JP2022056565A - Arc-welding control method - Google Patents

Abstract

To make it possible to achieve high-quality welding when performing semi-automatic welding in forward/reverse feed arc-welding.SOLUTION: According to arc-welding control method, a welding wire is fed by push-pull feed control by a push side feed motor which performs forward rotation Fwp and a pull side feed motor which repeats forward rotation and reverse rotation, an intermediate wire storage part, which temporally accommodates the welding wire, is provided between feed routes of the push side feed motor and the pull side feed motor, a pull feed speed Fw of the pull side feed motor is corrected on the basis of a capacity of the intermediate wire storage part, and welding is performed. In the arc-welding control method, a forward feed deceleration period Tsd and/or a reverse feed deceleration period Trd of the pull feed speed Fw is corrected and controlled on the basis of the capacity of the intermediate wire storage part. By this, even if semi-automatic welding is performed, a push feed speed Fwp and the pull feed speed Fw become substantially equal, and therefore, high-quality welding can be achieved.SELECTED DRAWING: Figure 2

Description

The present invention relates to an arc welding control method in which a welding wire is fed and welded by push-pull feed control by a push-side feed motor that rotates forward and a pull-side feed motor that repeats forward rotation and reverse rotation. It is a thing.

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

In order to further improve the welding quality, a forward / reverse feed arc welding method has been proposed in which the feed of the welding wire is alternately switched between normal feed and reverse feed for welding. In this forward / reverse feed arc welding method, the cycle of repeating short circuit and arc can be stabilized as compared with the conventional technique of constant feed rate, so that the amount of spatter generated can be reduced and the bead appearance can be improved. Welding quality can be improved.

In the forward / reverse feed arc welding method, it is necessary to switch between the forward feed and the reverse feed of the welding wire at high speed and high accuracy at about 100 Hz. For this reason, the push-pull feeding method is often adopted as the feeding method. Further, it is often the case that an intermediate wire accommodating portion for temporarily accommodating the welded wire is provided between the feeding path between the push side feeding motor and the pull side feeding motor.

In the forward / reverse feed arc welding method, the forward feed period and the reverse feed period are switched in synchronization with the occurrence timing of the short circuit period and the arc period. For this reason, when the welding conditions such as the set value of the welding voltage and the protrusion length change and the time ratio between the short circuit period and the arc period changes, the time ratio between the normal feed period and the reverse feed period also changes, so welding is performed. The average feed rate of the wire changes. When the average feeding rate changes, the amount of welding changes, so the welding quality deteriorates. In order to deal with this problem, in the inventions of Patent Documents 1 and 2, the push-side motor is used to positively feed and feed at a constant speed, the capacity of the intermediate wire accommodating portion is detected, and the pull-side motor is based on this accommodating capacity. The pull feed rate is corrected and controlled. This correction control suppresses the change in the average feeding speed.

Japanese Unexamined Patent Publication No. 2017-94380 Japanese Unexamined Patent Publication No. 2020-99945

In the correction control of the prior art, the forward feed peak value and / or the reverse feed peak value of the pull feed rate is changed based on the capacity of the intermediate wire accommodating portion. However, in semi-automatic welding in which the welding operator manually operates the welding torch to weld, if this correction control is performed, it is caused by fluctuations in the wire protrusion length, advance angle, welding speed, etc. due to the welding operator's camera shake. There is a problem that the arc length fluctuates greatly and the welded state tends to become unstable.

Therefore, in the present invention, in the forward / reverse feed arc welding method in which the pull feed rate is corrected and controlled based on the capacity of the intermediate wire accommodating portion, the welding state becomes unstable due to the camera shake of the welder. It is an object of the present invention to provide an arc welding control method capable of suppressing.

In order to solve the above-mentioned problems, the invention of claim 1 is
Welding wire is fed by push-pull feed control by a push-side feed motor that rotates forward and a pull-side feed motor that repeats forward rotation and reverse rotation.
An intermediate wire accommodating portion for temporarily accommodating the welded wire is provided between the feeding path between the push-side feeding motor and the pull-side feeding motor, and the pull is based on the accommodating capacity of the intermediate wire accommodating portion. Correct the pull feed speed of the side feed motor and
In the arc welding control method in which short-circuit period and arc period are repeatedly welded,
Based on the capacity, the normal feed deceleration period and / or the reverse feed deceleration period of the pull feed rate is corrected and controlled.
This is an arc welding control method characterized by this.

The invention of claim 2 is
The correction control of the forward deceleration period is performed based on the capacity at the start of the forward deceleration period, and the correction of the reverse deceleration period is performed based on the capacity at the start of the reverse deceleration period. To control,
The arc welding control method according to claim 1, wherein the arc welding is controlled.

The invention of claim 3 is
When the correction control of the forward feed deceleration period is performed, the reverse feed acceleration period is corrected and controlled so that the total value of the forward feed deceleration period and the reverse feed acceleration period becomes constant, and the reverse feed deceleration period is performed. When the correction control of the above is performed, the correction control of the forward feed acceleration period is performed so that the total value of the reverse feed deceleration period and the forward feed acceleration period becomes constant.
The arc welding control method according to claim 1 or 2, wherein the method is characterized by the above.

According to the present invention, in the forward / reverse feed arc welding method in which the pull feed rate is corrected and controlled based on the capacity of the intermediate wire accommodating portion, the welding state becomes unstable due to the camera shake of the welder. Can be suppressed.

It is a block diagram of the welding power source for carrying out 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 source of FIG. 1 which shows the arc welding control method which concerns on Embodiment 1 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V as an input, 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, this power supply main circuit PM is driven by a primary rectifier that rectifies a commercial power supply, a smoothing capacitor that smoothes the rectified direct current, and the above-mentioned error amplification signal Ea that converts the smoothed direct current into high-frequency alternating current. It is equipped with an inverter circuit, a high-frequency transformer that steps down high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current to direct current.

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

The push-side feed motor WMP receives the push feed control signal Fcp, which will be described later, as an input, rotates normally, and feeds the welding wire 1 at a push feed rate Fwp of a constant speed. The pull-side feed motor WM receives the pull feed control signal Fc, which will be described later, as an input, and alternately repeats forward feed rotation and reverse feed rotation to feed the weld wire 1 at the feed speed Fw. The push-side feed motor WMP is provided on the upstream side of the feed path, and the pull-side feed motor WM is provided on the downstream side. Both feed motors are speed controlled. Both feed motors make up a push-pull feed control system.

The intermediate wire accommodating portion WB is provided in the feeding path between the push-side feeding motor WMP and the pull-side feeding motor WM, temporarily accommodates the welded wire 1, and accommodates the accommodating amount signal Wb according to the accommodating amount. Is output. Since the intermediate wire accommodating portion WB is commonly used in the prior art such as Patent Document 1, the detailed structure will be omitted. The capacity of the weld wire 1 is detected by a mechanical principle, an electrical principle, an optical principle, a magnetic principle, or a combination of these principles.

The welding wire 1 is fed in the welding torch 4 by the rotation of the feeding roll 5 coupled to the pull-side feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the feeding tip (not shown) in the welding torch 4 and the base metal 2, and the welding current Iw is energized. Shielding gas (not shown) is ejected from the tip of the welding torch 4 to shield the arc 3 from the atmosphere.

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 takes the above-mentioned output voltage setting signal Er and the above-mentioned output voltage detection signal Ed as inputs, and amplifies the 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 above welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the above welding voltage Vw and outputs a voltage detection signal Vd. The short-circuit discrimination circuit SD takes the above voltage detection signal Vd as an input, and when this value is less than the predetermined short-circuit discrimination value (about 10V), it determines that it is in the short-circuit period and reaches the High level. The short-circuit discrimination signal Sd, which is determined to be in the arc period and becomes the Low level, is output.

The normal feed acceleration period initial value setting circuit TSUS outputs a predetermined forward feed acceleration period initial value setting signal Tsus.

The forward deceleration period initial value setting circuit TSDS outputs a predetermined normal feed deceleration period initial value setting signal Tsds.

The reverse feed acceleration period initial value setting circuit TRUS outputs a predetermined reverse feed acceleration period initial value setting signal Trus.

The reverse feed deceleration period initial value setting circuit TRDS outputs a predetermined reverse feed deceleration period initial value setting signal Trds.

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

The reverse feed peak value setting circuit WRR outputs a predetermined reverse feed peak value setting signal Wrr.

The accommodation amount setting circuit WBR outputs a predetermined accommodation amount setting signal Wbr which is a target value. The capacity error amplification circuit EW amplifies the error between the capacity setting signal Wbr (-) and the capacity signal Wb (+) by using the above capacity setting signal Wbr and the above capacity signal Wb as inputs. The accommodation error amplification signal Ew is output. Ew = G · (Wb—Wbr), where G is a positive amplification factor. Therefore, when the accommodation signal Wb is larger than the accommodation setting signal Wbr of the target value, the accommodation error amplification signal Ew becomes a positive value, and the accommodation signal Wb is smaller than the accommodation setting signal Wbr of the target value. In some cases, the accommodation error amplification signal Ew becomes a negative value.

The pull feed rate correction circuit FH has the above-mentioned short-circuit determination signal Sd, the above-mentioned forward feed acceleration period initial value setting signal Tsus, the above-mentioned forward feed deceleration period initial value setting signal Tsds, and the above-mentioned reverse feed acceleration period initial value setting signal. Using Trus, the above-mentioned reverse feed deceleration period initial value setting signal Trds, and the above-mentioned capacity error amplification signal Ew as inputs, one of the following processes 1) to 6) is selected and correction control is performed. The forward feed acceleration period setting signal Tsur, the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, and the reverse feed deceleration period setting signal Trdr are output. The correction control (modulation control) shown below is performed every one cycle of the normal feed period and the reverse feed period. One cycle is about 10 ms. The correction control shown below is the case of P control, but may be PI control or PID control.

Process 1) When only the forward deceleration period setting signal Tsdr is corrected and controlled When the short-circuit discrimination signal Sd changes to the High level (short-circuit period) and the forward deceleration period starts, the capacity error amplification signal Ew at that time is positive. The feed / deceleration period initial value setting signal Tsds is corrected and controlled (modulation control), and the normal feed / deceleration period setting signal Tsdr = Tsds + Ew is output. When the accommodating amount signal Wb is larger than the accommodating amount setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, and the accommodating amount signal Wb decreases and approaches the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes shorter than the initial value, and the accommodation signal Wb increases and approaches the set value. .. Then, the other signals are output as Tsur = Tsus, Trur = Trus, and Trdr = Trds as input signals.

Process 2) When only the reverse feed deceleration period setting signal Trdr is corrected and controlled When the short circuit discrimination signal Sd changes to the Low level (arc period) and the reverse feed deceleration period starts, it is reversed by the accommodation error amplification signal Ew at that time. The feed / deceleration period initial value setting signal Trds is corrected and controlled (modulation control), and the reverse feed / deceleration period setting signal Trdr = Trds-Ew is output. When the accommodating amount signal Wb is larger than the accommodating amount setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, and the accommodating amount signal Wb decreases and approaches the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the accommodation signal Wb increases and approaches the set value. .. Then, the other signals are output as Tsur = Tsus, Tsdr = Tsds and Trur = Trus as input signals.

Process 3) When correcting and controlling both the forward deceleration period setting signal Tsdr and the reverse deceleration period setting signal Trdr Both the above processes 1) and 2) are performed. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodation amount signal Wb is smaller than the accommodation amount setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, and the reverse feed deceleration period setting signal Trdr becomes longer than the initial value and accommodates. The quantity signal Wb increases and approaches the set value. Then, the other signals are output as Tsur = Tsus and Trur = Trus as input signals.

Process 4) When the forward deceleration period setting signal Tsdr and the reverse feed acceleration period setting signal Trur are corrected and controlled When the short-circuit discrimination signal Sd changes to the High level (short-circuit period) and the forward deceleration period starts, that The positive feed deceleration period initial value setting signal Tsds is corrected and controlled (modulation control) by the accommodation error amplification signal Ew at the time point, and the normal feed deceleration period setting signal Tsdr = Tsds + Ew is output. At the same time, the reverse feed acceleration period initial value setting signal Trus is corrected and controlled (modulation control) by the capacity error amplification signal Ew, and the reverse feed acceleration period setting signal Trur = Trus-Ew is output. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, the reverse acceleration period setting signal Trur becomes shorter than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr is shorter than the initial value, and the reverse acceleration period setting signal Trur is longer than the initial value and is accommodated. The quantity signal Wb increases and approaches the set value. Here, in the process 4), since Tsdr + Trur becomes a constant value, the short-circuit period can be maintained at a substantially constant value even if correction control is performed, and the welded state can be stabilized. Then, the other signals are output as Tsur = Tsus and Trdr = Trds as input signals.

Process 5) When the reverse feed deceleration period setting signal Trdr and the forward feed acceleration period setting signal Tsur are corrected and controlled When the short circuit discrimination signal Sd changes to the Low level (arc period) and the reverse feed deceleration period starts, that The reverse feed deceleration period initial value setting signal Trds is corrected and controlled (modulation control) by the accommodation error amplification signal Ew at the time point, and the reverse feed deceleration period setting signal Trdr = Trds-Ew is output. At the same time, the positive feed acceleration period initial value setting signal Tsus is corrected and controlled (modulation controlled) by the above-mentioned capacity error amplification signal Ew, and the normal feed acceleration period setting signal Tsur = Tsus + Ew is output. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the reverse feed deceleration period setting signal Trdr is shorter than the initial value, the forward acceleration period setting signal Tsur is longer than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodating amount signal Wb is smaller than the accommodating amount setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the forward feed acceleration period setting signal Tsur becomes shorter than the initial value and accommodates. The quantity signal Wb increases and approaches the set value. Here, in the process 5), since Trdr + Tsur becomes a constant value, the arc period can be maintained at a substantially constant value even if correction control is performed, and the welded state can be stabilized. Then, the other signals are output as Tsdr = Tsds and Trur = Trus as input signals.

Process 6) When correcting and controlling four of the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the reverse feed deceleration period setting signal Trdr, and the forward feed acceleration period setting signal Tsur. ) Do both. When the accommodation amount signal Wb is larger than the accommodation amount setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes longer than the initial value, the reverse feed acceleration period setting signal Trur becomes shorter than the initial value, and the reverse feed deceleration period. The setting signal Trdr becomes shorter than the initial value, the normal feed acceleration period setting signal Tsur becomes longer than the initial value, and the accommodation signal Wb decreases and approaches the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr is shorter than the initial value, and the reverse acceleration period setting signal Trur is longer than the initial value, and vice versa. The feed / deceleration period setting signal Trdr becomes longer than the initial value, the forward acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases to approach the set value. Here, in the process 6), since Tsdr + Trur and Trdr + Tsur each have constant values, the short-circuit period and the arc period can be maintained at substantially constant values even if correction control is performed, and the welded state can be stabilized. ..

The pull feed rate 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, and the above. With the normal feed peak value setting signal Wsr, the above-mentioned reverse feed peak value setting signal Wrr, and the above-mentioned short-circuit discrimination signal Sd as inputs, the pull feed rate pattern generated by the following processing is used as the pull feed rate setting signal Fr. Output. When the pull feed rate setting signal Fr is 0 or more, the normal feed period is set, and when it is less than 0, the reverse feed period is set.
1) Positive feed acceleration period setting signal During the normal feed acceleration period Tsur, the pull feed rate setting signal that accelerates linearly from 0 to the positive normal feed peak value Wsp determined by the positive feed peak value setting signal Wsr. Output Fr.
2) Subsequently, during the normal feed peak period Tsp, the pull feed rate setting signal Fr that maintains the above normal feed peak value Wsp is output.
3) When the short-circuit discrimination signal Sd changes from the Low level (arc period) to the High level (short-circuit period), it shifts to the forward deceleration period Tsd determined by the forward deceleration period setting signal Tsdr, and from the above normal feed peak value Wsp. The pull feed rate setting signal Fr that decelerates linearly to 0 is output.
4) Subsequently, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the pull feed linearly accelerates from 0 to the negative reverse feed peak value Wrp determined by the reverse feed peak value setting signal Wrr. The speed setting signal Fr is output.
5) Subsequently, during the reverse feed peak period Trp, the pull feed rate setting signal Fr that maintains the above reverse feed peak value Wrp is output.
6) When the short-circuit discrimination 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 above-mentioned reverse feed peak value Wrp. The pull feed rate setting signal Fr that decelerates linearly to 0 is output.
7) By repeating the above 1) to 6), a pull feed rate setting signal Fr of a feed pattern that changes in a positive or negative trapezoidal wave shape is generated.

The pull feed control circuit FC receives the above pull feed rate setting signal Fr as an input, and pull feed for feeding the weld wire 1 at a pull feed rate Fw corresponding to the value of the pull feed rate setting signal Fr. The feed control signal Fc is output to the pull-side feed motor WM.

The push feed rate setting circuit FRP outputs a predetermined push feed rate setting signal Frp having a positive value. The push feed control circuit FCP receives the above push feed rate setting signal Frp as an input, and push feed for feeding the welded wire 1 at a push feed rate Fwp corresponding to the value of the push feed rate setting signal Frp. The feed control signal Fcp is output to the push-side feed motor WMP described above.

The current reduction resistor R is inserted between the reactor WL and the welding torch 4. The value of the current reduction resistor R is set to a value (about 0.5 to 3Ω) that is 50 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 current-carrying path, the energy stored 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 described above, and is controlled on or off according to a drive signal Dr described later.

The constriction detection circuit ND receives the above-mentioned short-circuit discrimination signal Sd, the above-mentioned voltage detection signal Vd, and the above-mentioned current detection signal Id as inputs, and is a voltage detection signal Vd when the short-circuit discrimination signal Sd is at the High level (short-circuit period). When the voltage rise value reaches the reference value, it is determined that the constriction formation state has reached the reference state and becomes the High level, and when the short-circuit discrimination signal Sd changes to the Low level (arc period), the constriction detection becomes the Low level. The signal Nd is output. Further, the constriction detection signal Nd may be changed to the High level when the differential value of the voltage detection signal Vd during the short-circuit period reaches the corresponding reference value. Further, the value of the voltage detection signal Vd is divided by the value of the current detection signal Id to calculate the resistance value of the droplet, and when the differential value of this resistance value reaches the corresponding reference value, the constriction detection signal Nd is obtained. It may be changed 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 above-mentioned current detection signal Id as inputs, and outputs a current comparison signal Cm that becomes High level when Id <Ilr and Low level when Id ≧ Ilr. Output.

The drive circuit DR receives the above-mentioned current comparison signal Cm and the above-mentioned constriction detection signal Nd as inputs, and changes to the Low level when the constriction detection signal Nd changes to the High level, and then changes to the Low level when the current comparison signal Cm changes to the High level. The drive signal Dr that changes to the High level is output to the base terminal of the above-mentioned transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes Low level, the transistor TR is turned off, and the current reduction resistor R is inserted in the current path, so that the welding current Iw that energizes the short-circuit load drops sharply. .. Then, when the value of the suddenly reduced welding current Iw decreases to the value of the low level current setting signal Ilr, the drive signal Dr becomes the High level and the transistor TR is turned on, so that the current reduction resistor R is short-circuited and normally. Return to the state of.

The current control setting circuit ICR receives the above-mentioned short-circuit discrimination signal Sd, the above-mentioned low-level current setting signal Ilr, and the above-mentioned constriction detection signal Nd as inputs, performs the following processing, and outputs the current control setting signal Icr.
1) When the short-circuit discrimination signal Sd is at the Low level (arc period), the current control setting signal Icr, which is the low level current setting signal Ilr, is output.
2) When the short-circuit discrimination signal Sd changes to the High level (short-circuit period), the initial current set value becomes a predetermined value during the predetermined initial period, and then the short-circuit peak set value predetermined with the predetermined short-circuit slope. The current control setting signal Icr that rises to and maintains that value is output.
3) After that, when the constriction detection signal Nd changes to the High level, the current control setting signal Icr, which is the value of the low level current setting signal Ilr, is output.

The current error amplifier circuit EI uses the above-mentioned current control setting signal Icr and the above-mentioned current detection signal Id as inputs, and amplifies the error between the current control setting signal Icr (+) and the current detection signal Id (-) to obtain a current. The error amplification signal Ei is output.

The current drop time setting circuit TDR outputs a predetermined current drop time setting signal Tdr.

The small current period circuit STD receives the above-mentioned short-circuit discrimination signal Sd and the above-mentioned current drop time setting signal Tdr as inputs, and is determined by the current drop time setting signal Tdr from the time when the short-circuit discrimination signal Sd changes to the Low level (arc period). When the time elapses, the high level is reached, and then when the short circuit determination signal Sd reaches the high level (short circuit period), the low level signal Std is output.

The power supply characteristic switching circuit SW receives the above-mentioned current error amplification signal Ei, the above-mentioned voltage error amplification signal Ev, the above-mentioned short-circuit discrimination signal Sd, and the above-mentioned small current period signal Std as inputs, and performs the following processing to perform the following processing, and the error amplification signal. Output Ea.
1) During the period from the time when the short-circuit discrimination signal Sd changes to the High level (short-circuit period) to the time when the short-circuit discrimination signal Sd changes to the Low level (arc period) and a predetermined delay period elapses, the current The error amplification signal Ei is output as the error amplification signal Ea.
2) During the subsequent large current arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) During the small current arc period in which the small current period signal Std becomes the High level during the subsequent arc period, the current error amplification signal Ei is output as the error amplification signal Ea.
By this circuit, the characteristics of the welding power supply become the constant current characteristic during the short circuit period, the delay period and the small current arc period, and become the constant voltage characteristic during the other large current arc period.

FIG. 2 is a timing chart of each signal in the welding power supply of FIG. 1 showing an arc welding control method according to the first embodiment of the present invention. The figure (A) shows the time change of the pull feed rate Fw, the figure (B) shows the time change of the welding current Iw, and the figure (C) shows the time change of the welding voltage Vw. D) shows the time change of the short circuit discrimination signal Sd, FIG. 3E shows the time change of the small current period signal Std, and FIG. 3F shows the time change of the push feeding rate Fwp. Hereinafter, the operation of each signal will be described with reference to the figure.

The pull feed rate Fw shown in FIG. 1A is controlled by the value of the pull feed rate setting signal Fr output from the pull feed rate setting circuit FR of FIG. The pull feed rate Fw is determined by the normal 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. Forward deceleration period Tsd, reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur in FIG. 1, reverse peak period Trp that continues until an arc occurs, and reverse determined by the reverse deceleration period setting signal Trdr in FIG. It is formed from the feed deceleration period Trd. Further, the forward peak value Wsp is determined by the forward peak value setting signal Wsr in FIG. 1, and the reverse peak value Wrp is determined by the reverse peak value setting signal Wrr in FIG. As a result, the pull feed rate setting signal Fr becomes a feed pattern that changes in a substantially trapezoidal wave shape of positive and negative. Further, the push feeding speed Fwp shown in FIG. 1F is a constant speed determined by the push feeding speed setting signal Frp of FIG.

[Operation during short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the normal feed peak period Tsp, the welding voltage Vw drops sharply to a short circuit voltage value of several V as shown in FIG. The short-circuit discrimination signal Sd changes to the High level (short-circuit period). In response to this, the process shifts to the predetermined normal feed deceleration period Tsd at times t1 to t2, and as shown in FIG. do.

As shown in FIG. 3A, the pull feed rate Fw enters the predetermined reverse feed acceleration period Tru at times t2 to t3, and accelerates from 0 to the above-mentioned reverse feed peak value Wrp. During this period, the short circuit period continues.

When the reverse feed acceleration period Tru ends at time t3, the pull feed rate Fw enters the reverse feed peak period Trp and becomes the above-mentioned reverse feed peak value Wrp, as shown in FIG. The reverse peak period Trp continues until an arc is generated at time t4. Therefore, the period from time t1 to t4 is the short circuit period.

As shown in FIG. 3B, the welding current Iw during the short-circuit period from time t1 to t4 has a predetermined initial current value during the predetermined initial period. After that, the welding current Iw increases with a predetermined short-circuit slope, and maintains that value when the predetermined short-circuit peak value is reached.

As shown in FIG. 6C, the welding voltage Vw rises from the point where the welding current Iw reaches the peak value at the time of short circuit. This is because the back feed of the welding wire 1 and the action of the pinch force due to the welding current Iw gradually form a constriction in the droplets at the tip of the welding wire 1.

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

In response to the constriction detection signal Nd reaching the High level, the drive signal Dr in FIG. 1 becomes the Low level, so that the transistor TR in FIG. Will be inserted. At the same time, the current control setting signal Icr in FIG. 1 becomes smaller than the value of the low level current setting signal Ilr. Therefore, as shown in FIG. 3B, the welding current Iw sharply decreases from the peak value at the time of short circuit to the low level current value. Then, when the welding current Iw decreases to a low level current value, the drive signal Dr returns to the high level, so that the transistor TR is turned on and the current reduction resistor R is short-circuited. As shown in FIG. 3B, the welding current Iw is a low level current from the arc re-occurrence until the predetermined delay period elapses because the current control setting signal Icr remains the low level current setting signal Ilr. Maintain the value. Therefore, the transistor TR is turned off only during the period from the time when the constriction detection signal Nd changes to the High level until the welding current Iw decreases to the low level current value. As shown in FIG. 3C, the welding voltage Vw decreases once and then rises sharply because the welding current Iw becomes small. Each of the above-mentioned parameters is set to the following values, for example. Initial current = 40A, initial period = 0.5ms, short-circuit gradient = 175A / ms, short-circuit peak value = 400A, low-level current value = 50A, delay period = 0.5ms.

[Operation during the arc period from time t4 to t7]
At time t4, when the constriction progresses and an arc is generated due to the pinch force due to the reverse feed of the welding wire and the energization of the welding current Iw, the welding voltage Vw is an arc voltage value of several tens of V as shown in FIG. As shown in FIG. 3D, the short-circuit discrimination signal Sd changes to the Low level (arc period). In response to this, the process shifts to the predetermined reverse feed deceleration period Trd at times t4 to t5, and as shown in FIG. do.

When the reverse feed deceleration period Trd ends at time t5, the process shifts to the predetermined forward feed acceleration period Tsu from time t5 to t6. During this normal feed acceleration period Tsu, the pull feed rate Fw accelerates from 0 to the above normal feed peak value Wsp, as shown in FIG. The arc period continues during this period.

When the normal feed acceleration period Tsu ends at time t6, the pull feed rate Fw enters the normal feed peak period Tsp and becomes the above normal feed peak value Wsp, as shown in FIG. The arc period continues during this period. The forward peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. Then, when a short circuit occurs, the operation returns to the operation at time t1.

When an arc is generated at time t4, the welding voltage Vw rapidly increases to an arc voltage value of several tens of V, as shown in FIG. On the other hand, as shown in FIG. 3B, the welding current Iw continues to have a low level current value during the delay period from time t4 to t41. After that, from time t41, the welding current Iw rapidly increases to a peak value, and then gradually decreases to a large current value. During the large current arc period from time t41 to t61, the feedback control of the welding power supply is performed by the voltage error amplification signal Ev in FIG. 1, so that the constant voltage characteristic is obtained. Therefore, the value of the welding current Iw during the high current arc period changes depending on the arc load.

At time t61, when the current drop time determined by the current drop time setting signal Tdr in FIG. 1 elapses after the arc is generated at time t4, the small current period signal Std changes to the High level as shown in FIG. do. In response to this, the welding power supply is switched from the constant voltage characteristic to the constant current characteristic. Therefore, as shown in FIG. 6B, the welding current Iw drops to a low level current value and maintains that value until the time t7 when the short circuit occurs. Similarly, as shown in FIG. 6C, the welding voltage Vw also decreases. The small current period signal Std returns to the Low level when a short circuit occurs at time t7.

In the figure, the forward deceleration period Tsd (normal feed deceleration period setting signal Tsdr in FIG. 1), the reverse feed deceleration period Trd (reverse feed deceleration period setting signal Trdr in FIG. 1), and the reverse feed acceleration period Tsu (reverse in FIG. 1). The feed acceleration period setting signal Tsur) and the normal feed acceleration period Tsu (the normal feed acceleration period setting signal Tsur in FIG. 1) are selected from the processes 1) to 6) by the pull feed rate correction circuit FH in FIG. One is selected and corrected and controlled. By this correction control, the accommodation capacity of the intermediate wire accommodating portion in FIG. 1 is controlled to be equal to the target value, so that the average value of the pull feed rate Fw is constant even if the short circuit period and the arc period fluctuate. Can be kept.

Process 1) When only the forward deceleration period setting signal Tsdr is corrected and controlled At time t1, when the short-circuit discrimination signal Sd shown in FIG. At that time, the accommodation error amplification signal Ew in FIG. 1 corrects and controls (modulates) the normal feed deceleration period initial value setting signal Tsds in FIG. 1, and outputs the forward feed deceleration period setting signal Tsdr = Tsds + Ew. When the accommodation signal Wb in FIG. 1 is larger than the accommodation setting signal Wbr in FIG. 1, the forward deceleration period setting signal Tsdr becomes longer than the initial value, and the accommodation signal Wb decreases and approaches the set value. It will be. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes shorter than the initial value, and the accommodation signal Wb increases and approaches the set value. ..

Process 2) When only the reverse feed / deceleration period setting signal Trdr is corrected and controlled At time t4, when the short-circuit discrimination signal Sd shown in FIG. , The capacity error amplification signal Ew at that time corrects and controls (modulates) the reverse feed deceleration period initial value setting signal Trds in FIG. 1, and outputs the reverse feed deceleration period setting signal Trdr = Trds-Ew. When the accommodating amount signal Wb is larger than the accommodating amount setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, and the accommodating amount signal Wb decreases and approaches the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the accommodation signal Wb increases and approaches the set value. ..

Process 3) When correcting and controlling both the forward deceleration period setting signal Tsdr and the reverse deceleration period setting signal Trdr Both the above processes 1) and 2) are performed. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodation amount signal Wb is smaller than the accommodation amount setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, and the reverse feed deceleration period setting signal Trdr becomes longer than the initial value and accommodates. The quantity signal Wb increases and approaches the set value.

Process 4) When the forward deceleration period setting signal Tsdr and the reverse feed acceleration period setting signal Trur are corrected and controlled. At time t1, the short-circuit discrimination signal Sd shown in FIG. Then, when the normal feed deceleration period Tsd starts, the normal feed deceleration period initial value setting signal Tsds is corrected and controlled (modulation control) by the accommodation error amplification signal Ew at that time, and the normal feed deceleration period setting signal Tsdr = Tsds + Ew is output. do. At the same time, the reverse feed acceleration period initial value setting signal Trus in FIG. 1 is corrected and controlled (modulation control) by the capacity error amplification signal Ew, and the reverse feed acceleration period setting signal Trur = Trus-Ew is output. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, the reverse acceleration period setting signal Trur becomes shorter than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr is shorter than the initial value, and the reverse acceleration period setting signal Trur is longer than the initial value and is accommodated. The quantity signal Wb increases and approaches the set value. Here, in the process 4), since Tsdr + Trur becomes a constant value, the short-circuit period can be maintained at a substantially constant value even if correction control is performed, and the welded state can be stabilized.

Process 5) When the reverse feed deceleration period setting signal Trdr and the forward feed acceleration period setting signal Tsur are corrected and controlled. At time t4, the short circuit discrimination signal Sd shown in FIG. Then, when the reverse feed deceleration period Trd starts, the reverse feed deceleration period initial value setting signal Trds is corrected and controlled (modulation control) by the accommodation error amplification signal Ew at that time, and the reverse feed deceleration period setting signal Trdr = Trds-Ew. Is output. At the same time, the positive feed acceleration period initial value setting signal Tsus of FIG. 1 is corrected and controlled (modulation control) by the above-mentioned capacity error amplification signal Ew, and the normal feed acceleration period setting signal Tsur = Tsus + Ew is output. When the accommodation signal Wb is larger than the accommodation setting signal Wbr, the reverse feed deceleration period setting signal Trdr is shorter than the initial value, the forward acceleration period setting signal Tsur is longer than the initial value, and the accommodation signal Wb. Will decrease and approach the set value. On the contrary, when the accommodating amount signal Wb is smaller than the accommodating amount setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the forward feed acceleration period setting signal Tsur becomes shorter than the initial value and accommodates. The quantity signal Wb increases and approaches the set value. Here, in the process 5), since Trdr + Tsur becomes a constant value, the arc period can be maintained at a substantially constant value even if correction control is performed, and the welded state can be stabilized.

Process 6) When correcting and controlling four of the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the reverse feed deceleration period setting signal Trdr, and the forward feed acceleration period setting signal Tsur. ) Do both. When the accommodation amount signal Wb is larger than the accommodation amount setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes longer than the initial value, the reverse feed acceleration period setting signal Trur becomes shorter than the initial value, and the reverse feed deceleration period. The setting signal Trdr becomes shorter than the initial value, the normal feed acceleration period setting signal Tsur becomes longer than the initial value, and the accommodation signal Wb decreases and approaches the set value. On the contrary, when the accommodation signal Wb is smaller than the accommodation setting signal Wbr, the forward deceleration period setting signal Tsdr is shorter than the initial value, and the reverse acceleration period setting signal Trur is longer than the initial value, and vice versa. The feed / deceleration period setting signal Trdr becomes longer than the initial value, the forward acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases to approach the set value. Here, in the process 6), since Tsdr + Trur and Trdr + Tsur each have constant values, the short-circuit period and the arc period can be maintained at substantially constant values even if correction control is performed, and the welded state can be stabilized. ..

A numerical example of the waveform parameter of the pull feed rate Fw is shown below.
Forward peak value Wsp = 50m / min, reverse peak value Wrp = -30m / min
Forward feed peak period Tsp ≒ 3 ms (not a predetermined value), reverse feed peak period Trp ≒ 1 ms (not a predetermined value), forward feed acceleration period initial value = 2 ms, forward feed deceleration period initial value = 1 ms, reverse feed acceleration period Initial value = 2ms, reverse feed deceleration period Initial value = 1ms

According to the first embodiment described above, the normal feed deceleration period and / or the reverse feed deceleration period of the pull feed rate is corrected based on the capacity of the intermediate wire accommodating portion. In the forward / reverse feed arc welding method, the forward feed period and the reverse feed period are switched in synchronization with the occurrence timing of the short circuit period and the arc period. For this reason, if the wire protrusion length, advance angle, welding speed, etc. change during welding and the time ratio between the short circuit period and the arc period changes, the time ratio between the normal feed period and the reverse feed period also changes. , The average feed rate of the welded wire (the average value of the pull feed rate) changes. When the average feeding rate changes, the amount of welding changes, so the welding quality deteriorates. In the present embodiment, when the time ratio between the normal feed period and the reverse feed period changes and the average value of the pull feed rate changes, a difference occurs between the push feed rate and the constant feed rate. As a result, an error occurs between the accommodation capacity of the intermediate wire accommodating portion and the target value. By correcting the forward deceleration period and / or the reverse feed deceleration period so that this error becomes 0, the average value of the pull feed rate and the push feed rate can be made equal. Therefore, the average value of the pull feeding rate can be returned to a predetermined value. Further, in semi-automatic welding in which a welding worker manually operates a welding torch to perform welding, fluctuations in wire protrusion length, advance angle, welding speed, etc. due to camera shake of the welding worker become large. Even in such semi-automatic welding, if the present embodiment is adopted, the fluctuation of the arc length due to the fluctuation can be suppressed, and the welding state can be stabilized.

Further, according to the present embodiment, the correction control of the forward deceleration period is performed based on the capacity at the start of the forward deceleration period, and the reverse feed deceleration period is performed based on the capacity at the start of the reverse deceleration period. It is desirable to perform correction control. By doing so, the transient response of the correction control can be improved, so that the average value of the pull feeding speed can be kept more constant.

Further, according to the present embodiment, when the correction control of the normal feed deceleration period is performed, the reverse feed acceleration period is corrected and controlled so that the total value of the normal feed deceleration period and the reverse feed acceleration period becomes constant. When the correction control of the reverse feed deceleration period is performed, it is desirable to correct and control the forward feed acceleration period so that the total value of the reverse feed deceleration period and the forward feed acceleration period becomes constant. By doing so, the short-circuit period and the arc period can be brought closer to constant values, so that the welded state can be further stabilized.

1 Welding wire
2 Base material
3 arc
4 Welding torch
5 Feed roll CM Current comparison circuit Cm Current 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 ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal EW Capacity error amplification circuit Ew Capacity error amplification signal FC Pull feed control circuit Fc Pull feed control signal FCP Push feed control circuit Fcp Push feed control Signal FH Pull feed speed correction circuit FR Pull feed speed setting circuit F Pull feed speed setting signal FRP Push feed speed setting circuit Frp Push feed speed setting signal Fw Pull feed speed Fwp Push 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 PM Power supply main circuit R Current drainage resistor SD Short circuit discrimination circuit Sd Short-circuit discrimination signal STD Small current period circuit Std Small current period signal SW Power supply characteristic switching circuit TDR Current drop time setting circuit Tdr Current drop time setting signal TR Transistor Trd Reverse feed deceleration period Trdr Reverse feed deceleration period setting signal TRDS Reverse feed deceleration period Initial value setting circuit Trds Reverse feed deceleration period Initial value setting signal Trp Reverse feed peak period Tru Reverse feed acceleration period Trur Reverse feed acceleration period setting signal TRUS Reverse feed acceleration period initial value setting circuit Trus Reverse feed acceleration period Initial value setting signal Tsd Positive Forward deceleration period Tsdr Normal feed deceleration period setting signal TsdS Normal feed deceleration period initial value setting signal Tsds Positive feed deceleration period initial value setting signal Tsp Forward feed peak period Tsu Normal feed acceleration period Tsur Forward feed acceleration period setting signal TsuS Forward feed acceleration period Initial value setting signal Tsus Normal feed acceleration period Initial value setting signal VD Voltage detection circuit Vd Voltage detection signal Vw Welding voltage WB Intermediate wire accommodating part Wb Accommodating amount signal WBR Accommodating amount setting circuit Wbr Accommodating amount setting signal WL Reactor WM Pull side feeding Motor WMP Push side feed motor Wrp Reverse feed peak value WRR Reverse feed peak value setting circuit Wrr Reverse feed peak value setting signal Wsp Forward feed peak value WSR Forward feed peak value setting circuit Wsr Forward feed peak value setting signal

Claims (3)

Welding wire is fed by push-pull feed control by a push-side feed motor that rotates forward and a pull-side feed motor that repeats forward rotation and reverse rotation.
An intermediate wire accommodating portion for temporarily accommodating the welded wire is provided between the feeding path between the push-side feeding motor and the pull-side feeding motor, and the pull is based on the accommodating capacity of the intermediate wire accommodating portion. Correct the pull feed speed of the side feed motor and
In the arc welding control method in which short-circuit period and arc period are repeatedly welded,
Based on the capacity, the normal feed deceleration period and / or the reverse feed deceleration period of the pull feed rate is corrected and controlled.
An arc welding control method characterized by this. The correction control of the forward deceleration period is performed based on the capacity at the start of the forward deceleration period, and the correction of the reverse deceleration period is performed based on the capacity at the start of the reverse deceleration period. To control,
The arc welding control method according to claim 1. When the correction control of the forward feed deceleration period is performed, the reverse feed acceleration period is corrected and controlled so that the total value of the forward feed deceleration period and the reverse feed acceleration period becomes constant, and the reverse feed deceleration period is performed. When the correction control is performed, the normal feed acceleration period is corrected and controlled so that the total value of the reverse feed deceleration period and the forward feed acceleration period becomes constant.
The arc welding control method according to claim 1 or 2.

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