JPS5855865B2 - Control circuit device for 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 accumulated in a capacitor from an AC power source through a power transformer and a rectifier, and this is discharged directly or via a welding transformer to the stud weld, and the charging voltage control of the capacitor and the turning on and off of the discharge circuit are performed using SCR etc. Various stud welding machines have been proposed that are configured to perform welding operations using switching elements such that even if the welding gun is triggered before the capacitor's charge reaches a predetermined value, the capacitor will discharge. In addition, the charging circuit is configured to be cut off as soon as the charging of the capacitor reaches a predetermined value.

However, in such conventional stud welding machines, even if the welding gun is triggered before the capacitor has charged to a predetermined value, the capacitor will not discharge, but the stud loaded in the welding gun will erupt.

Therefore, operating the welding gun before charging the capacitor to the set value results in loss of the stud itself, resulting in a significant reduction in work efficiency.

An object of the present invention is to charge the capacitor in the capacitor discharge type stud welding machine of the above type in order to prevent the stud loaded in the welding gun from being discharged due to the operation of the welding gun before charging the capacitor to a set value. The second objective is to provide a circuit that maintains a solenoid coil for pulling up a stud loaded in a welding gun in an energized state regardless of the operation of a trigger switch of the welding gun.

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

The drawing shows an embodiment of the present invention, where A and B are power terminals, ST is a power transformer, SW is a power switch, and D1 to D1.
2 is a diode, R1-R13 are resistors, VRl, VH2
is a variable resistor, CI, C5 is a capacitor, 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 terminals of the rectifier bridge consisting of diodes D1-D4 are connected to the secondary side of the power transformer ST via a power switch SW.

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

Further, a series circuit consisting of variable resistors VR1, 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 VH2.

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 a variable resistor R1, 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 terminal of the rectifier bridge and the switching element S1 of the charging circuit.

Single junction transistor T2 is silicon controlled rectifier 81,8
3 constitutes a trigger oscillation circuit, the emitter of which is connected to the collector circuit of the transistor T1 through 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 charging through the resistors R5 and 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 second pulse transformer PT 111 is connected on the one hand to the gate terminal of the switching element S1 of the charging circuit via a normally closed contact CR1 of a relay CR, and on the other hand to the gate terminal of the switching element S3 via a resistor R8. Ru.

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 comprised of millicon controlled rectifiers in the illustrated embodiment, they may alternatively be comprised of GTO silices 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 above series circuit of the trigger switch GS and the relay CR and the switching element S3, and the series circuit consisting of the normally closed contact CR3 of the relay CR and the capacitor C4 is inserted in parallel. The connection point between contact CR3 and capacitor C4 is connected via the normally open contact CR4 of relay CR, resistor R9 and diode D11 to the gate terminal of switching element S2 of the discharge circuit of capacitor C1.

In the illustrated embodiment, the solenoid coil GC of the welding gun is the normally closed contact CR2 of the relay CR.

The output terminal of the rectifier bridge and the switching element S of the charging circuit via resistor R2, diode D5 and resistor R1
1.

The operation of the apparatus of the present invention configured as described above will be explained 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 VH2 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 voltage regulator diode Z3 to charge the capacitor C3.

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

As a result, a pulse signal is generated on the secondary side of the pulse transformer PT, which pulse signal is supplied via the resistor R7, the diode D9 and the normally closed contact CR1 to the gate terminal of the switching element S1 of the charging circuit, which Fire element S1.

The capacitor C1 then begins to charge.

As the charging voltage of capacitor C1 increases, resistor R11,
The voltages of variable resistors VR1, VH2 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 the variable resistor VRIVR2, and this set voltage is controlled only by the charging voltage of the capacitor C1.

On the other hand, when the single junction 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 forms a short circuit and makes this switching element 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 connected to the ignition capacitor C4 of the switching element S2 of the discharge circuit, and the trigger of the welding gun is activated. Switch GS and relay CR are substantially electrically disconnected.

Therefore, while charging the capacitor C1, the trigger switch GS
Even if it is inserted, relay CR does not operate and there is no effect on the charging/discharging circuit of 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 resistors R4, R1.

In this state, the trigger of the welding gun, that is, the trigger switch O
8, 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 D11.

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

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

As mentioned above, relay CR is not energized even if trigger switch O8 is closed while capacitor C1 is being charged.
The normally closed contact CR2 remains closed, the solenoid coil O8 of the welding gun is maintained in an energized state, 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 CR1 of R, the switching element S1
It is definitely cut off by the cutoff.

As described above, the device according to the present invention is configured to prevent studs loaded in the welding gun from being ejected due to activation of the welding gun before charging the capacitor to the set value, so that studs are not wasted. It is economical and also helps improve work efficiency.

[Brief explanation of the drawing]

The accompanying drawings are circuit diagrams showing one embodiment of the present invention. In the figure, BM is the base material, S is the stud, C1 is the capacitor that stores welding energy, T1 is the transistor, T2 is the oscillation circuit, 81 to S3 are the switching elements, and CR is the relay.
CR1 to CR4 are 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 into the discharge circuit of this capacitor, and a trigger signal from the welding gun after the capacitor has been charged to a set value. a circuit for supplying an ignition signal to said switching element in response to said capacitor; and a circuit for holding a solenoid coil which pulls up a stud loaded in a welding gun in an energized state regardless of activation of a trigger switch of said welding gun while said capacitor is being charged. A control circuit device for a capacitor discharge type stand welding machine, characterized in that: