JPH11267841A - Arc sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out copying of a welding bogie and the like against a welding center line by calculating a difference of arc welding current value from detection of arc welding current values at the times the welding torch weavings are stopped at both ends, and calculating position slippage of both weaving ends from a welding center line based on an evaluation function being set by an evaluation function setting means. SOLUTION: A current detection part 4 detects a welding current at both of the left, right weaving ends of the welding torch as a left end current, a right end current and inputs then into a computing device 7 via an isolation amplifier 5 and a A/D transformer 6. A controller 8 of a welding bogie and the like, into which computing operation results are inputted, sends a torch positioning signal, which indicates a welding torch position, to the computing device 7. The computing device 7 calculates a current difference when both of weaving ends of the welding torch are stopped, and furthermore acts as an evaluation function setting device for calculation of the arc position slippage volume from the welding center line. In the evaluation function, a dead zone is set when necessary, so as to restrain an irregularity of the arc position slippage from the welding center line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc sensor, and more particularly to an arc sensor for detecting a welding center line in an arc welding method.

[0002]

2. Description of the Related Art As one of the arc welding methods, a gas-shielded gas shielded arc welding method is known. In this electrode-type gas shielded arc welding method, an arc is generated between the welding torch (welding wire) and the base metal while the air at the welding point is excluded by the shielding gas, and the heat generated by the arc causes the welding torch and The base material is being melted.

Here, when performing arc welding on a welding point set along the longitudinal direction, such as fillet welding or butt welding, a welding torch is provided on a welding cart or a robot. At the same time, a configuration is adopted in which the motor provided on the welding trolley or the like is driven to rotate the drive wheels, so that the welding trolley or the like travels along the welding center line of the above-mentioned welding point and performs automatic welding with a welding torch. .

In the prior art, as a method of performing automatic welding along the welding center line as described above, a guide is applied to a base material to maintain a constant position with respect to a welding point such as a welding cart, or a method other than a welding torch is used. There is a method in which the apparatus is mounted on the tip of a welding bogie or the like, and the welding bogie or the like travels along the detected welding center line while detecting the welding center line before welding.

As a method of detecting a welding center line from an arc phenomenon itself during arc welding, there are a method using a welding current and a method using a welding voltage. Here, in order to generate an arc as described above, a constant-voltage welding power source is generally connected between the electrode tip holding the welding torch and the base material.

In the method using the welding current, the welding current is detected while weaving (oscillating) or rotating between the welding torch and the base material, and the welding current is detected based on a change in the welding current at that time. Is detected. Specifically, a change in welding current caused by a phenomenon in which an arc is repeatedly generated and short-circuited between a base material and a welding torch during a welding operation occurs. Further, in the method using the welding voltage, the amount of displacement of the arc is detected based on the change of the welding voltage detected in the same manner.

[0007]

However, in the method of applying a guide to the base material or using a device other than the welding torch as described above, the time required for welding is increased, and a welding cart or the like and its accessories are provided. There is a problem that a device for performing the operation becomes large.

On the other hand, in short-circuit welding using a constant-voltage welding power source as described above, the welding current greatly changes according to a change in the length of the welding torch (wire length) due to the characteristics of the power source. On the other hand, the change in the welding voltage is small, but the rate of change with respect to the length of the welding torch increases in the high current region. For this reason, it is difficult to accurately detect the welding center line using the above-described method using the welding current in the high current region, while it is difficult to accurately detect the welding center line using the welding voltage in the low current region and the medium current region. There is a problem that it is difficult to detect the center line.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to accurately detect an arc deviation from a welding center line without depending on welding conditions, and to easily follow a welding carriage or the like to a welding center line. An object of the present invention is to provide an arc sensor.

[0010]

According to the present invention, there is provided an arc sensor for detecting a shift amount of an arc from a welding center line when performing arc welding by the welding torch with a weaving operation of the welding torch. Current value detecting means for measuring the current value of the arc welding when both ends of the weaving of the welding torch are stopped; current value difference calculating means for calculating the difference between the measured current values of the both ends of the weaving; Evaluation function setting means for setting an evaluation function; and a displacement calculating means for determining a displacement amount of the weaving both ends from the welding center line based on the difference between the current values based on the evaluation function. Is obtained.

[0011] Preferably, the current value difference calculating means is configured to calculate a difference between the current values at both ends of the weaving based on a current value obtained by averaging a plurality of current differences at the time of stopping at both ends of the weaving measured in the plurality of weaving operations. Is calculated.

Preferably, the evaluation function setting means causes the evaluation function to have a dead zone irrelevant to the current difference.

[0013]

Embodiments of the present invention will be described below. FIG. 1 is a schematic explanatory view of an arc sensor according to an embodiment of the present invention, and FIG. 2 is an explanatory view of fillet welding by a welding torch 1.

This arc sensor detects a shift amount of an arc from a welding center line when performing an arc welding by a welding type gas shielded arc welding machine which performs an arc welding with a weaving operation of the welding torch 1. is there. And, it comprises a current detection unit 4, an isolation amplifier 5, an A / D converter 6, an arithmetic unit 7 and the like connected to the welding power source 3.

The welding power source 3 is for applying a constant voltage between the electrode tip of the welding torch 1 and the base material to be welded in order to generate an arc. The current detection unit 4
During the weaving operation of the welding torch 1, the welding current is detected as the left end current and the right end current at the left and right ends of the weaving. The detected left end current and right end current are
The signal is input to the arithmetic unit 7 as a digital signal through the isolation amplifier 5 and the A / D converter 6, and arithmetic processing described later is performed. The result of the arithmetic processing is input to a controller 8 such as a welding cart or a robot that moves the welding torch 1. The controller 8 sends a torch position signal indicating the position of the contact torch 1 to the arithmetic unit 7 using the result of the arithmetic processing described above.

Next, the arithmetic processing by the arithmetic unit 7 will be described. The arithmetic unit 7 calculates a current difference when both ends of the weaving of the welding torch 1 are stopped based on the digital signal indicating the left end current and the right end current and the torch position signal. Further, by operating as an evaluation function setting device, the arithmetic unit 7 calculates the positional shift amount of the arc from the welding center line with reference to the evaluation function set in advance in FIG. At this time, the arithmetic unit 7 functions as a displacement calculating means. The evaluation function includes a dead zone -a as necessary.
Ａa is provided, and thereby, the variation of the detection result in the deviation of the arc in a minute range from the welding center line can be suppressed.

Here, in the ordinary arc welding, when the wire length between the base material and the electrode tip changes, there is a characteristic that the welding current value changes. In the present invention, by utilizing this characteristic, the difference in the wire length at both ends is detected by comparing the current difference between both ends during weaving. Then, the deviation from the center line can be detected from the difference in the wire length, and the welding line can be corrected.

For example, as shown in FIG. 3A, when the welding torch 1 weaves symmetrically with respect to the welding center line C of the base material 2, the wire lengths 11 and 11 'at both ends.
Are equal. However, when the centers of both ends of the weaving are displaced from the welding center line C as shown in FIG. 3B, a difference δ occurs between the wire lengths 11 and 11 ′ at both ends of the weaving. Then, the difference in the wire length is detected as a current difference.

Furthermore, since the current difference between both ends of the weaving and the deviation from the welding center line C are almost linear, the deviation can be detected from the current difference between both ends of the weaving. Then, the correction may be performed using only this deviation amount as the correction amount. Then, the relationship between the current difference between both ends of the weaving and the correction amount of the welding line can be expressed as an evaluation function as shown in FIG. Here, by appropriately adjusting the inclination of the evaluation function in FIG. 3, the degree of following the welding center line can be appropriately changed.

In this evaluation function, a dead zone is provided for suppressing fluctuations in a minute range, and a maximum correction amount is provided for avoiding a sudden change in bead shape. Further, if this evaluation function is expressed as an arithmetic expression, it is as shown in the following Expression 1.

[0021]

When −a <I <a, δ = 0, when a ≦ I ≦ b / s, δ = S · Ib / s ≦ I ≦ −a, δ = S · I> b / S, δ = b I <−b / s, δ = −b Next, the operation of the arc sensor according to the above-described embodiment will be described. First, with reference to FIG. 2, welding torch 1 moves in a welding direction D along a welding location of base material 2 as indicated by trajectory 10. At this time, the average current value during the weaving stop time T at the left and right ends of the weaving is measured by the arithmetic unit 7, and the current difference between both ends for one weaving is calculated from the difference between the average currents at the left and right ends of the weaving. Further, in order to reduce the influence of the variation in the current value, the average current difference for a plurality of times of weaving, for example, eight times, is averaged.

Next, in the arithmetic unit 7, the correction amount of the welding line is obtained from the evaluation function set in advance and the calculated current difference between both ends of the weaving. Based on this correction amount, the controller 8 appropriately adjusts the range of the weaving of the welding torch 1 of the electrode-type gas shielded arc welding machine.
Therefore, the welding torch 1 can be accurately weaved along the welding center line.

[0023]

As described above, according to the present invention,
It is possible to provide an arc sensor that can accurately detect an arc deviation from a welding center line without depending on welding conditions, and can easily follow a welding cart or the like to the welding center line.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an arc sensor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of the arc sensor of FIG.

FIG. 3 shows the difference in wire length at both ends of weaving;
(A) is an explanatory diagram when there is no displacement from the welding center line, and (b) is an explanatory diagram when there is a displacement from the welding center line.

FIG. 4 is an explanatory diagram of an evaluation function used in the arc sensor of FIG. 1;

[Description of Signs] 1 Welding torch 2 Base material 3 Welding power supply 4 Current detector 5 Isolation amplifier 6 A / D converter 7 Arithmetic unit 8 Controller 11 Wire length

Claims (3)

[Claims] An arc sensor for detecting an amount of deviation of an arc from a welding center line when performing arc welding by the welding torch with a weaving operation of the welding torch. Current value detecting means for measuring the current value of the arc welding, current value difference calculating means for calculating the difference between the measured current values at both ends of the weaving, and evaluation function setting for setting a predetermined evaluation function An arc sensor, comprising: means for calculating a position shift amount between both ends of the weaving from the welding center line based on a difference between the current values based on the evaluation function. 2. The current value difference calculation means calculates a difference between the current values at both ends of the weaving based on a current value obtained by averaging a plurality of current differences at the time of stopping at both ends of the weaving measured in the plurality of weaving operations. The arc sensor according to claim 1, wherein the calculation is performed. 3. The arc sensor according to claim 1, wherein said evaluation function setting means has a dead zone irrelevant to said current difference in said evaluation function.