JPH09182964A - Arc sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect the deviation of an arc from a tangential line by detecting a welding voltage at both weaving ends at the time of a weaving action, calculating an arc position and referring it to an evaluation function. SOLUTION: At the time of weaving action of a torch, the left end voltage and the right end voltage are inputted in an arithmetic unit 7 as a digital signal through an isolation amplifier 5 and an A/D converter 6. The arithmetic unit 7, on the basis of this signal and the signal of the torch position, determines the deviation of the arc from a welding line and supplies the deviation value to a controller 8. The arithmetic unit 7 also performs as that of an arc position as well as a device for setting an evaluation function, determining the deviation of an arc from a tangential line by referring to a preset evaluation function. The evaluation function is desirably provided with a dead zone at need so as to suppress variations in a minute range. This arc sensor can also be used in fillet welding as well as in butt welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc sensor for detecting deviation of an arc from a welding line in an arc welding method.

[0002]

2. Description of the Related Art As one of the arc welding methods, the electrode welding type gas shield arc welding method is known. The hot-melt gas shielded arc welding method generates an arc between the welding wire and the base metal in a state where the air at the welding location is eliminated by the shield gas, and the welding wire and the base metal are melted by the heat generated by this arc. It is what makes me. To generate an arc, a constant voltage welding power source is connected between the electrode tip holding the welding wire and the base metal. In this case, when the distance between the electrode tip and the base material changes, the welding current changes according to the amount of change. That is, as shown in FIG. 4, as the arc length increases from L1 to L2, the welding current decreases from I1 to I2.

In view of this point, the conventional arc sensor has a welding torch 1 (or welding wire) as shown in FIG.
The welding current is detected while weaving (swinging) or rotating between the base materials 2 as indicated by the arrow, and the amount of deviation of the arc from the welding line is detected based on the change in the welding current at that time. Specifically, a change in welding current due to a phenomenon in which an arc is repeatedly generated and a short circuit occurs between the base metal and the welding wire during welding work is used. FIG. 5
FIG. 5A shows the case of butt welding, and FIG. 5B shows the welding operation in the case of fillet welding.

[0004]

However, as shown in FIG. 6 (a), the welding current during the welding operation has a large waveform and a relatively gentle change due to a short circuit between the base material and the welding wire. For example, the welding current does not increase immediately even if there is a short circuit between the base material and the welding wire, but gradually changes, and also decreases when it decreases. For this reason,
At the time of butt welding, there is a drawback that the deviation of the arc from the welding line cannot be accurately detected due to the so-called root gap between the base materials.

Further, since the change in arc length differs depending on the object to be welded, it is difficult to normalize the variation difference in welding current,
Therefore, it is necessary to adjust by various parameters. Furthermore, since the waveform of the welding current varies depending on the welding phenomenon, it is necessary to adjust it.

Further, as can be seen from FIG. 4, the higher the welding current, the smaller the change in current due to the difference in arc length, so that there is a problem that it is difficult to detect the amount of arc deviation itself at high currents.

Therefore, an object of the present invention is to provide an arc sensor which can accurately detect the deviation of the arc from the welding line without depending on the welding conditions.

[0008]

According to the present invention, in an arc sensor for detecting an amount of deviation of an arc from a welding line when performing arc welding with weaving operation of a torch, the weaving operation is performed during the weaving operation. Voltage detection means for detecting the welding voltage at each of both ends, arc position calculation means for calculating the position of the arc based on the both welding voltages, evaluation function setting means for setting an evaluation function, the arc position An arc sensor is obtained which includes a deviation amount calculating means for calculating the deviation amount of the arc from the welding line in light of the evaluation function.

Here, the arc position calculating means includes means for obtaining an integrated difference between the two welding voltages, and means for dividing the integrated difference by an integration time and a set voltage to make the arc position nondimensional. Is preferred.

Further, it is preferable that the evaluation function setting means gives the evaluation function a dead zone irrelevant to the arc position.

[0011]

1 is a schematic explanatory view of an arc sensor according to an embodiment of the present invention. This arc sensor is for detecting the amount of deviation of the arc from the welding line when performing arc welding by means of a welding electrode type gas shielded arc welding machine which performs arc welding with the weaving operation of the torch. The connected voltage detection unit 4 is provided. The welding power source 3 is for applying a constant voltage between the electrode tip and the base material in order to generate an arc. The voltage detection unit 4 detects the welding voltage at the left and right ends of the weaving as the left end voltage and the right end voltage during the weaving operation of the torch. As can be seen from Fig. 6 (a), the welding current is greatly influenced by the short circuit between the base metal and the welding wire, while the welding voltage is seen only from the moment when the short circuit occurs as shown in Fig. 6 (b). Can be said to be stable with respect to the welding phenomenon.

The left end voltage and the right end voltage are input to the arithmetic unit 7 as digital signals through the isolation amplifier 5 and the A / D converter 6. Further, a torch position signal indicating the position of the torch is input to the arithmetic unit 7 from a controller 8 such as an automatic machine or a robot that moves the torch.

The arithmetic unit 7 performs a predetermined arithmetic operation to be described later based on the digital signal indicating the left end voltage and the right end voltage and the torch position signal, calculates the deviation amount of the arc from the welding line, and calculates the deviation amount by the controller. Supply to 8.

Next, the calculation in the calculation device 7 will be described.

First, the integration interval (time) Δt is determined with reference to the torch position signal. The integration interval (time) Δt is defined as the stop time when the weaving operation has both ends stopped as shown in FIG. 2A, and as the weaving operation does not have both ends stopped as shown in FIG. 2B. Is near both ends of the weaving operation.

Next, based on the digital signal, the left end voltage E _l and the right end voltage E _r are integrated in the integration interval (time) Δt to obtain an integrated value, and the difference between these integrated values is calculated. It is divided by the integration interval (time) Δt and the set voltage E ₀ . As a result, the integration interval (time) Δt and the set voltage E
A dimensionless left / right voltage integration difference E that does not depend on ₀ is calculated. The above can be summarized as the following formula 1.

[0017]

[Equation 1] At this time, the arithmetic unit 7 functions as an arc position calculating unit that calculates the position of the arc.

Furthermore, in order to eliminate the influence of noise and the like,
The left-right voltage integration difference E is smoothed by a known moving average method or the like.

The calculation device 7 functions as an evaluation function setting device to calculate the amount of deviation of the arc from the welding line with reference to the evaluation function of FIG. 3 set in advance. At this time, the arithmetic unit 7 functions as a deviation amount calculating means. In addition, it is preferable that dead zones −a to a are provided in the evaluation function as needed to suppress the variation of movement in a minute range.

This arc sensor can be used not only for butt welding but also for fillet welding, and can accurately detect the deviation of the arc from the welding line. Further, since it is dimensionless, it is possible to deal with various welding conditions without changing the parameters of the evaluation function. Further, since the waveform of the welding voltage changes only for the moment when there is a short circuit, the welding voltage is stable with respect to the welding phenomenon, and therefore, there is an advantage that any welding phenomenon can be dealt with.

[0021]

As described above, according to the present invention,
It is possible to provide an arc sensor that can accurately detect the deviation of the arc from the welding line without depending on the welding conditions.

[Brief description of the drawings]

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

FIG. 2 is an explanatory view showing an integration section used in the arc sensor of FIG. 1 in relation to a weaving operation.

FIG. 3 is an explanatory diagram of an evaluation function used in the arc sensor of FIG.

FIG. 4 is a graph showing operating points of an arc in a constant voltage characteristic welding machine.

FIG. 5 is an explanatory view for explaining a general welding mode.

FIG. 6 is a graph showing a relationship between a welding current and a welding voltage with respect to a short circuit between a base material and a welding wire.

[Explanation of symbols]

 1 Torch 2 Base material 3 Welding power source 4 Voltage detector 5 Isolation amplifier 6 A / D converter 7 Arithmetic unit 8 Controller

Claims (3)

[Claims] 1. An arc sensor for detecting an amount of deviation of an arc from a welding line when performing arc welding accompanied by weaving operation of a torch. Detecting means, arc position calculating means for calculating the position of the arc based on the two welding voltages, evaluation function setting means for setting an evaluation function, and arc from the welding line in light of the arc position against the evaluation function. A deviation amount calculating means for calculating a deviation amount of the arc sensor. 2. The arc position calculating means includes means for obtaining an integrated difference between the two welding voltages, and means for dividing the integrated difference by an integration time and a set voltage to make the arc position nondimensional. The arc sensor according to claim 1. 3. The arc sensor according to claim 1, wherein the evaluation function setting means gives the evaluation function a dead zone irrelevant to the arc position.