JP7053121B2 - Arc welding control method - Google Patents

Description

The present invention relates to an arc welding control method in which the feeding of welding wires is alternately switched between a normal feeding period and a reverse feeding period, and a short-circuit period and an arc period are repeatedly welded.

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

In order to further improve the welding quality, a forward / reverse feed arc welding method has been proposed in which the welding wire is repeatedly welded forward and backward. In the invention of Patent Document 1, the feeding of the welded wire is alternately switched between the normal feeding period and the reverse feeding period, the short circuit period and the arc period are repeated, and when an arc is generated during the reverse feeding period, the welding wire shifts to the normal feeding period. , Disclosed is an arc welding method in which when a short circuit occurs during a normal feed period, the welding shifts to a reverse feed period and welding is performed.

International Publication WO2016 / 039113 Publication No. 7

The length of the short-circuit period varies due to disturbances such as irregular motion of the molten pool and the molten state of the weld wire. In forward / reverse feed arc welding, there is a problem that the welding state is more susceptible to fluctuations in the short-circuit period than in normal arc welding in which only forward feed is performed.

Therefore, an object of the present invention is to provide an arc welding control method capable of stably maintaining a welded state even if a short-circuit period fluctuates in forward / reverse feed arc welding.

In order to solve the above-mentioned problems, the invention of claim 1 is
The feed of the welded wire is switched alternately between the normal feed period and the reverse feed period, the short circuit period and the arc period are repeated, and when an arc is generated during the reverse feed period, the process shifts to the normal feed period and the normal feed period. In the arc welding control method in which a short circuit occurs during the process, the process shifts to the reverse feed period and welding is performed.
The time length of the reverse feed deceleration period is controlled according to the time length of the short-circuit period.
The time length of the reverse feed deceleration period is controlled so that the time length of the reverse feed period becomes a predetermined value.
It is an arc welding control method characterized by this.

The invention of claim 2 is
The welding current is increased after the delay time has elapsed from the time of transition to the arc period, and the delay time changes according to the time length of the reverse feed deceleration period.
The arc welding control method according to claim 1, wherein the arc welding is controlled.

The invention of claim 3 is
The time length of the forward acceleration period is controlled according to the time length of the arc period.
The arc welding control method according to any one of claims 1 and 2 .

The invention of claim 4 is
The time length of the normal feed acceleration period is controlled so that the time length of the normal feed period becomes a predetermined value.
The arc welding control method according to claim 3 , wherein the method is characterized by the above.

According to the present invention, in forward / reverse feed arc welding, the welded state can be stably maintained even if the short circuit period fluctuates.

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

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

[Embodiment 1]
The invention of the first embodiment controls the time length of the reverse feed deceleration period according to the time length of the short circuit period.

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

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

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

The feed motor WM receives the feed control signal Fc, which will be described later, as an input, and alternately repeats forward feed and reverse feed to feed the weld wire 1 at the feed speed Fw. As the feed motor WM, a motor having a high transient response is used. In order to accelerate the rate of change of the feed rate Fw of the welding wire 1 and the reversal of the feed direction, the feed motor WM may be installed near the tip of the welding torch 4. Further, there is a case where two feeding motors WM are used to form a push-pull type feeding system.

The welding wire 1 is fed in 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 metal 2. A welding voltage Vw is applied between the feeding tip (not shown) in the welding torch 4 and the base metal 2, and the welding current Iw is energized.

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

The voltage setting circuit VR outputs a predetermined voltage setting signal Vr.

The voltage error amplification circuit EV amplifies the error between the voltage setting signal Vr (+) and the voltage detection signal Vd (-) by using the above voltage setting signal Vr and the above voltage detection signal Vd as inputs, and amplifies the voltage error. Output the signal Ev.

The average feed rate setting circuit FAR outputs a predetermined average feed rate setting signal Far.

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

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

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

The normal feed peak value setting circuit WSR receives the above-mentioned average feed rate setting signal Far as an input, and outputs a predetermined normal feed peak value setting signal Wsr corresponding to the average feed rate setting signal Far. The normal feed peak value setting signal Wsr is calculated in advance by an experiment so that the average value of the feed rate Fw and the value of the average feed rate setting signal Far are equal to each other. Then, the value of the normal feed peak value setting signal Wsr corresponding to the average feed rate setting signal Far is stored.

The reverse feed peak value setting circuit WRR receives the above-mentioned average feed rate setting signal Far as an input, and outputs a predetermined reverse feed peak value setting signal Wrr corresponding to the average feed rate setting signal Far. The reverse feed peak value setting signal Wrr is calculated in advance by an experiment so that the average value of the feed rate Fw and the value of the average feed rate setting signal Far are equal to each other. Then, the value of the reverse feed peak value setting signal Wrr corresponding to the average feed rate setting signal Far is stored.

The reverse feed period setting circuit TRR outputs a predetermined reverse feed period setting signal Trr.

The reverse feed period measurement circuit MTR receives the feed rate setting signal Fr, which will be described later, as an input, and the elapsed time from the time when the feed rate setting signal Fr changes from a positive value to a negative value (the start time of the reverse feed period). Is measured and the reverse feed period measurement signal Mtr is output.

The feed rate setting circuit FR includes the forward feed acceleration period setting signal Tsur, the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the forward feed peak value setting signal Wsr, and the above. The feed rate pattern generated by the following processing is fed by inputting the reverse feed peak value setting signal Wrr, the short circuit determination signal Sd, the reverse feed period setting signal Trr, and the reverse feed period measurement signal Mtr. It is output as the speed setting signal Fr, and the calculated reverse feed / deceleration period setting signal Trdr is output. When the feed rate setting signal Fr is a positive value, it is a normal feed period, and when it is a negative value, it is a reverse feed period.
1) Positive feed rate setting signal Fr that accelerates linearly from 0 to the positive normal feed peak value Wsp determined by the normal feed peak value setting signal Wsr during the normal feed acceleration period Tsur, which is determined by the forward feed acceleration period setting signal Tsur. Is output.
2) Subsequently, during the normal feed peak period Tsp, the feed rate setting signal Fr that maintains the above normal feed peak value Wsp is output.
3) When the short-circuit discrimination signal Sd changes from the Low level (arc period) to the High level (short-circuit period), it shifts to the forward deceleration period Tsd determined by the forward deceleration period setting signal Tsdr, and from the above normal feed peak value Wsp. The feed rate setting signal Fr that decelerates linearly to 0 is output.
4) Subsequently, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the feed rate accelerates linearly from 0 to the negative reverse feed peak value Wrp determined by the reverse feed peak value setting signal Wrr. The setting signal Fr is output.
5) Subsequently, during the reverse feed peak period Trp, the feed rate setting signal Fr that maintains the above reverse feed peak value Wrp is output.
6) When the short-circuit discrimination signal Sd changes from the High level (short-circuit period) to the Low level (arc period), the value of the reverse-feed period measurement signal Mtr is subtracted from the value of the reverse-feed period setting signal Trr to reduce the reverse-feed. The period setting signal Trdr is calculated and output. Then, during the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trd, the feed rate setting signal Fr that linearly decelerates from the above reverse feed peak value Wrp to 0 is output. By this operation, even if the short-circuit period fluctuates, the reverse feed period Tr is always equal to the value of the reverse feed period setting signal Trr.
7) By repeating the above 1) to 6), a feed rate setting signal Fr of a feed pattern that changes in a positive or negative trapezoidal wave shape is generated.

The feed control circuit FC receives the feed speed setting signal Fr as an input, and feeds the weld wire 1 at the feed rate Fw corresponding to the value of the feed rate setting signal Fr. Output to the above feed motor WM.

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

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

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

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

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

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

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

The current drop time setting circuit TDR calculates the current drop time Td by a predetermined current drop time calculation function that inputs the above average feed rate setting signal Far, and outputs the current drop time setting signal Tdr. The current drop time calculation function is, for example, Td (ms) = 0.5 × Far (m / min) + 4. When Far = 0 to 10 m / min is set, it changes in the range of Td = 4 to 9 ms. The current drop time calculation function is experimentally set to an appropriate value according to the diameter and material of the weld wire.

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

The delay time setting circuit TCR takes the above-mentioned reverse feed deceleration period setting signal Trdr as an input, multiplies this value by a predetermined coefficient, and outputs the delay time setting signal Tcr. The coefficient is, for example, 0.8. Therefore, the value of the delay time setting signal Tcr changes in proportion to the value of the reverse feed deceleration period setting signal Trdr.

The power supply characteristic switching circuit SW receives the above-mentioned current error amplification signal Ei, the above-mentioned voltage error amplification signal Ev, the above-mentioned short-circuit discrimination signal Sd, the above-mentioned delay time setting signal Tcr, and the above-mentioned small current period signal Std as inputs. Is performed, and the error amplification signal Ea is output.
1) From the time when the short-circuit discrimination signal Sd changes to the High level (short-circuit period) to the time when the short-circuit discrimination signal Sd changes to the Low level (arc period) and the delay time Tc determined by the delay time setting signal Tcr elapses. During the period, the current error amplification signal Ei is output as the error amplification signal Ea.
2) During the subsequent arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) During the period when the small current period signal Std becomes the High level during the subsequent arc period, the current error amplification signal Ei is output as the error amplification signal Ea.
By this circuit, the characteristics of the welding power supply become the constant current characteristic during the short circuit period, the delay period and the small current period, and become the constant voltage characteristic during the other arc period.

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

The feed rate Fw shown in FIG. 1A is controlled by the value of the feed rate setting signal Fr output from the feed rate setting circuit FR of FIG. The feed rate Fw is determined by the normal feed acceleration period Tsu determined by the normal feed acceleration period setting signal Tsur in FIG. 1, the normal feed peak period Tsp that continues until a short circuit occurs, and the positive feed deceleration period setting signal Tsdr in FIG. The feed deceleration period Tsd, the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Tru, the reverse feed peak period Trp and the reverse feed period Tr that continue until an arc is generated are the reverse feed period setting signals Trr in FIG. It is formed from the reverse feed deceleration period Trd that is automatically adjusted to the value of. Further, the normal feed peak value Wsp is determined by the normal feed peak value setting signal Wsr in FIG. 1 as a value corresponding to the average feed rate setting signal Far, and the reverse feed peak value Wrp is determined by the reverse feed peak value setting signal Wrr in FIG. It is determined as a value according to the average feed rate setting signal Far. As a result, the feed rate setting signal Fr becomes a feed pattern that changes in a substantially trapezoidal wave shape of positive and negative.

[Operation during short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the normal feed peak period Tsp, the welding voltage Vw drops sharply to a short circuit voltage value of several V as shown in FIG. The short-circuit discrimination signal Sd changes to the High level (short-circuit period). In response to this, the feed rate shifts to the predetermined normal feed deceleration period Tsd at times t1 to t2, and as shown in FIG. .. For example, the forward deceleration period Tsd = 1 ms is set.

As shown in FIG. 3A, the feed rate Fw enters the predetermined reverse feed acceleration period Tru at times t2 to t3, and accelerates from 0 to the above-mentioned reverse feed peak value Wrp. During this period, the short circuit period continues. For example, the reverse feed acceleration period Tru = 1 ms is set.

When the reverse feed acceleration period Tru ends at time t3, the feed rate Fw enters the reverse feed peak period Trp and becomes the above-mentioned reverse feed peak value Wrp, as shown in FIG. The reverse peak period Trp continues until an arc is generated at time t4. Therefore, the period from time t1 to t4 is the short circuit period. The reverse peak period Trp is not a predetermined value, but it is about 2 ms. Further, the reverse feed peak value Wrp changes depending on the average feed rate setting signal Far, but is set to about -30 to -50 m / min.

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

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

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

In response to the constriction detection signal Nd reaching the High level, the drive signal Dr in FIG. 1 becomes the Low level, so that the transistor TR in FIG. Will be inserted. At the same time, the current control setting signal Icr in FIG. 1 becomes smaller than the value of the low level current setting signal Ilr. Therefore, as shown in FIG. 3B, the welding current Iw sharply decreases from the peak value at the time of short circuit to the low level current value. Then, when the welding current Iw decreases to a low level current value, the drive signal Dr returns to the high level, so that the transistor TR is turned on and the current reduction resistor R is short-circuited. As shown in FIG. 3B, in the welding current Iw, since the current control setting signal Icr remains the low level current setting signal Ilr, the delay time Tc determined by the delay time setting signal Tcr of FIG. 1 from the arc re-occurrence. Maintains a low level current value until. Therefore, the transistor TR is turned off only during the period from the time when the constriction detection signal Nd changes to the High level until the welding current Iw decreases to the low level current value. As shown in FIG. 3C, the welding voltage Vw decreases once and then rises sharply because the welding current Iw becomes small. Each of the above-mentioned parameters is set to the following values, for example. Initial current = 40A, initial period = 0.5ms, short-circuit slope = 180A / ms, short-circuit peak value = 400A, low-level current value = 50A.

[Operation during the arc period from time t4 to t7]
At time t4, when the constriction progresses and an arc is generated due to the pinch force due to the reverse feed of the welding wire and the energization of the welding current Iw, the welding voltage Vw is an arc voltage value of several tens of V as shown in FIG. As shown in FIG. (D), the short-circuit discrimination signal Sd changes to the Low level (arc period). The reverse feed period measurement circuit MTR of FIG. 1 outputs the elapsed time from the time t2 when the feed rate Fw changes from a positive value to a negative value as a reverse feed period measurement signal Mtr. That is, the reverse feed period measurement signal Mtr measures the time length of the reverse feed period. It is assumed that the reverse feed period measurement signal Mtr = Mtr4 at time t4. At this time, at time t4, the reverse feed deceleration period Trd is calculated by subtracting the above Mtr4 from the value of the reverse feed period setting signal Trr in FIG. Then, the process shifts to the calculated reverse feed deceleration period Trd from time t4 to t5, and the feed rate Fw decelerates from the above reverse feed peak value Wrp to 0 as shown in FIG. For example, the reverse feed deceleration period Trd changes in the range of about 0.5 to 2 ms.

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

When the normal feed acceleration period Tsu ends at time t6, the feed rate Fw enters the normal feed peak period Tsp and becomes the above normal feed peak value Wsp, as shown in FIG. The arc period continues during this period. The forward peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. Then, when a short circuit occurs, the operation returns to the operation at time t1. The forward peak period Tsp is not a predetermined value, but it is about 4 ms. Further, the normal feed peak value Wsp varies depending on the average feed rate setting signal Far, but is set to about 30 to 50 m / min.

When an arc is generated at time t4, the welding voltage Vw rapidly increases to an arc voltage value of several tens of V, as shown in FIG. On the other hand, as shown in FIG. 3B, the welding current Iw continues to have a low level current value during the delay time Tc determined by the delay time setting signal Tcr of FIG. 1 from the time t4. Since the delay time Tc is proportional to the reverse feed deceleration period Trd, it is automatically set to an appropriate value even if the reverse feed deceleration period Trd changes. This is because the melting of the welding wire 1 is suppressed by reducing the current value during the reverse feed deceleration period Trd. In this way, the arc length at the end of the reverse feed deceleration period Trd can be precisely controlled by the reverse feed feed rate Fw. As a result, the arc generation state can be stabilized and the arc period can be adjusted accurately.

After that, the welding current Iw increases to a high current value. During the arc period in which the high current value is obtained, the feedback control of the welding power supply is performed by the voltage error amplification signal Ev in FIG. 1, so that the constant voltage characteristic is obtained.

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

The current drop time Td is a value corresponding to the average feed rate setting signal Far. The current drop time Td is about 0.5 to 1 ms before the time t7 when the short circuit occurs at the timing when the welding current Iw becomes a small current value (time t61 when the small current period signal Std becomes the High level). Is desirable. As a result, the timing at time t61 is during the forward peak period Tsp. If the current drop time Td is too short, the period t61 to t7 of the small current value becomes long, and the arc state becomes unstable. On the contrary, if the current drop time Td is too long, the current value is not small even if a short circuit occurs, so that the sputtering increases. That is, it is important that the current drop time Td is set to an appropriate value according to the welding conditions.

Hereinafter, the action and effect of the first embodiment described above will be described. According to the first embodiment, the time length of the reverse feed deceleration period is controlled according to the time length of the short circuit period. As a result, the following effects are obtained.
(1) When the short-circuit period fluctuates and becomes long due to disturbance, the reverse feed deceleration period is controlled to be short. During the reverse feed deceleration period, the weld wire is pulled up by reverse feed in the arc generation state. At this time, if the reverse feed deceleration period is shortened, the pull-up distance is shortened, so that the normal feed period is entered with the arc length short. As a result, the next short circuit occurs earlier and the arc period becomes shorter. Therefore, the repetition period of the short circuit period and the arc period is stabilized, and the fluctuation of the welding state is suppressed.
(2) On the other hand, when the short-circuit period fluctuates and becomes shorter due to disturbance, the reverse feed deceleration period is controlled to become longer. During the reverse feed deceleration period, the weld wire is pulled up by reverse feed in the arc generation state. At this time, if the reverse feed deceleration period is lengthened, the pulling distance becomes long, so that the normal feed period is entered with the arc length long. As a result, the next short circuit occurs late and the arc period becomes long. Therefore, the repetition period of the short circuit period and the arc period is stabilized, and the fluctuation of the welding state is suppressed.

Further, in the first embodiment, the time length of the reverse feed deceleration period is controlled so that the reverse feed period becomes a predetermined value. In this case as well, the longer the short-circuit period, the shorter the reverse feed deceleration period. The shorter the short circuit period, the longer the reverse feed deceleration period. As a result, the above-mentioned action and effect are obtained. Further, in this way, the control of the reverse feed deceleration period is simplified, and the stability of the control system is improved.

Further, in the first embodiment, the welding current is increased after the delay time elapses from the time when the arc period is entered, and the delay time changes according to the time length of the reverse feed deceleration period. In this way, the delay time is automatically set to an appropriate value even if the reverse feed deceleration period changes. Therefore, by reducing the current value during the reverse feed deceleration period, it is possible to suppress the melting of the weld wire and precisely control the arc length. As a result, the arc generation state can be stabilized and the arc period can be adjusted accurately.

[Embodiment 2]
In the invention of the second embodiment, in addition to the first embodiment, the time length of the forward acceleration period is controlled according to the time length of the arc period.

FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the second embodiment of the present invention. This figure corresponds to FIG. 1 described above, and the same blocks are designated by the same reference numerals, and the description thereof will not be repeated. In the figure, the normal feed peak period measurement circuit MTSP and the normal feed period setting circuit TSR are added to FIG. 1, and the normal feed acceleration period setting circuit TUR in FIG. 1 is replaced with the second forward feed acceleration period setting circuit TUR2. be. Hereinafter, these blocks will be described with reference to the same figure.

The normal feed period setting circuit TSR outputs a predetermined normal feed period setting signal Tsr.

The normal feed peak period measurement circuit MTSP receives the above-mentioned normal feed peak value setting signal Wsr and the above-mentioned feed rate setting signal Fr as inputs, and determines the time length of the normal feed peak period in which the feed rate setting signal Fr = Wsr. It measures and outputs the normal feed peak period measurement signal Mtsp.

The second forward feed acceleration period setting circuit TUR2 receives the above-mentioned forward feed deceleration period setting signal Tsdr, the above-mentioned forward feed period setting signal Tsr, and the above-mentioned forward feed peak period measurement signal Mtsp as inputs, and the forward feed acceleration period setting signal Tsur2. = Tsr-Tsdr-Mtsp is calculated and output. By this circuit, the time length of the normal feed acceleration period is controlled so that the time length of the normal feed period becomes equal to the value of the normal feed period setting signal Tsr.

The timing chart of each signal in the welding power supply of FIG. 3 showing the arc welding control method according to the second embodiment of the present invention is the same as that of FIG. 2 described above. However, the operation of the normal feed acceleration period Tsu at times t5 to t6 in FIG. 2 is different. The normal feed peak period measurement circuit MTSP of FIG. 3 measures the time length of the normal feed peak period Tsp. At time t5, the value of the normal feed period measurement signal Mtsp is the time length of the normal feed peak period Tsp in the previous cycle. Here, the normal feed acceleration period setting signal Tsur is calculated by subtracting the above-mentioned normal feed peak period measurement signal Mtsp and the normal feed deceleration period setting signal Tsdr from the value of the normal feed period setting signal Tsr in FIG. Then, the process shifts to the calculated forward acceleration period Tsu at times t5 to t6. During this normal feed acceleration period Tsu, the feed rate Fw accelerates from 0 to the above normal feed peak value Wsp, as shown in FIG. The arc period continues during this period. For example, the forward acceleration period Tsu varies in the range of about 0.5 to 2 ms.

Hereinafter, the effects of the above-mentioned second embodiment will be described. According to the second embodiment, in addition to the first embodiment, the time length of the forward acceleration period is controlled according to the time length of the arc period. As a result, in addition to the effect of the first embodiment, the following effects are exhibited.
(1) When the arc period fluctuates and becomes longer due to disturbance, the forward acceleration period of the next cycle is controlled to be shorter. During the normal feed acceleration period, the weld wire is forward feed in the arc generation state, so that the arc length is shortened. At this time, if the forward acceleration period is shortened, the arc length is quickly shortened, so that a short circuit occurs earlier and the arc period is shortened. As a result, the repetition period of the short circuit period and the arc period is stabilized, and the fluctuation of the welding state is suppressed.
(2) On the other hand, when the arc period fluctuates and becomes shorter due to disturbance, the normal feed acceleration period of the next cycle is controlled to become longer. When the forward acceleration period is lengthened, it takes time for the arc length to be shortened, a short circuit occurs later, and the arc period becomes longer. As a result, the repetition period of the short circuit period and the arc period is stabilized, and the fluctuation of the welding state is suppressed.

Further, in the second embodiment, the time length of the normal feed acceleration period is controlled so that the normal feed period becomes a predetermined value. In this case as well, the longer the arc period, the shorter the forward acceleration period. The shorter the arc period, the longer the forward acceleration period. As a result, the above-mentioned action and effect are obtained. Further, in this way, the control of the forward acceleration period is simplified, and the stability of the control system is improved.

1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll CM Current comparison circuit Cm Current comparison signal DR Drive circuit Dr Drive signal E Output voltage Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification Circuit Ev Voltage error Amplification signal FAR Average feed rate setting circuit Far Average feed rate setting signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit F Feed speed setting signal Fw Feed speed ICR Current control setting Circuit Icr Current control setting signal ID Current detection circuit Id Current detection signal ILR Low level current setting circuit Ilr Low level current setting signal Iw Welding current MTR Reverse feed period measurement circuit Mtr Reverse feed period measurement signal ND Constriction detection circuit Nd Constriction detection signal MTSP Positive peak period measurement circuit Mtsp Positive peak period measurement signal PM Power supply main circuit R Low current resistor SD Short circuit discrimination circuit Sd Short circuit discrimination signal STD Small current period circuit Std Small current period signal SW Power supply characteristic switching circuit Tc Delay time TCR delay Time setting circuit Tcr Delay time setting signal Td Current drop time TDR Current drop time setting circuit Tdr Current drop time setting signal TR Transistor Tr Reverse feed period Trd Reverse feed deceleration period Trdr Reverse feed deceleration period Setting signal Trp Reverse feed peak period TRR Back feed Period setting circuit Trr Reverse feed period setting signal Tru Reverse feed acceleration period TRUR Reverse feed acceleration period setting circuit Trur Reverse feed acceleration period setting signal Tsd Forward forward deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp Forward feed Peak period TSR Normal feed period setting circuit Tsr Normal feed period setting signal Tsu Normal feed acceleration period TUR Positive feed acceleration period setting circuit Tsur Positive feed acceleration period setting signal TUR2 Second normal feed acceleration period setting circuit VD Voltage detection circuit Vd Voltage detection signal VR voltage setting circuit Vr voltage setting signal Vw welding voltage WL reactor WM feed motor Wrp reverse feed peak value WRR reverse feed peak value setting circuit Wrr reverse feed peak value setting signal Wsp forward peak value WSR forward feed peak value setting circuit Wsr positive Feed peak value setting signal

Claims (4)

The feed of the welded wire is switched alternately between the normal feed period and the reverse feed period, the short circuit period and the arc period are repeated, and when an arc is generated during the reverse feed period, the process shifts to the normal feed period and the normal feed period. In the arc welding control method in which a short circuit occurs during the process, the process shifts to the reverse feed period and welding is performed.
The time length of the reverse feed deceleration period is controlled according to the time length of the short circuit period.
The time length of the reverse feed deceleration period is controlled so that the time length of the reverse feed period becomes a predetermined value.
An arc welding control method characterized by this. The welding current is increased after the delay time has elapsed from the time of transition to the arc period, and the delay time changes according to the time length of the reverse feed deceleration period.
The arc welding control method according to claim 1 . The time length of the forward acceleration period is controlled according to the time length of the arc period.
The arc welding control method according to any one of claims 1 and 2 . The time length of the normal feed acceleration period is controlled so that the time length of the normal feed period becomes a predetermined value.
The arc welding control method according to claim 3 .

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