JP2008183588A - Pulsed arc welding control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform the excellent arc length control by removing the abnormal voltage on the welding voltage Vw for a long time in association with the deviation of a cathode point in the consumable electrode pulsed arc welding. <P>SOLUTION: In the pulsed arc welding control method, the welding voltage Vw of the pulse waveform is detected, the welding voltage limit value Vft is calculated by limiting the detected welding voltage value within the predetermined fluctuation range Vc±ΔVc from the reference voltage waveform of the pulse waveform; the reference voltage waveform is automatically updated to the voltage waveform generated by performing the moving average of the welding voltage limit value Vft; and the output of a welding power source is controlled so that the average value of the welding voltage limit value obtained by averaging the welding voltage limit value Vft is substantially equal to a predetermined voltage set value. The average value Vav of the welding voltage detected value Vw is calculated, the updating of the reference voltage waveform is interrupted when the raising rate Bv of the average value of the welding voltage reaches the reference raising rate Vt1, and the updating of the reference voltage waveform is re-started when the reducing rate Bv of the welding voltage average value reaches the reference reducing rate Bt2 thereafter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pulse arc welding control method for controlling an arc length by a welding voltage from which an abnormal voltage not proportional to the arc length is removed.

  FIG. 5 is a waveform diagram of a welding current Iw and a welding voltage Vw in consumable electrode pulse arc welding targeted by the present invention. Hereinafter, a description will be given with reference to FIG.

  During the peak rising period Tup from time t1 to t2, a transition current that rises from the base current Ib to the peak current Ip is energized as shown in FIG. 9A, and as shown in FIG. A transition voltage rising from the voltage Vb to the peak voltage Vp is applied between the electrode and the base material. During the peak period Tp from time t2 to t3, as shown in FIG. 6A, the peak current Ip having a large current value for transferring droplets is energized, and as shown in FIG. Vp is applied between the electrode and the base material. During the peak fall period Tdw from time t3 to t4, as shown in FIG. 6A, a transition current that falls from the peak current Ip to the base current Ib is applied, and as shown in FIG. A transition voltage that drops from the peak voltage Vp to the base voltage Vb is applied between the electrode and the base material. During the base period Tb from time t4 to t5, as shown in FIG. 6A, the base current Ib having a small current value for preventing the droplets from growing is energized, and as shown in FIG. A voltage Vb is applied between the electrode and the base material. Welding is performed repeatedly with the period of time t1 to t5 as the pulse period Tf. The peak rising period Tup and the peak falling period Tdw are as short as about 0.3 ms in the case of a reactor or the like existing inside and outside the welding power source. In this case, the welding current Iw and the welding voltage Vw are substantially rectangular waves. On the other hand, depending on the welding conditions, the peak rising period Tup and the peak falling period Tdw may be set to about several ms. In this case, the welding current Iw and the welding voltage Vw are trapezoidal waves.

  The welding current average value Iav is obtained by averaging the welding current Iw of the pulse waveform shown in FIG. 5A, and the welding voltage Vw is averaged by the welding voltage Vw of the pulse waveform as shown in FIG. The voltage average value Vav. Furthermore, as shown in FIG. 5B, the average value obtained by taking out only the peak voltage Vp in each cycle becomes the peak voltage average value Vpa, and the average value obtained by taking out only the base voltage Vb in each cycle is the base voltage average value Vba. It becomes.

  The arc length control of pulse arc welding is performed as follows. The arc length described below means the apparent arc length, and the apparent arc length is the distance to the base material directly under the welding wire. This apparent arc length is critically related to welding quality. Therefore, arc length control generally means apparent arc length control. Since the arc length (apparent arc length) and the welding voltage average value Vav are substantially proportional to each other, the arc length during welding can be detected by the welding voltage average value Vav. Then, at least one of the pulse period Tf, the peak period Tp, the peak current Ip, or the base current Ib is changed so that the detected value of the welding voltage average value Vav is substantially equal to the target voltage setting value Vs. By changing the welding current average value Iav, the wire melting rate is changed to control the arc length to an appropriate value. In the following description, a case where the pulse period Tf is changed by feedback control will be exemplified. Therefore, in this arc length control, it is a precondition for good arc length control that the arc length can be accurately detected by the welding voltage average value Vav.

By the way, in pulse arc welding, when the welding wire that is a consumable electrode and the base material are short-circuited and the short-circuit is released and the arc is re-ignited, the arc cathode spot caused by non-uniformity of the oxide film on the surface of the base material When a wobbling phenomenon occurs, an abnormal voltage may be superimposed on the welding voltage Vw. This abnormal voltage is generated due to various other causes.
Since this abnormal voltage is a voltage that is not proportional to the arc length, it is necessary to remove the abnormal voltage superimposed on the welding voltage Vw in order to detect the arc length. As a method for this removal, a reference voltage waveform Vc and a fluctuation range ΔVc of a pulse waveform are set in advance, and a portion where the welding voltage Vw falls outside the range of Vc ± ΔVc is cut and limited as an abnormal voltage. Technology has been proposed. Hereafter, this prior art is demonstrated (refer patent document 1, 2).

FIG. 6 is a diagram showing a method for setting the reference voltage waveform Vc. First, the reference peak voltage value Vpc, the reference base voltage value Vbc, and the fluctuation range ΔVc are set in advance by experiments or the like according to the type of welding wire, the feeding speed, and the like. Then, as shown in the figure, the reference voltage waveform Vc is defined by the following equation by the elapsed time t when the start time of the peak rising period Tup is 0 second.
0 ≦ t <Tup
Vc = ((Vpc−Vbc) / Tup) · t + Vbc (11) Expression Tup ≦ t <Tup + Tp
Vc = Vpc (12) Expression Tup + Tp ≦ t <Tup + Tp + Tdw
Vc = ((Vbc−Vpc) / Tdw) · (t−Tup−Tp) + Vpc (13) Expression Tup + Tp + Tdw ≦ t <Tup + Tp + Tdw + Tb
Vc = Vbc (14) Formula

For example, as shown in the figure, it is assumed that the welding voltage detection value at the elapsed time ta is Vd1. Since the elapsed time ta is when Tup + Tp ≦ ta <Tup + Tp + Tdw, the central voltage value Vc1 of the reference voltage waveform is substituted as follows by substituting into the above equation (13).
Vc1 = ((Vbc-Vpc) / Tdw). (Ta-Tup-Tp) + Vpc
Therefore, the welding voltage detection value Vd1 at the elapsed time ta is limited within the fluctuation range Vc1 ± ΔVc. That is, when Vd1 ≧ Vc1 + ΔVc, it is limited to Vd1 = Vc + ΔVc, and when Vd1 ≦ Vc1−ΔVc, it is limited to Vd1 = Vc−ΔVc. The welding voltage limit value Vft calculated in this way is a voltage value that is substantially proportional to the arc length from which the abnormal voltage is substantially eliminated.

  FIG. 7 is a voltage waveform diagram when an abnormal voltage is generated due to arc re-ignition immediately after the short circuit is released. FIG. 4A shows the time change of the welding voltage Vw, and FIG. 4B shows the time change of the welding voltage limit value Vft after the abnormal voltage is removed by the reference voltage waveform. As shown in FIG. 5B, the welding voltage Vw is limited within a fluctuation range Vc ± ΔVc having the reference voltage waveform as the center voltage value Vc. As a result, the welding voltage limit value Vft = Vc−ΔVc during the short-circuit period from time t1 to t2, and the welding voltage limit value Vft = Vc + ΔVc during the abnormal voltage generation period from time t2 to t3. Thus, the abnormal voltage can be substantially eliminated.

  FIG. 8 is a diagram showing a change over time in the welding voltage limit value Vft for explaining a method of automatically setting the reference voltage waveform Vc described above with reference to FIG. In the figure, the current time is time tn, which is the start time of the nth pulse cycle Tf (n). Further, the average value of the welding voltage limit value only during the peak period in the (n-1) th pulse cycle Tf (n-1) is the peak voltage limit value Vpf (n-1), and the welding voltage limit value only during the base period. Is the base voltage limit value Vbf (n-1). Similarly, the average value of the welding voltage limit value only during the peak period in the (n−m) th pulse cycle Tf (nm) is the peak voltage limit value Vpf (nm), and the average value of the welding voltage limit value only during the base period. Is the base voltage limit value Vbf (nm).

At time tn, the peak voltage moving average value Vpr (n) is calculated as shown in the following equation using the (n-1) to (nm) -th peak voltage limit value Vpf as an input.
Vpr (n) = (Vpf (n-1) +... + Vpf (nm)) / m Similar to the equation (21), at the time tn, the above (n-1) th to (nm) th base voltage limit Using the value Vbf as an input, the base voltage moving average value Vbr (n) is calculated as in the following equation.
Vbr (n) = (Vbf (n-1) +... + Vbf (nm)) / m (22)

In the equations (11) to (14), the peak voltage moving average value Vpr is substituted for the reference peak voltage value Vpc, and the base voltage moving average value Vbr is substituted for the reference base voltage value Vbc. Then, the reference voltage waveform during the nth pulse period Tf (n) is automatically set as shown in the following equation.
0 ≦ t <Tup
Vc (n) = ((Vpr (n) −Vbr (n)) / Tup) · t + Vbr (n) (31) Expression Tup ≦ t <Tup + Tp
Vc (n) = Vpr (n) (32) Expression Tup + Tp ≦ t <Tup + Tp + Tdw
Vc (n) = ((Vbr (n) −Vpr (n)) / Tdw) · (t−Tup−Tp) + Vpr (n) (33) Expression Tup + Tp + Tdw ≦ t <Tup + Tp + Tdw + Tb
Vc (n) = Vbr (n) (34)

  As described above, the peak voltage moving average value Vpr and the base voltage moving average value Vbr are calculated for each start point of the pulse period, and the reference voltage waveform is automatically set by the above equations (31) to (34). The In the above description, when the peak voltage moving average value Vpr is calculated, the peak voltage limit value Vpf may be calculated by weighted moving average. Similarly, when the base voltage moving average value Vbr is calculated, the base voltage limit value Vbf may be calculated by weighted moving average. Also, the length of the moving average period is set to the past several cycles to several tens of cycles.

JP 2003-31409 A JP 2006-68784 A

  As shown in FIG. 7, in pulsed MAG welding in which a steel material is welded using a mixed gas of an inert gas such as argon gas or helium and carbon dioxide, and an aluminum material is welded in 100% of an inert gas. In many cases, an abnormal voltage is superimposed on a part of the pulse period Tf or a period extending over about two cycles. For such an abnormal voltage, the abnormal voltage is substantially removed by the conventional abnormal voltage removing method. And good pulse arc welding can be performed.

  On the other hand, when steel materials such as stainless steel and Inconel are welded using 100% inert gas, the oxide film is extremely small on the surface of the base material, so it is easy to form where there is an oxide film. There may occur a phenomenon in which the cathode spot having the point is formed by moving instantaneously in search of an oxide film at a position far away from directly under the welding wire. Once the cathode spot is formed at a position far away from the cathode spot, the cathode spot becomes stable at that position, and a phenomenon occurs in which the cathode spot does not return directly below the welding wire for several hundred ms to several seconds. In such a state, the welding voltage Vw is not proportional to the arc length, which is the distance from the position immediately below the welding wire to the base metal, and becomes an abnormal voltage (hereinafter referred to as an abnormal voltage for a long period of time) in which the voltage has increased greatly. Hereinafter, the problems of the prior art when this abnormal voltage occurs for a long time will be described with reference to the drawings.

  FIG. 9 shows temporal changes in the welding voltage Vw and the welding voltage limit value Vft when the above-described abnormal voltage occurs for a long time. In the figure, during the period from time t1 to time t2, the cathode spot is suddenly formed at a position far away from directly below the wire for several hundred ms, and an abnormal voltage is generated for a long time. As shown in FIG. 5A, the welding voltage Vw of the pulse waveform has a waveform in which the voltage value is raised during the period of time t1 to t2. In the figure, the squares surrounded by diagonal lines schematically show the center voltage value Vc and the fluctuation range Vc ± ΔVc of the reference voltage waveform. The welding voltage Vw of each pulse period is limited within this fluctuation range Vc ± ΔVc, and a welding voltage limit value Vft shown in FIG. In the figure, for ease of explanation, the case where the pulse waveform is a rectangular wave is illustrated. The same applies to trapezoidal waves. Hereinafter, a description will be given with reference to FIG.

  During the pulse period Tf (1), as shown in FIG. 5A, the abnormal voltage is not superimposed on the welding voltage Vw and is within the fluctuation range Vc ± ΔVc from the reference voltage waveform. As shown in B), the welding voltage limit value Vft is equal to the welding voltage Vw. Since the above-described long-term abnormal voltage is generated in the pulse period Tf (2), the welding voltage Vw rises as a whole and has a waveform exceeding the upper limit value Vc + ΔVc of the fluctuation range as shown in FIG. It has become. For this reason, as shown in FIG. 5B, the welding voltage limit value Vft is limited to the upper limit value Vc + ΔVc of the fluctuation range. The center voltage value Vc of the reference voltage waveform at this time is substantially the same as that in the pulse period Tf (1).

  Also in the pulse period Tf (3), since abnormal voltage has been generated for a long time as shown in FIG. 3A, the welding voltage limit value Vft has a fluctuation range as shown in FIG. It is limited to the upper limit value Vc + ΔVc. Further, the center voltage value Vc of the reference voltage waveform in this cycle is calculated by the moving average value of the welding voltage limit value Vft in the past predetermined cycle, and thus becomes larger than the previous cycle. Similarly, also in the pulse period Tf (4), the welding voltage limit value Vft is larger than the previous period, and the center voltage value Vc of the reference voltage waveform is also increased. This state continues while the abnormal voltage is generated for a long time (between times t1 and t2).

  When this abnormal voltage is generated for a long period of time, the cathode spot has just moved away, and the arc length (apparent arc length) remains in an appropriate state. This is the same as the voltage waveform of the period Tf (1). However, as described above, since the welding voltage limit value Vft and the center voltage value Vc gradually increase, the welding voltage limit value Vft is an abnormal voltage when the abnormal voltage generation period continues for several hundreds of milliseconds to several seconds. It becomes the same as the raised welding voltage Vw. As a result, the average value Vfa of the welding voltage limit value, which is a feedback signal, gradually increases, so that the pulse period also gradually increases, the arc amount becomes shorter than the appropriate value, and the welding state becomes unstable.

  Therefore, the present invention provides a pulse arc welding control method capable of removing abnormal voltage and maintaining a stable welding state even if abnormal voltage occurs for a long period of time.

In order to solve the above-described problem, the first invention is to apply a welding current having a pulse waveform with a peak current and a base current as one cycle to the arc, and to weld a pulse waveform between the consumable electrode and the base material. The welding voltage limit value is calculated by limiting the welding voltage detection value within a predetermined fluctuation range from the reference voltage waveform of the pulse waveform, and the reference voltage waveform is generated by moving the welding voltage limit value. In a pulse arc welding control method for automatically updating the welding voltage waveform and controlling the output of the welding power source so that a welding voltage limit average value obtained by averaging the welding voltage limit values is substantially equal to a predetermined voltage setting value. ,
The average value of the welding voltage detection value is calculated, and when the increase rate of the welding voltage average value reaches the reference increase rate, the update of the reference voltage waveform is interrupted, and then the decrease rate of the welding voltage average value is The pulse arc welding control method is characterized in that the update of the reference voltage waveform is resumed when the reference reduction rate is reached.

  The second invention is the pulse arc welding control method according to the first invention, characterized in that the updating of the reference voltage waveform is equivalently performed by changing the fluctuation range to zero. is there.

  According to the first aspect of the invention, the updating of the center voltage value of the reference voltage waveform is interrupted during the period from when the increase rate of the welding voltage average value reaches the reference increase rate until the decrease rate reaches the reference decrease rate. By doing so, the abnormal voltage can be substantially removed for a long period of time. For this reason, even if an abnormal voltage occurs for a long time, the apparent arc length can be maintained at an appropriate value, and good welding quality can be obtained.

  According to the second aspect of the present invention, the fluctuation range of the reference voltage waveform is set to 0 during the period from when the increase rate of the welding voltage average value reaches the reference increase rate until the decrease rate reaches the reference decrease rate. Therefore, the abnormal voltage can be substantially removed for a long time. For this reason, even if an abnormal voltage occurs for a long time, the apparent arc length can be maintained at an appropriate value, and good welding quality can be obtained.

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

[Embodiment 1]
FIG. 1 is a voltage waveform diagram showing a pulse arc welding control method according to Embodiment 1 of the present invention. FIG. 4A shows the welding voltage Vw, FIG. 4B shows the differential value Bv of the welding voltage average value Vav, and FIG. 4C shows the welding voltage limit value Vft. This figure corresponds to FIG. 9 described above, and an abnormal voltage is generated for a long period of time from time t1 to time t2. As shown in FIG. 5A, numerals (1) to (7) described above each pulse waveform represent pulse period Tf (1) to pulse period Tf (7). In addition, the hatched squares shown in FIG. 5C indicate the fluctuation range Vc ± ΔVc from the center voltage value Vc of the reference voltage waveform. The figure shows the case where the pulse waveform is a rectangular wave, but the same applies to the case of a trapezoidal wave. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5A, the welding voltage average value Vav is a value obtained by moving average the welding voltage Vw. Further, the welding voltage average differential value Bv shown in FIG. 5B is a value obtained by differentiating the welding voltage average value Vav (Bv = G · dVav / dt, G is an amplification factor), and the welding voltage average value Vav increases. When it does, it becomes a positive value, and when it decreases, it becomes a negative value.

  In the pulse period Tf (1), as shown in FIG. 5A, no abnormal voltage is generated and the welding state is stable. As shown in FIG. Since the welding voltage Vw is within the fluctuation range Vc ± ΔVc from the center voltage value Vc of the reference voltage waveform, it becomes equal to the welding voltage Vw.

  In the pulse period Tf (2), as shown in FIG. 4A, an abnormal voltage is generated for a long period of time, resulting in a waveform in which the voltage is raised. The center voltage value Vc of the reference voltage waveform in this cycle is substantially the same as the previous cycle because the welding voltage limit value Vft up to the previous cycle is within the fluctuation range Vc ± ΔVc. Since the welding voltage Vw exceeds the fluctuation range upper limit value Vc + ΔVc, the welding voltage limit value Vft has a waveform limited to the fluctuation range upper limit value Vc + ΔVc.

At time t12 in the pulse period Tf (2), when the welding voltage average differential value Bv reaches a predetermined reference increase rate Bt1 as shown in FIG. To do. Therefore, the reference voltage waveform of the next pulse period Tf (3) is the same as the pulse period Tf (2). For this reason, as shown in FIG. 5C, the welding voltage limit value Vft in the pulse period Tf (3) is the same as the previous period. Similarly, the welding voltage limit value Vft in the pulse periods Tf (4) to (5) is the same as the pulse period Tf (2). As a result, during the long-term abnormal voltage generation period from time t1 to t2, the welding voltage limit value Vft has a waveform from which the abnormal voltage has been removed, so that the arc length (apparent arc length) is the pulse period Tf (1). It is possible to maintain an appropriate value in the same manner as.

  In the pulse period Tf (6), the generation of the abnormal voltage for a long time is completed and the cathode spot returns to the position immediately below the wire, so that the welding voltage Vw decreases to a normal value as shown in FIG. The reference voltage waveform in the pulse period Tf (6) remains the same as the pulse period Tf (2) because the update is still interrupted. However, since the welding voltage Vw is within the fluctuation range Vc ± ΔVc, the welding voltage limit value Vft is equal to the welding voltage Vw as shown in FIG.

  In the pulse period Tf (6), as shown in FIG. 5B, the update of the reference voltage waveform is resumed from the time t12 when the welding voltage average differential value Bv reaches the reference decrease rate Bt2. For this reason, in the pulse cycle Tf (7), the update by the moving average of the center voltage value Vc of the reference voltage waveform is resumed. The moving average may be performed at a predetermined period before the pulse period Tf (2) without using the pulse period during the abnormal voltage generation period for a long time, or may be performed at a predetermined period before the pulse period Tf (6). good. The operation after this pulse period Tf (7) is the same as in the prior art.

  FIG. 2 is a block diagram of a welding power source for carrying out the pulse arc welding control method according to the first embodiment. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial AC power supply (3-phase 200V, etc.) as input, performs output control such as inverter control and chopper control in accordance with a current error amplification signal Ei described later, and a welding voltage Vw and welding current suitable for welding. Iw is output. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 of the wire feeding device, and an arc 3 is generated between the welding wire 1 and the base material 2.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage average value calculation circuit VAV outputs a welding voltage average value signal Vav by moving and averaging the welding voltage detection signal Vd at a predetermined cycle (1 to a dozen cycles). The differentiation circuit BV differentiates the welding voltage average value signal Vav and outputs a welding voltage average differentiation value signal Bv. As shown in FIG. 1B, the comparison circuit CP is set to the High level when the welding voltage average differential value signal Bv reaches the reference increase rate Bt1, and then reset to the Low level when the reference decrease rate is reached. The comparison signal Cp is output. That is, the period in which the comparison signal Cp is at a high level substantially corresponds to a period in which an abnormal voltage has been generated for a long time.

  The welding voltage limit moving average value calculation circuit VRA receives a welding voltage limit value signal Vft, which will be described later, an elapsed time signal St, which will be described later, and the comparison signal Cp, and the comparison signal Cp is at a low level as described above with reference to FIG. In this case, the moving voltage average value of the welding voltage limit value signal Vft is averaged to update the peak voltage moving average value signal Vpr and the base voltage moving average value signal Vbr. When the comparison signal Cp is at the high level, the updating is interrupted and output. As described above, the reference voltage waveform generation circuit VC generates a reference voltage waveform automatically set by the peak voltage moving average value signal Vpr and the base voltage moving average value signal Vbr, and corresponds to an elapsed time signal St described later. The center voltage value signal Vc is output. Therefore, when the comparison signal Cp is at the Low level (when no abnormal voltage is generated for a long period of time), the center voltage value signal Vc is updated every pulse period, and when the comparison signal Cp is at the High level (for an abnormal voltage for a long period of time). The update will be interrupted.

  The fluctuation range setting circuit ΔVC outputs a predetermined fluctuation range signal ΔVc. The limit filter circuit FT receives the welding voltage detection signal Vd as an input, limits the fluctuation range Vc ± ΔVc from the center voltage value, and outputs a welding voltage limit value signal Vft. The average value calculation circuit VFA receives the welding voltage limit value signal Vft as an input, calculates an average value, and outputs a welding voltage limit average value signal Vfa.

  The voltage setting circuit VS outputs a predetermined voltage setting signal Vs. The voltage error amplification circuit EV amplifies the error between the welding voltage limit average value signal Vfa and the voltage setting signal Vs, and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit V / F converts the frequency to a frequency proportional to the value of the voltage error amplification signal Ev, and outputs a pulse period signal Tf that becomes a high level for a short time for each frequency (pulse period). The elapsed time counting circuit ST counts the elapsed time from the time point when the pulse period signal Tf changes to the high level (the start time of the peak rising period), and outputs the elapsed time signal St.

  The peak current setting circuit IPS outputs a predetermined peak current setting signal Ips. The base current setting circuit IBS outputs a predetermined base current setting signal Ibs. The current control setting circuit ISC receives the elapsed time signal St and outputs a current control setting signal Isc that rises from the base current setting signal Ibs to the peak current setting signal Ips during the peak rising period Tup. During the subsequent peak period Tp, the peak current setting signal Ips is output as the current control setting signal Isc, and during the subsequent peak falling period Tdw, the peak current setting signal Ips is changed to the base current setting signal Ibs. The falling current control setting signal Isc is output, and the base current setting signal Ibs is output as the current control setting signal Isc during the subsequent base period Tb. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current error amplification circuit EI amplifies the error between the current control setting signal Isc and the current detection signal Id and outputs a current error amplification signal Ei. By the block, the welding current Iw described above with reference to FIG. 5 corresponding to the current control setting signal Isc is supplied.

  According to the first embodiment described above, the update of the center voltage value of the reference voltage waveform is interrupted during the period from when the differential value of the welding voltage average value reaches the reference increase rate to the reference decrease rate. Therefore, the abnormal voltage can be substantially removed for a long time. For this reason, even if an abnormal voltage occurs for a long time, the apparent arc length can be maintained at an appropriate value, and good welding quality can be obtained.

[Embodiment 2]
FIG. 3 is a voltage waveform diagram showing the pulse arc welding control method according to the second embodiment of the present invention. FIG. 4A shows the welding voltage Vw, FIG. 4B shows the differential value Bv of the welding voltage average value Vav, and FIG. 4C shows the welding voltage limit value Vft. This figure corresponds to FIG. 1 described above, and an abnormal voltage has been generated for a long time from time t1 to t2. As shown in FIG. 5A, numerals (1) to (7) described above each pulse waveform represent pulse period Tf (1) to pulse period Tf (7). In addition, the hatched squares shown in FIG. 5C indicate the fluctuation range Vc ± ΔVc from the center voltage value Vc of the reference voltage waveform. Hereinafter, the difference from FIG. 1 described above will be described with reference to FIG.

  As shown in FIG. 1B, during the period from the time t11 when the welding voltage average differential value Bv reaches the reference increase rate Bt1 to the time t12 when the welding voltage average differential value Bt reaches the reference decrease rate Bt2, the first embodiment described above with reference to FIG. The updating of the center voltage value Vc of the reference voltage waveform is interrupted. On the other hand, in the present embodiment, as shown in FIG. 5C, the center voltage value Vc of the reference voltage waveform is continuously updated, but the fluctuation range ΔVc = 0 is temporarily set. As a result, the long-term abnormal voltage in the pulse periods Tf (2) to (5) is removed, and the welding voltage limit value Vft becomes a normal value. As a result, the arc length (apparent arc length) can be maintained at an appropriate value even when an abnormal voltage has been generated for a long time.

  FIG. 4 is a block diagram of a welding power source for carrying out the pulse arc welding control method according to the second embodiment described above. In the figure, the same blocks as those in FIG. 2 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from FIG. 2 will be described with reference to FIG.

  The second fluctuation range setting circuit ΔVC2 outputs a fluctuation range signal ΔVc having a predetermined value when the comparison signal Cp is at the Low level (when no abnormal voltage is generated for a long period of time), and when the comparison signal Cp is at the High level (for a long period of time). When an abnormal voltage is generated), the value is set to 0 and the fluctuation range signal ΔVc is output.

  According to the second embodiment described above, during the period from when the differential value of the welding voltage average value reaches the reference increase rate to the reference decrease rate, the fluctuation range of the reference voltage waveform is set to 0, Abnormal voltage can be substantially removed for a long time. For this reason, even if an abnormal voltage occurs for a long time, the apparent arc length can be maintained at an appropriate value, and good welding quality can be obtained.

  In Embodiments 1 and 2 described above, the average value Vav of the welding voltage Vw is differentiated, but the peak voltage or the base voltage may be differentiated. Further, a period in which the welding voltage average value Vav is larger than the reference value may be determined as a period in which the abnormal voltage is generated for a long time.

It is a voltage waveform diagram which shows the pulse arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for implementing the pulse arc welding control method which concerns on Embodiment 1 of this invention. It is a voltage waveform diagram which shows the pulse arc welding control method which concerns on Embodiment 2 of this invention. It is a block diagram of the welding power supply for implementing the pulse arc welding control method which concerns on Embodiment 2 of this invention. It is a wave form diagram of welding current Iw and welding voltage Vw of consumable electrode pulse arc welding in a prior art. It is a figure which shows the setting method of the reference voltage waveform Vc in a prior art. It is a voltage waveform figure at the time of the abnormal voltage generation | occurrence | production accompanying the arc re-ignition immediately after short circuit cancellation in a prior art. It is a figure which shows the time change of the welding voltage limiting value Vft for demonstrating the method of setting automatically the reference voltage waveform Vc mentioned above in FIG. It is a voltage waveform diagram when the abnormal voltage for a long time generate | occur | produces for demonstrating the subject of a prior art.

Explanation of symbols

1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll Bt1 Standard increase rate Bt2 Standard decrease rate BV Differentiating circuit Bv Welding voltage average differential value (signal)
CP comparison circuit Cp comparison signal EI current error amplification circuit Ei current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal FT limiting filter circuit Iav welding current average value Ib base current IBS base current setting circuit Ibs base current setting signal ID current Detection circuit Id Current detection signal Ip Peak current IPS Peak current setting circuit Ips Peak current setting signal ISC Current control setting circuit Isc Current control setting signal Iw Welding current PM Power supply main circuit ST Elapsed time counting circuit St Elapsed time signal ta Elapsed time Tb Base Period Tdw Peak falling period Tf Pulse period (signal)
Tp Peak period Tup Peak rising period V / F Voltage / frequency conversion circuit VAV Welding voltage average value calculation circuit Vav Welding voltage average value (signal)
Vb Base voltage Vba Base voltage average value Vbc Reference base voltage value Vbf Base voltage limit value Vbr Base voltage moving average value (signal)
VC Reference voltage waveform generation circuit Vc Center voltage value (signal) of reference voltage waveform
VD voltage detection circuit Vd welding voltage detection signal VFA average value calculation circuit Vfa welding voltage limit average value (signal)
Vft welding voltage limit value (signal)
Vp peak voltage Vpa peak voltage average value Vpc reference peak voltage value Vpf peak voltage limit value Vpr peak voltage moving average value (signal)
VRA welding voltage limit moving average value calculation circuit VS voltage setting circuit Vs voltage setting signal Vw welding voltage ΔVC fluctuation range setting circuit ΔVc fluctuation range (signal)
ΔVC2 Second fluctuation range setting circuit

Claims (2)

A welding current having a pulse waveform with a peak current and a base current as one cycle is applied to the arc, a welding voltage having a pulse waveform between the consumable electrode and the base material is detected, and the detected value of the welding voltage is used as a reference voltage of the pulse waveform. A welding voltage limit value is calculated by limiting within a predetermined fluctuation range from the waveform, and the reference voltage waveform is automatically updated to a voltage waveform generated by moving average of the welding voltage limit value, and the welding voltage limit value In the pulse arc welding control method for controlling the output of the welding power source so that the welding voltage limit average value obtained by averaging is substantially equal to a predetermined voltage setting value,
The average value of the welding voltage detection value is calculated, and when the increase rate of the welding voltage average value reaches the reference increase rate, the update of the reference voltage waveform is interrupted, and then the decrease rate of the welding voltage average value is The pulse arc welding control method characterized by restarting the update of the reference voltage waveform when a reference reduction rate is reached.   The pulse arc welding control method according to claim 1, wherein the updating of the reference voltage waveform is equivalently performed by changing the fluctuation range to zero.

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