JP2018192526A - Ac non-consumable electrode arc-welding control method - Google Patents

Abstract

To maintain an average current value to a specified value even if a weld cable is long in AC non-consumable electrode arc-welding.SOLUTION: In AC non-consumable electrode arc-welding control method for welding by conduction of AC welding current Iw, an average value of an absolute value of the welding current Iw is detected, and amplitude control for changing an amplitude of the welding current Iw is performed so that the average value becomes equal to a predetermined average current set value. Further, said amplitude control is performed only when an absolute value of a difference between the average value and the average current set value is a reference value or higher. In addition, said amplitude control is performed only during a prescribed period from an arc start. Consequently, an inductance value becomes large since a weld cable is long, and the average current value is maintained to a prescribed value even if a welding current waveform is changed, and therefore, a weld penetration depth can be stabilized.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an AC non-consumable electrode arc welding control method for performing welding by energizing an AC welding current.

  AC non-consumable electrode arc welding includes AC TIG welding, AC plasma arc welding, and the like. In AC non-consumable electrode arc welding, a non-consumable electrode such as a tungsten electrode is used as an electrode, and welding is performed by generating an arc by energizing an AC welding current in a state shielded from the atmosphere by a shielding gas such as argon gas. I do. The AC welding current is formed from an electrode negative polarity current during the electrode negative polarity period and an electrode positive polarity current during the electrode positive polarity period. The electrode minus polarity and the electrode plus polarity are alternately repeated, and the electrode minus polarity and the electrode plus polarity form one cycle.

  AC non-consumable electrode arc welding is mainly used for aluminum welding. There is an oxide film on the surface of the aluminum material, which is a base material, and good welding cannot be performed unless this is removed. In AC non-consumable electrode arc welding, a cathode spot is formed on the surface of the base material during the electrode positive polarity period. The action (cleaning action) of removing the oxide film works by the energy when the cathode spot is formed. That is, in AC non-consumable electrode arc welding, an oxide film is removed by providing a cleaning action by providing an electrode positive polarity period. At this time, since the non-consumable electrode is consumed quickly, the electrode positive polarity period is set to the shortest period in which an appropriate cleaning width can be secured. The time ratio of the electrode negative polarity period in one cycle is about 70%. In the following description, the non-consumable electrode may be simply referred to as an electrode.

  In the invention of Patent Document 1, in AC TIG welding, an average current set value, an electrode minus polarity period ratio set value, and an electrode minus polarity period set value are input, and an electrode minus polarity current set value, an electrode plus polarity current set value, and an electrode plus. The polarity period set value is calculated, and the waveform parameter of the welding current is determined.

Japanese Patent No. 3173159

  When the welding cable connecting the welding power source and the welding torch (arc generation location) is as short as several meters, the welding cable's inductance value is small, so the set welding current waveform and the waveform of the welding current that is actually energized Is almost identical.

  However, when the length of the welding cable is 10 m or more, sometimes it may be 50 m. In such a case, the inductance value of the welding cable increases. As the inductance value of the current path increases, the rate of change of the welding current becomes slower, so that the set welding current waveform and the waveform of the welding current that is actually energized differ. As a result, the average value of the welding current to be energized is smaller than the average current set value. Since the average value of the welding current correlates with the penetration depth, when the average value of the welding current becomes small, the penetration depth becomes small and the welding quality deteriorates.

  Therefore, an object of the present invention is to provide a non-consumable electrode arc welding control method in which the average value of the welding current that is energized is always equal to the average current set value even when the welding cable is long.

In order to solve the above-described problems, the invention of claim 1
In the AC non-consumable electrode arc welding control method of conducting welding by passing an AC welding current formed from an electrode negative polarity current during an electrode negative polarity period and an electrode positive polarity current during an electrode positive polarity period,
Detecting an average value of the absolute value of the welding current;
Amplitude control is performed to change the amplitude of the welding current so that the average value is equal to a predetermined average current setting value.
An AC non-consumable electrode arc welding control method characterized by the above.

The invention according to claim 2 performs the amplitude control only when an absolute value of a difference between the average value and the average current set value is a reference value or more.
The AC non-consumable electrode arc welding control method according to claim 1.

The invention according to claim 3 performs the amplitude control only during a predetermined period from the arc start.
The AC non-consumable electrode arc welding control method according to claim 1 or 2, characterized in that

The invention of claim 4 detects the electrode negative polarity ratio during welding,
Waveform control is performed to change the waveform parameter of the welding current so that the electrode negative polarity ratio becomes equal to a predetermined set value.
It is an alternating current non-consumable electrode arc welding control method of any one of Claims 1-3 characterized by the above-mentioned.

In the invention of claim 5, the electrode negative polarity ratio is a time ratio of the electrode negative polarity period in one cycle.
The AC non-consumable electrode arc welding control method according to claim 4.

In the invention of claim 6, the electrode negative polarity ratio is a ratio of an integrated value of the electrode negative polarity current (absolute value) to an integrated value of one cycle of the welding current (absolute value).
The AC non-consumable electrode arc welding control method according to claim 4.

The invention of claim 7 performs the waveform control only during a predetermined period from the arc start.
It is an alternating current non-consumable electrode arc welding control method of any one of Claims 4-6 characterized by the above-mentioned.

The invention of claim 8 detects the cycle of the welding current,
Performing cycle control to change the waveform parameter of the welding current so that the cycle is equal to a predetermined set value;
It is an alternating current non-consumable electrode arc welding control method of any one of Claims 1-3 characterized by the above-mentioned.

  According to the present invention, even when the welding cable is long, the average value of the welding current that is energized is always equal to the average current set value. For this reason, high quality welding becomes possible.

It is a block diagram of the welding apparatus for implementing the alternating current non-consumable electrode arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG. It is a block diagram of the welding apparatus for enforcing the AC non-consumable electrode arc welding control method which concerns on Embodiment 2 of this invention. It is a block diagram of the welding apparatus for enforcing the AC non-consumable electrode arc welding control method which concerns on Embodiment 3 of this invention. It is a block diagram of the welding apparatus for enforcing the AC non-consumable electrode arc welding control method which concerns on Embodiment 4 of this invention. It is a block diagram of the welding apparatus for enforcing the alternating current non-consumable electrode arc welding control method which concerns on Embodiment 5 of this invention. It is a block diagram of the welding apparatus for enforcing the alternating current non-consumable electrode arc welding control method which concerns on Embodiment 6 of this invention. It is a block diagram of the welding apparatus for enforcing the alternating current non-consumable electrode arc welding control method which concerns on Embodiment 7 of this invention.

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

[Embodiment 1]
1 is a block diagram of a welding apparatus for carrying out an AC non-consumable electrode arc welding control method according to Embodiment 1 of the present invention. In the figure, a circuit that applies a high voltage of several hundred volts at the time of polarity switching is not shown. Hereinafter, each block will be described with reference to FIG.

  The inverter circuit INV receives an AC commercial power source (not shown) such as a three-phase 200V as an input, performs inverter control by pulse width modulation control using a current error amplification signal Ei, which will be described later, and rectifies and smoothes a DC voltage. Is output.

  The inverter transformer INT steps down the high-frequency AC voltage to a voltage value suitable for arc welding.

  The secondary rectifiers D2a to D2d rectify the stepped-down high-frequency alternating current into direct current.

  The electrode plus polarity transistor PTR is turned on by an electrode plus polarity drive signal Pd described later, and the output of the welding power source becomes the electrode plus polarity EP. The electrode negative polarity transistor NTR is turned on by an electrode negative polarity drive signal Nd described later, and the output of the welding power source becomes the electrode negative polarity EN.

  The reactor WL smooths the rippled output.

  An electrode 1 is attached to the tip of the welding torch 4, and an arc 3 is generated between the electrode 1 and the base material 2. An AC welding current Iw is passed through the arc 3, and an AC welding voltage Vw is applied between the electrode 1 and the base material 2. It is customary that the welding current Iw is set to the + side when energizing in the direction of the base material 2 → the arc 3 → the electrode 1 (in the electrode negative polarity period Ten).

  Two output terminals (not shown) of the welding power source and the welding torch 4 or the base material 2 are connected by welding cables 5 and 6. When the welding cables 5 and 6 are long, the inductance value becomes large, and the changing speed of the welding current Iw becomes gentle. The inductance value also varies greatly depending on the routing state of the welding cables 5 and 6. When the welding cables 5 and 6 are wound around, the inductance value becomes very large.

  The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr. The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr.

  The current detection circuit ID detects the absolute value of the welding current Iw and outputs a current detection signal Id.

  The current comparison circuit CM receives the current detection signal Id, and outputs a current comparison signal Cm that is at a high level when the value of the current detection signal Id is equal to or less than a predetermined polarity switching current value. The polarity switching current value is set to 50A, for example.

The timer circuit TM receives the electrode negative polarity period setting signal Tnr, the electrode positive polarity period setting signal Tpr, and the current comparison signal Cm, performs the following processing, and outputs a timer signal Tm. When the timer signal Tm is 1 and 2, the electrode minus polarity period Ten is set, and when the timer signal Tm is 3 and 4, the electrode plus polarity period Tep is set.
1) The timer signal Tm = 1 is output during a period determined by the electrode negative polarity period setting signal Tnr.
2) Subsequently, the timer signal Tm = 2 is output during the transition period from when the period determined by the electrode negative polarity period setting signal Tnr elapses until the current comparison signal Cm changes to the High level.
3) Subsequently, the timer signal Tm = 3 is output during the period determined by the electrode positive polarity period setting signal Tpr after the current comparison signal Cm changes to the High level.
4) Subsequently, the timer signal Tm = 4 is output during the transition period from when the period determined by the electrode positive polarity period setting signal Tpr elapses until the current comparison signal Cm changes to the High level.
5) Repeat 1) to 4) above.

  The secondary drive circuit DV receives the timer signal Tm as an input, outputs the electrode negative polarity drive signal Nd when the timer signal Tm is 1 or 2, and outputs the electrode negative polarity drive signal Nd when the timer signal Tm is 3 or 4. Electrode positive polarity drive signal Pd is output. Accordingly, when the timer signal Tm is 1 or 2, the electrode minus polarity transistor NTR is turned on, and the electrode minus polarity period Ten is entered. When the timer signal Tm is 3 or 4, the electrode plus polarity transistor PTR is turned on, and the electrode plus polarity period Tep is entered.

  The electrode negative polarity current amplitude setting circuit INR outputs a predetermined electrode negative polarity current amplitude setting signal Inr.

  The average current detection circuit IAD receives the current detection signal Id as described above, calculates an average value, and outputs an average current detection signal Iad. For example, the average value is calculated by passing the current detection signal Id through a low-pass filter having a cutoff frequency of about 1 to 5 Hz. The average value may be calculated by sampling the current detection signal Id about every 0.1 ms and calculating the average value for every predetermined period of the welding current waveform.

  The average current setting circuit IAR outputs a predetermined average current setting signal Iar.

  The average current error amplification circuit EA receives the average current setting signal Iar and the average current detection signal Iad as input, amplifies the error between the two values, and average current error amplification signal Ea = G · (Iar−Iad) Is output. G is an amplification factor, and is set to about 0.2 to 2, for example. This amplification factor G is adjusted so that the amplitude control system becomes stable.

  The amplitude control circuit INC receives the electrode negative polarity current amplitude setting signal Inr and the average current error amplification signal Ea as input, integrates the average current error amplification signal Ea during welding, and generates an electrode negative polarity current amplitude control signal. Inc = Inr + ∫Ea · dt is output. Inc> 0.

  The electrode positive polarity current amplitude control circuit IPC receives the electrode negative polarity current amplitude control signal Inc as an input and calculates and outputs the electrode positive polarity current amplitude control signal Ipc by a predetermined function. The function is, for example, Ipc = Inc + 50. At this time, the welding current Iw has a non-equilibrium waveform. The function may be Ipc = Inc. At this time, the amplitudes of both polarities have the same value, and the welding current Iw has a balanced waveform. Ipc> 0.

  The average current error amplifying circuit EA, the amplitude control circuit INC, and the electrode plus polarity current amplitude control circuit IPC are used so that the value of the average current detection signal Iad becomes equal to the value of the average current setting signal Iar. The amplitudes of the negative polarity current Ien and the electrode positive polarity current Iep are controlled (amplitude control).

The switching circuit SW receives the timer signal Tm, the electrode negative polarity current amplitude control signal Inc and the electrode positive polarity current amplitude control signal Ipc as input, and outputs a current setting signal Ir.
1) When the timer signal Tm = 1, the electrode negative polarity current amplitude control signal Inc is output as the current setting signal Ir.
2) When the timer signal Tm = 2, the current setting signal Ir = 0 is output.
3) When the timer signal Tm = 3, the electrode positive polarity current amplitude control signal Ipc is output as the current setting signal Ir.
4) When the timer signal Tm = 4, the current setting signal Ir = 0 is output.

  The current error amplification circuit EI amplifies an error between the current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal Ei. As a result, the welding power source has a constant current characteristic, and the AC welding current Iw is energized.

  FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. (A) shows the time change of the welding current Iw, (B) shows the time change of the current comparison signal Cm, (C) shows the time change of the electrode negative polarity drive signal Nd, FIG. 4D shows the time change of the electrode positive polarity drive signal Pd, and FIG. 4E shows the time change of the current setting signal Ir. The welding current Iw shown in FIG. 2A is the electrode negative polarity current Ien from 0 to the upper side, and the electrode positive polarity current Iep from 0 to the lower side. This figure shows a non-equilibrium waveform in which the amplitude of the electrode plus polarity EP of the welding current Iw is larger than the amplitude of the electrode minus polarity EN. Hereinafter, the operation of each signal will be described with reference to FIG.

  At time t1, the absolute value of the welding current Iw (electrode plus polarity current Iep) becomes equal to or less than a predetermined polarity switching current value as shown in FIG. The current comparison signal Cm becomes High level for a short time. In response to this, as shown in FIG. 5C, the electrode minus polarity drive signal Nd becomes the high level, the electrode minus polarity transistor NTR is turned on, and the electrode minus polarity EN is switched. At the same time, as shown in FIG. 4D, the electrode positive polarity drive signal Pd becomes Low level, and the electrode positive polarity transistor PTR is turned off. At time t1, the current setting signal Ir switches from 0 to the electrode negative polarity current amplitude control signal Inc as shown in FIG. As shown in FIG. 6A, the welding current Iw instantaneously changes from a negative polarity switching current value to a positive polarity switching current value.

  During the period from the time t1 to the time t2, the welding current Iw increases with a slope from the polarity switching current value to the value of the electrode minus polarity current amplitude control signal Inc, as shown in FIG. This inclination is determined by the inductance value of the welding cable. The slope becomes gentler as the inductance value increases. During the period from the time t2 to the time t3, as shown in FIG. 5A, the welding current Iw becomes the value of the electrode negative polarity current amplitude control signal Inc.

  When the elapsed time from time t1 reaches the value of the electrode negative polarity period setting signal Tnr at time t3, the current setting signal Ir changes to 0 as shown in FIG. In response to this, the welding current Iw decreases with a slope, as shown in FIG. This inclination is also determined by the inductance value of the welding cable. At time t4, when the value of the welding current Iw becomes equal to or less than the polarity switching current value, the current comparison signal Cm becomes a high level for a short time as shown in FIG.

  At time t4, when the current comparison signal Cm becomes High level for a short time as shown in FIG. 5B, the electrode positive polarity drive signal Pd becomes High level as shown in FIG. The transistor PTR is turned on and switched to the electrode positive polarity EP. At the same time, as shown in FIG. 5C, the electrode minus polarity drive signal Nd becomes Low level, and the electrode minus polarity transistor NTR is turned off. At time t4, as shown in FIG. 5E, the current setting signal Ir switches from 0 to a positive value electrode positive polarity current amplitude control signal Ipc. As shown in FIG. 5A, the welding current Iw instantaneously changes from a positive polarity switching current value to a negative polarity switching current value.

  During the period from time t4 to t5, as shown in FIG. 5A, the welding current Iw increases with a slope from the polarity switching current value to the value of the electrode plus polarity current amplitude control signal Ipc. This inclination is also determined by the inductance value of the welding cable. During the period from time t5 to t6, as shown in FIG. 5A, the welding current Iw becomes the value of the electrode plus polarity current amplitude control signal Ipc.

  When the elapsed time from time t4 reaches the value of the electrode positive polarity period setting signal Tpr at time t6, the current setting signal Ir changes to 0 as shown in FIG. In response to this, the welding current Iw decreases with a slope, as shown in FIG. This inclination is also determined by the inductance value of the welding cable. At time t7, when the value of the welding current Iw becomes equal to or less than the polarity switching current value, the current comparison signal Cm becomes a high level for a short time as shown in FIG.

  Thereafter, the above operation is repeated.

  Time t1 to t7 is one cycle. The inclination of the time t1 to t2, the time t3 to t4, the time t4 to t5, and the time t6 to t7 is affected by the inductance value by the welding cable, so the average current value changes. Therefore, in the present embodiment, the average value of the absolute values of the welding current Iw is output as the average current detection signal Iad, and the value of the average current detection signal Iad is equal to the predetermined average current setting signal Iar. The electrode negative polarity current amplitude control signal Inc and the electrode positive polarity current amplitude control signal Ipc are feedback-controlled. Thereby, since the positive / negative amplitude of the welding current Iw is controlled, the average current value becomes a predetermined value. The figure shows the case where the welding current waveform is a non-equilibrium waveform, but the same applies to the case of a balanced waveform. Further, the figure shows the case where the welding current waveform is a trapezoidal wave, but the same applies to the case where the waveform changes in a curved shape such as a sine wave.

  According to the first embodiment described above, the average value of the absolute value of the welding current is detected, and amplitude control is performed to change the amplitude of the welding current so that the average value becomes equal to a predetermined average current set value. Thereby, in this Embodiment, even if an inductance value is large because the welding cable is long, the average value of the welding current to be energized can be controlled to be always equal to the average current set value. For this reason, the penetration depth can be made uniform, and a high-quality welding result can be obtained.

[Embodiment 2]
In the invention of the second embodiment, the above-described amplitude control is performed only when the absolute value of the difference between the average current detection signal Iad and the average current setting signal Iar is equal to or greater than a reference value.

  FIG. 3 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 2 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 replacing the average current error amplifier circuit EA of FIG. 1 with a second average current error amplifier circuit EA2. Hereinafter, this block will be described with reference to FIG.

  The second average current error amplifier circuit EA2 receives the average current setting signal Iar and the average current detection signal Iad as input, and the absolute value | Iar−Iad | of the difference between the two signals is less than a predetermined reference value. Outputs an average current error amplification signal Ea = 0, and when the absolute value of the difference is greater than or equal to the reference value, amplifies the error of both values and outputs an average current error amplification signal Ea = G · (Iar−Iad). . The reference value is set to 5A, for example.

  With the above circuit, amplitude control is performed only when the absolute value of the difference between the average current detection signal Iad and the average current setting signal Iar is equal to or greater than a reference value. As a result, when the average value of the welding current Iw is close to the set value, the amplitude control is not performed, so that the control system is stabilized without being sensitive control, and the welding state is further stabilized. At this time, when the average value of the welding current Iw approximates the set value, there is little fluctuation in the penetration depth, and there is no problem in the welding quality.

[Embodiment 3]
In the invention of the third embodiment, the amplitude control is performed only for a predetermined period from the arc start.

  FIG. 4 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 3 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 an initial period circuit TS to FIG. 1 and replacing the average current error amplifier circuit EA of FIG. 1 with a third average current error amplifier circuit EA3. Hereinafter, these blocks will be described with reference to FIG.

  The initial period circuit TS receives the current detection signal Id as described above, and outputs an initial period signal Ts that becomes High level only for a predetermined period after this value becomes equal to or greater than a predetermined energization determination value. The energization determination value is set to 1A, for example. The period in which the initial period signal Ts is at the high level is when the arc start is in a predetermined period. The predetermined period is set to about 0.1 to 1 second, for example.

  The third average current error amplifier circuit EA3 receives the average current setting signal Iar, the average current detection signal Iad, and the initial period signal Ts as input, and when the initial period signal Ts is at the low level, the average current error amplification is performed. When the signal Ea = 0 is output and the initial period signal Ts is at the high level, the error of both values is amplified and the average current error amplified signal Ea = G · (Iar−Iad) is output.

  With the above circuit, amplitude control is performed for a predetermined period from the arc start. The inductance value due to the welding cable hardly changes once the welding cable is laid. For this reason, if the amplitude control is performed only for a short time from the arc start, the average value of the welding current Iw thereafter matches the set value. By doing in this way, since amplitude control is performed only for a short time, a control system is stabilized and a welding state is further stabilized. The third embodiment is based on the first embodiment, but may be based on the second embodiment.

[Embodiment 4]
In addition to the amplitude control described above, the fourth embodiment of the invention detects the electrode negative polarity ratio during welding and changes the waveform parameter of the welding current so that the electrode negative polarity ratio becomes equal to a predetermined set value. Waveform control is performed.

  FIG. 5 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 4 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 an electrode minus polarity ratio detection circuit RND, an electrode minus polarity ratio setting circuit RNR, a ratio error amplification circuit EH, and a waveform control circuit TPC to FIG. Hereinafter, these blocks will be described with reference to FIG.

The electrode negative polarity ratio detection circuit RND receives the timer signal Tm, performs the following processing, and outputs an electrode negative polarity ratio detection signal Rnd. In the present embodiment, the electrode negative polarity ratio is the time ratio (%) of the electrode negative polarity period in one cycle.
1) The time when the timer signal Tm changes from 1 → 2 → 3 is measured as the electrode negative polarity period Ten.
2) The time for the timer signal Tm to change from 1 → 2 → 3 → 4 → 1 is measured as one cycle Tf.
3) An electrode minus polarity ratio detection signal Rnd = (Ten / Tf) × 100 is calculated and output.

  The electrode negative polarity ratio setting circuit RNR outputs a predetermined electrode negative polarity ratio setting signal Rnr.

  The ratio error amplification circuit EH receives the electrode minus polarity ratio detection signal Rnd and the electrode minus polarity ratio setting signal Rnr as described above, amplifies the error between the two values, and produces a ratio error amplification signal Eh = Gh · (Rnd− Rnr) is output. Gh is a positive amplification factor, and is set to about 0.01 to 0.1, for example. This amplification factor Gh is adjusted so that the waveform control system becomes stable.

  The waveform control circuit TPC receives the electrode plus polarity period setting signal Tpr and the ratio error amplification signal Eh as inputs, integrates the ratio error amplification signal Eh during welding, and produces an electrode plus polarity period control signal Tpc = Tpr + ∫. Eh · dt is output. The electrode plus polarity period control signal Tpc is input to the timer circuit TM as a substitute signal for the electrode plus polarity period setting signal Tpr.

  By using the ratio error amplifier circuit EH and the waveform control circuit TPC, the electrode plus polarity is used as a waveform parameter of the welding current so that the value of the electrode minus polarity ratio detection signal Rnd is equal to the value of the electrode minus polarity ratio setting signal Rnr. The period Tep (electrode plus polarity period control signal Tpc) is controlled (waveform control). That is, if the electrode positive polarity period Tep and / or the electrode negative polarity period Ten which are waveform parameters of the welding current are feedback-controlled so that the electrode negative polarity ratio detection signal Rnd and the electrode negative polarity ratio setting signal Rnr are equal. good.

  Since the timing chart of each signal in the welding apparatus of FIG. 5 is the same as that of FIG. 2 described above, description thereof will not be repeated. However, the following points are different. In FIG. 2, time t1 to t7 is one cycle Tf. The inclination of time t1 to t2, time t3 to t4, time t4 to t5, and time t6 to t7 is affected by the inductance value of the welding cable. Here, the electrode negative polarity ratio detection signal Rnd (%) = (Ten / Tf) × 100 = (time from time t1 to t4 / time from time t1 to t7) × 100. For this reason, the value of the electrode minus polarity ratio detection signal Rnd is greatly affected by the inductance value of the welding cable. Therefore, in the present embodiment, the electrode negative polarity ratio during welding is detected, and the waveform parameter of the welding current is set so that the electrode negative polarity ratio detection signal Rnd is equal to the predetermined electrode negative polarity ratio setting signal Rnr. Waveform control is performed to change one electrode plus polarity period control signal Tpc. As a result, the electrode positive polarity period Tep from time t4 to t7 is controlled, so that the electrode negative polarity ratio detection signal Rnd becomes a predetermined value. The waveform parameter to be changed is the electrode plus polarity period Tep and / or the electrode minus polarity period Ten. In the present embodiment, waveform control is added on the basis of the first embodiment, but waveform control may be added on the basis of the second or third embodiment.

  According to the fourth embodiment described above, in addition to the effects of the first to third embodiments, the electrode negative polarity ratio during welding is detected, and the welding current is set so that the electrode negative polarity ratio becomes equal to a predetermined set value. Perform waveform control to change the waveform parameter. Thereby, in this Embodiment, even if the inductance value of a welding cable changes, an electrode minus polarity ratio can always be maintained at a desired value. For this reason, the shape of the weld bead can be made uniform, and a high-quality welding result can be obtained.

[Embodiment 5]
In the invention of the fifth embodiment, the electrode negative polarity ratio is the time ratio of the electrode negative polarity period occupying one cycle in the fourth embodiment, whereas the integrated value of one cycle of the welding current (absolute value). The difference is the ratio of the integral value of the electrode negative polarity current (absolute value).

  FIG. 6 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 5 of the present invention. This figure corresponds to FIG. 5 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by replacing the electrode negative polarity ratio detection circuit RND of FIG. 5 with a second electrode negative polarity ratio detection circuit RND2. Hereinafter, this block will be described with reference to FIG.

The second electrode negative polarity ratio detection circuit RND2 receives the timer signal Tm and the current detection signal Id, performs the following processing, and outputs an electrode negative polarity ratio detection signal Rnd. In the present embodiment, the electrode negative polarity ratio is the ratio (%) of the integrated value of the electrode negative polarity current (absolute value) to the integrated value of one cycle of the welding current (absolute value).
1) The integral value of the current detection signal Id (electrode negative polarity current) during the electrode negative polarity period Ten in which the timer signal Tm is 1 and 2 is calculated.
2) The integral value of the current detection signal Id in one cycle Tf in which the timer signal Tm is 1 to 4 is calculated.
3) Calculate and output electrode negative polarity ratio detection signal Rnd = ((integral value of electrode negative polarity current) / (integral value of welding current in one cycle)) × 100.

  The timing chart of each signal in the welding apparatus of FIG. 6 is the same as that of FIG. However, in the present embodiment, the electrode minus polarity ratio detection signal Rnd is the ratio of the integral value of the electrode minus polarity current (absolute value) to the integral value of one cycle of the welding current (absolute value). According to the fifth embodiment, the same effect as in the fourth embodiment is obtained.

[Embodiment 6]
In the invention of the sixth embodiment, the waveform control of the fourth and fifth embodiments is performed only for a predetermined period from the arc start.

  FIG. 7 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 6 of the present invention. This figure corresponds to FIG. 5 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. In FIG. 5, an initial period circuit TS is added to FIG. 5, the average current error amplifier circuit EA of FIG. 5 is replaced with a third average current error amplifier circuit EA3, and the ratio error amplifier circuit EH of FIG. This is a replacement for the amplifier circuit EH2. Hereinafter, these blocks will be described with reference to FIG.

  Since the operations of the initial period circuit TS and the third average current error amplifier circuit EA3 are the same as those of the same circuit of FIG. 4, the description will not be repeated. The second ratio error amplifier circuit EH2 receives the electrode minus polarity ratio detection signal Rnd, the electrode minus polarity ratio setting signal Rnr, and the initial period signal Ts as input, and when the initial period signal Ts is at the low level, The error amplification signal Eh = 0 is output, and when the initial period signal Ts is at the high level, the error of both values is amplified and the ratio error amplification signal Eh = Gh · (Rnd−Rnr) is output.

  By the above circuit, waveform control is performed for a predetermined period from the arc start. The inductance value due to the welding cable hardly changes once the welding cable is laid. For this reason, if the waveform control is performed only for a short time from the arc start, the electrode minus polarity ratio thereafter matches the set value. By doing in this way, since waveform control is performed only for a short time, the control system is stabilized and the welding state is further stabilized. The sixth embodiment is based on the fourth embodiment, but may be based on the fifth embodiment.

[Embodiment 7]
In the seventh embodiment, in addition to the amplitude control of the first to third embodiments, the cycle of the welding current is detected and the waveform parameter of the welding current is changed so that the cycle becomes equal to a predetermined set value. It is.

  FIG. 8 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to Embodiment 7 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 period detection circuit TFD, a period setting circuit TFR, a period error amplifying circuit ES, and a period control circuit TPC2 to FIG. Hereinafter, these blocks will be described with reference to FIG.

  The period detection circuit TFD receives the timer signal Tm as an input, measures the time when the timer signal Tm changes from 1 → 2 → 3 → 4 → 1 as one period Tf, and outputs it as the period detection signal Tfd.

  The period setting circuit TFR outputs a predetermined period setting signal Tfr.

  The period error amplifier circuit ES receives the period detection signal Tfd and the period setting signal Tfr as input, amplifies the error between the two values, and outputs a period error amplification signal Es = Gs · (Tfr−Tfd). Gs is a positive gain, and is set to about 0.1 to 1.0, for example. This amplification factor Gs is adjusted so that the periodic control system becomes stable.

  The period control circuit TPC2 receives the electrode plus polarity period setting signal Tpr and the period error amplification signal Es as inputs, integrates the period error amplification signal Es during welding, and generates an electrode plus polarity period control signal Tpc = Tpr + ∫. Es · dt is output.

  The period error amplification circuit ES and the period control circuit TPC2 make the electrode positive polarity period Tep (electrode plus polarity) as a waveform parameter of the welding current so that the value of the period detection signal Tfd becomes equal to the value of the period setting signal Tfr. The period control signal Tpc) is controlled (period control). That is, if the electrode positive polarity period Tep and / or the electrode negative polarity period Ten which are waveform parameters of the welding current are feedback-controlled so that the electrode negative polarity ratio detection signal Rnd and the electrode negative polarity ratio setting signal Rnr are equal. good.

  Since the timing chart of each signal in the welding apparatus of FIG. 8 is the same as that of FIG. 2 described above, description thereof will not be repeated. However, the following points are different. In FIG. 2, time t1 to t7 is one cycle Tf. The inclination of time t1 to t2, time t3 to t4, time t4 to t5, and time t6 to t7 is affected by the inductance value of the welding cable. For this reason, the value of the period detection signal Tfd varies greatly depending on the inductance value of the welding cable. Therefore, in the present embodiment, the period Tf during welding is detected, and the electrode plus polarity period which is one of the waveform parameters of the welding current is set so that the period detection signal Tfd becomes equal to the predetermined period setting signal Tfr. Period control for changing the control signal Tpc is performed. As a result, the electrode positive polarity period Tep between times t4 and t7 is controlled, so that the cycle detection signal Tfd becomes a predetermined value. The waveform parameter to be changed is the electrode plus polarity period Tep and / or the electrode minus polarity period Ten. In the present embodiment, periodic control is added on the basis of the first embodiment, but periodic control may be added on the basis of the second and third embodiments.

  According to the seventh embodiment described above, in addition to the effects of the first to third embodiments, the period during welding is detected, and the waveform parameter of the welding current is changed so that the period becomes equal to a predetermined set value. Perform cycle control. Thereby, in this Embodiment, even if the inductance value of a welding cable changes, a period can always be maintained at a desired value. For this reason, the shape of the weld bead can be made uniform, and a high-quality welding result can be obtained.

  In the above, AC non-consumable electrode arc welding is the case of AC TIG welding, but the same applies to the case of AC plasma arc welding.

DESCRIPTION OF SYMBOLS 1 Electrode 2 Base material 3 Arc 4 Welding torch 5, 6 Welding cable CM Current comparison circuit Cm Current comparison signal D2a-D2d Secondary rectifier DV Secondary side drive circuit EA Average current error amplification circuit Ea Average current error amplification signal EA2 2nd Average current error amplifier circuit EA3 Third average current error amplifier circuit EH Ratio error amplifier circuit Eh Ratio error amplifier signal EH2 Second ratio error amplifier circuit EI Current error amplifier circuit Ei Current error amplifier signal EN Electrode minus polarity EP Electrode plus polarity ES Period Error amplification circuit Es Periodic error amplification signal G Amplification factor Gh Amplification factor Gs Amplification factor IAD Average current detection circuit Iad Average current detection signal IAR Average current setting circuit Iar Average current setting signal ID Current detection circuit Id Current detection signal Ien Electrode minus polarity current Iep electrode positive polarity current INC amplitude control circuit Inc electrode negative polarity current Amplitude control signal INR Electrode negative polarity current amplitude setting circuit Inr Electrode negative polarity current amplitude setting signal INT Inverter transformer INV Inverter circuit IPC Electrode plus polarity current amplitude control circuit Ipc Electrode plus polarity current amplitude control signal Ir Current setting signal Iw Welding current Nd Electrode Negative polarity drive signal NTR Electrode minus polarity transistor Pd Electrode plus polarity drive signal PTR Electrode plus polarity transistor RND Electrode minus polarity ratio detection circuit Rnd Electrode minus polarity ratio detection signal RND2 Second electrode minus polarity ratio detection circuit RNR Electrode minus polarity ratio setting circuit Rnr electrode minus polarity ratio setting signal SW switching circuit Ten electrode minus polarity period Tep electrode plus polarity period Tf period TFD period detection circuit Tfd period detection signal TFR period setting circuit Tfr period setting signal M Timer circuit Tm Timer signal TNR Electrode minus polarity period setting circuit Tnr Electrode minus polarity period setting signal TPC Waveform control circuit Tpc Electrode plus polarity period control signal TPC2 Period control circuit TPR Electrode plus polarity period setting circuit Tpr Electrode plus polarity period setting signal TS Initial period circuit Ts Initial period signal Vw Welding voltage WL Reactor

Claims (8)

In the AC non-consumable electrode arc welding control method of conducting welding by passing an AC welding current formed from an electrode negative polarity current during an electrode negative polarity period and an electrode positive polarity current during an electrode positive polarity period,
Detecting an average value of the absolute value of the welding current;
Amplitude control is performed to change the amplitude of the welding current so that the average value is equal to a predetermined average current setting value.
An AC non-consumable electrode arc welding control method. The amplitude control is performed only when the absolute value of the difference between the average value and the average current setting value is greater than or equal to a reference value.
The AC non-consumable electrode arc welding control method according to claim 1. The amplitude control is performed only during a predetermined period from the arc start.
The AC non-consumable electrode arc welding control method according to claim 1 or 2, characterized in that: Detect electrode negative polarity ratio during welding,
Waveform control is performed to change the waveform parameter of the welding current so that the electrode negative polarity ratio becomes equal to a predetermined set value.
The AC non-consumable electrode arc welding control method according to any one of claims 1 to 3. The electrode negative polarity ratio is a time ratio of the electrode negative polarity period occupying one cycle.
The AC non-consumable electrode arc welding control method according to claim 4. The electrode negative polarity ratio is a ratio of an integrated value of the electrode negative polarity current (absolute value) to an integrated value of one cycle of the welding current (absolute value).
The AC non-consumable electrode arc welding control method according to claim 4. The waveform control is performed only during a predetermined period from the arc start.
The AC non-consumable electrode arc welding control method according to any one of claims 4 to 6. Detecting the cycle of the welding current;
Performing cycle control to change the waveform parameter of the welding current so that the cycle is equal to a predetermined set value;
The AC non-consumable electrode arc welding control method according to any one of claims 1 to 3.

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