JPH084942B2 - Current control method and device in seam welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to seam welding, and in particular, to the number of stacked plates, such as welding of a metal roof plate or wall plate joint in a building structure. The present invention relates to a current control method and a current control apparatus suitable for continuous welding even when the number changes in one welding line.

[Conventional technology]

In recent years, to prevent rain leaks in building structures, metal has been adopted as the material for the roof and wall boards, and a thin plate of a size that conforms to the standards is welded at the construction site to form a single roof or wall board. There is a lot to do.

FIG. 3 shows an example of a roof for carrying out the welding work described above. That is, the end portion of the strip-shaped plate 1 is bent to provide the flange 2, and description will be given along a rafter (not shown). Then, for example, a traveling welding head having a rotatable roller electrode disclosed in Japanese Patent Publication No. 60-59074 is energized, and adjacent flanges 2 are seam-welded as shown by a dotted line, and substantially seamless. One roof plate 3 was formed. At this time, the impedance between the roller electrodes constantly changes due to changes in the internal resistance of the plates due to changes in the number of thin plates, changes in the contact resistance between the stacked plates, and the like. Therefore, in order to make the quality of the welded part uniform, the power source is controlled by a constant current device and the peak value Iw of the welding current (hereinafter, welding current value
Call it Iw. ) Is kept constant.

In addition, the ridge board 4 arranged in a direction orthogonal to the flange 2
Alternatively, when seam welding the eaves plate (not shown) and the roof plate 3, the end of the already welded flange 2 is tilted,
A flange 5a corresponding to the flange 5 of the ridge board 4 is formed, and both are seam welded as shown by a wavy line 6.

In the welding line indicated by the wavy line 6, as shown in FIG. 4 which is a sectional view taken along the line I-I of FIG.
Called stacking. ) And a portion where four sheets are stacked (hereinafter, simply referred to as four sheets). As described above, when the constant current device is used, even when two-ply and four-ply are mixed in one welding line, that is, even when the impedance change between the roller electrodes is large, Except for the position where the number of plates changes, a slight current change always exists as described above, but the welding current value Iw can be made almost constant.

[Problems to be Solved by the Invention]

However, when the welding speed is kept constant within one welding line, the peak value of the current suitable for welding two sheets (hereinafter referred to as the current value) and the current value suitable for welding four sheets Is different from.

In other words, a current value suitable for welding two-ply stacks cannot weld a four-ply stack, and a current value suitable for welding four-ply stacks results in an excessive current in the two-ply stack part. There is a hole in.

For this reason, it was necessary to perform seam welding indicated by the wavy line 6 at a current value suitable for welding two-ply stacks, and then repair-weld four-ply stacks not welded by a spot welding machine.

The object of the present invention is to solve the above-mentioned problems, and even when the number of stacked plates changes within one welding line, it is possible to continuously weld, and seam welding capable of improving welding workability. The present invention provides a welding current control method and apparatus.

[Means for solving the problem]

Means for solving the above problems will be described with reference to FIG. 1 showing an embodiment of the present invention.

A condition setting device 7 can set a plurality of current values. 8n is an upper limit setter, and 9n is a lower limit setter, which can set an upper limit and a lower limit which are allowable for each of the current values set in the condition setting device 7. 10 is a control device. 11 _nH and 11 _nL are comparators. 12 is a toroidal coil for measuring the actual welding current value I _w flowing through the roller electrode.

[Action]

The comparator 11 _nH compares the upper limit current value and the welding current value I _w with the comparator.
For 11 _nL, the upper limit current value and the welding current value I _W are compared. When the welding current value I _W exceeds the upper limit current value, the comparator 11 _nH closes, and when the welding current value I _w falls below the lower limit current value, the comparator 11 _nL closes.

The control device 10 switches to the next larger current value set in the condition setting device 7 when the comparator 11 _nL is closed, when the comparator 11 _nL is closed, and when the comparator 11 _nH is closed, the control device 10 sets the condition. Switch to the next smaller current value set in the device 7.

That is, the control device 10 switches the current value used for welding according to the change in the number of stacked plates. Therefore, even if the number of stacked plates changes within one welding line, continuous welding can be performed.

〔Example〕

FIG. 1 shows two continuous welding lines according to the present invention.
It is a connection system diagram of the welding current control apparatus for welding the roof plate in which 1 sheet stack, 4 sheet stack, and 6 sheet stack are mixed.

7 is a condition setting device, which can preset a current value I _n (where n = 2, 4, 6) suitable for stacking two sheets, four sheets, and six sheets. 8n upper limit setting device, 9n the lower limit setting unit can set the upper and lower limits acceptable for each of the current value I _n to be set in the condition setting unit 7. 10 is a control device, the signal from the comparator 11 _nH, 11 _nL, switches the current value I _n to another current value I _n. 12 is a toroidal coil for measuring the actual welding current value I _w flowing through the roller electrode.

Further, 13 is a pair of welding head roller electrodes. 14 is an AC power supply for welding. A constant current device 15 compares the welding current value I _w with a current value I _n set by the condition setting device 7 every half cycle or every cycle so that the welding current I _w becomes equal to the current value I _n. AC power supply 14 is controlled. The operation will be described below with reference to FIG.

Prior to welding, two-ply in condition setting device 7, piled four, setting the current value I _n suitable for 6-ply. Also,
An upper limit value I _nH and a lower limit value I _nL for the current value I _n are set in advance in the upper limit setter 8n and the lower limit setter 9n. In the figure, the current value I _n , the upper limit value I _nH , the lower limit value I _nL, and the welding current value I _w are only peak values on the plus side. Further, it is assumed that the roller electrode 13 starts welding at the two-sheet overlapping position P ₀ and moves in the arrow direction. And
At the position P ₀ , since two sheets are stacked, welding is started at the current value I ₂ set for stacking two sheets. The positions where the welding conditions change will be described below by dividing them.

(A) Between position P ₀ and position P ₁ Welding current value Iw due to impedance changes caused by changes in contact resistance between plates 1 sandwiched by roller electrodes 13 and the like.
Changes a little, but changes between the upper limit I _2H and the lower limit I _2L . Further, the constant current device 15 makes the welding current value I _w approximately equal to the current value I ₂ .

(B) Between position P ₁ and position P _{2 When the} roller electrode 13 moves to the position P ₁ which is the end portion of the stack of four sheets, the number of plates 1 sandwiched between the roller electrodes 13 increases from two to four. . That is, the internal resistance of the plate 1 and the contact resistance between the plates 1 increase, and further, the spacing increases between the two roller electrodes 13 to increase the impedance. Therefore, the welding current value I _w <lower limit value I _2L, and the comparator 11 _2L
Closes. Then, the control unit 10, as the current value for welding, switching it to a current value the current value next highest current value I ₄ of I ₂ which the I ₂ is set to the condition setting unit 7. Then, four layers are welded up to the position P ₂ .

(C) Between position P ₂ and position P _{3 When the} roller electrode 13 moves to the position P ₂ which is the end of the two sheets, contrary to the above (b), the impedance between the roller electrodes 13 decreases and welding Current value I _w > upper limit value I _4H , and comparator 11 _4H closed. Then, the control unit 10 as a current value for welding, so far the current value I ₄ switches to the next lower current value I ₂ of the current value I ₄ that is set on the condition setting unit 7. Then, the two sheets are welded up to the position P ₃ .

(D) Between position P ₃ and position P _{4 When the} roller electrode 13 moves to the position P ₃ which is the end portion of the stack of 6 sheets, the impedance between the roller electrodes 13 increases, and as in (b) above, first the comparator 11 _2L is closed, and the control device 10 switches the current value I ₂ to the current value I ₄ . However, the current value I ₄
Since welding current I _w <lower limit value I _4L ,
1 _4L is closed. Therefore, the controller 10 changes the current value I ₄ to the current value I _4.
Switch to ₆ and weld to position P ₄ .

(E) Between position P ₄ and position P _{5 When the} roller electrode 13 moves to the position P ₄ which is the end portion of the two-sheet stack, the impedance between the roller electrodes 13 decreases, and as in (c) above, first the comparator 10 is the current value I ₄
Switch to I ₂ and weld to position P ₅ .

In this embodiment, the AC power supply 14 is a constant current device.
Although it is controlled by 15, the constant current device 15 may be omitted.
Furthermore, when the upper limit value and the lower limit value for each current value I _n are equal, that is, when the allowable width of the current value I _n is the same, there may be one upper limit setter and one lower limit setter. Needless to say.

〔The invention's effect〕

As described in detail above, according to the present invention, even if the number of stacked plates changes within one welding line, continuous welding can be performed. That is, a change in the number of stacked plates is detected by comparing the measured welding current value with the currently set upper and lower limits of the current value. Then, because the current value is switched and welding is performed according to the comparison result,
For example, unlike the case where a change in the number of stacked plates is detected by a change in the pressing force of the roller electrode, the stacked plates are not affected by the bending. Therefore, repair welding is almost unnecessary even at a construction site or the like, and welding workability is improved.

[Brief description of drawings]

FIG. 1 is a connection system diagram of a welding current control device showing an embodiment of the present invention. FIG. 2 is an operation explanatory diagram. 3 to 4 are explanatory views of the prior art. 1 ... Board, 7 ... Condition setting device, 8 ... Upper limit setting device, 9
...... Lower limit setting device, 10 ...... Control device, 11 _nH , 11 _nL …… Comparator, 12 …… Toroidal coil.

Claims (2)

[Claims] 1. In a current control method in seam welding, in which a plurality of thin plates are superposed and welded, a current value suitable for the number of plates to be stacked is preset for each number of plates to be stacked, and an upper limit is set for each of the current values. Set the value and the lower limit value, measure the actual current value during welding, and when the measured current value exceeds the upper limit of the current value that is currently set, the number of plates on which the current value is set is repeated. A seam characterized by switching to the next smaller current value, and when the measured current value falls below the lower limit of the current value currently set, the number of plates on which the current value is set is switched to the next largest current value. Current control method for welding. 2. A condition setting device capable of setting a plurality of current values, an upper limit setter for setting an upper limit of each of the plurality of current values, and a lower limit for setting a lower limit of each of the plurality of current values. It consists of a setting device, a control device that switches the current value set in the condition setting device, a measuring device that measures the actual current value, and a comparator that compares the actual current value with the upper or lower limit of the current value. , If the output signal of the comparator exceeds the upper limit of the current value that is currently set, the control device switches to a current value in which the number of stacked plates is next smaller, and the output signal of the comparator is A current control device in seam welding, characterized in that, when it indicates that the current value has fallen below the lower limit of the current value, the number of sheets to be overlapped is switched to the next highest current value for welding.