JPH05245650A - Power unit for spot welding machine - Google Patents

Abstract

PURPOSE:To obtain a high welding current with a relatively small capacity power source and to optionally pet the welding time by ON and OFF of the gate voltage of a thyristor. CONSTITUTION:A battery 8 is connected in series to a transformer 2 of a welding circuit 9, the DC voltage of the battery 8 is superimposed on the AC voltage generated on the transformer 2 to generate the resultant voltage, a maximum value of the AC voltage is set slightly higher than the voltage of the battery 8 and welding is performed on a weld zone 11 by the welding current based on the resultant voltage. In addition, the thyristor 10 to rectify an AC part of the resultant voltage is connected and the gate voltage of the thyristor 10 is turned OFF, by which the welding current is stopped to complete welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power source device for a spot welding machine using a battery as an auxiliary power source.

[0002]

2. Description of the Related Art A conventional spot welding machine stores an electric charge in a capacitor from an AC power source and discharges the electric charge stored in the capacitor in an instant, thereby utilizing the heat generated by the current to perform spot welding. I was going.

[0003]

However, in the above-mentioned conventional welding machine, the power supply capacity is very large and a large-capacity power supply is required, so that it is difficult to secure the power supply. In addition, the welding time is extremely short at 10 Hz (about 1/6 second), and the welding time cannot be arbitrarily determined.

[0004]

In order to solve the above problems, the present invention connects a welding circuit to an AC power source via a transformer, and connects a battery in series to the transformer of the welding circuit to connect the transformer to the transformer. While superimposing the DC voltage of the battery on the generated AC voltage to generate a composite voltage,
The maximum value of the AC voltage is set to be slightly higher than the voltage of the battery, and welding is performed by a welding current based on the combined voltage, and a thyristor for rectifying an AC component of the combined voltage is connected to the thyristor. The spot welding machine power supply device is characterized in that the welding current can be stopped by turning off the gate voltage.

[0005]

When welding, a voltage is applied to the gate of the thyristor to turn it on. Then, in the welding circuit, a combined voltage in which the DC voltage of the battery is superimposed on the AC voltage generated in the transformer is generated, and a welding current flows based on the combined voltage, so that welding can be performed by the current.

When the welding is stopped, the gate voltage of the thyristor is turned off. Then, the alternating current component of the combined voltage is rectified by the thyristor within one cycle and the combined voltage becomes zero, so that the welding current is stopped and the welding can be stopped.

[0007]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a power source device for a spot welding machine according to the present invention, in which 1 is an AC power source, 2 is a transformer connected in parallel to the power source, a primary coil 3, a charging coil 4 and a welding coil. It is composed of 5.

Reference numeral 6 is a charging circuit composed of the charging coil 4, the charging thyristor 7 and the battery 8. By applying a voltage to the gate 7a of the thyristor 7, the thyristor 7 is turned on and generated between the coils 4. The battery 8 is adapted to be charged by the current B based on the voltage.

Reference numeral 9 denotes a welding circuit composed of the welding coil 5, the battery 8, the welding thyristor 10 and the welded portion 11. By applying a voltage to the gate 10a of the welding thyristor 10 (at this time, The charging thyristor 7 is off), and a current A flows due to the combined voltage of the AC voltage generated between the welding coils 5 and the DC voltage of the battery 8 to form a welding circuit. At this time, the maximum value Ea of the AC voltage generated between the welding coils 5 is set to be slightly larger than the battery voltage Eb.

The present invention is constructed as described above, and its operation will be described below with reference to FIGS. First, a voltage is applied only to the gate 7a of the charging thyristor 7 to turn on the thyristor 7, the charging circuit 6 is formed, and the battery 8 is charged with the current B.

When welding is performed, the charging thyristor 7 is used.
Is turned off, a voltage is applied to the gate 10a of the welding thyristor 10 at time t ₁ , and the thyristor 10 is turned on (see FIG. 2).
See) Welding circuit 9 is constructed.

At this time, since the welding circuit 9 has a structure in which the battery 8 is connected to the welding coil 5 in series, the voltage applied to the circuit 9 is the AC voltage (maximum value Ea) generated by the coil 5 and the battery. voltage Eb is the voltage that is superimposed (see the hatched portion in FIG. 2), the welding current a flows on the basis of the voltage, the welding from the time t ₁ is started.

Further, since the maximum value Ea of the AC voltage generated by the welding coil 5 is set to be slightly larger than the battery voltage Eb as described above, the times t ₂ and t
_The voltage is cut by the rectifying action of the welding thyristor 10 during the period ₃ , but since the welding thyristor 10 maintains the ON state, the voltage rises again after the time t ₃ .
The current A enables continuous welding.

When the welding is finished, the gate voltage of the welding thyristor 10 may be turned off at time t ₄ (see FIG. 3).

Then, the voltage applied to the welding circuit 9 becomes zero at time t ₅ within one cycle due to the alternating current, and thereafter the welding thyristor 10 is maintained in the off state, so at the time t ₅ . The welding current A is stopped and welding can be stopped completely.

As described above, according to the present invention, the battery 8 is connected to the welding circuit 9 to which the AC voltage is applied from the power source 1, and a large current is obtained by the combined voltage obtained by adding the battery voltage to the AC voltage. Therefore, it is possible to reduce the capacity of the power supply as compared with the conventional device.

The gate 10 of the thyristor 10 for welding is also used.
The welding time can be arbitrarily set by adjusting the time for applying a voltage to a, that is, the time between times t _{1 and} t ₄ (for example, 1 second to 10 seconds).
Seconds). Therefore, the metal can be melted and welded by Joule heat by passing a small current for a long time, and sufficient welding can be performed with a power source having a relatively small capacity.

Furthermore, since the battery voltage is set to a voltage slightly higher than the maximum value of the alternating current applied to the welding circuit 9, the welding current A can be easily stopped by stopping the gate voltage of the welding thyristor 10. The welding can be ended by, for example, a complicated technology such as a chopper used for stopping the electric current from the battery is not required, and the welding can be started and stopped with an extremely simple circuit configuration. ..

FIG. 4 shows another embodiment of the present invention, in which an AC voltage is double-wave rectified by a thyristor.

That is, in the figure, after charging the battery 8'of the charging circuit 6'and turning off the charging thyristor 7 ', the gates 12a and 13 of the welding thyristors 12 and 13 are shown.
When a voltage is applied to a at time t ₁ (see FIG. 5), the AC voltage generated in the welding coil 5 ′ is double-wave rectified,
Welding can be performed with a voltage as shown in.

Then, at time t ₂ , both thyristors 1 described above are
When the gate voltages of 2 and 13 are turned off, the voltage applied to the welding circuit 9'is
Since the thyristor 12 at time t ₃ is turned off, the thyristor 13 at time t ₄ is turned off, it is possible to stop the welding by stopping the welding current.

Also in this embodiment, it is possible to obtain the same effect as that of the circuit shown in FIG. 1, and it is possible to obtain a higher voltage as compared with the embodiment shown in FIG.
In FIG. 4, 1'is an AC power supply, 2'is a transformer,
3'is a primary coil.

[0023]

As described above, according to the present invention, a large current can be obtained by the combined voltage obtained by adding the battery voltage to the AC voltage generated in the transformer, so that the capacity of the power supply is made smaller than that of the conventional device. be able to.

Further, since the welding time can be arbitrarily determined by adjusting the time for applying the voltage to the gate of the thyristor, a small current can be passed for a long time to perform welding, and a power source having a relatively small capacity is sufficient. Welding can be performed.

Further, since the battery voltage is set to a voltage slightly higher than the maximum value of the alternating current generated in the transformer, it is possible to easily stop the welding current and finish the welding simply by stopping the gate voltage of the thyristor. It is possible to start and stop welding with an extremely simple circuit configuration without requiring a complicated technique such as a chopper used to stop the electric current from the battery.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a power supply circuit device for spot welding machines of the present invention.

FIG. 2 is a waveform diagram of a combined voltage showing a welding start state.

FIG. 3 is a waveform diagram of a combined voltage showing a state of completion of welding.

FIG. 4 is an electric circuit diagram showing another embodiment of the power supply circuit device for the spot welding machine.

5 is a waveform diagram of a combined voltage of the circuit of FIG.

[Explanation of symbols]

 1 AC power supply 2 Transformer 8 Battery 9 Welding circuit 10 Welding thyristor 10a Gate 11 Welding part

Claims (1)

[Claims] 1. A welding circuit is connected to an AC power source via a transformer, a battery is connected in series to the transformer of the welding circuit, and a DC voltage of the battery is superimposed on an AC voltage generated in the transformer to synthesize the AC voltage. A thyristor for generating a voltage, setting the maximum value of the AC voltage to a value slightly larger than the voltage of the battery and performing welding with a welding current based on the combined voltage, and rectifying the AC component of the combined voltage. Is connected and the gate voltage of the thyristor is turned off so that the welding current can be stopped.