JP7542381B2 - Arc welding control method - Google Patents

Description

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

In typical consumable electrode arc welding, the 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 arc welding, the welding wire and the base metal often enter a welding state in which short-circuit periods and arc periods alternate.

To further improve welding quality, a forward/reverse feed arc welding method has been proposed in which the welding wire is fed alternately in forward and reverse directions. Compared to conventional techniques with a constant feed speed, this forward/reverse feed arc welding method can stabilize the cycle of repeated short circuits and arcs, thereby improving welding quality by reducing the amount of spatter and improving the bead appearance.

In forward and reverse feed arc welding methods, it is necessary to switch between forward and reverse feed of the welding wire at high speed and high precision at about 100 Hz. For this reason, a push-pull feeding method is often adopted as the feeding method. Furthermore, an intermediate wire storage section that temporarily stores the welding wire is often provided between the feeding paths of 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. Therefore, when the welding conditions such as the set value of the welding voltage and the projection length change and the time ratio between the short circuit period and the arc period changes, the time ratio between the forward feed period and the reverse feed period also changes, and the average feed speed of the welding wire changes. When the average feed speed changes, the deposition amount changes, and the welding quality deteriorates. To address this problem, the inventions of Patent Documents 1 and 2 forward feed at a constant speed using the push side motor, detect the capacity of the intermediate wire storage section, and correct and control the pull feed speed of the pull side motor based on this capacity. This correction control suppresses changes in the average feed speed.

JP 2017-94380 A JP 2020-99945 A

In the correction control of the conventional technology, the forward feed peak value and/or reverse feed peak value of the pull feed speed are changed based on the capacity of the intermediate wire storage section. However, in semi-automatic welding in which a welding operator manually operates a welding torch, when this correction control is performed, the arc length fluctuates greatly due to fluctuations in the wire extension length, advance angle, welding speed, etc. caused by the welding operator's hand shaking, which can cause problems such as unstable welding conditions.

The present invention aims to provide an arc welding control method that can prevent the welding state from becoming unstable due to the welding operator's hand shaking in a forward/reverse feed arc welding method that corrects and controls the pull feed speed based on the capacity of the intermediate wire storage section.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
The welding wire is fed by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations;
an intermediate wire accommodating section for temporarily accommodating the welding wire is provided between a feed path of the push-side feed motor and the pull-side feed motor, and a pull feed speed of the pull-side feed motor is corrected based on an amount of the welding wire accommodated in the intermediate wire accommodating section;
1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising:
maintaining the reverse acceleration period and the forward acceleration period of the pull feed speed at predetermined values;
correcting and controlling a forward feed deceleration period and/or a reverse feed deceleration period of the pull feed speed based on the storage amount;
The present invention relates to an arc welding control method.

The invention of claim 2 is as follows:
performing the correction control of the forward transport deceleration period based on the capacity at a start point of the forward transport deceleration period, and performing the correction control of the reverse transport deceleration period based on the capacity at a start point of the reverse transport deceleration period;
2. The method for controlling arc welding according to claim 1 .

In order to solve the above-mentioned problems, the present invention provides a welding wire feeder that feeds a welding wire by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations,
an intermediate wire accommodating section for temporarily accommodating the welding wire is provided between a feed path between the push-side feed motor and the pull-side feed motor, and a pull feed speed of the pull-side feed motor is corrected based on an amount of the welding wire accommodated in the intermediate wire accommodating section;
1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising:
when the forward deceleration period of the pull feed speed is corrected and controlled based on the storage amount, the reverse acceleration period is corrected and controlled so that a sum of the forward deceleration period and the reverse acceleration period is constant,
When the reverse feed deceleration period of the pull feed speed is corrected and controlled based on the storage amount, the forward feed acceleration period is corrected and controlled so that a sum of the reverse feed deceleration period and the forward feed acceleration period becomes constant.
The present invention relates to an arc welding control method .

According to the present invention, in a forward/reverse feed arc welding method in which the pull feed speed is corrected and controlled based on the capacity of the intermediate wire storage section, it is possible to prevent the welding state from becoming unstable due to the welding operator's hand shaking.

1 is a block diagram of a welding power source for implementing an arc welding control method according to a first embodiment of the present invention. 2 is a timing chart of each signal in the welding power source of FIG. 1 , illustrating an arc welding control method according to the first embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

[First embodiment]
1 is a block diagram of a welding power source for carrying out an arc welding control method according to a first embodiment of the present invention. Each block will be described below with reference to the diagram.

The power supply main circuit PM receives a three-phase 200V or other commercial power supply (not shown), performs output control by inverter control or the like according to an error amplified signal Ea (described later), and outputs an output voltage E. Although not shown, this power supply main circuit PM includes a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smooths the rectified DC, an inverter circuit driven by the error amplified signal Ea described above that converts the smoothed DC into high-frequency AC, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency AC into DC.

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

The push side feed motor WMP receives a push feed control signal Fcp (described later) as an input and rotates in the forward direction to feed the welding wire 1 at a constant push feed speed Fwp. The pull side feed motor WM receives a pull feed control signal Fc (described later) as an input and alternates between forward and reverse rotation to feed the welding wire 1 at a 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 storage unit WB is provided in the feed path between the push side feed motor WMP and the pull side feed motor WM, temporarily stores the welding wire 1, and outputs a storage amount signal Wb according to the storage amount. The intermediate wire storage unit WB is commonly used in conventional technology such as Patent Document 1, so a detailed structure will be omitted. The storage amount of the welding wire 1 is detected by mechanical principles, electrical principles, optical principles, magnetic principles, or a combination of these principles.

The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 connected to the pull-side feed motor WM, and an arc 3 is generated between the base material 2 and the welding wire 1. 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 flows through it. A 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 amplifier circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed as inputs, amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-), and outputs the voltage error amplification signal Ev.

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 and outputs a short circuit determination signal Sd that goes to High level when this value is less than a predetermined short circuit determination value (approximately 10 V) and determines that the short circuit is in a short circuit period, and goes to Low level when this value is equal to or greater than this value and determines that the arc period is in an arc period.

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

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

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

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

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

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

The capacity setting circuit WBR outputs a predetermined capacity setting signal Wbr that is a target value. The capacity error amplifier circuit EW receives the capacity setting signal Wbr and the capacity signal Wb, amplifies the error between the capacity setting signal Wbr (-) and the capacity signal Wb (+), and outputs a capacity error amplification signal Ew. Ew = G (Wb - Wbr), where G is a positive amplification factor. Therefore, when the capacity signal Wb is greater than the target capacity setting signal Wbr, the capacity error amplification signal Ew is a positive value, and when the capacity signal Wb is less than the target capacity setting signal Wbr, the capacity error amplification signal Ew is a negative value.

The pull feed speed correction circuit FH receives the short circuit discrimination signal Sd, the forward acceleration period initial value setting signal Tsus, the forward deceleration period initial value setting signal Tsds, the reverse acceleration period initial value setting signal Trus, the reverse deceleration period initial value setting signal Trds, and the capacity error amplification signal Ew as inputs, selects one of the following processes 1) to 6), performs correction control, and outputs the forward acceleration period setting signal Tsur, the forward deceleration period setting signal Tsdr, the reverse acceleration period setting signal Trur, and the reverse deceleration period setting signal Trdr. The correction control (modulation control) shown below is performed for each period of the forward feed period and the reverse feed period. One period is about 10 ms. The correction control shown below is for P control, but PI control or PID control may also be used.

Process 1) When only the forward deceleration period setting signal Tsdr is corrected and controlled When the short circuit discrimination signal Sd changes to a high level (short circuit period) and the forward deceleration period starts, the forward deceleration period initial value setting signal Tsds is corrected and controlled (modulated) by the capacity error amplification signal Ew at that time, and the forward deceleration period setting signal Tsdr = Tsds + Ew is output. When the capacity signal Wb is larger than the capacity setting signal Wbr, the forward deceleration period setting signal Tsdr becomes longer than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward deceleration period setting signal Tsdr becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value. Then, the other signals are output as input signals, with Tsur = Tsus, Trur = Trus, and Trdr = Trds.

Process 2) When only the reverse deceleration period setting signal Trdr is corrected and controlled When the short circuit determination signal Sd changes to a low level (arc period) and the reverse deceleration period starts, the reverse deceleration period initial value setting signal Trds is corrected and controlled (modulated) by the capacity error amplification signal Ew at that time, and the reverse deceleration period setting signal Trdr = Trds - Ew is output. When the capacity signal Wb is larger than the capacity setting signal Wbr, the reverse deceleration period setting signal Trdr becomes shorter than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the reverse deceleration period setting signal Trdr becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value. Then, the other signals are output as input signals, with Tsur = Tsus, Tsdr = Tsds, and Trur = Trus.

Process 3) In the case where both the forward feed deceleration period setting signal Tsdr and the reverse feed deceleration period setting signal Trdr are corrected and controlled, both of the above processes 1) and 2) are performed. When the capacity signal Wb is larger than the capacity setting signal Wbr, the forward feed 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 capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value. The other signals are output as input signals with Tsur=Tsus and Trur=Trus.

Process 4) When both the forward deceleration period setting signal Tsdr and the reverse acceleration period setting signal Trur are corrected and controlled When the short circuit discrimination signal Sd changes to a high level (short circuit period) and the forward deceleration period starts, the forward deceleration period initial value setting signal Tsds is corrected (modulated) by the capacity error amplification signal Ew at that time, and the forward deceleration period setting signal Tsdr = Tsds + Ew is output. At the same time, the reverse acceleration period initial value setting signal Trus is corrected (modulated) by the capacity error amplification signal Ew, and the reverse acceleration period setting signal Trur = Trus - Ew is output. When the capacity signal Wb is larger than the capacity 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 capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed acceleration period setting signal Trur becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 4), Tsdr+Trur is a constant value, so even if correction control is performed, the short circuit period can be maintained at a substantially constant value, and the welding state can be stabilized. The other signals are output as input signals, with Tsur=Tsus and Trdr=Trds.

Process 5) In case of corrective control of both reverse feed deceleration period setting signal Trdr and forward feed acceleration period setting signal Tsur When the short circuit discrimination signal Sd changes to a low level (arc period) and the reverse feed deceleration period starts, the reverse feed deceleration period initial value setting signal Trds is correctively controlled (modulated) by the capacity error amplified signal Ew at that time, and the reverse feed deceleration period setting signal Trdr = Trds - Ew is output. At the same time, the forward feed acceleration period initial value setting signal Tsus is correctively controlled (modulated) by the capacity error amplified signal Ew, and the forward feed acceleration period setting signal Tsur = Tsus + Ew is output. When the capacity signal Wb is larger than the capacity setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, the forward feed acceleration period setting signal Tsur becomes longer than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, the forward feed acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 5), Trdr+Tsur becomes a constant value, so that even if correction control is performed, the arc period can be maintained at a substantially constant value, and the welding state can be stabilized. The other signals are output as input signals with Tsdr=Tsds and Trur=Trus.

Process 6) In the case where the four signals, forward feed deceleration period setting signal Tsdr, reverse feed acceleration period setting signal Trur, reverse feed deceleration period setting signal Trdr and forward feed acceleration period setting signal Tsur, are corrected and controlled: Processes 4) and 5) above are both performed. When the capacity signal Wb is larger than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes longer than its initial value, the reverse feed acceleration period setting signal Trur becomes shorter than its initial value, the reverse feed deceleration period setting signal Trdr becomes shorter than its initial value, the forward feed acceleration period setting signal Tsur becomes longer than its initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed acceleration period setting signal Trur becomes longer than the initial value, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, the forward feed acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 6), Tsdr+Trur and Trdr+Tsur are each constant, so that the short circuit period and the arc period can be maintained at approximately constant values even if correction control is performed, and the welding state can be stabilized.

The pull feed speed setting circuit FR receives 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 as inputs, and outputs a pull feed speed pattern generated by the following process as a pull feed speed setting signal Fr. When this pull 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) During the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, the pull feed speed setting signal Fr is output which linearly accelerates from 0 to the forward feed peak value Wsp, which is a positive value determined by the forward feed peak value setting signal Wsr.
2) Subsequently, during the forward feed peak period Tsp, the pull 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 a low level (arc period) to a high level (short circuit period), the process transitions to a forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and the pull feed speed setting signal Fr that linearly decelerates from the forward feed peak value Wsp to 0 is output.
4) Subsequently, during the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur, the pull feed speed setting signal Fr is output which linearly accelerates from 0 to the reverse peak value Wrp, which is a negative value determined by the reverse peak value setting signal Wrr.
5) Subsequently, during the reverse feed peak period Trp, the pull feed speed setting signal Fr for maintaining the reverse feed peak value Wrp is output.
6) When the short circuit determination signal Sd changes from a high level (short circuit period) to a low level (arc period), the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr begins, and the pull feed speed setting signal Fr that linearly decelerates the speed from the reverse feed peak value Wrp to 0 is output.
7) By repeating the above steps 1) to 6), a pull feed speed setting signal Fr is generated having a feed pattern that changes like a positive and negative trapezoidal wave.

The pull feed control circuit FC receives the pull feed speed setting signal Fr as input and outputs a pull feed control signal Fc to the pull side feed motor WM to feed the welding wire 1 at a pull feed speed Fw that corresponds to the value of the pull feed speed setting signal Fr.

The push feed speed setting circuit FRP outputs a predetermined push feed speed setting signal Frp of a positive value. The push feed control circuit FCP receives the push feed speed setting signal Frp and outputs a push feed control signal Fcp to the push side feed motor WMP to feed the welding wire 1 at a push feed speed Fwp that corresponds to the value of the push feed speed setting signal Frp.

The current-reducing resistor R is inserted between the reactor WL and the welding torch 4. The value of this current-reducing resistor R is set to a value (approximately 0.5 to 3 Ω) that is 50 times larger than the short-circuit load (approximately 0.01 to 0.03 Ω). When this current-reducing resistor R is inserted into the current 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 and is controlled to be turned on or off according to the drive signal Dr described below.

The constriction detection circuit ND receives the above short circuit determination signal Sd, the above voltage detection signal Vd, and the above current detection signal Id as inputs, and outputs a constriction detection signal Nd that determines that the constriction formation state has reached the reference state when the voltage rise value of the voltage detection signal Vd reaches a reference value when the short circuit determination signal Sd is at a high level (short circuit period) and goes to a high level, and goes to a low level when the short circuit determination signal Sd changes to a low level (arc period). In addition, the constriction 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 corresponding reference value. Furthermore, the value of the voltage detection signal Vd may be divided by the value of the current detection signal Id to calculate the resistance value of the droplet, and the constriction detection signal Nd may be changed to a high level when the differential value of this resistance value reaches a corresponding reference value.

The low-level current setting circuit ILR outputs a predetermined low-level current setting signal Ilr. The current comparison circuit CM receives this low-level current setting signal Ilr and the current detection signal Id as inputs, and outputs a current comparison signal Cm that goes to a high level when Id<Ilr and a low level when Id≧Ilr.

The drive circuit DR receives the current comparison signal Cm and the constriction detection signal Nd as inputs, and outputs a drive signal Dr to the base terminal of the transistor TR. The drive signal Dr changes to a low level when the constriction detection signal Nd changes to a high level, and then changes to a high level when the current comparison signal Cm changes to a high level. Therefore, when a constriction is detected, the drive signal Dr goes to a low level, the transistor TR is turned off, and the current-reducing resistor R is inserted in the current path, so that the welding current Iw passing through the short-circuit load is suddenly reduced. 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 goes to a high level, the transistor TR is turned on, and the current-reducing resistor R is short-circuited and returns to the normal state.

The current control setting circuit ICR receives the short circuit determination signal Sd, the low level current setting signal Ilr, and the constriction detection signal Nd, performs the following processing, and outputs a current control setting signal Icr.
1) When the short circuit determination signal Sd is at a low level (arc period), a current control setting signal Icr which becomes a low-level current setting signal Ilr is output.
2) When the short circuit determination signal Sd changes to a high level (short circuit period), a predetermined initial current setting value is output during a predetermined initial period, and thereafter, a current control setting signal Icr is output which rises to a predetermined short circuit peak setting value at a predetermined short circuit slope and maintains that value.
3) Thereafter, when the squeezing detection signal Nd changes to a high level, the current control setting signal Icr having 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 inputs, amplifies the error between the current control setting signal Icr(+) and the current detection signal Id(-), and outputs a current error amplification signal Ei.

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 short circuit detection signal Sd and the above current drop time setting signal Tdr as inputs, and outputs a small current period signal Std that goes to a high level when the time determined by the current drop time setting signal Tdr has elapsed since the short circuit detection signal Sd changed to a low level (arc period), and then goes to a low level when the short circuit detection signal Sd goes to a high level (short circuit period).

The power supply characteristics switching circuit SW receives the current error amplified signal Ei, the voltage error amplified signal Ev, the short circuit determination signal Sd, and the small current period signal Std as inputs, performs the following processing, and outputs an error amplified signal Ea.
1) During the period from the point at which the short circuit determination signal Sd changes to a high level (short circuit period) to the point at which a predetermined delay period has elapsed since the short circuit determination signal Sd changes to a low level (arc period), the current error amplified signal Ei is output as the error amplified signal Ea.
2) During the subsequent large current arc period, the voltage error amplified signal Ev is output as the error amplified signal Ea.
3) During the subsequent small current arc period in which the small current period signal Std is at a high level, the current error amplified signal Ei is output as the error amplified signal Ea.
This circuit causes the welding power supply to have constant current characteristics during the short circuit period, delay period and small current arc period, and constant voltage characteristics during other large current arc periods.

Figure 2 is a timing chart of each signal in the welding power source of Figure 1, which shows the arc welding control method according to the first embodiment of the present invention. Figure (A) shows the change over time of the pull feed speed Fw, Figure (B) shows the change over time of the welding current Iw, Figure (C) shows the change over time of the welding voltage Vw, Figure (D) shows the change over time of the short circuit determination signal Sd, Figure (E) shows the change over time of the small current period signal Std, and Figure (F) shows the change over time of the push feed speed Fwp. The operation of each signal will be explained below with reference to the figure.

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

[Operation during the short circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the forward feed peak period Tsp, as shown in Fig. 1C, the welding voltage Vw suddenly decreases to a short circuit voltage value of several volts, and the short circuit determination signal Sd changes to a high level (short circuit period) as shown in Fig. 1D. In response to this, the system transitions to a predetermined forward feed deceleration period Tsd from time t1 to t2, and the pull feed speed Fw decelerates from the forward feed peak value Wsp to 0 as shown in Fig. 1A.

As shown in FIG. 1A, the pull feed speed Fw enters a predetermined reverse acceleration period Tru between times t2 and t3, and accelerates from 0 to the reverse peak value Wrp described above. During this period, the short circuit period continues.

When the reverse acceleration period Tru ends at time t3, as shown in FIG. 1A, the pull feed speed Fw enters the reverse peak period Trp and becomes the reverse peak value Wrp described above. The reverse peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is the short circuit period.

As shown in FIG. 1B, the welding current Iw during the short circuit period from time t1 to t4 is a predetermined initial current value during a predetermined initial period. Thereafter, the welding current Iw rises at a predetermined short circuit slope, and when it reaches a predetermined short circuit peak value, it maintains that value.

As shown in FIG. 1C, the welding voltage Vw rises from the point where the welding current Iw reaches its peak value during a short circuit. This is because a constriction gradually forms in the droplet at the tip of the welding wire 1 due to the reverse feed of the welding wire 1 and the pinching force caused by the welding current Iw.

After that, when the voltage rise value of the welding voltage Vw reaches the reference value, it is determined that the state of the necking has reached the reference state, and the necking detection signal Nd in Figure 1 changes to a high level.

In response to the constriction detection signal Nd becoming high level, the drive signal Dr in FIG. 1 becomes low level, so that the transistor TR in FIG. 1 becomes off and the current reducing resistor R in FIG. 1 is inserted into the current path. At the same time, the current control setting signal Icr in FIG. 1 becomes small to the value of the low level current setting signal Ilr. For this reason, as shown in FIG. 1 (B), the welding current Iw suddenly 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 the low level current value, the drive signal Dr returns to high level, so that the transistor TR becomes on and the current reducing resistor R is short-circuited. As shown in FIG. 1 (B), the welding current Iw maintains the low level current value until a predetermined delay period has elapsed since the arc re-ignition, because the current control setting signal Icr remains the low level current setting signal Ilr. Therefore, the transistor TR is in the off state only during the period from when the squeezing detection signal Nd changes to a high level until the welding current Iw decreases to a low-level current value. As shown in FIG. 1C, the welding voltage Vw decreases once as the welding current Iw decreases, and then rises sharply. The above-mentioned parameters are set to the following values, for example: initial current = 40 A, initial period = 0.5 ms, short circuit slope = 175 A/ms, short circuit peak value = 400 A, low-level current value = 50 A, delay period = 0.5 ms.

[Operation during arc period from time t4 to t7]
At time t4, when the pinching force caused by the reverse feed of the welding wire and the flow of the welding current Iw causes the constriction to progress and an arc to be generated, as shown in Fig. 1C, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, and the short circuit determination signal Sd changes to a low level (arc period) as shown in Fig. 1D. In response to this, the system transitions to a predetermined reverse feed deceleration period Trd from time t4 to t5, and the pull feed speed Fw decelerates from the reverse feed peak value Wrp to 0 as shown in Fig. 1A.

When the reverse feed deceleration period Trd ends at time t5, a predetermined forward feed acceleration period Tsu begins from time t5 to t6. During this forward feed acceleration period Tsu, as shown in FIG. 1A, the pull feed speed Fw accelerates from 0 to the forward feed peak value Wsp. The arc period continues during this period.

When the forward acceleration period Tsu ends at time t6, as shown in FIG. 1A, the pull feed speed Fw enters the forward peak period Tsp and becomes the forward peak value Wsp described above. The arc period continues during this period as well. 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 that at time t1.

When an arc is generated at time t4, as shown in FIG. 1C, the welding voltage Vw increases rapidly to an arc voltage value of several tens of volts. On the other hand, as shown in FIG. 1B, the welding current Iw maintains a low-level current value during the delay period from time t4 to t41. After that, from time t41, the welding current Iw increases rapidly to a peak value, and then decreases gradually to a large current value. During this high-current arc period from time t41 to t61, feedback control of the welding power source is performed by the voltage error amplification signal Ev in FIG. 1, resulting in a constant voltage characteristic. 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 has elapsed since the arc was generated at time t4, the small current period signal Std changes to a high level, as shown in FIG. 1(E). In response to this, the welding power source is switched from a constant voltage characteristic to a constant current characteristic. As a result, as shown in FIG. 1(B), the welding current Iw drops to a low level current value and maintains that value until time t7 when a short circuit occurs. Similarly, as shown in FIG. 1(C), the welding voltage Vw also drops. When a short circuit occurs at time t7, the small current period signal Std returns to a low level.

In the figure, the forward feed deceleration period Tsd (forward feed deceleration period setting signal Tsdr in FIG. 1), reverse feed deceleration period Trd (reverse feed deceleration period setting signal Trdr in FIG. 1), reverse feed acceleration period Tsu (reverse feed acceleration period setting signal Tsur in FIG. 1), and forward feed acceleration period Tsu (forward feed acceleration period setting signal Tsur in FIG. 1) are corrected and controlled by the pull feed speed correction circuit FH in FIG. 1, which selects one from processes 1) to 6). This correction control controls the capacity of the intermediate wire storage section in FIG. 1 to be equal to the target value, so that the average pull feed speed Fw can be kept constant even if the short circuit period and arc period vary.

Process 1) When only the forward deceleration period setting signal Tsdr is corrected and controlled When the short circuit discrimination signal Sd shown in FIG. 1(D) changes to a high level (short circuit period) at time t1 and the forward deceleration period Tsd starts, the forward deceleration period initial value setting signal Tsds in FIG. 1 is corrected and controlled (modulated) by the capacity error amplification signal Ew in FIG. 1 at that time, and the forward deceleration period setting signal Tsdr = Tsds + Ew is output. When the capacity signal Wb in FIG. 1 is larger than the capacity setting signal Wbr in FIG. 1, the forward deceleration period setting signal Tsdr becomes longer than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward deceleration period setting signal Tsdr becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value.

Process 2) When only the reverse deceleration period setting signal Trdr is corrected and controlled When the short circuit determination signal Sd shown in FIG. 1(D) changes to a low level (arc period) at time t4 and the reverse deceleration period Trd starts, the reverse deceleration period initial value setting signal Trds in FIG. 1 is corrected and controlled (modulated) by the capacity error amplification signal Ew at that time, and the reverse deceleration period setting signal Trdr=Trds-Ew is output. When the capacity signal Wb is larger than the capacity setting signal Wbr, the reverse deceleration period setting signal Trdr becomes shorter than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the reverse deceleration period setting signal Trdr becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value.

Process 3) In the case where both the forward feed deceleration period setting signal Tsdr and the reverse feed deceleration period setting signal Trdr are corrected and controlled, both of the above processes 1) and 2) are performed. When the capacity signal Wb is larger than the capacity setting signal Wbr, the forward feed 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 capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value.

Process 4) When the forward deceleration period setting signal Tsdr and the reverse acceleration period setting signal Trur are corrected and controlled When the short circuit discrimination signal Sd shown in FIG. 1(D) changes to a high level (short circuit period) at time t1 and the forward deceleration period Tsd starts, the forward deceleration period initial value setting signal Tsds is corrected (modulated) by the capacity error amplification signal Ew at that time to output the forward deceleration period setting signal Tsdr = Tsds + Ew. At the same time, the reverse acceleration period initial value setting signal Trus in FIG. 1 is corrected (modulated) by the capacity error amplification signal Ew to output the reverse acceleration period setting signal Trur = Trus - Ew. When the capacity signal Wb is larger than the capacity 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 capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed acceleration period setting signal Trur becomes longer than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 4), Tsdr+Trur is a constant value, so that even if correction control is performed, the short circuit period can be maintained at a substantially constant value, and the welding state can be stabilized.

Process 5) In the case where both 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 determination signal Sd shown in FIG. 1(D) changes to a low level (arc period) at time t4 and the reverse feed deceleration period Trd starts, the reverse feed deceleration period initial value setting signal Trds is corrected (modulated) by the capacity error amplified signal Ew at that time, and the reverse feed deceleration period setting signal Trdr = Trds - Ew is output. At the same time, the forward feed acceleration period initial value setting signal Tsus in FIG. 1 is corrected (modulated) by the capacity error amplified signal Ew, and the forward feed acceleration period setting signal Tsur = Tsus + Ew is output. When the capacity signal Wb is larger than the capacity setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes shorter than the initial value, the forward feed acceleration period setting signal Tsur becomes longer than the initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, the forward feed acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 5), Trdr+Tsur becomes a constant value, so that even if correction control is performed, the arc period can be maintained at a substantially constant value, and the welding state can be stabilized.

Process 6) In the case where the four signals, forward feed deceleration period setting signal Tsdr, reverse feed acceleration period setting signal Trur, reverse feed deceleration period setting signal Trdr and forward feed acceleration period setting signal Tsur, are corrected and controlled: Processes 4) and 5) above are both performed. When the capacity signal Wb is larger than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes longer than its initial value, the reverse feed acceleration period setting signal Trur becomes shorter than its initial value, the reverse feed deceleration period setting signal Trdr becomes shorter than its initial value, the forward feed acceleration period setting signal Tsur becomes longer than its initial value, and the capacity signal Wb decreases and approaches the set value. Conversely, when the capacity signal Wb is smaller than the capacity setting signal Wbr, the forward feed deceleration period setting signal Tsdr becomes shorter than the initial value, the reverse feed acceleration period setting signal Trur becomes longer than the initial value, the reverse feed deceleration period setting signal Trdr becomes longer than the initial value, the forward feed acceleration period setting signal Tsur becomes shorter than the initial value, and the capacity signal Wb increases and approaches the set value. Here, in process 6), Tsdr+Trur and Trdr+Tsur are each constant, so that the short circuit period and the arc period can be maintained at approximately constant values even if correction control is performed, and the welding state can be stabilized.

Numerical examples of waveform parameters of the pull feed rate Fw are shown below.
Forward peak value Wsp = 50 m/min, reverse peak value Wrp = -30 m/min
Forward transport peak period Tsp ≈ 3 ms (not a specified value), reverse transport peak period Trp ≈ 1 ms (not a specified value), forward transport acceleration period initial value = 2 ms, forward transport deceleration period initial value = 1 ms, reverse transport acceleration period initial value = 2 ms, reverse transport deceleration period initial value = 1 ms

According to the above-mentioned embodiment 1, the forward feed deceleration period and/or reverse feed deceleration period of the pull feed speed are corrected based on the capacity of the intermediate wire storage section. In the forward and 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 wire protrusion length, forward 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 forward feed period and the reverse feed period also changes, so that the average feed speed of the welding wire (average value of the pull feed speed) changes. When the average feed speed changes, the amount of deposition changes, and the welding quality deteriorates. In this embodiment, when the time ratio between the forward feed period and the reverse feed period changes and the average value of the pull feed speed changes, a difference occurs with a constant push feed speed. As a result, an error occurs between the capacity of the intermediate wire storage section and the target value. By correcting the forward feed deceleration period and/or the reverse feed deceleration period so that this error becomes zero, the average values of the pull feed speed and the push feed speed can be made equal. This allows the average pull feed speed to be returned to a predetermined value. Furthermore, in semi-automatic welding, where the welding operator manually operates the welding torch, fluctuations in the wire extension length, advance angle, welding speed, etc., occur due to the welding operator's hand shaking. Even in such semi-automatic welding, by adopting this embodiment, it is possible to suppress the fluctuations in arc length caused by such fluctuations, and the welding state can be stabilized.

Furthermore, according to this embodiment, it is desirable to perform correction control of the forward feed deceleration period based on the capacity at the start of the forward feed deceleration period, and to perform correction control of the reverse feed deceleration period based on the capacity at the start of the reverse feed deceleration period. In this way, the transient response of the correction control can be improved, so that the average value of the pull feed speed can be kept more constant.

Furthermore, according to this embodiment, it is desirable to correct and control the reverse feed acceleration period so that the sum of the forward feed deceleration period and the reverse feed acceleration period becomes constant when the forward feed deceleration period is corrected and controlled, and to correct and control the forward feed acceleration period so that the sum of the reverse feed deceleration period and the forward feed acceleration period becomes constant when the reverse feed deceleration period is corrected and controlled. In this way, the short circuit period and the arc period can be brought closer to constant values, and the welding 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 Fr 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 Neck detection circuit Nd Neck detection signal PM Power supply main circuit 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 changeover circuit TDR Current fall time setting circuit Tdr Current fall 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 Forward feed deceleration period Tsdr Forward feed deceleration period setting signal TsdS Forward feed deceleration period initial value setting signal Tsds Forward feed deceleration period initial value setting signal Tsp Forward feed peak period Tsu Forward feed acceleration period Tsur Forward feed acceleration period setting signal TsuS Forward feed acceleration period initial value setting signal Tsus Forward feed acceleration period initial value setting signal VD Voltage detection circuit Vd Voltage detection signal Vw Welding voltage WB Intermediate wire accommodation section Wb Accommodation amount signal WBR Accommodation amount setting circuit Wbr Accommodation amount setting signal WL Reactor WM Pull side feed 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)

The welding wire is fed by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations;
an intermediate wire accommodating section for temporarily accommodating the welding wire is provided between a feed path of the push-side feed motor and the pull-side feed motor, and a pull feed speed of the pull-side feed motor is corrected based on an amount of the welding wire accommodated in the intermediate wire accommodating section;
1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising:
maintaining the reverse acceleration period and the forward acceleration period of the pull feed speed at predetermined values;
correcting and controlling a forward feed deceleration period and/or a reverse feed deceleration period of the pull feed speed based on the storage amount;
2. An arc welding control method comprising: performing the correction control of the forward transport deceleration period based on the capacity at a start point of the forward transport deceleration period, and performing the correction control of the reverse transport deceleration period based on the capacity at a start point of the reverse transport deceleration period;
2. The method of claim 1, wherein the arc welding is controlled by the control circuit. The welding wire is fed by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations;
an intermediate wire accommodating section for temporarily accommodating the welding wire is provided between a feed path of the push-side feed motor and the pull-side feed motor, and a pull feed speed of the pull-side feed motor is corrected based on an amount of the welding wire accommodated in the intermediate wire accommodating section;
1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising:
when the forward deceleration period of the pull feed speed is corrected and controlled based on the storage amount, the reverse acceleration period is corrected and controlled so that a sum of the forward deceleration period and the reverse acceleration period is constant,
When the reverse feed deceleration period of the pull feed speed is corrected and controlled based on the storage amount, the forward feed acceleration period is corrected and controlled so that a sum of the reverse feed deceleration period and the forward feed acceleration period becomes constant.
2. An arc welding control method comprising :

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