JPH0646618Y2 - Analog control capacitor discharge type stat welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an analog control type capacitor discharge type stud welding apparatus.

[Conventional technology]

Generally, the capacitor discharge type stud welding device accumulates electric charge from an AC power source to a required charge level in a capacitor through a power transformer and a rectifier, and welds the charge voltage of the capacitor under the control of the charge / discharge control circuit of the capacitor. It is configured to perform stud welding by causing an electric discharge between the stud attached to the gun and the base material.

As a conventional example of a capacitor charge / discharge control circuit, Japanese Patent Publication No.
In this example, two DC power supplies are used, and the potential of the circuit that supplies a closing signal to the switching control element of the circuit that charges the capacitor is compared with the potential of the capacitor. , Thereby detecting whether or not the charging potential of the capacitor is at the set value.

Further, Japanese Patent Publication No. 57-50596 is configured so that when the capacitor is charged to a set value, the circuit for generating an ignition signal to the charging circuit of the capacitor is cut off and an ignition signal to the discharging circuit of the capacitor is generated. A control circuit is disclosed.

Further, as another conventional example of the charge / discharge control circuit of the capacitor, the one disclosed in JP-B-58-41947 can be cited.

[Problems to be solved by the device]

In the conventionally known capacitor discharge type stud welding apparatus as described above, the charge / discharge control circuit of the capacitor keeps the charge voltage level of the capacitor constant, but in reality, the charge characteristic of the capacitor is shown in FIG. As shown by the curve I, a so-called overshoot occurs, which exceeds the set charge level. This fluctuation amount is about 3 to 5% of the normally set charge level, but it was found that it greatly affects the welding characteristics of the stud. That is, when a stud is welded to a relatively thin base material, an unsightly welding trace appears on the back surface of the base material, and the size and shape of the stud welding surplus vary.

Therefore, an object of the present invention is to provide an analog control type capacitor discharge type stud welding device in which a charging characteristic which is set in the charging of a capacitor is jumped over and a so-called overshoot is eliminated so that the charging characteristic becomes gentle from around the set charging voltage level. To do.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, an analog control type capacitor discharge type stud welding device according to the present invention provides a capacitor for storing welding energy for welding a stud to a base metal using a welding gun and a charging voltage of this capacitor. A first voltage detecting circuit for setting and detecting, a second voltage detecting circuit for setting and detecting a voltage exceeding a charging voltage level set by the first voltage detecting circuit, and a first circuit for charging the capacitor. And a charge adjusting circuit including a series circuit of a second switching element and a resistor connected in parallel to the switching element of
When the charging voltage level set by the voltage detecting circuit is reached, the first switching element is cut off, and the second switching element is ignited by the output signal of the second voltage detecting circuit to charge control circuit. It is characterized in that it is configured to continue to charge up to a predetermined charging voltage of the capacitor via.

[Action]

In the analog control type capacitor discharge type stud welding apparatus according to the present invention configured as above, the capacitor is first charged through this circuit by the ignition of the first switching element of the charging circuit, and the charging voltage of the capacitor is set to the first value. When the charging voltage level set by the voltage detection circuit is reached, the first switching element of the charging circuit is cut off. At the same time, the second voltage detection circuit sends an output signal to the second switching element in the charge regulation circuit to fire the second switching element. As a result, the charging of the capacitor is succeeded via the charge adjusting circuit, and the capacitor is charged to the final charging voltage set by the second voltage detecting circuit with a gradual charging characteristic, and the second voltage detecting circuit then performs this final charging. When the voltage is detected, the charge adjustment circuit is shut off. In this case, when the actual charging voltage of the capacitor has already reached the expected charging voltage set by the second voltage detection circuit for some reason with respect to the charging voltage level set by the first voltage detection circuit, The voltage detection circuit of No. 2 turns on and off the charge adjustment circuit almost at the same time, and the capacitor is not substantially charged through the charge adjustment circuit,
When the charging voltage of the capacitor decreases, the charging is continued via the charging adjustment circuit, and the charging voltage of the capacitor can always be accurately maintained at the set voltage level. By such two-stage charging, the capacitor can be charged with a charging characteristic without overshoot.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

In FIG. 1, 1 is an AC power source, 2 is a power transformer, 3 is a rectifier, and a charging circuit 4 is provided between the output terminals of the rectifier 3.
A capacitor 6 for storing required welding energy is connected via the first switching element 5, and a stud 9 and a base material 10 are connected to a discharge circuit 7 of the capacitor 6 via a switching element 8.

Reference numeral 11 denotes a first voltage detection circuit, which detects the relative charging voltage level of the capacitor 6 and controls the charging circuit 4 of the capacitor 6 to the first level depending on whether or not the charging voltage of the capacitor 6 is at the set charging voltage level. The switching element 5 is controlled to be turned on and off. This first voltage detection circuit 11
Can have a normal circuit configuration with a variable resistor, and the charging voltage level of the capacitor 6 can be set by adjusting the variable resistor, and the set value is a digital display value (not shown) provided on the front panel of the device. ) To be displayed digitally.

Reference numeral 12 is a second voltage detection circuit, which is configured in the same manner as the first voltage detection circuit 11, that is, the second voltage detection circuit 12 can set the final charging voltage of the capacitor 6, and this set capacitor When the final charging voltage of 6 (overshoot above this voltage) is reached, a detection signal is output. The output of the second voltage detecting circuit 12 is composed of a charge adjusting circuit (a series circuit of a second switching element 13 and a resistor 14) connected in parallel to the first switching element 5 in the charging circuit 4 of the capacitor 6. 2) is connected to the gate electrode of the second switching element 13 in FIG.

In the operation of the illustrated device thus configured, first, the knob of the digital indicator provided on the front panel of the device is turned to adjust the variable resistance in the first voltage detection circuit 11,
The charging voltage level of the capacitor 6 is set. Charging circuit 4
When the first switching element 5 is fired, the capacitor 6 begins to charge and charges towards the set voltage level L as shown by curve II in FIG. When the charging voltage of the capacitor 6 approaches the set voltage level L, the first voltage detecting circuit 11 causes the first switching element 5 of the charging circuit 4 to operate.
Cut off. At the same time, the second voltage detection circuit 12 sends an ignition signal to the gate electrode of the second switching element 13 of the charge adjustment circuit to cause the switching element 13 to fire. As a result, the charging of the capacitor 6 is succeeded via the charging adjustment circuit, and the charging characteristic with substantially no overshoot is obtained.

[Effect of device]

As described above, according to the present invention, a charging adjustment circuit is provided in parallel with a charging circuit of a capacitor that stores welding energy for welding a stud to a base metal by using a welding gun, and a charging voltage of the capacitor is set. Until the value is reached, charging is performed through the normal charging circuit, and thereafter, charging is taken over through the charging adjustment circuit that provides a gradual charging characteristic, so the charging voltage of the capacitor is always the set voltage. The level can be maintained accurately, and as a result, it is possible to avoid the effects of instantaneous charging voltage fluctuations such as overshooting, and it is possible to obtain consistent welding characteristics.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, and FIG.
The figure is a voltage waveform showing the charging voltage characteristic of the capacitor. In the figure 1: AC power supply 2: Power transformer 3: Rectifier 5: First switching element 6: Capacitor 11: First voltage detector 12: Second voltage detector 13: Second switching element 14: Resistor

Claims (1)

[Scope of utility model registration request] 1. A capacitor for storing welding energy for welding a stud to a base material using a welding gun, a first voltage detection circuit for setting and detecting a charging voltage of the capacitor, and the first voltage detection. A second voltage detection circuit for setting and detecting a voltage exceeding the charging voltage level set by the circuit, and a series connection of a resistor and a second switching element connected in parallel to the first switching element of the capacitor charging circuit. A charge adjusting circuit composed of a circuit, which shuts off the first switching element when the charge voltage of the capacitor reaches the charge voltage level set by the first voltage detecting circuit and the second voltage. The second switching element is ignited by the output signal of the detection circuit and the charging of the capacitor is continued via the charge adjusting circuit. Analog display type capacitor discharge stud welding apparatus.