JP2000271763A - Easy diagnostic method of high frequency welding circuit and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily estimate a welding condition during a line stop before the start of operation and to execute a stable operation in on-line by storing a resonant waveform resonating to a high voltage pulse applied to the secondary side of an output transformer and observing the resonant waveform displayed on a monitor to execute diagnosis of abnormality. SOLUTION: When grouped charging switches 33 are successively closed and then opened, a DC power source 32 is connected to capacitors 34 and a DC high voltage is charged by the capacitors 34. When the charge for the high voltage is completed, a high voltage pulse is applied to the secondary side of the output transformer of a high frequency welding circuit by closing a pulse applying switch 36 for a moment and then opening it. At the same time, a resonated voltage waveform is observed using a waveform display 22 having a memory function to store the measured waveform. Since the high frequency welding circuit is easily diagnosed on the basis of the resonant waveform, the change of the state of the welding circuit is observed without executing welding and investigation of a cause is allowed before working of the line starts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for simply diagnosing abnormalities in a high-frequency welding circuit for performing welding by oscillating high-frequency waves. In the following, a high-frequency welding circuit applied to the manufacture of a welded H-section steel will be described as a typical example, but the present invention is not limited to this, and the high-frequency welding circuit used in the manufacture of an ERW pipe is also described. The present invention can be applied to a high frequency welding circuit for performing local welding, such as a spoke of a bicycle, or the like.

[0002]

2. Description of the Related Art FIG. 2 is a side view of a main portion near a welding point showing a method of manufacturing a welded H-section steel by high frequency welding. In FIG. 2, a pair of squeeze rolls 2 include a flange material 3 and a web material 4, which are components (weld to be welded) of the welded H-section steel 1.
Are pressed together to convey them to the left. A contact tip 5 slidably contacting the flange material 3 and the web material 4
, A high-frequency current applied from the high-frequency power supply 6 is supplied.

The high-frequency current generates Joule heat when passing through the flange material 3 and the web material 4 and heats them, and at the same time, flows intensively at a welding point 7 where they come into contact with each other to melt this portion. Therefore, the flange material 3 and the web material 4 are pressed down by the squeeze roll 2 at a welding point 7 where they are in a molten state, and are welded and joined.

The reason why a high-frequency power source is adopted as a welding power source for a welded H-section steel is that a high-frequency current is applied to a very narrow portion necessary for welding a member to be welded (the upper and lower end surfaces of the web material and the end faces of the web material of the flange material face each other). This is because there are various effects (skin effect and proximity effect) that are convenient for the production of a welded H-section steel, in which only the central portion of the width, which is referred to as the welded portion, is effectively heated and melted.

On the other hand, there is a mechanical joint in the path of the welding current (this is related to the magnitude of resistance,
Also, the distance of the current path is related to the magnitude of the inductance), and other equipment is present around the current path (which is related to the magnitude of the capacitance), and these are very vague factors. In addition, the state of welding tends to be extremely unstable. Therefore, when there is a problem in the weldability, the cause is currently investigated by the operator's experience and intuition while directly observing the weld bead.

Particularly, in the case of a welded H-section steel, since the material to be welded is a steel material to which an oxide film is adhered, conduction between the welding device and the material to be welded is poor, and it may be difficult to conduct electricity.
It is also necessary to take measures such as disclosed in JP-263844A (a method and an apparatus for manufacturing a welded H-section steel).

[0007]

As factors that cause a problem in weldability, the mutual relation of the materials to be welded, the insulation state of peripheral machinery and equipment, the positional relationship of peripheral machinery and the like are important points. Another important point is whether there is any abnormality in the welding power source itself. In particular, in the case of welded H-section steel, it is necessary to install two welding devices in a narrow space, and the mechanical equipment for restraining the material to be welded is complicated, so that it is difficult to maintain these conditions at the best. Therefore, the various conditions relating to the weldability are difficult to determine and very vague, which has been a major obstacle to performing stable welding.

In the case where there is a problem in weldability such as insufficient joining of the materials to be welded or the bead is dirty, an operator investigates the cause based on experience and intuition while observing the bead. ing. In other words, this is an inefficient method of finding optimum conditions while producing defective products.

In welding a welded H-section steel, a high-frequency current applied from a welding device to a material to be welded forms a high-frequency welding circuit. An example of this high-frequency welding circuit will be described with reference to FIG. The circuit diagram of FIG. 3 is an example and is simplified. In FIG. 3, a direct current is supplied from the left side of the oscillation tube 62 and is converted into a high frequency using the oscillation tube 62. The frequency of the high frequency is set to about 400 kHz when welding an ERW pipe or a welded H-section steel.

This frequency was brought into contact with the resonance part 61 mainly constituted by the capacitor 63, the welding adapter 20 connected via the output transformer 14, and the contact tip (not shown here) provided at the tip thereof. It is determined by the load-side circuit constant determined from the state of the material to be welded (also not shown) and the like. FIG. 4 shows a state of contact between one example of the welding adapter 20 and the workpieces 3 and 4. The welding adapter 20 is connected to the secondary coil 14b of the output transformer 14 of the high frequency power supply unit 6. The central portion of the welding adapter 20 is insulated by the insulating plate 13, and the high-frequency current supplied through the welding adapter 20 is applied to the workpiece 3 via the contact tips 5 a and 5 b in contact with the workpieces 3 and 4. , 4.

FIG. 5 shows an example of an actual welding adapter 20. The welding adapter 20 of this example includes contact tips 5a and 5b to be brought into contact with the flange material 3 and the web material 4, respectively.
Is attached to one end of the conductive head 10.
Is rotatably coupled to the conductive arm 12 via the fulcrum shaft 11, and the other end of the conductive head 10 is driven by the air cylinder 9 fixed to the conductive arm 12 to rotate forward and backward around the fulcrum shaft 11. It is composed.

Naturally, the conductive head 10, the fulcrum shaft 11, and the conductive arm 12 are all bisected by the insulating plate 13, and are electrically insulated from each other as a power supply route to the contact chips 5a and 5b. Although only the upper part is shown in FIG. 5, the same applies to the lower part. The squeeze roll for rolling down the welding point 7 and the high-frequency power supply connected to the conductive arm 12 are not shown. Further, in the example of FIG. 5, the air cylinder 9 drives the flange material conductive head and the web material conductive head at the same time. However, two air cylinders 9 are provided to drive both independently. It may be.

FIG. 5 also shows an example, and the shape and the like of the welding adapter 20 need not be as shown in the figure.
For example, although the air cylinder 9 is used in FIG. 5 to press the contact tips 5a and 5b against the workpieces 3 and 4,
This may be a hydraulic cylinder or a spring. The welding current supplied to the workpieces 3 and 4 flows along a space between the workpieces called a V-shape, flows intensively along a line where the workpieces are in contact with each other, and is subjected to Joule heat. Heat the welding material. This is a problem with the skin effect and proximity effect described above. The heated workpiece is pressed by a squeeze roll and welded.

FIG. 6 is a diagram showing the welding of the welded H-section steel described above in an electric equivalent circuit. The welding adapter and the material to be welded, which are conductors, also become inductors for high frequencies and cannot be ignored. In addition, the junction of the welding adapter, the oxide film of the material to be welded, and the like are non-negligible registers. In the case of a high frequency, capacitance between conductors and between a conductor and ground cannot be strictly neglected, but is omitted here for simplification.

The equivalent circuit of FIG. 6 can be further simplified to an equivalent circuit shown in FIG. That is, the circuit resonates at a specific frequency (for example, 400 kHz) due to the resonance of the impedance between the resonance unit and the load circuit. Here, if a factor that affects the welding current occurs, for example, a defect in the component of the resonance portion, an increase in the resistance value of the joint portion of the welding adapter on the load circuit side, or a decrease in insulation on the mechanical equipment side, the impedance in FIG. Will change. Further, for example, the same applies to a case where some kind of conductor exists in the vicinity of the high-frequency current conducting portion and a non-negligible capacitance is generated between the ground.

That is, if the state of impedance of the circuit shown in FIG. 7 (a circuit constituted by a resonance section and a load circuit, which is called a resonance circuit) can be easily diagnosed, the state of the circuit can be estimated. Here, in order to measure individual impedances such as capacitance, inductance, and resistance, there are commercially available instruments, respectively, and these can be easily measured using these instruments.

If only a composite impedance is to be measured, a method of applying an AC voltage and observing the voltage and current waveforms can be applied. However, the high-frequency welding circuit described above (corresponding to the resonance circuit of FIG. 7)
Is difficult to measure the current due to the structure of the actual device. In addition, since it is necessary to consider the influence of the insulation performance of the mechanical equipment, evaluation at a high voltage corresponding to the level actually used is required.

In addition, in order to promptly realize stable online operation, it is sufficient if a simple diagnosis of weldability can be realized, and an accurate measured value is not required as a diagnosis result. An object of the present invention is to provide means for easily estimating these conditions in advance in a line stop state before the start of operation, and to quickly realize stable online operation.

[0019]

From the above, the present invention has been made to achieve the object of the present invention by momentarily applying a high-voltage pulse to a high-frequency welding circuit and observing the voltage waveform. The present invention includes a high-frequency power supply unit that oscillates and resonates a high frequency and applies the same externally via an output transformer, and a welding adapter that is connected to the secondary side of the output transformer and has a contact tip at a tip. A simple diagnosis method for a high-frequency welding circuit for easily diagnosing abnormalities in a high-frequency welding circuit, comprising applying a high-voltage pulse to a secondary side of the output transformer and resonating with the applied high-voltage pulse. The above problem was solved by a simple diagnosis method for a high-frequency welding circuit, characterized in that abnormalities could be diagnosed by displaying the stored resonance waveform on a monitor and observing the displayed resonance waveform. .

Further, the present invention provides a high-frequency power source for oscillating and resonating a high frequency and applying the same externally via an output transformer, and a welding adapter connected to the secondary side of the output transformer and having a contact tip at a tip. A high-frequency welding circuit for easily diagnosing an abnormality of the high-frequency welding circuit, comprising: a high-frequency welding circuit connected to a secondary side of an output transformer for applying a high-voltage pulse; The above problem has been solved by a simple diagnosis device for a high-frequency welding circuit including a voltage pulse application device and a waveform display device with a memory function for storing a resonance waveform that resonates with the applied high voltage pulse and displaying the same on a monitor. It is.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a simple diagnostic device for a high-frequency welding circuit according to the present invention. In FIG. 1, a simple diagnostic device for a high-frequency welding circuit according to the present invention includes a high-voltage pulse applying device 30.
And a waveform display device 22 with a memory function.
An output of the high voltage pulse applying device 30 is connected to a secondary side of an output transformer of a high frequency welding circuit (not shown). Then, a resonance waveform that resonates with the applied high-voltage pulse is taken into the waveform display device 22 with a memory function. Here, an example is shown in which the output of the high-voltage pulse applying device 30 is connected to the secondary side of the output transformer of the high-frequency welding circuit to be diagnosed. Of course, it is possible to do so.

Next, the high voltage pulse applying device 30 will be described. In the present device, the DC power supply 32 is connected to the capacitor 34 by sequentially closing and then opening the charging switches 33, and the capacitor 34 connected in series is charged with a high DC voltage. This charging method is already known, and in the case of the present invention, a method of charging a DC high voltage is not particularly defined.

When the high-voltage charging is completed, the pulse applying switch 36 is momentarily closed and opened to apply a high-voltage pulse to the secondary side (welding adapter side) of the output transformer of the high-frequency welding circuit. At the same time, a waveform display device 22 with a memory function having a function of storing the measured waveform is provided.
Is used to observe the resonated voltage waveform. FIG. 8 shows an example of the observed waveform.

In FIG. 8, a normal waveform 40, which is a good resonance waveform in a normal state, is shown by a thick line. On the other hand, for example, 41 shows a waveform when the capacitor of the power supply unit is damaged. In this case, the characteristic is that the frequency of the resonance waveform increases. Next, 42 shows a case where there is a capacitance that cannot be ignored between the conductors, and resonance of a very high frequency occurs due to this capacitance. A state in which such a very high frequency resonance occurs is called a parasitic resonance.

FIG. 43 shows a waveform 43 when the contact resistance at any place in the high-frequency welding circuit is large. In this case, the characteristic is that the attenuation of the waveform increases. By making a determination as described above, based on the observed resonance waveform, diagnosis of the high-frequency welding circuit can be easily performed, and the state change of the high-frequency welding circuit can be observed without actually performing welding, It became possible to investigate the cause while the line was stopped before operating the line.

[0026]

In the online operation of high frequency welding,
Conventionally, it has been confirmed whether there is a problem in weldability while observing a bead, and when there is a problem, the cause has been investigated based on the observation result of the bead. In contrast,
According to the present invention, it is possible to make a prediction diagnosis of the welding state in advance while the line is stopped before starting the operation, and it is possible to quickly realize a stable online operation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a diagnostic device of the present invention.

FIG. 2 is a main part side view for explaining a method of manufacturing a welded H-section steel by high-frequency welding.

FIG. 3 is a schematic circuit diagram of high-frequency welding.

FIG. 4 is a schematic diagram illustrating connection between a welding adapter and a power supply in high frequency welding of a welded H-section steel.

FIG. 5 is a perspective view illustrating an arrangement of a welding adapter in high-frequency welding of a welded H-section steel.

FIG. 6 is an equivalent circuit diagram of high-frequency welding.

FIG. 7 is an explanatory diagram in which an equivalent circuit of high-frequency welding is simplified.

FIG. 8 is a schematic diagram of a waveform shown in the diagnostic device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welded H-section steel (material to be welded) 2 Squeeze roll 3 Flange material (material to be welded) 4 Web material (material to be welded) 5 Contact tip 5A Contact tip (for flange material) 5B Contact tip (for web material) 6 High frequency Power supply unit 7 Welding point 9 Air cylinder 10 Conductive head 11 Support shaft 12 Conductive arm 13 Insulating plate 14 Output transformer 14a Primary coil 14b Secondary coil 20 Weld adapter 22 Waveform display device with memory function 30 High voltage pulse applying device 32 DC power supply 33 Charge switch 34 Capacitor 35 Diode 36 Pulse application switch 40 Normal waveform 41 Waveform when capacitor is damaged 42 Waveform when parasitic resonance exists 43 Waveform when contact resistance is large 61 Resonance section 62 Oscillator tube 63 Capacitor 64 Earth (grounding part)

Claims (2)

[Claims] 1. A high-frequency power supply unit for oscillating and resonating high-frequency waves and applying the same to the outside via an output transformer, and a welding adapter connected to a secondary side of the output transformer and having a contact tip at a tip. A simple diagnosis method for a high-frequency welding circuit for easily diagnosing abnormalities in a high-frequency welding circuit to be performed, comprising:
In addition to applying to the next side, the resonance waveform that resonates with the applied high-voltage pulse is stored, the stored resonance waveform is displayed on a monitor, and abnormality can be diagnosed by observing the displayed resonance waveform. A simple diagnostic method for high-frequency welding circuits. 2. A high-frequency power supply unit for oscillating and resonating high-frequency waves and applying the same to the outside via an output transformer, and a welding adapter connected to the secondary side of the output transformer and having a contact tip at a tip. A simple diagnostic device for a high-frequency welding circuit for simply diagnosing abnormalities of a high-frequency welding circuit to be performed, comprising:
A high-voltage pulse applying device connected to the next side and applying a high-voltage pulse, and a waveform display device with a memory function for storing a resonance waveform that resonates with the applied high-voltage pulse and displaying the same on a monitor Simple diagnostic device for high-frequency welding circuits.