JP4907892B2 - Constriction detection control method for consumable electrode arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy of detecting constriction in a method for detecting/controlling constriction in consumable electrode arc welding attended with a short circuit. <P>SOLUTION: In this method for detecting/controlling constriction in consumable electrode arc welding, the constrictive phenomenon of a droplet as a sign phenomenon of regeneration of arc from a short-circuit state is detected by that a change in a voltage or resistance value between a consumable electrode and a base metal reaches a reference value Vtn for detecting the constriction, thereby a welding current is rapidly reduced. The constriction detecting time is detected for each short-circuit, storing the detecting time from the current point of time retroactively to the prescribed number of time in the past (MT). When the number of each stored constriction detecting time (Mt) below the minimum value inclusive is not less than the minimum number, the reference value Vtn for detecting the constriction is decreased by the variation &Delta;F. When the number of each stored constriction detecting time (Mt) above the maximum value inclusive is not less than the maximum number, the reference value Vtn for detecting the constriction is increased by the variation &Delta;F. Thus, the reference value Vtn for detecting the constriction is optimized. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a constriction detection control method of consumable electrode arc welding for detecting a constriction phenomenon of a droplet during a short-circuiting period and rapidly reducing a welding current to improve welding quality.

  FIG. 4 is a diagram showing current / voltage waveforms and droplet transfer in consumable electrode arc welding in which the short-circuit period Ts and the arc period Ta are repeated. FIG. 4A shows the change over time in the welding current Iw for energizing the consumable electrode (hereinafter referred to as welding wire 1), and FIG. 4B shows the time of the welding voltage Vw applied between the welding wire 1 and the base material 2. FIG. FIGS. 3C to 3E show the transition of the droplet 1a. Hereinafter, a description will be given with reference to FIG.

  During the short-circuit period Ts from time t1 to t3, the droplet 1a at the tip of the welding wire 1 is short-circuited with the base material 2, and as shown in FIG. As shown in B), since the welding voltage Vw is in a short circuit state, the welding voltage Vw becomes a low value of about several volts. As shown in FIG. 5C, the droplet 1a comes into contact with the base material 2 at a time t1 to enter a short circuit state. Thereafter, as shown in FIG. 4D, a constriction 1b is generated at the upper part of the droplet 1a by an electromagnetic pinch force generated by a welding current Iw for energizing the droplet 1a. And this constriction 1b advances rapidly, and as shown to the same figure (E) at the time t3, the droplet 1a transfers from the welding wire 1 to the molten pool 2a, and the arc 3 regenerates.

  When the above-mentioned constriction phenomenon occurs, the short circuit is released after an extremely short time of about several hundred μs, and the arc 3 is regenerated. That is, this constriction phenomenon is a precursor of short circuit opening. When the constriction 1b occurs, the conduction path of the welding current Iw becomes narrow at the constricted portion, and the resistance value of the constricted portion increases. The increase in the resistance value increases as the constriction progresses and the constricted portion becomes narrower. Therefore, the occurrence and progress of the constriction phenomenon can be detected by detecting the change in resistance value between the welding wire 1 and the base material 2 during the short-circuit period Ts. This change in resistance value can be calculated by welding voltage Vw / welding current Iw. Further, as described above, since the constriction occurrence time is extremely short, the change in the welding current Iw during this period is small as shown in FIG. For this reason, the occurrence of the constriction phenomenon can be detected by the change of the welding voltage Vw instead of the change of the resistance value. As a specific necking detection method, a change rate (differential value) of the resistance value or the welding voltage value Vw during the short-circuit period Ts is calculated, and the necking detection is performed when the rate of change reaches a predetermined necking detection reference value. There is a way to do. As another method, as shown in FIG. 5B, a voltage increase value ΔV from a stable short-circuit voltage value Vs before occurrence of constriction during the short-circuit period Ts is calculated, and this voltage increase value ΔV is calculated at time t2. There is a method of detecting the squeezing when the squeezing reaches a predetermined squeezing detection reference value Vtn. In the following description, a case in which the squeezing detection method is based on the above-described voltage increase value ΔV will be described, but other methods that have been proposed in the past may be used. Detection of arc reoccurrence at time t3 can be easily performed by determining that the welding voltage Vw has become equal to or greater than the short circuit / arc determination value Vta. Incidentally, the period of Vw <Vta is the short circuit period Ts, and the period of Vw ≧ Vta is the arc period Ta. The time from the occurrence of squeezing at times t2 to t3 to the reoccurrence of the arc is hereinafter referred to as squeezing detection time Tn. When the arc is regenerated at the time t3, the welding current Iw gradually decreases after rapidly increasing as shown in FIG. 9A, and the welding voltage Vw is about several tens of volts as shown in FIG. Arc voltage value. During the arc period Ta from time t3 to t4, the tip of the welding wire 1 is melted to form a droplet 1a. Thereafter, the operation in the period from time t1 to t4 is repeated.

  In the welding with short circuit described above, when the arc regeneration current value Ia when the arc 3 is regenerated at the time t3 is a large current value, the arc force from the arc 3 to the molten pool 2a increases sharply. A large amount of spatter is generated. That is, the amount of spatter generated increases substantially in proportion to the current value Ia at the time of arc re-generation. Therefore, in order to suppress the occurrence of sputtering, it is necessary to reduce the current value Ia at the time of arc re-occurrence. As a method for this, various welding power sources have been proposed in which a constriction detection control method is added to detect the occurrence of the above-mentioned constriction phenomenon, to rapidly reduce the welding current Iw and to reduce the current value Ia at the time of arc reoccurrence. . Hereinafter, this prior art will be described.

  FIG. 5 is a block diagram of a welding power source adopting a squeezing detection control method of the prior art. The welding power source PS is a general welding power source for consumable electrode arc welding. The transistor TR is inserted in series with the output, and a resistor R is connected in parallel therewith. The squeezing detection control circuit ND outputs a squeezing detection signal Nd that is at a high level when the welding voltage Vw is input to detect the occurrence of squeezing of the droplet during the short-circuiting period by increasing the voltage. Details of the constriction detection control circuit ND will be described later with reference to FIG. When the squeezing detection signal Nd is at a low level (when non-necking is detected), the driving circuit DR outputs a driving signal Dr that turns on the transistor TR. Therefore, the transistor TR is turned off when the squeezing detection signal Nd is at a high level (when squeezing is detected).

  FIG. 6 is a timing chart of each signal of the welding power source. 4A shows the welding current Iw, FIG. 2B shows the welding voltage Vw, FIG. 3C shows the squeezing detection signal Nd, and FIG. 4D shows the time change of the drive signal Dr. Hereinafter, a description will be given with reference to FIG.

  In the figure, during a period other than the squeezing detection time Tn from time t2 to t3, as shown in FIG. 10C, the squeezing detection signal Nd is at the low level, and as shown in FIG. The signal Dr becomes a high level. As a result, since the transistor TR is turned on, the operation is the same as that of a normal welding power source for consumable electrode arc welding.

  At time t2, as shown in FIG. 5B, it is detected that the welding voltage Vw has increased during the short-circuit period Ts and the voltage increase value ΔV has become equal to or greater than a predetermined squeezing detection reference value Vtn. If it is determined that constriction has occurred, the constriction detection signal Nd becomes High level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr goes to a low level, so that the transistor TR is turned off. As a result, the resistor R is inserted into the energization path of the welding current Iw. Since the value of this resistor R is set to a value that is at least 10 times larger than the short-circuit load (several tens of mΩ), it is accumulated in the DC reactor in the welding power source and the cable reactor as shown in FIG. As a result, the welding current Iw decreases rapidly. At time t3, when the short circuit is released and the arc is regenerated, the welding voltage Vw becomes equal to or higher than a predetermined short circuit / arc discrimination value Vta as shown in FIG. By detecting this, the squeezing detection signal Nd becomes the Low level as shown in FIG. 5C, and the drive signal Dr becomes the High level as shown in FIG. As a result, the transistor TR is turned on, and normal consumable electrode arc welding is controlled. By this operation, the arc regeneration current value Ia at the time of arc regeneration (time t3) can be reduced, and the occurrence of sputtering can be suppressed.

  FIG. 7 is a detailed block diagram of the squeezing detection control circuit ND in the welding power source described above with reference to FIG. Hereinafter, a description will be given with reference to FIG.

  In the figure, the welding voltage Vw is input, the necking detection reference value Vtn is optimized, the necking phenomenon is detected, and the necking detection signal Nd is output. The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. As described above with reference to FIG. 4, the voltage increase value detection circuit DV receives the welding voltage detection signal Vd as an input, detects the voltage increase value from the short circuit voltage Vs during the short circuit period, and outputs the voltage increase value signal ΔV. The squeezing comparison circuit CMN compares this voltage rise value signal ΔV with a squeezing detection reference value signal Vtn, which will be described later, and outputs a set signal St that becomes High level only for a short time when ΔV ≧ Vtn. The re-arc comparison circuit CMA compares the welding voltage detection signal Vd with a predetermined short-circuit / arc discrimination value Vta, and when the Vd ≧ Vta is satisfied, the re-arc comparison signal Cma that is at a high level for a short time. Is output. The squeezing detection time comparison circuit CMT detects a squeezing detection time Tn with an input of a squeezing detection signal Nd, which will be described later. A squeezing detection time comparison signal Cmt is output. The OR circuit OR performs a logical sum of the re-arc comparison signal Cma and the squeezing detection time comparison signal Cmt, and outputs a reset signal Rt. The flip-flop circuit FF outputs a squeezing detection signal Nd that is set to High level when the set signal St changes to High level, and is reset to Low level when the reset signal Rt changes to High level. That is, the squeezing detection signal Nd changes to the high level when the squeezing is detected, and returns to the low level when the arc is re-arced. Further, when the squeezing detection time Tn becomes equal to or greater than the maximum value Tnm, the level returns to the low level even before re-arcing. Therefore, when Tn ≧ Tnm, the above-described transistor TR in FIG. 5 is turned on, and the welding current Iw increases to the short-circuit current. This is because the constriction detection time Tn exceeds the maximum value Tnm because there is a high possibility that the constriction is erroneously detected. In the above description, the case where the voltage rise value signal ΔV is used as the constriction detection method has been described. However, as described above, even if the rate of change of the resistance value or the welding voltage value of the droplet portion during the short circuit period is used, the same applies. It is. In addition, as a method of suddenly decreasing the current when the squeezing detection signal Nd becomes a high level, various conventionally proposed methods other than the methods described above with reference to FIGS. 5 and 6 can be used.

  The squeezing detection time calculation circuit TNA receives the squeezing detection signal Nd as an input, calculates a squeezing detection time Tn for each short circuit, and outputs a squeezing detection time calculation signal Tna. At this time, the squeezing detection time calculation signal Tna may be a moving average value of the squeezing detection times Tn for a predetermined number of times in the past. The squeezing detection time setting circuit TNR outputs a predetermined squeezing detection time setting signal Tnr. The error amplification circuit EA amplifies an error between the squeezing detection time setting signal Tnr and the squeezing detection time calculation signal Tna, and outputs an error amplification signal ΔE. The squeezing detection reference value setting circuit VTN receives the error amplification signal ΔE as an input, adds the error amplification signal ΔE to the squeezing detection reference value signal Vtn (n-1) at the time of the previous short circuit, and optimizes the squeezing detection reference value. The signal Vtn (n) = Vtn (n-1) + ΔE is output.

  FIG. 8 is a relationship diagram of input / output signals in the error amplifier circuit EA. The horizontal axis represents the input signal ΔT [μs] = Tnr−Tna, and the vertical axis represents the output signal ΔE [V] = Gain · ΔT. The amplification factor Gain is a negative number, for example, Gain = −0.01 V / 50 μs. Specific numerical examples will be given. When the squeezing detection time setting signal Tnr = 250 μs and the maximum squeezing detection time Tnm = 500 μs, the range of the squeezing detection time calculation signal Tna is 0 to 500 μs. Therefore, the input signal ΔT is in the range of −250 to +250 μs, and the error amplification signal ΔE that is the output signal is in the range of +0.05 to −0.05 V. The squeezing detection reference value Vtn is set to an appropriate value in accordance with the welding conditions in the range of about 1 to 5V. Each time a short circuit occurs, the error amplification signal ΔE is added to the squeezing detection reference value Vtn (n-1) at the time of the previous short circuit and corrected. When the squeezing detection time calculation signal Tna is smaller than the squeezing detection time setting signal Tnr, ΔT> 0 and ΔE <0, and the squeezing detection reference value signal Vtn (n) becomes small. As a result, the squeezing detection sensitivity increases and the squeezing detection time calculation signal Tna becomes longer in a direction approaching the squeezing detection time setting signal Tnr. Conversely, when the squeezing detection time calculation signal Tna is larger than the squeezing detection time setting signal Tnr, ΔT <0, so that ΔE> 0, and the squeezing detection reference value signal Vtn (n) becomes large. As a result, the squeezing detection sensitivity decreases and the squeezing detection time calculation signal Tna becomes shorter in a direction approaching the squeezing detection time setting signal Tnr. In this way, the squeezing detection reference value signal Vtn converges to an appropriate value.

JP 59-206159 A JP-A-1-205875

  Even if various welding conditions such as the material of the welding wire, the type of shield gas, and the welding speed change, the appropriate value of the squeezing detection time Tn does not change much, but the squeezing detection reference value Vtn changes greatly. In addition to the welding conditions, the squeezing detection reference value Vtn varies greatly depending on from which detection point the welding voltage Vw is detected. The ideal detection point is between the power feed tip and the base material, but there are various cases, such as between the output terminals of the welding power source due to restrictions on the actual detection line wiring, or the base material side is the terminal of the positioner. is there.

  In FIG. 8 described above, the error ΔT between the squeezing detection time calculation signal Tna and the squeezing detection time setting signal Tnr does not stick to a range of less than ± 250 μs, that is, the maximum value or the minimum value when the welding conditions or the like change. There is no problem in the optimization processing of the squeezing detection reference value Vtn using the error amplification signal ΔE. However, when the error ΔT reaches the maximum value or the minimum value, there is no possibility that the squeezing detection reference value Vtn greatly deviates from the appropriate value because there is no error ΔT greater than that value. The error ΔT is the minimum value (−250 μs) as shown in FIG. 9 when the squeezing detection time Tn reaches the maximum value Tnm (500 μs). As shown in FIG. 6A, the constriction is detected at time t2, and the welding current Iw is rapidly reduced. When the squeezing detection time Tn reaches the maximum value Tnm at time t21, if the arc does not reoccur, the welding current Iw is increased to return to the short-circuit current. Then, the arc is regenerated at time t3. The reason why the maximum value is provided for the constriction detection time Tn is that when the constriction detection time Tn is too long, there is a high possibility that the constriction is erroneously detected. In this case, the squeezing detection reference value Vtn is too small. Further, when the error ΔT is the maximum value (+250 μs), as shown in FIG. 10, the squeezing detection time Tn becomes the minimum value (0 μs). As shown in FIG. 5A, the arc is regenerated at time t3 without detecting a constriction. In this case, the squeezing detection reference value Vtn is too large.

  As described above, when the squeezing detection time Tn reaches the maximum value or the minimum value, the conventional squeezing detection reference value Vtn using the error amplification signal ΔE takes a long time to converge, and spattering occurs during the transition period. Many occur. In some cases, the arc state becomes unstable, and the welding quality may deteriorate. In order to cope with this, when the gain Gain described above in FIG. 8 is increased, the control system for optimizing the squeezing detection reference value becomes unstable.

  Therefore, the present invention provides a constriction detection control method for consumable electrode arc welding that can quickly converge the constriction detection reference value Vtn to an appropriate value even when the constriction detection time Tn reaches the maximum value or the minimum value.

In order to solve the above-described problems, a first invention is a consumable electrode arc welding in which an arc generation state and a short circuit state are repeated between a consumable electrode and a base material, and a sign that an arc is regenerated from the short circuit state. The phenomenon of droplet constriction, which is a phenomenon, is detected when the change in the voltage value or resistance value between the consumable electrode and the base material reaches the squeezing detection reference value. The output is controlled so that the arc is re-generated at a low current value with a sudden decrease, and the squeezing detection reference value is optimized so that the squeezing detection time from the time of detecting the squeezing phenomenon to the time of re-occurring arc becomes the set value. In the constriction detection control method for consumable electrode arc welding,
The squeezing detection time is detected and stored for each short circuit, and the number of the squeezing detection times for a predetermined number of past multiples from the stored current time is less than a predetermined minimum value. when the above number is decreased by decreasing values predetermined said squeezing detection reference value, said time stored the squeezing detection time is the number is greater than or equal to the maximum value number of predetermined at a predetermined maximum value or the Increase the squeezing detection reference value by a predetermined increase value , and repeat these processes for each short circuit .
This is a constriction detection control method for consumable electrode arc welding.

  A second invention is a constriction detection control method for consumable electrode arc welding, wherein the minimum value described in the first invention is 0 μs.

  When the stored number of squeezing detection times is not more than the minimum value or more than the minimum number, or when the number of stored squeezing detection times or more is not less than the maximum value, the number is stored. The constriction detection control method for consumable electrode arc welding according to the first or second invention, wherein all the constriction detection times are once reset.

  According to the present invention, the squeezing detection reference value is set to a predetermined decrease value when the number of squeezing detection time groups stored is less than the minimum value or greater than or equal to the maximum value. Alternatively, by correcting only the increase value, even if the squeezing detection reference value is greatly deviated from the appropriate value, it can be quickly converged to the appropriate value. Further, when the deviation of the squeezing detection reference value is small, the correction factor amplification factor is reduced, so that the squeezing detection reference value optimization control system can be kept stable. For this reason, even if welding conditions change, the squeezing detection reference value can always be maintained at an appropriate value, and good welding quality with less spatter can be obtained.

  According to the third aspect of the invention, in addition to the above effects, when the number of stored squeezing detection time groups whose value is less than the minimum value or more than the maximum value is greater than or equal to the predetermined number, the squeezing occurs. After correcting the detection reference value by a predetermined decrease value or increase value, all the stored squeezing detection time groups are once reset. As a result, the correction by the decrease value or the increase value is not continuously performed for each short circuit. For this reason, the correction of the squeezing detection reference value does not become excessive, and the control system is further stabilized.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
In the first embodiment of the present invention, the squeezing detection time Tn is detected for each short circuit, and the squeezing detection times Tn of the predetermined predetermined number of memories from the present time are stored, and each stored squeezing detection time Tn is less than the minimum value. When a certain number is equal to or greater than the minimum number of times, the squeezing detection reference value Vtn is decreased by a predetermined decrease value ΔD, and when the number of stored squeezing detection times Tn is equal to or greater than the maximum value, the squeezing is detected. This is a constriction detection control method for consumable electrode arc welding in which the detection reference value Vtn is increased by a predetermined increase value ΔU. Details of the first embodiment will be described below.

  The block diagram of the welding power source for carrying out the constriction detection control method for consumable electrode arc welding according to Embodiment 1 of the present invention is the block diagram shown in FIG. 1 for the constriction detection control circuit ND in FIG. It is. In FIG. 1, the same blocks as those in FIG. 7 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 7 will be described with reference to FIG.

  The squeezing detection time group storage circuit MT receives a squeezing detection signal Nd, detects a squeezing detection time for each short circuit, stores a squeezing detection time group having a predetermined number of memories from the present time, and a squeezing detection time group storage signal. Mt is output. That is, when the n-th short-circuit occurs, the (n-1) -th short circuit neck detection time Tn (n-1), the (n-2) -th short-circuit neck detection time Tn (n-2),... , The number m of the squeezing detection time Tn (nm) at the time of the (n−m) th short circuit is stored.

  The excess number determination circuit OC performs the processing shown in the flowchart of FIG. 2 with the above-described squeezing detection time group storage signal Mt as an input, and outputs an increase / decrease value signal ΔF and an excess number signal So. Hereinafter, the processing contents will be described with reference to FIG. In step ST1, the number of stored squeezing detection time groups (Tn (n-1), Tn (n-2),..., Tn (n-m)) is read from the squeezing detection time group storage signal Mt. In step ST2, the number of m squeezing detection time groups whose value is equal to or smaller than a predetermined minimum value Tni is counted, and if the counted value is equal to or larger than the predetermined minimum value number Ni, the process proceeds to step ST3. If less, the process proceeds to step ST4. In step ST3, the number-of-times excess signal So is set to the High level, and a predetermined decrease value ΔD is substituted and output for the increase / decrease value signal ΔF, and the processing is quantified. In step ST4, the number of m squeezing detection time groups whose value is equal to or greater than a predetermined maximum value Tnm is counted. If the count value is equal to or greater than the predetermined maximum value number Nm, the process proceeds to step ST5. If less, the process proceeds to step ST6. In step ST5, the number-of-times excess signal So is set to High level, a predetermined increase value ΔU is substituted for the increase / decrease value signal ΔF, and the process is terminated. In step ST6, the excess count signal So is set to the Low level and output. The above process is repeated for each short circuit.

  The above values are as follows. The number of times of storage m is about 10 to several tens, the minimum value Tni is about 0 to several tens of μs, the minimum number Ni is about several% to several tens of% with respect to m, and the decrease value ΔD is 0.1 to 0. About 5V. Further, the maximum value Tnm is about 400 to 500 μs, the maximum value number Nm is about several% to several tens% with respect to m, and the increase value ΔU is about 0.1 to 0.5V. Specifically, m = 16, Tni = 0 μs, Ni = 2 times, ΔD = 0.5 V, Tnm = 500 μs, Nm = 2 times, and ΔU = 0.5 V. These setting ranges and numerical examples are merely examples and vary depending on welding conditions and the like.

  The switching circuit SW outputs the error amplification signal ΔE as the correction value signal ΔG when the above-exceeded number signal So is at the Low level, and outputs the increase / decrease value signal ΔF as the correction value signal ΔG when the signal is the High level. The squeezing detection reference value setting circuit VTN receives this correction value signal ΔG as an input, adds the correction value signal ΔG to the squeezing detection reference value signal Vtn (n-1) at the previous short-circuit, and optimizes it, thereby making the squeezing detection reference value The signal Vtn (n) = Vtn (n-1) + ΔG is output. The subsequent operation is the same as that in FIG.

  In the first embodiment described above, the squeezing detection criterion is based on the error amplification signal ΔE described above with reference to FIG. 8 when the number less than the minimum value or the maximum value is less than the predetermined number among the m squeezing detection time groups stored. The value Vtn is optimized. Thus, when the error ΔT is small, it is not necessary to increase the amplification factor, and the control system is stabilized. On the other hand, when the number less than the maximum value or more than the maximum value in the stored m number of squeezing detection time groups is a predetermined number or more, the squeezing detection reference value Vtn is optimized by the increase / decrease value signal ΔG. As described above, since the increase / decrease value signal ΔG is considerably larger than the error amplification signal ΔE, the increase / decrease value signal ΔG can be converged quickly even if the squeezing detection reference value Vtn is greatly deviated from the appropriate value.

[Embodiment 2]
The block diagram of the welding power source for carrying out the constriction detection control method of consumable electrode arc welding according to Embodiment 2 of the present invention is the block diagram shown in FIG. 3 for the constriction detection control circuit ND in FIG. It is. In FIG. 3, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 1 will be described with reference to FIG.

  The second squeezing detection time group storage circuit MT2 receives the squeezing detection signal Nd as input, detects a squeezing detection time for each short circuit, stores a squeezing detection time group having a predetermined number of memories from the present time, and stores a squeezing detection time group. The signal Mt is output. Further, the second squeezing detection time group storage circuit MT2 resets all the stored squeezing detection time groups when the over-count signal So becomes High level. That is, when the n-th short-circuit occurs, the (n-1) -th short circuit neck detection time Tn (n-1), the (n-2) -th short-circuit neck detection time Tn (n-2),... , The number m of the squeezing detection time Tn (nm) at the time of the (n−m) th short circuit is stored. When reset, m necking detection times are memorized again from the next short circuit. As a result, it is possible to prevent the increase / decrease value signal ΔF from being continuously output and the squeezing detection reference value Vtn from being excessively corrected, and to further improve the stability of the control system.

It is a block diagram of the constriction control circuit ND which concerns on Embodiment 1 of this invention. It is a flowchart which shows the processing content of the excess number determination circuit OC of FIG. It is a block diagram of the constriction control circuit ND which concerns on Embodiment 2 of this invention. It is a current and voltage waveform diagram of consumable electrode arc welding in the prior art. It is a block diagram of the welding power supply which employ | adopted the necking detection control method of the prior art. It is a timing chart of each signal of the welding power supply of FIG. FIG. 6 is a block diagram of a squeezing detection control circuit ND in FIG. 5. FIG. 8 is a relationship diagram of input / output signals of the error amplifier circuit EA of FIG. 7. It is a current / voltage waveform diagram when the squeezing detection time is the maximum value. FIG. 6 is a current / voltage waveform diagram when the squeezing detection time is a minimum value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 2 Base material 2a Weld pool 3 Arc CMA Re-arc comparison circuit Cma Re-arc comparison signal CMN Neck comparison circuit CMT Neck detection time comparison circuit Cmt Neck detection time comparison signal DR Drive circuit Dr Drive signal DV Voltage rise value Detection circuit EA Error amplification circuit FF Flip-flop circuit Gain Amplification factor Ia Arc regeneration current value Iw Welding current m Memory count MT Constriction detection time group memory circuit MT Constriction detection time group memory signal MT2 Second constriction detection time group memory circuit ND Constriction detection control circuit Nd Constriction detection signal Ni Minimum value number Nm Maximum value number OC Excess number determination circuit OR OR circuit PS Welding power source R Resistor Rt Reset signal So Excess number signal St Set signal SW Switching circuit Ta Arc period Tn Constriction detection Time TNA Constriction detection time calculation circuit Tna Constriction Output time calculation signal Tni (Neck detection time) Minimum value Tnm (Neck detection time) Maximum value TNR Neck detection time setting circuit Tnr Neck detection time setting signal TR Transistor Ts Short circuit period VD Welding voltage detection circuit Vd Welding voltage detection signal Vs Short-circuit voltage value Vta Short-circuit / arc discrimination value Vtn Necking detection reference value (signal)
Vw Welding voltage ΔD Decrease value ΔE Error amplification signal ΔF Increase / decrease value signal ΔG Correction value signal ΔT Error ΔU Increase value ΔV Voltage increase value (signal)

Claims (3)

In consumable electrode arc welding where the arc generation state and short circuit state are repeated between the consumable electrode and the base material, the constriction phenomenon of droplets, which is a precursor to the arc re-occurring from the short circuit state, is observed between the consumable electrode and the base material. This is detected when the change in voltage value or resistance value reaches the squeezing detection reference value, and when this squeezing phenomenon is detected, the welding current applied to the short-circuit load is suddenly reduced so that the arc is regenerated at a low current value. In the constriction detection control method of consumable electrode arc welding, which optimizes the constriction detection reference value so that the constriction detection time from the constriction phenomenon detection time to the arc re-occurrence time becomes a set value,
The squeezing detection time is detected and stored for each short circuit, and the number of the squeezing detection times for a predetermined number of past multiples from the stored current time is less than a predetermined minimum value. when the above number is decreased by decreasing values predetermined said squeezing detection reference value, said time stored the squeezing detection time is the number is greater than or equal to the maximum value number of predetermined at a predetermined maximum value or the Increase the squeezing detection reference value by a predetermined increase value , and repeat these processes for each short circuit .
A constriction detection control method for consumable electrode arc welding.   The constriction detection control method of consumable electrode arc welding, wherein the minimum value according to claim 1 is 0 μs. When the stored number of squeezing detection times is not more than the minimum value or more than the minimum number, or when the number of stored squeezing detection times or more is not less than the maximum value, the number is stored. 3. The constriction detection control method for consumable electrode arc welding according to claim 1, wherein all the constriction detection times are reset once.

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