JPS6245024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a pulsed arc welding machine that periodically supplies pulsed current to a consumable electrode wire.

[Conventional technology]

In general, pulsed arc welding involves welding by passing a low-output base current between the electrode and the base metal, and superimposing a pulsed current on the base current at an arbitrary period. Due to the pinch force, the molten metal of the fed wire turns into small particles in the form of a spray and separates from the tip at high speed, which has the advantage of less spatter.

The conventional pulse arc welding machine is constructed as shown in FIG.
The output is rectified by a base current supply rectifier 3 and current limited by a current limiting resistor 4, and a constant level base current is passed through two DC reactors 5 and 6 for smoothing to the electrode wire 8 of the wire feeding device 7.
On the other hand, the AC power supply 1 is converted by a pulse current supply transformer 9 and then rectified by a pulse current supply control rectifier 10 to periodically form a pulse current. It is supplied to the connection points 5 and 6 and the base material 11.

Note that, as shown in FIG. 2, the control rectifier 10 is normally used by limiting the conduction angle to 90 degrees or less in order to supply a pulse current with a high current rise and a high peak value.

Then, during the period when the pulse current is not superimposed, the arc is maintained by the base current, and during the superimposition period, the droplet is separated from the tip of the wire 8 of the consumable electrode by the pinch effect based on the pulse current, and the base material 11 is welded.

[Problem that the invention seeks to solve]

By the way, in the case of the conventional pulse arc welding machine shown in FIG. 1, a pulse current is generated only by controlling the phase of the commercial frequency AC power source 1.
The peak value of the pulse current formed by the conduction angle of the control rectifier 10 changes greatly depending on power fluctuations, conduction angle settings, etc., and the pulse current does not have constant current or constant voltage characteristics, so the spray effect changes. uniform welding results cannot be obtained.

When the pulse current is below the critical current value, the conduction angle becomes very small, and the droplets form a large lump larger than the diameter of the wire 8 and irregularly transfer to the arc, and the pulse current exceeds the critical current value. In this case, the droplets become fine and a relatively stable spray transfer is possible, but if the conduction angle is set to 90 degrees or more to increase the pulse current even more, the heat input to the base material 11 will be excessive. In particular, when the base material 11 is a thin plate, burn-through occurs.

Furthermore, when welding a narrow groove, if high arc welding is performed, the arc will spread too much and the molten metal will not transfer smoothly to the base metal 11, and the shielding state by the shielding gas will deteriorate. Welding defects are more likely to occur.

The usable conduction angle of the phase controller 10 is
It is limited to about 60 to 90 degrees, which makes it difficult to adjust the current or voltage over a wide range, and limits the loads that can be welded.

Furthermore, since a single phase is used to supply the pulse current and a 3-phase is used to supply the base current, an unbalance occurs in the input current, which may cause other equipment connected to the input power supply to malfunction. Furthermore, a circuit for base current and a circuit for pulse current are required, making it complicated and expensive, and making it difficult to reduce the size and weight of the power supply.

[Means for solving problems]

This invention has been made with the above points in mind, and includes a rectifier that rectifies alternating current, a switching circuit that switches the output of the rectifier and outputs it intermittently, and a circuit that smoothes the output from the switching circuit. A DC reactor that supplies the load, a flywheel diode that regenerates the stored energy of the DC reactor to the load, and a large current in which a base current and a pulse current are superimposed are alternately supplied to the load by controlling the driving of the switching circuit. A pulse arc welding machine is equipped with a detector for detecting load current or load voltage, and a base current supply command power supply that outputs a first reference signal at a constant level for the base current supply command. , a second command for supplying a trapezoidal or triangular wave pulse current during a preset pulse current superimposition period.
a pulse current supply command power supply that outputs a reference signal of the peak level; and a comparison amplifier that outputs a signal of a level difference between the sum signal of the two reference signals and the detection signal of the detector; oscillation means for generating a high-frequency reinforcement oscillation signal whose output level is set higher than the output level of the amplifier; and pulse width modulation of the oscillation signal by the output signal of the amplifier, so that the oscillation signal is the output signal of the amplifier. A pulse arc welding machine is provided with a modulating means for outputting a modulated pulse having a pulse width set to a period in which the level is lower as a drive control signal for the switching circuit.

[Effect]

Therefore, based on the high frequency switching of the switching circuit, a base current and a pulse current are formed in one circuit, and at this time, the level difference between the sum signal of the first and second reference signals and the detection signal of the detector is Based on the signal, the current supplied to the load during the base current period and the pulse current superimposition period is negative feedback controlled to have constant current characteristics or constant voltage characteristics, and is stabilized.
Moreover, the current value or voltage value of the base current period can be arbitrarily set depending on the level of the first reference signal, and the pulse current value can be arbitrarily set depending on the period and level of the trapezoidal wave or triangular wave of the second reference signal. Since the superimposition period and the current value or voltage value during the period are arbitrarily set, current or voltage adjustment can be performed over a wide range.

Furthermore, the second reference signal becomes a trapezoidal wave or a triangular wave during the pulse current superimposition period, and the second reference signal becomes a trapezoidal wave or a triangular wave during the pulse current superimposition period. Based on the slope of the reference signal, the current or voltage supplied to the load changes relatively slowly, and the arc rises and falls slowly, reducing arc noise.

〔Example〕

Next, this invention will be explained in detail with reference to the drawings from FIG. 3 showing one embodiment thereof.

Figure 3 shows the case of controlling to constant current characteristics, 3
The voltage of the phase AC power source 1 is stepped down by a welding converter 12, and the stepped down voltage is rectified by a rectifier 13, smoothed by a smoothing capacitor 14, and then is switched by high frequency switching of a switching circuit 15 using switching elements such as transistors. , converts the output DC of the capacitor 14 into a pulsed high frequency output of 200Hz to 2KHz, and supplies it to the electrode wire 8 of the wire feeding device 7 via the DC reactor 16,
A low base current and a large current with a superimposed pulse current are periodically and alternately supplied to the arc load.

By the way, the pulse width is 200Hz depending on the input signal.
When the ON control signal shown in FIG.
5, an ion pulse current _J1 shown in FIG. 4C flows, and at this time, energy of L ^di /dt is accumulated in the DC reactor 16 and the wiring inductance.

Then, when the control signal is turned off by the drive device 17, the switching circuit 15 is turned off, and the energy stored in the reactor 16 etc. is transferred to the wire 8, the base material 1
1. An off-pulse current I ₂ is released through the flywheel diode 18 and shown in FIG. 4d flows through the flywheel diode 18.

Therefore, by turning on and off the drive device 17,
A smoothed current I ₀ shown in FIG. 4a flows through the load.

On the other hand, a current detector ₁₉ that detects the DC output current of a current shunt or DC current transformer, etc.
is detected, and a detection signal Ed proportional to the smoothed current I ₀ is output to the comparison amplifier 20.

The comparator amplifier 20 receives a constant level base current supply command signal from the base current supply command power supply 23.
The addition signal of Eb and the pulse current supply command signal Ep of the pulse current supply command power source 24 is compared and amplified with the detection signal Ed, and an output signal V having a level of Eb+Ep-Ed is output to the drive device 17.

By the way, the command power supply 23 is composed of a variable DC power supply, and outputs a command signal Eb at a level that is operationally set as a base current value as a first reference signal.

The command power source 24 also includes a variable DC power source 25 , a voltage-frequency converter 26 , a monostable multivibrator 27 , and a waveform shaper 28 . In addition to converting the frequency signal into a frequency signal with a frequency corresponding to the voltage, the monostable multivibrator 27 converts the frequency signal into a rectangular wave, and the waveform shaper 28 integrates the rectangular wave signal into a trapezoidal wave or triangular wave. A command signal that is shaped into a waveform and becomes a trapezoidal or triangular wave only during the pulse current superimposition period.
Ep is output as the second reference signal.

Note that the period of superimposition of the pulse current is, for example, 1/
It is set to a period of 10 seconds to 1/10 ³ seconds.

Therefore, based on the conversion range of the converter 26 and the time constant settings of the multivibrator 27,
The frequency of the aforementioned frequency signal and square wave signal is 10Hz
It is set to ~1KHz.

In addition, a multivibrator 27, a waveform shaper 2
8 is constructed as shown in FIG. 7, in which 27' is a monostable multivibrator integrated circuit, a frequency signal is input to the trigger terminal i,
A time constant is set by an external time constant resistor R1 and capacitor C1, and a rectangular wave signal is output from the output terminal q. 28' is an operational amplifier that forms an integrating circuit together with an integrating resistor R2 and a capacitor C2, which integrates a rectangular wave signal and outputs a command signal Ep at a level set as a pulse current value.

Then, the comparator amplifier 20 outputs the command signal Eb.
and the command signal Ep are added, and at this time, since the command signal Ep becomes 0 during the base current period, the added signal formed by the addition is equal to the base current setting level of the command signal Eb during the base current period. As the pulse current superimposes, the command signal Ep
The superimposed current setting level is obtained by adding the level of the command signal Eb to the level of the command signal Eb, and changes as shown by the thick solid line in FIG. 4e, for example.

Furthermore, by subtracting the detection signal Ed from the addition signal of the command signals Eb and Ep, the comparator amplifier 2
The output signal V of 0 changes in proportion to the difference between the base current value and superimposed current value set by the addition signal and the current value being supplied.

Further, a drive circuit 17 to which the output signal V is input.
consists of an oscillation comparator 21 and an amplifier 22, as shown in FIG.

By the way, as shown in FIG. 8, the oscillation comparator 21 includes UJTQ1, transistor Q2, and oscillation resistors R3, R4, R5, R6, R7, R8, R
9. Oscillator 21' consisting of capacitor C3
and a comparator 21'' for comparing the sawtooth waveform oscillation signal of the oscillator 21' and the output signal V.

In order to perform high frequency switching of the switching circuit 15, the oscillation frequency of the oscillator 21' is set to 200.
The extended oscillation signal shown by the solid line in FIG. 6a, whose peak level is set to be higher than the output signal V, is output from the oscillator 21' to the comparator 21'', which is set at a high frequency of Hz to 2 KHz.

Further, the comparator 21'' compares the constant oscillation signal and the output signal V, performs pulse width modulation with the constant oscillation signal, and sets the pulse width to a period during which the constant oscillation signal is at a lower level than the output signal V. The modulated pulse is outputted to the switching circuit 15 via the amplifier 22 as a drive control signal.

For example, when the level of the output signal V is the level indicated by the broken line in FIG. 6a, the comparator 21'' outputs a modulated pulse having the pulse width shown in FIG. 6b.

Furthermore, based on the setting of the output level of the comparator amplifier 20, the addition signal of the command signals Eb and Ep and the detection signal
When the level difference of Ed is 0, the level of the output signal V is approximately 1/2 the level of the tensile oscillation signal.

Therefore, the output signal of the drive device 17 becomes the high-frequency drive control signal shown in FIG. 4b, whose pulse width changes in proportion to the level difference between the addition signal of the command signals Eb and Ep and the detection signal Ed.

Then, the output of the drive device 17 is set so that the level of the addition signal of the command signals Eb and Ep changes between the base current period and the superimposition period of the base current and pulse current, and the level of the detection signal Ed becomes the level of the addition signal. Since the switching of the switching circuit 15 is controlled based on the signal, the current supplied to the arc load is equal to or equal to the base current at the level set by the command signal Eb at the cycle set by the command signal Ep. , so that the superimposed current at the level set by the command signals Eb and Ep, that is, the superimposed current of the base current and the pulse current, alternately changes.
Negative feedback control is performed, and at this time, due to negative feedback control,
The current supplied to the arc load is controlled to be a base current and a superimposed current, respectively.

Furthermore, based on the slopes of the front and trailing edges of the trapezoidal or triangular wave of the command signal Ep, the output signal V changes relatively slowly, and for this reason,
The current supplied to the arc load changes relatively slowly, reducing arc noise.

Therefore, in the case of the above embodiment, the command signal Ep, which becomes a trapezoidal wave or a triangular wave only during the superimposition period of the pulse current, is added to the constant level command signal Eb, and the command signal Ep is detected as a sum signal of the command signals Eb and Ep. By controlling the switching operation of the switching circuit 15 based on the comparison of the level difference with the signal Ed, and alternately supplying a low base current and a large current with a superimposed pulse current to the arc load, one circuit A superimposed current of a base current and a pulse current can be supplied by using a welding machine, which makes the welding machine simpler, cheaper, and lighter.Furthermore, since only three-phase input is used, problems such as input imbalance can be avoided. will not occur.

In addition, instead of the phase control of the conventional controlled rectifier, the current supplied to the arc negative is controlled by high frequency switching of the switching circuit 15, and the base current is controlled by constant current control by so-called negative feedback control. The current during this period and the pulse current superimposition period is controlled to have constant current characteristics, allowing stable and uniform welding to be performed and improving power supply efficiency.

Then, set the level of command signal Eb,
Base current and pulse current can be arbitrarily set variably over a wide range based on the period and level settings of the Ep trapezoidal or triangular wave.
Current can be adjusted over a wide range, allowing welding with various loads.

Furthermore, by changing the trapezoidal wave or the triangular wave of the command signal Ep, it is possible to reduce arc noise when the base current changes to a large current on which a pulse current is superimposed, and when the large current changes to the base current.

Note that although the above embodiment is a case of operation with constant current characteristics, it is also possible to detect the output voltage and perform operation with constant voltage characteristics.

Further, although the above embodiments are based on a three-phase AC power source, similar effects can be obtained even when a single-phase AC power source is used.

〔Effect of the invention〕

As described above, according to the pulse arc welding machine of the present invention, the pulse of the drive control signal output from the drive device to the switching circuit is based on the level difference between the addition signal of the first and second reference signals and the detection signal. By controlling the operation of the switching circuit by varying the width and alternately supplying a high current with a low base current and a pulse current superimposed to the load, it can be formed using one circuit, and welding In addition to simplifying the machine, reducing its price and weight, there are no problems such as unbalanced power supply input, and the power supply is more efficient than when controlling the current supplied to the load using phase control. etc. will improve.

Further, since the current supplied to the load is controlled to have constant current characteristics or constant voltage characteristics by load feedback control, stable and uniform welding can be performed and welding performance is improved.

Furthermore, based on the adjustment of the first and second reference signals, the current value or voltage value of the base current period and the pulse current superimposition period, as well as the pulse current superimposition period, can be variably set over a wide range. Alternatively, it is possible to perform welding under various loads by adjusting the voltage.

Furthermore, based on the slope of the trapezoidal wave or triangular wave of the second reference signal, the output current or output voltage at the time of transition from the base current to a large current with a superimposed pulse current, and from the large current to the base current. It is also possible to make the change relatively gentle and reduce arc noise.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a conventional pulse arc welding machine.
2 is a current waveform diagram of FIG. 1, FIG. 3 is a wiring diagram of one embodiment of the pulse arc welding machine of the present invention, and FIG.
Figures a, b, c, d, and e are waveform diagrams of each part in Figure 3,
FIG. 5 is a block wiring diagram of the drive device shown in FIG. 3, and FIGS. 6a and 6b are waveform diagrams for explaining the operation of FIG. FIGS. 7 and 8 are detailed wiring diagrams of parts of FIGS. 3 and 5, respectively. DESCRIPTION OF SYMBOLS 1... AC power supply, 13... Rectifier, 15... Switching circuit, 16... Reactor, 17... Drive device,
18...Flywheel diode, 19...Current detector, 20...Comparative amplifier, 23...Base current supply command power supply, 24...Pulse current supply command power supply.

Claims (1)

[Scope of Claims] 1. A rectifier that rectifies alternating current, a switching circuit that switches the output of the rectifier and outputs it intermittently, a DC reactor that smoothes the output from the switching circuit and supplies it to a load, and A flywheel diode that regenerates the energy stored in the reactor to the load, and a drive device that controls the driving of the switching circuit to alternately supply the load with a large current in which a base current and a pulse current are superimposed. In a pulse arc welding machine, a detector that detects load current or load voltage,
A base current supply command power supply that outputs a first reference signal at a constant level for a base current supply command, and a second reference signal for a trapezoidal or triangular wave pulse current supply command during a preset pulse current superimposition period. a pulse current supply command power supply that outputs a pulse current supply command power source, and a comparison amplifier that outputs a signal representing a level difference between a sum signal of the two reference signals and a detection signal of the detector; oscillation means for generating a high frequency tension oscillation signal set higher than the output level of the
The oscillation signal is pulse width modulated by the output signal of the amplifier, and a modulation pulse whose pulse width is set to a period during which the oscillation signal is at a lower level than the output signal of the amplifier is used as a drive control signal for the switching circuit. A pulse arc welding machine characterized by being equipped with a modulation means for outputting.