JP2008068283A - Method of controlling output of consumable electrode arc welding source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform control in consumable electrode arc welding in such a manner that welding is not interrupted while preventing buckling of a welding wire caused by an increase in a feed load. <P>SOLUTION: A method for controlling the output of a consumable electrode arc welding source is provided for outputting a torque excess signal Td when a motor current Im flowing through a feed motor M exceeds a standard current value It during welding, and stopping the feed of the feed motor M and the output of a welding source PS based on the torque excess signal Td. In the method, when the welding state upon the output of the torque excess signal Td lies in a short circuit state, the feed of the feed motor M is stopped and the output of the welding source PS is continued, and when the welding state upon the output of the torque excess signal Td does not lie in a short circuit state, the feed of the feed motor M and the output of the welding source PS are stopped. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an output control method of a consumable electrode arc welding power source for suppressing a decrease in work efficiency due to buckling of a welding wire.

In the consumable electrode arc welding, a welding wire is fed to a welding part by a feeding motor, and welding voltage / current is supplied from a welding power source to generate an arc to perform welding. The welding wire is fed from the feeder to the welding torch body through the liner in the conduit cable. When the feeding load becomes heavy, the welding wire is buckled and cannot be fed. There are various reasons why the feeding load becomes heavy as follows.
(1) Cutting waste due to feeding of the welding wire accumulates inside the liner and the like, and the feeding load increases (increase in the feeding load of the feeding path).
(2) The welding wire is welded inside the power feed tip and the like, and the feeding load is increased (increasing the feeding load due to welding).
(3) A long-term short circuit exceeding several tens of ms occurs at the time of arc start or steady welding, and the welding wire tip is not melted and pressed against the base metal, increasing the feeding load (increasing feeding load due to long-term short-circuiting) ).

  The following prior art is commonly used as a method for preventing the above-described welding wire buckling. In other words, the feeding load is detected by the torque amount of the feeding motor, and if the feeding load increases and the torque amount exceeds the reference value, the possibility of buckling increases, so the welding wire feeding and the welding power supply output are stopped. To do. Usually, the amount of torque is detected by the value of the current (motor current) flowing through the feeding motor (see, for example, Patent Documents 1 to 3).

JP-A-5-31577 JP-A-8-215846 Japanese Patent Laid-Open No. 2003-200265

  When the buckling prevention method described above is activated, feeding of the welding wire and output of the welding power source are forcibly stopped even during welding. For this reason, the work in which the buckling prevention method is operated is poorly welded. In addition, when the buckling prevention method is activated, the welding line is stopped for a long time for recovery, so that the production efficiency is lowered. As described above, there are various types of causes for occurrence of buckling of the welding wire. Therefore, the present invention provides an output control method for a consumable electrode arc welding power source capable of avoiding buckling as much as possible and discriminating the cause of the increase in feeding load by type, while avoiding as much as possible the interruption of welding.

In order to solve the above-described problem, the first invention is to feed a welding wire by a feeding motor and to supply a welding voltage / current from a welding power source to perform welding, and to flow through the feeding motor during welding. Output control method of consumable electrode arc welding power source that outputs torque excess signal when motor current exceeds reference current value and stops feeding of feeding motor and output of welding power source based on this torque excess signal In
When the welding state when the torque excess signal is output is a short circuit state, the feeding of the feeding motor is stopped and the output of the welding power source is continued,
An output control method for a consumable electrode arc welding power source, wherein the feeding of the feeding motor and the output of the welding power source are stopped when the welding state when the torque excess signal is output is not a short circuit state It is.

  2nd invention is a state where the welding state when the torque excess signal is output is not in a short-circuit state, and only when the arc length is longer than a reference arc length, the feeding of the feeding motor and the The output control method for a consumable electrode arc welding power source according to the first aspect of the invention, wherein the output of the welding power source is stopped.

  According to the first aspect of the invention, when a long-term short circuit occurs at the time of arc start, steady welding or the like and the feeding load increases, this state is discriminated and only the feeding is performed while the output of the welding power source continues. Stop. Thus, buckling can be prevented without forcibly terminating welding. For this reason, the welding line is not stopped by welding interruption, and the welding line is not stopped. The number of occurrences of buckling due to a long-term short circuit occupies a considerable proportion of the total number of occurrences of buckling, so the effect of avoiding welding interruption is great.

  Furthermore, according to the second aspect of the invention, in addition to the effect of the first aspect, when the torque amount of the feed motor exceeds the reference value, the short circuit state is not established and the arc length exceeds the reference value. Output and feed are stopped only when For this reason, the detection system for preventing buckling is improved.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source PS for carrying out an output control method for a consumable electrode arc welding power source according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The output control circuit PM performs output control such as inverter control with a commercial power source such as three-phase 200V as an input, and outputs a welding voltage Vw and a welding current Iw suitable for arc welding. The output control circuit PM stops output when an output stop signal Ps described later is at a high level. The welding wire 1 is fed through the cable of the welding torch 4 by the rotation of the feed roll 5 coupled to the feed motor M, and an arc 3 is generated between the base metal 2 and welding is performed.

  The feed motor control circuit MC controls the rotational speed of the feed motor M described above. The feed motor control circuit MC stops the rotation of the feed motor M when a feed stop signal Ms described later is at a high level. The motor current detection circuit IM detects a motor current that is substantially proportional to the amount of torque applied to the feeding motor M, and outputs a motor current detection signal Im. The torque excess determination circuit TD outputs a torque excess signal Td that becomes High level when the value of the motor current detection signal Im exceeds the reference current value It.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD determines that the welding state is a short circuit state based on the value of the voltage detection signal Vd, and outputs a short circuit determination signal Sd.

The buckling prevention circuit ZP, when the above torque excess signal Td becomes High level (torque excess),
(1) If the short circuit determination signal Sd is at a high level (short circuit), an output stop signal Ps = Low level and a feed stop signal Ms = High level are output, and then the short circuit determination signal Sd is at a low level (non-short circuit) ), An output stop signal Ps = Low level and a feed stop signal Ms = Low level are output,
(2) If the short circuit determination signal Sd is at the Low level (non-short circuit), the output stop signal Ps = High level and the feed stop signal Ms = High level are output. That is, if the welding state is not a short-circuited state when the torque excess signal Td = High level, both output and feeding of the output control circuit PM are stopped. On the other hand, when the welding state when the torque excess signal Td = High level is a short circuit state, the output of the output control circuit PM is continued and only the feeding is stopped. In this case, the short circuit is released by continuing the output, and the feeding is resumed after the short circuit is released.

  FIG. 2 is a timing chart of each signal of the welding power source PS described above with reference to FIG. 1 when a long-term short circuit occurs at the arc start and the feed load increases. This figure shows the output control method of the consumable electrode arc welding power source according to Embodiment 1 of the present invention. (A) shows the welding voltage Vw, (B) shows the welding current Iw, (C) shows the motor current detection signal Im, and (D) shows the torque excess signal Td. (E) shows the short circuit determination signal Sd, (F) shows the output stop signal Ps, and (G) shows the feed stop signal Ms. Hereinafter, a description will be given with reference to FIG.

  When a welding start command (not shown) is input from the outside at time t1, a no-load voltage is applied between the welding wire and the base material as the welding voltage Vw as shown in FIG. Since it is fed at a slow-down speed, a motor current Im smaller than that during steady welding is energized as shown in FIG.

  When the welding wire reaches and comes into contact with the base metal at time t2, the welding voltage Vw becomes a low short-circuit voltage value as shown in FIG. 9A, and the welding current Iw is shown in FIG. Is energized. At the time of arc start, since the temperature of the welding wire is low, it is not possible to smoothly shift to the arc, and a long-term short circuit exceeding tens of ms is likely to occur. This is also the case in this figure. Since the feed speed changes to a steady feed speed at time t2, the motor current Im increases as shown in FIG. Further, as shown in FIG. 5E, the short circuit determination signal Sd changes to the high level. Since the short-circuit state is continued, the tip of the wire is pressed against the base material, and the feed load increases suddenly, increasing the torque amount of the feed motor. Accordingly, the motor current Im increases as shown in FIG.

  At time t3, when the motor current Im exceeds the reference current value It as shown in FIG. 10C, the torque excess signal Td becomes High level as shown in FIG. At time t3, the short circuit determination signal Sd is at a high level (short circuit) as shown in FIG. 8E, and therefore the output stop signal Ps is at a low level (output continuation) as shown in FIG. ), And as shown in FIG. 5G, the feed stop signal Ms becomes High level (feed stop). Therefore, since the output is continued, the welding current Iw is continuously energized as shown in FIG. On the other hand, since there is a possibility of buckling in this state, feeding is stopped.

  When the welding current Iw is energized at time t4 and the short circuit is released and an arc is generated as shown in FIG. 5A, the short circuit determination signal Sd changes to the low level as shown in FIG. . In response to this, the feed stop signal Ms returns to the low level as shown in FIG. 5G, so that the feeding of the welding wire is resumed, and the steady feed as shown in FIG. A motor current Im corresponding to the speed is energized. After time t4, the steady welding voltage Vw and the welding current Iw are output as shown in FIGS. Since this figure is a case of pulse arc welding, a pulse voltage is applied and a pulse current is energized.

  FIG. 3 is a timing chart of each signal of the welding power source PS described above with reference to FIG. 1 when a long-term short circuit occurs during steady welding. This figure corresponds to FIG. 2 described above, and the signal names in FIGS. (A) to (G) are the same. Hereinafter, a description will be given with reference to FIG.

  When a short circuit occurs at time t1, as shown in FIG. 5E, the determination signal Sd becomes High level as shown in FIG. If this short circuit continues for a long time, the wire tip protrudes from the base material, so that the feeding load increases, and the motor current Im increases as shown in FIG. At time t2, when the motor current Im exceeds the reference current value It as shown in FIG. 8C, the torque excess signal Td becomes High level as shown in FIG. Since the short-circuit determination signal Sd at this time is at the high level, the output stop signal Ps remains at the low level as shown in FIG. 5F, and the feed stop signal as shown in FIG. Ms changes to a high level. Therefore, since the output of the welding power source is continued, the energization of the welding current Iw is continued as shown in FIG. On the other hand, since feeding stops, buckling can be prevented.

  When the arc is generated by releasing the long-term short-circuit by applying the welding current Iw at time t3, the welding voltage Vw changes from the short-circuit voltage value to the arc voltage value as shown in FIG. As shown, the short circuit determination signal Sd changes to the Low level. In response to this, as shown in FIG. 5G, the feed stop signal Ms changes to the Low level, and the feed of the welding wire is resumed. Thereafter, the welding state is in a steady state, and a steady welding voltage Vw is applied as shown in FIG. 9A, and a steady welding current Iw is applied as shown in FIG.

  According to the first embodiment described above, when a long-term short circuit occurs at the time of arc start, steady welding, etc., and the feeding load increases, this state is discriminated and only the feeding is performed while the output of the welding power source continues. To stop. Thus, buckling can be prevented without forcibly terminating welding. For this reason, the welding line is not stopped by welding interruption, and the welding line is not stopped. The number of occurrences of buckling due to a long-term short circuit occupies a considerable proportion of the total number of occurrences of buckling, so the effect of avoiding welding interruption is great.

[Embodiment 2]
FIG. 4 is a block diagram of a welding power source PS for carrying out the polarity switching short-circuit arc welding method according to Embodiment 2 of the present invention. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, a block different from FIG. 1 will be described.

  The arc length excess determining circuit AD outputs an arc length excess signal Ad that becomes a high level when the value of the voltage detection signal Vd exceeds the reference voltage value Vt. This utilizes the fact that the arc length is approximately proportional to the welding voltage value. As described above, buckling also occurs due to an increase in the feeding load of the feeding path or an increase in the feeding load due to welding. In such a state, the arc length becomes excessively long because the feeding is delayed or stopped. Therefore, when the arc length becomes longer than the reference arc length, the feeding load increases and there is a risk of buckling. Such an increase in the feeding load can also be detected by the torque excess signal Td described above. However, the feeding load on the feeding path may increase transiently, or welding may temporarily occur and the feeding load may temporarily increase. For this reason, when the detection sensitivity of the torque excess discrimination circuit TD is high (the reference current value It is lowered), there is a high risk of erroneous detection. On the other hand, if the detection sensitivity is lowered (the reference current value It is increased), there is a case where the detection cannot be performed before buckling occurs. In order to improve this problem, in this embodiment, the logical seat (AND) of the torque excess signal Td and the arc length excess signal Ad is taken to improve the detection accuracy.

The second buckling prevention circuit ZP2 is configured such that when the torque excess signal Td becomes High level (torque excess),
(1) If the short circuit determination signal Sd is High level (short circuit), an output stop signal Ps = Low level and a feed stop signal Ms = High level are output, and then the short circuit determination signal Sd is Low level (non-short circuit). Then, the output stop signal Ps = Low level and the feed stop signal Ms = Low level are output,
(2) If the short circuit determination signal Sd is at the low level (non-short circuit) and the arc length excess signal Ad is at the high level (arc length excess), the output stop signal Ps = High level and the feed stop signal Ms = High level is output. That is, if the welding state is an arc length excess state when the torque excess signal Td = High level, both the output control circuit PM and the feeding are stopped. On the other hand, when the welding state when the torque excess signal Td = High level is a short circuit state, the output of the output control circuit PM is continued and only the feeding is stopped. In this case, the short circuit is released by continuing the output, and the feeding is resumed after the short circuit is released.

  FIG. 5 is a timing chart of each signal of the welding power source PS described above with reference to FIG. 4 when welding occurs and the feeding load increases. This figure shows an output control method of the consumable electrode arc welding power source according to Embodiment 2 of the present invention. (A) shows the welding voltage Vw, (B) shows the welding current Iw, (C) shows the motor current detection signal Im, and (D) shows the torque excess signal Td. (E) shows the short circuit determination signal Sd, (F) shows the output stop signal Ps, (G) shows the feed stop signal Ms, and (H) shows the arc length. The excess signal Ad is shown. Hereinafter, a description will be given with reference to FIG.

  The figure shows the case of pulse arc welding. During the period before time t1, a pulse voltage is applied as shown in FIG. 5A, and a pulse current is applied as shown in FIG. At time t1, welding occurs, the feeding load increases, and the arc length becomes excessive. As a result, as shown in FIG. 5B, the pulse voltage exceeds the reference voltage value Vt, and as shown in FIG. 5H, the arc length excess signal Ad becomes High level.

  At time t2, when the motor current Im exceeds the reference current value It as shown in FIG. 8C, the torque excess signal Td becomes High level as shown in FIG. Therefore, the output stop signal Ps becomes High level and the output is stopped as shown in FIG. 5F, and the feed stop signal Ms becomes High level and the feed is stopped as shown in FIG. To stop. The above is the case of welding, but the same applies when the feeding load of the feeding path increases.

  According to the second embodiment described above, when the torque amount of the feeding motor exceeds the reference value, output and feeding are performed only when the short circuit state and the arc length exceed the reference value. Stop. This improves the buckling prevention system.

It is a block diagram of welding power source PS concerning Embodiment 1 of the present invention. It is a timing chart which shows the output control method of the consumable electrode arc welding power supply which concerns on Embodiment 1 of this invention. 3 is a timing chart different from FIG. 2 showing the output control method of the consumable electrode arc welding power source according to Embodiment 1 of the present invention. It is a block diagram of welding power supply PS concerning Embodiment 2 of the present invention. It is a timing chart which shows the output control method of the consumable electrode arc welding power supply which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll AD Arc length excess discrimination circuit Ad Arc length excess signal IM Motor current detection circuit Im Motor current detection signal It Reference current value Iw Welding current M Feeding motor MC Feeding Motor control circuit Ms Feed stop signal PM Output control circuit PS Welding power supply Ps Output stop signal SD Short circuit determination circuit Sd Short circuit determination signal TD Torque excess determination circuit Td Torque excess signal VD Voltage detection circuit Vd Voltage detection signal Vt Reference voltage value Vw Welding Voltage ZP Buckling prevention circuit ZP2 Second buckling prevention circuit

Claims (2)

Welding wire is fed by a feed motor and welding voltage / current is supplied from a welding power source to perform welding. When the motor current flowing through the feed motor exceeds the reference current value during welding, a torque excess signal is sent. In the output control method of the consumable electrode arc welding power source that outputs and stops the feeding of the feeding motor and the output of the welding power source based on the torque excess signal,
When the welding state when the torque excess signal is output is a short circuit state, the feeding of the feeding motor is stopped and the output of the welding power source is continued,
An output control method for a consumable electrode arc welding power source, wherein the feeding of the feeding motor and the output of the welding power source are stopped when the welding state when the torque excess signal is output is not a short circuit state . The feeding of the feeding motor and the output of the welding power source are stopped only when the welding state when the torque excess signal is output is not a short-circuited state and the arc length is longer than the reference arc length. The output control method for a consumable electrode arc welding power source according to claim 1.

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