JP2002160070A - Seam welding method and controlling method for welding quality - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve determination accuracy of a welding quality by quantitively monitoring a margin in a joint part of a seam welding. SOLUTION: In a mash seam welding method, the joint part wherein metal materials are slightly overlapped is pinched by electrode rings, pressurizing force and welding current which are required for the welding is supplied to the electrode rings, and the seam welding is conducted by rotating and driving the electrode rings and by crushing the length of the joint part so as to roughly be closed to the same plate thickness as at least one side of the plate thickness of a base material. In this method, the amount of displacement e of a lap margin in a weld is detected by an image sensor b before the metal materials are started to weld at every welding, and when the detected amount of displacement is within a preset allowable value, a seam welding start signal is issued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of lap resistance welding, and more particularly, to a lap joint formed by slightly overlapping metal plates (work) to be welded, before welding. The present invention relates to a seam welding method and a welding quality control method that enable quantitative management of initial set values and quality control of welding after welding.

[0002]

2. Description of the Related Art Among seam weldings used for plate joining,
In mash seam welding, equivalent thicknesses or differences in thickness, metal plates of different materials are slightly overlapped, and a lap joint is sandwiched between rotating electrode wheels for seam welding and pressurized to rotate the electrodes while supplying welding current. In addition, the present invention is a welding method for forming a smooth welded portion by crushing the overlapped portion so as to reduce the thickness to a thickness substantially equal to at least one base material.

[0003] There are various combinations of tailored blanks, such as different plate thicknesses and dissimilar metal plates, and the welding is reliably performed by uniformly maintaining the overlap margin between the welding start point and the welding end point of the lap joint portion of the plate material. There is a need.

[0004] The conventional mash seam welding machine generally requires a work holding jig in order to prevent the overlapping joint from shifting as described above. The work holding jig is provided with a clamp device for firmly fixing the metal plate to be welded to the work entrance side and the work exit side. The work holding jig is a rigid jig having a considerable clamp load. After the lap joint portion of the metal plate is positioned by the clamp device, welding is performed by moving the work holding jig or the seam welding machine.

In this case, the conventional work holding jig incorporated in the seam welding machine is provided with positioning pins for positioning the plate to be welded, and is positioned in a locate hole provided at a predetermined position of the work when setting the work. Positioning is performed by inserting a pin. On the other hand, as another positioning method, positioning has been performed by clamping the upper and lower end faces of the lap joint on the basis of the position where the end faces abut against a contact sensor such as a gauge bar.

In the conventional seam welding described above, the following cases are known as a method for quality control of a welded portion. (1) Indirectly managing the change amount of the upper electrode wheel by catching that the reduction ratio of the electrode wheel changes proportionally due to the change in the wrap amount. (2) The change in the amount of lap was compared with the amount of heat generated during welding, and the temperature was indirectly controlled by a radiation thermometer. (3) The change in the lap amount is compared with the change in color due to heat generated during welding, and indirectly managed by a color-specific image sensor.

[0007]

However, when using the positioning pins in the conventional method to keep the overlap allowance uniform, it is necessary to machine a locating hole in the work, which not only requires a lot of man-hours but also requires a work set. It must be done manually and automation is difficult.

In the conventional method of checking the lap amount by disposing a contact sensor on the butt end face, the sensor is brought into direct contact with the butt end face, so that the gauge bar is quickly consumed or damaged. It was difficult to quantitatively secure a reliable lap allowance due to variations in measurement accuracy.

On the other hand, in the conventional welding quality control method, in the case of the above (1), the change in the lap amount is changed by the change amount of the electrode wheel, and the accuracy changes depending on the roundness of the electrode wheel, so that the reliability is lacking. Things.

In the method (2), the change in the amount of wrap is compared with the amount of heat generated, and there is a variation due to the degree of surface treatment of the material or a difference between the energized position and the measured position. It lacks.

In case (3) above, the change in the amount of lap is compared with the change in color due to the heat generated during welding. It was unreliable.

[0012]

[Means for Solving the Problems] Accordingly, the present invention has been developed to solve the above-mentioned conventional problems.
The specific configuration is such that a joint portion in which metal plates are slightly overlapped is sandwiched between electrode wheels, a pressing force and a welding current necessary for welding are supplied to the electrode wheels, and the electrode wheels are rotated to drive the electrode wheels. In a mash seam welding method in which seam welding is performed while crushing the entire length of a joint portion to a thickness substantially equal to at least one base metal plate, a margin for overlapping a welded portion before starting the welding of the metal plate for each welding. The amount of displacement is detected by an image sensor, a comparison operation is performed to determine whether the detected amount of displacement is within a preset allowable value, and a seam welding start signal is generated based on the comparison result. .

According to a second aspect of the present invention, the image sensor measures an overlap margin by using an image pattern from a camera disposed at or near an end face of the metal plate opposite to the overlap joint. .

According to a third aspect of the present invention, a joint portion in which metal plates are slightly overlapped is sandwiched between electrode wheels, a pressing force and a welding current necessary for welding are supplied to the electrode wheels, and the electrode wheels are connected. In a mash seam welding method of performing seam welding while rotating and crushing the entire length of the joint portion to a thickness substantially equal to at least one base metal plate, welding is performed before starting welding of the metal plate for each welding. The displacement sensor detects the displacement of the overlap margin of the part, and performs a comparison operation to determine whether the detected displacement is within a preset allowable value, and starts seam welding based on the comparison result. A displacement sensor detects a displacement amount in the width direction of the metal plate before and after welding by a displacement sensor, and performs a comparison operation to determine whether a difference between the displacement amounts before and after the welding is within a predetermined allowable range, The comparison And judging the quality of the quality of the seam weld by.

According to a fourth aspect of the present invention, the displacement sensor is a non-contact sensor such as a photoelectric switch, a proximity switch, and an image sensor.

[0016]

FIG. 1 is a schematic diagram showing an apparatus for carrying out the method of the present invention. The basic configuration of this device is composed of a work holding jig for supporting a work to be welded, a clamp device arranged on the entrance side and the exit side opposite to each other, and a mash seam welding machine.

In the seam welding machine, a metal sheet S1 and a metal plate S2 set on a work holding jig are slightly overlapped with each other, and an overlapping margin is sandwiched between an upper electrode wheel 1 and a lower electrode wheel 2 for seam welding. A welding force and a welding current required for welding are supplied in between, and the electrode is driven to rotate to continuously crush the entire length of the welded portion to at least a thickness substantially equal to at least one of the base materials, thereby performing seam welding. I do.

An example of a generally known procedure for positioning a shift type overlapped portion will be described below. (1) In this case, the two metal plates (left and right) to be welded are sent to a predetermined position of the work holding jig manually or by a work input device. (2) At this time, the fixed-side clamp device 3 and the movable-side clamp device 4 arranged on the work holding jig are on standby with the upper clamp beam opened. (3) The clamp device 4 on the moving side moves forward to a predetermined welding center line. (4) When the tip of the moving-side clamp device 4 is positioned at the welding center line, it is closed. (5) The tip of the metal plate S1 is abutted against the tip of the clamp device 4 on the moving side as a stopper, and the clamp beam of the clamp device 3 on the fixed side is closed to press the metal plate S1. (6) Open the clamp device 4 on the moving side and open the next metal plate S2.
And insert the metal plate S2
Press the tip of. (7) After hitting the metal plate S2, the upper clamp beam on the moving side is closed and the metal plate S2 is pressed. As a result, the overlap of the two plates is positioned. (8) Thereafter, the moving-side clamp device 4 is retracted from the welding center line to a predetermined position, and the lap amount (e) is regulated by the joint portion of the seam welding, and the clamp is firmly held. (9) Enter the welding process. In this case, the work holding jig is moved to the seam welding machine having the upper electrode wheel 1 and the lower electrode wheel 2 or the work holding jig side is fixed and the seam welding machine side is moved to open the seam welding machine. When the lap margin is fed onto the press center line of the upper electrode wheel 1 and the lower electrode wheel 2 from the welding start point to the welding end point of the overlap margin, the upper electrode wheel presses the upper electrode wheel between them. When a current flows between the lower electrode wheels and the upper and lower electrode wheels are rotated, the plate material is sequentially fed in the advancing direction by this driving force, and seam welding proceeds.

In the overlap margin of the seam weld shown in FIG. 4, it is necessary to set an appropriate lap amount (e) in accordance with the combination of the thicknesses to be welded and to secure the mutual positions uniformly. Therefore, as shown in FIG. 1, the present invention uses the image sensor 6 to set the lap amount (e) of the metal plates S1 and S2 and secure the mutual position, so that the image sensor 6 is disposed on both sides of the overlap joint portion of the metal plates S1 and S2. It was arranged at or near the end face. In this embodiment, the camera 6
Are arranged on both sides of the joint so as to be shifted to an arbitrary position.

Image information input from the cameras 6 on both sides is recognized as data, and image information of a lap margin sampled in advance is set as an appropriate welding condition in a reference video pattern.

For each work set, data of a lap image projected by the camera is input, and the input image data is compared with reference image data stored in advance to calculate a difference between displacement amounts of a lap allowance within an allowable value. When it is determined that there is, a welding start signal is output and welding is started. Also, the system is configured to output an abnormal signal to the outside when the displacement amount is outside the allowable value. For example, the allowable value range is set to an upper limit of 3.5 mm to a lower limit of 2.7 with respect to a reference set value of the overlap margin of 3 mm.
If the measured value based on the input image data is within the allowable value (upper / lower limit value), the welding start signal is output. If the measured value is out of the allowable value, an abnormal signal is output to the outside.

Immediately below the electrode wheel, when electricity is supplied,
The overlap margin is crushed together with the softening to form a joint as shown in FIG. 5, and the welding is completed.

When expansion or crushing during energization or heat generation, the overlap (e) of the unwelded portion is reduced due to the component force due to the plastic deformation in the width direction of the plate (the direction ⇒ in FIG. 5) and the thermal effect. As a result, as shown by the solid line in FIG. 3, the welding quality varies, and if it is remarkable, a uniform overlap margin cannot be secured (the plate to be joined gradually opens due to the component force due to plastic deformation and thermal influence). ), Poor welding.

As a countermeasure in this case, quantitative data management is possible for the welding current, the pressing force, and the speed element, and the fluctuation range (accuracy) is a value that is sufficient within a range that does not affect the welding quality. is there. In addition, the initial lap of the welding line can be eliminated by a method of abutting against a gauge or a method using a locating pin.

However, in addition to the relationship between the sheet thickness and the amount of lap, the change factors of the lap amount, the change of the friction coefficient due to the cutting accuracy and the burr situation, the clamping force and the surface condition, the change due to the thermal influence during welding, and the welding Variable components such as the component force generated in the direction perpendicular to the line and the difference in rigidity inherent to the machine are compounded, and it is difficult to quantitatively manage it in an actual production line.

Therefore, in order to realize the quantitative welding quality control method described above, according to a third aspect of the present invention, as shown in FIG. 3, a displacement sensor 5 is provided on the end face of the metal plate to be welded opposite to the welding side. A method for quantitatively managing data before and after welding for each welding position by comparison and calculating whether the difference is within the allowable value was developed.

That is, the difference (v) between the position data before welding and the position data after welding is detected for the plate end on the side opposite to the welding side, and the difference between the detected value and the lap amount stored in advance as optimum conditions is detected. It is possible to easily determine the necessity of the welded portion by calculating and comparing the set value to be performed and detecting the difference in the lap amount.

The detector 5 can obtain the same function and effect with a photoelectric switch, a proximity switch, an image sensor, and the like.

The metal plates S1, S2 in the ⇒ direction shown in FIG.
Is moved by the detector 5 at the end of the sheet material on the non-welding side of the metal sheet.
(That is, the end surface of the plate opposite to the welding side is managed by detecting the movement in the ⇒ direction).

It should be noted that the welding method and quality control method of the present invention can be carried out in various welding fields other than resistance welding used for plate joining without departing from the principle of the present invention.

[0031]

As described above, according to the welding method of the present invention, the displacement of the overlap of the welded portion is detected by the image sensor before the welding of the metal plate is started for each welding, and the displacement is determined in advance. Since the seam welding start signal is issued in comparison with the set allowable value, in comparison with the conventional method of securing the overlap allowance by using the positioning pin, the locating hole machining is no longer required and the machining cost is not required. Automation of work set becomes easy.

Compared with the conventional method of checking the lap amount by applying a sensor to the butt end face, non-contact eliminates wear and breakage of a sensor such as a gauge bar, and further improves measurement accuracy and ensures reliable lapping. The cost can be secured quantitatively.

According to the welding quality control method of the present invention, the change in the lap amount before welding is checked by the image sensor, and after welding, the position change of the plate is monitored by the displacement sensor or the image sensor, and the displacement of the plate is monitored. This directly reads whether the amount is within the allowable value, and improves the welding quality judgment accuracy and facilitates quality control.

[Brief description of the drawings]

FIG. 1 is a principle view showing a case where the welding method of the present invention is applied to a mash seam welding machine.

FIG. 2 is a principle diagram showing a case where the welding quality control method of the present invention is applied to a mash seam welding machine.

FIG. 3 is a principle diagram showing an embodiment in the case of managing the displacement amount of a lap portion before and after welding by mash seam welding according to the present invention.

FIG. 4 is a view showing a cross-sectional shape of a lap joint portion before mash seam welding.

FIG. 5 is a diagram showing a sectional shape of a welded portion after mash seam welding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper electrode wheel 2 Lower electrode wheel 3 Fixed side clamp device 4 Moving side clamp device 5 Displacement sensor 6 Image sensor

Claims (4)

[Claims] 1. A joint portion in which metal plates are slightly overlapped with each other is sandwiched between electrode wheels, a pressing force and a welding current required for welding are supplied to the electrode wheels, and the electrode wheels are rotated to drive the joint portion. Mash seam welding method in which seam welding is performed while crushing the entire length of at least one of the base materials to a thickness substantially equal to the thickness of at least one of the base materials, the displacement of the overlap of the welded portion before starting the welding of the metal plate for each welding The amount of displacement is detected by an image sensor, a comparison operation is performed to determine whether or not the detected displacement is within a predetermined allowable value, and a seam welding start signal is generated based on the comparison result. Method. 2. The seam welding according to claim 1, wherein the image sensor measures an overlap margin by using an image pattern from a camera disposed at or near an end surface of the metal plate opposite to the lap joint. Method. 3. A joint portion in which metal plates are slightly overlapped is sandwiched between electrode wheels, a pressing force and a welding current necessary for welding are supplied to the electrode wheels, and the electrode wheels are rotated to drive the joint portion. Mash seam welding method in which seam welding is performed while crushing the entire length of at least one of the base materials to a thickness substantially equal to the thickness of at least one of the base materials, the displacement of the overlap of the welded portion before starting the welding of the metal plate for each welding The displacement is detected by a displacement sensor, a comparison operation is performed to determine whether the detected displacement is within a preset allowable value, and seam welding is started based on the comparison result. The displacement in the width direction of the plate after welding is detected by a displacement sensor, and a comparison operation is performed to determine whether or not the difference between the displacement before and after welding is within a predetermined allowable range. Quality A quality control method for a mash seam weld characterized by determining the quality of a mash seam weld. 4. The quality control method according to claim 3, wherein said displacement sensor includes a photoelectric switch, a proximity switch, an image sensor, and the like.