JP2016059957A - Arc-welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method that repeats forward feeding and backward feeding of a welding wire periodically, which can improve stability of a welding state.SOLUTION: In an arc-welding control method that repeats periodically a forward feeding period and a backward feeding period at a feeding speed Fw for a welding wire so as to generate a short-circuit period and an arc period, and conducts short-circuit currents Iw during the short-circuit period, when a phase of the feeding speed Fw reaches a predetermined reference phase during the short-circuit period (at t41) a peak value of the short-circuit currents Iw is increased from Ip1 to Ip2. Therefore, when a short-circuit release phase is varied by disturbance, the peak value of the short-circuit currents Iw is increased to promote release of the short-circuit. This can suppress variation of the short-circuit release phase so that stability of a welding state can be improved.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an arc welding control method for generating a short circuit period and an arc period by periodically repeating a forward feed period and a reverse feed period of a feeding speed of a welding wire and energizing a short circuit current during the short circuit period. It is.

  In general consumable electrode arc welding, a welding wire that is a consumable electrode is fed at a constant speed, and an arc is generated between the welding wire and a base material to perform welding. In the consumable electrode type arc welding, the welding wire and the base material are often in a welding state in which a short circuit period and an arc period are alternately repeated.

  By the way, in order to further improve the welding quality, a method has been proposed in which welding is performed by periodically repeating forward and reverse feeding of the welding wire. Hereinafter, this welding method will be described.

  FIG. 4 is a waveform diagram in a welding method in which a normal feeding period and a reverse feeding period of the welding wire feeding speed are periodically repeated. FIG. 4A shows the waveform of the feeding speed Fw, FIG. 4B shows the waveform of the welding current Iw, and FIG. 4C shows the waveform of the welding voltage Vw. Hereinafter, the operation will be described with reference to FIG.

  As shown in FIG. 5A, the feed speed Fw is a forward feed period above 0 and a reverse feed period below. Forward feeding is feeding in the direction in which the welding wire is brought closer to the base material, and reverse feeding is feeding in a direction away from the base material. The feeding speed Fw changes in a sine wave shape and has a waveform shifted to the forward feeding side. For this reason, the average value of the feeding speed Fw is a positive value, and the welding wire is fed forward on average.

  As shown in FIG. 6A, the feeding speed Fw is 0 at time t1, the period from time t1 to t2 is a normal feeding acceleration period, the maximum value of normal feeding at time t2, and the time t2 The period of t3 is a forward feed deceleration period, becomes 0 at time t3, the period of time t3 to t4 is a reverse feed acceleration period, becomes the maximum value of reverse feed at time t4, and the period of time t4 to t5 is a reverse feed deceleration period. It becomes. The feeding speed Fw is repeated with time t1 to t5 as one cycle.

  Short-circuiting between the welding wire and the base material often occurs before and after the maximum normal feed value at time t2. In the figure, the case occurs at time t21 during the forward feed deceleration period after the forward feed maximum value. When a short circuit occurs at time t21, the welding voltage Vw rapidly decreases to a short circuit voltage value of several V as shown in FIG. 10C, and the welding current Iw also has a small current value as shown in FIG. Decrease to the initial current value. In the following description, the welding current Iw during the short circuit period will be described as a short circuit current. After that, the short-circuit current increases at a predetermined rate of increase S [A / ms] and maintains that value when it reaches a predetermined peak value Ip.

  As shown in FIG. 5A, the feeding speed Fw is in the reverse feed period from time t3, so the welding wire is fed backward. The short circuit is released by the reverse feed and the pinch force caused by the short circuit current, and the arc is regenerated at time t31. The reoccurrence of the arc often occurs before and after the maximum reverse feed value at time 4. In the figure, the case occurs at time t31 during the reverse acceleration period before the reverse maximum value.

  When the arc is regenerated at time t31, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. As shown in FIG. 5B, the short-circuit current rapidly decreases from a time about several hundred μs before the time t31 by the control of detecting the constriction of the droplet, which is a precursor of the arc re-occurrence, and at the time t31. When the arc is regenerated, the current value is small. The detection of the necking is performed by detecting that when the necking is formed in the droplet, the current path becomes narrow and the resistance value or the welding voltage value between the welding wire and the base material increases.

  As shown in FIG. 5A, the feeding speed Fw is reversely sent from time t31 to time t5. During this period, the arc length becomes longer. During the period from time t31 to t5, as shown in FIG. 5B, the welding current Iw increases at a predetermined arc rise rate, and when the predetermined first welding current value is reached, the value is regenerated. A predetermined period from the time (time t31) is maintained. Thereafter, a second welding current that is smaller than the first welding current is applied until time t61 when the next short circuit occurs.

  As shown in FIG. 5A, the feeding speed Fw is a normal feeding period from time t5, and reaches the maximum value of normal feeding at time t6. In the figure, the next short circuit occurs at time t61. During the period from time t5 to t61, the welding voltage Vw gradually decreases as shown in FIG. 5C, and the welding current Iw also gradually decreases as shown in FIG.

  As described above, the cycle of the short circuit and the arc substantially matches the cycle of the forward feed and the reverse feed of the feed speed. That is, in this welding method, the cycle between the short circuit and the arc can be set to a desired value by setting the cycle between the forward feed and the reverse feed of the feed speed. For this reason, if this welding method is carried out, it becomes possible to suppress the variation in the cycle between the short circuit and the arc and make it substantially constant, and perform welding with a small amount of spatter generation and a good bead appearance. Can do.

  However, in a welding method that repeats forward and reverse feeding speeds, due to disturbances such as the distance between the feeding tip and the base metal, irregular movement of the molten pool, and changes in the welding position, the short-circuit period to the arc period There is a case where the timing of the transition and the transition from the arc period to the short-circuit period does not occur at the appropriate timing described above. If it becomes like this, the period of a short circuit and an arc and the period of forward transmission and reverse transmission will become out of synchronization, and the period of a short circuit and an arc will vary. A method for returning the synchronization shift state to the original synchronization state is disclosed in Patent Document 1.

  In the invention of Patent Document 1, when a short-circuit does not occur before the feeding speed reaches a predetermined feeding speed during normal feeding of the welding wire and deceleration of the feeding speed, the periodic change is stopped. The feed speed is controlled to be constant at the first feed speed, and if a short circuit occurs during normal feed at the first feed speed, deceleration is started from the first feed speed and the periodic change is resumed. Welding. As a result, the synchronization shift state is returned to the synchronization state.

Japanese Patent No. 4807474

  In the invention of Patent Document 1, when a short circuit does not occur at an appropriate timing, the feeding speed is switched to a constant feed speed, and when a short circuit occurs, the feeding speed is returned to the original periodic change. However, in this control, the cycle of the feeding speed is changed by itself, and the welding state may fall into an unstable state.

  Therefore, in the present invention, the period of the short-circuit and the arc and the period of the forward and reverse feeding speeds are in a synchronized deviation state while keeping the period of the feeding speed forward and backward feeding constant. It is an object of the present invention to provide an arc welding control method capable of suppressing the occurrence of a stable welding.

In order to solve the above-described problems, the invention of claim 1
In the arc welding control method of generating a short circuit period and an arc period by periodically repeating a forward feed period and a reverse feed period of the feeding speed of the welding wire, and supplying a short circuit current during the short circuit period,
When the phase of the feeding speed reaches a predetermined reference phase during the short circuit period, the peak value of the short circuit current is increased.
An arc welding control method characterized by the above.

The invention of claim 2 detects the feeding speed when the phase of the feeding speed reaches the reference phase, and increases the peak value of the short-circuit current according to the detected feeding speed. Change
The arc welding control method according to claim 1, wherein:

  According to the present invention, when the short-circuit period continues even when the phase of the feed speed reaches the reference phase, the peak value of the short-circuit current can be increased to facilitate the release of the short-circuit. An increase in the period can be suppressed. For this reason, in the present invention, the cycle of the short circuit and the arc and the cycle of the forward feed and the reverse feed of the feed rate are synchronized with each other while keeping the cycle of the feed feed forward and reverse feed constant. Stable welding can be performed while suppressing the state.

It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 1 for demonstrating the arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 2 of this invention. In a prior art, it is a wave form diagram in the welding method which repeats forward feeding and reverse feeding of feed speed periodically.

  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 for carrying out an arc welding control method according to Embodiment 1 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 into direct current, a reactor that smoothes the rectified direct current, and modulation that performs pulse width modulation control using the error amplification signal Ea as an input. The circuit includes an inverter drive circuit that receives a pulse width modulation control signal as input and drives a switching element of the inverter circuit.

  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). When the current reducing resistor R is inserted into the current path, the energy stored in the 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 feed motor WM receives a feed control signal Fc described later, and feeds the welding wire 1 at a feed speed Fw by periodically repeating forward feed and reverse feed. As this feed motor WM, a motor having a fast transient response is used. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

  The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd.

  The short-circuit determination circuit SD receives the welding voltage detection signal Vd as described above, and when this value is less than a predetermined short-circuit / arc determination value (set to about 10 V), determines that it is in the short-circuit period and becomes High level. In the above case, it is determined that the arc period is in effect, and a short-circuit determination signal Sd that goes low is output.

  The feed rate setting circuit FR outputs a feed rate setting signal Fr having a predetermined pattern in which the forward feed and the reverse feed are periodically repeated, as will be described in detail with reference to FIG.

  The feed control circuit FC receives the feed speed setting signal Fr and inputs a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the set value to the feed motor WM. Output to.

  The reference phase setting circuit BR outputs a predetermined reference phase setting signal Br. The reference phase excess discrimination circuit BD receives the reference phase setting signal Br, the feed speed setting signal Fr and the short-circuit discrimination signal Sd as inputs, and feeds when the short-circuit discrimination signal Sd is at a high level (short-circuit). When the phase Ba of the speed setting signal Fr reaches the value of the reference phase setting signal Br, it is set to High level, and when the short circuit determination signal Sd becomes Low level (arc), a reference phase excess determination signal Bd that is reset to Low level is output. To do.

  The first welding current setting circuit IWR1 outputs a predetermined first welding current setting signal Iwr1. The first welding current conduction period setting circuit TWR1 outputs a predetermined first welding current conduction period setting signal Twr1.

  The increase rate setting circuit SR outputs a predetermined increase rate setting signal Sr. The peak value setting circuit IPR receives the above reference phase excess discrimination signal Bd, and when the reference phase excess discrimination signal Bd = Low level, it becomes a predetermined first peak value Ip1, and when Bd = High level, it is predetermined. The peak value setting signal Ipr which becomes the second peak value Ip2 is output. Here, Ip1 <Ip2.

  The constriction detection circuit ND receives the short-circuit determination signal Sd, the welding voltage detection signal Vd, and the welding current detection signal Id, and detects the welding voltage when the short-circuit determination signal Sd is at a high level (short-circuit period). When the voltage rise value of the signal Vd reaches a predetermined squeezing detection reference value, it is determined that a squeezing has been formed and becomes a high level, and when the short-circuit determination signal Sd changes to a low level (arc period), it becomes a low level. The squeezing detection signal Nd is output. Alternatively, the squeezing detection signal Nd may be changed to a high level when the differential value of the welding voltage detection signal Vd during the short circuit period reaches the squeezing detection reference value corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the welding voltage detection signal Vd by the value of the welding current detection signal Id, and when the differential value of the resistance value reaches the corresponding squeezing detection reference value, the squeezing occurs. The 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 welding current detection signal Id as described above, and becomes a high level when Id <Ilr, and a low level current comparison signal Cm when Id ≧ Ilr. Is output.

  The drive circuit DR receives the current comparison signal Cm and the above-described squeezing detection signal Nd, changes to a low level when the squeezing detection signal Nd changes to a high level, and then changes to a high level when the current comparison signal Cm changes to a high level. The drive signal Dr that changes in level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. Therefore, the 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 includes the short circuit determination signal Sd, the low level current setting signal Ilr, the squeezing detection signal Nd, the first welding current setting signal Iwr1, the increase rate setting signal Sr, and the The following processing is performed with the peak value setting signal Ipr as an input, and the current control setting signal Icr is output.
1) A predetermined initial current set value is output as the current control setting signal Icr during a predetermined initial period from the time when the short circuit determination signal Sd changes to the high level (short circuit).
2) Thereafter, the value of the current control setting signal Icr is increased from the initial current setting value to the value of the peak value setting signal Ipr at an increase rate determined by the increase rate setting signal Sr, and the value is maintained. (The value of the peak value setting signal Ipr becomes the first peak value Ip1 until the phase of the feed speed reaches the reference phase, and after that reaches the second peak value Ip2.)
3) When the squeezing detection signal Nd changes to the high level, the value of the current control setting signal Icr is switched to the value of the low level current setting signal Ilr and maintained.
4) When the short circuit determination signal Sd changes to the low level (arc), the current control setting signal Icr is increased to the value of the first welding current setting signal Iwr1 at a predetermined rate of increase during arcing, and this value is maintained.

  The off-delay circuit TDS receives the short circuit determination signal Sd and the first welding current energization period setting signal Twr1 as input, and sets the first welding current energization period when the short circuit determination signal Sd changes from the High level to the Low level. The delayed signal Tds is output with an off-delay for the period of the signal Twr1. Therefore, this delay signal Tds is a signal that becomes a high level in the short circuit period, and that is off-delayed for a period of the first welding current energization period setting signal Twr1 after the arc is regenerated and becomes a low level.

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

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage during the arc period. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr (+) and the welding 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 first welding is performed). Current error amplification signal Ei is output as error amplification signal Ea when the current energization period setting signal Twr1 elapses), and voltage error amplification signal Ev is error amplification signal Ea when the current level is low (arc). Output as. With this circuit, constant current control is performed during the short-circuit period + first welding current energization period, and constant voltage control is performed during the other arc periods.

  FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 for explaining the arc welding control method according to the first embodiment of the present invention. The figure (A) shows the time change of the feeding speed Fw of the welding wire 1, the figure (B) shows the time change of the welding current Iw, the figure (C) shows the time change of the welding voltage Vw, FIG. 4D shows the time change of the squeezing detection signal Nd, FIG. 4E shows the time change of the drive signal Dr, FIG. 4F shows the time change of the delay signal Tds, and FIG. ) Shows a time change of the current control setting signal Icr, and FIG. 9H shows a time change of the reference phase excess determination signal Bd. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5A, when the feeding speed Fw is a positive value above 0, it indicates that the welding wire is being fed forward, and when the feeding speed Fw is a negative value below 0, Indicates that it is being sent back. Since the feeding speed Fw shown in FIG. 5A is set by a feeding speed setting signal Fr (not shown), both waveforms are similar waveforms. Further, the feeding speed Fw shown in FIG. 4A has the same waveform as the feeding speed Fw shown in FIG.

  As shown in FIG. 6A, the feeding speed Fw is 0 at time t1, the period from time t1 to t2 is a normal feeding acceleration period, the maximum value of normal feeding at time t2, and the time t2 The period of t3 is a forward feed deceleration period, becomes 0 at time t3, the period of time t3 to t4 is a reverse feed acceleration period, becomes the maximum value of reverse feed at time t4, and the period of time t4 to t5 is a reverse feed deceleration period. It becomes. Therefore, the feeding speed Fw has a waveform that repeats the period from time t1 to t5 as one cycle. This one period is a constant value during welding and does not change. The phase of the feeding speed Fw is 0 ° at time t1, 90 ° at time t2, 180 ° at time t3, 270 ° at time t4, and 360 ° (0 °) at time t5. Although it changes in a sine wave shape in the figure, it may be changed in a triangular wave shape or a trapezoidal wave shape. For example, the normal transmission period from time t1 to t3 is 5.4 ms, the reverse transmission period from time t3 to t5 is 4.6 ms, and one period is 10 ms. Further, the maximum value for forward feed is 50 m / min, and the maximum value for reverse feed is −40 m / min. At this time, the average value of the feeding speed Fw is about +4 m / min, and the average welding current value is about 150A.

Here, a method of calculating the feeding speed phase Ba (°) will be described. The normal transmission period from time t1 to t3 is Ts (ms), and the reverse transmission period from time t3 to t5 is Tr (ms). The elapsed time Ta (ms) from the time t1, which is the start time of the cycle, is measured, and the feeding speed phase Ba can be calculated by the following equation.
When Ta ≦ Ts, Ba = (Ta / Ts) × 180
When Ta> Ts, Ba = ((Ta−Ts) / Tr) × 180 + 180

  This figure shows a case where the reference phase setting signal Br (not shown) = 280 °. Bd = 280 ° is time t41. Bd = 280 ° is in the reverse feed deceleration period from time t4 to t5. The state in which the reference transfer excess determination signal Bd is at the high level is a state in which the short circuit has not been released yet and the arc has not been regenerated even though the reverse feed deceleration period has started. In such a state, it is necessary to quickly release the short circuit. For this reason, when the phase Ba of the feed speed reaches the value of the reference phase setting signal Bd during the short circuit period, the peak value Ip of the short circuit current is increased to increase the pinch force and promote the release of the short circuit. To do.

  As shown in FIG. 5C, when a short circuit between the welding wire and the base material occurs at time t21, the welding voltage Vw rapidly decreases to a short circuit voltage value of several volts. When it is determined that the welding voltage Vw has become less than the short circuit / arc determination value Vta, 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. 5G, the current control setting signal Icr changes to a predetermined initial current setting value which is a small value at time t21.

  Since the reverse feed acceleration period starts from time t3, the feed speed Fw is switched to the reverse feed direction. As shown in FIG. 5G, the current control setting signal Icr becomes the above initial current set value during a predetermined initial period from time t21 to t22, and the rising rate setting signal Sr during the period from time t22 to t23. And during the period from time t23 to t41, the value of the peak value setting signal Ipr (first peak value Ip1) is obtained.

  At time t42, even if the phase Ba of the feed speed reaches the value of the reference phase setting signal Br, the short circuit period remains, so that the reference phase excess determination signal Bd is set to the high level as shown in FIG. Change. In response to this, the value of the peak value setting signal Ipr increases to the second peak value Ip2.

  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. Therefore, as shown in FIG. 5B, the welding current Iw rapidly decreases from the welding current during the arc period at time t21, becomes an initial current value during the initial period from time t21 to t22, and from time t22 to t23. During the period, the rate increases at the rate of increase S, during the period from time t23 to t41, the first peak value Ip1, and during the period from time t41 to t42, the second peak value Ip2. For example, the initial period is set to 1 ms, and the initial current is set to 50A. The rate of increase S is set to 400 A / ms, the first peak value Ip1 is set to 450 A, and the second peak value Ip2 is set to 550 A. As shown in FIG. 5H, the reference phase excess discrimination signal Bd is at a high level during the period from time t41 to t44. As shown in FIG. 4D, the squeezing detection signal Nd is at a high level during a period from time t42 to t44 described later, and is at a low level during other periods. As shown in FIG. 5E, the drive signal Dr is at a low level during a period from time t42 to t43, which will be described later, and is at a high level during other periods. Therefore, during the period before time t42 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.

  As shown in FIG. 6C, the welding voltage Vw increases from around time t41 when the welding current Iw becomes the second peak value Ip2. This is because, in addition to the reverse feed of the welding wire, the welding current Iw increases to the second peak value Ip2, the pinch force increases, and the constriction of the droplet gradually forms.

  When the constriction formation state reaches the reference state at time t42, the constriction detection signal Nd changes to the high level as shown in FIG. In response to this, as shown in FIG. 5E, the drive signal Dr becomes a 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. 5B, the welding current Iw rapidly decreases from the second peak value Ip2 to the low level current value Il. When the welding current Iw decreases to the low level current value Il at time t43, as shown in FIG. 5E, 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. 5B, the welding current Iw maintains the low level current value Il until the arc is regenerated at time t44 because the current control setting signal Icr remains the low level current setting signal Ilr. Therefore, the transistor TR is turned off only during a period from the time when the squeezing detection signal Nd changes to the high level at time t42 until the welding current Iw decreases to the low level current value Il at time t43. As shown in FIG. 5C, the welding voltage Vw increases rapidly after once decreasing from time t42 because the welding current Iw becomes small. The low level current value Il is set to 50 A, for example.

  At time t44, when the constriction progresses due to the pinch force caused by the reverse feeding of the welding wire and the energization of the welding current Iw, and the arc is regenerated, the value of the welding voltage Vw is short-circuited / arc discriminated as shown in FIG. The value Vta or more.

  When the arc is regenerated at time t44, the value of the current control setting signal Icr rises from the value of the low level current setting signal Ilr with a predetermined arc slope as shown in FIG. When the value of 1 welding current setting signal Iwr1 is reached, that value is maintained. As shown in FIG. 5F, the delay signal Tds remains at the high level until time t45 when the first welding current energization period Tw1 elapses after the arc is regenerated at time t44. Therefore, since the welding power source is controlled at a constant current until time t45, as shown in FIG. 5B, the welding current Iw rises with an arc slope from time t44, and the value of the first welding current setting signal Iwr1. When the value is reached, the value is maintained until time t45. As shown in FIG. 5C, the welding voltage Vw is in a state of a large first welding voltage value during the first welding current energization period Tw1 from time t44 to t45. Since the arc is regenerated at time t44, the reference phase excess discrimination signal Bd changes to the low level as shown in FIG. 5H, and the squeezing detection signal Nd becomes the low level as shown in FIG. To change. For example, the arc-time inclination is set to 400 A / ms, the first welding current setting signal Iwr1 is set to 450 A, and the first welding current energization period setting signal Twr1 is set to 2 ms.

  At time t45, the delay signal Tds changes to the low level as shown in FIG. As a result, the welding power source is switched from constant current control to constant voltage control. From the time the arc is regenerated at time t44 to the time t5, the welding wire is fed backward, so the arc length gradually increases. Since it is the forward feed acceleration period from time t5, the feed speed Fw is switched to forward feed as shown in FIG. When switched to constant voltage control at time t45, as shown in FIG. 5B, the welding current Iw is energized by the second welding current Iw2 that gradually decreases from the first welding current Iw1. Similarly, as shown in FIG. 3C, the welding voltage Vw gradually decreases from the first welding voltage value. The next short circuit occurs at time t61 after the maximum forward value at time t6.

  Since the transition state of the droplets is fluctuated due to disturbance, the short-circuit period may continue even if the phase Ba of the feed speed reaches the value of the reference phase setting signal Br. If this state is left as it is, the feeding speed shifts to the normal feeding period, and it becomes more difficult to cancel the short circuit, so the short circuit period becomes longer. When the short-circuit period is prolonged, the cycle of the short-circuit and the arc and the cycle of the feed speed forward and reverse feed fall into a synchronized shift state, and the welding state becomes unstable. In the first embodiment described above, the welding current Iw is changed from the first peak value Ip1 to the second peak value Ip2 when the feeding speed phase Ba reaches the value of the reference phase setting signal Br and is in the short circuit period. increase. Thereby, since the pinch force which acts on a droplet increases, cancellation | release of a short circuit will be accelerated | stimulated and it can suppress that a short circuit period becomes long. As a result, in this Embodiment, it can suppress that the period of a short circuit and an arc, and the period of the forward feed of a feed rate, and the period of reverse feed will be in a synchronous shift state. At this time, one cycle of the feeding speed Fw at times t1 to t5 is constant and does not change.

  In the normal case where the short circuit is released and the arc is regenerated before the phase of the feed speed reaches the reference phase, the operation is the same as that of FIG. That is, the short circuit is released when the peak value of the short circuit current is the first peak value Ip1.

  According to the first embodiment described above, the peak value of the short circuit current is increased when the phase of the feeding speed reaches a predetermined reference phase during the short circuit period. As a result, when the short-circuit period continues even if the phase of the feed speed reaches the reference phase, it is possible to increase the peak value of the short-circuit current and promote the release of the short-circuit. Can be suppressed. For this reason, in the present embodiment, the period of the short-circuit and the arc and the period of the forward and reverse of the feeding speed are maintained while the period of the forward and backward feeding of the feeding speed is kept constant. Stable welding can be performed by suppressing the synchronous shift state.

[Embodiment 2]
The invention of the second embodiment detects the feed rate when the phase of the feed rate reaches the reference phase, and the amount of increase in the peak value of the short-circuit current (second peak) according to the detected feed rate. The value Ip2) is changed.

  FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the second embodiment of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and the description thereof will not be repeated. This figure is obtained by adding a reference phase feed speed detection circuit FD to FIG. 1 and replacing the peak value setting circuit IPR of FIG. 1 with a modified peak value setting circuit IPR2. Hereinafter, these blocks will be described with reference to FIG.

  The reference phase feed speed detection circuit FD receives the feed speed setting signal Fr and the reference phase setting signal Br, and feeds when the phase of the feed speed setting signal Fr reaches the value of the reference phase setting signal Br. The value of the speed setting signal Fr is detected and output as a reference phase feed speed detection signal Fd.

  The corrected peak value setting circuit IPR2 receives the reference phase feed speed detection signal Fd and the phase excess discrimination signal Bd, and when the reference phase excess discrimination signal Bd = Low level, the first peak value Ip1 is set in advance. When Bd = High level, a peak value setting signal Ipr serving as the second peak value Ip2 that changes according to the reference phase feed speed detection signal Fd is output. Here, Ip1 <Ip2. Ip2 is a function of Fd. This function is preset. Ip2 is a function that decreases as Fd increases.

  Since the timing chart of each signal in the welding power source of FIG. 3 for describing the arc welding control method according to the second embodiment of the present invention is the same as that of FIG. 2 described above, description thereof will not be repeated. However, the following operations are different.

  At time t41, when the reference phase excess determination signal Bd shown in FIG. 5H becomes High level, the reference phase feed speed detection signal Fd is output by the reference phase feed speed detection circuit FD of FIG. At the same time, a peak value setting signal Ipr that becomes the second peak value Ip2 corresponding to the reference transfer feed speed detection signal Fd is output by the corrected peak value setting circuit IPR2 of FIG.

  Therefore, during the period from time t41 to t42, the current control setting signal Icr shown in FIG. 5G and the value (second peak value Ip2) of the welding current Iw shown in FIG. It differs from FIG. 2 in that it changes depending on the value of the signal Fd.

  According to the second embodiment described above, the feeding speed when the phase of the feeding speed reaches the reference phase is detected, and the increase amount of the peak value of the short-circuit current is changed according to the detected feeding speed. Let Thereby, in addition to the effect of Embodiment 1, there exist the following effects. When the phase of the feeding speed reaches the reference phase during the short-circuit period, the appropriate value of the increase amount of the peak value for promoting the release of the short circuit differs depending on the feeding speed at that time. That is, when the feeding speed in the reverse feeding state is high, the short circuit is quickly released even if the increase amount of the peak value is small. When the increase amount of the peak value is small, the amount of spatter generated is small. On the other hand, when the feeding speed is low, the short circuit is not quickly released unless the increase amount of the peak value is increased. For this reason, in the second embodiment, the increase amount of the peak value is automatically optimized according to the detected feed speed, so that the stability of the welding state can be further improved.

1 Welding wire
2 Base material
3 Arc
4 Welding torch
5 Feeding roll
Ba Feeding speed phase BD Reference phase excess discrimination circuit
Bd Reference phase excess discrimination signal
BR reference phase setting circuit
Br reference phase setting signal
CM current comparison circuit
Cm current comparison signal
DR drive circuit
Dr drive signal
Ea Error amplification signal
EI current error amplifier circuit
Ei Current error amplification signal
EV voltage error amplifier circuit
Ev Voltage error amplification signal
FC feed control circuit
Fc feed control signal
Fd Reference phase feed speed detection circuit Fd Reference phase feed speed detection signal FR Feed speed setting circuit
Fr Feeding speed setting signal
Fw Feeding speed
ICR current control setting circuit
Icr Current control setting signal
ID welding current detection circuit
Id Welding current detection signal
Il Low level current value
ILR low level current setting circuit
Ilr low level current setting signal
Ip peak value
Ip1 first peak value Ip2 second peak value IPR peak value setting circuit
Ipr peak value setting signal
IPR2 Modified peak value setting circuit Iw Welding current
Iw1 1st welding current
Iw2 Second welding current
IWR1 first welding current setting circuit
Iwr1 1st welding current setting signal
ND Constriction detection circuit
Nd Constriction detection signal
PM Main circuit R Current reducing resistor
S Increase rate
SD short-circuit detection circuit
Sd Short circuit detection signal
SR rise rate setting circuit
Sr rise rate setting signal
SW control switching circuit
Ta elapsed time TDS off delay circuit
Tds Delay signal TR Transistor
Tr Reverse feed period Ts Forward feed period Tw1 First welding current conduction period
TWR1 first welding current conduction period setting circuit
Twr1 First welding current conduction period setting signal
VD welding voltage detection circuit
Vd Welding voltage detection signal
VR voltage setting circuit
Vr voltage setting signal
Vta short circuit / arc discrimination value
Vw welding voltage
WM feed motor

Claims (2)

In the arc welding control method of generating a short circuit period and an arc period by periodically repeating a forward feed period and a reverse feed period of the feeding speed of the welding wire, and supplying a short circuit current during the short circuit period,
When the phase of the feeding speed reaches a predetermined reference phase during the short circuit period, the peak value of the short circuit current is increased.
An arc welding control method characterized by the above. Detecting the feeding speed when the phase of the feeding speed reaches the reference phase, and changing the increase amount of the peak value of the short-circuit current according to the detected feeding speed;
The arc welding control method according to claim 1.

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