JP2018051579A - Arc-welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increasing of sputter generation amount even when droplet sizes are varied upon occurrence of short-circuit due to disturbance in a welding method in which feeding speed of a welding wire is alternately changed into normal feeding period and reverse feeding period.SOLUTION: In an arc-welding control method of alternately changing a feeding speed Fw of a welding wire into a normal feeding period and a reverse feeding period and repeating a short-circuit period and an arc-period to perform welding, an integral value of a weld electric current Iw during the arc-period is calculated and a reverse feeding peak value Wrp of the feeding speed Fw is changed based on an error between the integral value and a predefined standard value. The integral value is such a value as to be correlated with a droplet size upon short-circuit initiation. Therefore, the reverse feeding peak value Wrp is changed in accordance with the droplet size upon occurrence of short-circuit and, as the result, the increasing of sputter generation amount can be suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an arc welding control method in which a welding wire feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and welding is performed by repeating a short circuit period and an arc period.

  In general consumable electrode arc welding, a welding wire that is a consumable electrode is fed at a constant speed, and an arc is generated between the welding wire and a base material to perform welding. In the consumable electrode type arc welding, the welding wire and the base material are often in a welding state in which a short circuit period and an arc period are alternately repeated.

  In order to further improve the welding quality, a method has been proposed in which welding is performed by periodically repeating forward and reverse feeding of the welding wire. In invention of patent document 1, it is set as the average value of the feeding speed according to the welding current setting value, and the frequency and amplitude of the forward feed and reverse feeding of the welding wire are values according to the welding current setting value.

  By the way, during welding, the droplet formation state may vary due to various disturbances such as irregular movement of the molten pool, gas ejection from the molten pool, fluctuation of the welding position, fluctuation of the torch height, and the like. . If the formation state of the droplets varies, the size of the droplets at the time when the short circuit occurs varies, and as a result, the amount of spatter generated increases. In the above-described welding method for switching between the normal feeding period and the reverse feeding period of the feeding speed, this phenomenon becomes more conspicuous than in the case of constant speed feeding.

Japanese Patent No. 52012266

  Therefore, in the present invention, in the welding method in which the feeding speed of the welding wire is alternately switched between the normal feeding period and the reverse feeding period, the amount of spatter generated increases even if the droplet size varies due to a disturbance due to a disturbance. An object of the present invention is to provide an arc welding control method that does not have any.

In order to solve the above-described problems, the invention of claim 1
In the arc welding control method in which the welding wire feeding speed is alternately switched between the normal feeding period and the reverse feeding period, and the short circuit period and the arc period are repeatedly welded.
Detecting a value correlating with the droplet size at the time when the short-circuit period starts,
Based on this correlation value, the reverse feed peak value of the feed speed is changed,
An arc welding control method characterized by the above.

In the invention of claim 2, the correlation value is a time length of the arc period immediately before the short-circuit period starts.
The arc welding control method according to claim 1, wherein:

In the invention of claim 3, the correlation value is an integral value of a welding current during the arc period immediately before the short-circuit period starts.
The arc welding control method according to claim 1, wherein:

The invention according to claim 4 changes the reverse peak value based on an error between the correlation value and a predetermined reference value.
The arc welding control method according to any one of claims 1 to 3, wherein:

The invention of claim 5 changes the reverse feed peak value of the feed speed based on a comparison result between the correlation value and a predetermined threshold value.
The arc welding control method according to any one of claims 1 to 3, wherein:

  According to the present invention, in the welding method in which the feeding speed of the welding wire is alternately switched between the normal feeding period and the reverse feeding period, even if the droplet size varies due to a disturbance due to a disturbance, the droplet size varies depending on the droplet size variation. Since the reverse feed peak value changes, it is possible to prevent an increase in the amount of spatter generated.

It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 1 which shows the arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 2 of this invention.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source for carrying out an arc welding control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control by inverter control or the like according to an error amplification signal Ea described later, and outputs an output voltage E. Although not shown, the power main circuit PM is driven by a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, and the error amplification signal Ea that converts the smoothed direct current to a high-frequency alternating current. An inverter circuit, a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current.

  The reactor WL smoothes the output voltage E. The inductance value of the reactor WL is, for example, 100 μH.

  The feed motor WM receives a feed control signal Fc described later and feeds the welding wire 1 at a feed speed Fw by alternately repeating forward feed and reverse feed. A motor with fast transient response is used as the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

  The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E and outputs an output voltage detection signal Ed.

  The voltage error amplification circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed, and amplifies an error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (−). The voltage error amplification signal Ev is output.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short-circuit determination circuit SD receives the voltage detection signal Vd as described above, and when this value is less than a predetermined short-circuit determination value (about 10 V), it determines that the short-circuit period is in effect and becomes a High level. A short circuit determination signal Sd which is determined to be in the arc period and becomes Low level is output.

  The forward feed acceleration period setting circuit TSUR outputs a predetermined forward feed acceleration period setting signal Tsur.

  The forward feed deceleration period setting circuit TSDR outputs a predetermined forward feed deceleration period setting signal Tsdr.

  The reverse acceleration period setting circuit TRUR outputs a predetermined reverse acceleration period setting signal Trur.

  The reverse feed deceleration period setting circuit TRDR outputs a predetermined reverse feed deceleration period setting signal Trdr.

  The forward feed peak value setting circuit WSR outputs a predetermined forward feed peak value setting signal Wsr.

The droplet size correlation value calculation circuit PD receives the short-circuit determination signal Sd and the current detection signal Id as input, selects one of the following 1) or 2) and processes the droplet size correlation value: The signal Pd is output. When the short-circuit period starts, the droplet size at the occurrence of the short-circuit increases as the time length of the immediately preceding arc period increases. In addition, as the integration ground of the welding current Iw during the immediately preceding arc period increases, the droplet size at the time of occurrence of a short circuit increases.
1) The time length during which the short circuit determination signal Sd is at the low level (arc period) is measured and output as the droplet size correlation value signal Pd.
2) During a period in which the short circuit determination signal Sd is at the low level (arc period), Pd = ∫Id · dt is integrated and output as the droplet size correlation value signal Pd.

  The reference value setting circuit Pr outputs a predetermined reference value signal Pr. The reference value signal Pr is set in conjunction with the average feed speed (average welding current value). The reference value signal Pr is set by experimentally calculating the time length of the arc period or the current integration ground in a stable welding state without disturbance.

  The correlation value error amplification circuit EP receives the droplet size correlation value signal Pd and the reference value signal Pr as inputs, and calculates an error between the droplet size correlation value signal Pd (+) and the reference value signal Pr (−). Amplify and output a correlation value error amplified signal Ep.

  The reverse feed peak value setting circuit WRR receives the short-circuit discrimination signal Sd and the correlation value error amplification signal Ep as inputs, and when the short-circuit discrimination signal Sd changes to a high level (short-circuit), the reverse feed peak is set in advance. The standard value of the value and the correlation value error amplification signal Ep are added and corrected, and the reverse peak value setting signal Wrr is output. By this circuit, when the droplet size correlation value signal Pd is smaller than the reference value signal Pr (when the droplet size when the short-circuit occurs is smaller than the standard size), the reverse feed peak value setting signal Wrr is smaller than the standard value. It changes to be smaller. On the other hand, when the droplet size at the time of occurrence of a short circuit where Pd> Pr is larger than the standard size, the reverse feed peak value setting signal Wrr changes so as to be larger than the standard value.

The feed speed setting circuit FR includes the forward feed acceleration period setting signal Tsur, the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the reverse feed deceleration period setting signal Trdr, The forward feed peak value setting signal Wsr, the reverse feed peak value setting signal Wrr and the short circuit determination signal Sd are input, and the feed speed pattern generated by the following processing is output as the feed speed setting signal Fr. When the feed speed setting signal Fr is 0 or more, it is a forward feed period, and when it is less than 0, it is a reverse feed period.
1) Feed speed setting signal Fr that linearly accelerates from 0 to a positive feed peak value Wsp determined by a forward feed peak value setting signal Wsr during the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur. Is output.
2) Subsequently, during the forward feed peak period Tsp, the feed speed setting signal Fr for maintaining the forward feed peak value Wsp is output.
3) When the short-circuit determination signal Sd changes from the Low level (arc period) to the High level (short-circuit period), it shifts to the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and from the forward feed peak value Wsp. A feed speed setting signal Fr that linearly decelerates to 0 is output.
4) Subsequently, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the feed speed that linearly accelerates from 0 to the negative reverse feed peak value Wrp determined by the reverse feed peak value setting signal Wrr. A setting signal Fr is output.
5) Subsequently, during the reverse feed peak period Trp, the feed speed setting signal Fr that maintains the reverse feed peak value Wrp is output.
6) When the short circuit determination signal Sd changes from the High level (short circuit period) to the Low level (arc period), it shifts to the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr, and from the reverse feed peak value Wrp. A feed speed setting signal Fr that linearly decelerates to 0 is output.
7) By repeating the above 1) to 6), a feed rate setting signal Fr of a feed pattern that changes in a positive and negative trapezoidal shape is generated.

  The feed control circuit FC receives the feed speed setting signal Fr and receives a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. It outputs to said feed motor WM.

  The current reducing resistor R is inserted between the reactor WL and the welding torch 4. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (about 0.01 to 0.03Ω). When the current reducing resistor R is inserted into the energization path, the energy accumulated in the reactor WL and the reactor of the external cable is suddenly discharged.

  The transistor TR is connected in parallel with the current reducing resistor R and is controlled to be turned on or off in accordance with a drive signal Dr described later.

  The constriction detection circuit ND receives the short circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id as inputs, and the voltage detection signal Vd when the short circuit determination signal Sd is at a high level (short circuit period). When the voltage rise value reaches the reference value, it is determined that the constriction formation state has become the reference state, and becomes a high level. When the short circuit determination signal Sd changes to the low level (arc period), the constriction detection that becomes the low level is detected. The signal Nd is output. In addition, the squeezing detection signal Nd may be changed to a high level when the differential value of the voltage detection signal Vd during the short circuit period reaches a reference value corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the corresponding reference value, the constriction detection signal Nd is calculated. You may make it change to a High level.

  The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as input, and outputs a current comparison signal Cm that is at a high level when Id <Ilr and is at a low level when Id ≧ Ilr. Output.

  The drive circuit DR receives the current comparison signal Cm and the squeezing detection signal Nd as input, and changes to a low level when the squeezing detection signal Nd changes to a high level, and then changes to a high level after the current comparison signal Cm changes to a high level. The drive signal Dr that changes to High level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. Therefore, the welding current Iw for energizing the short-circuit load decreases rapidly. . When the sharply decreased welding current Iw value decreases to the low level current setting signal Ilr value, the drive signal Dr becomes a high level and the transistor TR is turned on. Return to the state.

The current control setting circuit ICR receives the short circuit determination signal Sd, the low level current setting signal Ilr, and the squeezing detection signal Nd as input, and outputs the current control setting signal Icr.
1) When the short circuit determination signal Sd is at the low level (arc period), the current control setting signal Icr that becomes the low level current setting signal Ilr is output.
2) When the short-circuit determination signal Sd changes to the high level (short-circuit period), the initial current setting value is set during a predetermined initial period, and thereafter, the preset peak setting value during short-circuiting is set with a predetermined inclination during short-circuiting. The current control setting signal Icr that rises to and maintains that value is output.
3) After that, when the squeezing detection signal Nd changes to the high level, the current control setting signal Icr that is the value of the low level current setting signal Ilr is output.

  The current error amplifier circuit EI receives the current control setting signal Icr and the current detection signal Id as input, amplifies an error between the current control setting signal Icr (+) and the current detection signal Id (−), and An error amplification signal Ei is output.

  The small current period circuit STD receives the short-circuit determination signal Sd as described above, and goes to a high level when a predetermined current drop time elapses from when the short-circuit determination signal Sd changes to a low level (arc period). When the short circuit determination signal Sd becomes High level (short circuit period), a small current period signal Std which becomes Low level is output.

The power supply characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, the short circuit determination signal Sd, and the small current period signal Std as input, and performs the following processing to obtain an error amplification signal. Ea is output.
1) During the period from the time when the short circuit determination signal Sd changes to the high level (short circuit period) to the time when the predetermined delay period elapses after the short circuit determination signal Sd changes to the low level (arc period) The error amplification signal Ei is output as the error amplification signal Ea.
2) During the subsequent arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) During the subsequent arc period, the current error amplification signal Ei is output as the error amplification signal Ea during the period when the small current period signal Std becomes High level.
With this circuit, the characteristics of the welding power source are constant current characteristics during a short circuit period, a delay period, and a small current period, and constant voltage characteristics during other arc periods.

  FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the arc welding control method according to the first embodiment of the present invention. (A) shows the time change of the feeding speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, (D) ) Shows a time change of the short circuit determination signal Sd, and FIG. 9E shows a time change of the small current period signal Std. Hereinafter, the operation of each signal will be described with reference to FIG.

  The feed speed Fw shown in FIG. 6A is controlled to the value of the feed speed setting signal Fr output from the feed speed setting circuit FR of FIG. The feed speed Fw is determined by the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur in FIG. 1, the forward feed peak period Tsp that continues until a short circuit occurs, and the forward feed deceleration period setting signal Tsdr in FIG. The reverse transmission period Tsd, the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur in FIG. 1, the reverse peak period Trp that continues until the arc is generated, and the reverse transmission determined by the reverse deceleration period setting signal Trdr in FIG. It is formed from the deceleration period Trd. Further, the forward peak value Wsp is determined by the forward peak value setting signal Wsr in FIG. 1, and the backward peak value Wrp is determined by the backward peak value setting signal Wrr in FIG. As a result, the feed speed setting signal Fr has a feed pattern that changes in a substantially positive and negative trapezoidal waveform.

[Operation in the short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the forward feed peak period Tsp, the welding voltage Vw rapidly decreases to a short circuit voltage value of several V as shown in FIG. The short circuit determination signal Sd changes to a high level (short circuit period). During the arc period immediately before time t1, the droplet size correlation value signal Pd is calculated. When the short-circuit period starts at time t1, the correlation value error amplification circuit EP in FIG. 1 calculates an error amplification value between the droplet size correlation value signal Pd and the reference value signal Pr, and the correlation value error amplification signal Ep is obtained. Is output. This signal is input to the reverse peak value setting circuit WRR shown in FIG. 1, and the reverse peak value setting signal Wrr is output. The reverse peak value setting signal Wrr changes as follows. For example, the standard value of the reverse feed peak value Wrp is set to 40 m / min, and the change width based on the droplet size correlation value signal Pd is about ± 10 m / min.
1) Pd <Pr (when the time length of the immediately preceding arc period or the current integrated value is smaller than the reference value)
The reverse feed peak value Wrp changes so as to be smaller than a predetermined standard value.
2) Pd> Pr (when the time length of the immediately preceding arc period or the current integrated value is larger than the reference value)
The reverse peak value Wrp changes so as to be larger than the standard value.

  When the short-circuit period starts at time t1, a transition is made to a predetermined forward feed deceleration period Tsd at times t1 to t2, and the feed speed Fw is 0 from the forward feed peak value Wsp as shown in FIG. To slow down. For example, the normal feed deceleration period Tsd = 1 ms is set.

  As shown in FIG. 5A, the feed speed Fw enters a predetermined reverse feed acceleration period Tru at times t2 to t3, and accelerates from 0 to the reverse feed peak value Wrp. During this period, the short circuit period continues. For example, the reverse feed acceleration period Tru = 1 ms is set.

  When the reverse acceleration period Tru ends at time t3, the feed speed Fw enters the reverse peak period Trp and becomes the reverse peak value Wrp as shown in FIG. The reverse feed peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is a short circuit period. The reverse transmission peak period Trp is not a predetermined value, but is about 4 ms.

  As shown in FIG. 5B, the welding current Iw during the short-circuit period from time t1 to t4 has a predetermined initial current value during a predetermined initial period. Thereafter, the welding current Iw rises with a predetermined slope at the time of short circuit, and maintains that value when it reaches a predetermined peak value at the time of short circuit.

  As shown in FIG. 6C, the welding voltage Vw increases from the point where the welding current Iw becomes the short circuit peak value. This is because a constriction is gradually formed in the droplet at the tip of the welding wire 1 due to the reverse feed of the welding wire 1 and the action of the pinch force caused by the welding current Iw.

  After that, when the voltage increase value of the welding voltage Vw reaches the reference value, it is determined that the constriction formation state has become the reference state, and the constriction detection signal Nd in FIG. 1 changes to the high level.

  In response to the squeezing detection signal Nd becoming high level, the drive signal Dr in FIG. 1 becomes low level, so that the transistor TR in FIG. 1 is turned off and the current reducing resistor R in FIG. Inserted. At the same time, the current control setting signal Icr in FIG. 1 is reduced to the value of the low level current setting signal Ilr. For this reason, as shown in FIG. 5B, the welding current Iw rapidly decreases from the short-circuit peak value to the low-level current value. When the welding current Iw decreases to the low level current value, the drive signal Dr returns to the high level, so that the transistor TR is turned on and the current reducing resistor R is short-circuited. As shown in FIG. 6B, the welding current Iw is the low level current until the predetermined delay period elapses after the arc is regenerated because the current control setting signal Icr remains the low level current setting signal Ilr. Keep the value. Therefore, the transistor TR is turned off only during a period from when the squeezing detection signal Nd changes to the high level until the welding current Iw decreases to the low level current value. As shown in FIG. 5C, the welding voltage Vw rapidly increases after once decreasing because the welding current Iw becomes small. Each parameter mentioned above is set to the following values, for example. Initial current = 40 A, initial period = 0.5 ms, short circuit slope = 2 ms, short circuit peak value = 400 A low level current value = 50 A, delay period = 1 ms.

[Operation during arc period from time t4 to t7]
At time t4, when the constriction progresses due to the pinch force caused by the reverse feeding of the welding wire and the energization of the welding current Iw, and an arc is generated, the welding voltage Vw is an arc voltage value of several tens of volts as shown in FIG. Therefore, the short circuit determination signal Sd changes to the low level (arc period) as shown in FIG. When the arc period starts, the calculation of the droplet size correlation value signal Pd starts and continues until the arc period ends.

  At the time t4, when the arc period starts, a transition is made to a predetermined reverse feed deceleration period Trd at times t4 to t5, and as shown in FIG. 5A, the feed speed Fw is determined from the reverse feed peak value Wrp. Decelerate to zero.

  When the reverse feed deceleration period Trd ends at time t5, the process proceeds to a predetermined forward feed acceleration period Tsu at times t5 to t6. During the normal feed acceleration period Tsu, the feed speed Fw is accelerated from 0 to the normal feed peak value Wsp as shown in FIG. During this period, the arc period continues. For example, the normal feed acceleration period Tsu = 1 ms is set.

  When the normal feed acceleration period Tsu ends at time t6, the feed speed Fw enters the normal feed peak period Tsp as shown in FIG. The arc period continues during this period. The forward feed peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. When a short circuit occurs, the operation returns to the operation at time t1. The forward feed peak period Tsp is not a predetermined value, but is about 4 ms. The forward feed peak value Wsp is set to 50 m / min, for example.

  When an arc is generated at time t4, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. On the other hand, as shown in FIG. 5B, the welding current Iw continues to have a low level current value during the delay period from time t4. Thereafter, the welding current Iw increases to a high current value. During the arc period in which the current value is high, feedback control of the welding power source is performed by the voltage error amplification signal Ev in FIG.

  At time t61 when a predetermined current drop time elapses after the arc is generated at time t4, the small current period signal Std changes to the high level as shown in FIG. In response to this, the welding power source is switched from the constant voltage characteristic to the constant current characteristic. For this reason, as shown in FIG. 5B, the welding current Iw decreases to a low level current value, and maintains that value until time t7 when a short circuit occurs. Similarly, the welding voltage Vw also decreases as shown in FIG. The small current period signal Std returns to the Low level when a short circuit occurs at time t7. Since the current drop time is set to about 5 ms, the timing at time t61 is during the forward feed peak period Tsp.

  In the first embodiment, the reverse feed peak value Wrp changes based on a value (droplet size correlation value signal Pd) that correlates with the droplet size at the time when the short-circuit period starts. That is, the smaller the droplet size is, the smaller the reverse feed peak value Wrp is. The larger the droplet size is, the larger the reverse feed peak value Wrp is. When the droplet size at the time of occurrence of a short circuit is small, the spatter generation amount can be reduced by reducing the reverse feed peak value Wrp. Conversely, when the droplet size at the time of occurrence of a short circuit is large, the amount of spatter generated can be reduced by increasing the reverse feed peak value Wrp.

[Embodiment 2]
The invention of the second embodiment changes the reverse feed peak value of the feed speed based on the comparison result between the droplet size correlation value signal and a predetermined threshold value.

  FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the second embodiment of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. In this figure, the reference value setting circuit Pr in FIG. 1 is deleted, the correlation value error amplifier circuit EP in FIG. 1 is replaced with a correlation value comparison circuit CP, and the reverse peak value setting circuit WRR in FIG. The peak value setting circuit WRR2 is replaced. Hereinafter, these blocks will be described with reference to FIG.

  The correlation value comparison circuit CP receives the droplet size correlation value signal Pd as an input, and outputs a correlation value comparison signal Cp = 1 when the droplet size correlation value signal Pd is less than a predetermined lower threshold value. When the size correlation value signal Pd is equal to or greater than a predetermined upper limit threshold, the correlation value comparison signal Cp = 2 is output. When the droplet size correlation value signal Pd is equal to or greater than the lower limit threshold and less than the upper limit threshold, the correlation value comparison signal Cp = 0 is output.

  The second reverse feed peak value setting circuit WRR2 receives the short circuit determination signal Sd and the correlation value comparison signal Cp as input, and the correlation value comparison signal Cp when the short circuit determination signal Sd changes to a high level (short circuit). When = 1, the standard value of the reverse peak value determined in advance is corrected so as to decrease by a predetermined value, and when the correlation value comparison signal Cp = 2, the standard value of the reverse peak value is increased by a predetermined value. When the correlation value comparison signal Cp = 0, the reverse peak value standard value is output as it is as the reverse peak value setting signal Wrr. With this circuit, when the correlation value comparison signal Cp = 1 (the droplet size at the time of occurrence of a short circuit is smaller than the standard size), the reverse feed peak value setting signal Wrr is changed to be smaller than the standard value. When Cp = 2 (the droplet size when the short-circuit occurs is larger than the standard size), the reverse feed peak value setting signal Wrr changes so as to be larger than the standard value. When Cp = 0 (the droplet size at the time of short circuit is almost the standard size), the reverse feed peak value setting signal Wrr remains at the standard value.

  The timing chart of each signal in the welding power source in FIG. 3 showing the arc welding control method according to the second embodiment of the present invention is the same as that in FIG. However, the method for correcting the reverse feed peak value Wrp based on the droplet size correlation value signal Pd is different as described above.

  According to the above-described second embodiment, the reverse peak value of the feeding speed is changed based on the comparison result between the correlation value and a predetermined threshold value. Thereby, the same effects as those of the first embodiment can be obtained. In the invention of the second embodiment, when the droplet size correlation value signal Pd is in an appropriate range, the reverse feed peak value does not change, so that there is an effect that the change in the welding state becomes gentle.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll CM Current comparison circuit Cm Current comparison signal CP Correlation value comparison circuit Cp Correlation value comparison signal DR Drive circuit Dr Drive signal E Output voltage Ea Error amplification signal ED Output voltage detection Circuit Ed Output voltage detection signal EI Current error amplification circuit Ei Current error amplification signal EP Correlation value error amplification circuit Ep Correlation value error amplification signal ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit Fr Feed speed setting signal Fw Feed speed ICR Current control setting circuit Icr Current control setting signal ID Current detection circuit Id Current detection signal ILR Low level current setting circuit Ilr Low Level current setting signal Iw Welding current ND Constriction detection circuit Nd Constriction detection signal PD Droplet size Function value calculation circuit Pd Droplet size correlation value signal PM Power supply main circuit Pr Reference value setting circuit Pr Reference value signal R Current reducing resistor SD Short circuit determination circuit Sd Short circuit determination signal STD Small current period circuit Std Small current period signal SW Power supply characteristics Switching circuit TR transistor reverse feed deceleration period TRDR reverse feed deceleration period setting circuit Trrd reverse feed deceleration period setting signal Trp reverse feed peak period Tru reverse feed acceleration period TRUR reverse feed acceleration period setting circuit Trur reverse feed acceleration period setting signal Tsd forward feed Deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp Forward feed peak period Tsu Su Forward feed acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal VD Voltage detection circuit Vd Voltage detection signal Vw Welding Voltage WL Reactor WM Feed motor Wrp Reverse feed peak value WRR Reverse feed peak value setting circuit Wrr Reverse feed peak value setting signal W R2 second backhaul peak value setting circuit Wsp positive feed peak value WSR positive feed peak value setting circuit Wsr positive feed peak value setting signal

Claims (5)

In the arc welding control method in which the welding wire feeding speed is alternately switched between the normal feeding period and the reverse feeding period, and the short circuit period and the arc period are repeatedly welded.
Detecting a value correlating with the droplet size at the time when the short-circuit period starts,
Based on this correlation value, the reverse feed peak value of the feed speed is changed,
An arc welding control method characterized by the above. The correlation value is a time length of the arc period immediately before the short-circuit period starts;
The arc welding control method according to claim 1, wherein: The correlation value is an integral value of a welding current during the arc period immediately before the short-circuit period starts.
The arc welding control method according to claim 1, wherein: Changing the reverse peak value based on an error between the correlation value and a predetermined reference value;
The arc welding control method according to any one of claims 1 to 3, wherein: Changing a reverse feed peak value of the feed speed based on a comparison result between the correlation value and a predetermined threshold;
The arc welding control method according to any one of claims 1 to 3, wherein:

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