JP3039196B2 - Arc sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc sensor effective for automatic arc welding of a thin plate.

[0002]

2. Description of the Related Art In recent years, a rotary arc welding method in automatic arc welding not only has a feature such as making the penetration shape uniform and flattening a bead shape in welding, but also has a feature such as a welding current or an arc voltage. It is suitable for arc sensor control that performs welding by always positioning the center axis of the nozzle at the center of the groove of the workpiece by the signal obtained from the change of the nozzle, and it has begun to be widely applied to automatic welding of thick plates. I have.

A specific conventional method for controlling an arc sensor in rotary arc welding is disclosed in Japanese Patent Publication No. 64-4875.
And is being widely used at present. Less than,
The conventional arc sensor control disclosed in Japanese Patent Publication No. 64-4875 will be described with reference to the drawings.

FIG. 4A is a front view showing a welding state of rotary arc welding to which conventional arc sensor control is applied. In the figure, reference numerals 11 and 11 'denote workpieces, and reference numeral 12 denotes a groove. Reference numeral 13 denotes a nozzle vertically inserted into the groove 12. The tip 19 for guiding the tip of the electrode 15 is mounted eccentrically from the central axis 14 of the nozzle 13, so that welding is performed while rotating the nozzle counterclockwise. , Electrode 15 and workpieces 11, 11 ′
4 (b), circular arcs sequentially pass through points p, q, r and s in the horizontal direction within the groove 12 as shown in FIG. 4 (b).

An arc sensor control method applied to the above-described rotary arc welding will be described with reference to FIG. When the central axis 14 of the nozzle 13 passes through the central portion 18 of the groove 12, the welding current changes as shown in FIG. Next, when the central axis 14 of the nozzle 13 is displaced to the left or right from the central portion 18 of the groove 12, the welding current changes as shown in FIG. FIG. 5 (b)
5 shows a case where the central axis 14 of the nozzle 13 is displaced to the left from the central portion 18 of the groove 12, and when it is displaced to the right, the time axis p of FIG. r and q are read as s, r is read as p and s is read as q. This welding current is applied to the left and right quarter cycles of the rotating arc (FIG. 5 (a),
By integrating each time between pq and rs in FIG. 5B and comparing the left and right integrated values, it is possible to detect the position of the central axis 14 of the nozzle 13 in the groove 12. , Whereby it can be controlled to always be located at the central portion 18.

[0006]

However, in the above-described conventional arc sensor, the thickness of the workpiece is close to or less than the minimum value that can be used as an arc sensor having a rotating diameter. When applied to a joint or the like, the following problems occur. That is, in such a joint, when the central axis of the nozzle is located at, for example, point E in FIG. 1, there is a problem that the sensitivity of the arc sensor is reduced in the comparison of the integral values of the left and right quarter periods. .

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an arc sensor applicable to a thin lap joint or the like.

[0008]

In order to achieve this object, an arc sensor according to the present invention uses a signal obtained from a welding current or an arc voltage for each cycle of an arc rotation to obtain a relative position between a nozzle and a workpiece. In rotating arc welding where welding is performed while detecting an arc, when an inflection point is detected in a signal obtained from a welding current or an arc voltage, the width of the integration area is controlled so that the inversion area of the signal does not include the inflection point. Things.

[0009]

According to this method, when the present invention is applied to a lap joint of a thin plate whose plate thickness is close to or less than a minimum value usable as an arc sensor of a rotating diameter, the central axis of the nozzle is caused by a welding current or a welding current. When the signal obtained from the arc voltage deviates to a point that includes an abnormal value that lowers the sensor sensitivity, the integration area is narrowed, so that a high-performance arc sensor can be realized.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numerals 1 and 1 ′ denote a thin plate to be welded, 1 an upper plate, and 1 ′ a lower plate to form a horizontal lap joint.
Reference numeral 2 denotes a welding line, which indicates the traveling direction of a torch (not shown) by an arrow. Reference numeral 3 denotes a nozzle attached to the tip of the torch, which has a tip (not shown) mounted eccentrically from the center axis 4 and guiding the electrode 5. A rotating arc is generated between the workpiece 5 and the workpieces 1 and 1 '. Reference numerals 6 and 6 'denote projection lines of the circular orbit drawn by the rotating arc when the central axis 4 of the nozzle 3 passes through the point C or the point E onto the workpieces 1 and 1'.

The operation of the above-described rotary arc welding method will be described with reference to FIGS. In this embodiment, the torch position is such that the nozzle 3 is welding to the workpiece 1 at a target angle of 45 degrees. In addition, the rotation diameter of the arc is set to φ1.5 mm as a value that allows a change in welding current to be used as an arc sensor for a workpiece having a plate thickness of t1 mm.

The center axis 4 of the nozzle 3 is A, B, C,
The welding current at each point of D and E is shown in FIG.
(A), (b), (c), (d) and (e). Point C is on the weld line 2 and indicates that the torch is in a normal position. When the center axis 4 of the nozzle 3 is in the range from the point A to the point D, welding proceeds normally following the welding line 2 by the conventional arc sensor control. Nozzle 3
When the central axis 4 is at the point E, the projected line 6 'of the circular orbit drawn by the rotating arc on the workpieces 1 and 1' is as shown in FIG. ), The rotating arc shows a peculiar curvature at points m and n of the circular orbit. This curvature appears in a phase in which the welding current increases, contrary to the normal curvature seen when the center axis 4 of the nozzle 3 passes through the point B or the point D near the point C in the normal position. FIG.
The dashed line in (e) shows the change in welding current when the thickness of the upper plate 1 is assumed to be sufficiently thicker than the rotating diameter of the arc. The sensitivity as a sensor is reduced compared to the change in the welding current indicated by the dotted line. If the center axis 4 of the nozzle 3 is shifted further upward or to the left from the point E, the sensitivity is further reduced. Therefore, when the reverse bending point seen at points m and n is detected, the integration area is narrowed so that the integration area does not include the bending point.

As described above, according to the present embodiment, in the rotary arc welding in which welding is performed while detecting the relative position between the nozzle and the workpiece with a signal obtained from the welding current in each cycle of the arc rotation, By detecting the inflection point of the signal obtained from the welding current so as not to include the inflection point in the integration region of the signal, whether the sheet thickness is close to the minimum value that can be used as an arc sensor of the rotating diameter. ,
When applied to thin lap joints that are less than that, when the center axis of the nozzle deviates to the point that the signal obtained from the welding current contains an abnormal value that reduces the sensor sensitivity Since the integration area is narrowed, a high-performance arc sensor can be realized.

As described above, the arc sensor according to the present embodiment can obtain an excellent effect in removing the sensitivity decrease due to the peculiar reverse curvature which appears in the change of the welding current.

Although the welding current is used as the arc sensor signal source in this embodiment, an arc voltage may be used as the arc sensor signal source. Further, it is needless to say that the work to be welded is not limited to a thin horizontal lap joint, but may be applied to a square joint as shown in FIG.

[0017]

As described above, the present invention relates to rotary arc welding in which welding is performed while detecting the relative position between the nozzle and the workpiece with a signal obtained from the welding current or arc voltage for each cycle of arc rotation. When the reverse bending point of the signal obtained from the welding current or the arc voltage is detected, the reverse bending point is not included in the integration region of the signal, so that the plate thickness can be used as an arc sensor having a rotating diameter. When applied to welding of thin plates that are close to or less than the minimum value, the central axis of the nozzle may contain abnormal values that reduce the sensor sensitivity in the signal obtained from the welding current or arc voltage. It realizes an excellent arc sensor with high sensor sensitivity even when it deviates to a certain point.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a horizontal lap joint welding method according to an embodiment of the present invention.

FIGS. 2A to 2E are diagrams showing changes in welding current at points A to E, respectively, in the horizontal lap joint welding method according to one embodiment of the present invention.

FIG. 3 is a joint shape diagram for explaining another application in one embodiment of the present invention.

FIG. 4 (a) is a front view showing a welding state of conventional rotary arc welding; FIG. 4 (b) is a plan view showing a circular arc trajectory of conventional rotary arc welding;

FIG. 5 (a) is a diagram showing a change in welding current when the center axis of the nozzle is located at the center of a groove in conventional rotary arc welding. The figure which shows the change of the welding current when the central axis is deviated from the center of the groove

[Explanation of symbols]

 1,1 'Workpiece 3 Nozzle m, n Reverse curve point

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 9/127

Claims (1)

(57) [Claims] 1. In rotary arc welding in which welding is performed while detecting the relative position between a nozzle and an object to be welded by a signal obtained from a welding current or an arc voltage for each cycle of arc rotation, the welding current or the arc voltage is used. An arc sensor for controlling an integration region width such that when an inverted curve point is detected in an obtained signal, the integrated region of the signal does not include the inverted curve point.