JPH0413060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a high-frequency pulse arc welding machine suitable for use in AC welding of thin plates and the like.

"Prior Art" FIG. 3 is a circuit diagram showing the configuration of a conventional welding power source. In the figure, 1 is a DC power source (voltage E) such as a battery. INV is an inverter that converts the DC output of the DC power supply 1 into AC and outputs it,
It is composed of switching elements 2-5 and diodes 6-9. A current detector 10, a workpiece 11, an arc 12, an electrode 13, a coupling coil 14, and a reactor 15 are arranged in series between the output ends of the inverter INV. 17 is a control circuit that performs on/off control of the switching elements 2 to 5 based on the detected current of the current detector 10, and also controls the drive of the high frequency high voltage generator 16.
constitutes an arc starter together with the coupling coil 14. Further, 18 is a command/operation unit, which instructs the control circuit 17 about a target value of welding current, etc.

FIG. 4 is a waveform diagram showing the relationship between the on/off timing of switching elements 2 to 5 and welding current Iw of the conventional welding power source having the above configuration. In this figure, the hatched portion indicates the on period of each switching element 2-5. Then, when the control circuit 17 gives a drive command to the high frequency high pressure generator 16 to generate high pressure, the material to be welded 11
Arc discharge is started between the electrode 13 and the welding current Iw as shown in FIG. 4A when switching control is performed as shown in FIG. That is, during the period in which switching elements 2 and 5 are both on, which is indicated by T1 in the same figure, the following changes occur: DC power supply 1 → switching element 2 → workpiece 11 → arc 12 → electrode 13 → coupling coil 14 →
Welding current Iw flows through the path of reactor 15 → switching element 5 → DC power supply 1 (hereinafter, this period is referred to as power supply period T1), and switching element 5 is turned off and only switching element 2 is turned on, as shown by T2 in the figure. During the period, the energy stored in the reactor 15 causes the reactor 15 → diode 8 → switching element 2 → workpiece 11 →
Arc 12 → Electrode 13 → Coupling coil 14
→The welding current Iw circulates in the path of the reactor 15 (hereinafter, this period is referred to as a circulation period T2).

"Problems to be Solved by the Invention" By the way, in DC welding, it is known that when a high frequency pulse current is superimposed on the welding current, the electromagnetic pinch effect increases and the stability of the arc is improved. The electromagnetic pinch effect is a property in which the diameter of the arc is narrowed under the influence of the magnetic field generated by the arc current, and is a desirable property for stabilizing the arc. Therefore,
The method of superimposing high-frequency pulsed currents is effective for welding thin plates, which require low current welding and where the arc is likely to become unstable.

On the other hand, in the case of materials that are easily oxidized, such as aluminum, reverse polarity welding or AC welding, which has a cleaning effect to remove the oxide film, is often applied.

However, in the case of an AC welding power source, when welding thin materials, the average value of the welding current must be lowered, which has the disadvantage that the arc becomes unstable. Therefore, it is conceivable to superimpose high-frequency pulses as in the case of a DC welding power source.
In order to superimpose high-frequency pulses, it is sufficient to increase the frequency of the oscillator in the control circuit 17 that determines the AC periods T and T', but in the conventional AC welding power source shown in FIG. 15, the ripple component of the welding current Iw is removed as shown in FIG. 4A, making it difficult to superimpose high frequency components. In particular, in order to eliminate the adverse auditory effects associated with the superimposition of high-frequency components, setting the high-frequency components to 15 kHz or higher (frequencies outside the audible range) is affected by the reactor 15 (including wiring stray inductance) and has almost no effect. It was possible.

Therefore, if the reactor 15 is removed or its value is reduced and the pair of switching elements 2 and 5 or 4 and 3 are turned on and off simultaneously, di/
The value of dt becomes almost the same as that at the time of rise (the sign is opposite), and as a result, it becomes possible to superimpose high frequency components as shown by the solid line in FIG. Note that due to the influence of the reactor 15 and wiring stray inductance, the waveform of the welding current Iw cannot be made into a perfect rectangular wave, but becomes a triangular wave as shown in the figure. However, if the current peak value is large, It can be effective.

However, if the reactor 15 is set to a small value in this way, the smoothing effect disappears, so when the average value of the welding current Iw is small, that is, when the ON time of the switching elements 2 to 5 is short, the dotted line shown in FIG. As shown in the figure, there was a section where the welding current Iw was 0, which caused the problem of arc breakage.

This invention was made in view of the above-mentioned circumstances, and it is possible to superimpose a high-frequency pulse current on the welding current in an AC welding power source, and even when the average value of the welding current is set to a small value, arc breakage occurs. The purpose of the present invention is to provide a high frequency pulse arc welding machine that does not cause any damage.

"Means for Solving the Problem" The present invention connects first and second switching elements that are turned on and off in a complementary manner in series to a first DC power supply, and also turns on and off in a complementary manner. a first inverter configured by sequentially connecting third and fourth switching elements in series with the first DC power source, and further connecting diodes in reverse series to each of the switching elements; Fifth and sixth switching elements that are turned on and off in a complementary manner are connected in series to the second DC power supply, and seventh and eighth switching elements that are turned on and off in a complementary manner are connected to the second DC power supply. a second inverter configured by connecting diodes in reverse series to each of the switching elements; and a second inverter configured by connecting diodes in reverse series to each of the switching elements; an oscillator that outputs a high-frequency signal, a first comparator that compares the absolute value of the welding current with a preset first value, and a first comparator that compares the absolute value of the welding current with a preset first value. a second comparator that compares the second value with the second value, and turns on the second and third switching elements or the first and fourth switching elements in accordance with the period of the high frequency signal; All switching elements of the first inverter are turned off based on the output signal of the first comparator, and any switching element of the second inverter is turned on based on the output signal of the second comparator. It is characterized by comprising a control means for performing a series of operations.

"Effect" Welding current during power supply period and regeneration period
The value of di/dt can be made large, therefore,
The high-frequency component can be superimposed well, and the control means turns on the second and third switching elements or the first and fourth switching elements in accordance with the period of the high-frequency signal, so that the output signal of the first comparator A series of operations is performed in which all the switching elements of the first inverter are turned off based on the output signal of the second inverter, and one of the switching elements of the second inverter is turned on based on the output signal of the second comparator. The current never becomes 0, and arc breakage is prevented.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and parts corresponding to those in FIG. 3 described above are given the same reference numerals.

In Figure 1, 1a and 1b, 2a to 5a and 2
b-5b, 6a-9a and 6b-9b and 15a
and 15b correspond to the DC power supply 1, switching elements 2 to 5, diodes 6 to 9, and reactor 15 shown in FIG. A second inverter INVb is constructed by switching elements 2b to 5b and diodes 6b to 9b.

17A are switching elements 2a to 5a and 2b to
5b and the high frequency/high pressure generator 16, and is a control circuit that controls the setting values of each setting device _18A1 to _18A5 in the command/operation section 18A and the current detector 10.
Turn on/off each switching element based on the detected value of
It is now possible to perform off control. In this case, the control system of the high frequency high voltage generator 16 in the control circuit 17A is the same as the control circuit 17 shown in FIG. 3, so illustration and explanation thereof will be omitted, and only the control system of the switching element will be described below. .

First, the welding current Iw is in the positive direction (material to be welded 11→
When the welding current Iw is flowing from the arc 12 to the electrode 13 (hereinafter referred to as the SP period), the detected current (hereinafter referred to as the feedback signal Fs) corresponding to the welding current Iw output from the current detector 10 is transmitted to the analog switch 27. are supplied to deviation detection points 29, 31, 39 and 40, respectively.

Conversely, when the welding current Iw is flowing in the negative direction (electrode 13 → arc 12 → welded material 11) (hereinafter referred to as the RP period), the feedback signal Fs output from the electrode detector 10 has a gain of - After being inverted by an inverter 26 constituted by one amplifier, the signals are supplied to deviation detection points 29, 31, 39 and 40 via an analog switch 28, respectively.

The setting device 18A ₁ is for setting the welding current average value Iav, and the deviation detection point 29 is for setting the welding current average value Iav.
This is to detect the deviation between the welding current average value Iav output from _A1 and the feedback signal Fs (corresponding to the welding current Iw). This deviation detection point 2
The deviation obtained at 9 is integrated by an integrator 30. 31 is an integral output signal of the integrator 30;
This is a deviation detection point that detects the deviation from the instantaneous value of the feedback signal Fs.
The magnitude relationship with the instantaneous value of is compared.

19 is a pulse oscillator that generates a 15kHz rectangular wave, and this output pulse is supplied to the trigger terminal of the one-shot multivibrator 34, and one input terminal of the negative logic OR gate 33;
It is applied to the clock input CK of the D-type flip-flop 21.

The output pulse of the one-shot multivibrator 33 is supplied to the set terminal S of the set-reset flip-flop 35, and the output of the negative logic OR gate 33 is supplied to the reset terminal R of the set-reset flip-flop 35. . The reset flip-flop 35 is set each time the output of the oscillator 19 goes to the "H" level, and then, during the period when the output of the oscillator 19 is at the "L" level, the welding current Iw is set.
When the peak value Ip (corresponding to the welding current average value Iav set by the setting device _18A1 ) shown in FIG. be done.

Set/Reset/Flip Flop 35 Q
The output is AND gate 37 and AND gate 38
supplied to The AND gate 37 and the AND gate 38 respectively turn on/off the pair of switching elements 2a and 5a and the pair of switching elements 3a and 4a that constitute the first inverter INVa. As a result, during the period when the Q output of the reset flip-flop 35 is at the "H" level, the AND gate 37 or the AND gate 38 is in an open state, and the AND gate 38 is in an open state.
7 or the other input terminal of the AND gate 38, the switching element 2
a, 5a pair or switching elements 3a, 4
Pair a is turned on.

Then, the welding current Iw is at the peak value shown in Figure 2.
Before reaching Ip, the output of the comparator 32 is at "H" level, and the set/reset signal is
Flip-flop 35 remains set, so AND gates 37 and 38 are open. Here, when the pair of switches 2a and 5a is turned on via the AND gate 37, the second
During the power supply period _T1 shown in the figure, when the positive side main pulse +MP is generated and the pair of switching elements 3a and 4a is turned on via the AND gate 38, the negative side main pulse +MP is generated during the power supply period _T1 shown in the figure. Main pulse - MP is generated.

Also, the output pulse of the pulse oscillator 19 is “L”
level, and when the welding current Iw reaches the peak value Ip shown in FIG. Therefore, the switching elements 2a to 5a are all turned off, resulting in a regeneration period _T3 shown in FIG. 2.

As can be seen from the above explanation, the pulse oscillator 1
The frequency of main pulse ±MP is defined by the frequency of 9, and furthermore, the frequency of main pulse ±
The peak value ±Ip of MP is always maintained at the welding current average value Iav set by the setting device _18A1 .

On the other hand, the output pulse of the pulse oscillator 20 is supplied to the D input terminal of the D type flip-flop 21. The pulse oscillator 20 has an oscillation frequency set by the setting device _18A2 (usually about 1kHz or less)
It is configured to oscillate according to the duty ratio set by the setter _18A3 .

These pulse oscillator 20 and D-type flip-flop 21 are used to define the SP period, which is the positive half cycle, and the RP period, which is the negative half cycle, of the welding current Iw, as shown in FIG. . That is, the D type flip-flop 21
The Q output of is switched when the output of the pulse oscillator 19 supplied to the clock input terminal CK rises to the "H" level. ), the Q of the D type flip-flop 21 is
The output becomes "H" level.

When the Q output of the D-type flip-flop 21 becomes "H" level, the AND gate 37 and the AND gate 45 become open, and as a result,
Depending on the signals supplied to the other input terminals of AND gates 37 and 45, the first inverter
Switching elements 2a, 5a forming INVa,
And the switching element 5b constituting the second inverter INVb is turned on.

On the other hand, during the period in which the output of the pulse oscillator 20 is at the "L" level (RP period), the Q output of the D-type flip-flop 21 is at the "L" level, thereby opening the AND gates 38 and 46. , switching elements 3a and 4a constituting the first inverter INVa and the second inverter INVa according to signals supplied to other input terminals of the AND gates 38 and 46.
Switching element 4b constituting INVb is turned on.

The Q output of the D-type flip-flop 21 is supplied to an analog switch 27 and also to an analog switch 28 via an inverter 28a, whereby each deviation detection point 29, 31,
Feedback signal Fs supplied to 39 and 40
The polarity of is always maintained on the positive side during both the SP period and the RP period.

Next, the setting device 18A ₄ is for setting the base welding current lower limit value IB ₁ shown in FIG. 2, and the setting device 18A ₅ is for setting the base welding current upper limit value IB ₂
This is for setting. These setting devices 18
Each setting value of A ₄ and 18A ₅ is determined by the deviation detection point 39.
and 40 to provide feedback signal Fs
(corresponding to welding current Iw) is detected. The deviations obtained at these deviation detection points 39 and 40 are input to comparators 41 and 42 and compared in magnitude. In this case, welding current
When Iw becomes smaller than the base welding current lower limit value IB ₁ , the output of the comparator 41 becomes "H" level, and the welding current Iw becomes the base welding current upper limit value.
When it becomes larger than IB ₂ , the output of the comparator 42 becomes "L" level. These comparators 4
The outputs 1 and 42 are supplied to the set terminal S and the reset terminal R of the set/reset flip-flop 43, so that the set/reset flip-flop 43 controls the welding current Iw to be lower than the base welding current lower limit _IB1. It is set when the base welding current exceeds the upper limit value _IB2 , and is reset when the base welding current exceeds the upper limit value IB2. The Q output of this set/reset flip-flop 43 is connected to the AND gate 4.
5 and 46.

As described above, when the welding current Iw becomes equal to or less than the base current lower limit value ± _IB1 during the regeneration period _T3 after the main pulse ±MP is supplied, the switching element 2 constituting the second inverter INVb
The pair b, 5b or the pair 3b, 4b is turned on, a power supply period T ₁ ' occurs, and then the welding current Iw
When the base current reaches the upper limit value ± _IB2 , only the switching element 2b or 3b is turned on, and a freewheeling period _T2 begins.

In addition, 48 shown in the figure is an inverter, 36, 44
is a timer. The timers 36 and 44 are used to prevent switching elements having opposite polarities from being turned on at the same time when the on/off patterns of the switching elements 2a to 5a and 2b to 5b are switched.

Next, the operation of one embodiment with the above-described configuration will be explained with reference to FIG. 2.

In this embodiment, the SP period in which the welding current Iw flows in the forward direction and the RP period in which the welding current Iw flows in the reverse direction are controlled in exactly the same way, so here,
Only the SP period will be explained.

Now, at time ts, the welding current Iw is below the peak value Ip, and the output of the comparator 32 is at the "H" level. Here, when the output of the pulse oscillator 19 rises to the "H" level, the set/reset flip-flop 35 is set and its Q output becomes the "H" level. Further, when the output of the pulse oscillator 20 becomes "H" level and the Q output of the D type flip-flop 21 becomes "H" level, all the input terminals of the AND gate 37 become "H" level when the timer 36 completes the timing operation. ” level, thereby turning on switching elements 2a and 5a. Then, the welding current Iw changes from DC power supply 1a to switching element 2.
a → reactor 15a → current detector 10 → welded material 11 → arc 12 → electrode 13 → coupling coil 14 → switching element 5a → DC power supply 1a
As a result, the first inverter
The welding power source Iw is supplied by INVa, and the main pulse +MP is generated (power supply period T ₁ ).

Next, at time _t1 , when the welding current Iw reaches the peak value Ip, the output of the comparator 32 is inverted to the "L" level, the set/reset flip-flop 35 is reset, and its Q output becomes the "L" level. to be reversed. Then, the switching elements 2a and 5a are turned off simultaneously, and the welding current Iw is regenerated to the DC power supply 1a via the diodes 7a and 8a, so that the value of the welding current Iw becomes equal to the slope of di/dt during the power supply period _T1. decreases with the same slope (opposite sign) (regeneration period
_T2 ).

Next, at time t ₂ , the welding current Iw changes to the setting device 1.
Base welding current lower limit value set by 8A ₄
When IB decreases to ₁ , the output of the comparator 41 becomes "H" level, the set/reset flip-flop 43 is set, its Q output becomes "H" level, and this "H" level Q output is sent to the AND gate 45. The switching element 5b is turned on. Here, switching element 2b is already turned on based on the Q output of D type flip-flop 21. these,
When switching elements 2b and 5b are both turned on, DC power supply 1b → switching element 2b → reactor 15b → current detector 10 → workpiece 11 →
Arc 12 → Electrode 13 → Coupling coil 14
Welding current Iw flows through the path → switching element 5b → DC power supply 1b, and as a result, welding current Iw is supplied by the second inverter INVb (power supply period T ₁ ').

Next, at time _t3 , when the welding current Iw reaches the base welding current upper limit value _IB2 set by the setting device _18A5 , the output of the comparator 42 becomes "L" level, and the set/reset flip-flop 43 is turned on. is reset, and its Q output is
It becomes "L" level. Then, the switching element 5b is turned off and only the switching element 2b is turned on. As a result, the energy stored in the reactor 15b causes the reactor 15b → current detector 10 → workpiece 11 → arc 12 → electrode 13 → coupling Coil 14 → diode 8b
The welding current Iw flows back through the path of → switching element 2b → reactor 15b (reflux period T ₂ ). In this way, the second inverter INVb is subjected to constant ripple control, and the welding current Iw is set to the base welding current lower limit.
Welding current Iw is supplied when IB ₁ or less, and welding current Iw is circulated when base welding current upper limit IB _{2 or} more is reached. The frequency in this case is determined by the load.

Thereafter, similarly, the power supply period T ₁ and the regeneration period T ₃ by the first inverter INVa, and the power supply period T ₁ ' and the circulation period T ₂ by the second inverter INVb are repeated in sequence.

According to one embodiment described above, the first inverter
The di/dt (slope of main pulse MP) of the welding current Iw supplied from INVa can be increased to enable superimposition of high-frequency pulses, and when the value of the welding current Iw becomes less than the base welding current lower limit value IB ₁ , Since the welding current Iw is supplied from the second inverter INVb, it is possible to avoid a situation where the welding current Iw becomes zero.

Although one current detector 10 is provided in the embodiment described above, a pair of current detectors 1 is provided.
0 may be provided in the same way as the reactors 15a and 15b, and the second inverter INVb may be configured to always perform constant current control or constant ripple control to supply the welding current Iw. INVb does not need to be driven in synchronization with the first inverter INVa, and may be driven asynchronously as long as the polarities (SP period and RP period) are the same.

"Effects of the Invention" As explained above, according to the present invention, the first and second switching elements, which are turned on and off in a complementary manner, are sequentially connected in series to the first DC power supply, and a first inverter configured by sequentially connecting third and fourth switching elements to turn on/off in series with the first DC power source, and further connecting a diode in reverse series to each of the switching elements; , the fifth and sixth switching elements which are turned on and off in a complementary manner are sequentially connected in series with the second DC power supply, and the seventh and eighth switching elements which are turned on and off in a complementary manner are connected to the second DC power supply. A second inverter is connected in series to the DC power supply of the inverter, and a second inverter is configured by connecting a diode in reverse series to each of the switching elements, and a second inverter is connected in series to the DC power supply of the inverter. An electrode and a welded material connected in series, an oscillator that outputs a high frequency signal, and a first comparator that compares the absolute value of the welding current with a preset first value;
a second comparator that compares the absolute value of the welding current with a preset second value; 4 switching elements are turned on, all the switching elements of the first inverter are turned off based on the output signal of the first comparator, and the second
Since the control means performs a series of operations to turn on any switching element of the second inverter based on the output signal of the comparator, the di/dt of the welding current during the power supply period and the regeneration period is controlled. The value can be made large, and therefore high frequency components can be superimposed well, and
The control means turns on the second and third switching elements or the first and fourth switching elements in accordance with the period of the high frequency signal, and turns on all of the first inverters based on the output signal of the first comparator. Since a series of operations is performed in which the switching element is turned off and one of the switching elements of the second inverter is turned on based on the output signal of the second comparator, the welding current does not become zero and the arc The effect of being able to prevent cuts is obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a waveform diagram of various parts to explain the operation of the same embodiment, and Fig. 3 is a block diagram showing the configuration of a conventional welding power source. , FIG. 4 is a waveform diagram of various parts of the welding power source, and FIG. 5 is a waveform diagram when high frequency components are superimposed in a conventional welding power source circuit. 1a, 1b...DC power supply, 2a~5a, 2b~
5b...Switching element, 6a-9a, 6b-
9b...diode, INVa...first inverter, INVb...second inverter, 11...material to be welded, 13...electrode, 17A...control circuit.

Claims (1)

[Scope of Claims] 1. First and second switching elements that are turned on and off in a complementary manner are sequentially connected in series to a first DC power supply, and a third switching element that is turned on and off in a complementary manner is connected in series to the first DC power source.
A first inverter configured by sequentially connecting fourth switching elements in series with the first DC power supply and further connecting diodes in reverse series to each of the switching elements, and a first inverter configured to turn on/off in a complementary manner. The fifth and sixth switching elements to be turned on and off are connected sequentially in series to the second DC power supply, and the seventh and eighth switching elements to be turned on and off in a complementary manner are connected in series to the second DC power supply. a second inverter configured by connecting diodes in reverse series to each of the switching elements; and electrodes and electrodes connected in series between both output terminals of the first and second inverters. a material to be welded, an oscillator that outputs a high frequency signal, a first comparator that compares the absolute value of the welding current with a first preset value, and a second comparator that compares the absolute value of the welding current with a preset second value. and a second comparator for comparing the high-frequency signal, the second and third switching elements or the first and fourth switching elements are turned on in accordance with the period of the high-frequency signal, and the first comparator A series of steps in which all the switching elements of the first inverter are turned off based on the output signal of the first inverter, and any switching element of the second inverter is turned on based on the output signal of the second comparator. A high-frequency pulse arc welding machine, comprising: a control means for operating the machine; and a high-frequency pulse arc welding machine.