JP3415538B2 - Disconnection prediction 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 wire breakage prediction device suitable for predicting a wire breakage of a cable.

[0002]

2. Description of the Related Art In general, when a cable used for a power line or the like is damaged, it is not possible to visually recognize the disconnection state of the core wire or the like from the outside. For example, to detect damage to the cable of a welding machine, the cable coating has a double structure, the outer coating is made of an insulating material, and the inner coating is made of a conductive (carbon-containing) rubber material. If a direct current voltage of about 9V is applied to the outer coating, the outer coating is damaged and the inner coating is grounded, and the ground resistance becomes 100Ω or less,
There is a cable damage alarm system that activates an alarm.

It is also known that a normal value of the current to the welding transformer is measured in advance and an alarm is issued when the current falls below a predetermined reference value.

[0004]

However, the above-mentioned conventional technique is to detect the damage of the coating to the last, and to know the damage in the middle of the complete breakage of the core wire due to repeated bending. There is a problem that you can not. Furthermore, of course, it is not possible to know the degree of disconnection of the core wire. Further, there is a problem that it cannot be detected during the operation of the device, and the damage of the core wire cannot be known until the operation of the device is stopped due to the disconnection of the electric current.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems and to reliably detect the disconnection state of a cable, the present invention has a movable part.
Connect the welding machine cable to the secondary side cable provided on the movable part.
Cable and the primary cable provided on the power supply side
With a power supply voltage detecting means for detecting a voltage of the primary cable, the load voltage detecting means for detecting the voltage of the secondary side cable, wherein the secondary voltage of the primary cable
Voltage difference detection means for detecting a voltage difference from the voltage of the side cable, and disconnection prediction determination means for detecting that the voltage difference is equal to or higher than a disconnection prediction voltage difference corresponding to a predetermined disconnection rate of the secondary cable. And an alarm means for outputting an alarm according to the detection result by the disconnection prediction determination means.

According to this, for example, when a cable having a core wire formed by bundling a plurality of twisted wires is used for a movable part of a device, all of the twisted wires are finally started after some of the twisted wires start to break. Since the cable breaks due to the disconnection of the cable, the number of stranded wires that can carry current decreases and the voltage on the load side of the cable decreases in the middle of the process. A voltage difference from the voltage is detected, and an alarm is output when the voltage difference becomes equal to or higher than a disconnection prediction voltage difference corresponding to a predetermined disconnection rate or higher. Therefore, the symptom can be notified before the complete disconnection.

According to the provision of the cable length adjusting means for adjusting the detected value of the load side voltage according to the cable length of each of the primary side cable and the secondary side cable, the voltage due to the cable length is provided. Highly accurate prediction that prevents the influence of descent can be performed.

Further, by providing the disconnection rate adjusting means capable of appropriately setting the disconnection rate to an arbitrary value, for example, when there is a difference in the usage frequency for each device, the cable replacement work after the disconnection prediction is performed. It is possible to set an appropriate disconnection rate in consideration of operating time.

Alternatively, the case of a welding machine having moving parts
Cable and power supply for the secondary side installed on the movable part
It is divided into the primary side cable provided on the side and
The voltage of the secondary-side cable and the load voltage detecting means for detect <br/> by energizing without weld object disconnection prediction for outputting a disconnection prediction voltage corresponding to a predetermined breakage rate of the secondary-side cable Voltage output means, disconnection prediction determination means for detecting that the voltage of the secondary side cable has become equal to or less than the disconnection prediction voltage, and alarm means for outputting an alarm according to the detection result by the disconnection prediction determination means. Good to have.

According to this, for example, at the time of inspection at the start of work, power is supplied without an object to be welded to detect a voltage on the cable load side, and a predetermined disconnection rate is compared with a preset disconnection prediction voltage. If it is determined that the above is the case, an alarm can be output as a sign of disconnection.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail based on specific examples shown in the accompanying drawings.

FIG. 1 is a schematic view showing the entire automatic welding machine to which the present invention is applied. As shown in the figure, the present welding machine performs welding with a hand 1 of a welding robot. A disconnection predicting device 2 as a disconnection detecting means is provided at an appropriate position of the multi-joint arm of the welding robot, and a secondary side cable 3 is connected between the hand 1 and the disconnection predicting device 2 and is separate from the welding robot. The primary side cable 5 is connected between the welding timer conductor 4 and the disconnection prediction device 2 installed in the. A welding voltage applying transformer 6 is attached to the hand 1 portion, and a secondary side detection cable 7 constituting a load voltage detecting means is connected to the primary coil side of the transformer 6.

FIG. 2 is a schematic circuit wiring diagram of the disconnection prediction device according to the present invention. As shown in the figure, transformer 6
The hand 1 of the welding robot is connected to the secondary coil, and each end (load side connection end) of each core wire 3u, 3v as the power line of the cable 3 is connected to the primary coil of the transformer 6. The remaining core wire 3w of the cable 3 is grounded. Also, each core wire 3u, 3v, 3 of the cable 3
The other end of w is connected to each corresponding terminal of the disconnection prediction device 2.

In the cable 3 according to this illustrated example, as shown in FIG. 3, the two-core detection cable 7 as well as the core wires 3u, 3v, 3w are covered by the insulating outer coating 3a of the cable 3. . Further, each element wire of each core wire 3u, 3v, 3w is covered with an insulating inner coating. In the illustrated example, the core wires 3u, 3v, 3w and the detection cable 7
Although the integrated cable 3 is used, a two-core cable may be combined with a conventional three-core cable depending on the use environment.

One end of each core wire 7a, 7b of the detection cable 7 is connected to each terminal connected to the transformer 6 of each core wire 3u, 3v, and the other end is inside the disconnection predicting device 2. It is connected to the disconnection prediction circuit 8 provided. The voltage on the transformer 6 side (voltage on the load side) of the secondary side cable 3 can be detected by the disconnection prediction circuit 8 via the detection cable 7.

The primary side cable 5 also includes the core wires 3
Each core wire 5u / 5v / 5w corresponding to u / 3v / 3w,
It is formed by a structure integrally including a two-core detection cable 9 which constitutes a power supply voltage detection means. Each core wire 5
One end of each of u, 5v, 5w is connected to each terminal of the disconnection prediction device 2 corresponding to each core wire 3u, 3v, 3w, and each core wire 9a, 9 of the detection cable 9 as the power supply voltage detecting means.
b is connected between the connection terminals of the core wires 5u and 5v on the welding timer conductor 4 side and the disconnection prediction circuit 8. Through this detection cable 9, the voltage at the power source side connection end of the primary side cable 5 can be detected by the disconnection prediction circuit 8.

Further, the disconnection predicting device 2 is provided with an external monitoring output terminal 2a for enabling the contact (for example, normally closed contact) output of the relay RY whose drive is controlled by the disconnection predicting circuit 8 to be output to the outside. At the same time, the power supply 10 for supplying power to the disconnection prediction circuit 8 is connected.

In the disconnection predicting device thus constructed, the disconnection predicting circuit 8 uses the welding timer conductor 4 side voltage of the primary side cable 5 and the hand 1 (transformer 6) side of the secondary side cable 3. The voltage is detected and compared, and when a voltage difference different from the initial value is generated between the detected voltages, it is determined that the wire is broken. This initial value may be set by the disconnection prediction circuit 8.

Next, the above disconnection prediction judgment will be described below with reference to a specific circuit example shown in FIG. This device is
Each core wire 3u on the load side (cable 3) of cable 3.5
Although the state leading to the 3v disconnection can be detected separately, FIG. 4 shows only one core wire 3u. The other core wire 3v may be the same as the circuit of FIG. 4, and its illustration and description are omitted.

As shown in FIG. 4, the core wire 9a of the primary side detection cable 9 is connected to the primary side cable length switching circuit 8a, and similarly, the core wire 7a of the secondary side detection cable 7 is connected to the secondary side cable length switching circuit. It is connected to 8b. Further, the core wire 5u of the primary side cable 5 and the core wire 3u of the secondary side cable 3
Are relayed by the disconnection prediction device 2 and connected to each other, but the relay connection point is the primary side cable length switching circuit 8a.
And the secondary side cable length switching circuit 8b.
The cable length switching circuits 8a and 8b are for generally adjusting the difference in the detected voltage due to the difference in the length of the cables 3 and 5, and are switched by the switch, the volume or the like in units of 1 m, or the analog. It can be continuously variable.

The output of the primary side cable length switching circuit 8a is input to the rectification / amplification circuit 8c which constitutes the power supply voltage detection means, and the output of the secondary side cable length switching circuit 8b constitutes the rectification / amplification which constitutes the load voltage detection means. Input to circuit 8d,
The outputs of the rectification / amplification circuits 8c and 8d are input to a common differential amplification circuit 8e. The differential amplifier circuit 8e is a dual rectifier
The difference between the output voltages from the amplifier circuits 8c and 8d is amplified and output to the balance display circuit 8f and the detection cable abnormality detection circuit 8k.

The output value of the one rectifying / amplifying circuit 8c is output as a detected value of the power supply side voltage and can be adjusted by the balance adjusting circuit 8g. Also,
The output of the rectification / amplification circuit 8c is output in parallel to the differential amplification circuit 8e to a signal detection timer circuit 8h and a disconnection rate adjusting circuit 8i as a disconnection rate setting means. In addition,
The balance adjusting circuit 8g makes it possible to adjust the initial value of the voltage detection value on the power source side when the apparatus is assembled to the welding machine.

The output terminal of the wire breakage rate adjusting circuit 8i is connected to a comparator circuit 8j as a wire break predicting means, and the output of the rectifying / amplifying circuit 8d is input to the comparator circuit 8j. The output end of the signal detection timer circuit 8h is connected to the comparison circuit 8j, the detection cable abnormality detection circuit 8k, and the balance display circuit 8f. Signal detection timer circuit 8
From h, a detection timer signal delayed by a predetermined time is output in order to judge in a stable state in the middle of the voltage except for unstable voltage at the start of welding and at the end of welding. With respect to the detection timer signal, for example, when the welding time is about 200 ms, the delay time from the start of welding is set to 80 ms, and the detection width is set to 60 ms. This may be appropriately set according to the voltage waveform during welding. The output voltage V1 of the disconnection rate adjusting circuit 8i and the output voltage V2 of the rectifying / amplifying circuit 8d are input to the comparison circuit 8j.

Then, both voltages V1.
When it is determined that the voltage difference between V2 (breakage prediction voltage difference) is equal to or more than a predetermined value, the relay RY is driven by the output from the comparison circuit 8j corresponding thereto, and the cable breakage abnormality indicator lamp LY is turned on. It has become. In this device, the relay RY is driven by the output of the detection cable abnormality detection circuit 8k, and the detection cable disconnection indicator light L
R lights up.

When the present apparatus is assembled to the welding machine, the above-mentioned balance adjusting circuit 8g can balance the voltage between the two rectifying / amplifying circuits 8c and 8d when the cable is new, and when the balance is achieved. The balance display lamp LG is turned on by the output of the balance display circuit 8f. Further, the disconnection rate adjusting circuit 8i sets the detection voltage of the primary side cable 5 to a value corresponding to an arbitrary disconnection rate (disconnection rate setting value), and the disconnection rate of the secondary side cable 3 reaches the disconnection rate set value. The comparison circuit 8j determines what has been done. In this way, it can be detected that the disconnection rate of the secondary cable 3 has exceeded the set value.

As for the disconnection rate, in the cable used in the welding machine as shown in this embodiment, each core wire is formed by bundling a plurality of stranded wires, and the total number of stranded wires in the core wire is It may be the ratio of the number of broken wires.
In the case of a single wire, it may be the area ratio of the non-conducting portion (for example, the portion lacking due to scratches) in the cross section.

In use, when the comparator circuit 8i detects that the output V2 of the rectifying / amplifying circuit 8d has become equal to or higher than the voltage V1 corresponding to the disconnection rate setting value by the disconnection rate adjusting circuit 8i as described above, the detection thereof is performed. The result signal drives the cable disconnection abnormality indicator LY and the relay RY as alarm means, and outputs an alarm to the outside.

In setting the disconnection rate, for example, WC
As a result of the experiment using the cable of T14 ^□ , the voltage of the node A shown in FIG. 4 is 5.9 when the disconnection rate is 0%.
Although it was V, it became 6.2 V when the disconnection rate was about 70%. The disconnection rate can be arbitrarily set (for example, 60% or 80%) based on the voltage change.

Further, when the secondary side detection cable 7 is broken, no voltage is generated at the node A. Therefore, when the detection cable abnormality detection circuit 8k detects the voltage drop, the detection result signal serves as an alarm means. The detection cable breakage indicator LR and the relay RY are driven in the same manner as above, and an alarm is output to the outside.

As described above, according to the present apparatus, since it is possible to detect and warn the state in which the secondary cable 3 is being completely disconnected, it is possible to operate the apparatus before it becomes impossible to operate due to the complete disconnection. It is possible to deal with it. For example, if it is confirmed that the degree of disconnection has progressed beyond a predetermined disconnection rate by lighting the cable disconnection abnormality indicator LY or the output of the relay RY, reconnecting the cable outside the line operation time has other effects. You can replace it with a new cable without giving it. Therefore, when applied to a device used in a line, it is advisable to set a wire breakage rate that can withstand a continuous operating time of one day or more as a predetermined wire breakage rate that serves as a reference for alarm generation.

A second embodiment according to the present invention will be described below with reference to FIGS. 5 and 6. Note that FIG. 5 corresponds to FIG. 2 described above, and FIG. 6 corresponds to FIG. 4 described above, and similar portions are denoted by the same reference numerals, and detailed description thereof will be omitted.
In this embodiment, as shown in FIG. 5, only the secondary side detection cable 7 for detecting the load side voltage is wired to the disconnection prediction device 12.

As shown in FIG. 6, this circuit includes a secondary side cable length switching circuit 8b, a rectification / amplification circuit 8d, a signal detection timer circuit 8h, and a disconnection rate adjusting circuit as a disconnection prediction voltage output means. 8i, a comparison circuit 8j, a detection cable abnormality detection circuit 8, a cable breakage abnormality indicator lamp LY,
The detection cable disconnection indicator LR and the relay RY are used.

In the present apparatus, the disconnection rate is set in advance by the disconnection rate adjusting circuit 8i in the same manner as described above, and for example, at the time of inspection at the start of work, electricity is supplied without a workpiece to be welded, Load side voltage detection value V2 and disconnection rate adjusting circuit 8 at that time
The output value of i (breakage prediction voltage) V1 and the comparison circuit 8j at the timing of the signal detection timer circuit 8h in the same manner as above.
When the voltage difference (V1-V2) becomes equal to or more than a predetermined value, the cable disconnection abnormality indicator lamp LY and the relay RY are output by the output from the comparison circuit 8j according to the result. Driven.

In this case, it is not possible to predict the disconnection in real time for each welding, but it is possible to confirm it by appropriately energizing without the object to be welded when necessary. In the case of welding cables, it is unlikely that the wire will be completely broken in an instant, and the progress of the wire breakage rate may be on a daily basis.As described above, sufficient confirmation of wire breakage can be made only by checking at the start of work. be able to. As a result, the circuit configuration can be further simplified, and the cost of the device can be improved.

A disconnection of the detection cable 7 (abnormality of the detection cable) can also be detected. In this circuit, the detected voltage is taken from the voltage input terminal to the secondary side cable length switching circuit 8b. ing. The detection voltage is detected by the detection cable abnormality detection circuit 8k at the timing of the signal detection timer circuit 8h, and the voltage becomes 0 potential at the time of disconnection. Therefore, depending on the detection result, the detection cable disconnection indicator lamp LR is output in the same manner as above. And the relay RY are driven.

The present invention is not limited to use in a welding robot, but can be applied to various general-purpose devices, and particularly movable cables for devices (motors, etc.) used with a large current. It is suitable for detecting the process leading to the complete disconnection, and the disconnection can be predicted and an alarm can be given to the outside. Incidentally, in order to perform highly accurate detection in accordance with each cable, electronic components may be replaced as appropriate.

[0037]

As described above, according to the present invention, the voltage difference between the voltage on the power source side and the voltage on the load side in the cable is detected, and the voltage difference increased due to the decrease in the voltage on the load side when the cable disconnection rate advances. When it is determined that the voltage has exceeded the disconnection prediction voltage difference corresponding to the predetermined disconnection rate, the sign of disconnection can be alerted to the outside, and the cable can be exchanged outside the line operation time accordingly, and You can prevent the cable from breaking and the line stopping in advance,
Planned repairs can be performed without affecting the line availability.

By adjusting the detection value of the load side voltage according to the cable length by the cable length adjusting means,
It is possible to make highly accurate predictions that prevent the effect of voltage drop due to cable length, and to set the disconnection rate to an arbitrary value using the disconnection rate adjustment means, for example, when there is a difference in the frequency of use for each device. By applying this device to various devices, such as setting the appropriate disconnection rate considering the operating time until cable replacement work after disconnection prediction,
The versatility of the device is improved.

Alternatively, even with a simple configuration in which the load side voltage of the cable is detected and compared with a disconnection prediction voltage corresponding to a predetermined disconnection rate of the cable, for example, no welding object is provided at the time of inspection at the start of work. The voltage on the cable load side is detected by energizing, and it is possible to determine that it has exceeded the predetermined disconnection rate by comparing with the preset disconnection prediction voltage, and an alarm is output if there is a sign of disconnection. Therefore, the structure of the disconnection predicting device can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an entire automatic welding machine to which the present invention is applied.

FIG. 2 is a schematic circuit wiring diagram of a disconnection prediction device according to the present invention.

FIG. 3 is a diagram showing a cross section of a cable to which the present invention is applied.

FIG. 4 is a block diagram of a disconnection prediction circuit according to the present invention.

FIG. 5 is a view corresponding to FIG. 2 showing a second embodiment according to the present invention.

FIG. 6 is a view corresponding to FIG. 4 showing a second embodiment according to the present invention.

[Explanation of symbols]

1 Hand 2 Disconnection Prediction Device 3 Secondary Side Cable, 3u / 3v Core Wire 4 Welding Timer Conductor 5 Primary Side Cable, 5u / 5v Core Wire 6 Transformer 7 Detection Cable 8 Disconnection Prediction Circuit 8a Primary Side Cable Length Switching Circuit, 8b Secondary Side Cable length switching circuit 8c / 8d Rectification / amplification circuit, 8e Differential amplification circuit, 8
f Balance display circuit 8g Balance adjustment circuit, 8h Signal detection timer circuit,
8i disconnection rate adjusting circuit 8j comparison circuit, 8k detection cable abnormality detection circuit 9 detection cable 12 disconnection prediction device 18 disconnection prediction circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-328775 (JP, A) JP-A-11-192551 (JP, A) JP-A-1-91977 (JP, A) Actual Kaihei 4- 60374 (JP, U) Actual development Sho 62-86980 (JP, U) Actual public Sho 54-37780 (JP, Y1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 19/165 G01R 31 / 02

Claims (4)

(57) [Claims] 1. A cable for a welding machine having moving parts
Provided on the secondary side cable provided on the movable part and on the power supply side
With divided into a primary side cables to be said, the power supply voltage detecting means for detecting a voltage of the primary cable, the load voltage detecting means for detecting a voltage of said secondary cable, the voltage of the primary-side cable and Secondary cave
A voltage difference detecting means for detecting a voltage difference between the voltage of Le, and breakage prediction discrimination means for detecting that the voltage difference becomes disconnected prediction than the voltage difference corresponding to a predetermined breakage rate of the secondary-side cable A disconnection prediction device, comprising: an alarm unit that outputs an alarm according to the detection result by the disconnection prediction determination unit. 2. The cable length adjusting means for adjusting the detection value of the load side voltage according to each cable length of the primary side cable and the secondary side cable is provided. The disconnection prediction device described in. 3. The wire breakage predicting apparatus according to claim 1, further comprising a wire breakage rate adjusting means capable of appropriately setting the wire breakage rate to an arbitrary value. 4. A cable of a welding machine having moving parts
Provided on the secondary side cable provided on the movable part and on the power supply side
With divided into a primary cable which is the voltage of the secondary side cable energized without welded object
A load voltage detecting means for detecting Ri, and disconnection predictive voltage output means for outputting a disconnection prediction voltage corresponding to a predetermined breakage rate of the secondary cable, the voltage of the secondary side cable falls below the disconnection prediction voltage A disconnection prediction device comprising: a disconnection prediction determination means for detecting that a disconnection is detected; and an alarm means for outputting an alarm according to the detection result by the disconnection prediction determination means.