JPH07115208B2 - Method and apparatus for seam welding for strip connection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention sandwiches a lap joint portion formed by stacking two metal plates (hereinafter referred to as strips) between electrode wheels for seam welding (hereinafter referred to as electrode wheels). The present invention relates to a seam welding method and apparatus for press-welding the entire length of a lap joint while pressing and then running the electrode wheel. Particularly, the welding start position and the welding end position of the lap joint are accurately detected, and the welding current The present invention relates to a seam welding method and apparatus for appropriately controlling "cutting" or "strong" and "weak" of welding current.

(Prior Art) When the start point and the end point of seam welding are detected from the strip width edge of the lap joint portion of the strip, and the appropriate "entering" and "cutting" operations of the welding current are performed, for example, the first Conventional detection methods as shown in FIGS. 2 and 3 are known.

That is, in the case of FIG. 1, the photoelectric switch 15 that can move together with the upper and lower electrode wheels 3 and 4 is provided with a pressure center line a- of the upper and lower electrode wheels.
When the electrode wheels 3 and 4 are mounted on the lap joint a, the photoelectric switch 15 detects the edge E of the lap joint when the electrode wheels 3 and 4 ride on the lap joint, and a welding current is supplied by the operation signal. Further, when the current is cut off, the electrode wheel is separated from the end of the joint portion, and when the photoelectric switch 15 detects the light emission, the welding current energizing operation is cut off.

On the other hand, in the method shown in FIG. 2, photoelectric switches are arranged on the inlet side and the outlet side of the upper and lower electrode wheels 3 and 4, and the photoelectric switch 16 on the inlet side is arranged.
Welding current is input when is turned on, and the photoelectric switch on the output side
When 17 turns on, the welding current energization operation is stopped.

(Problems to be Solved by the Invention) In the former method, it is difficult to adjust the position of the photoelectric switch 15 on the pressurization center line aa of the electrode wheels 3 and 4, and the timing of turning on and off the electric power often deviates. However, it was one of the major causes of the occurrence of sparks and the early wear of electrodes due to sparks.

On the other hand, in the latter method, since the electrode wheels 3 and 4 are energized early before riding on the strip joint, and the electrode wheels are completely separated from the strips, the energization operation is stopped. When the plate width and the plate thickness are different, a large current flows with the electrode pressing force being inconsistent at the moment when the electrode wheel gets on the strip and at the moment when the electrode wheel leaves the strip, sparks are generated, and the electrode wheel is seriously damaged. Therefore, to prevent this photoelectric switch 1
Attempt to adjust the position of 6 and 17, but like this, again,
The position of the sensor was difficult to adjust, and it was still impossible to prevent the occurrence of sparks and unwelded parts.

(Means for Solving the Problem) Therefore, the present invention takes the following technical means as a clue for solving the above problems.

That is, in the case of welding the lap joint portion of the strip to be welded by applying pressure to the seam welding electrode wheel that is rotationally driven, the lap joint on the side where welding is started while the seam welding electrode wheel is rotationally driven. Check the displacement of the seam welding electrode wheel or the change in the electrode pressure during the process of climbing onto the welded part and during the process of moving away from the lap joint on the side where welding is completed while the electrode wheel for seam welding is driven to rotate. Provided are a seam welding method for strip connection and a device therefor for controlling a welding current.

(Operation) Then, according to the present invention, the welding current is changed after confirming the electrode displacement or the change in the pressure applied to the electrode wheel during the process in which the electrode wheel moves onto the joint portion and during the process in which the electrode moves away from the joint portion. Since the control is performed, it is possible to control the on / off of energization while the applied pressure is constant at the welding start position and the welding end position of the lap joint. Therefore,
It is possible to completely eliminate the occurrence of sparks and unwelded portions, which have been seen in the past, and form a good quality welded portion over the entire welding width.

(Example) Hereinafter, the method of the present invention will be described with reference to the drawings. FIG. 3A shows the amount of vertical displacement of the seam welding electrode wheel with respect to the lap joint during the welding process.

As is clear from the transitions of the electrode center points a, b, and c in this figure, the displacement of the electrode wheel changes to the position b when the electrode wheel 3 rotates from the position a and gradually moves to the edge of the lap joint. When the electrode wheel 3 completely rides on the joint W, the displacement amount changes to the maximum value at the position of C.

FIG. 3B is a graph showing the transition of the electrode displacement amount corresponding to the operation during the welding process of the electrode wheel shown in FIG. 3A.

Therefore, as can be seen from this figure, the welding current is switched on and off by the electrode displacement during the process in which the electrode wheel 3 is transferred to the lap joint portion and the change in the electrode wheel during the process in which the electrode wheel is separated from the lap joint portion. It will be.

FIG. 3C is a graph showing changes in the electrode pressing force corresponding to the movement of the electrode wheel shown in FIG. 3A during the welding process.

The electrode pressure is extremely reduced when the electrode wheel 3 moves from the normal pressurization state to the edge E of the lap joint W,
The pressure gradually moves upward in the process in which the electrode rides on the joint portion, and when the electrode wheel 3 completely rides on the joint portion, the applied pressure rises to a constant state.

Then, in this state, the electrode wheel runs over the joint to reach the end of welding, and when it moves down from here, the pressing force begins to decrease again, and when it completely separates from the edge of the joint, the pressing force rises again. Changes to. Therefore, the welding current is switched on and off by detecting a change in the applied force in the section where the electrode wheel moves to the lap joint and a change in the electrode force in the section where the electrode wheel separates from the lap joint.

Next, FIG. 4A is an embodiment of a welding method of strips having different plate thicknesses and plate widths, and FIG. 4B is an electrode corresponding to the operation of the electrode wheel shown in FIG. 4A during the welding process. It is a graph showing the change of the amount of displacement.

Even when strips with different conditions are welded in this way, it is possible to check the electrode displacement in the section of the second stage here, as in the above-described embodiment, to control the on / off of energization.

Incidentally, the present invention is not limited to "entry" and "cutting" of the welding current, weakening the welding current in the section where the electrode wheel is transferred to the lap joint portion and the section away from the lap joint portion, and the electrode wheel is in the joint portion. The "strong" and "weak" of the welding current may be controlled by, for example, increasing the welding current when the vehicle is completely applied with a pressure.

Next, FIG. 5 shows an embodiment of a seam welding apparatus for carrying out the method of the present invention.

Although not shown, an upper frame 1 is supported by a C frame which reciprocally moves on a guide rail in a direction traversing the welding line by a drive cylinder, and is vertically movable by an elevating cylinder 2.

Reference numeral 3 denotes an upper electrode wheel, and 4 denotes a lower electrode wheel. Reference numeral 5 denotes an arm that rotatably supports the upper electrode wheel 3 around a support shaft 6. One end of the arm is rotatably supported by a bracket 7 fixed to the lower surface of the upper frame 1, and the other end is an upper portion. The pressure cylinder 8 supported on the frame is supported on the rod 9 side.

Reference numeral 10 denotes an arm that rotatably supports the lower electrode wheel 4 around a support shaft 11. One end of the arm is rotatably supported by a bracket 13 fixed to the upper surface of the lower frame 12, and the other end is an electrode. A sensor 13 for measuring the electrode pressing force, that is, a load cell 13 is in contact with the wheel center line aa. Further, a sensor 14 for detecting the displacement amount of the upper electrode wheel 3, that is, a potentiometer 14 is attached between the arm 5 supporting the upper electrode wheel 3 and the upper frame 1.

The sensor 14 may be provided on the movable part of the electrode system as described above, or may be directly attached to the electrode wheel. As another embodiment, the piston rod 9 of the pressure cylinder 8 is used as both rods 9'and the sensor 14 'is attached to the rod 9'as shown in the figure, so that the displacement of the electrode wheel can be changed from the movable portion of the pressure system. It can also be measured directly.

The operation of the above configuration will be described with reference to the flowchart of FIG.

In FIG. 6, as shown in FIG. 3, the electrode wheel displacement amount when energized is Aα, the electrode wheel pressing force is Bα, the electrode wheel displacement amount when energized is Aβ, and the electrode wheel pressing force is Bβ. An operation flow when the reference value is determined is shown.

After the end portions of the strip conveyed on the welding line are shear-cut at the clamp position, the cut ends are overlapped to form a lap joint W. And the upper and lower electrode wheels 3, 4
As shown in the figure, the electrode wheel moves forward from the side to the line, and the pressing force and the rotational drive are applied between the electrodes during that time, and the electrode wheel gradually moves up from the edge E of the lap joint W. During this process, a sensor such as the potentiometer 14 or the load cell 13 detects a displacement of the electrode wheel 3 or a change in the applied pressure of the electrode wheel 4, and the detection signal from the sensor is sequentially converted into a digital signal Ax or Bx. Further, sample and hold the data A ₁ and B ₁ before the electrode wheel rides on the lap joint at the point "a". From the above data, the value of Ax-A ₁ or Bx-B _{1 and} the amount of electrode wheel displacement Aα or the amount of applied pressure change Bα that becomes energized
Constantly compare. When Ax-A ₁ ≧ Aα or Bx-B ₁ ≧ Bα is established, an energization start signal is sent to the control device and a welding current is applied between the electrodes via the contactor to start welding.

Then, the electrode wheels 3 and 4 weld the lap joint, and after a certain period of time, the point "C", the displacement of the electrode wheel 3 on the lap joint or the change in the applied pressure of the electrode wheel 4 is again measured by the potentiometer 14
Alternatively, a sensor such as the load cell 13 detects, the output signal from the sensor is converted into digital signals A ₂ and B ₂ , and sample and hold are performed. Then, when the electrode wheel moves to the end of the joint and leaves from it, the value of A ₂ -Ax or B ₂ -Bx and the electrode wheel displacement amount Aβ and the electrode wheel pressure change amount Bβ at which the current is cut off
And A ₂ −Ax ≧ Aβ or B ₂ −Bx ≧ Bβ holds,
An energization stop signal is sent to the control device to stop energization of the contactor and complete seam welding of the entire length of the lap joint.

After the welding is completed, the clamp and the upper and lower electrode wheels 3 and 4 are opened, the strip is threaded, the electrode wheels 3 and 4 are returned to the original state, and they are ready for the next operation.

(Effects of the Invention) As described above, according to the method of the present invention, it is possible to confirm the vertical displacement or the change in the pressure applied to the electrode wheel during the process in which the electrode wheel moves onto the joint portion. Since the welding current is controlled, it is possible to control the turning on and off of the energization with good timing in a constant state even at the welding start position and the welding end position of the lap joint. Therefore, it is possible to completely eliminate the occurrence of sparks, unwelded portions, electrode damage due to sparks, and the like, which have been conventionally observed, and form a good quality welded portion over the entire welding width.

Further, according to the device of the present invention, the true pressurization state can be accurately detected by simply attaching the above detector to either the movable part of the electrode system or the movable part of the pressurization system, and the welding current input / output accuracy can be improved. It has an excellent effect that it can be attached to an existing device at low cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of plate edge detection in a conventional seam welding method. FIG. 2 is a schematic view showing another plate edge detection in the conventional seam welding method. FIG. 3A is an explanatory diagram showing the vertical displacement during the welding process of the seam welding electrode wheel with respect to the lap joint. FIG. 3B is a graph showing the transition of the electrode displacement amount corresponding to the operation during the welding process of the electrode wheel shown in FIG. 3A. FIG. 3C is a graph showing changes in the electrode pressing force corresponding to the movement of the electrode wheel shown in FIG. 3A during the welding process. FIG. 4A is an embodiment of a welding method for strips having different plate thicknesses and widths, and FIG. 4B shows the electrode displacement amount corresponding to the operation during the welding process of the electrode wheel shown in FIG. 4A. A graph showing the transition. FIG. 5 is a schematic front view showing an embodiment of a seam welding apparatus for carrying out the method of the present invention. FIG. 6 is a flowchart showing the operation flow of the device of the present invention. [Explanation of reference symbols] 3, 4 ... electrode wheel for seam welding 13, 14 ... sensor W ... lap welding joint, E ... edge

Claims (2)

[Claims] 1. When welding a lap joint portion of a strip to be welded under pressure and current through a rotationally driven seam welding electrode wheel, the side on which welding is started while the seam welding electrode wheel is rotationally driven. Of the seam welding electrode wheel or the change in electrode pressure during the process of riding on the lap joint part of The seam welding method for strip connection, which is to check the welding current and control the welding current. 2. A device for seam-welding the entire length of a lap joint by pinching a lap joint to be welded with a seam welding electrode wheel and applying a pressing force and a welding current to the electrode wheel while rotating the electrode wheel. In the welding process, a sensor that detects a change in the electrode wheel or a change in the electrode pressing force and outputs an output signal is provided in the electrode wheel or a movable part of the electrode system or the pressurizing system. Electrode displacement or pressure displacement during the process of riding on the lap joint on the side where welding is started while rotating, and during the process of leaving the lap joint on the side where welding is completed while the driven electrode wheel is rotating. A seam welding device for connecting a strip, which performs on / off operation of welding current and / or pressure control.