JPH0247312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency resistance spot projection welding machine.

Conventional resistance welding machines of this type are classified into alternating current type, capacitor type, rectification type, and low frequency type based on the welding current delivery method, and each type has the following characteristics.

The AC type is a commonly used method because the structure of the welding machine is simple, the price is low, and resistance welding can be performed over a wide range of areas. Advanced control devices are currently being manufactured and can control the welding current in various ways, but because the basic frequency uses a power source with a commercial frequency, the minimum time unit for current control is 1/2 of the commercial frequency. This becomes a cycle, and control in a shorter period of time is impossible.

Capacitor type welding machines are manufactured from small to large sizes, and various welding conditions are performed by changing the welding current by changing the charging voltage of the capacitor and the turns ratio of the welding transformer.

However, since the welding current is generated by discharging the charge stored in the capacitor, in order to obtain a welding current that rises quickly, it is necessary to reduce the actance from the primary side of the welding transformer. As a result, the welding transformer becomes larger and the shape of the transformer secondary conductor becomes constrained.

Furthermore, a welding current with a slow rise has limitations, such as the inability to effectively utilize the energy stored in the capacitor.

For the rectifier type and low frequency type, the minimum time unit that can be controlled is 1/2 cycle of the commercial frequency, just like the AC type, and control in shorter time is not possible. The rise time of the welding current is determined by the shape of the secondary conductor of the welding machine, the reactance of the rectifier circuit, and the reactance of the transformer. Although it is possible to slow down the rise of the current using a control device, it is better to make it faster. is difficult due to the above constraints.

Therefore, the present invention provides a high-frequency resistance spot projection welding machine that expands the scope of conventional welding by enabling welding that was difficult or impossible with the conventional methods described above. The purpose is to

An embodiment of the welding machine of the present invention will be described below with reference to the drawing of FIG. In the figure, 1 is a commercial frequency power supply, 2 is a converter that converts alternating current to direct current, 3 is a variable resistor as a welding current control means to control the magnitude of welding current, and 4 is an inverter that converts direct current to high frequency. , 5 is a variable resistor as an output time control means for controlling the high frequency output time, 6 is a variable resistor as a slope control means for controlling the slope, 7 is a high frequency welding transformer, and 8 is a variable resistor of the transformer 7. It is a conductor that connects the secondary side, the spot or projection electrode 9, and the workpiece 10. Although not shown, it is equipped with a pressure mechanism as a resistance welder.

And power supply 1, converter 2, inverter 4,
The transformer 7, electrode 9, and workpiece 10 are connected in series as shown in the figure, and the variable resistor 3 is connected to the converter 2.
Variable resistors 5 and 6 are provided in inverter 4, respectively.

Then, converter 2 converts the commercial frequency alternating current of power supply 1 to direct current, and converts the direct current to inverter 4.
The welding current is converted into a high frequency current by the transformer 7, and the high frequency current is further converted into an appropriate welding current by the transformer 7 and supplied to the electrode 9 to perform spot welding or projection welding on the workpiece 10.

In addition, the slope is controlled by the variable resistor 6, that is, the current width of each cycle of the high frequency is controlled.
Various slope (up slope/down slope) currents as shown in the figure can be obtained.
With this control, the heat input period and cooling period (current = 0) can be adjusted independently of the control of the current magnitude for the workpiece made of a material with an imbalanced heat balance (material with a difference in heat capacity). It is possible to control the heat input (temperature rise) to the workpiece to achieve a pulsation effect that is appropriate, and as a result, the range of welding performance can be greatly expanded.

The welding current is adjusted by the variable resistor 3, and the high frequency output time is set by the variable resistor 5.

The high frequency welding machine of the present invention constructed as described above has the following features.

(1) As shown in Figure 2, the minimum controllable unit time is shorter than that of the conventional methods shown in Figures 3 to 6, so the rise (angle θ in each figure) is faster (rise angle The welding current can be passed through the workpiece (almost perpendicular), and the current of each high frequency cycle can be controlled to produce various slope currents (up slope, down slope) as shown in Figure 7. By using waveforms ranging from those with a quick rise to the conventional waveforms, it is suitable for welding materials with good thermal conductivity, thin materials, protrusion-shaped items, small items, etc.

Note that FIG. 3 shows the current for one cycle of the commercial frequency in an AC type. _Iw indicates the effective value of welding current, and θ indicates the rising angle. FIG. 4 shows the welding current of the capacitor type, FIG. 5 shows the welding current of the three-phase full-wave rectification type, and FIG. 6 shows the welding current of the three-phase low-frequency type.

(2) If an inverter that converts the voltage into a rectangular wave high-frequency voltage is used as the power source that converts the voltage into a high-frequency voltage, energy with good thermal efficiency as shown in FIG. 8 can be applied to the workpiece. That is, FIG. 8 shows that the high-frequency type waveform A is more efficient in imparting thermal energy to the workpiece than the AC type waveform B.

(3) Due to the high frequency, the welding transformer is smaller than the conventional type, and depending on the capacity, it can be built into the pressure mechanism of the welding machine, making it possible to manufacture a welding machine with good workability and efficiency. It is.

(4) It has better thermal efficiency than conventional methods, so there is less heat influence on areas other than the welded area.

(5) Various slope currents can be obtained by controlling the slope, that is, controlling the current width of each cycle of the high frequency, using the slope control means. With this control, the heat input period and cooling period can be controlled independently of the current magnitude control for workpieces made of materials with an imbalanced heat balance, and the heat input period and cooling period can be controlled independently of the current magnitude. It can produce a pulsation effect with appropriate heat input, greatly expanding the range of welding capabilities.

As described above, according to the present invention, it is possible to provide a high frequency resistance spot projection welding machine having various features.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a welding machine according to the present invention, FIG. 2 is a welding current waveform diagram of the same welding machine, and FIGS. 3 to 6 are welding current waveform diagrams of a conventional welding machine.
FIG. 7 is a slope current waveform diagram of the welding machine of the present invention;
FIG. 8 is a comparison diagram of welding currents between a welding machine according to the present invention and an AC welding machine. 1... Commercial frequency power supply, 2... AC-DC converter (converter), 3, 5, 6... Variable resistor,
4...DC-high frequency converter (inverter), 7...
...High frequency welding transformer, 8... Connection conductor, 9... Electrode, 10... Welded object.

Claims (1)

[Claims] 1. A high-frequency power supply device comprising a converter that converts a commercial frequency power source to direct current, and an inverter that converts the output of this converter to a high-frequency power source;
A pressurizing mechanism that includes a high-frequency welding transformer that converts a high-frequency power source into the current necessary for welding, an electrode that pressurizes and energizes the workpiece, and a conductor that connects the electrode and the high-frequency welding transformer. A high frequency resistance spot projection welding machine comprising: a slope control means for slope control provided in the inverter of the high frequency power supply device.