JP4676081B2 - Output control method for pulse arc welding power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an output control method for forming external characteristics in a consumable electrode pulse arc welding power supply apparatus.
[0002]
[Prior art]
In consumable electrode pulse arc welding, it is necessary to maintain the arc length during welding at an appropriate value in order to obtain good welding quality. As an output control method of the welding power source apparatus for maintaining the arc length at an appropriate value, there are frequency modulation control, pulse width modulation control, peak current modulation, and the like, as will be described later with reference to FIG. In the present invention, as will be described later with reference to FIG. 3, in multi-electrode pulse arc welding using a plurality of welding wires, a peak current modulation control method having excellent characteristics among the above output control methods is targeted. Hereinafter, a conventional peak current modulation control method will be described.
[0003]
FIG. 2 is a current / voltage waveform diagram of pulse arc welding. 4A shows the time change of the output current Io, FIG. 2B shows the time change of the output voltage Vo, and FIGS. 1C1 to C3 show the arc generation state at each time. Hereinafter, a description will be given with reference to FIG.
[0004]
(1) Period from time t1 to t2 (peak period Tp)
During a predetermined peak period Tp (in the range of about 1 to 3 [ms]), as shown in FIG. 5B, the peak voltage Vp corresponding to the predetermined peak voltage set value Vsp is the welding wire / welded. Apply between objects. With this peak voltage setting value Vsp, the peak voltage Vp is set so as to have an appropriate arc length. On the other hand, during this period, the peak current Ip determined by the peak voltage Vp and the arc load is applied as shown in FIG. Therefore, the value of the peak current Ip varies depending on the peak voltage Vp and the arc load. However, in order to obtain a good bead appearance without spatter adhesion, the change width of the peak current Ip needs to be within the current range of 1 pulse per droplet transfer. In a mild steel wire having a diameter of 1.2 [mm], this current range is approximately 400 to 550 [A].
In addition, as shown in FIG. 1C1, the arc occurrence at this time is accelerated by the application of the peak current Ip having a large current value, and melting of the welding wire 1 is promoted, and a droplet 1a is formed at the tip of the wire. It becomes a state.
[0005]
(2) Period from time t2 to t3 (base period Tb)
During a predetermined base period Tb (in the range of about 2 to 20 [ms]), as shown in FIG. 5A, a predetermined base current Ib is energized to a value that does not promote melting of the welding wire. The value of the base current Ib is about 30 to 80 [A]. On the other hand, during this period, the base voltage Vb corresponding to the energization of the base current Ib is applied as shown in FIG.
In the arc generation state at this time, as shown in (C2) in the figure, immediately after the end of the peak period Tp, the droplets are detached from the tip of the wire and transferred to the work piece 2. Thereafter, as shown in FIG. 3C3, since the value of the base current Ib is small, the welding wire is hardly melted, and the wire tip position approaches the workpiece 2 by wire feeding.
[0006]
As described above, the welding wire 1 melts only during the peak period Tp and hardly melts during the base period Tb. Here, when the wire feeding speed is Wf [mm / s], the wire feeding amount during the period from time t1 to t3 is Wf1 = Wf × (Tp + Tb) [mm]. On the other hand, if the wire melting amount during the peak period Tp is Wm1 [mm], Wf1 = Wm1 must be satisfied in order to maintain the arc length at a constant value. The wire melting amount Wm1 is proportional to the product of the time length of the peak period Tp and the peak current value Ip. When the peak period Tp is a constant value, the wire melting amount Wm1 varies depending on the value of the peak current Ip. Further, the arc length during the period from time t1 to time t3 varies depending on the difference between the wire melt amount Wm1 and the wire feed amount Wf1. Therefore, the arc length can be controlled by changing the value of the peak current Ip. This output control method for controlling the arc length is called a peak current modulation control method.
[0007]
FIG. 3 is a current waveform diagram in two-electrode pulse arc welding for explaining the superior characteristics of the above-described pulse current modulation control method. This figure shows a case of two-electrode pulse arc welding in which two arcs A3 and B3 are simultaneously generated using two welding wires A1 and B1, as shown in FIG. FIGS. (B1) and (B2) show the case where the output control method is frequency modulation control, and (B1) shows the time change of the first output current AIo energizing the first arc A3. FIG. (B2) shows the time change of the second output current BIo energizing the second arc B3. FIGS. (C1) and (C2) show the case where the output control method is pulse current modulation control. FIG. (C1) shows the time change of the first output current AIo energizing the first arc A3. FIG. 3C2 shows the change over time of the second output current BIo for energizing the second arc B3. Hereinafter, a description will be given with reference to FIG.
[0008]
(1) For frequency modulation control
As shown in FIG. 5B1, the first arc A3 is energized with a predetermined peak current Ip during a predetermined peak period Tp from time t1 to time t2, and then the first arc A3 until time t3. A predetermined base current Ib is applied during the period of the pulse period Tf1. In the frequency modulation control, the arc length control is performed by controlling the first pulse period Tf1 so that the average value of the output voltage Vo becomes equal to a predetermined voltage setting value. Therefore, the first pulse period Tf1 changes every period according to the fluctuation of the arc load.
On the other hand, as shown in FIG. Similarly to the above, the peak current Ip is energized during the peak period Tp from time t1 to t2, and then the base current Ib is energized during the second pulse period Tf2 until time t4. Since the two arcs A3 and B3 are independently subjected to frequency modulation control (arc length control), the time length of the first pulse period Tf1 and the time length of the second pulse period Tf2 are different from each other. Different values. For this reason, even if the peak period Tp between times t1 and t2 can be synchronized, the next peak period Tp cannot be synchronized.
[0009]
In the two-electrode pulse arc welding, since two arcs A3 and B3 are generated adjacent to each other, the arc generation state tends to become unstable due to interference with each other. In order to solve this, a method has been proposed in which energization is performed by completely synchronizing the peak current Ip having a large current value for energizing the two arcs A3 and B3. However, as described above, in the frequency modulation control, the peak currents Ip of the two arcs cannot be energized in complete synchronization. Therefore, it is impossible to stabilize the arc generation state by suppressing the mutual interference of the arcs. Can not.
[0010]
Although omitted in the figure, in the pulse width modulation control, the above-described pulse period Tf is set to a constant value, and the arc length control is performed by changing the peak period Tp. For this reason, even in the pulse width modulation control, the peak period Tp cannot be completely synchronized, and as a result, the arc generation state cannot be stabilized by suppressing the mutual interference of the arcs.
[0011]
(2) For peak current modulation control
As shown in FIG. 11C1, the first arc A3 is energized with a peak current Ip1 during a predetermined peak period Tp from time t1 to t2, and then a predetermined base period from time t2 to t3. A predetermined base current Ib is energized during Tb. On the other hand, as shown in FIG. 2C2, the second arc B3 is supplied with the peak current Ip2 during the peak period Tp as described above, and then the base current Ib during the base period Tb as described above. Is energized. Therefore, since the peak currents Ip1 and Ip2 that energize the two arcs A3 and B3 can be perfectly synchronized, it is possible to suppress the mutual interference of the arcs and stabilize the arc generation state. As described above, in multi-electrode arc welding, the peak current modulation control has excellent characteristics not found in other modulation controls.
[0012]
FIG. 4 is a block diagram of a welding power source apparatus PS equipped with the above-described conventional peak current modulation control method. Hereinafter, a description will be given with reference to FIG.
The output control circuit INV receives a commercial AC power supply (three-phase 200 [V], etc.) as an input, and outputs an output voltage Vo and an output current Io suitable for an arc load according to an error amplification signal Ea described later by inverter control, thyristor phase control, and the like Is output. The direct current reactor DCL smoothes the output current Io. The welding wire 1 is fed through the welding torch 4 by the feeding roll 5a of the wire feeding device, and an arc 3 is generated between the workpiece 2 and the workpiece.
[0013]
The voltage detection circuit VD detects the output voltage before being smoothed by the DC reactor DCL, and outputs a voltage detection signal Vd. The peak voltage setting circuit VSP outputs a predetermined peak voltage setting signal Vsp. This signal Vsp may be set from outside the welding power supply device. The voltage error amplification circuit EV amplifies the error between the voltage detection signal Vd and the peak voltage setting signal Vsp and outputs a voltage error amplification signal Ev.
The current detection circuit ID detects the output current Io and outputs a current detection signal Id. The base current setting circuit ISB outputs a predetermined base current setting signal Isb. This signal Isb may be set from the outside of the welding power supply device. The current error amplification circuit EI amplifies an error between the current detection signal Id and the base current setting signal Isb, and outputs a current error amplification signal Ei.
[0014]
The switching timer circuit TPB is at a high level during a predetermined peak period Tp and is subsequently at a low level during a predetermined base period Tb, and outputs a switching signal Tpb that repeats these outputs. The switching circuit SW switches to the a side when the switching signal Tpb is at a high level and outputs the voltage error amplification signal Ev as an error amplification signal Ea. When the switching signal Tpb is at a low level, Switching to the b side outputs the current error amplification signal Ei as the error amplification signal Ea. Therefore, during the peak period Tp in which the switching signal Tpb is at a high level, the external characteristics of the welding power source device are constant voltage characteristics by constant voltage control using the peak voltage setting signal Vsp as a target value, while the switching signal Tpb is at a low level. During the base period Tb, the external characteristic of the welding power source device becomes a constant current characteristic by constant current control using the base current setting signal Isb as a target value.
[0015]
FIG. 5 is an external characteristic / arc characteristic relationship diagram for explaining the arc length control by the above-described peak current modulation control method. The figure shows the external characteristic L1 during the peak period, the horizontal axis shows the peak current Ip, and the vertical axis shows the peak voltage Vp. Hereinafter, a description will be given with reference to FIG.
As described above in the description of FIG. 4, the external characteristic L1 of the welding power source device becomes a constant voltage characteristic by the constant voltage control using the peak voltage setting signal Vsp as a target value during the peak period Tp. Generally, the slope Ss of the constant voltage characteristic L1 is about −2 [V / 100 A] due to the influence of the internal impedance of the welding power source device.
[0016]
Assuming that the arc characteristic when the arc length is in a steady state with an appropriate value is the characteristic Y1, the intersection P1 between the external characteristic L1 and the arc characteristic Y1 is an operating point in the steady state. At this operating point P1, the peak current Ip is Ip1 [A], and the peak voltage Vp is Vp1 [V] corresponding to the peak voltage setting signal Vsp.
In the steady state at the operating point P1, the arc length is transiently caused by fluctuations in the wire feed speed, irregular movement of the molten pool, fluctuations in the distance between the tip and the workpiece due to touching, etc. (hereinafter referred to as disturbance). Becomes longer, the arc characteristic changes from characteristic Y1 to characteristic Y2 accordingly. Since the external characteristic L1 does not change, the intersection P2 between the external characteristic L1 and the arc characteristic Y2 becomes the operating point after the change. At this operating point P2, the peak current Ip decreases to Ip2 [A], and the peak voltage Vp increases to Vp2 [V] because the arc length is increased. As described above in the description section of FIG. 2, the wire melting rate Wm is increased because the peak current Ip decreases from Ip1 [A] at the operating point P1 to Ip2 [A] at the operating point P2. It decreases from Wm1 [mm / s] at the point P1 to Wm2 [mm / s] at the operating point P2. On the other hand, the wire feed speed Wf [mm / s] is a constant value during welding. At the operating point P1, since the arc length is maintained at an appropriate value, Vf = Wm1. However, at the operating point P2, since the wire feed speed Wf> the wire melting speed Wm2, the arc length changes in the direction of shortening. This change continues until the operating point P2 moves rightward on the external characteristic L1 and returns to the operating point P1. Therefore, the arc length that becomes transiently long due to the disturbance returns to the steady state of the appropriate value as the operating point moves.
[0017]
The above operation will be described with specific numbers as follows. The following description is for the case of pulse arc welding using a mild steel wire having a diameter of 1.2 [mm]. It is assumed that the peak current Ip1 = 500 [A] and the peak voltage Vp1 = 45 [V] at the operating point P1. As a result, the arc length becomes slightly longer due to the disturbance, and as a result, when the peak voltage Vp2 = 46 [V] at the operating point P2 increases, the peak current Ip2 = 500 + (1 / −2) × 100 = 450 [A] decreases. . As described above in the description of FIG. 2, the peak current Ip2 = 450 [A] after this change is within the current range of 1 pulse / one droplet transfer.
[0018]
As described above, when the arc length becomes transiently long due to disturbance during welding, the peak current Ip is reduced by the constant voltage characteristic L1 and the amount of wire melting is reduced. As a result, the arc length is pulled back to the original state. . Conversely, when the arc length is shortened due to disturbance during welding, the peak current Ip is increased by the constant voltage characteristic L1 and the amount of wire melting is increased. As a result, the arc length is pulled back to the original state. This action is generally referred to as an arc length self-control action due to external characteristics.
[0019]
FIG. 6 is a current waveform / arc length relationship diagram when the arc length described above becomes transiently long. FIG. 4A shows the change over time of the output current Io, and FIGS. 4B to 6B show the arc generation state at each time. This figure shows a case where the arc length is instantaneously increased due to disturbance during the period from time t1 to time t2. Hereinafter, a description will be given with reference to FIG.
[0020]
(1) Period before time t1 (operating point P1)
Since the operating point before time t1 is the operating point P1 described above with reference to FIG. 5, the peak current is Ip1 [A] and the base current is Ib [A] as shown in FIG. Further, as shown in FIG. 5B1, the arc length is in a steady state with an appropriate value La1 [mm].
(2) Period from time t1 to t2 (operation point P2)
During the period from the time t1 to the time t2, as shown in FIG. 5B2, the arc length is instantaneously increased to La2 [mm] due to the disturbance.
(3) Period from time t2 to t3 (operating point P2)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from time t2 to t3 becomes P2, and as shown in FIG. 4A, the peak current decreases to Ip2 [A], As shown in the figure (B3), the arc length changes in the direction of shortening to La3 [mm].
[0021]
(4) Period from time t3 to t4 (middle of movement from operating point P2 to operating point P1)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from the time t3 to the time t4 is in the middle of movement from P2 to P1, and as shown in FIG. ], And the arc length changes in a direction of shortening to La31 [mm], as shown in FIG.
(5) Period from time t4 to t5 (middle of movement from operating point P2 to operating point P1)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from time t4 to t5 is in the middle of movement from P2 to P1, and as shown in FIG. ], And the arc length changes to La32 [mm] as shown in (B5).
(6) Period after time t5 (operating point P1)
Since the operating point during the period after time t5 is P1, the peak current returns to Ip1 [A] as shown in FIG. 5A, and the arc length is La1 as shown in FIG. Return to [mm].
[0022]
[Problems to be solved by the invention]
FIG. 7 is an external characteristic / arc characteristic relationship diagram corresponding to FIG. 5 described above for explaining the problem to be solved by the present invention. The figure shows the external characteristic L1 during the peak period, the horizontal axis shows the peak current Ip, and the vertical axis shows the peak voltage Vp. Further, the external characteristic L1 and the arc characteristic Y1 shown in the figure are the same as those in FIG. Hereinafter, a description will be given with reference to FIG.
[0023]
As in the case of FIG. 5 described above, the intersection P1 between the external characteristic L1 and the arc characteristic Y1 is an operating point in a steady state. At this operating point P1, the peak current Ip is Ip1 [A], and the peak voltage Vp is Vp1 [V] corresponding to the peak voltage setting signal Vsp.
In the steady state at the operating point P1, when the arc length becomes transiently very long due to disturbance, the arc characteristic changes from the characteristic Y1 to the characteristic Y3. Since the external characteristic L1 does not change, the intersection P3 between the external characteristic L1 and the arc characteristic Y3 becomes the operating point after the change. At this operating point P3, the peak current Ip is greatly reduced to Ip3 [A], and the peak voltage Vp is greatly increased to Vp3 [V] because the arc length is very long. Therefore, as shown in the figure, the peak current value Ip3 at the operating point P3 is a value outside the current range of 1 pulse per droplet transfer. For this reason, at the operating point P3, since 1 pulse per 1 droplet is not transferred, large spatter is generated, resulting in a poor bead appearance.
[0024]
As in the case of FIG. 5 described above, the above operation will be described with specific numerals as follows. The following description is for the case of pulse arc welding using a mild steel wire having a diameter of 1.2 [mm]. The peak current Ip1 at the operating point P1 = 500 [A] and the peak voltage Vp1 = 45 [V]. When the arc length becomes very long due to the disturbance and increases to the peak voltage Vp3 = 48 [V] at the operating point P3, the peak current Ip3 = 500 + (3 / −2) × 100 = 350 [A] decreases. Therefore, the peak current Ip3 = 350 [A] after the change is a value outside the current range of 1 pulse / one droplet transfer of about 400 to 550 [A] as described above.
[0025]
As described above, in pulse arc welding, by transferring one pulse per droplet by energization with a peak current Ip, it is possible to refine the droplet transfer and obtain a good bead appearance without spatter adhesion. However, as described above, when the arc length greatly changes due to disturbance, the peak current is greatly reduced to Ip3 [A] by the constant voltage characteristic L1. For this reason, the peak current value Ip3 is out of the current range of 1 pulse 1 droplet transfer, and the 1 pulse 1 droplet transfer is not maintained, so that the droplet transfer becomes large and the spatter of large spatter adheres. Bead appearance. As described above, in the case of a mild steel wire having a diameter of 1.2 [mm], the current range for causing one pulse per droplet transfer is in the range of about 400 to 550 [A]. Accordingly, when Ip3 = 350 [A], it is not possible to transfer one pulse per droplet. In order to keep the change width of the peak current Ip within the range of 400 to 550 [A], the change width of the peak voltage Vp accompanying the change of the arc length is within a very narrow range of +2 to −1 [V]. It needs to be a change. However, in actual welding, the change width of the peak voltage Vp accompanying the change in the arc length due to disturbance is often about ± 5 [V]. Therefore, in the peak current modulation control method of the prior art, there is a case where the state of 1 pulse per droplet transfer cannot always be maintained, so it is difficult to always obtain a good bead appearance without spatter adhesion. It was.
[0026]
Therefore, in the present invention, even when the arc length greatly changes due to disturbance during welding, the peak current value Ip changes while maintaining the state of one pulse per droplet transfer, and the arc length is returned to the original appropriate value. A peak current modulation control method that can be returned is provided.
[0027]
[Means for Solving the Problems]
The invention of claim 1 at the time of filing, as shown in FIGS.
A consumable electrode pulse that energizes a peak current Ip having a value that causes droplet transfer during a predetermined peak period Tp, and then energizes a base current Ib that does not promote melting of the welding wire during a predetermined base period Tb. In the output control method of the arc welding power supply device,
During the peak period Tp, the external characteristics of the welding power supply device are controlled to be drooping characteristics, and during the base period Tb, the external characteristics of the welding power supply apparatus are controlled. Constant current characteristics It is the output control method of the pulse arc welding power supply device to be controlled.
[0028]
The invention of claim 2 at the time of filing, as shown in FIG.
Claim 1 at the time of filing that the slope Ss of the drooping characteristic during the peak period Tp described in claim 1 at the time of filing is a value within a range of −5 [V / 100 A] or less and −20 [V / 100 A] or more. It is the output control method of the pulse arc welding power supply device described in.
[0029]
The invention of claim 3 at the time of filing, as shown in FIGS.
The slope Ss of the drooping characteristic during the peak period Tp described in claim 2 at the time of filing changes to an appropriate value corresponding to at least one of the wire feed speed, the diameter of the welding wire, or the material of the workpiece. It is an output control method of the pulse arc welding power supply device described in claim 2 at the time of filing.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
An example of an embodiment of the present invention is shown in FIG. 1 (same as FIG. 8),
A consumable electrode pulse that energizes a peak current Ip having a value that causes droplet transfer during a predetermined peak period Tp, and then energizes a base current Ib that does not promote melting of the welding wire during a predetermined base period Tb. In the output control method of the arc welding power supply device,
During the peak period Tp, the external characteristics of the welding power source are set within the range of -5 [V / 100A] or less and -20 [V / 100A] or more, the wire feed speed, the diameter of the welding wire, or the material of the workpiece. The pulse arc welding power source apparatus controls the drooping characteristic L2 having a slope Ss that changes to an appropriate value corresponding to at least one of the above and controls the external characteristic of the welding power source apparatus to a substantially constant current characteristic during the base period Tb. This is an output control method (peak current modulation control method).
[0031]
【Example】
[Example 1]
The invention of the first embodiment described below corresponds to the invention of claim 1 at the time of filing. The invention of the first embodiment controls the external characteristics of the welding power source device during the predetermined peak period Tp to the drooping characteristics instead of the constant voltage characteristics as in the prior art described above, and during the predetermined base period Tb, the welding power source This is a peak current modulation control method for controlling the external characteristics of the device to substantially constant current characteristics as in the above-described prior art. Hereinafter, the invention of Example 1 will be described with reference to the drawings.
[0032]
FIG. 8 is an external characteristic / arc characteristic relationship diagram corresponding to FIG. 7 described above for explaining the peak current modulation control method of the first embodiment. The figure shows the external characteristic L2 during the peak period, the horizontal axis shows the peak current Ip, and the vertical axis shows the peak voltage Vp. Further, in the figure, the external characteristic L2 during the peak period Tp is controlled to a drooping characteristic having a slope Ss = −10 [V / 100A]. The arc characteristics Y1 and Y3 are the same as in FIG. Hereinafter, a description will be given with reference to FIG.
[0033]
Similarly to FIG. 7 described above, the intersection P1 between the external characteristic L2 and the arc characteristic Y1 is an operating point in a steady state. At this operating point P1, the peak current Ip is Ip1 [A], and the peak voltage Vp is Vp1 [V] corresponding to the peak voltage setting signal Vsp.
In the steady state of the operating point P1, as in the case of FIG. 7 described above, when the arc length becomes transiently long due to a disturbance, the arc characteristic changes from the characteristic Y1 to the characteristic Y3. Since the external characteristic L2 does not change, the intersection P4 between the external characteristic L2 and the arc characteristic Y3 becomes the operating point after the change. At this operating point P4, the peak current Ip becomes Ip4 [A], and the peak voltage Vp increases to Vp4 [V] because the arc length has become very long.
[0034]
As in the case of FIG. 7 described above, the above operation will be described with specific numerals as follows. The peak current Ip1 at the operating point P1 = 500 [A] and the peak voltage Vp1 = 45 [V]. When the arc length becomes very long due to the disturbance and the peak voltage Vp4 at the operating point P4 increases to 48 [V], the peak current Ip4 = 500 + (3 / −10) × 100 = 467 [A] decreases. Since this peak current Ip4 = 467 [A] is within the current range of 1 pulse per droplet transfer, the droplet transfer is miniaturized and the amount of spatter generated is very small. In addition, the peak current value Ip changes according to the change of the arc length, and it has a self-control action of the arc length by an external characteristic that returns the arc length to the original proper value.
[0035]
Furthermore, even if the arc length changes more greatly than in the above case due to disturbance during welding, the peak current Ip is 400 to 550 [if the peak voltage Vp after the change is +10 to -5 [V]. A] changes within the current range of 1-pulse 1-droplet transfer, so that a good bead appearance without spatter adhesion can be obtained.
[0036]
FIG. 9 is a current waveform / arc length relationship diagram when the arc length described above in FIG. 8 becomes transiently long. FIG. 4A shows the change over time of the output current Io, and FIGS. 4B to 6B show the arc generation state at each time. This figure shows a case where the arc length is increased from the appropriate value La1 [mm] to La2 [mm] due to the disturbance during the period from the time t1 to the time t2, as in FIG. Hereinafter, a description will be given with reference to FIG.
[0037]
(1) Period before time t1 (operating point P1)
Since the operating point before time t1 is the operating point P1 described above with reference to FIG. 8, the peak current is Ip1 [A] and the base current is Ib [A], as shown in FIG. Further, as shown in FIG. 5B1, the arc length is an appropriate value La1 [mm].
(2) Period from time t1 to t2 (operation point P4)
During the period from the time t1 to the time t2, as shown in FIG. 5B2, the arc length is instantaneously increased to La2 [mm] due to the disturbance.
(3) Period of time t2 to t3 (operating point P4)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from time t2 to t3 becomes P4, and the peak current decreases to Ip4 [A] as shown in FIG. As shown in (B3), the arc length changes in a direction of shortening to La4 [mm].
[0038]
(4) Period from time t3 to t4 (middle of movement from operating point P4 to operating point P1)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from the time t3 to the time t4 is in the middle of movement from P4 to P1, and as shown in FIG. ], And the arc length changes in a direction of decreasing to La41 [mm], as shown in FIG.
(5) Period from time t4 to t5 (while moving from the operating point P4 to the operating point P1)
Due to the self-control action of the arc length due to the external characteristics described above, the operating point during the period from time t4 to t5 is in the middle of movement from P4 to P1, and as shown in FIG. ], And the arc length changes in a direction of decreasing to La42 [mm] as shown in FIG.
(6) Period after time t5 (operating point P4)
Since the operating point during the period after time t5 is P1, the peak current returns to Ip1 [A] as shown in FIG. 5A, and the arc length is appropriate as shown in FIG. Return to the value La1 [mm].
Since the peak currents Ip1, Ip2, Ip4, Ip41, and Ip42 described above are within the current range of 1 pulse per droplet transfer, a good bead appearance without spatter adhesion is obtained.
[0039]
FIG. 10 is a block diagram of an external characteristic control welding power source device CPS for carrying out the peak current modulation control method of the first embodiment. In this figure, the same circuit blocks as those in FIG. 4 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, the external characteristic inclination setting circuit SS and the external characteristic control circuit VSC indicated by dotted lines, which are circuit blocks different from those in FIG. 4, will be described with reference to FIG.
[0040]
The external characteristic inclination setting circuit SS outputs an external characteristic inclination setting signal Ss per predetermined 100 [A]. The external characteristic control circuit VSC receives the above-described external characteristic slope setting signal Ss, current detection signal Id, and peak voltage setting signal Vsp as input, and calculates the voltage control setting signal Vsc for forming external characteristics by performing the following calculation. Output.
Vsc = (Ss / 100) × (Id−Ist) + Vsp (1) Formula
However, the reference current value Ist [A] is a predetermined constant. This external characteristic control method will be described later with reference to FIG.
[0041]
FIG. 11 is an external characteristic diagram for explaining a method for controlling the external characteristic. In the figure, the horizontal axis indicates the current detection signal Id, and the vertical axis indicates the voltage control setting signal Vsc. Since this figure shows external characteristics during the peak period Tp, the current detection signal Id on the horizontal axis corresponds to the peak current Ip, and the voltage control setting signal Vsc on the vertical axis corresponds to the peak voltage Vp.
Hereinafter, a description will be given with reference to FIG.
[0042]
In this figure, when the value of the current detection signal Id shown on the horizontal axis is a predetermined constant reference current value Ist [A], the value of the voltage control setting signal Vsc shown on the vertical axis is the peak voltage setting signal Vsp. (P5 point). In addition, since the slope of the external characteristic L3 is Ss [V / 100A], the straight line expression of the external characteristic L3 is expressed by the above-described expression (1).
Here, when the value of the current detection signal Id changes from Id1 (Ist) [A] at the point P5 to Id2 [A] at the point P6, Vsc2 [V] is calculated as follows according to the equation (1).
Vsc2 = (Ss / 100) × (Id2−Ist) + Vsp
Similarly, when the value of the current detection signal Id changes to Id3 [A] at the point P7, Vsc3 [V] is calculated as follows according to the equation (1).
Vsc3 = (Ss / 100) × (Id3−Ist) + Vsp
As described above, by calculating the voltage control setting signal Vsc corresponding to the current detection signal Id based on the expression (1), a predetermined external characteristic (sagging characteristic) having a predetermined external characteristic slope Ss is formed. be able to.
[0043]
[Example 2]
The invention of Example 2 described below corresponds to the invention of claim 2 at the time of filing. In the invention of Example 2, the slope Ss of the drooping characteristic during the peak period Tp in the invention of Example 1 described above is a value in the range of −5 [V / 100 A] or less and −20 [V / 100 A] or more. This is a peak current modulation control method. Hereinafter, the invention of Example 2 will be described with reference to FIG.
[0044]
The peak current modulation control method according to the second embodiment can be implemented by the above-described external characteristic control welding power source device CPS of FIG. In other words, the value of the external characteristic inclination setting signal Ss in FIG.
FIG. 12 is a diagram showing an appropriate range of the external characteristic slope Ss under various welding conditions. In the figure, the horizontal axis represents the wire feed speed [m / min], and the vertical axis represents the slope Ss [V / 100A] of the external characteristic during the peak period Tp. The figure shows a mild steel wire having a diameter of 1.2 [mm], a mild steel wire having a diameter of 1.6 [mm], a stainless steel (SUS) wire having a diameter of 1.2 [mm], and a diameter of 1.2 [mm]. ] Shows an appropriate value of the external characteristic gradient Ss with respect to the wire feed speed when the aluminum alloy (Al) wire is used. As is apparent from the figure, the appropriate range of the external characteristic slope Ss is in the range of −5 or less and −20 or more.
[0045]
[Example 3]
The invention of Example 3 described below corresponds to the invention of claim 3 at the time of filing. In the invention of Example 3, the slope Ss of the drooping characteristic during the peak period Tp in the invention of Example 2 described above corresponds to at least one of the wire feed speed, the diameter of the welding wire, or the material of the workpiece. The peak current modulation control method changes to an appropriate value. Hereinafter, the invention of Example 3 will be described with reference to FIG.
[0046]
The block diagram of the welding power source apparatus for carrying out the peak current modulation control method of the third embodiment is a block diagram in which the external characteristic slope setting circuit SS of FIG. 10 described above is replaced with a circuit of FIG. Circuit blocks other than those described above are the same as those in FIG.
FIG. 13 is a block diagram of the external characteristic inclination setting circuit SS of the third embodiment. The external characteristic inclination setting circuit SS outputs an external characteristic inclination setting signal Ss having an appropriate value corresponding to the wire feeding speed, the diameter of the welding wire, and the material of the workpiece. The appropriate values of the external characteristic inclination Ss corresponding to the wire feed speed, the diameter of the welding wire, and the material of the workpiece are as shown in FIG. For example, when the wire feed speed is 10 [m / min], the diameter of the welding wire is 1.2 [mm], and the material of the workpiece is mild steel, the appropriate value of the external characteristic inclination Ss is the same as As shown in the figure, −9 [V / 100 A] is obtained. Further, when the wire feed speed is 10 [m / min], the diameter of the welding wire is 1.2 [mm], and the material of the workpiece is an aluminum alloy, the appropriate value of the external characteristic inclination Ss is: As shown in the figure, −20 [V / 100 A] is obtained.
[0047]
In Examples 1 to 3 described above, the DC pulse arc welding method has been described as the pulse arc welding method, but the same applies to the AC pulse arc welding method.
In other words, in AC pulse arc welding, the external characteristic is controlled to a drooping characteristic during the peak period of the electrode positive polarity, and the external characteristic is set to a substantially constant current characteristic during the base period of the positive electrode polarity and the negative electrode period of the negative electrode polarity. This is a peak current modulation control method to be controlled.
In the first to third embodiments described above, the external characteristic during the base period Tb is a substantially constant current characteristic. However, the substantially constant current characteristic includes a drooping characteristic having a steep slope Ss.
[0048]
【The invention's effect】
In the present invention, by setting the external characteristic during the peak period Tp as the drooping characteristic, the peak current Ip always changes within the current range of 1 pulse / one droplet transfer even if the arc length greatly changes due to disturbance during welding. As a result, the arc length is quickly returned to an appropriate value, so that a good bead appearance without spattering can be obtained.
Furthermore, in the invention of Example 3, the slope Ss of the external characteristic during the peak period Tp changes to an appropriate value corresponding to at least one of the wire feed speed, the diameter of the welding wire, or the material of the workpiece. The above effects can be exhibited even under various welding conditions.
[Brief description of the drawings]
FIG. 1 is an external characteristic / arc characteristic relationship diagram illustrating an embodiment;
[Figure 2] Current / voltage waveform diagram of pulse arc welding
Fig. 3 Current waveform diagram of two-electrode pulse arc welding
FIG. 4 is a block diagram of a conventional welding power supply device.
FIG. 5: Relationship between external characteristics and arc characteristics in the prior art
FIG. 6 is a relationship diagram of current waveform and arc length in the prior art.
FIG. 7 is an external characteristic / arc characteristic relation diagram for explaining a problem to be solved.
FIG. 8 is an external characteristic / arc characteristic relationship diagram of Example 1.
9 is a current waveform / arc length relationship diagram of Example 1. FIG.
FIG. 10 is a block diagram of a welding power source apparatus according to the first embodiment.
11 is an external characteristic diagram of Example 1. FIG.
FIG. 12: Appropriate range of external characteristic slope
FIG. 13 is a block diagram of an external characteristic inclination setting circuit SS according to the third embodiment.
[Explanation of symbols]
1 Welding wire
1a droplet
2 Workpiece
3 Arc
4a Contact tip of welding torch
5a Feeding roll of wire feeding device
A1 first welding wire
A3 First arc
AIo first output current
B1 Second welding wire
B3 Second arc
BIo second output current
CPS external characteristic control welding power supply
DCL DC reactor
Ea Error amplification signal
EI current error amplifier circuit
Ei Current error amplification signal
EV voltage error amplifier circuit
Ev Voltage error amplification signal
Ib Base current
ID current detection circuit
Id Current detection signal
INV output control circuit
Io output current
Ip peak current
ISB base current setting circuit
Isb Base current setting (value / signal)
Ist reference current value
L1-L3 External characteristics
La Arc length
P1 to P7 operating point
PS welding power supply
SS External characteristic inclination setting circuit
Ss External characteristic slope (setting signal)
SW switching circuit
Tb base period
Tf pulse period
Tp peak period
TPB switching timer circuit
Tpb switching signal
Vb Base voltage
VD voltage detection circuit
Vd Voltage detection signal
Vo output voltage
Vp peak voltage
VSC external characteristic control circuit
Vsc Voltage control setting signal
VSP peak voltage setting circuit
Vsp peak voltage setting (value / signal)
Y1-Y3 arc characteristics

Claims (3)

A consumable electrode pulse arc welding power supply apparatus that supplies a peak current having a value that causes droplet transfer during a predetermined peak period, and subsequently supplies a base current that does not promote melting of the welding wire during a predetermined base period. In the output control method of
An output control method for a pulse arc welding power supply apparatus that controls the external characteristic of the welding power supply apparatus to a drooping characteristic during the peak period and controls the external characteristic of the welding power supply apparatus to a constant current characteristic during the base period. 2. The output control method for a pulse arc welding power supply device according to claim 1, wherein the slope of the drooping characteristic during the peak period is a value within a range of −5 [V / 100 A] or less and −20 [V / 100 A] or more. The pulse arc welding power supply device according to claim 2, wherein the slope of the drooping characteristic during the peak period changes to an appropriate value corresponding to at least one of the wire feed speed, the diameter of the welding wire, or the material of the workpiece. Output control method.

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