JPH04220171A - Travel controller for arc welding torch - Google Patents

Abstract

PURPOSE:To prevent the occurrence of weld defects at the time of starting to weld, to detect abnormality in a welding circuit and to stop facilities. CONSTITUTION:A detector 20 to detect electric current and voltage is provided on power cables 7 and 8 to connect a torch 2, materials 2 to be welded and a welding power source 9, respectively. The detected current and voltage are compared and checked with set values by an arc current checking device 21 and an arc voltage checking device 25 and based on a checked result, an arc generated state is judged by an arc generation determining device 29 to control travel of the torch 2 via a torch travel control circuit 5 based on a judged result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding torch travel control device that is installed in a consumable electrode type arc welding apparatus and controls the travel operation of the torch.

0002

2. Description of the Related Art FIG. 5 shows a schematic configuration of a conventional consumable electrode type automatic arc welding device. In the figure, a torch 3 through which a welding wire 1 is inserted and fed toward a workpiece 2 is supported by a traveling device 4, which is a robot, and travels. Traveling device 4
is controlled by a torch travel control circuit 5, and the welding wire 1 is fed into the torch 3 by a wire feeding motor 6. Further, the welding wire 1 and the workpiece 2 are connected to a welding power source 9 via power cables 7 and 8, respectively, and the welding power source 9 includes a welding control circuit 10 and a power transformer 11.
and a current check relay 12 are provided.

FIG. 6 shows the basic operation of a conventional automatic arc welding apparatus constructed as described above. In the figure, A indicates the operation of the torch running control circuit 5, B indicates the current confirmation relay 12, C indicates the welding power source 9, and D indicates the operation of the arc. In step 101, when the traveling device 4 is driven by a signal issued from the torch traveling control circuit 5, the torch 3 moves to the welding start position and stops at that position in step 102. Next, in step 103, the torch traveling control circuit 5 outputs a welding start signal 13 to the welding control circuit 10 of the welding power source 9.

In step 104, the welding control circuit 10 receives the welding start signal 13 and turns the power transformer 11 on.
Then, power is output to the welding circuit formed by the welding wire 1 and the workpiece 2 via the power cables 7 and 8, and a signal is further output to the wire feeding motor 6 to rotate it. As a result, in step 105, an arc is generated between the welding wire 1 and the workpiece 2. Welding wire 1 is melted by the heat of the arc and diffused between welding wire 1 and object 2 to be welded. At this time, the welding wire 1 is fed toward the workpiece 2 by the wire feeding motor 6, and the distance between the welding wire 1 and the workpiece 2 is kept constant. Further, in step 106, welding conditions are controlled by the welding control circuit 10, and in step 107, the arc is stabilized.

On the other hand, the current checking relay 12 detects the current flowing through the power cables 7 and 8 due to the occurrence of an arc, and is turned ON in step 108. Current confirmation relay 12
When turned on, the arc generation confirmation signal 14 is input to the torch traveling control circuit 5, and the torch 3 is caused to travel in step 109.

When welding is completed, the torch 3 stops at that position in step 110, and the welding start signal 13 output from the torch traveling control circuit 5 is turned off in step 111. As a result, in step 112, the output of the welding power source 9 is stopped, and the wire feeding motor 6 is also stopped. Then, in step 113, the welding wire 1 is ignited, the arc is extinguished in step 114, and the current checking relay 12 is turned off in step 115. Next, in step 116, the torch 3 is moved to the next welding position and the above operation is repeated.

[0007] As this type of arc welding equipment,
As described in Japanese Patent Application Laid-Open No. 59-153578,
An arc detector detects the occurrence of an arc caused by the welding current, and based on the detected value, it selects the start current according to the welding conditions and sets the time for the start current to flow, ensuring a reliable arc start. It is known that this was done.

[0008]

The current checking relay 12 is turned ON when a current flows through the welding circuit formed by the welding wire 1 and the workpiece 2. However, time is required after current starts flowing through this circuit until an arc is generated between the welding wire 1 and the workpiece 2 and a desired welding current is obtained. For this reason, after receiving the ON signal from the current check relay 12, the torch running control circuit 5 controls the torch 3 to start running after a delay time of about 0.2 seconds has elapsed.

Furthermore, during welding, the arc may be momentarily interrupted and the current may become zero. In this case, in order to prevent the equipment from stopping, the relay should be turned OFF on the current checking relay circuit side.
A delay time of about 0.2 seconds is normally set until F is reached.

In the above-described conventional device, the torch running control circuit 5 operates approximately 0.2 times after the current check relay 12 is turned on.
The torch will start running after a second. Also, the current confirmation relay 12 turns OFF approximately 0.2 seconds after the current becomes zero.
The equipment then stops. For this reason, there was a risk that the torch would start traveling before the arc actually occurred, resulting in a welding gap.

In order to solve this problem, it is possible to extend the torch travel start delay time or shorten the OFF delay time, but in the former case, when the arc starts well, the torch 3 It will be stopped for a while,
There is a possibility that heat will be concentrated on the workpiece 2 to be welded, resulting in defects such as holes. In the latter case, even if the arc is momentarily cut off and restored immediately, the current checking relay 12 will be turned OFF and the equipment will be stopped. As a result, there was a problem in that the operating rate of the equipment decreased and the welding quality was also adversely affected.

On the other hand, a problem in arc welding is the shunting of welding current that occurs within the welding circuit, particularly within the welding torch. Originally, the power cable 7 on the torch 3 side must be supplied with power to the welding wire 1 via a contact tip 15 attached to the tip of the torch 3, as shown in FIG. However, due to a defect in the torch 3, a welding circuit may be formed at a point other than the contact tip 15 through spatter or torch components, and a shunt may occur there.

Moreover, the conventional current checking relay 12 described above
This detects whether a current is flowing or not, and cannot detect whether the flowing current is due to a shunt.

When a shunt occurs in the torch 3 in this way, the current flowing through the welding wire 1 decreases, as shown in FIG. The arc disappears. If the torch 3 continues to run in this state, the red-hot wire that is not melted will continue to be fed out by the wire feeding motor 6, leaving only the welding wire 1 behind where welding is required, resulting in welding defects. .

In addition, the automatic arc welding machine in which the torch 3 is moved by a robot has a wide range of movement of the torch 3, as shown in FIG.
A power cable 7 connected to the torch 3 as shown in
8, a gas hose (not shown), and a wire conduit tube (not shown) are usually pulled or rubbed and subjected to excessive force during work. For this reason, power cable 7
. As a result, the internal resistance 16 of the welding circuit gradually increases, the welding conditions change, and in the worst case, the arc disappears. When this phenomenon occurs, the current value becomes low but does not become zero, and the current check relay 12 does not turn off but continues to turn on.

[0016] The proposal described in the above publication is to switch to the set welding current value after generating an arc, and since the current continues to flow even if a shunt current occurs during welding, the normal current value As a result, the heat generation phenomenon is reduced. Furthermore, it is not possible to detect changes in welding conditions due to disconnection of the power cable.

The present invention has been made in view of the above points, and provides a travel control device for an arc welding torch that can prevent welding defects from occurring at the start of welding and can detect abnormalities in the welding circuit. The purpose is to

[0018]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an arc between the workpiece and the welding wire while feeding the welding wire through a torch toward the workpiece. A travel control device for an arc welding torch that is installed in a consumable electrode type arc welding device that generates electricity and welds the workpiece, and that controls the travel operation of the torch, wherein the torch, the workpiece, and the welding power source are connected to each other. A detector for detecting arc current and arc voltage is provided in the power cables connected to each, and an arc current tester and an arc voltage tester are used to verify the current and voltage detected by the detector by comparing them with respective set values. In addition to connecting the
An arc occurrence determiner for determining the arc occurrence state based on the test results is connected to both of the testers, and the arc occurrence determiner is further connected to the traveling control circuit of the torch.

[0019]

[Operation] According to the above structure, the power current and voltage flowing through the welding wire are detected by the detector, and the detected values are verified by comparing them with set values by the arc current tester and the arc voltage tester, respectively. Then, based on these test values, the arc occurrence state is determined by the arc occurrence determination device, and the running operation of the torch is controlled to prevent the occurrence of welding defects.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an automatic arc welding machine equipped with a torch travel control device according to an embodiment of the present invention. In the figure, parts corresponding to those in the conventional example shown in FIG. 5 are denoted by the same reference numerals, and the explanation thereof will be omitted as appropriate. The power cables 7 and 8 are provided with a current and voltage detector 20 for detecting the current and voltage of the welding circuit, and the detector 20 is connected to an arc current tester 21 and an arc voltage tester 22. . These testers 21
, 22 have the same configuration, the arc voltage tester 22
Illustrated only. The certifiers 21 and 22 include a smoothing circuit 23, an upper limit comparator 24, a lower limit comparator 25, an AND circuit 26, and a detection zone setter 27.

The upper limit comparator 24 and the lower limit comparator 25 are each connected to a detection zone setter 27, and the detection zone setter 27 provided in both certifiers 21 and 22 is connected to a welding condition setter 28. There is. Further, the welding condition setting device 28 is connected to a welding control circuit 10 within the welding power source 9. On the other hand, an arc occurrence determiner 29 is connected to the AND circuit 26 provided in both the certifiers 21 and 22, and the arc occurrence determiner 29 is connected to the torch travel control circuit 5.

Next, the operation of this embodiment will be explained. The current and voltage detector 20 detects the current and voltage at the contact portion between the welding wire 1 and the workpiece 3 using analog values. The detected values are input to an arc current tester 21 and an arc voltage tester 22, respectively. The voltage value 30 input from the current/voltage detector 20 to the arc voltage tester 21 is input to the welding power source 9.
Many high-frequency waveforms are included due to pulses and welding phenomena. Therefore, the waveform is smoothed by the smoothing circuit 23.

On the other hand, in accordance with the welding condition voltage value 31 input from the welding condition setting device 28, the detection zone setting device 27 outputs an upper limit value 32 and a lower limit value 33 of the arc generation determination voltage. If the welding condition range is narrow, the upper limit value 32 and lower limit value 33 may be fixed regardless of the input of the welding condition voltage value 31.

The voltage value output from the smoothing circuit 23 is sent to an upper limit comparator 24 and a lower limit comparator 25, and in the upper limit comparator 24, the output from the smoothing circuit 22 is sent to the detection zone setter 2.
If the output from the smoothing circuit 22 is higher than the lower limit value 33 input from the detection zone setter 27, the lower limit comparator 25 generates an ON signal. Upper limit comparator 24 and lower limit comparator 2
The ON signals emitted from each of the circuits 5 and 5 are input to the AND circuit 26, and when both inputs are ON, the ON signal is output to the arc occurrence determination device 29.

Similarly, an ON signal is output from the arc current tester 21 to the arc occurrence determiner 29, and the arc occurrence determiner 29 connects the arc current tester 21 and the arc voltage tester 22.
When the signals from both are ON, an ON signal is output to the torch travel control circuit 5 to cause the torch 2 to travel.

FIG. 2 is a timing chart showing the current and voltage waveforms and the output signals of the arc current tester 21, arc voltage tester 22, and arc occurrence determiner 29. In the figure, when the current value 34 and the voltage value 30 are between the upper limit value and the lower limit value, respectively, the outputs of the testers 21 and 22 are turned ON.

FIG. 3 is a time chart showing the state when the flow split occurs in FIG. 2. As shown in the figure, when a shunt occurs at the point shown in (a) from a normal welding state as shown on the left side of the figure, the resistance of the entire secondary circuit decreases, so the current value 34 increases slightly, but the arc current test It is between the upper limit value and the lower limit value at which the device 21 issues an ON signal. However, the voltage value 3
0 is almost zero because the welding wire 1 and the workpiece 2 are in contact with each other, and is smaller than the lower limit value 33, so that no ON signal is generated. Therefore, the arc voltage tester 22 is turned off.
The output of the arc occurrence determination device 29 is also turned off, and the torch 3
will stop running.

Further, when the power cables 7 and 8 are disconnected, the current value 34 decreases and becomes smaller than the lower limit value of the arc current tester 21 at the time of disconnection (b) shown in FIG. Therefore, the output signal of the arc current tester 21 is turned OFF, and the output signal of the arc occurrence determiner 29 is also turned OFF, so that the equipment stops.

According to this embodiment, the current value 34 and voltage value 30 of the arc welding power flowing through the welding wire 1 are detected by the detector 20, and if the detected values are within a predetermined range, the arc occurrence determination device is activated. 29, and the torch travel control circuit 5 drives the welding power source and the torch travel device 4 to perform the prescribed arc welding. This prevents welding failures at the start of welding and prevents welding failures during welding. Equipment can be stopped by detecting welding circuit abnormalities such as shunts and cable breaks.

[0030]

[Effects of the Invention] As explained above, according to the present invention,
Welding is performed only when both the current and voltage values of the arc welding power flowing through the welding wire are within a predetermined range, which prevents welding failures at the start of welding and prevents welding from occurring during welding. It is possible to detect abnormalities in the welding circuit, such as cable breakage or cable breakage, and stop the equipment, ensuring welding quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a time chart showing the same operation.

FIG. 3 is a time chart showing the operation when a shunt occurs.

FIG. 4 is a time chart showing the operation when the power cable is disconnected.

FIG. 5 is a block diagram showing the configuration of a conventional automatic arc welding device.

6 is an explanatory diagram showing the basic operation of the automatic arc welding apparatus shown in FIG. 5. FIG.

FIG. 7 is an explanatory diagram showing the state of branched flow in the arc welding device.

FIG. 8 is an explanatory diagram showing weld defects caused by shunting.

FIG. 9 is an explanatory diagram showing a state in which the power cable is disconnected.

[Explanation of symbols]

1 Welding wire 2 Object to be welded 3 Torch 4 Traveling device 5 Travel control circuit 7, 8 Power cable 9 Welding power source 20 Current voltage detector 21 Arc current tester 22 Arc voltage tester 29 Arc occurrence determiner

Claims (1)

[Claims] 1. Consumable electrode type arc welding, in which the welding wire is fed toward the workpiece through a torch, and an arc is generated between the workpiece and the welding wire to weld the workpiece. A travel control device for an arc welding torch that is installed in a device and controls the travel operation of the torch, which detects arc current and arc voltage in power cables that connect the torch, the workpiece, and a welding power source, respectively. A detector is provided, and an arc current tester and an arc voltage tester are connected to the detector to compare and verify the detected current and voltage with set values, respectively, and a A travel control device for an arc welding torch, characterized in that an arc occurrence determiner for determining an arc occurrence state is connected, and the arc occurrence determiner is further connected to a travel control circuit for the torch.