JP2002172466A - Capacitor discharge type stud welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor discharge type stud welding method small in incomplete penetration by making the current at the starting time of welding generate a fast and large arc. SOLUTION: In the capacitor discharge type stud welding method wherein a stud metal 21 is welded to a base metal 22 by quick-discharging a charge charged in a capacitor 11 into the stud metal 21 brought into contact with the base metal 22 through a switching element 13, a variable resistor 15 is provided on a discharge circuit of the capacitor 11 in series to quick-discharge the charge of the capacitor 11 substantially in the state of a resistance load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of charging a large-capacity capacitor, discharging the charge in a short time to a weld formed between the tip of the stud material and the base material, and converting the stud material to the base material. The present invention relates to a capacitor discharge type stud welding method for welding a stud.

[0002]

2. Description of the Related Art Capacitor discharge stud welding is known as a method for welding bolts, pins, etc. to a base material (workpiece, workpiece). This welding method does not require a large-capacity power source. It is widely used because it can be welded quickly and easily. FIG. 4A shows a circuit configuration of this capacitor discharge stud welding method. The capacitor 60 is charged in advance through a charging circuit (not shown), and charges the capacitor 60 through a thyristor 61 and a reactor 62 connected in series. The stud material 65 is welded to the base material 66 by the arc heat generated at this time. FIG. 4B shows a current waveform at the time of welding. When the switch for starting welding is operated, the thyristor 61 is turned on and the capacitor 60 is turned on.
However, since the reactor 62 has the reactor 62, the current at the start is suppressed, the current gradually increases, and then the current waveform generally decreases.

[0003]

In the conventional capacitor discharge stud welding method according to the prior art, the stud material is held down by a spring provided inside the welding gun 63, so that the first capacitor 60 is not used. At the time of the discharge, the base material 66
When a current flows over a certain current (at time t1), an arc is generated at the tip of the stud material 65, and the stud material 65 is immediately pressed against the base material by the spring (t1).
2:00) The welding had been completed. Therefore,
In FIG. 4 (B), an arc generation time is between t1 and t2. For this reason, the electric charge accumulated in the capacitor 60 is not effectively used, and an arc is generated by a gradually increasing current, so that it is difficult to generate an arc having a large weld, and there is a problem that poor penetration is likely to occur. Was. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a capacitor discharge type stud welding method in which the current at the start of welding is increased to generate a fast and large arc, and the penetration defect is small.

[0004]

According to the present invention, there is provided a capacitor discharge type stud welding method according to the present invention, wherein electric charges charged in a capacitor are rapidly discharged to a stud material brought into contact with a base material via a switching element. A capacitor discharge type stud welding method for welding the stud material to the base material, wherein a variable resistor is provided in series with a discharge circuit of the capacitor, and the electric charge of the capacitor is rapidly discharged in a substantially resistive load state. ing. In the present invention, since the load is substantially not provided with inductance and the discharge of the capacitor is performed in the state of a resistance load, the current flowing at the start of welding becomes maximum and gradually decreases. As a result, an arc is generated at the same time as the start of welding, the weld is immediately melted, and the stud material is pressed against the base metal when the pressing force of the stud material exceeds the pushing force of the stud material by the arc. Here, in the capacitor-discharge-type stud welding method according to the present invention, the variable resistor may have a resistance of 0.1 mm.
It is preferably in the range of 01 to 1 ohm. Further, it is preferable that welding is performed in a state where the stud material is constantly urged against the base material by a spring. As a result, an arc is generated by the rapid discharge current at the time of starting, so that heat can be more efficiently supplied to the welded portion.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is an explanatory diagram of a welding apparatus to which the capacitor discharge stud welding method according to one embodiment of the present invention is applied, FIG. 2 is a graph showing a temporal change of a welding current during welding, and FIG. (A)-(D) are explanatory diagrams of a variable resistor.

FIG. 1 shows a welding apparatus 1 to which a capacitor discharge stud welding method according to an embodiment of the present invention is applied.
0, the welding apparatus 10 includes a large-capacity capacitor 11 and a charging circuit 12 for the capacitor 11, a thyristor 13 which is an example of a switching element connected in series to the capacitor 11, a stud welding gun 14, And a variable resistor 15 connected in series to the circuit of FIG. Less than,
These will be described in detail.

The capacitor 11 is composed of a large-capacity capacitor (for example, 100,000 μF). A charging circuit 12 for charging the capacitor has a function of rectifying an AC power supply and charging the capacitor 11 to a predetermined voltage in a relatively short time. To charge. As the thyristor 13, a thyristor having a capacity sufficient to rapidly discharge the electric charge of the capacitor 11 is used, and a gate control circuit 16 for supplying a signal to the gate of the thyristor 13 is provided. The gate control circuit 16 operates a start switch 18 provided on the handle 17 of the stud welding gun 14 to send a signal current to the gate of the thyristor 13 to rapidly discharge the charge of the capacitor 11. .

A commercially available stud welding gun 14 is used. A power supply rod 19 is provided inside the power supply rod 19 so as to be vertically movable, and an attachment (conductive mounting bracket) 20 is provided below the power supply rod 19. Stud material 2
1 is attached. The power supply rod 19 is constantly urged against the base material 22 by a spring disposed inside the stud welding gun 14. Stud welding gun 14
Up and down support 24 with multiple legs 23
By changing the mounting height of the support 24, the pressure applied to the stud member 21 by the internal spring is changed. In FIG. 1, reference numerals 25 and 26 denote conductor cables whose outsides are covered with an insulating material, and reference numerals 27 and 28 denote connection terminals.

A variable resistor 15 is connected in series with the capacitor 11.
, The structure of the variable resistor 15 will be described with reference to FIG. The variable resistor 15 is, as shown in FIG. 3A, a linear resistor 30, fixing brackets 31 and 32 attached to both ends of the resistor 30, and is attached to the resistor 30 so as to be able to move laterally. And a sliding metal fitting 33. The resistor 30 has a rectangular cross section and is made of a material having relatively high electric resistance, such as stainless steel, iron, and nichrome. As shown in FIG. 3B, the fixing bracket 31 is made of copper or brass, and in some cases, is made of iron, and has bolt holes 34 and 35 for mounting on both sides.
Is fixed by welding or brazing. A tap is formed at the upper center of the fixing bracket 31, and a terminal fitting 36 attached to the other end of the conductor cable having one end connected to the connection terminal 28 is screwed to the fixing fitting 31. I have. The terminal fitting 36 can be attached to the fixing fitting 31 by directly brazing.

As shown in FIG. 3 (C), the fixing bracket 32 has a metal fitting main body 37 and a rectangular cylindrical insulator 38 disposed inside the metal fitting main body 37. Are fitted and supported. Bolt holes 39 and 40 are provided on both sides of the metal fitting body 37. As shown in FIG. 3D, the sliding bracket 33 includes two plate members 41,
42, bolts 43 for screwing them at both ends thereof,
44. On the back side of the plate member 41 and on the front side of the plate member 42, there are provided grooves 45 and 46 in which the resistor 30 is partially fitted. The total depth of the grooves 45 and 46 is
When the plate members 41 and 42 are joined by the bolts 43 and 44 at both ends when the thickness is smaller than 0, the sliding bracket 33 is fixed to the resistor 30 with the plate members 41 and 42 sufficiently tightening the resistor 30. It is a structure that can be done. A terminal fitting 47 attached to the other end of the conductor cable having one end connected to the capacitor 11 is fixed to the center of the front side of the plate member 41. The method of fixing the terminal fitting 47 may be brazing or a screw such as a bolt. Therefore, in the variable resistor 15, the position of the slide metal member 33 is moved to change the resistance between the fixed metal member 31 having the terminal metal member 36 and the slide metal member 33 having the terminal metal member 47 attached thereto. I have. This variable resistor 15 is directly connected to the capacitor 11, but if it is a discharge circuit of the capacitor 11,
Another location (for example, before and after the thyristor 13) may be used.

The capacitor discharge type stud welding method according to one embodiment of the present invention will be described in detail using the welding apparatus 10 having the above-described configuration. When the start switch 18 is operated while the capacitor 11 is charged through the charging circuit 12, the thyristor 13 is turned on,
The electric charge of the capacitor 11 flows to the base material 22 via the protrusion at the lower end of the stud material 21. At this time, since a current flows through the variable resistor 15, the current becomes a resistive load, and a current flows as shown by a broken line in FIG. As a result, a rapid large current flows through the protrusion at the tip of the stud member 21, and an arc is generated in this portion. At this time, the stud material 21 is urged toward the base material side by the spring, but the state is momentarily maintained due to a rise in the pressure of the atmosphere due to the generation of the arc, and the discharge of the capacitor 11 starts to decrease and the arc force is reduced. When it becomes weak, the stud material 21 is pressed against the base material 22 by the spring, and the welding is completed. Therefore, an arc is generated during the period of t3 in FIG. Here, by making the spring weaker than the conventional one, the arcing time can be prolonged. When a resistance load is applied, the energization time becomes longer, but in this case, the current flows through the welded portion after welding, so that this portion is heated and the effect of preventing the welded portion from being rapidly cooled in a short time is effective. is there.

As described above, by setting the discharge circuit of the capacitor 11 to a resistance load having no inductance, it is possible to prevent the current from gradually increasing after the start of welding, and to start up quickly with the start of welding to charge the capacitor 11. Increase the charge to arc energy. by this,
The generated arc is generated in a wide range, and the stud material 21 and the base material 22 are more efficiently melted, so that more reliable welding can be performed. Actually, since there is some reactance in a conductor cable or the like, there is a first rise as shown by a solid line in FIG. 2, but the reactance is extremely small as compared with the resistance value of the variable resistor 15, so that the influence is affected. Is almost negligible. The value of the variable resistor 15 needs to be changed depending on the size and material of the stud material to be welded, and the maximum value of the flowing current depends on the charging voltage E of the capacitor 11 and the total resistance value R mainly of the variable resistor 15. Divided by. Generally, the charging voltage of the capacitor 11 is about 50 to 300 V, so that the resistance value of the variable resistor 15 is adjusted to about 0.01 to 1 ohm. Note that the variable resistor 15 is set to 0.0
Even if it is set to 1 ohm, the internal resistance of the capacitor 11 and the internal resistance of the circuit and the cable will be smaller than the theoretical value, but the internal resistance can be obtained by experiment.

In the above embodiment, a plate-shaped resistor is used as the resistor of the variable resistor, but a resistor having another shape may be used. It is preferable to use a capacitor having as low an internal resistance as possible.

[0014]

As is apparent from the above description, the capacitor discharge type stud welding method according to claims 1 to 3 has the discharge circuit of the capacitor in a resistance load state, so that a large current is generated at the start of welding. Therefore, a large arc is generated from the beginning of welding, and the spread of the arc is expanded to enable more stable welding.
Further, since the current remaining in the capacitor flows through the weld even after the welding is completed, rapid solidification of the weld can be prevented, and the weld can be prevented from becoming brittle.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a welding apparatus to which a capacitor discharge stud welding method according to an embodiment of the present invention is applied.

FIG. 2 is a graph showing a temporal change of a welding current at the time of welding.

3A to 3D are explanatory views of a variable resistor, FIG. 3A is a plan view of the variable resistor, and FIG. 3B is a diagram of FIG.
Is a sectional view taken along the line AA in FIG. 2, (C) is a sectional view taken along the line BB in FIG. (A), and (D) is a sectional view taken along the line CC in FIG.

FIGS. 4A and 4B are explanatory diagrams of a capacitor discharge stud welding method according to a conventional example.

[Explanation of symbols]

10: welding equipment, 11: capacitor, 12: charging circuit,
13: Thyristor, 14: Stud welding gun, 15:
Variable resistor, 16: gate control circuit, 17: handle, 1
8: Start switch, 19: Power supply rod, 20: Attachment, 21: Stud material, 22: Base material, 23:
Leg, 24: support, 25, 26: conductor cable, 2
7, 28: connection terminal, 30: resistor, 31, 32: fixing bracket, 33: sliding resistance, 34, 35: bolt hole, 36:
Terminal fittings, 37: fitting body, 38: insulator, 39, 4
0: bolt hole, 41, 42: plate material, 43, 44: bolt, 45, 46: groove, 47: terminal fitting

Claims (3)

[Claims] 1. A capacitor discharge type stud welding method for rapidly discharging a charge charged in a capacitor to a stud material abutting on a base material through a switching element and welding the stud material to the base material. A capacitor discharge type stud welding method, characterized in that a variable resistor is provided in series with the discharge circuit of the capacitor, and the electric charge of the capacitor is rapidly discharged under a substantially resistive load. 2. The capacitor discharge type stud welding method according to claim 1, wherein the variable resistor has a resistance of 0.01 to 1.5 mm.
A capacitor discharge stud welding method characterized by being in the range of 1 ohm. 3. The capacitor discharge type stud welding method according to claim 1, wherein the stud material is welded while being constantly urged to the base material by a spring. Stud welding method.