JP2022143142A - Arc-welding device - Google Patents

Abstract

To estimate states of constrictions formed on molten droplets without detecting a voltage of an arc-generation part.SOLUTION: An arc-welding device comprises: a short-circuit determining part SD that determines a short-circuit period and outputs a short-circuit determination signal Sd; a current reduction timer part ND that outputs a current decrease signal Nd when a reference time Tnr elapses after a start time of the short-circuit period, when the short-circuit determination signal Sd is input; an electricity control part PM that repeats the short-circuit period and an arc period while supplying an inter-output terminal voltage Vw and welding currents Iw to a space between a welding wire 1 and a base material 2, and when the current decrease signal Nd is input in the short-circuit period, reduces the welding currents Iw and then transfers the period to the arc period; an average short-circuit time calculating part TSA that calculates an average short-circuit time for each predetermined cycle when the short-circuit determination signal Sd is input and outputs an average short-circuit time calculation signal Tsa; and a reference time setting part TNR that sets the reference time Tnr on the basis of the average short-circuit time calculation signal Tsa.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding apparatus that feeds a welding wire and performs welding by repeating a short circuit period and an arc period.

In general consumable electrode arc welding, welding is performed by feeding a welding wire, which is a consumable electrode, at a constant speed to generate an arc between the welding wire and a base material. In consumable electrode arc welding, the welding wire and the base material are often welded to alternate short-circuit periods and arc periods.

To improve weld quality, neck detection controls are commonly used in which, upon detection of droplet necking during a short circuit, the welding current is reduced to a low level current value to re-ignite the arc. Neck detection control can significantly reduce the generation of spatter, resulting in higher quality weld results. In order to perform this necking detection control, it is necessary to accurately detect the necking state of the droplet from the voltage of the arc generating portion. For this reason, in order to detect the voltage at the arc generating portion, a dedicated detection wire is wired between the base metal and the welding torch. However, it takes time and effort to wire this detection line. Furthermore, since the welding torch moves during welding, there is a possibility that the detection wire will break and cause trouble. Furthermore, when welding large structures, it is difficult to detect the voltage at the arc generating portion.

In order to solve the above problem, in the invention of Patent Document 1, when a predetermined reference time elapses from the start of the short circuit, the welding current is reduced by estimating that the formation state of the constriction of the droplet has reached the reference state. I am letting In this way, since it is not necessary to detect the voltage of the arc generating portion, there is no need to install a detection line. However, in this control, the problem is what value the reference time should be set to. Since the state of constriction formation of droplets varies depending on various welding conditions such as welding wire material, type of shielding gas, welding current, welding voltage, welding speed, welding posture, wire projection length, etc., an appropriate standard is It is difficult to set the time in advance by experiment. If the reference time is shorter than the appropriate value, the welding current is reduced at the point when the state of droplet formation is not yet sufficient, so the timing of arc re-occurrence is delayed and the state of welding becomes unstable. Conversely, if the reference time is longer than the appropriate value, the arc will re-occur at a timing when the welding current is not sufficiently reduced, resulting in the generation of a large amount of spatter. Therefore, in the prior art, setting the reference time to an appropriate value is excessive.

Japanese Patent No. 5974984

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an arc welding apparatus capable of performing high-quality welding with less spatter under various welding conditions without detecting the voltage of the arc generating portion.

In order to solve the above-mentioned problems, the invention of claim 1 is
a feed motor for feeding welding wire;
a short-circuit discrimination unit that discriminates that the welding wire and the base material are in a short-circuit period and outputs a short-circuit discrimination signal;
a current decrease timer unit that receives the short circuit determination signal as input and outputs a current decrease signal when a reference time elapses from the start of the short circuit period;
A welding voltage and a welding current are supplied between the welding wire and the base material to repeat the short circuit period and the arc period, and the welding current is reduced when the current decrease signal is input during the short circuit period. and a power control unit for shifting to the arc period by
In an arc welding device with
an average short-circuit time calculation unit that receives the short-circuit determination signal as an input, calculates an average short-circuit time for each predetermined cycle, and outputs an average short-circuit time calculation signal;
a reference time setting unit that sets the reference time based on the average short circuit time calculation signal;
An arc welding device further comprising:

The invention of claim 2 is
The reference time setting unit sets a value obtained by subtracting a predetermined time from the value of the average short-circuit time calculation signal as the reference time.
The arc welding apparatus according to claim 1, characterized by:

The invention of claim 3 is
The feed motor forwards the welding wire during the arc period and reversely feeds it during the short-circuit period.
The arc welding apparatus according to claim 1 or 2, characterized by:

According to the arc welding apparatus of the present invention, high-quality welding with little spatter can be performed under various welding conditions without detecting the voltage of the arc generating portion.

1 is a block diagram of an arc welding device according to an embodiment of the invention; FIG. 2 is a timing chart of each signal in the arc welding apparatus of FIG. 1;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an arc welding apparatus according to an embodiment of the invention. Each block will be described below with reference to FIG.

The power control unit PM receives a commercial power supply (not shown) such as a three-phase 200V power supply, performs output control by inverter control or the like in accordance with an error amplification signal Ea described later, and outputs an output voltage E, whereby the welding wire 1 and the base material 2, the output terminal voltage Vw and the welding current Iw are supplied. Although not shown, the power control unit PM is driven by a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified direct current, and the error amplification signal Ea that converts the smoothed direct current into high-frequency alternating current. 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.

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

The feed motor WM feeds the welding wire 1 at a feed speed Fw by alternately repeating forward feed and reverse feed upon receiving a feed control signal Fc, which will be described later. Forward feeding means feeding the welding wire forward in a direction approaching the base metal, and reverse feeding means backward feeding in a direction away from the base metal. A motor with fast transient response is used for the feeding motor WM. In some cases, the feed motor WM is installed near the tip of the welding torch 4 in order to speed up the rate of change of the feed speed Fw of the welding wire 1 and the reversal of the feed direction. In some cases, two feeding motors WM are used to form a push-pull type feeding system.

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

The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. An 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, and amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-). , output the voltage error amplification signal Ev.

A current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. A voltage detection circuit VD detects a voltage Vw across the output terminals of the welding power source and outputs a voltage detection signal Vd. The short-circuit determination circuit SD receives the voltage detection signal Vd as an input, and when this value is less than a predetermined short-circuit determination value (about 10 V), it determines that there is a short-circuit period and becomes High level. It determines that it is in the arc period and outputs a short-circuit determination signal Sd that becomes Low level.

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

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

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

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

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

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

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

A feed control circuit FC receives the feed speed setting signal Fr as an input and outputs a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. Output to the feed motor WM.

A current reducing resistor R is inserted between the reactor WL and the welding torch 4 . The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is at least 50 times larger than the short-circuit load (about 0.01 to 0.03Ω). When this current reducing resistor R is inserted into the current path, the energy accumulated in the reactor WL and the reactor of the external cable is rapidly discharged.

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

The average short-circuit time calculation circuit TSA receives the short-circuit determination signal Sd as an input, calculates the moving average of the short-circuit time during which the short-circuit determination signal Sd is at a High level (short-circuit period) over a predetermined period, and outputs an average short-circuit time calculation signal Tsa. do. The predetermined cycle is a cycle in which a short circuit occurs, and is set to approximately 3 to 10 cycles. Therefore, every time a short circuit occurs, the average value of the short circuit time in the predetermined period immediately before that is calculated.

The reference time setting circuit TNR receives the average short circuit time calculation signal Tsa, subtracts a predetermined time from the value of the average short circuit time calculation signal Tsa, and outputs a reference time setting signal Tnr. The predetermined time is set to, for example, about 1 ms. At a predetermined time before the short circuit ends and the arc reoccurs, the state of formation of the constriction is the reference state. When the welding current is decreased at this timing, the welding current reaches the desired low level current value at the time of arc recurrence.

A current decrease timer circuit ND receives the short-circuit determination signal Sd and the reference time setting signal Tnr as inputs, and measures the time elapsed from when the short-circuit determination signal Sd is at High level (short-circuit period) and changed to High level. When the time reaches the reference time Tn determined by the reference time setting signal Tnr, it outputs the current decrease signal Nd that becomes High level for a short period of time.

The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. A current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as inputs, and generates a current comparison signal Cm that becomes High level when Id<Ilr and becomes Low level when Id≧Ilr. Output.

The drive circuit DR receives the current comparison signal Cm and the current reduction signal Nd as inputs, and changes to Low level when the current reduction signal Nd changes to High level. A drive signal Dr that changes to High level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the driving signal Dr becomes Low level, the transistor TR is turned off, and the current reducing resistor R is inserted in the conducting path, so that the welding current Iw passing through the short-circuited load rapidly decreases. . Then, when the value of the welding current Iw, which has suddenly decreased, decreases to the value of the low-level current setting signal Ilr, the drive signal Dr becomes High level, and the transistor TR is turned on, so that the current reducing resistor R is short-circuited and normally state.

The first arc period setting circuit TA1R outputs a predetermined first arc period setting signal Ta1r.

The first arc period circuit STA1 receives the short-circuit determination signal Sd and the first arc period setting signal Ta1r as inputs, and the short-circuit determination signal Sd changes to a low level (arc period), and a predetermined delay period Tc elapses. A first arc period signal Sta1 that is at a high level is output during a first arc period Ta1 predetermined by the first arc period setting signal Ta1r from the point of time when the first arc period setting signal Ta1r.

The first arc current setting circuit IA1R outputs a predetermined first arc current setting signal Ia1r.

The third arc period circuit STA3 receives the above short-circuit determination signal Sd, and becomes High level when a predetermined current drop time Td elapses after the short-circuit determination signal Sd changes to Low level (arc period). After that, when the short circuit determination signal Sd becomes High level (short circuit period), it outputs a third arc period signal Sta3 which becomes Low level.

The third arc current setting circuit IA3R outputs a predetermined third arc current setting signal Ia3r.

The current control setting circuit ICR receives the above short circuit determination signal Sd, the above low level current setting signal Ilr, the above current decrease signal Nd, the above first arc period signal Sta1, the above third arc period signal Sta3, the above The first arc current setting signal Ia1r and the third arc current setting signal Ia3r are input, the following processing is performed, and the current control setting signal Icr is output.
1) During the delay period from when the short circuit determination signal Sd changes to Low level (arc period) to when the first arc period signal Sta1 changes to High level, the current control setting is the value of the low level current setting signal Ilr. It outputs a signal Icr.
2) After that, when the first arc period signal Sta1 is at High level (first arc period), the current control setting signal Icr that becomes the first arc current setting signal Ia1r is output.
3) During the period (second arc period and third arc period) from when the first arc period signal Sta1 changes to Low level to when the third arc period signal Sta3 changes to Low level, the third arc current setting It outputs a current control setting signal Icr that becomes the signal Ia3r.
4) When the short-circuit determination signal Sd changes to a high level (short-circuit period), the current is set to a predetermined initial current set value during a predetermined initial period, and after that, a predetermined short-circuit slope and a predetermined short-circuit peak set value. and output a current control setting signal Icr that maintains that value.
5) After that, when the current decrease signal Nd changes to High level, the current control setting signal Icr having the value of the low level current setting signal Ilr is output.

A 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 the current It outputs an error amplified signal Ei.

The power supply characteristics switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, the first arc period signal Sta1, and the third arc period signal Sta3, and performs the following processing, It outputs an error amplified signal Ea.
1) During the second arc period Ta2 from when the first arc period signal Sta1 changes to Low level to when the third arc period signal Sta3 changes to High level, the voltage error amplification signal Ev is output as the error amplification signal Ea. .
2) During other periods, the current error amplification signal Ei is output as the error amplification signal Ea.
With this circuit, the characteristics of the welding power source are constant current characteristics during the short circuit period, delay period, first arc period Ta1 and third arc period Ta3, and constant voltage characteristics during the second arc period Ta2.

2 is a timing chart of each signal in the arc welding apparatus of FIG. 1. FIG. (A) shows the time change of the feed speed Fw, (B) shows the time change of the welding current Iw, and (C) shows the time change of the output terminal voltage Vw. (D) shows the time change of the short-circuit determination signal Sd, (E) shows the time change of the first arc period signal Sta1, (F) shows the time change of the third arc period signal Sta3, (G) in the same figure shows the time change of the current decrease signal Nd. The operation of each signal will be described below with reference to FIG.

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

[Operation during short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the forward peak period Tsp, the voltage Vw across the output terminals rapidly decreases to a short-circuit voltage value of several volts, as shown in FIG. Then, the short circuit determination signal Sd changes to High level (short circuit period). In response to this, a transition is made to a predetermined normal feed deceleration period Tsd from time t1 to t2, and the feed speed Fw is reduced from the normal feed peak value Wsp to 0 as shown in FIG. . For example, the forward deceleration period Tsd is set to 1 ms.

As shown in FIG. 4A, the feeding speed Fw enters a predetermined reverse feeding acceleration period Tru from time t2 to t3, and accelerates from 0 to the reverse feeding peak value Wrp. During this period, the short-circuit period continues. For example, the reverse acceleration period Tru is set to 1 ms.

When the reverse feeding acceleration period Tru ends at time t3, the feeding speed Fw enters the reverse feeding peak period Trp and becomes the reverse feeding peak value Wrp, as shown in FIG. The reverse feed peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is the short-circuit period. Although the reverse transmission peak period Trp is not a predetermined value, it is approximately 3 ms. Also, for example, the backward feed peak value Wrp is set to -40 m/min.

As shown in FIG. 4B, 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 at a predetermined short-circuiting slope, and when it reaches a predetermined short-circuiting peak value, the value is maintained.

As shown in (C) of the figure, the voltage Vw between the output terminals rises from around the time when the welding current Iw reaches the short-circuit peak value. This is because constriction is gradually formed in the droplet at the tip of the welding wire 1 due to the action of the pinch force due to the welding wire 1 being reversed and the welding current Iw.

When the elapsed time from the start of the short-circuit period at time t1 reaches the reference time Tn, it is assumed that the state of formation of the constriction has reached the reference state, and at time t31, a current decrease signal is generated as shown in FIG. Nd changes to High level for a short time. The reference time Tn is set by the reference time setting signal Tnr shown in FIG. Further, the reference time setting signal Tnr is set as a value obtained by subtracting a predetermined time from the value of the average short circuit time calculation signal Tsa of FIG. The average short-circuit time calculation signal Tsa is calculated by moving the short-circuit time over a predetermined cycle. For example, the short circuit from time t1 is the m-th short circuit, the predetermined cycle is 3, and the short circuit times in the predetermined cycle are Ts(m-3), Ts(m-2), and Ts(m-1). Then, the reference time setting signal Tsa(m) in the m-th short-circuit period is calculated as follows.
Tsa(m)=(Ts(m-3)+Ts(m-2)+Ts(m-1))/3
The short-circuit time becomes a substantially constant value for each of various welding conditions. Therefore, by calculating the average short-circuit time, it is possible to estimate the short-circuit time under the current welding conditions. Then, if the reference time Tm is set by subtracting a predetermined time from the average short circuit time, the formation state of the constriction will be the reference state in the state a predetermined time before the short circuit ends and the arc reoccurs. It can be assumed that For example, the value of the average short-circuit time calculation signal Tsa is approximately 5 ms, the predetermined time is 0.5 ms, and the reference time Tn is approximately 4.5 ms. As described above, the reference time Tn can be automatically set to an appropriate value under various welding conditions.

At time t31, as shown in FIG. 1(G), the drive signal Dr in FIG. is turned off, and the current reducing resistor R shown in FIG. 1 is inserted into the conducting path. At the same time, the current control setting signal Icr of FIG. 1 decreases to the value of the low level current setting signal Ilr. As a result, the welding current Iw sharply decreases from the short-circuit peak value to the low level current value, as shown in FIG. When the welding current Iw decreases to the low level current value, the drive signal Dr returns to the high level, so that the transistor TR is turned on and the current reducing resistor R is short-circuited. As shown in (B) of the figure, the welding current Iw is at a low level until the predetermined delay period Tc elapses after the recurrence of the arc because the current control setting signal Icr remains at the low level current setting signal Ilr. Maintain current value. Therefore, the transistor TR is turned off only during the period from when the current decrease signal Nd changes to High level to when the welding current Iw decreases to the low level current value. As shown in (C) of the figure, the voltage Vw between the output terminals decreases once and then rises sharply because the welding current Iw becomes smaller. Each parameter mentioned above is set to the following values, for example. Initial current = 40 A, initial period = 0.5 ms, slope at short circuit = 180 A/ms, peak value at short circuit = 400 A Low level current value = 50 A, delay period Tc = 1 ms.

[Operation during arc period from time t4 to t7]
At time t4, when the constriction progresses due to the pinch force due to the reverse feeding of the welding wire and the application of the welding current Iw, and an arc is generated, the voltage Vw between the output terminals is several tens of volts as shown in FIG. Since the voltage rises rapidly, the short-circuit determination signal Sd changes to Low level (arc period) as shown in (D) of FIG. In response to this, a transition is made to a predetermined reverse feeding deceleration period Trd from time t4 to t5, and the feeding speed Fw is reduced from the reverse feeding peak value Wrp to 0 as shown in FIG. . For example, the reverse deceleration period Trd is set to 1 ms.

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

When the normal feeding acceleration period Tsu ends at time t6, the feeding speed Fw enters the normal feeding peak period Tsp and reaches the normal feeding 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 time t1. Although the forward transmission peak period Tsp is not a predetermined value, it is approximately 5 ms. Also, for example, the forward feed peak value Wsp is set to 60 m/min.

When an arc occurs at time t4, the output terminal voltage Vw rapidly increases to several tens of volts as shown in (C) of the figure. On the other hand, as shown in (B) of the figure, the welding current Iw continues at a low level current value during the delay period Tc from time t4. This is because if the current value is increased immediately after the arc is generated, the reverse feeding of the welding wire and the melting of the welding wire due to the welding current are added together, resulting in a rapid lengthening of the arc and an unstable welding state. This is because there are cases.

When the delay period Tc ends at time t51 during the forward acceleration period Tsu, the first arc period signal Sta1 changes to a high level as shown in FIG. It shifts to one arc period Ta1. During the first arc period Ta1, constant current control continues, and a predetermined first arc current Ia1 determined by the first arc current setting signal Ia1r shown in FIG. 1 flows as shown in FIG. 1(B). As shown in (C) of the figure, the voltage Vw between the output terminals becomes a value determined by the current value and the arc load, and becomes a large value. For example, the delay period Tc is about 1 ms, the first arc period Ta1 is about 1 ms, and the first arc current Ia1 is about 400A.

At time t62, when a predetermined current drop time Td has elapsed from arc occurrence time t4, the third arc period signal Sta3 changes to a high level, as shown in FIG. The period from time t61 to t62 is the second arc period Ta2. Constant voltage control is performed during the second arc period Ta2. As shown in FIG. 4B, the second arc current Ia2 varies depending on the arc load, but is smaller than the first arc current Ia1 and larger than the third arc current Ia3. That is, the output is controlled so that Ia1>Ia2>Ia3. As shown in FIG. 4C, the output terminal voltage Vw is controlled to a predetermined value by constant voltage control, and becomes an intermediate value between the voltage value in the first arc period Ta1 and the voltage value in the third arc period Ta3. Although the second arc period Ta2 is not a predetermined value, it is approximately 4.5 ms.

A period from time t62 when the third arc period signal Sta3 changes to High level to time t7 when a short circuit occurs is the third arc period Ta3. Constant current control is performed during the third arc period Ta3. As shown in FIG. 4B, a predetermined third arc current Ia3 determined by the third arc current setting signal Ia3r of FIG. 1 is applied. As shown in (C) of the figure, the output terminal voltage Vw is a value determined by the current value and the arc load. For example, the third arc current Ia3 is set to 60A. Although the third arc period Ta3 is not a predetermined value, it is approximately 0.5 ms.

In the above-described embodiment, the welding wire is fed forward during the arc period and reversed during the short-circuit period, but it may be fed at a constant speed during the entire period.

According to the arc welding apparatus according to the present embodiment described above, an average short-circuit time calculation unit that receives a short-circuit determination signal as an input, calculates an average short-circuit time for each predetermined cycle, and outputs an average short-circuit time calculation signal; and a reference time setting unit that sets the reference time based on the calculated signal. In the present embodiment, the standard time for determining the timing for decreasing the welding current is automatically set based on the average short-circuit time by estimating that the state of formation of the constriction has reached the standard state. Therefore, the reference time can be automatically set to an appropriate value according to various welding conditions. As a result, in the present embodiment, high-quality welding with less spatter can be performed under various welding conditions without detecting the voltage of the arc generating portion.

Furthermore, according to the present embodiment, it is preferable that the reference time setting unit sets a value obtained by subtracting a predetermined time from the value of the average short-circuit time calculation signal as the reference time. In this way, the welding current can be brought to a low level current value immediately before the arc re-occurs, so that the amount of spatter generated can be reduced and the transition to the arc period can be made smooth.

Furthermore, according to this embodiment, the feed motor preferably feeds the welding wire forward during the arc period and reversely during the short-circuit period. When the forward and reverse feed control of the welding wire is performed, variations in the short-circuit time become smaller than when the constant-speed feed control is performed. Therefore, the accuracy of estimating the formation state of the constriction based on the reference time is improved. As a result, the amount of spatter generated can be further reduced.

1 welding wire
2 Base material
3 arcs
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 FC Feeding control circuit Fc Feeding control signal FR Feeding speed setting circuit Fr Feeding speed setting signal Fw Feeding speed Ia1 First arc current IA1R First arc Current setting circuit Ia1r First arc current setting signal Ia2 Second arc current Ia3 Third arc current IA3R Third arc current setting circuit Ia3r Third arc current setting signal 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 Current reduction timer circuit Nd Current reduction signal PM Power controller R Current reduction resistor SD Short-circuit discrimination circuit Sd Short-circuit discrimination signal STA1 First arc period circuit Sta1 First arc period signal STA3 Third arc period circuit Sta3 Third arc period signal SW Power supply characteristics switching circuit Tc Delay period TA1R First arc period setting circuit Ta1r First arc period setting signal Td Current drop time Tn Reference time TNR Reference time setting Circuit Tnr Reference time setting signal TR Transistor Trd Reverse transfer deceleration period TRDR Reverse transfer deceleration period setting circuit Trdr Reverse transfer deceleration period setting signal Trp Reverse transfer peak period Tru Reverse transfer acceleration period TRUR Reverse transfer acceleration period setting circuit Trur Reverse transfer acceleration period setting Signal TSA Average short-circuit time calculation circuit Tsa Average short-circuit time calculation signal Tsd Forward deceleration period TSDR Forward deceleration period setting circuit Tsdr Forward deceleration period setting signal Tsp Forward peak period Tsu Forward acceleration period TSUR Forward acceleration period setting circuit Tsur Forward acceleration period setting signal VD Voltage detection circuit Vd Voltage detection signal Vw Output terminal voltage WL Reactor WM Feed motor Wrp Reverse feed peak value WRR Reverse feed peak value setting circuit Wrr Reverse feed peak value setting signal Wsp Forward feed peak value WSR Forward peak value setting circuit Wsr Forward peak value setting signal

Claims (3)

a feed motor for feeding welding wire;
a short-circuit discrimination unit that discriminates that the welding wire and the base material are in a short-circuit period and outputs a short-circuit discrimination signal;
a current decrease timer unit that receives the short circuit determination signal as input and outputs a current decrease signal when a reference time elapses from the start of the short circuit period;
A welding voltage and a welding current are supplied between the welding wire and the base material to repeat the short circuit period and the arc period, and the welding current is reduced when the current decrease signal is input during the short circuit period. and a power control unit for shifting to the arc period by
In an arc welding device with
an average short-circuit time calculation unit that receives the short-circuit determination signal as an input, calculates an average short-circuit time for each predetermined cycle, and outputs an average short-circuit time calculation signal;
a reference time setting unit that sets the reference time based on the average short circuit time calculation signal;
An arc welding device further comprising: The reference time setting unit sets a value obtained by subtracting a predetermined time from the value of the average short-circuit time calculation signal as the reference time.
The arc welding apparatus according to claim 1, characterized in that: The feed motor forwards the welding wire during the arc period and reversely feeds it during the short-circuit period.
The arc welding device according to claim 1 or 2, characterized in that:

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