ is applied. Further, this switch 23b is a switch 2 operated by the output of the above-mentioned comparator 27.
In cooperation with 3a, the states of both switches 23a, 23b are different from each other, that is, when one side is on, the other side is off, and when one side is off, the other side is on.

Then, when the output level of the leakage signal Di is lower than the level of the reference signal S ₄₀ , it is judged that there is no defect because the covered core wire 1a is completely covered by the shield member, and the output of the leakage signal Di is output. If the level is higher than the level of the reference signal S ₄₀ , there is a defect in the shield member and the coated core wire
Since the leakage of the signal supplied to 1a exceeds a predetermined value, a defect detection signal S _NG in a signal form (for example, H level in a normal state and L level in an abnormal state) associated with the determination that there is a shield defect is generated. It is sent to the next stage circuit.

Here, when the level of the test signal Ri of the output of the amplifier 22 exceeds the level of the reference signal S ₃₀ preset in the upper limit value setting unit 26, a dangerous voltage is applied to the conductor of the coated core wire 1a. It is determined that the switch 23a is turned off, and the above-mentioned switch 23a is turned off, and the gain of the amplifier 22 is maintained at a predetermined upper limit value. At the same time, by turning on the switch 23b, the control signal T ₂ is applied to the amplifier 30, and the gain of the amplifier 30 is reduced. As a result, the level of the reference signal S ₄₀ decreases,
The so-called slice level is reduced.

The reason for doing this is based on the following reasons. That is, the magnitude of the leakage signal Di is proportional to the magnitude of the test signal Ri except for the output based on the defect of the shield part, and the detection sensitivity is the ratio of the reference signal S ₄₀ (slice level) to the leakage signal Di. It is determined. However, considering the noise margin and the like, even if the ratio of the reference signal S ₄₀ leakage signal Di is constant, it is more stable when used on the side where both levels are high. For this purpose, first the reference signal S ₄₀ is fixed at a high level and the leakage signal Di
The test signal Ri is adjusted to be large.
However, the test signal Ri cannot be increased above a certain level due to safety concerns. Therefore, when a sufficient detection signal cannot be obtained even when the test signal Ri is increased to a certain upper limit, a certain detection sensitivity is maintained by lowering the reference signal S ₄₀ at the expense of the noise margin. Of. This enables stable detection of defects in shielded cables.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained because the detection sensitivity when detecting a defect in the shielded cable and the test signal are automatically adjusted based on the supply monitor signal. is there.

(A) Since the supply signal level to the core wire based on the test signal is made constant even if the resistance component and the capacitance component of the winding length of the cable change, stable and reliable defect detection can be performed. (B) If the supply signal level rises to a dangerous voltage as the resistance component and the capacitance component of the cable winding length increase significantly, the supply signal level can be increased to a certain upper limit. Defect detection can be performed without lowering the sensitivity by suppressing the value to a value and lowering the slice level for comparison detection.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a defect detecting device for a shielded cable showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a defect detecting device for a conventional shielded cable. 1,2 …… Drum 1a …… Coated core wire 2a …… Shield tape 3 …… Extruder 4,14 …… Slip ring 5,15 …… Brush 8 …… Monitor sensor 11 …… Sensor 21 …… Reference signal generator 22,30 ...... Amplifier 23a, 23b ...... Switch 24 ...... Setting device 25,27 …… Comparator 26 …… Upper limit value setting device 28 …… Divisor 29 …… Detection level setting device 100 …… Shield cable

Claims (1)

[Claims] 1. A signal supply means for supplying a test signal to one end of a housed covered conductor, and a leakage signal generated in a covered conductor of the housed conductor arranged at a position where the housed covered conductor is pulled out. A first detecting means for detecting the supply monitor signal level; and a shield member and a jacket formed on the outer periphery of the coated conductor which has passed through the first detecting means.
By comparing the level of the leakage signal generated in the cable with a preset defect presence / absence determination level, second detecting means for detecting the presence / absence of a defect in the shield member and the supply monitor signal level are made constant. The output of the signal supply means is controlled, and when the supply monitor signal level exceeds a predetermined upper limit value, the output of the signal supply means is limited to control the defect presence / absence determination level of the second detection means to be low. A shielded cable defect detection apparatus, comprising: