JP2014039937A - Consumable electrode arc welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a welding state from being unstable as automatic correction on constriction detection sensitivity is improperly made when constriction detection control and feed speed variable control for making a welding current constant are both in operation.SOLUTION: In a consumable electrode arc welding control method of performing constriction detection control to achieve welding by reducing a welding current once a constriction of a droplet being short-circuited is detected, generating an arc again, and automatically correcting constriction detection sensitivity, and also performing welding by bringing a feed speed Fw under variable control so that an average value Iav of the welding current becomes equal to a current set value, a variation rate of the feed speed Fw is detected and the automatic correction on the constriction detection sensitivity is inhibited during a feed speed abrupt change period Tcf in which the variation rate of the feed speed is equal to or larger than a reference value. Consequently, a welding state is prevented from being unstable owing to improper automatic correction on the constriction detection sensitivity in the feed speed abrupt change period Tcf.

Description

  The present invention performs the necking detection control for reducing the welding current when the droplet constriction is detected and regenerating the arc, and the feeding speed variable control for controlling the feeding speed so that the welding current becomes equal to the set value. The present invention relates to a consumable electrode arc welding control method for welding.

  In the invention of Patent Document 1, in consumable electrode arc welding in which an arc generation state and a short-circuit state are repeated between a welding wire and a base material, a constriction of droplets, which is a precursor to the occurrence of an arc again from the short-circuit state, is detected. The change in the voltage value or resistance value between the base metal and the base metal is detected when it reaches the squeezing detection reference value, and when this squeezing is detected, the welding current flowing to the short-circuit load is suddenly reduced, and the arc is in a state of a small current value. The output is controlled to reoccur. In this way, since the current value at the time of arc re-generation can be reduced, the amount of spatter generated can be reduced. In the following description, the time from the detection time of the constriction for each short circuit to the reoccurrence time of the arc is referred to as the constriction detection time.

  In the above-described constriction detection control, it is important to accurately detect constriction in order to increase the sputter reduction effect. The occurrence of necking and its progress vary depending on various welding conditions such as the type of shielding gas, the type of welding wire, the shape of the base metal, the feeding speed of the welding wire, the welding position, the welding speed, and the state of routing of the welding cable. To do. Therefore, it is necessary to optimize the sensitivity for detecting the occurrence of necking according to the welding conditions. The squeezing detection sensitivity can be adjusted by increasing or decreasing the squeezing detection reference value. That is, when the squeezing detection reference value is increased, the squeezing detection sensitivity is decreased, and conversely, it is increased when the squeezing detection reference value is decreased. If the squeezing detection reference value is too large, the squeezing detection sensitivity will be too low, and the squeezing detection time will be too short, and the welding current cannot be reduced sufficiently until the arc reoccurs, so the spatter reduction effect will be small. . On the other hand, if the squeezing detection reference value is too small, the squeezing detection sensitivity will be too high, and the squeezing detection time will be too long and the arc will not reoccur, making the welding state unstable. Therefore, it can be said that the squeezing detection time is in the range of about 50 to 1000 μs when the squeezing detection reference value is set to an appropriate value.

  As described above, the appropriate value for the squeezing detection reference value varies depending on various welding conditions. For this reason, it is necessary to optimize the squeezing detection reference value in a state where the welding power source is installed in the actual welding line and the welding conditions are fixed. However, in order to conduct an experiment for optimizing the squeezing detection reference value in the welding line, there is a problem that it takes a lot of time for production preparation. For this reason, control for automatically correcting the squeezing detection reference value to an appropriate value (automatic correction control of the squeezing detection reference value) has been proposed. Hereinafter, the automatic correction control of the squeezing detection reference value will be described (see Patent Document 1).

  The first method of automatic correction control detects the squeezing detection time for each short circuit, and automatically controls the squeezing detection reference value to an appropriate value by feedback control so that this squeezing detection time becomes equal to a predetermined time set value. To do.

  In the second method of automatic correction control, the squeezing detection time is detected and stored for each short circuit, and each value of the squeezing detection times for a predetermined number of past plural numbers from the stored current time is less than a predetermined minimum value. When a certain number is equal to or greater than a predetermined minimum value, the squeezing detection reference value is decreased by a predetermined decrease value, and the number of squeezing detection times stored is equal to or greater than a predetermined maximum value. When the number is greater than or equal to the number, the squeezing detection reference value is increased by a predetermined increase value, and these processes are repeated for each short circuit.

  In the invention of Patent Document 2, the feed rate of the welding wire is feedback controlled so that the welding current is equal to a predetermined current set value. In normal consumable electrode arc welding, the feeding speed during welding is a constant value. On the other hand, in the invention of Patent Document 2, the feeding speed is variably controlled so that the welding current value becomes constant even when the distance between the power supply tip and the base material changes. Since the penetration depth of the base material is substantially proportional to the welding current value, the penetration depth becomes uniform when the welding current value becomes constant. In normal arc welding, welding is performed with a constant distance between the power supply tip and the base material. However, in the case of deep groove welding, multi-layer welding, etc., it may be difficult to maintain a constant distance between the power supply tip and the base material due to problems such as interference between the welding torch and the base material. . Thus, in the welding in which the distance between the power supply tip and the base material varies, the invention of Patent Document 2 is one of important welding qualities because the welding current value is kept constant by variably controlling the feeding speed. It is possible to make uniform by suppressing fluctuations in the penetration depth.

Japanese Patent No. 4907789 Japanese Patent Laid-Open No. 7-51854

  When the necking detection control with automatic correction of the necking detection reference value described above is performed and welding is performed while performing the above-described variable control of the feeding speed, if the feeding speed changes rapidly by the feeding speed variable control, As a result, the state of formation of the constriction of the droplets varies greatly. In such a state, the automatic correction control of the squeezing detection reference value malfunctions, and the squeezing detection reference value greatly deviates from the appropriate value, and a false detection of squeezing occurs and the welding state becomes unstable. Arise. For this reason, in the prior art, the operation of the constriction detection control is prohibited when the feed speed variable control is performed. However, this causes a problem that the amount of spatter generated increases.

  Therefore, in the present invention, there is provided a consumable electrode arc welding control method capable of keeping the welding state stable even when welding is performed by operating both the necking detection control with automatic correction of the necking detection reference value and the feed speed variable control. The purpose is to provide.

In order to solve the above-mentioned problem, the invention of claim 1 is based on the fact that the constriction of droplets, which is a precursor to the occurrence of an arc again from a short-circuit state, is caused by a change in voltage value or resistance value between the welding wire and the base material. Detected by reaching the squeezing detection reference value. When this squeezing is detected, the welding current applied to the short-circuit load is reduced to regenerate the arc, and squeezing is detected from the time when the squeezing is detected until the time when the squeezing of the arc occurs The squeezing detection reference value is automatically corrected so that the time is within a predetermined time setting range, and squeezing detection control for welding is performed, a smooth value of the welding current is detected, and the welding current smoothing value is determined in advance. In the consumable electrode arc welding control method of performing welding control by performing feedback control of the feed speed of the welding wire so that the current set value becomes equal, and performing feed speed variable control,
Detecting the rate of change of the feed rate, and prohibiting automatic correction of the squeezing detection reference value during a feed rate sudden change period in which the rate of change of the feed rate is equal to or greater than a predetermined reference value;
This is a consumable electrode arc welding control method.

The invention of claim 2 maintains the prohibition of automatic correction of the squeezing detection reference value until a predetermined period elapses from the time when the feed speed sudden change period ends.
The consumable electrode arc welding control method according to claim 1.

In the invention of claim 3, the automatic correction of the necking detection reference value is:
(1) detecting the constriction detection time for each short circuit;
(2) When the squeezing detection time is less than or equal to the lower limit time of the time setting range, 1 is subtracted from the counter value. When the squeezing detection time is greater than or equal to the upper limit time of the time setting range, 1 is added to the counter value. Adding steps,
(3) When the counter value reaches a negative reference value that is a predetermined negative value, the squeezing detection reference value is decreased by a predetermined decrease value, and the counter value is reset to 0. When the positive reference value which is a predetermined positive value is reached, the squeezing detection reference value is increased by a predetermined increase value and the counter value is reset to 0.
The consumable electrode arc welding control method according to claim 1 or 2.

  According to the present invention, the automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time for a short circuit that occurs during the rapid change of the feeding speed. During the rapid change of the feeding speed, the formation state of the droplet constriction varies greatly. In such a state, the automatic correction of the squeezing detection reference value malfunctions, and the squeezing detection reference value deviates greatly from the appropriate value, so that a false detection of squeezing occurs and the welding state becomes unstable. On the other hand, in the present invention, automatic correction of the squeezing detection reference value is prohibited during the sudden change of the feeding speed, so that the squeezing detection control and automatic feeding speed variable control that operate together are automatically operated. Even if it makes it, it can maintain a welding state in a stable state.

It is a block diagram of the welding power supply for implementing the consumable electrode arc welding control method which concerns on embodiment of this invention. It is a timing chart which shows the constriction detection control method which concerns on embodiment of this invention. It is a timing chart which shows the feed speed variable control method which concerns on embodiment of this invention when the change rate of feed speed is more than a reference value. It is a timing chart which shows the feed speed variable control method which concerns on embodiment of this invention when the change rate of feed speed is less than a reference value.

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

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

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

  The current reducing resistor R is inserted between the power supply main circuit PM and the welding torch 4. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (about 0.01 to 0.03Ω). For this reason, when the current reducing resistor R is inserted into the energization path by the constriction detection control, the energy accumulated in the DC reactor in the welding power source and the reactor of the external cable is suddenly discharged. The transistor TR is connected in parallel with the current reducing resistor R and is controlled to be turned on or off in accordance with a drive signal Dr described later.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the feed motor WM, and an arc 3 is generated between the base wire 2 and the welding wire 1. A welding voltage Vw is applied between the welding wire 1 and the base material 2, and a welding current Iw is passed through the arc 3.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current smoothing circuit IAV smoothes the current detection signal Id as an input, and outputs a welding current smoothing signal Iav. This smoothing is performed using a smoothing circuit including a resistor and a capacitor, a low-pass filter, and the like. When a low-pass filter is used, the smoothing time constant can be set by setting a cutoff frequency. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd.

  The current setting circuit IR outputs a predetermined current setting signal Ir that becomes a target current value in the feed speed variable control. The feeding error amplification circuit EF amplifies an error between the current setting signal Ir (+) and the welding current smoothing signal Iav (−), and outputs a feeding error amplification signal Ef. The feed speed setting circuit FR integrates the feed error amplification signal Ef and outputs a feed speed setting signal Fr. Integration is performed during welding, and Fr = Fr0 + ∫Ef · dt. Here, Fr0 is an initial value. This initial value Fr0 is set to an appropriate value in the range of about 6 to 10 m / min. Since the feed speed is determined when the value of the current setting signal Ir, the material and diameter of the welding wire, and the distance between the power supply tip and the base material at the start of welding are determined, this feed speed may be set to the initial value Fr0. The feed control circuit FC receives the feed speed setting signal Fr as an input, and feeds a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to the set value to the feed motor WM. Output.

  The feed rate change rate detection circuit DF receives the feed rate setting signal Fr, detects the rate of change of the feed rate setting signal Fr, and outputs a feed rate change rate detection signal Df. The feed speed setting signal Fr is a signal for setting a feed speed Fw that changes every moment by the feed speed variable control. The rate of change of the feeding speed setting signal Fr can be detected by differentiating the feeding speed setting signal Fr. Alternatively, the feed speed setting signal Fr may be sampled every predetermined period (for example, 10 ms), and the difference between the current sampling value and the previous sampling value may be detected as a change rate. The rate of change of the feed speed setting signal Fr corresponds to the rate of change of the feed speed Fw. Furthermore, the rate of change may be calculated by directly detecting the rotation speed (feed speed Fw) of the feed motor WM using an armature voltage, a tachometer, an encoder, or the like.

  The feed speed rapid change determination circuit CF receives this feed speed change rate detection signal Df, and when the feed speed change rate detection signal Df is equal to or higher than a predetermined reference value, it becomes High level, and when it becomes less, it becomes Low level. A feed speed rapid change determination signal Cf is output. That is, the period during which the rate of change of the feeding speed Fw is equal to or greater than the reference value is determined as the feeding speed sudden change period Tcf. When both the necking detection control and the feed speed variable control are operated, a malfunction of automatic correction of the necking detection reference value occurs when the feed speed Fw is changed by the feed speed variable control, and the welding state is not good. May become stable. An automatic correction malfunction is more likely to occur as the rate of change of the feeding speed Fw increases. Therefore, the reference value is set to the upper limit value of the change rate of the feeding speed Fw that does not cause a malfunction of automatic correction of the squeezing detection reference value. Further, the above-described feed speed rapid change determination signal Cf may be off-delayed for a predetermined period from the High level to the Low level. This is because even if the rate of change of the feeding speed Fw becomes less than the reference value, a state in which a malfunction of automatic correction still tends to occur continues for a predetermined period. The predetermined period is set to 100 ms, for example.

  The short circuit / arc discriminating circuit SD receives the voltage detection signal Vd as described above, and when the value is less than a predetermined short circuit / arc discriminating value, the short circuit / arc discriminating circuit determines that the short circuit is in a high level, A short circuit / arc determination signal Sd which is determined to be in the arc generation state and becomes Low level is output.

The correction amount calculation circuit DUD receives the feed speed rapid change determination signal Cf and the squeezing detection signal Nd described later as input, and outputs the correction amount signal Δud.
1) When the feed speed sudden change determination signal Cf is Low level (non-rapid change), the time during which the squeezing detection signal Nd is High level (squeezing detection time) is measured, and Cf = High level (feed speed sudden change period Tcf) ) Is not measured. Here, during the feed speed rapid change period Tcf, the automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time. As a result, it is possible to suppress the automatic correction of the squeezing detection reference value from malfunctioning during the feed speed sudden change period Tcf and causing the value of the squeezing detection reference value signal Vtn to deviate from the appropriate value.
2) When the squeezing detection time is less than or equal to the lower limit time of the predetermined time setting range, 1 is subtracted from the counter value, and when the squeezing detection time is greater than or equal to the upper limit time of the time setting range, the counter value is set. Add one.
3) When the counter value reaches a negative reference value that is a predetermined negative value, a predetermined decrease value is output as the correction amount signal Δud, and the counter value is reset to 0 so that the counter value is a predetermined positive value. When the positive reference value is reached, a predetermined increase value is output as the correction amount signal Δud and the counter value is reset to zero.
4) During welding, the above processes 1) to 3) are repeated.

  The above counter value is reset to 0 at the start of welding. The time setting range is set to 50 to 1000 μs, for example. In this case, the lower limit time of the time setting range is 50 μs, and the upper limit time is 1000 μs. The negative reference value is set to a negative value, for example, in the range of about −5 to −20. Further, the positive reference value is set to a positive value, for example, in the range of about +5 to +20. These set values are set according to the magnitude of the fluctuation of the constriction occurrence state. The absolute values of the negative reference value and the positive reference value are not necessarily the same value. The decrease value is set to a negative value, and the absolute value thereof is set to a range of about 10 to 30% of an initial value Vtn0 of a squeezing detection reference value described later, for example. The increase value is set to a positive value, for example, set in a range of about 10 to 30% of the initial value Vtn0 of the squeezing detection reference value. Since these set values correspond to the gains of the feedback system, the set values are set in consideration of the transient response and steady stability in the corrected state of the squeezing detection reference value signal Vtn.

  The squeezing detection reference value automatic correction circuit VTN receives the above correction amount signal Δud, calculates Vtn = Vtn0 + ΣΔud, and outputs a squeezing detection reference value signal Vtn. Here, Vtn0 is an initial value of the squeezing detection reference value. The initial value Vtn0 is set so that the squeezing detection sensitivity is lowered so that the welding state does not become unstable until the squeezing detection reference value signal Vtn is optimized. Further, Δud is added every time the correction amount signal Δud is input. By this circuit, the value of the squeezing detection reference value signal Vtn is automatically corrected and optimized so that the squeezing detection time falls within the above time setting range.

  The squeezing detection circuit ND receives the squeezing detection reference value signal Vtn, the voltage detection signal Vd, the current detection signal Id and the short circuit / arc discrimination signal Sd, and the short circuit / arc discrimination signal Sd is at a high level ( When the voltage rise value of the voltage detection signal Vd at the time of short circuit reaches the value of the squeezing detection reference value signal Vtn, it is determined that the squeezing has been formed and becomes High level, and the short circuit / arc determination signal Sd is at the Low level (arc). The squeezing detection signal Nd which becomes Low level at the time of changing to () is output. Here, the squeezing detection signal Nd may be changed to the High level when the differential value of the voltage detection signal Vd during the short circuit period reaches the value of the squeezing detection reference value signal Vtn corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the value of the squeezing detection reference value signal Vtn corresponding thereto. The constriction detection signal Nd may be changed to a high level.

  The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as input, and outputs a current comparison signal Cm that is at a high level when Id <Ilr and is at a low level when Id ≧ Ilr. Output. The drive circuit DR receives the current comparison signal Cm and the above-described squeezing detection signal Nd, changes to a low level when the squeezing detection signal Nd changes to a high level, and then changes to a high level when the current comparison signal Cm changes to a high level. The drive signal Dr that changes in level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. Therefore, the welding current Iw for energizing the short-circuit load decreases rapidly. . When the sharply decreased welding current Iw value decreases to the low level current setting signal Ilr value, the drive signal Dr becomes a high level and the transistor TR is turned on. Return to the state.

The current control setting circuit ICR receives the short-circuit / arc discrimination signal Sd, the low-level current setting signal Ilr, and the squeezing detection signal Nd as input, and outputs a current control setting signal Icr.
1) A predetermined initial current set value is output as the current control setting signal Icr during a predetermined initial period from the time when the short circuit / arc determination signal Sd changes to the high level (short circuit).
2) Thereafter, the value of the current control setting signal Icr is increased from the initial current setting value to a predetermined peak setting value at a predetermined short-circuit slope, and the value is maintained.
3) When the squeezing detection signal Nd changes to the high level (squeezing detection), the value of the current control setting signal Icr is switched to the value of the low level current setting signal Ilr and maintained.
4) When the short circuit / arc determination signal Sd changes to the low level (arc), the current control setting signal Icr is increased to a predetermined high level current setting value at a predetermined arc inclination, and the value is maintained.

  The off-delay circuit TDS receives the short-circuit / arc discrimination signal Sd as described above, and outputs a delay signal Tds by delaying off the time when this signal changes from the high level to the low level by a predetermined delay time. Accordingly, the delay signal Tds is a signal that becomes a high level during the short circuit period, and is turned off to a low level after being delayed for a delay time after the arc is regenerated. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage during the arc period. The current error amplification circuit EI amplifies an error between the current control setting signal Icr (+) and the current detection signal Id (−), and outputs a current error amplification signal Ei. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr (+) and the voltage detection signal Vd (−) and outputs a voltage error amplification signal Ev. The control switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev and the delay signal Tds as inputs, and the delay signal Tds is at a high level (the arc is regenerated from the start of the short circuit and the delay time is increased). The current error amplification signal Ei is output as the error amplification signal Ea during the period until the time elapses, and the voltage error amplification signal Ev is output as the error amplification signal Ea when at the low level (arc). With this circuit, constant current control is performed during the short circuit period + delay period, and constant voltage control is performed during the other arc periods.

The processing of the correction amount calculation circuit DUD described above may be performed as follows.
1) When the feed speed sudden change determination signal Cf is Low level (non-rapid change), the time during which the squeezing detection signal Nd is High level (squeezing detection time) is measured, and Cf = High level (feed speed sudden change period Tcf) ) Is not measured. Here, during the feed speed rapid change period Tcf, the automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time.
2) An error between the squeezing detection time and a predetermined time setting range is amplified and output as a correction amount signal Δud.
3) During the welding, the above processes 1) to 2) are repeated.
Here, the time setting range is a time setting value, and is set to 500 μs, for example. As a definition of the term, a time set value is one form of a time set range. That is, the lower limit time and the upper limit time of the time setting range are the same value.

Further, the processing of the correction amount calculation circuit DUD described above may be performed as follows.
1) When the feed speed sudden change determination signal Cf is at the Low level (non-rapid change), the time during which the squeezing detection signal Nd is at the High level (squeezing detection time) is measured and stored, and Cf = High level (the feed speed is suddenly changed). During the period Tcf), no measurement is performed. Here, during the feed speed rapid change period Tcf, the automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time.
2) More than a plus reference value in which the number of the squeezing detection times corresponding to a plurality of predetermined numbers from the current stored time is equal to or greater than a predetermined positive value in which the number is equal to or less than a lower limit time of a predetermined time setting range In this case, a predetermined decrease value is output as the correction amount signal Δud, and when the number of stored squeezing detection times is not less than the upper limit time of the time setting range is not less than the plus reference value, it is determined in advance. The increase value is output as the correction amount signal Δud.
3) During the welding, the above processes 1) to 2) are repeated.
Here, the time setting range, the negative reference value, the positive reference value, the increase value, and the decrease value are set to the above-described values. Said predetermined number is set in the range of about 5-30.

  FIG. 2 is a timing chart showing the squeezing detection control method according to the embodiment of the present invention. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the squeezing detection signal Nd, (D) ) Shows the time change of the drive signal Dr, FIG. 9E shows the time change of the delay signal Tds, and FIG. 9F shows the time change of the current control setting signal Icr. In the figure, the operation or prohibition of the control for automatically correcting the value of the squeezing detection reference value signal Vtn to an appropriate value is the state of the feed speed sudden change determination signal Cf (whether the change rate of the feed speed is larger than the reference value). Or small state). Hereinafter, a description will be given with reference to FIG.

(1) Operation from occurrence of short circuit at time t1 to necking detection time at time t2 When the welding wire comes into contact with the base material at time t1, a short circuit is established, and as shown in FIG. It decreases rapidly to a short-circuit voltage value of about. It is determined that the welding voltage Vw has become less than the short circuit / arc determination value Vta, and the delay signal Tds changes from the Low level to the High level as shown in FIG. In response to this, as shown in FIG. 5F, the current control setting signal Icr changes from a predetermined high level current setting value to a predetermined initial current setting value which is a small value at time t1. During the predetermined initial period from the time t1 to t11, the initial current set value is set. During the period from the time t11 to t12, the voltage rises with a predetermined slope at the time of short circuit, and during the period from the time t12 to t2, the predetermined peak is set. Set value. Since the constant current control is performed as described above during the short circuit period, the welding current Iw is controlled to a value corresponding to the current control setting signal Icr. For this reason, as shown in FIG. 6A, the welding current Iw rapidly decreases from the welding current in the arc period at time t1, and becomes an initial current value during the initial period from time t1 to t11, and from time t11 to t12. During the period, it rises with a slope at the time of short circuit, and reaches a peak value during the period from time t12 to t2. As shown in FIG. 5B, the welding voltage Vw increases rapidly from around time t12 when the welding current Iw reaches its peak value. This is because constriction occurs in the droplets. As shown in FIG. 6C, the squeezing detection signal Nd is at a high level during a period from time t2 to t3, which will be described later, and is at a low level during other periods. The time from the time t2 to the time t3 when the squeezing detection signal Nd becomes High level becomes the squeezing detection time Tn. As shown in FIG. 4D, the drive signal Dr is at a low level during a period from time t2 to t21, which will be described later, and is at a high level during other periods. Therefore, during the period before time t2 in the figure, the drive signal Dr is at a high level and the transistor TR in FIG. 1 is turned on, so that the current reducing resistor R is short-circuited and the normal consumable electrode arc welding power source is connected. It becomes the same state. The initial period is set to about 1 ms, the initial current value is set to about 50 A, the short-circuit slope is set to about 100 to 300 A / ms, and the peak value is set to about 300 to 400 A.

(2) Operation during Neck Detection Time Tn from Neck Detection Time at Time t2 to Arc Reoccurrence Time at Time t3 At time t2, as shown in FIG. When the constriction is detected when the voltage increase value ΔV from the voltage value becomes equal to the value of the constriction detection reference value signal Vtn, the constriction detection signal Nd changes to the high level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr becomes the low level, so that the transistor TR in FIG. 1 is turned off and the current reducing resistor R is inserted into the energization path. At the same time, the current control setting signal Icr decreases to the value of the low level current setting signal Ilr, as shown in FIG. For this reason, as shown in FIG. 5A, the welding current Iw rapidly decreases from the peak value to the low level current value Il. When the welding current Iw decreases to the low level current value Il at time t21, as shown in FIG. 4D, the drive signal Dr returns to the high level, so that the transistor TR in FIG. The device R is short-circuited. As shown in FIG. 6A, the welding current Iw maintains the low level current value Il until the arc is regenerated at time t3 because the current setting signal Ir remains the low level current setting signal Ilr. Therefore, the transistor TR is turned off only during a period from when the constriction is detected at time t2 until the welding current Iw decreases to the low level current value Il at time t21. As shown in FIG. 5B, the welding voltage Vw increases rapidly after once decreasing from time t2. The low level current value Il is set to about 30A. The value of the squeezing detection reference value signal Vtn sets the squeezing detection sensitivity. As described above, the value of the squeezing detection reference value signal Vtn is automatically corrected so that the squeezing detection time Tn falls within the time setting range. The automatic correction method is as described above with reference to FIG. In this automatic correction, as described above, the operation is temporarily prohibited during the feed speed sudden change period Tcf in which the feed speed sudden change determination signal Cf is at the High level. However, the operation of the timing chart in the figure is the same regardless of whether or not it is during the feeding speed sudden change period Tcf.

(3) Operation from time of arc reoccurrence at time t3 to end of delay period Td at time t4 When arc is regenerated at time t3, the value of the welding voltage Vw is short-circuited / The arc discrimination value Vta or more. In response to this, as shown in FIG. 5F, the value of the current control setting signal Icr rises from the value of the low level current setting signal Ilr at a predetermined arc slope, and the above described high level current setting When the value is reached, the value is maintained. As shown in FIG. 5E, the delay signal Tds remains at the high level until time t4 when a predetermined delay period Td elapses after the arc is regenerated at time t3. Therefore, since the welding power source is controlled at a constant current until time t4, as shown in FIG. 4A, the welding current Iw increases at the arc slope from time t3 and reaches that value when it reaches a high level current value. Is maintained until time t4. As shown in FIG. 5B, the welding voltage Vw is in a high level voltage value during the delay period Td between times t3 and t4. The delay period Td is set to about 2 ms. As shown in FIG. 5C, the squeezing detection signal Nd changes to the low level because the arc is regenerated at time t3.

(4) Operation in the arc period from the end of the delay period Td at time t4 until the next short-circuit occurrence at time t5 As shown in FIG. 5E, the delay signal Tds changes to the low level. As a result, the welding power source is switched from constant current control to constant voltage control. For this reason, as shown in FIG. 5A, the welding current Iw gradually decreases from the high level current value. Similarly, as shown in FIG. 3B, the welding voltage Vw gradually decreases from the high level voltage value.

  Thus, in the squeezing detection control, when squeezing is detected at time t2, the welding current Iw is rapidly reduced by inserting a current reducing resistor in the energizing path, and the current value at the time when the arc is regenerated at time t3 is reduced. The value can be controlled. For this reason, the amount of spatter generated can be greatly reduced.

  FIG. 3 is a timing chart illustrating the feed speed variable control method according to the embodiment of the present invention when the rate of change of the feed speed is greater than or equal to a reference value. FIG. 4A shows the change over time of the distance Lw between the power feed tip and the base material, FIG. 4B shows the change over time of the feeding speed Fw, and FIG. 4C shows the change over time of the welding current smoothing signal Iav. FIG. 4D shows the change over time of the feed speed sudden change determination signal Cf. The figure shows the feed speed Fw and welding current smoothing signal Iav when the distance Lw between the power supply tip and the base material becomes longer in steps from L1 (mm) to L2 (mm) at time t1. Transient response is shown. Hereinafter, a description will be given with reference to FIG.

  When the distance between the welding torch and the base material is increased at time t1 during welding, the distance Lw between the power feed tip and the base material is increased stepwise from L1 to L2, as shown in FIG. For this reason, as shown in FIG. 3C, the value of the welding current smoothing signal Iav decreases with an inclination from the time t1. In response to this, an attempt is made to maintain the value of the welding current smoothing signal Iav at a constant value by the feed speed variable control, and as shown in FIG. Become. The value of the welding current smoothing signal Iav decreases from time t1, reverses from decrease to increase at time t2, and returns to the value before time t1 at time t3, as shown in FIG. The feeding speed Fw increases from time t1, continues to increase at time t2, and converges to a faster value at time t3 than before time t1. The time from time t1 to t3 is the transient response time T1 (second). For example, T1 = about 100 ms.

  As shown in FIG. 4B, the rate of change of the feeding speed Fw is equal to or higher than the reference value during the period from time t1 to time t3. Therefore, as shown in FIG. Becomes High level during this period. That is, the period from time t1 to t3 is the feed speed sudden change period Tcf. As described above, during this feed speed rapid change period Tcf, automatic correction of the squeezing detection reference value is prohibited to prevent malfunction. Further, as described above, the timing at which the feed speed sudden change determination signal Cf changes from the high level to the low level may be off-delayed for a predetermined period.

  During the feed rate sudden change period, several short circuits occur. For these short circuits, as described above, the automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time. During the rapid change of the feeding speed, the formation state of the droplet constriction varies greatly. In such a state, the automatic correction of the squeezing detection reference value malfunctions, and the squeezing detection reference value deviates greatly from the appropriate value, so that a false detection of squeezing occurs and the welding state becomes unstable. On the other hand, in the present embodiment, the automatic correction of the squeezing detection reference value is prohibited during the rapid feed rate change period, so that the welding state does not become unstable. At this time, since the time ratio occupied by the feed rate sudden change period in the entire welding period is usually very small, there is almost no influence on the transient response and the steady stability when the necking detection reference value is automatically corrected. As a result, the welding state can be maintained in a stable state even when the squeezing detection control accompanied by the automatic correction of the squeezing detection reference value and the feed speed variable control are operated together.

  The rate of change of the feeding speed Fw varies depending on the vertical movement speed and movement width of the welding torch, the transient response of the feeding speed variable control, and the like. The reference value for discriminating the feed rate sudden change period is set to the upper limit value of the rate of change of the feed rate Fw that does not cause a malfunction of automatic correction even when automatic correction of the squeezing detection reference value is operating. This reference value is preferably optimized according to the material, diameter, welding method, type of shielding gas, and the like of the welding wire.

  FIG. 4 is a timing chart showing the feed speed variable control method according to the embodiment of the present invention when the rate of change of the feed speed is less than the reference value. FIG. 4A shows the change over time of the distance Lw between the power feed tip and the base material, FIG. 4B shows the change over time of the feeding speed Fw, and FIG. 4C shows the change over time of the welding current smoothing signal Iav. FIG. 4D shows the change over time of the feed speed sudden change determination signal Cf. The figure shows the feed speed Fw and welding current smoothing signal when the distance Lw between the power supply tip and the base material gradually increases from L1 (mm) to L2 (mm) from time t1 to time t2 during welding. It shows the transient response of Iav. This figure corresponds to FIG. 3 described above. Hereinafter, a description will be given with reference to FIG.

  When the distance between the welding torch and the base material is increased in the period from time t1 to time t2 during welding, the distance Lw between the power feed tip and the base material gradually increases from L1 to L2, as shown in FIG. . The period of time t1 to t2 is, for example, 500 ms. In this way, since the distance Lw between the power feed tip and the base material is gradually increased, the value of the welding current smoothing signal Iav is slightly reduced from time t1 as shown in FIG. At time t2, the value returns to the value before time t1. In response to this, an attempt is made to maintain the value of the welding current smoothing signal Iav at a constant value by feed rate variable control, and as shown in FIG. 5B, the feed rate Fw increases from time t1, and at time t2. It converges to a faster value than before time t1. The time from time t1 to t2 is the transient response time T1 (second).

  As shown in FIG. 6B, the rate of change of the feeding speed Fw is less than the reference value during the period from the time t1 to the time t2, so as shown in FIG. Becomes Low level for all periods. That is, in the figure, there is no feed speed rapid change period Tcf. As described above, the automatic correction of the squeezing detection reference value is operated during a period other than the feed speed rapid change period Tcf.

  During the period in which the feeding speed changes from time t1 to t2, a short circuit occurs ten times or more. For these short circuits, automatic correction of the squeezing detection reference value is operating. Even if the squeezing detection control with automatic correction of the squeezing detection reference value and the feed speed variable control are operated together, the automatic correction of the squeezing detection reference value malfunctions because the rate of change of the feeding speed is less than the reference value. Therefore, the welding state does not become unstable.

  According to the above-described embodiment, the rate of change of the feed rate is detected, and the necking detection reference value is automatically corrected during the feed rate sudden change period in which the rate of change of the feed rate is equal to or greater than a predetermined reference value. Ban. Thus, in the present embodiment, automatic correction of the squeezing detection reference value is prohibited by not measuring the squeezing detection time for a short circuit that occurs during the rapid change in the feeding speed. During the rapid change of the feeding speed, the formation state of the droplet constriction varies greatly. In such a state, the automatic correction of the squeezing detection reference value malfunctions, and the squeezing detection reference value deviates greatly from the appropriate value, so that a false detection of squeezing occurs and the welding state becomes unstable. On the other hand, in the present embodiment, the automatic correction of the squeezing detection reference value is prohibited during the rapid feed rate change period, so that the welding state does not become unstable. At this time, since the time ratio occupied by the feed rate sudden change period in the entire welding period is usually very small, there is almost no influence on the transient response and the steady stability when the necking detection reference value is automatically corrected. As a result, the welding state can be maintained in a stable state even when the squeezing detection control accompanied by the automatic correction of the squeezing detection reference value and the feed speed variable control are operated together.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll CF Feeding speed sudden change discrimination circuit Cf Feeding speed sudden change judgment signal CM Current comparison circuit Cm Current comparison signal DF Feeding speed change rate detection circuit Df Feeding speed change Rate detection signal DR Drive circuit Dr Drive signal DUD Correction amount calculation circuit Ea Error amplification signal EF Feed error amplification circuit Ef Feed error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fr0 initial value Fw feed speed IAV current smoothing circuit Iav welding current smoothing signal ICR current control setting circuit Icr current control setting signal ID current Detection circuit Id Current detection signal Il Low level current value ILR Low level current setting circuit Ilr Low level current setting signal IR Current Constant circuit Ir Current setting signal Iw Welding current Lw Distance between feed tip and base material ND Constriction detection circuit Nd Constriction detection signal PM Power supply main circuit R Current drop resistor SD Short circuit / arc determination circuit Sd Short circuit / arc determination signal SW Control switching circuit T1 Transient response time Tcf Feeding speed sudden change period Td Delay period TDS Off delay circuit Tds Delay signal Tn Neck detection time TR Transistor VD Voltage detection circuit Vd Voltage detection signal VR Voltage setting circuit Vr Voltage setting signal Vta Short circuit / arc discriminating value VTN Detection reference value automatic correction circuit Vtn Neck detection reference value signal Vtn0 Initial value Vw Welding voltage WM Feeding motor Δud Correction amount signal ΔV Voltage increase value

Claims (3)

Detects the constriction of droplets, which is a precursor to the occurrence of an arc again from a short circuit, when the voltage or resistance change between the welding wire and the base metal reaches the constriction detection reference value. Then, the welding current applied to the short-circuit load is reduced to regenerate the arc, and the squeezing detection is performed so that the squeezing detection time from the squeezing detection time to the reoccurrence time of the arc is within a predetermined time setting range. Necking detection control for welding with automatic correction of the reference value is performed, the smoothing value of the welding current is detected, and the welding wire feed speed is adjusted so that the welding current smoothing value and the preset current setting value are equal. In the consumable electrode arc welding control method for performing feedback control and performing feed rate variable control welding,
Detecting the rate of change of the feed rate, and prohibiting automatic correction of the squeezing detection reference value during a feed rate sudden change period in which the rate of change of the feed rate is equal to or greater than a predetermined reference value;
A consumable electrode arc welding control method. Maintaining the prohibition of automatic correction of the squeezing detection reference value until a predetermined period elapses from the time when the feeding speed sudden change period ends.
The consumable electrode arc welding control method according to claim 1. The automatic correction of the constriction detection reference value is
(1) detecting the constriction detection time for each short circuit;
(2) When the squeezing detection time is less than or equal to the lower limit time of the time setting range, 1 is subtracted from the counter value. When the squeezing detection time is greater than or equal to the upper limit time of the time setting range, 1 is added to the counter value. Adding steps,
(3) When the counter value reaches a negative reference value that is a predetermined negative value, the squeezing detection reference value is decreased by a predetermined decrease value, and the counter value is reset to 0. When the positive reference value which is a predetermined positive value is reached, the squeezing detection reference value is increased by a predetermined increase value and the counter value is reset to 0.
The consumable electrode arc welding control method according to claim 1 or 2.

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