JPS5841947B2 - Control circuit device for manual capacitor discharge type stud welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit device for a capacitor discharge type stud welding machine.

Conventionally, charge is stored in a capacitor from an AC power source through a power transformer and a rectifier, and the charge is discharged directly or through a welding transformer to the stud weld, and the charging voltage leg of the capacitor and the on/off of the discharge circuit are controlled by SCR. Various stud welding machines have been proposed that are configured to perform welding operations using switching elements such as The capacitor is configured not to discharge, but to shut off its charging circuit as soon as the capacitor's charge reaches a predetermined value.

However, with such conventional stud welding machines, if the welding gun is triggered before the capacitor has charged to a predetermined value, the capacitor will not discharge, but at the same time the capacitor will stop charging and the welding gun will Studs loaded in the can also be fired.

Therefore, operation of the welding gun before charging the capacitor to the set value not only interrupts charging of the capacitor, but also causes loss of the stud itself, resulting in a significant reduction in work efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved control circuit arrangement to eliminate the above-mentioned drawbacks of conventional stud welding machines.

That is, according to the present invention, in a capacitor discharge type stud welding machine that welds a stud to a base metal using the charge of a capacitor, the capacitor discharge starts by operating a welding gun before charging the capacitor to a set value, and To prevent interruptions in charging, a circuit is provided that continues to hold the capacitor in a charged state regardless of actuation of the welding gun trigger switch while the capacitor is charging.

This circuit includes an SCR or a GTO or a transistor.

The present invention will be further described below with reference to the accompanying drawings.

The drawing shows an embodiment of the present invention, in which AlB is a power terminal, ST is a power transformer, V is a power switch, and D1 to D1.
1 is a diode, R1-R13 are resistors, VRl, VB2
is a variable resistor, C1 to C5 are capacitors, z1 to z5 are constant voltage diodes, 81 to S3 are silicon controlled rectifiers, T
1 is a transistor, T2 is a single junction transistor, PT is a pulse transformer, GS is a welding gun trigger switch, CR
is a relay, CR1 to CR3 are normally closed contacts of relay CR, C
R4 is a normally open contact, GC is the solenoid coil of the welding gun,
BM is the base material, and S is the stud.

The input terminal of the rectifier bridge consisting of diodes D1 to D4 is connected via a power switch 8V to the secondary side of a power transformer ST constituting the power supply device.

A welding capacitor C1 is connected between the output terminals of this rectifier bridge via a silicon-controlled rectifier S1 that constitutes a switching element, and a discharge circuit of the capacitor C1 is connected between one plate of this capacitor C1 and the base material BM. A silicon-controlled rectifier S2 is inserted which forms the switching element of.

Further, a series circuit consisting of variable resistors VRI, VR2 and resistor R11 is connected in parallel to capacitor C1, and the charging voltage of capacitor C1 can be set by variable resistor VR1 or VB2.

The transistor T1 constitutes a control circuit, and the base of this transistor T1 is connected to a resistor R12 and a constant voltage diode Z.
5 to the tap of the variable resistor VR1, and its emitter is connected to a common conductor connected to one of the output terminals of the rectifier bridge.

The collector of the transistor T1 is also connected via resistors R3, R1 between the output terminals of the rectifier bridge and the switching element S1 of the charging circuit.

Single junction transistor T2 is silicon controlled rectifier S1
, constitutes the trigger oscillation circuit of S3, the emitter of which is connected to the collector circuit of the transistor T1 via the constant voltage diode Z3 and the diode DI, and the first base of which is connected to the output terminal of the rectifier bridge and the charging via the resistor R5t R1. It is connected between the switching element S1 of the circuit and the second base is connected on the one hand to the common conductor via a diode D8 and on the other hand to the primary side of the pulse transformer PT.

The secondary side of this pulse transformer PT is connected on the one hand to the gate terminal of the switching element S1 of the charging circuit via a normally closed contact CRI of a relay CR and on the other hand to the gate terminal of the switching element S3 via a resistor R8. be done.

This switching element S3 is connected between the output terminals of the rectifier bridge in parallel with the series circuit of trigger switch GS and relay CR of the welding gun.

Also, although the switching elements are silicon controlled rectifiers in the illustrated embodiment, they may alternatively be comprised of GTO thyristors or transistors.

Furthermore, a series circuit consisting of the normally closed contact CR3 of the relay CR and the capacitor C4 is inserted in parallel between the series circuit of the trigger switch GS and the relay CR and the switching element S3. The connection point between and capacitor C4 is normally open contact CR4 of relay CR, and resistor R.
9 and a diode D11 to the gate terminal of the switching element S2 of the discharge circuit of the capacitor C1.

Also in the illustrated embodiment, the solenoid coil GC of the welding gun is connected between the output terminal of the rectifier bridge and the switching element S1 of the charging circuit via a normally closed contact CR2 of a relay CR, a resistor R2, a diode D5 and a resistor R1. be done.

The operation of the apparatus of the present invention constructed in this manner will be described below.

First, assume that capacitor C1 is in a discharged state.

In this state, the voltage across capacitor C1 is zero, and therefore the resistances of resistor R11 and variable resistors VR1 and VR2 are also zero.

When the trigger switch GS of the welding gun is opened as shown, the secondary voltage of the power transformer ST passes through the power switch SW and is rectified by the rectifier bridge D1-D4, and the resistor R1
, R3, the diode DI and the constant voltage diode z3 to charge the capacitor C3.

When the charging voltage of this capacitor C3 reaches a predetermined value,
Single junction transistor T2 conducts.

As a result, a pulse signal is generated on the secondary side of the pulse transformer RT, which pulse signal is supplied via the resistor R7, the diode D9 and the normally closed contact CRI to the gate terminal of the switching element S1 of the charging circuit, which Firing element S1.

Thereby, capacitor C1 begins to charge.

As the charging voltage of capacitor C1 increases, resistor R11,
The voltages of variable resistors VRI and VR2 and constant voltage diode Z5 also rise.

When the voltage applied to the voltage regulator diode Z5 is lower than its Zener voltage, the voltage regulator diode Z5 has a high impedance, so the current flowing through the resistor R12 to the base of the transistor T1 is extremely small. It remains in a cutoff state.

However, when the voltage applied to the voltage regulator diode Z5 reaches its Zener voltage, the voltage regulator diode Z5 becomes a low impedance, so a current flows to the base of the transistor T1 via this voltage regulator diode and the resistor R12, and this transistor T1 is conductive.

The result is a bypass through resistors R1, R3 and the collector and emitter of transistor T1.

Therefore, the voltage of the capacitor C3 drops, and the oscillation of the single junction transistor T2 forming the oscillation circuit stops.

As a result, no ignition signal is generated on the secondary side of the pulse transformer PT and the switching element S1 is switched off.

Therefore, charging of capacitor C1 is stopped.

Charging of the capacitor C1 that stores welding energy in this way is set by the resistor R11 and variable resistors VR1 and VR2, and this set voltage is controlled only by the charging voltage of the capacitor C1.

On the other hand, when the single i combination transistor T2 is conductive, the pulse transformer P
The ignition signal generated on the secondary side of T is also supplied via a resistor R8 to the switching element S3 which short-circuits it, making it conductive.

That is, during oscillation of the oscillation circuit consisting of the single-junction transistor T2, in other words, until the capacitor C1 is charged to the set value, the switching element S3 is used as the ignition capacitor C4 of the switching element S2 of the discharge circuit and the trigger switch of the welding gun. GS and relay CR are substantially electrically cut off.

Therefore, while charging the capacitor C1, the trigger switch GS
Even if the capacitor C1 is inserted, the phosphor-CR does not operate and has no effect on the charging/discharging circuit of the capacitor C1.

Capacitor C1 charges to the set value and transistor T1
When becomes conductive, the single junction transistor T2 is cut off, and therefore the short circuit S3 is cut off.

As a result, the ignition capacitor C4 charges via the normally closed contact CR3, the diode D6 and the resistor R4°R1.

In this state, the trigger of the welding gun, that is, the trigger switch G
When S is closed, relay CR is energized and its normally closed contact C
R3 is open and normally open contact CR4 is closed.

Therefore, the charge in capacitor C4 is transferred to contact CR4 and resistor R.
9 and the diode Dll.

As a result, switching element S2 is turned on and discharges the charge on capacitor C1.

In this way, the welding operation is performed and the initial state is returned.

As mentioned above, even if the trigger switch GS is closed while the capacitor C1 is being charged, the relay CR will not be energized, but if the trigger switch GS is kept closed and the scheduled time elapses, that is, when the capacitor C1 is charged to the set value, the relay CR will not be energized. The CR begins to energize so that a welding operation can occur as previously described.

On the other hand, even if the trigger switch GS is closed while the capacitor C1 is being charged, the relay CR is not energized, so the normally closed contact CR
2 remains closed, the solenoid coil GC of the welding gun is kept energized, and the stud loaded in the welding gun is not fired.

Also, while the capacitor C1 is discharging, its charging circuit is connected to the relay C1.
By opening the normally closed contact CRI of R, switching element S1
It is definitely cut off by the cutoff.

As explained above, in the device according to the present invention,
The switching element of the charging/discharging circuit of the capacitor that stores welding energy is controlled according to the state of charge of the capacitor, and the capacitor is maintained in the charged state regardless of the operation of the welding gun before charging the set value of the capacitor. This structure prevents the capacitor from discharging and welding the stud even if the welding gun is triggered before the capacitor's charge reaches a predetermined value, and also prevents the capacitor from stopping charging. be able to.

Therefore, there is no loss in the charging time of the capacitor, and no matter when the trigger of the welding gun is pulled, the welding operation is reliably performed after the capacitor has been charged to the set voltage.

As a result, there is no need to check the state of charge of the capacitor every time you operate the welding gun, making operation even easier.
Work efficiency can be significantly improved.

[Brief explanation of the drawing]

The accompanying drawings are circuit diagrams showing one embodiment of the present invention. In the figure, BM...Base metal, S...Stud, C1...Capacitor that stores welding energy,
T1...Transistor, T2...Oscillation circuit, S1-S3...Switching element, CR
...Relay, CRI to CR4...Relay contacts.

Claims (1)

[Claims] 1. A capacitor that stores electric charge for welding a stud to a base material using a welding gun, a switching element inserted in the discharge circuit of this capacitor, and a trigger signal from the welding gun after the capacitor is charged to a set value. a circuit for providing an ignition signal to the switching element in response to;
A control circuit device for a manual capacitor discharge type stud welding machine, comprising a circuit that maintains the capacitor in a charging state regardless of activation of a trigger switch of a welding gun while the capacitor is being charged.