JPS6138781A - Consumable electrode type pulse arc welding machine - Google Patents

Abstract

PURPOSE:To stabilize a welding arc and to improve operability by decreasing or increasing an arc voltage in accordance with the differential number of times between a set number of short circuits and detected number of short circuits. CONSTITUTION:The waveform of the welding arc voltage is made into a short circuit waveform by a level adjusting circuit for detecting short circuit. The waveform is shaped to a short circuit detecting pulse. The difference nd between the number (n) of the short circuit pulses in sampling time Ts and the preset number ns of pulses is determined. The differential nd pulse is inputted to an up counter when (n-ns)>0 and the differential pulse nd is inputted to a down counter when (ns-n)>0. The output of the counter is subjected to digital to analog conversion to an analog quantity which is compared with the output command value of a welding machine. The output of the welding machine is regulated by said signal. The welding arc length is always stabilized by the above- mentioned method, by which spatters are decreased and the operability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention shields a welded area with a gas mainly composed of an inert gas, and connects a consumable electrode wire (hereinafter simply referred to as an electrode wire) to the welded area continuously. In a welding method that performs fusion welding by feeding the consumable electrode wire, a welding method (hereinafter referred to as ``welding method'') uses a lasing current as the welding current to transfer the molten metal of the consumable electrode wire into a spray form. This invention relates to a consumable electrode type pulse arc welding machine using a welding voltage control method (simply referred to as the Guls M-G welding method).

(Configuration of conventional example and its problems) In the conventional pulsed MIG welding method, a constant DC current is used in order to apply a pulsed current to actively transfer the wire molten metal to the base metal in a spray state. It has various different characteristics compared to the so-called normal MIG welding method. The major difference in characteristics is that when the welding output is low current, MIG welding progresses welding by repeating short circuits and arcs, whereas in pulsed MIG welding, the wire weld metal is sprayed. The point is that it can be transferred to the base material. When transfer is performed in a spray state, unlike short-circuit transfer welding, there is a big difference in the generation of footing and footing. That is, when spray transfer welding is performed, the amount of spatter generated is extremely small compared to normal short-circuit transfer welding, which is one of the major features of the Luz MIG welding method. However, in the pulsed MIG welding method, if the arc voltage is set low and the arc length is shortened, a short circuit will occur between the electrode wire and the base metal.
If the voltage is too low, short circuits will occur many times, and normal M
As with the IG welding method, splinters and base ivy occur frequently, which is undesirable.On the other hand, if the arc voltage is increased and the arc length is increased, short circuits are less likely to occur between the electrode wire and the base metal. , the arc tends to tilt unstablely, and as a result, the arc is not generated at the desired location, making it impossible to perform good welding.

Figure 1 is a graph showing the relationship between the welding arc voltage and the number of short circuits that occur per second.
mmφ), the number of short circuits increases greatly as the arc voltage decreases, while the arc voltage decreases to 2/1.
When the voltage is higher than V, no short circuit occurs.

FIG. 2 is a graph showing the relationship between the welding arc voltage and the amount of soot and ivy generated, and the welding conditions are the same as in FIG. 1. Spatter increases as the arc voltage decreases, ie, as the number of short circuits increases.

When the arc voltage is 24V or higher, no short circuit will occur,
At this time, almost no smut occurs. According to our detailed experimental results, when the H arc voltage is 24 V or more, increasing the welding speed is not preferable because welding defects such as undercuts occur. On the other hand, when the welding arc voltage is low, even if high-speed welding is performed, undercuts will not occur, but snorkeling will increase, which is undesirable. Therefore, it has been found that when the arc voltage is in the range of (23±0.5) V in FIG. 1, the number of short circuits is 20 times/5 eCJJ, there is little spatter, and the best welding can be performed.

The arc length at this time is 4. It is about rnm.

As mentioned above, in the pulsed MIG welding method, the range of conditions in which it can exhibit its features is extremely limited, and as shown in the example, the arc voltage has a margin of only about 1V.

Furthermore, this appropriate voltage value varies greatly depending on other welding conditions such as welding posture, joint shape, and gas type. For example, regarding the joint shape, the optimal voltage value for fillet welding is 0.5% compared to the optimal voltage value for downward butt welding.
It will be about V lower.

゛As shown above, the problem with the pulsed MIG welding method is not simply that the appropriate voltage conditions are narrow, but that the appropriate welding conditions change depending on the welding construction conditions, which makes it extremely difficult to handle. This has become a major problem in welding work on site.

(Objective of the Invention) The present invention aims to solve the above-mentioned problem ρ, and aims to provide a device that can always control the arc length to an appropriate length.

(Structure of the Invention) The present invention detects the number of short circuits between the electrode wire and the molten part of the base metal that occur during welding at regular intervals (hereinafter referred to as sampling time), and uses the short circuit detection signal to determine the welding arc voltage. In a consumable electrode/Grus arc welding machine that controls the welding output, the preset number of short circuits n8
and the number of short circuits n detected within the sampling time, when the number of differences nd (= ns - n )>0, the arc voltage is lowered according to the value of the number of differences nd, and n-n5>
When the difference ns is 0, the arc voltage is increased according to the value of the difference ns to control the welding output. It has a configuration set so that

(Description of Embodiments) FIG. 3 is a flowchart illustrating the present invention in detail, and its configuration will be described below.

The welding arc voltage waveform is controlled by the short circuit detection level adjustment circuit.
Cut the voltage above a certain level to create a short circuit waveform,
This waveform is shaped and used for short circuit detection and gluing. Count the number n of short circuits and pulses within the sampling time T8, find the difference nd from the preset number n8 of pulses, and calculate (n n
a) When > O, input the difference n4 pulse to the up counter, and conversely, when (na-n) > 0, input the difference n4 pulse to the down counter, and convert the digital output of the counter to analog quantity. Then, the output of this analog quantity is adjusted, and the output of the welding machine is adjusted as a deviation output signal by comparing it with the output command signal of the welding machine. Here, the analog conversion amount for a single digital amount from the counter is configured to be larger in the case of a down counter.

FIG. 4 is a block diagram of an embodiment showing the configuration of the welding machine of the present invention, in which 1 is a short circuit detection circuit, 2 is a short circuit detection level adjustment circuit, 3 is a waveform shaping circuit, 4 is a down counter, and 5 is a short circuit detection circuit.
is an up counter, 6 is a desired value n8 setting circuit, 7 is a sampling time setting circuit, 8.9 is a latch circuit, 10 is a converter, 11 is a pulse generator, 12 is an up/down counter, and 13 is a D/A converter, 14 is a gain adjustment circuit, 15 is a deviation output circuit, 16 is an output command voltage circuit,
17 is a latch circuit control signal generation circuit, 18 and 19 are inverter circuits, 20 and 21 are AND circuits, 22 is a timing adjustment circuit, 23 is an analog switch having a control terminal C1, 24 is an analog switch having a control terminal C2, 25 indicates an inverter.

FIG. 5 shows the output voltage waveform of the circuit shown in FIG. 4, where (a) is the welding arc voltage waveform, (b) is the output waveform of the short circuit detection circuit 1, and (C) is the short circuit/galus voltage waveform. , (d) is the pulse for setting sampling time T8, (e) is the output waveform of the latch circuit control signal generation circuit 17, (f) is the output inversion waveform of the latch circuit control signal generation circuit 17, and (a) is the welding arc voltage. be.

Hereinafter, the configuration and operation of FIG. 4 will be explained together with FIG. 5.

The short circuit detection circuit 1 includes resistors R1t R2r and a Zener diode zDl. This voltage waveform V
The signal a is cut to the level of ■ by the Zener diode ZD, resulting in various waveforms as shown in the figure (b).

The arc voltage Va signal is normally a voltage signal between the welding torch and the welding base metal, and when no welding arc is generated, a no-load voltage is induced, and this no-load voltage value is abnormal compared to the welding arc voltage. expensive. This Zener diode ZD
1 acts to prevent this high voltage from destroying the control circuit of the present invention. The short circuit detection level adjustment circuit 2 includes a resistor R3,
R4, R5, variable resistor VR1, operational amplifier IC1,
It consists of By adjusting the value of the variable resistor VR, it is possible to adjust the short circuit detection level, which is equivalent to adjusting the detection level shown by @ in the axis of Figure 5. The output waveform obtained by inputting the voltage waveform shown in (b) to the waveform shaping circuit 3 shown in FIG. 4 has a constant pulse width and voltage shown in FIG. 5(C).
A pulse waveform is obtained.

That is, the portion where the arc voltage va is short-circuited has a rectangular waveform. This pulse is input to the down counter 4. The intended value n8 setting path 6 determines the intended value n8 of the down counter 4, and the sampling time setting circuit 7 sets the sampling time of the down counter 4.

In the sampling time T8 setting pulse shown in FIG. 5(d), the pulse interval T8 indicates the sampling time. When the short circuit or pulse shown in FIG. 5(c) is input to the down counter 4, the output of the down counter 4 is counted down from the set value n8 according to the number n of short circuit pulses within the sampling time T8. When the short-circuit/glucose number n is smaller than the set value n8, that is, when n<ns, the output nd of the down counter 4 (this value is equal to the value of R8-n) is input to the latch circuits 8 and 9. be done. 17 is a latch circuit control signal generation circuit, the output waveform of which is shown in FIG. 5(e). When the latch signal (e) input to the latch circuit 8 is at high level, the latch circuit 8 inputs the short circuit pulse signal from the counter 4, and when it is at low level, it holds the data. The latch signal (e) is also input to the latch circuit 9 through the inverter circuit 18. This latch signal (
f) is shown in FIG.

The latch signals (e) and (f) have opposite phases. Therefore, as mentioned above, the output of the down counter 4 is input to the latch circuits 8 and 9, but when one latch circuit is inputting a short circuit pulse, the other latch circuit is inputting a short circuit pulse. First, it works to hold the previous cycle data (that is, the data from one sampling time ago).

Next, when the number of short circuit pulses n is larger than the set value n, that is, n
The operation when ≧n will be explained.

When the number of short-circuit pulses n becomes equal to the set value nS, 4
Since is a down counter, its output nd is 0. When the output of the down counter 4 becomes O, the carry-out signal of the down counter 4 changes from high level to low level. This carry-out signal is converted to a high level through the entire inverter circuit 19 and is input to the A terminal of the AND circuit 20. A short circuit pulse signal is input to the other B terminal of the AND circuit 20. That is, as is clear from the above explanation, when the number n of short circuits and pulses becomes equal to the set value n8, the A terminal of the AND circuit 20 becomes the NO level, so the short circuit and pulse signal increases through the AND circuit 200B terminal. It is input to counter 5.

A signal for determining the sampling time is also input to the up counter 5 from the sampling time setting circuit 7. That is, the number of pulses nd ("' n n8) exceeding the set number of pulses n8 is input to the up counter 5. The set value of the up counter 5 is O. Therefore, the output of the up counter 5 is equal to nd. This Noculus has latch circuit 8.
and 9.

Therefore, when the number n of short-circuit Noculus within the sampling time TS is smaller than the set pulse number n8 (n<ns), the difference number 9
The pulse number nd (2n8-n) is output from the down counter 4 and input to the latch circuits 8 and 9. on the other hand,
When the number of short-circuit pulses n within the sampling time T8 is greater than the set Q pulse number n8 (n≧n8), the difference pulse number nd
(=n-ns) is output from the up counter 5 and input to the latch circuits 8 and 9. As mentioned above, the latch circuits 8 and 9 work alternately, and when one is in the input state, the other holds the data (nd)' of the previous cycle, and this held data is , is input to the A input terminal of the converter 10. The comparator 10 is an element that compares and outputs the magnitude of input data from two input terminals, and the other input terminal B receives the pulse ns from the pulse generator 11. The output of the comparator 10 is input to the A terminal of the AND circuit 21. The output of the comparator 10 is the number np of pulses input inversely to the B input terminal, which is set to the A input terminal.
Rus number ns,! : High level until equal,
When more iP pulse n is input to the input terminal, the output of the comparator 10 becomes low level. Since the output signal of the comparator 10 is connected to the A terminal of the AND circuit 21, the i9 pulse np of the Noculus generator 11 is inputted to the up/down counter 2 by the number equal to the pulse number ns through the entire AND circuit 21. I live to be treated.

The carry-out signal of the down counter 4 is used for the up/down control terminal of the up/down counter 2. The carry-out signal of down counter 4 is n
-n) When O, this carry-out signal goes to the low level throughout the input circuit 19. This low level signal is the up/down counter 2
When inputted to the up/down control terminal of the up/down counter 12, the up/down counter 12 functions as a down counter. On the other hand n-n5
When ≧0, the carry-out signal is at a low level, and this carry-out signal passes through the inverter circuit 19 and becomes no impel. When this no-in-bell signal is input to the up-down control terminal of the up-down counter 12, the counter 12 functions as an up-counter. in·
The carry-out signal that has traced the mater circuit 19 is connected to the up/down counter 12 through the entire timing circuit 22, but this is because the output pulses nd of the up and down counters 4 and 5 are once sent to the latch circuits 8 and 9. As a result, the timing of the pulse nd input to the up/down counter 12 and the carry-out signal of the down counter 4 is different from each other. A circuit that adjusts this timing is the timing adjustment circuit 22.

The output of the up/down counter 12 is input to a D/A converter 13, and the digital signal is converted into an analog signal.

n-n)O, the up-down counter 12 functions as a down counter, and the output digital amount of the up-down counter 12 decreases by the number of pulses n4""18n. On the other hand, when n-n8≧0, up/down counter 1
2 works as an up counter, and the number of pulses d = n
The output of the up/down counter 12 increases by -ns. A key adjustment circuit 14 is an output adjustment circuit for the analog output of the converter 13, and its output is connected to the deviation output circuit 15.

The gain adjustment circuit 14 is an output adjustment circuit for the analog output of the D/A converter 13, and is connected to a resistor R6゜R7*.
RB, O-wave amplifier IC3, and analog switch 2
3 and 24. analog switch 23
and 24 have control terminals C1 and C2, respectively, and when there is a high level input to the control terminals CI and C2, the impedance between the input and output becomes low impedance, and the D-level input signal to the control terminal C
1, C2, the element has a high impedance between input and output.

The input signal to the timing adjustment circuit 22 is n-n8≧0.
When , it becomes high level and R5-n>.

When , it becomes a low level, but this human input signal is input to the CI control terminal of the analog switch 23.
On the other hand, this input signal is inputted to the control terminal C2 of the analog switch 24 with its output level inverted through the inverter 25. Therefore, when n-n ≧0, that is, when the up-down counter 12 works as an up-counter, the output of the D/A converter 13 is sent to the input/output adjustment circuit 14 so that the input and output of the analog switch 23 is Since the impedance is low (at this time, there is a high impedance between the input and output of the analog switch 24), the output adjustment determined by the resistor R6 is performed. Conversely, when n - n>0,
That is, when the counter 12 works as a down counter, D
The output of the /A converter 13 is determined by the resistor R7, since there is a low impedance between the input and output of the analog switch 24 in the input adjustment circuit 14 (at this time, there is high impedance between the input and output of the analog switch 23). Power adjustments are made. The impedances of the resistor R6 and the resistor R7 are different, and the impedance of the resistor R7 is configured to have a larger value than the impedance of the resistor R6. That is, when the counter 12 functions as a down counter, the output adjustment value of its analog output is larger than the output adjustment value of the analog output in the case of an up counter.

With the above configuration, the arc voltage drop value per difference number ns becomes a larger value than the arc voltage rise value.

The output signal of the output command voltage circuit 16 composed of a welding machine output adjustment remote controller, etc. is input to the A terminal of the output command voltage circuit 16 mainly composed of an operational amplifier IC2,
The output signal of the gain adjustment circuit 14 is connected to the other B terminal. The output of the deviation output circuit 15 is input to a control circuit of an output control element (not shown) of the welding machine to adjust the welding output.

As is clear from the above, since the arc voltage Vh is high, when the number n of pulses generated within the sampling time Ts is smaller than the set pulse number n8, the output of the deviation output circuit 15 decreases by the difference pulse number nd. However, the welding machine output voltage is decreased to increase the number of short circuit pulses.

On the other hand, if the arc voltage Va is low and the number of pulses n is larger than the set number of pulses n8, the output of the deviation output circuit 15 increases by the difference/number of pulses ns, increasing the welding machine output voltage. The number n of short-circuit pulses is controlled to decrease by increasing the number n of short-circuit pulses. Here, the arc voltage drop value of the differential circuit nd is set to be a larger value than the arc voltage rise value. In other words, the amount of analog conversion for short circuits and leaks varies when the output increases and decreases.Even if the number of differences is the same T14, the arc voltage drop value is higher than the arc voltage rise value. takes a larger value.

The reason for such a configuration will be explained next. Number of short circuits n
<ns, the number of differences n4 = ns n,
The maximum value of this value is when n = O, that is, nd = ns
In other words, the value of the number of differences n6 is n8
It is impossible to obtain a value larger than this. On the other hand, when n) n8r1Q), the difference number n d""' i n s is, and when the arc voltage is low and n is large, the ndO value is slightly larger than n8, that is, n<ns , the number of differences is determined by the maximum value n8, whereas n8
When n, there is no maximum limit value. For this reason, in an actual arc, an imbalance may occur with respect to the rise and fall of the arc voltage. At this time, the arc becomes unstable, and this tendency becomes particularly noticeable when the initial setting value nsO is set to a small value. However, as in the present invention, a stable arc can be obtained by changing the output voltage adjustment value per differential number ns, that is, the gain.

That is, according to the configuration example of the present invention, when the number of short circuits that occur in the weld is greater than the initial setting value, the welding output voltage is immediately increased to prevent the number of short circuits from increasing, while the number of short circuits is When it is less than the value, the welding output voltage is immediately reduced to maintain an appropriate arc length. In particular, by changing the circuit gain when the output voltage rises and falls, an even more stable arc can be obtained.

(Effects of the Invention) As explained above, the present invention uses a gas mainly composed of inert bottom gas, feeds a consumable electrode wire to a welding part, and performs fusion welding using a pulsed welding current. do, so-called/
This invention provides a new control method for the output voltage of the OLS MIG welding method.When the number of short circuits occurs is greater than a set value, the welding voltage is immediately increased to prevent an increase in the occurrence of short circuits, and the welding arc voltage is As soon as the number of short circuits increases and the number of short circuits that occur falls below the set value, the welding voltage is immediately lowered and the welding voltage is controlled so that an appropriate arc length (the number of short circuits is the set value n) is obtained.

Because the arc length is always controlled to an appropriate length by the above-mentioned functions, the arc is extremely stable and good welding results with less spatter can be obtained.

In addition, even if the distance between the torch and the welding part changes due to the welder's camera shake, the arc length remains constant, eliminating the need to set delicate welding conditions that previously required a certain level of skill. , welding efficiency is significantly improved, and there is great economic efficiency.

In addition, the appropriate voltage value for welding output varies depending on the construction conditions such as welding posture, joint shape, and gas type, but according to the present invention, the arc length is always controlled to the appropriate number of short circuits. , it is possible to perform highly efficient welding with extremely excellent workability.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the welding arc voltage and the number of short circuits that occur per second, Figure 2 is a graph showing the relationship between the welding arc voltage and the amount of spruce and base ivy generated, and Figure 3 is the graph showing the relationship between the welding arc voltage and the number of short circuits that occur per second. A flowchart explaining the invention in detail, FIG. 4 is a block diagram of an embodiment showing the configuration of the welding machine of the present invention, and FIG.
FIG. 3 is a diagram showing an output voltage waveform of the circuit shown in the figure. l... Short circuit detection circuit, 2... Short circuit detection level adjustment circuit, 3... Waveform shaping circuit, 4... Down counter,
5... Azzo counter, 6... Initial value n setting circuit, 7... Sampling time setting circuit, 8, 9-touch circuit, 10... Comparator, 11... Pulse generator, 12 ...Up-down counter, 13...D/
A converter, 14... Gain adjustment circuit, 15... Deviation output circuit, 1G... Output command voltage circuit, 17... Latch circuit control signal generation circuit, 18, 19... Inverter circuit, 20 .21...AND circuit, 22...timing adjustment circuit, 23...analog switch having control terminal c1, 24...control terminal c
an analog switch having 2, 25...inverter;

Claims (1)

[Claims] A consumable electrode type pulse arc welding machine that detects the number of short circuits between the electrode wire and the molten base metal that occur during welding at regular intervals, and controls the welding arc voltage based on the short circuit detection signal to control the welding output. , a preset number of short circuits n_s and a number of short circuits detected within the certain period of time n
When the number of differences n_d (=n_s-n)>0, the arc voltage is lowered according to the value of the number of differences n_d, and n-n
When _s>0, the method includes means for controlling the welding output by increasing the arc voltage according to the value of the difference n_d, and setting the arc voltage decrease value per the number of differences n_d to a value larger than the arc voltage increase value. A consumable electrode type pulse arc welding machine characterized by being set to