JP4767508B2 - 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-circuiting period and rapidly reducing a welding current to improve welding quality.

  FIG. 5 is a diagram showing current / voltage waveforms and droplet transfer in consumable electrode arc welding (hereinafter also referred to as short-circuit transfer 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 progresses rapidly, and as shown to the same figure (E) at the time t3, the droplet 1a will detach | leave from the welding wire 1 to the molten pool 2a, and the arc 3 will generate | occur | produce again.

  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 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 of the constriction phenomenon can be detected by detecting the change in the 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 period 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, the rate of change (differential value) of the resistance value or welding voltage value Vw during the short circuit period Ts is calculated, and it is determined that this rate of change has reached a predetermined necking detection reference value. Constriction detection is performed. As a second method, as shown in FIG. 5B, a voltage rise value ΔV from a stable short-circuit voltage value Vs before the occurrence of constriction during the short-circuit period Ts is calculated, and this voltage rise at time t2. Necking is detected by determining that the value ΔV has reached a predetermined squeezing detection reference value Vtn. In the following description, the case where the constriction detection method is the second method will be described. However, the first method and other methods 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. A period from detection of the occurrence of squeezing at times t2 to t3 to reoccurrence of the arc is hereinafter referred to as a squeezing detection period Tn.

  In short-circuit transfer welding, if the current value when arc 3 is regenerated at time t3 (hereinafter referred to as welding current value Ia when arc is regenerated) is a large current value, the pressure (arc) from arc 3 to molten pool 2a Force) becomes very large and a large amount of spatter is generated. That is, the amount of spatter generated increases substantially in proportion to the value of the welding current value Ia when the arc is regenerated. Therefore, in order to suppress the occurrence of spatter, it is necessary to reduce the welding current value Ia when the arc is regenerated. As a method for this purpose, various welding power sources have been proposed in which a current reduction control at the time of squeezing detection is added to detect the occurrence of the above-mentioned squeezing phenomenon and reduce the welding current Iw rapidly to reduce the welding current value Ia when the arc reoccurs. Has been. Hereinafter, these conventional techniques will be described.

[Prior Art 1 (Patent Document 1)]
FIG. 6 is a block diagram of a welding power source with a current suddenly decreasing function at the time of detection of squeezing described in Patent Document 1. 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 becomes a high level when detecting that the squeezing of the droplet has occurred during the short-circuiting period by receiving the welding voltage Vw between the + terminal and the − terminal as an input. . The drive circuit DR outputs a drive signal Dr that turns on the transistor TR when the squeezing detection signal Nd is at a low level. Therefore, the transistor TR is turned off when the squeezing detection signal Nd is at a high level (during the squeezing detection period Tn).

  FIG. 7 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 period Tn1 from time t2 to t3, as shown in FIG. 10C, the squeezing detection signal Nd is at the low level, so that the driving is performed as shown in FIG. The signal Dr becomes a high level. As a result, the transistor TR is turned on, which is the same as the welding power source 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. At the same time, the output of the welding power source PS is stopped. 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 opened 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. At the same time, the output of the welding power source PS is started to return to normal consumable electrode arc welding control. By this operation, the welding current value Ia1 at the time of arc re-generation at the time of arc re-generation (time t3) can be reduced, and the occurrence of spatter can be suppressed.

[Prior Art 2 (Japanese Patent Application No. 2004-146108)]
FIG. 8 is a block diagram of a welding power source with a current suddenly decreasing function at the time of detection of squeezing in Prior Art 2. Hereinafter, each circuit block will be described with reference to FIG.

  The welding power source PS is a general welding power source for consumable electrode arc welding. A discharge circuit composed of a series circuit of a capacitor C and a discharge switching element TRD is connected between the + terminal and the − terminal of the welding power source PS. The discharge current Id from this discharge circuit is energized in the direction opposite to the welding current Iw during the squeezing detection period. The capacity of the capacitor C is set to a value at which the discharge current Id has a substantially peak value when the arc is regenerated. A charging circuit including a series circuit of a charging power source E and a charging switching element TRC is connected in parallel with the capacitor C.

  The squeezing detection control circuit ND receives the welding voltage Vw as an input, detects the occurrence of squeezing of the droplets as the voltage rises, and outputs a squeezing detection signal Nd that assumes a high level. The charge / discharge drive circuit DRA receives the squeezing detection signal Nd as an input, and turns off the charging switching element TRC when the squeezing detection signal Nd becomes a high level, or when a predetermined time has elapsed since then. Then, the charging drive signal Drc for turning on the charging switching element TRC is output. At the same time, the charge / discharge drive circuit DRA receives the squeezing detection signal Nd as an input, and turns on the discharge switching element TRD when the squeezing detection signal Nd becomes a high level, or at a time when the squeezing detection signal Nd becomes a low level or after that. When the time has elapsed, a discharge drive signal Drd for turning off the discharge switching element TRD is output.

  FIG. 9 is a timing chart of each signal of the welding power supply with a current sudden decrease function at the time of detecting the squeezing. (A) is the welding current Iw, (B) is the welding voltage Vw, (C) is the squeezing detection signal Nd, (D) is the charge drive signal Drc (E) ) Shows the discharge drive signal Drd, (F) shows the discharge current Id, and (G) shows the time change of the voltage Vc across the capacitor. Hereinafter, a description will be given with reference to FIG.

  In the figure, during a period other than the squeezing detection period Tn1 at times t2 to t3, the squeezing detection signal Nd is at a low level as shown in FIG. The drive signal Drd is at a low level. As a result, the discharge switching element TRD is turned off, so that the welding current Iw is the same as the welding power source for normal consumable electrode arc welding, as shown in FIG.

  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 the squeezing detection reference value Vtn, and the squeezing of the droplets has occurred. If it is determined that it has occurred, the squeezing detection signal Nd becomes High level as shown in FIG. In response to this, as shown in FIG. 4D, the charging drive signal Drc is at the low level, so that the charging switching element TRC is turned off. At the same time, as shown in FIG. 5E, the discharge drive signal Drd is at a high level, so that the discharge switching element TRD is turned on. Therefore, as shown in FIG. 5F, the discharge current Id is supplied from the capacitor C in the opposite direction to the welding current Iw shown in FIG. As shown by the dotted lines at times t2 to t3 in FIG. 5A, the output current Io is reduced only slightly in a short time by the action of a DC inductor having a large inductance value in the welding power source PS. Since the value obtained by subtracting the discharge current Id from the output current Io becomes the welding current Iw, the welding current Iw rapidly decreases. When the short circuit is opened and the arc is regenerated at time t3, the welding voltage Vw becomes equal to or higher than the 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 charging drive signal Drc becomes the High level as shown in FIG. For this reason, as shown in FIG. 5G, the voltage Vc across the capacitor is charged by the charging power source E and gradually increases. At the same time, as shown in FIG. 5E, the discharge drive signal Drd is at the low level, so that the discharge switching element TRD is turned off. For this reason, the discharge current Id is cut off as shown in FIG. 5F, so that the welding current Iw becomes the same as the output current Io and the welding current Iw increases as shown in FIG. To do. By this operation, the welding current value Ia1 at the time of arc re-generation at the time of arc re-generation (time t3) can be reduced, and the occurrence of spatter can be suppressed.

[Prior Art 3 (Patent Document 2)]
FIG. 10 is a time change diagram of the welding current Iw and the welding voltage Vw when the voltage listing characteristic X during the constriction generation period in FIGS. 7 and 9 is changed. The voltage rise characteristic X is greatly influenced by the progress state of the constriction of the droplet. For example, when the welding conditions such as the material, diameter, welding joint, welding posture, welding speed, wire protrusion length, etc. of the welding wire change, the voltage rise characteristic X changes. In this case, if the squeezing detection reference value Vtn is a constant value, the squeezing detection timing at time t2 is shifted as shown in FIG. As a result, the constriction detection period may be shortened from Tn1 to Tn2, and the arc is regenerated in the state of Ia2 without reducing the welding power source Iw to Ia1 as shown in FIG. As described above, if the welding current value at the time of arc re-occurrence becomes larger than Ia1 in Ia2, the effect of reducing spatter is reduced accordingly.

  Conversely, if the voltage rise characteristic X changes and the squeezing detection period becomes too long, the welding current Iw may decrease to zero. In this case, even if the constriction progresses and the droplet transfer is completed, the arc may not be regenerated. In order to solve such a problem, in the conventional technique 3, the time length of the squeezing detection period Tn is detected, and the squeezing detection reference value Vtn is changed so that the squeezing detection period Tn becomes a predetermined value. As a result, even if the welding conditions change and the voltage rise characteristic X changes, the squeezing detection reference value Vtn changes accordingly, and the squeezing detection period Tn becomes a substantially constant value. For this reason, since the welding current value Ia at the time of arc re-generation becomes a substantially constant value of a low current value, the effect of reducing the spatter remains large.

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

  FIG. 11 is a time change diagram of the welding current Iw and the welding voltage Vw corresponding to FIG. 10 described above when the inductance value of the cable increases. This figure shows a case where the control for making the squeezing detection period Tn of the prior art 3 constant is performed. The inductance value of the cable is an inductance value that is generated when a welding cable connecting the welding power source and the welding torch or the base material becomes long and the cable is routed. The large inductance value of the DC reactor built in the welding power source is about 50 to 100 μH. On the other hand, the inductance value of the cable is as high as 50 μH when it is large, and about 5 μH when it is small. Thus, the influence of the inductance value of the cable is large.

  In FIG. 10, as described above with reference to FIG. 10, the squeezing detection period Tn becomes a predetermined value even if the welding condition changes and the voltage rise characteristic X changes. However, if the inductance value of the cable changes to a large value at this time, the decrease characteristic Y of the welding current Iw becomes gentle as shown in FIG. Great value. As a result, the spatter reduction effect is reduced. On the other hand, when the inductance value of the cable becomes small, the current reduction characteristic Y becomes faster and the welding current Iw may become zero. As a result, there may be a case where the re-generation of the arc fails. Furthermore, even if the inductance value of the cable is large, if the target value of the squeezing detection period is lengthened in order to reduce the welding current value at the time of arc re-occurrence, the squeezing detection reference value should be lowered over all welding conditions. Will be higher. For this reason, the squeezing detection sensitivity may become unnecessarily high depending on the welding conditions, and the squeezing phenomenon may be erroneously detected.

  Therefore, in the present invention, even when the welding conditions and the inductance value of the cable described above change, it is possible to accurately detect the constriction phenomenon, and the welding current value at the time of arc re-generation is always maintained at a low value, thereby greatly increasing the occurrence of spatter. The present invention provides a constriction detection control method for consumable electrode arc welding that can be suppressed.

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. In the constriction detection control method of consumable electrode arc welding that controls the output so that the arc is regenerated in a state of a low current value that is rapidly reduced,
The welding power source has a selection part for selecting the test welding mode or the actual welding mode,
When the test welding mode is selected by the operator, the welding current value at the time of the arc regeneration is detected on the actual welding line in which the welding conditions and the inductance value of the cable are determined, and the welding current at the time of the arc regeneration is detected. An appropriate value is calculated by changing the squeezing detection reference value by feedback control so that the value is substantially equal to a predetermined current value at the time of arc regeneration,
When the actual welding mode is selected by an operator, the necking detection reference value is automatically fixed to an appropriate value calculated in the test welding mode, and necking detection control is performed.
This is a constriction detection control method for consumable electrode arc welding.

In addition, the second invention calculates an appropriate value of the squeezing detection reference value for each welding point by the test welding mode for each of a plurality of welding points, and when the actual welding mode is selected, the squeezing detection reference is calculated. The value is fixed to an appropriate value calculated for each welding point.
A constriction detection control method for consumable electrode arc welding according to the first aspect of the present invention.

According to the first invention , the necking detection reference value is optimized by the test welding mode , and when the actual welding mode is selected, the necking detection reference value is fixed to the appropriate value calculated in the test welding mode, Since the squeezing detection reference value does not change out of the stable control range due to disturbance during the work, more stable low spatter welding can be performed.

According to the second aspect of the invention , when welding a plurality of welding locations, the effect of the first aspect of the invention can be achieved by optimizing and fixing the necking detection reference value for each welding location.

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

[Embodiment 1]
The first embodiment of the present invention is a reference embodiment for explaining the present invention. In the constriction detection control, a welding current value Ia at the time of arc regeneration is detected, and this welding current value at the time of arc regeneration is detected. This is a constriction detection control method for consumable electrode arc welding in which the constriction detection reference value Vtn is changed so that Ia is substantially equal to a predetermined arc re-occurrence current set value Iar.

That is, the welding current value Ia at the time of arc regeneration at each short-circuit opening is detected, and an error amplification value ΔE from the preset current value Iar at the time of arc regeneration is calculated by the following equation.
ΔE = Gain · (Iar−Ia) (1) where Gain is a predetermined positive amplification factor.
Next, when the squeezing detection reference value for the (n-1) th short-circuit period is Vtn (n-1), the squeezing detection reference value Vtn (n) for the n-th short-circuiting period is calculated by the following equation.
Vtn (n) = Vtn (n-1) + ΔE = Vtn0 + ∫ΔE · dt (2) where Vtn0 is an initial value of a predetermined squeezing detection reference value, and integration continues during welding.
As described above, in the first embodiment, the welding current at the time of arc re-generation is not affected by the change of the voltage increase characteristic X accompanying the change of the welding conditions and the change of the current decreasing characteristic Y accompanying the change of the inductance value of the cable. The value Ia can always be maintained at the low current value arc current setting value Iar. For this reason, the spatter reduction effect can always be maximized.

  In the above equation (1), the error amplification value ΔE is calculated from only the error between the detected value of the welding current value Ia at the time of arc regeneration and the current setting value Iar at the time of arc regeneration that is the target value. In addition to this, a differential value of the error may be added. The same applies to the so-called P control, PI control or PID control in the feedback control of the welding current value when the arc is regenerated. In the above, if the welding conditions and the inductance value of the cable are determined, the above-described control causes the squeezing detection reference value Vtn to converge to an appropriate value for the welding location. The constriction detection reference value Vtn after convergence becomes a substantially constant value.

  FIG. 1 is a time change diagram of the welding current Iw and the welding voltage Vw when the inductance value of the cable described above in FIG. 11 increases. In the figure, the operation during the period other than the times t2 to t3 is the same as the normal consumable electrode arc welding described above with reference to FIG. Hereinafter, a description will be given with reference to FIG.

  In the figure, as the inductance value of the cable increases, the current decrease characteristic Y becomes gentle. However, since the squeezing detection reference value Vtn changes and converges to an appropriate value so that the welding current value Ia at the time of arc re-occurrence at time t3 becomes substantially equal to the current setting value Iar at the time of arc re-occurrence, the squeezing detection period reaches Tn3. become longer. For this reason, even if the current reduction characteristic Y becomes gentle, the welding current value Ia at the time of arc regeneration is substantially equal to the current setting value Iar at the time of arc regeneration at a low current value.

  Similarly, even when the welding condition changes and the voltage rise characteristic X changes, the squeezing detection reference value is set so that the welding current value Ia at the time of arc reoccurrence becomes substantially equal to the current setting value Iar at the time of arc reoccurrence accordingly. Vtn converges to an appropriate value.

  In the first embodiment, the maximum value of the squeezing detection reference value Vtn in a state in which the welding current value Ia at the time of arc regeneration is substantially equal to the current setting value Iar at the time of arc regeneration is the convergence value. Therefore, when the inductance value of the cable is within the normal range, the squeezing detection reference value Vtn becomes a large value. As the inductance value of the cable increases, the squeezing detection reference value Vtn decreases. The larger the value of the squeezing detection reference value Vtn, the lower the squeezing detection sensitivity. Therefore, when the inductance value of the cable is within the normal range, the squeezing detection sensitivity is low in the appropriate range, and the probability of false detection of the squeezing phenomenon due to the squeezing detection sensitivity being unnecessarily high is reduced.

  The block diagram of the welding power source for carrying out the first embodiment described above is obtained by replacing the squeezing detection control circuit ND with the circuit shown in FIG. Therefore, FIG. 2 is a block diagram of the squeezing detection control circuit ND according to the first embodiment. Hereinafter, a description will be given with reference to FIG.

  In this figure, the welding current Iw and the welding voltage Vw are input, the necking detection reference value is optimized, the necking phenomenon is accurately detected, and the necking detection signal Nd is output. The arc re-generation welding current value detection circuit IAD receives the welding current Iw, detects the arc re-generation welding current value, and outputs an arc re-generation welding current value detection signal Iad. The arc regeneration current setting circuit IAR outputs a predetermined arc regeneration current setting signal Iar. The error amplification circuit EA amplifies an error between the arc regeneration current setting signal Iar and the arc regeneration welding current value detection signal Iad, as shown in the equation (1), and an error amplification signal. ΔE is output. The squeezing detection reference value calculation circuit VTN receives the initial value Vtn0 and the error amplification signal ΔE, and outputs a squeezing detection reference value signal Vtn according to the above equation (2). The error amplification circuit EA and the squeezing detection reference value calculation circuit VTN optimize the squeezing detection reference value signal Vtn so that the welding current value detection signal Iad at the time of arc re-occurrence becomes substantially equal to the current setting signal Iar at the time of arc re-occurrence. .

  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. 5, the voltage increase value detection circuit DV receives the welding voltage detection signal Vd as an input, detects a voltage increase value from the short circuit voltage during the short circuit period, and outputs a voltage increase value detection signal ΔV. The squeezing comparison circuit CMN compares the voltage rise value detection signal ΔV with the squeezing detection reference value signal Vtn, and outputs a set signal St that becomes a high level 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 outputs a reset signal Rt that becomes a high level when Vd ≧ Vta. 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.

  In the above description, the case where the voltage increase value ΔV is used as the squeezing detection method has been described. However, as described above, the same applies even when the rate of change of the resistance value or the welding voltage value during the short circuit period is used. 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. 6 and 8 can be used.

[Embodiment 2]
In the second embodiment of the present invention, test welding is performed by the constriction detection control method for consumable electrode arc welding according to the first embodiment, and an appropriate value of the constriction detection reference value Vtn is calculated. In actual welding, this constriction detection reference value is calculated. This is constriction detection control for consumable electrode arc welding in which Vtn is fixed to an appropriate value calculated by test welding and constriction detection control is performed.

  That is, in the actual welding line in which the welding conditions and the inductance value of the cable are determined, test welding is performed by the squeezing detection control method described in the first embodiment. As a result of this test welding, the squeezing detection reference value Vtn converges to an appropriate value for this welding point. In carrying out the work, welding is performed with the squeezing detection reference value Vtn fixed to the above-mentioned appropriate value. If the welding line conditions and the welding location of the workpiece are determined, the welding conditions and the inductance value of the cable are determined. Therefore, once test welding is performed and the squeezing detection reference value Vtn is optimized once, good squeezing detection control can always be performed.

  In the second embodiment, since the squeezing detection reference value Vtn is fixed to an appropriate value at the time of construction, there is a possibility that the squeezing detection reference value is set out of the stable control range due to disturbance and trouble that the welding quality deteriorates may occur. Becomes lower.

  FIG. 3 is a block diagram of the squeezing detection control circuit ND according to the second embodiment. This figure is used in place of the constriction detection control circuit ND of FIG. In the figure, the same blocks as those in FIG. Hereinafter, blocks indicated by dotted lines different from those in FIG. 2 will be described.

  The welding mode selection circuit TM outputs a welding mode selection signal Tm corresponding to the welding mode selected from the test welding mode or the actual welding mode. The second squeezing detection reference value calculation circuit VTN2 outputs the squeezing detection reference value signal Vtn calculated by the above equation (2) when the welding mode selection signal Tm is the test welding mode, and test welding when the welding mode selection signal Tm is the actual welding mode. A squeezing detection reference value signal Vtn having a convergence value (appropriate value) at the time is output.

  An appropriate value of the squeezing detection reference value may be calculated as an average value of the squeezing detection reference values calculated for each short circuit during test welding.

[Embodiment 3]
Embodiment 3 of the present invention is a constriction detection control method for consumable electrode arc welding described in Embodiment 2, in which test welding is performed for each of a plurality of welding locations, and an appropriate value of the necking detection reference value Vtn for each welding location is determined. This is a constriction detection control method for consumable electrode arc welding in which the constriction detection reference value Vtn is calculated and fixed to an appropriate value calculated for each welding point in actual welding.

  That is, when there are a plurality of welding locations in one workpiece, or when there are a plurality of types of workpieces and a plurality of welding locations, test welding is performed at each welding location and the necking detection reference value Vtn at each welding location. The convergence value (appropriate value) is calculated and stored. At the time of execution, the squeezing detection reference value Vtn is called and fixed to the appropriate value for each welding point calculated by the above test welding.

  In the third embodiment, the above-described second embodiment can be applied to a welding line having a plurality of welding points.

  FIG. 4 is a block diagram of the squeezing detection control circuit ND according to the third embodiment. This figure is used in place of the constriction detection control circuit ND of FIG. In the figure, the same blocks as those in FIG. Hereinafter, blocks indicated by dotted lines different from those in FIG. 3 will be described.

  The welding location notification circuit WP outputs a welding location notification signal Wp for notifying the welding location number assigned to each welding location. The third squeezing detection reference value calculation circuit VTN3 outputs the squeezing detection reference value signal Vtn calculated by the above equation (2) when the welding mode selection signal Tm is in the test welding mode, and corresponds to the welding location notification signal Wp. The convergence value of the squeezing detection reference value signal Vtn is stored, and in the actual welding mode, the squeezing detection reference value signal Vtn of the convergence value (proper value) at the time of test welding corresponding to the welding location notification signal Wp is stored. Output.

  An appropriate value of the squeezing detection reference value may be calculated as an average value of the squeezing detection reference values calculated for each short circuit during test welding at each welding point.

It is a time change figure of welding current Iw and welding voltage Vw which shows the constriction detection control method of consumable electrode arc welding concerning Embodiment 1 of the present invention. 2 is a block diagram of a squeezing detection control circuit ND according to Embodiment 1 of the present invention. FIG. It is a block diagram of the constriction detection control circuit ND which concerns on Embodiment 2 of this invention. It is a block diagram of the constriction detection control circuit ND which concerns on Embodiment 3 of this invention. It is a time change figure of welding current Iw and welding voltage Vw of consumable electrode arc welding. It is a block diagram of the welding power supply with an electric current rapid decrease function at the time of a constriction detection in the prior art 1. FIG. It is a timing chart of each signal in the welding power supply of FIG. It is a block diagram of the welding power supply with an electric current rapid decrease function at the time of a constriction detection in the prior art 2. It is a timing chart of each signal in the welding power supply of FIG. It is a time change figure of welding current Iw in conventional technology 3, and welding voltage Vw. It is a time change figure of welding current Iw and welding voltage Vw corresponding to Drawing 10 for explaining a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 2 Base material 2a Molten pool 3 Arc C Capacitor CMA Re-arc comparison circuit CMN Constriction detection comparison circuit DR Drive circuit Dr Drive signal DRA Charge / discharge drive circuit Drc Charge drive signal Drd Discharge drive signal DV Voltage rise value detection Circuit E Charging power supply EA Error amplification circuit FF Flip-flop circuit Ia Arc regenerating welding current value IAD Arc regenerating welding current value detection circuit Iad Arc regenerating welding current value detection signal IAR Arc regenerating current setting circuit Iar Arc Current setting at re-generation (value / signal)
Id Discharge current Io Output current Iw Welding current ND Constriction detection control circuit Nd Constriction detection signal PS Welding power supply R Resistor Rt Reset signal St Set signal Ta Arc period TM Welding mode selection circuit Tm Welding mode selection signal Tn Detection period TR Transistor TRC Charging Switching element TRD Discharging switching element Ts Short-circuit period Vc Capacitor voltage VD Welding voltage detection circuit Vd Welding voltage detection signal Vs Short-circuit voltage value Vta Short-circuit / arc discrimination value VTN Constriction detection reference value calculation circuit Vtn Constriction detection reference value (signal)
Vtn0 Initial value VTN2 Second squeezing detection reference value calculation circuit VTN3 Third squeezing detection reference value calculation circuit Vw Welding voltage WP Welding location notification circuit Wp Welding location notification signal X Voltage increase characteristic Y Current decrease characteristic ΔE Error amplification (value / signal)
ΔV Voltage rise value (detection signal)

Claims (2)

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 that controls the output to
The welding power source has a selection part for selecting the test welding mode or the actual welding mode,
When the test welding mode is selected by the operator, the welding current value at the time of the arc regeneration is detected on the actual welding line in which the welding conditions and the inductance value of the cable are determined, and the welding current at the time of the arc regeneration is detected. An appropriate value is calculated by changing the squeezing detection reference value by feedback control so that the value is substantially equal to a predetermined current value at the time of arc regeneration,
When the actual welding mode is selected by an operator, the necking detection reference value is automatically fixed to an appropriate value calculated in the test welding mode, and necking detection control is performed.
A constriction detection control method for consumable electrode arc welding. Calculate an appropriate value for the squeezing detection reference value for each of the welding locations for each of the welding locations, and calculate the squeezing detection reference value for each of the welding locations when the actual welding mode is selected. Fixed to the appropriate value,
The constriction detection control method of consumable electrode arc welding according to claim 1.

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