JP2015030033A - Welding-current control method for welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent malfunction of droplet constriction detection control when a plurality of welding power sources are simultaneously used.SOLUTION: A common workpiece 2 is welded using arcs 31, 32 generated by a first welding power source PS1 and a second welding power source PS2, respectively, the first welding power source PS1 has a droplet constriction detection control function, and a maximum change ratio of a second welding current Iw2 of the second welding power source PS2 during arc period is set to be smaller in a case in which a first welding current Iw1 from the first welding power source PS1 is supplied than in a case in which the first welding current is not supplied. Consequently, even if the second welding current Iw2 changes due to a sudden change of an arc length, malfunction of a droplet constriction detection control of the first welding power source PS1 can be suppressed.

Description

  The present invention feeds a first welding wire from a first welding power source and energizes a first welding current to generate a first arc on a common workpiece and welds the second welding wire from a second welding power source. A welding apparatus that feeds and energizes a second welding current to generate a second arc on a common workpiece and performs welding. The first welding power source energizes a short-circuit load when detecting a constriction of droplets. The present invention relates to a welding current control method for a welding apparatus that regenerates a first arc by reducing a welding current.

  In the invention of Patent Document 1, in consumable electrode arc welding in which an arc period and a short-circuit period are alternately repeated between a welding wire and a workpiece, the constriction of droplets, which is a precursor to the occurrence of an arc again from the short-circuit period, is eliminated. The change in the voltage value or resistance value between the workpiece and the workpiece is detected when it reaches the squeezing detection reference value.When this squeezing is detected, the welding current flowing to the short-circuit load is suddenly reduced, and an arc is generated with a small current value Output control (necking detection control) is performed so that it occurs again. In this way, since the current value at the time of arc re-generation can be reduced, the amount of spatter generated can be reduced.

  By the way, a workpiece having a plurality of welding locations may be simultaneously welded using a plurality of welding power sources. Hereinafter, constriction detection control in such a case will be described with reference to the drawings.

  FIG. 7 is a configuration diagram of a welding apparatus for simultaneously welding two welding locations of one workpiece using two welding power sources. The two welding power sources both provide a constriction detection control function. Hereinafter, each component will be described with reference to FIG.

  The first welding power source PS1 outputs a first welding voltage Vw1 and a first welding current Iw1, and outputs a first feed control signal Fc1 to the first feeder FD1. The first feeder FD1 feeds the first welding wire 11 through the first welding torch 41 with the first feeding control signal Fc1 as an input. A first arc 31 is generated between the first welding wire 11 and the workpiece 2. Between the 1st welding wire 11 and the workpiece | work 2, a short circuit period and an arc period are repeated alternately, and welding is performed. The first welding torch 41 is held by a robot (not shown). The workpiece 2 is installed on a jig 5.

  The plus terminal of the first welding power source PS1 and the first power supply tip 61 in the first welding torch 41 are connected via a cable. Further, the negative terminal of the first welding power source PS1 and the jig 5 are connected via a cable. The first welding voltage Vw1 is a voltage applied between the first power supply tip 61 and the surface of the workpiece 2. Although it is easy to connect the voltage detection line to the first power supply chip 61, it is difficult to connect the voltage detection line to the surface of the work 2. For this purpose, the first welding voltage detection circuit VD1 detects the voltage between the first power feed tip 61 and the jig 5 and outputs the first welding voltage detection signal Vd1. The first welding voltage detection signal Vd1 is input to the first welding power source PS1. The first welding voltage detection signal Vd1 is used to detect the constriction formed on the droplet of the first welding wire 11.

  The second welding power source PS2 outputs the second welding voltage Vw2 and the second welding current Iw2, and outputs the second feeding control signal Fc2 to the second feeder FD2. The second feeder FD2 feeds the second welding wire 12 through the second welding torch 42 by using the second feeding control signal Fc2 as an input. A second arc 32 is generated between the second welding wire 12 and the workpiece 2. Between the 2nd welding wire 12 and the workpiece | work 2, a short circuit period and an arc period are repeated alternately, and welding is performed. The second welding torch 42 is held by a robot (not shown).

  The plus terminal of the second welding power source PS2 and the second power feed tip 62 in the second welding torch 42 are connected via a cable. The minus terminal of the second welding power source PS2 and the jig 5 are connected via a cable. The second welding voltage Vw2 is a voltage applied between the second power feed tip 62 and the surface of the workpiece 2. Although it is easy to connect the voltage detection line to the second power feed chip 62, it is difficult to connect the voltage detection line to the surface of the work 2, and thus the connection is made to the jig 5. For this purpose, the second welding voltage detection circuit VD2 detects the voltage between the second power feed tip 62 and the jig 5, and outputs a second welding voltage detection signal Vd2. The second welding voltage detection signal Vd2 is input to the second welding power source PS2. The constriction formed in the droplet of the second welding wire 12 is detected using the second welding voltage detection signal Vd2.

  The first welding current Iw1 is energized through the plus terminal of the first welding power source PS1, the first feeding tip 61, the first welding wire 11, the workpiece 2, the jig 5, and the minus terminal path of the first welding power source PS1. The second welding current Iw2 is energized through the plus terminal of the second welding power source PS2, the second feed tip 62, the second welding wire 12, the workpiece 2, the jig 5, and the minus terminal path of the second welding power source PS2. Accordingly, the first welding current Iw1 and the second welding current Iw2 are passed through the workpiece 2 and the jig 5. The current obtained by adding the first welding current Iw1 and the second welding current Iw2 is hereinafter referred to as a combined welding current Ig. And the workpiece | work 2 and the jig | tool 5 which this total welding current Ig supplies will be called a common energization path. This common energization path has a resistance value and an inductance value L (μH). In general, the resistance value is small and can be ignored. For this reason, the common energization path has only the inductance value L.

Said 1st welding voltage detection signal Vd1 and 2nd welding voltage detection signal Vd2 can be represented like the following Formula.
Vd1 = Vw1 + L · dIg / dt (11) Formula Vd2 = Vw2 + L · dIg / dt (12) Therefore, the first welding voltage detection signal Vd1 is common to the first welding voltage Vw1 due to the change of the total welding current Ig. The voltage generated on the inductance value L of the electric circuit is a superimposed value. The same applies to the second welding voltage detection signal Vd2.

  FIG. 8 is a waveform diagram when the squeezing detection control operates normally in the welding apparatus of FIG. (A) shows the waveform of the first welding current Iw1, FIG. (B) shows the waveform of the first welding voltage detection signal Vd1, and (C) shows the waveform of the second welding current Iw2. FIG. 4D shows the waveform of the second welding voltage detection signal Vd2. The figure shows a case where the times t1 to t3 when the first welding wire 11 and the work 2 are in a short circuit period and the times t5 and t6 where the second welding wire 12 and the work 2 are in a short circuit period do not overlap. . Hereinafter, a description will be given with reference to FIG.

  During the period from time t1 to t3 in which the first welding wire 11 and the work 2 are short-circuited, the arc period is between the second welding wire 12 and the work 2. For this reason, as shown in FIG. 3C, the second welding current Iw2 is during the arc period, and since there is no sudden change in the arc length due to disturbance, the current change rate is slower than during the short circuit period. is there.

(1) Operation from occurrence of short circuit of first welding wire 11 at time t1 to detection of necking at time t2 When the first welding wire 11 comes into contact with the workpiece 2 at time t1, a short circuit period occurs, as shown in FIG. As described above, the first welding voltage detection signal Vd1 rapidly decreases to a short-circuit voltage value of about several volts. As shown in FIG. 5A, the first welding current Iw1 decreases from the welding current during the arc period at time t1, and becomes a predetermined initial current value during a predetermined initial period from time t1 to t11. During the period from t11 to t12, it rises with a predetermined slope at the time of short circuit, and during the period from time t12 to t2, has a predetermined peak value. As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises from around time t12 when the first welding current Iw1 reaches its peak value. This is because a constriction is gradually formed in the droplet. The period from time t12 is a period for detecting the constriction. In the period for detecting the constriction, as shown in FIG. 4A, the first welding current Iw1 has a peak value and a substantially constant value. Further, as shown in FIG. 5C, the second welding current Iw2 is not changing rapidly because it is during the arc period and there is no sudden change in the arc length due to disturbance. As a result, in the above-described equation (11), L · dIg / dt becomes a small value and can be ignored. Therefore, since Vd1 = Vw1, the constriction of the droplet can be normally detected without malfunction. The initial period is set to about 1 ms, the initial current value is set to about 50 A, the short-circuit slope is set to about 100 to 300 A / ms, and the peak value is set to about 300 to 400 A. Is done.

(2) Operation from the time when the necking is detected at time t2 to the time when the arc is regenerated at time t3 At time t2, as shown in FIG. The constriction is detected when the voltage increase value ΔV from the value becomes equal to a predetermined constriction detection reference value Vtn. When the constriction is detected, the first welding current Iw1 rapidly decreases from the peak value to the predetermined low level current value Il as shown in FIG. 5A, and the value is maintained until the arc is regenerated at time t3. . This rapid current deceleration is an extremely fast value of about 3000 A / ms. As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises rapidly after once decreasing from time t2 because the first welding current Iw1 becomes the low level current value Il. The low level current value Il is set to about 30A.

(3) Operation from time of arc reoccurrence at time t3 to end of delay period Td at time t4 When the first arc 31 reappears at time t3, as shown in FIG. The value of the signal Vd1 is equal to or greater than the short circuit / arc discrimination value Vta. As shown in FIG. 6A, the first welding current Iw1 rises at a predetermined arc slope from time t3, and when it reaches a predetermined high level current value, the value is maintained until time t4. As shown in FIG. 5B, the first welding voltage detection signal Vd1 is in a high level voltage value during a predetermined delay period Td from time t3 to t4. This delay period Td is set to about 2 ms.

(4) Arc period operation from the end of the delay period Td at time t4 to the next short-circuit occurrence at time t5 At time t4, as shown in FIG. 4A, the first welding current Iw1 is determined from the high level current value. It gradually decreases. Similarly, as shown in FIG. 5B, the first welding voltage detection signal Vd1 gradually decreases from the high level voltage value.

(5) Operation from occurrence of short circuit of second welding wire 12 at time t5 to reoccurrence of arc at time t6 Second welding current Iw2 shown in FIG. 5C and second welding voltage detection signal shown in FIG. Since the waveform of Vd2 is the same as the waveforms of (1) and (2) above, description thereof is omitted.

  As described above, when the mutual short-circuit periods do not overlap and there is no sudden change in the arc length due to disturbance, the rate of change in the welding current during the arc period is small. Since the generated voltage value is small, the constriction can be accurately detected.

  FIG. 9 is a waveform diagram when the squeezing detection control malfunctions in the welding apparatus of FIG. (A) shows the waveform of the first welding current Iw1, FIG. (B) shows the waveform of the first welding voltage detection signal Vd1, and (C) shows the waveform of the second welding current Iw2. FIG. 4D shows the waveform of the second welding voltage detection signal Vd2. In the same figure as FIG. 8 mentioned above, the time t1-t3 when the 1st welding wire 11 and the workpiece | work 2 are a short circuit period, and the time t5-t6 when the 2nd welding wire 12 and the workpiece | work 2 are a short circuit period. This is a case where and do not overlap. Hereinafter, a description will be given with reference to FIG.

  During the period from time t1 to t3 in which the first welding wire 11 and the work 2 are short-circuited, the arc period is between the second welding wire 12 and the work 2. In the figure, the second welding current Iw2 changes suddenly because the arc length suddenly changes due to disturbance during the arc period of the second welding wire 12 at times t1 to t3. In this state, the squeezing detection control is malfunctioning, although the reason will be described later. This figure corresponds to FIG. 8 described above, and the description of the same operation will not be repeated. Examples of the disturbance include sudden ejection of gas from the molten pool, irregular movement of the molten pool, fluctuations in the feeding speed, fluctuations in the distance between the power supply tip and the workpiece, and changes in the welding posture.

  When the first welding wire 11 comes into contact with the workpiece 2 at time t1, a short-circuit period occurs, and the first welding voltage detection signal Vd1 rapidly decreases to a short-circuit voltage value of about several volts as shown in FIG. As shown in FIG. 5A, the first welding current Iw1 decreases from the welding current during the arc period at time t1, becomes an initial current value during the initial period from time t1 to t11, and during the period from time t11 to t12. Rises with a slope at the time of a short circuit, and reaches a peak value during the period from time t12. As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises from around time t12 when the first welding current Iw1 reaches its peak value. This is because a constriction is gradually formed in the droplet. The period from time t12 is a period for detecting the constriction. Since the arc length of the second arc 31 suddenly increases due to disturbance at time t13 during the period for detecting this constriction, the second welding current Iw2 rapidly decreases as shown in FIG. As shown in FIG. (D), the second welding voltage detection signal Vd2 rises rapidly. Since the arc length returns to the original at time t41, the second welding current Iw2 rises and returns to the original as shown in FIG. 10C, and the second welding voltage is detected as shown in FIG. The signal Vd2 decreases and returns.

  In the period for detecting the constriction from time t12, as shown in FIG. 5A, the first welding current Iw1 is a peak value and a substantially constant value. However, as shown in FIG. 5C, the second welding current Iw2 is rapidly decreased because the arc length is abruptly increased at time t13 as described above. As a result, in the above equation (11), for L · dIg / dt = dIw1 / dt + dIw2 / dt, dIw1 / dt is a small value and dIw2 / dt is a negative large value. For this reason, as shown in FIG. 5B, the first welding voltage detection signal Vd1 gradually increases from time t12 with the formation of the constriction, and the time t13 before the increase reaches the constriction detection reference value Vtn. , The second welding current Iw2 decreases suddenly, and the constriction detection fails.

  At time t13, as shown in FIG. 5B, the first welding voltage detection signal Vd1 decreases and does not reach the squeezing detection reference value Vtn. Therefore, as shown in FIG. 5A, the first welding current Iw1 Maintains the peak value until the first arc 31 at time t3 is regenerated.

  When the first arc 31 is regenerated at time t3, the value of the first welding voltage detection signal Vd1 becomes equal to or greater than the short circuit / arc discrimination value Vta, as shown in FIG. As shown in FIG. 5A, the first welding current Iw1 changes from the peak value at time t3 to the high level current value, and maintains that value until time t4. As shown in FIG. 5B, the first welding voltage detection signal Vd1 is in a high level voltage value during the delay period Td from time t3 to time t4.

  As described above, if the welding current from another welding power source suddenly changes during the period of detecting the constriction, the voltage value generated by the inductance value L of the common energization path becomes large, so that the possibility of erroneously detecting the constriction increases. . In the figure, in the period for detecting the constriction of the first welding wire 11, the misdetection of the constriction caused by the arc length being increased due to the disturbance and the second welding current Iw2 being rapidly reduced has been described. However, the arc length is shortened by the disturbance. Therefore, erroneous detection may occur even when the second welding current Iw2 increases rapidly. Furthermore, there is a possibility that erroneous detection may occur due to increase / decrease of the second welding current Iw2 during the short circuit period.

  In the invention of Patent Document 2, when the second welding current Iw2 of the second welding power source PS2 is changing suddenly, the detection of the constriction of the first welding power source PS1 is prohibited. Thereby, the false detection of the constriction by the sudden change of the 2nd welding current Iw2 can be prevented. However, since the situation in which the second welding current Iw2 changes suddenly occurs frequently during welding, this method has a problem that the constriction detection control is frequently prohibited and the effect of reducing the amount of spatter generation is reduced.

JP 2006-281219 A Japanese Patent No. 4815966

  Therefore, in the present invention, the first and second welding power sources each generate an arc on the common workpiece and weld it, and the first welding power source has a constriction detection control function, and the second welding current during the arc period. It is an object of the present invention to provide a welding current control method for a welding apparatus that can operate normally without malfunction of the squeezing detection control of the first welding power source even if the temperature changes suddenly.

In order to solve the above-described problems, the invention of claim 1
While feeding a 1st welding wire from a 1st welding power supply, energizing a 1st welding current and generating a 1st arc to a common work, and feeding a 2nd welding wire from a 2nd welding power supply A welding device for energizing a second welding current to generate a second arc on the common workpiece and welding,
In the welding current control method of the welding apparatus, when the first welding power source detects the constriction of the droplets, the first welding current to be supplied to the short-circuit load is reduced to regenerate the first arc.
When the first welding current is energized, the maximum rate of change during the arc period of the second welding current is smaller than when not energized,
This is a welding current control method for a welding apparatus.

The invention of claim 2 reduces the maximum rate of change only when the first arc is in a short circuit period.
The welding current control method for a welding apparatus according to claim 1.

Invention of Claim 3 makes the said maximum change rate in the whole period of the said welding part small, when the said 1st welding current has energized the partial period of the welding part of the said common workpiece | work,
The welding current control method for a welding apparatus according to claim 1.

  According to the present invention, the first and second welding power sources respectively generate arcs on the common workpiece and weld them, and the first welding power source has a constriction detection control function, and the second welding current during the arc period. Since the maximum change rate is controlled to be small even if the change suddenly changes, the squeezing detection control of the first welding power source can operate normally without malfunctioning.

It is a block diagram of the welding apparatus for welding two welding locations of one workpiece | work simultaneously using two welding power supplies which concern on Embodiment 1 of this invention. It is a detailed block diagram of 1st welding power supply PS1 which comprises the welding apparatus of FIG. It is a timing chart of each signal in 1st welding power supply PS1 of FIG. It is a block diagram of the welding apparatus for welding two welding locations of one workpiece | work simultaneously using two welding power supplies which concern on Embodiment 2 of this invention. It is a detailed block diagram of 1st welding power supply PS1 which comprises the welding apparatus of FIG. It is a timing chart of each signal in 1st welding power supply PS1 of FIG. In prior art, it is a block diagram of the welding apparatus for welding two welding locations of one workpiece | work simultaneously using two welding power supplies. FIG. 8 is a waveform diagram when the squeezing detection control operates normally in the welding apparatus of FIG. 7. FIG. 8 is a waveform diagram when the squeezing detection control malfunctions in the welding apparatus of FIG. 7.

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

[Embodiment 1]
FIG. 1 is a configuration diagram of a welding apparatus for simultaneously welding two welding locations of one workpiece using two welding power sources according to Embodiment 1 of the present invention. The two welding power sources both provide a constriction detection control function. This figure corresponds to FIG. 7 described above, and the same components are denoted by the same reference numerals, and description thereof will not be repeated. This figure is obtained by adding a combined welding current detection circuit IGD to FIG. Hereinafter, the added component will be described with reference to FIG.

  The total welding current detection circuit IGD detects the total welding current Ig energized in the common current path, and outputs a total welding current detection signal Igd to the first welding power source PS1 and the second welding power source PS2.

  FIG. 2 is a detailed block diagram of the first welding power source PS1 constituting the welding apparatus of FIG. The same applies to the block diagram of the second welding power source PS2. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V as input and performs output control such as inverter control in accordance with an error amplification signal Ea described later to obtain the first welding voltage Vw1 and the first welding current Iw1. Output. This power supply main circuit PM is omitted in the drawing, but a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current to high frequency alternating current, and high frequency alternating current for welding A high-frequency transformer that steps down to a suitable voltage value, a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current, a reactor that smoothes the rectified direct current, a modulation circuit that performs pulse width modulation control using the error amplification signal Ea as an input, An inverter drive circuit that drives the switching element of the inverter circuit using the pulse width modulation control signal as an input is provided.

  The current reducing resistor R is inserted between the power supply main circuit PM and the first welding torch 41. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (about 0.01 to 0.03Ω). For this reason, when the current reducing resistor R is inserted into the energization path by the constriction detection control, the energy accumulated in the DC reactor in the welding power source and the reactor of the external cable is suddenly discharged. The transistor TR is connected in parallel with the current reducing resistor R and is controlled to be turned on or off in accordance with a drive signal Dr described later.

  The first welding wire 11 is fed through the first welding torch 41 by the first feeder FD <b> 1, and a first arc 31 is generated between the first welding wire 11 and the workpiece 2. The workpiece 2 is installed on a jig 5. A first welding voltage Vw1 is applied between a first power feed tip (not shown) in the first welding torch 41 and the surface of the work 2, and a first welding current Iw1 is conducted. Then, the combined welding current Ig passes through the common energization path such as the workpiece 2 and the jig 5.

  The first welding current detection circuit ID1 detects the first welding current Iw1 and outputs a first welding current detection signal Id1. As described above with reference to FIG. 1, the total welding current detection circuit IGD provided outside detects the above total welding current Ig and outputs the total welding current detection signal Igd. As described above with reference to FIG. 1, the first welding voltage detection circuit VD <b> 1 provided outside detects the voltage between the first power feed tip in the first welding torch 41 and the jig 5 to perform the first welding. The voltage detection signal Vd1 is output. The first welding voltage detection circuit VD1 may be provided inside.

  The short circuit determination circuit SD receives the first welding voltage detection signal Vd1 as described above, and when this value is less than a predetermined short circuit / arc determination value, it determines that it is in the short circuit period and becomes High level. Outputs a short-circuit determination signal Sd which is determined to be in the arc period and becomes Low level.

  The current energization determination circuit CD receives the above-mentioned total welding current detection signal Igd and the above-mentioned first welding current detection signal Id1, and subtracts Igd−Id1. When this subtraction value is equal to or higher than the threshold value, High. A current energization determination signal Cd that becomes a level is output. The threshold is set to about 10A. Igd-Id1 corresponds to the value of the welding current from the other welding power source when viewed from the first welding power source PS1. Therefore, when the current energization determination signal Cd is at a high level, the welding current from another welding power source is energized, and when it is at a low level, it is not energized. In the figure, the welding current from another welding power source is the second welding current Iw2.

  The squeezing detection reference value setting circuit VTN outputs a squeezing detection reference value signal Vtn. The value of the squeezing detection reference value signal Vtn is set to an appropriate value according to the welding conditions such as the welding method, the feeding speed, the material of the first welding wire 11 and the diameter. The constriction detection circuit ND receives the constriction detection reference value signal Vtn, the short circuit determination signal Sd, the first welding voltage detection signal Vd1 and the first welding current detection signal Id1, and the short circuit determination signal Sd is High. When the voltage increase value of the first welding voltage detection signal Vd1 at the level (short-circuit period) reaches the value of the squeezing detection reference value signal Vtn, it is determined that the squeezing has been formed and becomes the High level, and the short-circuit determination signal Sd. When the signal changes to the low level (arc period), the squeezing detection signal Nd which becomes the low level is output. Further, the squeezing detection signal Nd may be changed to a high level when the differential value of the first welding voltage detection signal Vd1 during the short circuit period reaches the value of the squeezing detection reference value signal Vtn corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the first welding voltage detection signal Vd1 by the value of the first welding current detection signal Id1, and the differential value of this resistance value corresponds to the squeezing detection reference value signal Vtn. The squeezing detection signal Nd may be changed to a high level when reaching the value of.

  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 first welding current detection signal Id1 as an input, and becomes a high level when Id1 <Ilr and becomes a low level when Id1 ≧ Ilr. The signal Cm is output. The drive circuit DR receives the current comparison signal Cm and the above-described squeezing detection signal Nd, changes to a low level when the squeezing 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. The drive signal Dr that changes in level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. Therefore, the first welding current Iw1 energizing the short-circuit load is Decrease rapidly. Then, when the value of the first welding current Iw1 that suddenly decreases 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. To return 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 squeezing detection signal Nd as input, and outputs the current control setting signal Icr.
1) A predetermined initial current set value is output as the current control setting signal Icr during a predetermined initial period from the time when the short circuit determination signal Sd changes to the high level (short circuit).
2) Thereafter, the value of the current control setting signal Icr is increased from the initial current setting value to a predetermined peak setting value at a predetermined short-circuit slope, and the value is maintained.
3) When the squeezing detection signal Nd changes to the high level (squeezing detection), the value of the current control setting signal Icr is switched to the value of the low level current setting signal Ilr and maintained.
4) When the short circuit determination signal Sd changes to the low level (arc), the current control setting signal Icr is raised to a predetermined high level current setting value with a predetermined arc inclination, and the value is maintained.

  The off-delay circuit TDS receives the short-circuit determination signal Sd as described above, and outputs a delay signal Tds by delaying off the time when this signal changes from the high level to the low level by a predetermined delay time. Accordingly, the delay signal Tds is a signal that becomes a high level during the short circuit period, and is turned off to a low level after being delayed for a delay time after the arc is regenerated.

  The current error amplification circuit EI amplifies an error between the current control setting signal Icr (+) and the first welding current detection signal Id1 (−), and outputs a current error amplification signal Ei.

  The gain setting circuit GR receives the above-described current energization determination signal Cd, and when the current energization determination signal Cd is at a high level (when a welding current from another welding power source is energized), a low gain setting determined in advance. When the value is low and the welding current from another welding power source is not energized, a gain setting signal Gr that is a predetermined high gain setting value is output. Naturally, the low gain setting value> the high gain setting value. The gain (amplification factor, gain) of the constant voltage feedback control (arc length control) system during the arc period in the first arc 31 is set by the gain setting signal Gr. The high gain setting value is set by experiment so that the transient response and steady stability of the arc length control system are good. The low gain set value is set such that the maximum rate of change when the first welding current Iw1 during the arc period changes due to a disturbance is limited to a value that does not cause squeezing detection control in another welding power source to malfunction. For example, the maximum rate of change of the first welding current Iw1 during the arc period is about 1000 A / ms when the gain is high, and 200 to 500 A when the gain is low. / ms or so. When the gain is set to a low value, the transient response of the arc length control system is slightly delayed, but the welding quality is not greatly affected.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage during the arc period. The voltage error amplifying circuit EV receives the voltage setting signal Vr, the first welding voltage detection signal Vd1 and the gain setting signal Gr, and receives the voltage setting signal Vr (+) and the first welding voltage detection signal Vd1 (− ) Is amplified by a gain determined by the gain setting signal Gr, and a voltage error amplified signal Ev is output.

  The control switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev and the delay signal Tds as inputs, and the delay signal Tds is at a high level (the arc is regenerated from the start of the short circuit and the delay time is increased). The current error amplification signal Ei is output as the error amplification signal Ea during the period until the time elapses, and the voltage error amplification signal Ev is output as the error amplification signal Ea when at the low level (arc). With this circuit, constant current control is performed during the short circuit period + delay period, and constant voltage control is performed during the other arc periods.

  The feeding speed setting circuit FR outputs a predetermined feeding speed setting signal Fr. The first feed control circuit FC1 receives the feed speed setting signal Fr as an input, and supplies the first feed control signal Fc1 for feeding the first welding wire 11 at a feed speed corresponding to the set value. To the first feeder FD1.

  FIG. 3 is a timing chart of each signal in the first welding power source PS1 of FIG. FIG. 4A shows the time change of the first welding current Iw1, FIG. 3B shows the time change of the first welding voltage detection signal Vd1, and FIG. 4C shows the time change of the necking detection signal Nd. (D) shows the time change of the drive signal Dr, (E) shows the time change of the delay signal Tds, (F) shows the time change of the current control setting signal Icr, Fig. (G) shows the time change of the second welding current Iw2, and Fig. (H) shows the time change of the gain setting signal Gr of the first welding power source PS1. This figure corresponds to FIG. 9 described above, and shows a case where the second welding current Iw2 suddenly changes due to a disturbance during the short-circuit period of the first welding wire 11. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5G, the second welding current Iw2 is energized during the entire period shown in FIG. 5G. Therefore, as shown in FIG. 5H, the gain of the arc length control system of the first welding power source PS1 is obtained. The value of the setting signal Gr remains the low gain setting value. For this reason, the maximum rate of change of the first welding current Iw1 during the arc period is smaller than when the second welding current Iw2 is not energized. Similarly, the maximum change rate of the second welding current Iw2 during the arc period (hereinafter, this control is referred to as current change rate limiting control) is also small.

(1) Operation from the occurrence of a short circuit at time t1 until the necking detection time at time t2 When the first welding wire 11 comes into contact with the workpiece 2 at time t1, a short circuit period occurs, and as shown in FIG. The voltage detection signal Vd1 rapidly decreases to a short circuit voltage value of about several volts. It is determined that the first welding voltage detection signal Vd1 is less than the short circuit / arc determination value Vta, and the delay signal Tds changes from the Low level to the High level as shown in FIG. In response to this, as shown in FIG. 5F, the current control setting signal Icr changes from a predetermined high level current setting value to a predetermined initial current setting value which is a small value at time t1. During the predetermined initial period from the time t1 to t11, the initial current set value is set. During the period from the time t11 to t12, the voltage rises with a predetermined slope at the time of short circuit, and during the period from the time t12 to t2, the predetermined peak is set. Set value. Since the constant current control is performed as described above during the short-circuit period, the first welding current Iw1 is controlled to a value corresponding to the current control setting signal Icr. For this reason, as shown in FIG. 5A, the first welding current Iw1 rapidly decreases from the welding current in the arc period at time t1, and becomes the initial current value during the initial period from time t1 to t11. During the period of t12, it rises with the inclination at the time of a short circuit, and becomes a peak value during the period of time t12-t2. As shown in FIG. 6C, the squeezing detection signal Nd is at a high level during a period from time t2 to t3, which will be described later, and is at a low level during other periods. As shown in FIG. 4D, the drive signal Dr is at a low level during a period from time t2 to t21, which will be described later, and is at a high level during other periods. Therefore, during the period before time t2 in the figure, the drive signal Dr is at a high level and the transistor TR in FIG. 2 is turned on, so that the current reducing resistor R is short-circuited and the normal consumable electrode arc welding power source is connected. It becomes the same state.

  As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises from around time t12 when the first welding current Iw1 reaches its peak value. This is because a constriction is gradually formed in the droplet. The period from time t12 is a period for detecting the constriction. In the period in which this constriction is detected, the first welding current Iw1 is a peak value and a substantially constant value as shown in FIG. On the other hand, since the arc length of the second arc 32 suddenly increased due to the disturbance at time t13 in the period for detecting this constriction, the second welding current Iw2 is shown in FIG. It decreases more slowly than in the case of C). Since the arc length of the second arc 32 returns to the original at time t41, the second welding current Iw2 increases more slowly than in the case of FIG. 9C, as shown in FIG. Return. The reason why the rate of change of the second welding current Iw2 becomes gradual is as follows. That is, since the first welding current Iw1 is energized, the gain setting signal Gr in the second welding power source PS2 becomes a low gain setting value, so that the maximum rate of change of the second welding current Iw2 during the arc period is small. It is because it is limited to become.

  As a result, in the above equation (11), for L · dIg / dt = dIw1 / dt + dIw2 / dt, dIw1 / dt is a small value, and dIw2 / dt is also smaller than that in FIG. . For this reason, as shown in FIG. 5B, the first welding voltage detection signal Vd1 gradually rises from time t12 as the constriction is formed, and continues to rise at time t13.

(2) Operation from the time when the necking is detected at time t2 to the time when the arc is regenerated at time t3 At time t2, as shown in FIG. When the necking is detected when the voltage rise value ΔV from the value becomes equal to the predetermined squeezing detection reference value Vtn, the squeezing detection signal Nd changes to the high level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr becomes a low level, so that the transistor TR in FIG. 2 is turned off, and the current reducing resistor R is inserted into the energization path. At the same time, the current control setting signal Icr decreases to the value of the low level current setting signal Ilr, as shown in FIG. For this reason, as shown in FIG. 5A, the first welding current Iw1 rapidly decreases from the peak value to the low level current value Il. When the first welding current Iw1 decreases to the low level current value Il at time t21, as shown in FIG. 4D, the drive signal Dr returns to the high level, so that the transistor TR in FIG. The current resistor R is short-circuited. As shown in FIG. 9A, the first welding current Iw1 is maintained at the low level current value Il until the arc is regenerated at time t3 because the current control setting signal Icr remains the low level current setting signal Ilr. To do. Therefore, the transistor TR is turned off only during a period from when the constriction is detected at time t2 until the first welding current Iw1 decreases to the low level current value Il at time t21. As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises rapidly after once decreasing from time t2 because the first welding current Iw1 becomes small.

(3) Operation from time of arc reoccurrence at time t3 to end of delay period Td at time t4 When the first arc 31 reappears at time t3, as shown in FIG. The value of the signal Vd1 is equal to or greater than the short circuit / arc discrimination value Vta. In response to this, as shown in FIG. 5F, the value of the current control setting signal Icr rises from the value of the low level current setting signal Ilr at a predetermined arc slope, and the above described high level current setting When the value is reached, the value is maintained. As shown in FIG. 5E, the delay signal Tds remains at the high level until time t4 when a predetermined delay period Td elapses after the arc is regenerated at time t3. Therefore, since the welding power source is controlled at a constant current until time t4, as shown in FIG. 4A, when the first welding current Iw1 rises at an arc inclination from time t3 and reaches a high level current value. The value is maintained until time t4. As shown in FIG. 5B, the first welding voltage detection signal Vd1 is in a high level voltage value during the delay period Td from time t3 to time t4. As shown in FIG. 5C, the squeezing detection signal Nd changes to the low level because the arc is regenerated at time t3.

(4) Operation in the arc period from the end of the delay period Td at time t4 until the next short-circuit occurrence at time t5 As shown in FIG. As a result, the welding power source is switched from constant current control to constant voltage control. For this reason, as shown in FIG. 5A, the first welding current Iw1 gradually decreases from the high level current value. Similarly, as shown in FIG. 5B, the first welding voltage detection signal Vd1 gradually decreases from the high level voltage value. During the period from time t42 to t43 during the arc period, the arc length of the first arc 31 is shortened due to the disturbance, so that the first welding current Iw1 is an increased value as shown in FIG. As shown in FIG. 5B, the first welding voltage detection signal Vd1 has a decreased value. The rate of change of rising and falling of the first welding current Iw1 at this time is more gradual than when the second welding current Iw2 is not energized. The reason is that, since the second welding current Iw2 is energized as shown in FIG. 5G, the gain setting signal Gr becomes a low gain setting value as shown in FIG. This is because the maximum change rate of the first welding current Iw1 during the period is limited to be small.

  As described above, in the squeezing detection control, when squeezing is detected at time t2, the first welding current Iw1 is suddenly reduced by inserting a current reducing resistor in the energizing path, and the first arc 31 is regenerated at time t3. The current value at can be controlled to a small value. For this reason, the amount of spatter generated can be greatly reduced.

  In the first embodiment described above, whether or not a welding current from another welding power source is energized is determined by detecting the total welding current Ig. In robot welding, the current energization determination signal Cd may be generated from a work program. That is, in a welding section in which a welding current from another welding power source is energized, a high-level current energization determination signal Cd is input from the robot controller to the first welding power source PS1 by the work program, A low level current energization determination signal Cd is input to a welding section in which no welding current is applied. Further, when a welding current from another welding power source is energized in a part of the welded part of the work, the gain of the arc length control system in the whole part of the welded part may be reduced. This is because there are cases where the welding state is more stable when the gain of the entire section is made smaller than when the section where the gain of the arc length control system is large and the section where the gain is small in the welding section.

  In the first embodiment described above, the gain of the voltage error amplification circuit EV of the constant voltage feedback control system is reduced in order to reduce the maximum rate of change of the welding current during the arc period. (Current change rate limiting control) As another method, the welding current change rate is detected, and when the change rate detection signal exceeds the reference value, the output control of the welding power source is temporarily forced. You may make it stop.

  In FIG. 1 described above, both the first welding power source PS1 and the second welding power source PS2 are provided with a constriction detection control function. Therefore, when both the welding power sources are energized with the other side welding current, It is necessary to provide control for reducing the maximum rate of change of the welding current during the arc period. When the first welding power source PS1 has a squeezing detection control function and the second welding power source PS2 does not have a squeezing detection control function, the second welding power source PS2 needs to have at least the current change rate limiting control described above. There is. On the other hand, when the second welding power source PS2 has a squeezing detection control function and the first welding power source PS1 does not have a squeezing detection control function, the first welding power source PS1 has at least the above-described current change rate limiting control. It is necessary to have. In Embodiment 1, the number of welding power sources is two, but the same applies to the case of three or more.

  Even if the welding current during the arc period of another welding power source changes suddenly by the above-described current change rate limiting control, it is possible to suppress the malfunction of the constriction detection control. However, the malfunction of the squeezing detection control due to a sudden change in the welding current during the short-circuit period of another welding power source cannot be suppressed. In this regard, as in the prior art, when another welding power source is in a short-circuit period, the necking detection control may be prohibited. The time ratio of the short circuit period to the welding period including the arc period and the short circuit period is at most 20%. Therefore, even if the squeezing detection control is prohibited when the other welding power source is in the short-circuit period, the effect on the reduction amount of spatter generation is small.

  According to the first embodiment described above, the maximum rate of change during the arc period of the second welding current is made smaller when the first welding current is energized than when it is not energized. As a result, in the present embodiment, the first and second welding power sources generate arcs on the common workpieces and weld them, and the first welding power source has a constriction detection control function. 2 Even if the welding current changes suddenly, the maximum change rate is controlled to be small, so that the squeezing detection control of the first welding power source can operate normally without malfunctioning.

[Embodiment 2]
In the first embodiment described above, the maximum change rate of the welding current during the arc period is reduced depending on whether or not the welding current from another welding power source is energized. On the other hand, in Embodiment 2, when the welding wire of another welding power source is in the short circuit period, the maximum rate of change of the welding current during the arc period is made smaller than when the welding wire is not in the short circuit period. .

  FIG. 4 is a configuration diagram of a welding apparatus for simultaneously welding two welding locations of one workpiece using two welding power sources according to Embodiment 2 of the present invention. The two welding power sources both provide a constriction detection control function. This figure corresponds to FIG. 1 described above, and the same components are denoted by the same reference numerals, and description thereof will not be repeated. This figure is obtained by deleting the total welding current detection circuit IGD of FIG. 1 and adding a first short circuit period notification signal Sm1 and a second short circuit period notification signal Sm2. Hereinafter, different parts will be described with reference to FIG.

  The first welding power source PS1 outputs a first short circuit period notification signal Sm1 to the second welding power source PS2. This first short-circuit period notification signal Sm1 is a signal that is at a high level when the first welding wire 11 and the workpiece 2 are in a short-circuit period, and is at a low level when it is in an arc period.

  The second welding power source PS2 outputs a second short circuit period notification signal Sm2 to the first welding power source PS1. The second short-circuit period notification signal Sm2 is a signal that is at a high level when the second welding wire 12 and the workpiece 2 are in a short-circuit period, and is at a low level when the arc is in an arc period.

  FIG. 5 is a detailed block diagram of the first welding power source PS1 constituting the welding apparatus of FIG. The same applies to the block diagram of the second welding power source PS2. This figure corresponds to FIG. 2 described above, and the same reference numerals are given to the same blocks, and the description thereof will not be repeated. In the figure, the total welding current detection circuit IGD and the current conduction determination circuit CD in FIG. 2 are deleted, a first short-circuit period notification circuit SM1 is added, and the gain setting circuit GR in FIG. 2 is replaced with a second gain setting circuit GR2. It is a thing. Hereinafter, different blocks will be described with reference to FIG.

  The first short circuit period notification circuit SM1 receives the short circuit determination signal Sd and outputs the value of the short circuit determination signal Sd as it is to the second welding power source PS2 as the first short circuit period notification signal Sm1.

  The second gain setting circuit GR2 receives the second short-circuit period notification signal Sm2 from the second welding power source PS2, and when this signal is at a high level (when the other welding power sources are in the short-circuit period), a predetermined low gain is set. When set to the low level (when the other welding power source is in the arc period), a gain setting signal Gr that is a predetermined high gain setting value is output. When the second short circuit period notification signal Sm2 is at a high level, it means that the second welding wire 12 of the second welding power source PS2, which is another welding power source, is in an energized state and is in a short circuit period. . Since the constriction detection control is performed when the second welding wire 12 of the second welding power source PS2 is in the short circuit period, the maximum rate of change during the arc period of the first welding current Iw1 from the first welding power source PS1 becomes small. I am doing so. Thus, in the second embodiment, unlike the first embodiment, when the second welding wire 12 of the second welding power source PS2 is energized and is in the arc period, the first welding power source PS1 The maximum change rate during the arc period of the first welding current Iw1 is not reduced. When the second welding wire 12 of the second welding power source PS2 is in the arc period, it is needless to say that the squeezing detection control is not performed, and therefore it is not necessary to reduce the maximum rate of change of the first welding current Iw1.

  FIG. 6 is a timing chart of each signal in the first welding power source PS1 of FIG. FIG. 4A shows the time change of the first welding current Iw1, FIG. 3B shows the time change of the first welding voltage detection signal Vd1, and FIG. 4C shows the time change of the necking detection signal Nd. (D) shows the time change of the drive signal Dr, (E) shows the time change of the delay signal Tds, (F) shows the time change of the current control setting signal Icr, Fig. (G) shows the time change of the second welding current Iw2, and Fig. (H) shows the time change of the gain setting signal Gr of the first welding power source PS1. This figure corresponds to FIG. 3 described above, and the description of the same operation will not be repeated. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5G, the second welding current Iw2 is energized during the entire period of FIG. 5 and the period from time t5 to time t6 is a short-circuit period. In addition, the value of the gain setting signal Gr of the arc length control system of the first welding power source PS1 is a low gain setting value only during the period from time t5 to t6, and is a high gain setting value during the other periods. Therefore, the maximum rate of change of the first welding current Iw1 shown in FIG. 4A is small during the period from time t5 to t6. Similarly, the maximum rate of change of the second welding current Iw2 shown in FIG. 5G is small because the first welding wire 11 is short-circuited during the period from time t1 to time t3.

  As shown in FIG. 5B, the first welding voltage detection signal Vd1 rises from around time t12 when the first welding current Iw1 reaches its peak value. This is because a constriction is gradually formed in the droplet. The period from time t12 is a period for detecting the constriction. In the period in which this constriction is detected, the first welding current Iw1 is a peak value and a substantially constant value as shown in FIG. On the other hand, since the arc length of the second arc 32 suddenly increased due to the disturbance at time t13 during the period for detecting this constriction, the second welding current Iw2 is shown in FIG. It decreases gradually as in the case of G). For this reason, malfunction of the constriction detection control can be prevented. Since the arc length of the second arc 32 returns to the original at time t41, the second welding current Iw2 increases more rapidly than in FIG. 3G, as shown in FIG. Return to the original. This is because the first welding wire 11 has shifted to the arc period instead of the short-circuit period at time t3.

  During the period from time t42 to t43 during the arc period, the arc length of the first arc 31 is shortened due to the disturbance, so that the first welding current Iw1 is an increased value as shown in FIG. As shown in FIG. 5B, the first welding voltage detection signal Vd1 has a decreased value. The rate of change in rising and falling of the first welding current Iw1 at this time becomes steeper than in the case of FIG. This is because during the period from time t42 to t43, the second welding wire 12 is not in the short-circuit period, so the value of the gain setting signal Gr is a high gain setting value as shown in FIG. It is.

  According to Embodiment 2 described above, the maximum rate of change of the second welding current during the arc period is reduced only when the first arc is in the short circuit period. Thereby, in addition to the effect of Embodiment 1, in Embodiment 2, there exist the following effects. That is, in Embodiment 2, the maximum rate of change during the arc period of its own welding current is reduced only during the short-circuit period in which the squeezing detection control in another welding power source operates. For this reason, since the maximum rate of change of the welding current during the arc period, which is not related to the prevention of malfunction of the squeezing detection control of other welding power sources, is not reduced, the transient response of the arc length control system is more than that of the first embodiment. Will be improved.

11 1st welding wire 12 2nd welding wire 2 work 31 1st arc 32 2nd arc 41 1st welding torch 42 2nd welding torch 5 jig 61 1st feeding tip 62 2nd feeding tip CD current conduction discrimination circuit Cd current Energization determination signal CM Current comparison circuit Cm Current comparison signal DR Drive circuit Dr Drive signal Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC1 First feed control circuit Fc1 First 1 feeding control signal Fc2 2nd feeding control signal FD1 1st feeding machine FD2 2nd feeding machine FR feeding speed setting circuit Fr feeding speed setting signal GR gain setting circuit Gr gain setting signal GR2 second gain setting circuit ICR current control setting circuit Icr current control setting signal ID1 first welding current detection circuit Id1 first welding current detection signal Ig combined welding current GD Total welding current detection circuit Igd Total welding current detection signal Il Low level current value ILR Low level current setting circuit Ilr Low level current setting signal Iw1 First welding current Iw2 Second welding current L Inductance value ND Constriction detection circuit Nd Constriction detection signal PM power main circuit PS1 first welding power source PS2 second welding power source R current reducing resistor SD short circuit determination circuit Sd short circuit determination signal SM1 first short circuit period notification circuit Sm1 first short circuit period notification signal Sm2 second short circuit period notification signal SW control Switch circuit Td Delay period TDS Off delay circuit Tds Delay signal TR Transistor VD1 First welding voltage detection circuit Vd1 First welding voltage detection signal VD2 Second welding voltage detection circuit Vd2 Second welding voltage detection signal VR Voltage setting circuit Vr Voltage setting signal Vta Arc discrimination value VTN Constriction detection reference value setting circuit Vtn Constriction detection reference value )
Vw1 1st welding voltage Vw2 2nd welding voltage ΔV Voltage rise value

Claims (3)

While feeding a 1st welding wire from a 1st welding power supply, energizing a 1st welding current and generating a 1st arc to a common work, and feeding a 2nd welding wire from a 2nd welding power supply A welding device for energizing a second welding current to generate a second arc on the common workpiece and welding,
In the welding current control method of the welding apparatus, when the first welding power source detects the constriction of the droplets, the first welding current to be supplied to the short-circuit load is reduced to regenerate the first arc.
When the first welding current is energized, the maximum rate of change during the arc period of the second welding current is smaller than when not energized,
A welding current control method for a welding apparatus. Only when the first arc is in a short circuit period, the maximum rate of change is reduced.
The welding current control method of the welding apparatus according to claim 1. When the first welding current is energized during a part of the welded part of the common workpiece, the maximum rate of change during the entire period of the welded part is reduced.
The welding current control method of the welding apparatus according to claim 1.

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