JPH039904Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a contact type high frequency electric resistance welding pipe welding device, and particularly to a control device for a high frequency power supply device.

[Prior Art] A contact type high-frequency electric resistance welding pipe welding device brings an electric contact (chip) supplied with the output of a high-frequency oscillation section of a high-frequency power supply device into sliding contact with the welding part, thereby creating resistance to the high-frequency current flowing through the welding part. Welding with heat generation. The high frequency power supply device is constructed as shown in FIG.
The power control means first steps down the voltage received from the high voltage power supply 1 using a rectifier transformer 2, and controls the output power by voltage control using a thyristor power control section 3.
This output is returned to high voltage by step-up transformer 4,
Through the rectifier 5, a DC output with a controlled output voltage is obtained. The high frequency oscillator 6 uses the output of the power control means as a DC power source to obtain a high frequency oscillation output. Chip 6
A and 6B are brought into contact with the welded part of the welded member 7 and supply the high frequency current of the oscillating part 6 to the welded part.

Among these, the output voltage control of the thyristor power control section 3 is performed based on the output voltage feedback signal from the transformer 4, the output current and voltage of the oscillation section 6, as well as the welding temperature and welding current at the welding section to determine the appropriate amount of heat input. That is, an appropriate output voltage is determined, and the control device 8 controls the thyristor gate phase of the thyristor power control section 3 in accordance with this voltage.

[Problem to be solved by the invention] To start the high-frequency power supply, a soft start is performed in which the output voltage of the thyristor power control section 3 is gradually increased. However, if there is a gap, the load on the high-frequency oscillator 6 becomes open (no-load state), causing abnormal oscillation or inability to oscillate, and startup failure may occur. In particular, poor contact due to the chips 6A and 6B is likely to occur when steel plates are formed into a round shape because the surface to be welded has many irregularities, rust, etc.

[Means and effects for solving the problem] The purpose of the present invention is to ensure that the chip can be started even when there is poor contact between the chip and the material to be welded. By providing a voltage control means that increases the voltage in steps to the voltage necessary to cause dielectric breakdown between the chip and the part to be welded, and gradually increases the voltage from this increased voltage to the operating voltage, the voltage between the chip and the part to be welded can be increased. The purpose is to cause a contact failure to break down due to a step-like increase in output voltage, to cause welding current to flow, and to stably start oscillation of a high-frequency oscillating section.

[Embodiment] FIG. 1 is a circuit diagram of a main part of a control device 8 showing an embodiment of the present invention. A constant voltage +V is applied to the reference voltage setting device 11 through one contact 12A of the relay contacts 12A and 12B that are closed at startup, and the output voltage is set to the operating voltage of the power control means and the soft start circuit 13 is used as input. The soft start circuit 13 performs an integral operation on the output voltage of the setter 11 (voltage that rises in a stepwise manner upon starting) to obtain a reference voltage output that rises at a constant slope up to the output voltage. The voltage control amplifier 14 adds the set voltage of the step voltage setter 15 to the reference voltage output of the soft start circuit 13, and obtains an output voltage control signal by matching this set voltage with the output voltage detection signal Vf of the transformer 4. . A constant voltage is applied to the step voltage setter 15 via a relay contact 12B which is closed when the engine is started, and outputs a set voltage that rises in a stepwise manner. This voltage corresponds to the voltage required to cause dielectric breakdown between the chips 6A, 6B and the weld.

Further, the setting input of the voltage control amplifier 14 is corrected by calculation with other detection elements (for example, welding temperature, current of the oscillator 6), and the output voltage of the amplifier 14 is adjusted to the thyristor power via the gate phase control circuit 16. It is taken out as a gate pulse of the control section 3.

This configuration is different from the conventional one in that the output of the step voltage setter 15 is applied to the reference voltage setting means consisting of the reference voltage setter 11, the soft start circuit 13, and the relay contact 12A at the time of starting. That is, in the conventional control device, when the relay contact 12A, which is closed at startup, is turned on, the soft start circuit 13 obtains an output that increases at a constant slope with respect to the step voltage output of the reference voltage setter 11, and this output is used as the reference output. Use voltage command. This waveform is shown by the dashed line in FIG.

On the other hand, setting device 15 and relay contact 12B
When the contact 12B is closed during startup, the output voltage of the setting device 15 is added to the reference output voltage command of the reference voltage setting means, and the waveform at this time is as shown in FIG. as shown by the solid line. Therefore, at the time of starting, the output voltage of the thyristor power control section 3, that is, the output voltage of the high frequency oscillation section 6, increases rapidly in steps by an amount corresponding to the voltage set by the setting device 15. As a result, even if there is a poor contact between the chips 6A and 6B and the welding part of the welded member 7, the cause of the poor contact can be eliminated by the voltage increase due to the step voltage (for example, 3 to 6 KV in output voltage). It is possible to start the high frequency oscillator 6 without having to open the load by causing current to flow through the welded member.

[Effects of the invention] According to the invention, the output voltage of the high-frequency oscillator is increased in steps at the time of starting, and the increased voltage is gradually increased to the operating voltage, so there is no possibility of poor contact between the chip and the welded part. The dielectric breakdown caused by the step voltage eliminates load open, enables stable and reliable starting, and is effective in improving welding reliability.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the main part of a control device showing an embodiment of the present invention, Fig. 2 is a starting output voltage characteristic diagram of the conventional and the present invention, and Fig. 3 is a high frequency diagram of a contact type high frequency electric resistance welding pipe welding device. It is a circuit diagram of a power supply device. 3... Thyristor power control unit, 5... Rectifier, 6...
High frequency oscillator, 6A, 6B...chip, 7...member to be welded, 8...control device, 11...reference voltage setter, 1
2A, 12B...Starting relay contact, 13...Soft start circuit, 14...Voltage control amplifier, 15...Step voltage setter, 16...Gate phase control circuit.

Claims (1)

[Scope of utility model registration request] a power control means for controlling an output voltage; a high-frequency oscillation section that uses the power control means as a DC power source to obtain a high-frequency oscillation output; and a high-frequency oscillation section that is in sliding contact with a welding part of a workpiece and that applies a high-frequency current of the high-frequency oscillation section to the welding part. In a high frequency power supply device for a contact type high frequency electric resistance welding pipe welding device, the operating voltage of the power control means is set and the set voltage increases at a constant slope from zero voltage to the operating voltage at the time of startup. step voltage setting means for obtaining a set voltage corresponding to the voltage required to cause dielectric breakdown between the electrical contact and the welded portion from the time of startup; and a voltage output of the reference voltage setting means. 1. A control device for a high frequency power supply device, comprising means for adding voltage outputs of the step voltage setting means to obtain an output voltage setting signal from the start to the operating voltage of the power control means.