JP5808947B2 - Constriction detection control method for consumable electrode arc welding - Google Patents

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 circuit period and reducing welding current to improve welding quality.

  FIG. 5 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 of the welding current Iw for energizing the consumable electrode (hereinafter referred to as welding wire 1), and FIG. 4B shows the welding voltage applied between the welding wire 1 and the base material 2. FIG. The time change of Vw is shown, The figure (C)-(E) shows the mode of the transfer 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 a 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, by detecting a change in resistance value between the welding wire 1 and the base material 2 during the short-circuit period Ts, it is possible to detect the occurrence and progress of the necking phenomenon. This change in resistance value can be calculated by dividing the welding voltage Vw by the welding current Iw. Further, as shown in FIG. 9A, the change in the welding current Iw during the short necking period is small. 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, the rate of change (differential value) of the resistance value or the welding voltage value Vw during the short-circuit period Ts is calculated, and the necking is achieved by reaching the predetermined necking detection reference value Vtn. There is a way to detect. 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 re-occurrence 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 reference 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 purpose, various welding power sources have been proposed in which a constriction detection control method for detecting the occurrence of the above-described constriction phenomenon and reducing the welding current Iw to reduce the current value Ia at the time of arc re-generation is added. . Hereinafter, this prior art will be described.

  FIG. 6 is a block diagram of a welding apparatus equipped with a conventional necking detection control method. 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 reference value setting circuit VTN outputs a squeezing detection reference value signal Vtn. The squeezing detection circuit ND receives the squeezing detection reference value signal Vtn and the welding voltage Vw, and becomes a high level when the voltage rise value ΔV during the short circuit reaches the value of the squeezing detection reference value signal Vtn as described above. When the arc is regenerated, a squeezing detection signal Nd that becomes a low level is output. Therefore, the squeezing detection time Tn is a period during which the squeezing detection signal Nd is at a high level. As described above, the squeezing detection signal Nd is changed to the high level when the differential value of the welding voltage Vw during the short circuit period reaches the value of the squeezing detection reference value signal Vtn set corresponding thereto. Also good. Further, the welding current Iw is input in addition to the welding voltage Vw, the resistance value of the droplet is calculated by dividing the welding voltage Vw by the welding current Iw, and a differential value of this resistance value is set correspondingly. When the value of the squeezing detection reference value signal Vtn is reached, the squeezing detection signal Nd may be changed to a high level. 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. 7 is a timing chart of each signal of the welding apparatus. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the squeezing detection signal Nd, (D) ) 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 welding apparatus for normal 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 reference 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. The value of the resistor R is set so that the decrease rate of the welding current is about 1000 to 50000 A / ms. In the case of a normal welding apparatus in which the resistor R is not inserted, the reduction rate of the welding current is about 100 A / ms. As a means for rapidly reducing the welding current Iw when the constriction is detected, the method for inserting the resistor R into the current path has been described above. As another means, a capacitor is connected between the output terminals of the welding apparatus in parallel through the switching element, and when the constriction is detected, the switching element is turned on and a discharge current is supplied from the capacitor to rapidly increase the welding current Iw. There is also a method of decreasing (see, for example, Patent Document 1).

  In the above-described constriction detection control method, it is important to accurately detect the occurrence of constriction in order to increase the effect of suppressing the amount of spatter generated. The occurrence of the constriction and its progress vary depending on the welding conditions such as the type of shielding gas, the type of welding wire, the shape of the base material, the feeding speed of the welding wire, and the welding posture. For this reason, it is necessary to optimize the sensitivity for detecting the occurrence of constriction according to the welding conditions. The squeezing detection sensitivity can be adjusted by increasing or decreasing the squeezing detection reference value Vtn. That is, when the squeezing detection reference value Vtn is increased, the sensitivity is lowered, and conversely, when it is decreased, the sensitivity is increased. If the squeezing detection reference value Vtn is too large, the sensitivity will be too low, and the squeezing detection time Tn will be too short, and the welding current cannot be reduced sufficiently until the arc is regenerated. The effect is reduced. Conversely, if the squeezing detection reference value Vtn is too small, the sensitivity will be too high, and the above-described squeezing detection time Tn will be too long and the arc will not reoccur, making the welding state unstable. Therefore, it can be said that the squeezing detection time Tn is in the range of about 50 to 1000 μs when the squeezing detection reference value Vtn is set to an appropriate value.

  In the welding power source to which the necking detection control method is added as described above, the necking detection reference value Vtn is switched to an appropriate value in accordance with the shield gas selection signal, the welding wire selection signal, and the feed speed setting signal. I am doing so. However, in the actual welding process, the plurality of welding conditions described above are combined to determine an appropriate value for the squeezing detection reference value Vtn. Therefore, a function for automatically adjusting the squeezing detection reference value Vtn from the initial value to an appropriate value according to the welding process is required. Hereinafter, conventional techniques related to the automatic adjustment function (see, for example, Patent Documents 2 and 3) will be described.

  In the invention of Patent Document 2, a squeezing detection time Tn is detected for each short-circuit, a predetermined number of squeezing detection times Tn are stored from the present time, and each stored squeezing detection time Tn is equal to or less than a predetermined lower limit time. When the number is equal to or greater than a predetermined lower limit number, the squeezing detection reference value Vtn is decreased by a predetermined decrease value, and the number of stored squeezing detection times Tn is equal to or greater than a predetermined upper limit time. When the number is more than the number, the squeezing detection reference value Vtn is optimized by increasing the squeezing detection reference value Vtn by a predetermined increase value. Accordingly, each squeezing detection time Tn falls within an appropriate range between the lower limit time and the upper limit time, and the squeezing detection reference value Vtn can be optimized according to the welding conditions.

  In the invention of Patent Document 3, a squeezing detection time Tn is detected for each short circuit, and when the squeezing detection time Tn is equal to or longer than a predetermined upper limit time, it is determined that the squeezing is erroneously detected. It is optimized by increasing the value Vtn. In the invention of Patent Document 3, when the squeezing detection time Tn is equal to or longer than the upper limit time (when the sensitivity is too high), the squeezing detection reference value Vtn is increased to lower the sensitivity and optimize the squeezing. However, in the invention of Patent Document 3, when the squeezing detection time Tn is short (when the sensitivity is too low), the squeezing detection reference value Vtn cannot be optimized.

JP 2005-288540 A JP 2006-281219 A JP 2009-125760

  By applying the inventions of Patent Documents 2 and 3 described above, the squeezing detection reference value can be automatically optimized according to the welding conditions. By the way, when the feeding speed is relatively low (when the welding current average value is less than about 200 A), the droplet transfer form becomes a short-circuit transfer form, and the short-circuit period and the arc period are regularly repeated. The state of constriction is also stable. Under such circumstances, the squeezing detection reference value can be quickly converged to an appropriate value by the inventions of Patent Documents 2 and 3.

  However, when the feeding speed is relatively high (average welding current is about 200 A or more), the droplet transfer form becomes a globule transfer form, and short-circuiting occurs irregularly. Fluctuation increases. For this reason, a state occurs in which the squeezing detection time becomes equal to or longer than the upper limit time in the next short circuit in which the squeezing detection time is equal to or shorter than the lower limit time. When the inventions of Patent Documents 2 and 3 are applied when the variation in the constriction occurrence state is large as described above, the constriction detection reference value may fluctuate greatly and may not converge to an appropriate value. As a result, the effect of suppressing the amount of spatter is reduced, and the welding state may become unstable due to the constriction detection control. In addition to the above cases, welding conditions with large fluctuations in the state of occurrence of constriction include cases where the welding speed is high, the welding wire material is stainless steel, the wire protrusion length is relatively long, etc. .

  Therefore, an object of the present invention is to provide a constriction detection control method for consumable electrode arc welding that can quickly converge the constriction detection reference value to an appropriate value even under welding conditions in which the variation of the constriction occurrence state is large. .

In order to solve the above-described problems, the invention of claim 1
In consumable electrode arc welding that repeats the arc generation state and the short circuit state between the consumable electrode and the base material, the constriction phenomenon of the droplets, which is a precursor of the arc re-occurring from the short circuit state, is detected between the consumable electrode and the base material. The change in the voltage value or resistance value during the period is detected by reaching the squeezing detection reference value, and when this squeezing phenomenon is detected, the welding current flowing to the short-circuit load is reduced and the arc is regenerated at a low current value. In the constriction detection control method of consumable electrode arc welding that controls the output to
A squeezing detection time from the time of detection of the squeezing phenomenon to the time of reoccurrence of the arc is detected for each short circuit. When this squeezing detection time is less than a predetermined lower limit time, 1 is subtracted from the counter value, and the squeezing detection time is When it is equal to or longer than a predetermined upper limit time that is longer than the lower limit time, 1 is added to the counter value,
When the counter value reaches a negative reference value that is a predetermined negative value, the squeezing detection reference value is decreased by a predetermined decrease value, and the counter value is reset to 0, so that the counter value is determined in advance. When the positive reference value, which is a positive value, is reached, the squeezing detection reference value is increased by a predetermined increase value and the counter value is reset to 0, and the squeezing detection reference value is continuously corrected during welding. And
When a short circuit occurs within a predetermined period from when the arc is regenerated after the previous short circuit is opened, the counter value is not increased or decreased based on the constriction detection time of the short circuit,
This is a constriction detection control method for consumable electrode arc welding.

According to a second aspect of the present invention, the decrease value is changed according to a time from when the counter value is reset to 0 until the minus reference value is reached, and the increase value is reset to 0. Change according to the time from the point in time until the positive reference value is reached,
The constriction detection control method for consumable electrode arc welding according to claim 1.

The invention of claim 3 does not increase or decrease the counter value based on the squeezing detection time of this short circuit when a short circuit occurs within a predetermined period from the time when the previous short circuit was opened and the arc was regenerated. ,
The constriction detection control method for consumable electrode arc welding according to claim 1 or 2.

  According to the present invention, the tendency of the squeezing detection time is discriminated by the counter value, and the squeezing detection reference value is corrected when the tendency becomes a predetermined state or more. That is, when the counter value is equal to or less than the negative reference value, it is determined that the squeezing detection time is in a state shorter than the appropriate range as a tendency, and the squeezing detection reference value is decreased to increase the sensitivity. When the counter value is equal to or greater than the plus reference value, it is determined that the squeezing detection time tends to be longer than the appropriate range, and the squeezing detection reference value is increased to lower the sensitivity. By doing so, it is possible to optimize the squeezing detection reference value quickly and stably even under welding conditions in which the variation of the squeezing occurrence state is large. For this reason, the effect of suppressing the amount of spatter generated can be increased, and the welding state can also be stabilized.

It is a block diagram of the welding apparatus for implementing the constriction detection control method of consumable electrode arc welding which concerns on Embodiment 1 of this invention. It is a block diagram of the welding apparatus for enforcing the constriction detection control method of consumable electrode arc welding which concerns on Embodiment 2 of this invention. FIG. 3 is a diagram illustrating an example of a decrease value correction function built in a decrease value setting correction circuit DDS of FIG. 2. It is a block diagram of the welding apparatus for enforcing the constriction detection control method of the consumable electrode arc welding which concerns on Embodiment 3 of this invention. In a prior art, it is a figure which shows the electric current and voltage waveform and droplet transfer in consumable electrode arc welding which repeats the short circuit period Ts and the arc period Ta. It is a block diagram of the welding apparatus for enforcing the necking detection control method of a prior art. It is a timing chart of each signal in the welding apparatus of FIG.

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

[Embodiment 1]
In the squeezing detection control method according to Embodiment 1 of the present invention, a squeezing detection time Tn is detected for each short circuit. When this squeezing detection time Tn is equal to or less than the lower limit time Lt, 1 is subtracted from the counter value Cn, and the upper limit is set. When the time is equal to or longer than the time Ht, 1 is added to the counter value Cn. When the counter value reaches the minus reference value Lc, the squeezing detection reference value Vtn is decreased by the decrease value Δd and the counter value Cn is reset to 0. When the counter value Cn reaches the plus reference value Hc, the squeezing detection reference value Vtn is increased by the increase value Δu and the counter value Cn is reset to 0. During the welding, the squeezing detection reference value Vtn is continuously corrected. Do it. Hereinafter, the first embodiment will be described.

  1 is a block diagram of a welding apparatus for carrying out a constriction detection control method for consumable electrode arc welding according to Embodiment 1 of the present invention. This figure corresponds to FIG. 6, the same reference numerals are given to the same blocks, and the description thereof is omitted. In the figure, a counter circuit CN, a counter value discriminating circuit CD, a decrease value setting circuit DD and an increase value setting circuit DU indicated by broken lines in FIG. 6 are added, and the necking detection reference value setting circuit VTN of FIG. The detection reference value setting correction circuit VTNS is replaced. Hereinafter, these blocks will be described with reference to FIG.

  The counter circuit CN receives the squeezing detection signal Nd and the reset signal Rs, measures the time during which the squeezing detection signal Nd is at a high level (squeezing detection time Tn), and the squeezing detection time Tn is a predetermined lower limit. When the time is less than the time Lt, 1 is subtracted from the counter value. When the squeezing detection time Tn is greater than or equal to a predetermined upper limit time Ht, 1 is added to the counter value, and the counter value signal Cn is output. The counter circuit CN resets the counter value to 0 when the reset signal Rs is input. The value of the counter value signal Cn becomes the counter value. The counter value has an initial value of 0 at the start of welding. Naturally, the upper limit time Ht is set to be longer than the lower limit time. The lower limit time Lt is set in a range of about 0 to 200 μs. Further, the upper limit time Ht is set in a range of about 500 to 800 μs. These set values are determined by experiments so as to be appropriate values according to the welding conditions.

  The decrease value setting circuit DD outputs a predetermined decrease value signal Δd. The increase value setting circuit DU outputs a predetermined increase value signal Δu. The counter value discriminating circuit CD receives the decrease value signal Δd, the increase value signal Δu, and the counter value signal Cn, and when the value of the counter value signal Cn becomes equal to or less than a predetermined negative reference value Lc, The signal Δd is output as the correction signal Δud and the reset signal Rs is output. When the value of the counter value signal Cn becomes equal to or greater than a predetermined plus reference value, the increase value signal Δu is output as the correction signal Δud and the reset signal. Rs is output. The minus reference value Lc is set to a negative value, for example, in a range of about −5 to −20. The positive reference value Hc is set to a positive value, for example, in the range of about +5 to +20. These set values are determined to be appropriate values by experiments in accordance with the magnitude of variation in the constriction occurrence state. The absolute values of the minus reference value Lc and the plus reference value Hc are not necessarily the same value. The value of the decrease value signal Δd is set to a negative value, and the absolute value thereof is set to a range of about 10 to 30% of the initial value Vtn0 of the squeezing detection reference value, for example. The value of the increase value signal Δu is set to a positive value, for example, in a range of about 10 to 30% of the initial value Vtn0 of the squeezing detection reference value. Since these set values correspond to the gains of the feedback system, they are set by experiments in consideration of the transient response and steady stability in the corrected state of the squeezing detection reference value Vtn.

  The necking detection reference value setting correction circuit VTNS receives the correction signal Δud as described above, performs correction based on the value of the correction signal Δud, and outputs a necking detection reference value signal Vtn. Vtn = Vtn0 + ΣΔud. Here, Vtn0 is an initial value. Further, Δud is added every time the correction signal Δud is input.

To summarize the operation of the above block, the method for correcting the squeezing detection reference value Vtn is as follows.
(1) Constriction detection time Tn is detected for each short circuit.
(2) Cn-1 is performed when Tn ≦ Lt, Cn + 0 is performed when Lt <Tn <Ht, and Cn + 1 is performed when Tn ≧ Ht. Here, Lt is a lower limit time, Ht is an upper limit time, and Cn is a counter value. The counter value Cn is reset to 0 at the start of welding.
(3) When Cn ≦ Lc, the correction signal Δud = Δd is output and Cn is reset to 0. When Cn ≧ Hc, the correction signal Δud = Δu is output and Cn is reset to zero. Here, Lc is a negative reference value, Hc is a positive reference value, Δd is a decrease value, and Δu is an increase value.
(4) Necking detection reference value Vtn = Vtn0 + ΣΔud is performed to correct the squeezing detection reference value Vtn. Here, Vtn0 is an initial value.
(5) The correction operations (1) to (4) are continued during welding.

  As described above, the necking detection time Tn for each short circuit varies greatly under welding conditions in which the variation of the necking occurrence state is large. The squeezing detection time Tn in the n-th short circuit is less than or equal to the lower limit time Lt, the squeezing detection time Tn in the (n + 1) th short circuit is greater than or equal to the upper limit time Ht, and the squeezing detection time Tn in the (n + 2) th short circuit is the lower limit time Lt. And an upper limit time Ht. When the above-described prior art is applied when the variation in the squeezing detection time Tn is large as described above, the squeezing detection reference value Vtn largely fluctuates due to excessive reaction to the variation in the squeezing detection time Tn. In such a state, the welding state was unstable.

  In contrast, according to the first embodiment described above, the squeezing detection reference value Vtn is not directly corrected for the squeezing detection time Tn for each short circuit. The tendency of the squeezing detection time Tn is discriminated by the counter value Cn, and the squeezing detection reference value Vtn is corrected when the tendency becomes a predetermined state or more. That is, when the counter value Cn becomes equal to or less than the negative reference value Lc, it is determined that the squeezing detection time Tn tends to be shorter than the appropriate range, and the squeezing detection reference value Vtn is decreased to increase the sensitivity. ing. When the counter value Cn exceeds the plus reference value Hc, it is determined that the squeezing detection time Tn tends to be longer than the appropriate range, and the squeezing detection reference value Vtn is increased to lower the sensitivity. Yes. By doing so, it is possible to optimize the squeezing detection reference value Vtn quickly and stably even under welding conditions in which the variation of the squeezing occurrence state is large. For this reason, the effect of suppressing the amount of spatter generated can be increased, and the welding state can also be stabilized.

[Embodiment 2]
In the squeezing detection control method according to the second embodiment of the present invention, the decrease value Δd is set to the negative reference value arrival time Td from when the counter value Cn is reset to 0 until the negative reference value Lc is reached. The increase value Δu is changed according to the plus reference value arrival time Tu from when the counter value Cn is reset to 0 until the plus reference value Hc is reached. Hereinafter, the second embodiment will be described.

  FIG. 2 is a block diagram of a welding apparatus for carrying out the constriction detection control method for consumable electrode arc welding according to the second embodiment. FIG. 6 corresponds to FIG. 6 and FIG. 1 described above, and the same reference numerals are given to the same blocks, and descriptions thereof are omitted. In FIG. 1, a reference value arrival time measurement circuit TUD indicated by a broken line in FIG. 1 is added, the decrease value setting circuit DD in FIG. 1 is replaced with a decrease value setting correction circuit DDS indicated by a broken line, and the increase value setting circuit DU is indicated by a broken line. Is replaced with an increase value setting correction circuit DUS. Hereinafter, these blocks will be described with reference to FIG.

  The reference value arrival time measurement circuit TUD receives the counter value signal Cn, measures the time from when the value of the counter value signal Cn is reset to 0 to reach the negative reference value Lc, and measures the negative reference value arrival time signal. It outputs as Td, measures the time from when the value of the counter value signal Cn is reset to 0 until it reaches the positive reference value Hc, and outputs it as a positive reference value arrival time signal Tu.

  The decrease value setting correction circuit DDS receives the minus reference value arrival time signal Td as an input, and outputs a decrease value signal Δd calculated according to a predetermined decrease value correction function. The increase value setting correction circuit DUS receives the plus reference value arrival time signal Tu as an input and outputs an increase value signal Δu calculated according to a predetermined increase value correction function. An example of the decrease value correction function is shown in FIG.

  FIG. 3 is a diagram illustrating an example of a decrease value correction function that calculates the decrease value Δd with the minus reference value arrival time Td as an input. In the figure, the horizontal axis represents the negative reference value arrival time Td (ms), and the vertical axis represents the decrease value Δd (V). As shown in the figure, the decrease value Δd is a constant value of −0.1 V in the range of 0 ms ≦ Td <10 ms, and the range of 10 ms ≦ Td <50 ms changes to a straight line that rises to the right. The range of Td is a constant value of -0.01V. That is, as the negative reference value arrival time Td becomes longer, the absolute value of the decrease value Δd changes so as to become substantially smaller. The reason for this is as follows. When the negative reference value arrival time Td is short, the short-circuiting in which the squeezing detection time Tn is less than or equal to the lower limit time Lt frequently occurs. Such a state is when the squeezing detection reference value Vtn is considerably larger than the appropriate value. Therefore, the absolute value of the decrease value Δd is increased so that the squeezing detection reference value Vtn is significantly reduced. In the correction control system for the squeezing detection reference value Vtn, the gain is increased. This speeds up the transient response. On the other hand, when the negative reference value arrival time Td is long, a short circuit in which the squeezing detection time Tn is less than or equal to the lower limit time Lt occurs occasionally. Such a state is when the squeezing detection reference value Vtn is slightly larger than the appropriate value. Therefore, the absolute value of the decrease value Δd is reduced to make the squeezing detection reference value Vtn small. In the correction control system for the squeezing detection reference value Vtn, the gain is reduced. Thereby, steady stability is made favorable. The change curve in the figure is an example, and may be changed to a curved line, a straight line, or a staircase.

  The increase value correction function is also the same as that in FIG. However, the horizontal axis is replaced with the plus reference value arrival time Tu (ms), and the vertical axis is replaced with the increase value Δu (V). Although the horizontal axis is the same, the increase value Δu on the vertical axis is a positive value. Therefore, the increase value Δu has the same absolute value as the decrease value Δd, but has a different sign. The effects are also the same as in FIG. Of course, the absolute value change curve may be set differently between the decrease value Δd and the increase value Δu. The decrease value correction function and the increase value correction function are set to appropriate functions according to the magnitude of the variation in the constriction occurrence state. This setting is performed by experiment.

  According to the second embodiment described above, the decrease value is changed according to the time from when the counter value is reset to 0 to the time when it reaches the negative reference value, and the increase value is determined from the time when the counter value is reset to 0. Change according to the time to reach the positive reference value. Thereby, in addition to the effect of the first embodiment, the gain in the correction control system for the squeezing detection reference value can be made variable, so that the transient response and the steady stability can be improved.

[Embodiment 3]
In the constriction detection control method according to the third embodiment of the present invention, in addition to the first and second embodiments described above, a short circuit occurs within a predetermined period Ti from the time when the previous short circuit is opened and the arc is regenerated. In this case, the counter value Cn is not increased or decreased based on the short circuit squeezing detection time Tn. The third embodiment will be described below.

  FIG. 4 is a block diagram of a welding apparatus for carrying out a constriction detection control method for consumable electrode arc welding according to Embodiment 3 of the present invention. 6 corresponds to FIG. 6 and FIG. 1, and the same reference numerals are given to the same blocks, and the description thereof is omitted. In the figure, a short circuit / arc determination circuit SA and a double short circuit determination circuit SS indicated by broken lines in FIG. 1 are added, and the counter circuit CN of FIG. 1 is replaced with a second counter circuit CN2 indicated by broken lines. Hereinafter, these blocks will be described with reference to FIG.

  The short-circuit / arc discrimination circuit SA receives the welding voltage Vw, and when this value is less than a predetermined short-circuit / arc discrimination reference value Vta, the short-circuit / arc discrimination circuit SA determines that it is a short-circuit period and becomes a high level. The short circuit / arc determination signal Sa which becomes low level is determined and is output. This short circuit / arc discrimination reference value Vta is set to about 10V. The double short-circuit determination circuit SS receives this short-circuit / arc determination signal Sa, and when this signal changes to a high level (short-circuit), this signal changes from the previous change to a low level (arc) to the current high level ( The time (the length of the arc period) until the point of change to (short circuit) is measured, and when this measured time is less than the predetermined period Ti, it changes to the High level, and when it is more than that, it changes to the Low level. A short circuit determination signal Ss is output. That is, when the current short circuit occurs within the predetermined period Ti from the time when the previous short circuit was opened and the arc re-generated, it is determined that two short circuits (double short circuit) have occurred over a short arc period. Then, the double short-circuit determination signal Ss is set to the high level. The predetermined period Ti is set to about 100 to 500 μs, for example. This value is set by experiment so as to be an appropriate value according to the welding method, the type of welding wire, the feeding speed, and the like.

The second counter circuit CN2 receives the squeezing detection signal Nd, the reset signal Rs, and the double short-circuit determination signal Ss as input, and measures the time (the squeezing detection time Tn) when the squeezing detection signal Nd is at the high level. When the short circuit determination signal Ss is at the Low level and the squeezing detection time Tn is equal to or less than the predetermined lower limit time Lt, 1 is subtracted from the counter value, and when the squeezing detection time Tn is equal to or greater than the predetermined upper limit time Ht. 1 is added to the counter value, and the counter value signal Cn is output. The second counter circuit CN2 resets the counter value to 0 when the reset signal Rs is input. The value of the counter value signal Cn changes as follows.
1) When Ss = Low level and Tn ≦ Lt, Cn is decremented by 1.
2) When Ss = Low level and Tn ≧ Ht, Cn is incremented by 1.
3) When Ss = Low level and Lt <Tn <Ht, Cn is not increased or decreased.
4) When Ss = High level, Cn is not increased or decreased regardless of the value of Tn.

  This figure is the addition of the invention of the third embodiment on the basis of FIG. 1 of the first embodiment, but the same applies when the invention of the third embodiment is added on the basis of FIG. 2 of the second embodiment. It is. As described above, in the third embodiment, unlike the first and second embodiments, when a double short circuit occurs, the counter value is not increased or decreased regardless of the squeezing detection time. As described above, the double short circuit is a state in which the next short circuit occurs within a short predetermined period Ti after the previous short circuit is opened and the arc is regenerated. That is, a short circuit occurs again immediately after an instantaneous arc for a short period of time. Such double shorts sometimes occur due to various factors such as irregular movement of the weld pool, fluctuations in the feed rate of the welding wire, and the state of the arc when the arc is regenerated. Since the double short-circuit occurs after a short instantaneous arc, unlike the normal short-circuit occurrence, there is no time for the tip of the welding wire to melt and form droplets. For this reason, when a double short circuit occurs, it short-circuits with a molten pool in the state where the tip of a welding wire has hardly melted. In such a short circuit, the constriction is formed in the droplet, and the droplet does not move in the normal state. Instead, the welding current is applied to the protruding part of the welding wire and heat is generated by Joule heat, so that the arc is regenerated. It becomes a state to do. Therefore, if the counter value is increased or decreased based on the squeezing detection time Tn at the time of such a double short-circuit, the squeezing detection reference value correction control system is destabilized. In order to prevent this, the counter value is not increased or decreased during the double short circuit regardless of the squeezing detection time.

  According to the above-described third embodiment, when a short circuit (double short circuit) occurs within a predetermined period from the time when the previous short circuit is opened and the arc is regenerated, the counter value is determined based on the constriction detection time of the short circuit. Do not increase or decrease. Thereby, it is possible to prevent the squeezing detection reference value correction control system from becoming unstable due to the occurrence of a double short circuit. Therefore, the squeezing detection reference value can be quickly and stably converged to an appropriate value.

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 1b Constriction 2 Base material 2a Weld pool 3 Arc CD Counter value discrimination circuit CN Counter circuit Cn Counter value (signal)
CN2 Second counter circuit DD Decrease value setting circuit DDS Decrease value setting correction circuit DR Drive circuit Dr Drive signal DU Increase value setting circuit DU Increase value setting correction circuit Hc Plus reference value Ht Upper limit time Ia Arc regeneration current value Iw Welding current Lc Negative reference value Lt Lower limit time ND Constriction detection circuit Nd Constriction detection signal PS Welding power supply R Resistor Rs Reset signal SA Short circuit / arc determination circuit Sa Short circuit / arc determination signal SS Double short circuit determination circuit Ss Double short circuit determination signal Ta Arc period Td Negative reference value arrival time (signal)
Ti Predetermined period Tn Neck detection time TR Transistor Ts Short circuit period Tu Plus reference value arrival time (signal)
TUD Reference value arrival time measurement circuit Vs Short-circuit voltage value Vta Short-circuit / arc discrimination reference value VTN Detection reference value setting circuit Vtn Neck detection reference value (signal)
Vtn0 Neck detection reference value initial value VTNS Detection reference value setting correction circuit Vw Welding voltage Δd Decrease value (signal)
Δu increase value (signal)
Δud Correction signal ΔV Voltage rise value

Claims (2)

In consumable electrode arc welding that repeats the arc generation state and the short circuit state between the consumable electrode and the base material, the constriction phenomenon of the droplets, which is a precursor of the arc re-occurring from the short circuit state, is detected between the consumable electrode and the base material. The change in the voltage value or resistance value during the period is detected by reaching the squeezing detection reference value, and when this squeezing phenomenon is detected, the welding current flowing to the short-circuit load is reduced and the arc is regenerated at a low current value. In the constriction detection control method of consumable electrode arc welding that controls the output to
A squeezing detection time from the time of detection of the squeezing phenomenon to the time of reoccurrence of the arc is detected for each short circuit. When this squeezing detection time is less than a predetermined lower limit time, 1 is subtracted from the counter value, and the squeezing detection time is When it is equal to or longer than a predetermined upper limit time that is longer than the lower limit time, 1 is added to the counter value,
When the counter value reaches a negative reference value that is a predetermined negative value, the squeezing detection reference value is decreased by a predetermined decrease value, and the counter value is reset to 0, so that the counter value is determined in advance. When the positive reference value, which is a positive value, is reached, the squeezing detection reference value is increased by a predetermined increase value and the counter value is reset to 0, and the squeezing detection reference value is continuously corrected during welding. And
When a short circuit occurs within a predetermined period from when the arc is regenerated after the previous short circuit is opened, the counter value is not increased or decreased based on the constriction detection time of the short circuit,
A constriction detection control method for consumable electrode arc welding. The decrease value is changed according to the time from when the counter value is reset to 0 to the time when the minus reference value is reached, and the increase value is changed from the time when the counter value is reset to 0 to the plus reference value. Change according to the time to reach,
The constriction detection control method of consumable electrode arc welding according to claim 1.

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