JPS5837064B2 - Power supply for stud welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device for arc stud welding, which reduces minute short circuits that occur during the period when an arc is generated between a stud bolt and a base metal, and which also reduces The purpose is to improve welding quality by keeping the welding and short-circuit currents at set values.

First, a conventional power supply device for arc stud welding of this type will be described. FIG. 1 is a characteristic diagram showing the relationship between output current and output voltage of the device.

As can be seen from this characteristic diagram, conventional devices adjust the output using resistors, actors, etc., and have a simple configuration.When a micro short circuit occurs during arc generation, the output current increases. It has the advantage of suppressing short circuits in a short period of time.

On the other hand, as shown in Fig. 2, when the stud is welded into the base material after an arc occurs, the short circuit current becomes excessive as shown in A in Fig. 2, and the molten metal may be blown away or the stud gun may This method has disadvantages such as overheating of the cabtire cable connected to the cable, and variations in the voltage drop due to changes in the power supply voltage and cable temperature, resulting in unstable welding conditions.

On the other hand, Fig. 3 shows a conventional device different from the conventional device explained above. In the figure, 1 is a welding transformer, 2 is a welding current adjustment circuit consisting of semiconductor switching elements such as Cyrisk, and 3 is a welding current adjustment circuit. 4 is a gate signal generation circuit for circuit 2; 5 is a differential amplification circuit that compares and amplifies the reference signal of reference signal generation circuit 6 and the welding current proportional signal transmitted from welding current detection circuit 3; be.

FIG. 4 is a characteristic diagram showing that when the output is adjusted using circuit 2 in the above device, the relationship between output current and output voltage becomes approximately a constant current characteristic. The shortcomings have been resolved.

On the other hand, when a micro short circuit occurs during arc generation, the short circuit time may become longer, resulting in insufficient heat input.

In addition, in the case of Fig. 1, the short circuit current is
Methods to reduce the amount as shown in B and C in the figure have also been devised, but
In this case, there is a drawback that the switching device for switching the resistor, actuator, etc. is large and expensive.

The present invention eliminates such conventional drawbacks, and one embodiment thereof is shown in Fig. 5, a characteristic diagram showing the relationship between output current and output voltage is shown in Fig. 6, and an operation diagram is shown in Fig. T. are shown respectively.

Figure 5 shows an arc voltage detection circuit 7 in the conventional device shown in Figure 3.
This is an additional feature. Therefore, the differential amplifier circuit 5
will compare and amplify the signal from the arc voltage detection circuit T in addition to the two input signals in the apparatus of FIG.

Then, set the voltage of the arc voltage detection circuit 7 to 15 V or arc voltage (normally, arc voltage > 15 V), and change the amplification degree of the differential amplifier 5 below this arc voltage value (approximately 15 V at most). By configuring the arc voltage detection circuit T to generate a signal in which the output current gradually increases as the output voltage decreases, and the differential amplifier 5 to perform operations such as combining this signal with the reference signal, as shown in FIG. It is possible to obtain the output current vs. output voltage characteristics shown in FIG.

That is, the output current has a substantially constant current characteristic when the output voltage is higher than the arc voltage, and when the voltage is lower than that, the output current increases as the voltage decreases.

Further, as shown by the dotted line, a switching means or the like is provided so that the current characteristic is substantially constant even at the voltage below the above-mentioned voltage.

With this configuration, the output current increases in the event of a minute short circuit that occurs during arc generation (D in Figure 1), and the short circuit time can be minimized. This allows welding with constant heat input without being affected by changes in power supply voltage or voltage drop due to cables.

Furthermore, as shown in Fig. 7A, turn the welding operation switch ON.
After the arc is generated and the stud welding is performed, the solenoid for pushing the stud is turned on as shown in FIG.

The current at the time of short circuit may be switched to A, B, or C as necessary.

According to the power supply device for stud welding of the present invention as described above, it is possible to perform arc stud welding with constant heat input, and furthermore, it is possible to maintain the short circuit current during stud welding at a preset value, so that it is uniform. This enables welding with high quality.

[Brief explanation of drawings]

Figure 1 is an output current vs. output voltage characteristic diagram of a conventional device.
Fig. 2 is an operating characteristic diagram of the same device, Fig. 3 is a block diagram of another conventional device, Fig. 4 is an output current-output voltage characteristic diagram of the same device, and Fig. 5 is an implementation of the device according to the present invention. The block diagram of the example, Figure 6 is the output current-output voltage characteristic diagram of the same device,
FIG. 7 is a diagram showing the operating characteristics of the device. 1... Welding transformer, 2... Welding current adjustment circuit, 3... Welding current detection circuit, 4...
...Gate signal generation circuit. 5...Differential amplifier circuit, 6...Reference signal generation circuit, 7...
Arc voltage detection circuit.

Claims (1)

[Claims] 1 The welding current circuit is provided with a welding current adjustment circuit and a welding current detection circuit, and an arc voltage detection circuit that detects the arc voltage is provided, and when the output voltage is higher than the arc voltage by this arc voltage detection circuit, the output current and output are The relationship with the voltage is made to exhibit approximately constant current characteristics, and at voltages lower than the arc voltage, the output current increases as the output voltage decreases, and the stud welding signal causes the output voltage to exhibit approximately constant current characteristics until the point where the output voltage is zero. A power supply device for stud welding, characterized in that it is configured to be switchable according to the characteristics.