JP4318826B2 - Welding cable abnormality detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detection device for a welding cable that detects an abnormality such as a ground fault of a welding cable connecting a welding power source device and a welding transformer in a resistance welding robot or the like.
[0002]
[Prior art]
Recently, a resistance transformer that places a welding transformer near the gun arm and supplies a primary AC voltage of about several hundred volts to the primary coil of this welding transformer from a welding power source via a welding cable is in use. It is provided. In this resistance welding apparatus, the primary AC voltage is stepped down to a voltage of about several volts or less by the welding transformer, and a large current of, for example, about tens of thousands of amperes can be supplied to the workpiece.
[0003]
By using a resistance welding device with such a configuration, the welding cable can be made relatively thin, so it has excellent mobility and can move the gun arm at high speed in the case of multi-point welding of workpieces, etc. Become.
[0004]
However, in a resistance welding apparatus having a welding cable that is moved in this manner, there is a possibility that the resin coating of the welding cable is peeled off due to scratching or the like and the core wire is grounded.
[0005]
As a device for detecting this ground fault, a technique disclosed in Japanese Patent Application Laid-Open No. 59-127777 (referred to as a first technique) and a technique disclosed in Japanese Utility Model Laid-Open No. 7-15175 (referred to as a second technique). .).
[0006]
In this first technique, an insulation transformer is provided between the welding power source and the primary side of the welding transformer, and a current detector is connected between the core wire of the secondary side welding cable (movable cable) of the insulation transformer and the ground. When a ground fault occurs in the welding cable, the occurrence of the ground fault is detected by the current flowing through the current detector.
[0007]
In the second technique, a shield wire is disposed in the resin that is the insulation coating of the weld cable, and insulation is provided between the shield wire and the inner conductor (core wire) of the weld cable and between the shield wire and the work potential. A circuit is provided, and a ground fault between the shield wire and the core wire and a ground fault between the shield wire and the work potential are detected by outputs of these two insulation circuits.
[0008]
[Problems to be solved by the invention]
However, in the first technique, since an insulating transformer is provided between the welding power source device and the primary side of the welding transformer, the current efficiency of welding by this insulating transformer is reduced, and the insulating transformer is expensive. Therefore, there is a problem that the resistance welding apparatus itself increases in cost.
[0009]
In the second technique, an abnormality detection circuit is required for both a ground fault between the shield wire and the core of the welding cable and a ground fault between the shield wire and the work potential, and the circuit configuration is complicated. In addition, there is a problem that the cost is increased, and further, since it is necessary to draw out the core wire, which is normally at a high voltage, with the lead wire, this lead wire also requires a high-voltage insulation coated wire, which also increases the cost. is there.
[0010]
The present invention has been made in consideration of such problems, and an object of the present invention is to provide a welding cable abnormality detection device that has a simple configuration and that does not require drawing out the core wire of the welding cable.
[0011]
Another object of the present invention is to provide a welding cable abnormality detection device that can be configured at low cost.
[0012]
[Means for Solving the Problems]
  This inventionAnomaly detection device for welding cableIs a welding cable that supplies power to the primary coil of the welding transformer(30)In the abnormality detection apparatus, the welding cable(30)Insulated conductors for power supply(53)And the insulated coated conductor(53)Flexible conductive material covering(64)And the conductive material(64)Flexible insulating material covering(66)And the conductive material(64)Floating DC power supply between ground and ground(92)And the DC power supply(92)Anomaly detection circuit that detects potential fluctuations(48)TheThe abnormality detection circuit (48) is configured such that the voltage (Ed) between the positive terminal (Q) and the negative terminal (P) of the floating DC power source (92) is divided by the voltage dividing means (94, 96). A divided voltage potential (Ea) is supplied to the negative input terminal, the ground potential is supplied to the positive input terminal, and the positive terminal (Q) of the floating DC power source (92). A first diode (85) connected to the other end of the first resistor (84), one end of which is connected to the flexible conductive material (64); A second diode having an anode terminal connected to the positive input terminal at the ground potential and a cathode terminal connected to a common connection point of the cathode terminal of the first diode (85) and the first resistor (84). (86) and one end is the above A second resistor (102) connected to the positive input terminal having a round potential and having the other end connected to the negative terminal (P) of the floating DC power source (92). When the conductive material (64) has a ground fault with the ground, or when the conductive material (64) has a ground fault with the core wire (51) of the insulating film conductor (53) The potential on the negative terminal (P) side of the DC power source (92) is floated and the potential on the positive terminal (Q) side is floated by the voltage drop generated by the current flowing through the second resistor (102). The divided potential (Ea) is changed to invert the output of the comparator (90).It is characterized byThe
[0013]
According to the present invention, an abnormality detection circuit that operates with a floating DC power supply is provided between a flexible conductive material that covers the insulation-coated conductor for supplying power and the ground, and the abnormality detection circuit allows the DC power supply to be Since the potential fluctuation is detected, an abnormality such as a ground fault of the welding cable can be detected based on the potential fluctuation of the DC power source.
[0014]
In this case, when a DC potential fluctuation of the DC power supply is detected, an abnormality detection output for detecting a ground fault occurring between the conductive material and the ground can be generated. Invention), when an AC potential fluctuation of the DC power source is detected, as an abnormality detection output for detecting a ground fault occurring between the core of the insulation coated conductor for supplying power and the conductive material, An on / off abnormality detection output using dynamic potential fluctuation can be generated (invention of claim 3).
[0015]
In addition, an isolation means that is insulated from the abnormality detection circuit is connected to the output side of the abnormality detection circuit, and when abnormality in the potential of the DC power supply is detected, an abnormality detection output is generated via the isolation means. Thus, an isolated output can be obtained as the abnormality detection output (the invention according to claim 4).
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a schematic external configuration in which various mechanical drive mechanisms of a resistance welding apparatus 10 to which an embodiment of the present invention is applied are omitted.
[0018]
The resistance welding apparatus 10 includes a welding robot 11, a welding power supply device 32 that supplies a welding power source to the welding robot 11, and a robot (not shown) that controls operations of the welding power supply device 32 and the welding robot 11. It is basically composed of a controller.
[0019]
The welding robot 11 has a base 14 that is disposed on the floor 12 and is movable in the direction of the arrow. A rotary base 16 that rotates in the horizontal direction is provided on the base 14. An arm 20a is attached via a joint 18a that rotates in the direction of the arrow. A joint 18b that rotates in the direction of the arrow and a joint 21 that rotates in the direction of the arrow via the arm 20b are attached to the tip of the arm 20a, and the welding transformer 22 is integrally fixed to the joint 21. Yes.
[0020]
The output side of the welding transformer 22 is connected to the base side of a conductive welding gun (gun arm) 26 that is controlled to open and close by a cylinder 24 in the direction of the arrow.
[0021]
A pair of welding tips 28 for attaching the workpiece W to the front end side of the welding gun 26 is attached.
[0022]
In this case, the input side of the welding transformer 22 is connected to a welding power source device 32 via a flexible welding cable 30. In this case, the welding cable 30 is connected to the welding transformer 22 from the welding power source device 32 using the internal space of the welding robot 11.
[0023]
FIG. 2 shows a schematic block configuration of an electric circuit from the welding power source device 32 to the welding tip 28.
[0024]
The welding power supply device 32 includes a converter circuit 42 that performs full-wave rectification of the alternating current output from the external alternating current power supply 41, an inverter circuit 44 that repeatedly converts the direct current output from the converter circuit 42 into a square-wave high-frequency alternating current, and an inverter A welding controller 40 for controlling the circuit 44 and an abnormality detection circuit 48 which is a point of the present invention are provided.
[0025]
The high-frequency alternating current generated in the inverter circuit 44 is supplied to the primary coil side of the welding transformer 22 in which the rectifying diode is integrally incorporated via the welding cable 30, and the welding transformer 22 outputs the secondary coil side output. The rectified output is supplied to the welding gun 26 by rectification.
[0026]
FIG. 3 shows a detailed circuit of the abnormality detection circuit 48, a schematic configuration of the welding cable 30, and a configuration of a circuit connected to the input / output side of the flexible welding cable 30.
[0027]
The welding cable 30 is for grounding having two flexible insulated conductors 53 for power supply each having a core wire 51 and an insulating coating 52, and a core wire 61 and an insulating coating 62. Insulating coated conductor 63 having flexibility, flexible conductive material 64 such as conductive rubber embedded so as to cover these insulated coated conductors 53, 63, and the entire conductive material 64 are insulated from an external ground or the like. In order to do so, it is composed of an insulating material (also referred to as a coating) 66 which is a flexible coating such as butyl rubber. As the flexible conductive material 64, a braid which is a shield wire can be used instead of the conductive rubber.
[0028]
In FIG. 3, the converter circuit 42 is schematically represented by two positive and negative DC power sources 42a and 42b that generate voltages + E1 and -E1. Here, the inverter circuit 44 basically includes four transistors 46a, 46b, 46c, and 46d, and the base terminals of these transistors 46a to 46d are on / off controlled through the welding controller 40 (see FIG. 2). .
[0029]
A DC power supply 42a is connected to the collector terminals of the transistors 46a and 46c, and a DC power supply 42b is connected to the emitter terminals of the transistors 46d and 46b.
[0030]
The emitter terminal of the transistor 46 a and the collector terminal of the transistor 46 d are connected, and the common connection point is connected to the core wire 51 of one insulation-coated conductor 53. In addition, the emitter terminal of the transistor 46 c and the collector terminal of the transistor 46 b are connected, and the common connection point is connected to the core wire 51 of the other insulated wire 53. Further, the insulation coated conductor 63 is grounded (also referred to as ground or earth) on the welding power supply device 32 side.
[0031]
The core wire on the opposite side of the insulation coated conductor 63 is also grounded on the welding transformer 22 side. Further, the opposite sides of the two insulation-coated conductive wires 53 are connected to the primary coil 22 a of the welding transformer 22. The output of the secondary coil 22b of the welding transformer 22 is connected to the anode terminal side of the rectifying diodes 70 and 72, respectively, and the cathode terminals of the rectifying diodes 70 and 72 are connected in common to one input of the welding gun 26. Connected to the side. The intermediate tap of the secondary coil 22 b is connected to the other input side of the welding gun 26. As described above, the welding tip 28 is detachably attached to the tip of the welding gun 26.
[0032]
The conductive material 64 disposed on the inner side of the sheath 66 of the welding cable 30 is connected to the core wire on one end side of the insulation coated conductor 80, and the core wire on the other end side is the in-phase transformer constituting the abnormality detection circuit 48. 82 is connected to the coil end of one of the coils 82a. The other end of the coil 82a is connected to cathode terminals of diodes 85 and 86 functioning as gate means via a resistor 84.
[0033]
The abnormality detection circuit 48 further includes a comparator 90 as a comparison circuit (comparison means) constituted by an operational amplifier. The power supply terminal of the comparator 90 is a floating power supply different from the welding power supply by the welding power supply device 32. Is connected to a DC power source 92 having a low voltage (here, voltage value Ed = 24 [V]). Here, the positive terminal of the DC power source 92 is also referred to as a reference point Q, and the negative terminal is also referred to as a reference point P. The floating DC power source 92 is a power source in which the reference points P and Q are simultaneously changed by the same potential while the terminal voltage Ed remains unchanged with respect to the infinity point reference (ground reference).
[0034]
As will be described in detail later, when the abnormality detection circuit 48 detects a ground fault or the like of the welding cable 30 through the insulation coated conductor 80, the potential fluctuation of the DC power source 92, in other words, the reference points P and Q It is possible to detect the fluctuation of the ground reference potential difference by the comparator 90 and output the abnormality detection output Sout corresponding to the type of ground fault.
[0035]
Resistors 94 and 96 are connected to the negative input terminal of the comparator 90 as voltage dividing means for dividing the inter-terminal voltage value Ed of the DC power supply 92. Here, the reference voltage Ea appearing at the negative input terminal is set to Ea = about 4 × Ed / 24 [V] = 4 [V] in a normal state.
[0036]
  On the other hand, the positive input terminal of the comparator 90 includes the anode terminal of the diode 98 whose cathode terminal is connected to the reference point Q, the capacitor 100 and the resistor 102 connected in parallel to the reference point P, and the other coil of the common-mode transformer 82. It is connected to one coil end of 82b. The other coil end of the coil 82b is grounded.. ThisHere, the voltage appearing at the positive input terminal of the comparator 90 is referred to as a comparison voltage Eb.
[0037]
A bias resistor 104 is connected to the positive terminal of the DC power source 92 at the output terminal of the comparator 90, and the cathode terminal of the light emitting diode 108 constituting the photocoupler 106 as an isolation means (isolation circuit). Connected. The anode terminal of the light emitting diode 108 is connected to the positive terminal of the DC power source 92 through the resistor 109.
[0038]
An abnormality detection output Sout is generated between the output terminals 112 and 114 to which the collector terminal and the emitter terminal of the phototransistor 110 constituting the photocoupler 106 are connected. Note that the photocoupler 106 as the isolation means can be replaced with an electromagnetic relay. Any isolation means may be used as long as the output can be optically, electromagnetically or electrostatically isolated (insulated).
[0039]
The resistance welding apparatus 10 according to this embodiment is basically configured as described above, and the operation thereof will be described next.
[0040]
First, the overall operation of the resistance welding apparatus 10 will be described. When the workpiece W is positioned and placed in a state where the resistance welding apparatus 10 is powered on, the welding gun 26 of the welding robot 11 moves in the playback mode to a position where the workpiece W is sandwiched by a robot controller (not shown). Is done.
[0041]
That is, based on the teaching data prepared in advance, the base 14, the turntable 16, the joints 18a, 18b, 21 and the arms 20a, 20b are driven by a predetermined amount of movement, so that the welding gun 26 in the open state is opened. The welding tip 28 is moved to a position where the welding tip 28 faces through the workpiece W.
[0042]
Next, the welding gun 26 is closed by the cylinder 24, and pressure is applied to the workpiece W via the welding tip 28. As described above, when a pressing force is applied to the workpiece W via the welding tip 28 by the welding gun 26, the welding power source device 32 is driven for a predetermined time by a command from the robot controller.
[0043]
That is, the positive and negative direct current power sources 42a and 42b of the voltages + E1 and −E1 generated by the converter circuit 42 based on the alternating current power source from the external alternating current power source 41 are controlled by the welding controller 40 to form a transistor 46a that constitutes the inverter circuit 44. ˜46d is supplied to the welding cable 30 side by being on / off controlled for a predetermined time.
[0044]
In this case, when the transistors 46a and 46b are in the on state and the transistors 46c and 46d are in the off state, the current flowing out from the positive terminal of the voltage E1 of the one DC power supply 42a is the transistor 46a and the one insulation-coated conductor 53. A core wire 51 on one end side of the wire, in the welding cable 30, a core wire 51 on the other end side of the one insulation-coated conductor 53, one end portion of the primary coil 22a of the welding transformer 22, and other than the primary coil 22a. One end of the other end of the other insulation-coated conductor 53, the welding cable 30, the other end of the other insulation-coated conductor 53, through the core 51, the transistor 46 b, and the other DC power supply 42 b Return to the negative terminal of voltage -E1.
[0045]
Similarly, when the transistors 46a and 46b are in the on state and the transistors 46c and 46d are in the off state, the current flowing from the positive terminal of the voltage E1 of the one DC power supply 42a is changed to the transistor 46c and the one insulation-coated conductor. 53, one end of the welded coil 30, the other end of the one insulation-coated conductor 53, one end of the primary coil 22a of the welding transformer 22, the other end of the primary coil 22a, and the other insulation-coated conductor 53. It returns to the negative terminal of the voltage -E1 of the other DC power supply 42b through the transistor 46d through one end, the welding cable 30, and the other end of the other insulation-coated conductor 53.
[0046]
By repeating such an operation for a predetermined time, a repetitive square wave voltage with an amplitude of + E1 to −E1 is applied to the core wire 51 (primary coil 22a) of the insulation coated conductor 53 as shown in FIG. The
[0047]
This repetitive square wave voltage is stepped down and induced in the secondary coil 22b, rectified by the diodes 70 and 72, and applied to the workpiece W through the welding gun 26 and the welding tip 28 as a DC voltage. At this time, for example, the secondary current value flowing through the workpiece W or the primary current value flowing through the primary coil 22a is detected by a current detector (not shown) and supplied to the welding controller 40, whereby the current value is fed back. Control is performed, and a desired current is supplied to the workpiece W at a desired pressure for a desired time, and the workpiece W is suitably welded.
[0048]
After the welding process on the workpiece W, the drive of the inverter circuit 44 by the welding controller 40 is stopped, the welding gun 26 is opened by the cylinder 24, and the welding gun 26 starts moving to the next spot position.
[0049]
In this way, the welding operation for the workpiece W by the resistance welding apparatus 10 is performed.
[0050]
Next, in the resistance welding apparatus 10 in the power-on state, an abnormality detection operation (ground fault detection operation) for the welding cable 30 by the abnormality detection circuit 48 will be described. The abnormality detection operation in the abnormality detection circuit 48 is performed by so-called internal damage (conducting with the core wire 51 of the insulation-coated conductive wire 53) of the welding cable 30 based on the potential difference between the reference voltage Ea and the comparison voltage Eb generated at the positive and negative input terminals of the comparator 90. This is an operation for discriminating between an abnormal state such as a ground fault with the material 64) or a trauma (a ground fault between the conductive material 64 and the ground generated when the coating 66 is broken) and a normal state.
[0051]
A. Explanation of detection operation when welding cable 30 is normal
When the welding cable 30 is normal, the reference voltage Ea set by the voltage dividing ratio of the resistors 94 and 96 is about 4 [V]. At this time, the comparison voltage generated at the positive input terminal of the comparator 90 Since the voltage Eb is grounded via the coil 82b of the in-phase transformer 82, Eb = 0 [V]. Therefore, the output of the comparator 90 is at a low level.
[0052]
  Therefore, a resistor is connected from the DC power source 92 to the light emitting diode 108 constituting the photocoupler 106.109A current flows through the output phototransistor 106, and the output phototransistor 110 of the photocoupler 106 is turned on. The phototransistor 110 has a pull-up configuration in which one output terminal 114 is connected to the ground of a monitor circuit (not shown) and current is supplied to the other output terminal 112 from a positive DC power source through a resistor. The abnormality detection output Sout that operates as an open collector circuit and is supplied to the monitor circuit is in a low level stationary state (DC state) representing normality. In the following description, it is assumed that the phototransistor 110 operates as such an open collector circuit.
[0053]
B. Description of detection operation in the case where the welding cable 30 is damaged
As schematically shown in FIG. 4, when a damage occurs on the covering (outer skin) 66 of the welding cable 30, a ground fault occurs when the conductive material 64, which is a conductive resin inside the welding cable 30, contacts the ground. appear.
[0054]
At this time, the current i flowing out from the positive terminal of the DC power source 92 of the abnormality detection circuit 48 flows to the ground G1 through the diode 85, the resistor 84, the coil 82a, the insulating coating conductor 80, and the conductive material 64. Further, the capacitor 100 is charged by the current i flowing from the ground G 1 through the ground G 2 and the other coil 82 b of the common-phase transformer 82, and the current i flows into the negative terminal of the DC power source 92 through the resistor 102. Since the diode 85 is forward biased, the diode 85 is opened when the diode 85 is considered as a gate means.
[0055]
  in this case,The potential of the negative terminal (reference point P) of the DC power source 92 floats (decreases) by a voltage drop obtained by multiplying the current i flowing through the resistor 102 by the resistance value of the resistor 102. At the same time, the positive terminal (reference point Q) of the DC power supply 92 is floated (decreased), the reference voltage (reference potential) Ea is lowered, and the reference voltage Ea at this time is lower than the ground potential.By setting the resistance values of the resistor 84 and the resistor 102 so as to be at a potential, the comparator 90 is inverted when the conductive material 64 is grounded, and the output voltage of the comparator 90 becomes high level. For this reason, the photocoupler 106 is turned off, and the abnormality detection output Sout is held at a DC high level output indicating an abnormality in the trauma. In this state, the DC power source 92 generates a DC potential fluctuation, and as a result, the DC potential fluctuation is detected by the comparator 90.
[0056]
C. Explanation of detection operation when internal damage has occurred in welding cable 30
As shown in the broken part of FIG. 5, when the sheath 52 of the insulation coated conductor 53, which is a power supply conductor inside the welding cable 30, is broken to cause internal damage, and the core wire 51 and the conductive material 64 come into contact with each other. Will also cause a ground fault.
[0057]
In this case, a positive voltage + E1 (+300 [V] in this embodiment) and a negative voltage −E1 (−300 [V] in this embodiment), which are high-frequency alternating current, are alternately generated in the core wire 51, Therefore, the positive voltage + E1 and the negative voltage −E1 having the same potential as those of the conductive material 64 are alternately generated.
[0058]
When the positive voltage + E1 is applied to the conductive material 64 due to a ground fault, the positive voltage + E1 is applied to the cathode terminals of the diodes 85 and 86 as the gate means, so that a reverse bias is applied and the off state (the gate means is closed). Therefore, the output of the comparator 90 becomes a low level in the same non-inversion state as in the normal state.
[0059]
However, when the negative voltage −E1 is applied, as shown in FIG. 6, the diodes 85 and 86 are turned on (open as gate means), so that the potential fluctuation of the DC power source 92 occurs and the reference voltage is applied. Ea is lower than the comparison voltage Eb. In other words, the comparison voltage Eb becomes higher than the reference voltage Ea, and the output of the comparator 90 becomes an inverted high level.
[0060]
Therefore, when a ground fault occurs in which the core wire 51 comes into contact with the conductive material 64, the comparator 90 detects an AC potential fluctuation of the DC power supply 92, and as a result, the abnormality detection output Sout is turned on and off. Repeated abnormality detection output.
[0061]
As described above, according to the above-described embodiment, the abnormality detection circuit 48 that operates with the floating DC power source 92 is provided between the flexible conductive material 64 that covers the insulation-coated conductor 53 for supplying welding power and the ground. Since the fluctuation of the potential of the floating DC power supply 92 is detected by the comparator 90 constituting the abnormality detection circuit 48, a ground fault of the welding cable 30 is detected based on the potential fluctuation of the DC power supply 92 caused by a ground fault or the like. Abnormality can be detected.
[0062]
Basically, the resistors 94 and 96 are set to resistance values that make the reference voltage Ea higher than the comparison voltage Eb so that the output of the comparator 90 is in a non-inverted state when no ground fault occurs. Set it. Then, when a ground fault occurs such that the coating 66 of the welding cable 30 is broken and comes into contact with the ground, when the DC power supply 92 floats, the resistor / diode is set so that the reference voltage Ea becomes lower than the comparison voltage Eb. The comparator 90 is inverted by determining the circuit configuration / value of the capacitors (84, 85, 86, 98, 100, 102).
[0063]
By providing the photocoupler 106 as an isolation means on the output side of the comparator 90, a ground fault can be detected by a monitor circuit or the like (not shown) based on the abnormality detection output Sout of the photocoupler 106. In the monitor circuit, the ground fault can be displayed by lighting or can be detected by an alarm. It can also be displayed with characters on the display. Note that the polarity of the comparator 90 can be reversed.
[0064]
Note that the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.
[0065]
【The invention's effect】
As described above, according to the present invention, an abnormality detection circuit that operates with a floating DC power source is provided between a flexible conductive material that covers an insulation-coated conductor for supplying power and the ground, and the abnormality detection is performed. Since the potential fluctuation of the DC power source is detected by the circuit, an abnormality such as a ground fault of the welding cable can be easily detected based on the potential fluctuation of the DC power source.
[0066]
Therefore, according to the present invention, it is not necessary to provide an insulating transformer between the welding power source and the primary side of the welding transformer as in the first technique in the prior art, so that the current efficiency of welding is reduced. Further, it is possible to suppress the cost, and it is not necessary to use an expensive insulating transformer, so that cost can be reduced.
[0067]
Further, unlike the second technique in the prior art, it is not necessary to use two systems of abnormality detection circuits, so that the circuit configuration is simple and the cost can be reduced.
[0068]
That is, according to the present invention, it is possible to obtain a welding cable abnormality detection device that has a simple configuration and that does not require drawing out the core wire of the welding cable.
[Brief description of the drawings]
FIG. 1 is an external view of a resistance welding apparatus to which an embodiment of the present invention is applied.
2 is an electric circuit block diagram of the resistance welding apparatus of FIG. 1 example. FIG.
3 is a circuit diagram showing details of a main part of the resistance welding apparatus of FIG. 1 example; FIG.
FIG. 4 is a circuit diagram for explaining the operation of the abnormality detection circuit when a flaw or the like occurs in the welding cable covering.
FIG. 5 is a circuit diagram for explaining the operation of the abnormality detection circuit when a flaw or the like occurs in the core wire of the welding cable.
FIG. 6 is a circuit diagram for explaining the operation of the abnormality detection circuit when a flaw or the like occurs in the core wire of the welding cable.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Resistance welding apparatus 11 ... Welding robot
22 ... Welding transformer 22a ... Primary coil
22b ... secondary coil 26 ... welding gun (gun arm)
28 ... Welding tip 30 ... Welding cable
32 ... Welding power supply 40 ... Welding controller
41 ... External AC power source 42 ... Converter circuit
42a, 42b ... Positive and negative DC power supply 44 ... Inverter circuit
48 ... Abnormality detection circuit 51, 61 ... Core wire
52, 62 ... Coating 53, 63, 80 ... Insulation coated conductor
64: Conductive material 66 ... Insulating material (coating)
82 ... In-phase transformer 90 ... Comparator
92 ... DC power supply
106: Photocoupler (isolation means)
Sout ... abnormal detection output

Claims (4)

In the abnormality detection device for the welding cable (30) for supplying power to the primary coil of the welding transformer,
The welding cable (30) is flexible to an insulation coated conductive wire for power supply (53), covering a flexible conductive material which covers the insulating coated conductive wire (53) (64), the conductive material (64) An insulating material (66) ,
Between the conductive material (64) and ground, and operates in floating DC power supply (92), and has an abnormality detection circuit (48) for detecting a potential change of the DC power supply (92),
The abnormality detection circuit (48)
A divided potential (Ea) obtained by dividing the voltage (Ed) between the positive terminal (Q) and the negative terminal (P) of the floating DC power source (92) by the voltage dividing means (94, 96) is negative. A comparator (90) supplied to the input terminal and supplied with the ground potential to the positive input terminal;
An anode terminal is connected to the positive terminal (Q) of the floating DC power source (92), a cathode terminal is connected to the flexible conductive material (64), and the first resistor (84) is connected to the flexible conductive material (64). A first diode (85) connected to the other end;
A second diode having an anode terminal connected to the positive input terminal at the ground potential and a cathode terminal connected to a common connection point of the cathode terminal of the first diode (85) and the first resistor (84). (86)
A second resistor (102) having one end connected to the positive input terminal at the ground potential and the other end connected to the negative terminal (P) of the floating DC power source (92). ,
The second resistor (102) has a ground fault when the conductive material (64) has a ground fault with the ground, or the conductive material (64) has a ground fault with the core wire (51) of the insulating film conductor (53). Sometimes the potential on the negative terminal (P) side of the DC power source (92) is floated and the potential on the positive terminal (Q) side is floated due to a voltage drop generated by the current flowing through the second resistor (102). An apparatus for detecting an abnormality of a welding cable, wherein the divided voltage potential (Ea) is varied to reverse the output of the comparator (90) . The abnormality detection device according to claim 1,
When the DC potential fluctuation of the DC power supply (92) is detected by the abnormality detection circuit (48) , the comparator (90) is generated between the conductive material (64) and the ground. An apparatus for detecting an abnormality of a welding cable, characterized by generating an abnormality detection output for detecting a ground fault. The abnormality detection device according to claim 1,
By the abnormality detection circuit (48), when the AC potential variation of the DC power source (92) is detected, the comparator (90), said insulating coating said core wire conductor (53) and (51) An on / off abnormality detection output is generated as an abnormality detection output for detecting a ground fault occurring between the conductive material (64) and the welding cable abnormality detection device. In the abnormality detection apparatus according to any one of claims 1 to 3,
The output of the comparator (90) of the abnormality detection circuit (48), isolation means (106) for insulating the abnormal detection circuit (48) is connected,
The abnormality detection circuit (48) outputs the abnormality detection output via the isolation means (106) when detecting a potential fluctuation of the DC power source (92). apparatus.

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