JPH09108836A - Method for controlling consumable nozzle type ac arc welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable arc by eliminating the defective welding such as arc break at the inversion in the polarity to achieve the smooth inversion of polarity. SOLUTION: The dead time delay signal X in which the prescribed delay time is added to the period (dead time period) in which both a switching element QN for positive polarity to output the positive polarity of a secondary side inverter part 4 and a switching element QP for reverse polarity to output the reverse polarity are in the non-conductive condition (OFF condition) is prepared by a dead time delay signal output control part 20. During the period of the dear time delay signal X, the arc/short circuit detecting signal A/S to be outputted from an arc/short circuit detecting part 21 is forcibly in the arc condition so that no mis-judgment of the short circuit is made though the arc/short circuit detecting part 21 is generating the arc between a welding wire 8 and a base metal 10 which is a work, and the rise of the current at the inversion of polarity is steep to control so that the current instantaneously becomes the pulse current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a consumable electrode type AC arc welding machine for performing arc welding by applying an AC voltage between a welding wire which is a consumable electrode and a base material which is a workpiece. It is a thing. The alternating voltage applied between the welding wire and the base metal is a waveform in which the welding wire has a positive polarity and a reverse polarity period in which the welding wire has a negative polarity and the positive polarity period in which the welding wire has a negative polarity are alternately repeated with a dead time in between.
The ratio of the length of the positive polarity period to the length of the reverse polarity period can be set arbitrarily according to, for example, the material of the base material.

[0002]

2. Description of the Related Art FIG. 7 shows a circuit block diagram of a conventional consumable electrode type AC arc welding machine. In FIG. 7, 1 is a power supply input terminal of an AC arc welding machine from a three-phase AC power supply, and 2 is 1
Next inverter part, 3 is a welding transformer, 4 is a secondary inverter part, 5 is a reactor for limiting current, 6 is an output terminal of an AC arc welding machine, 7 is a contact tip for energization, 8 is a contact tip for energization 7. A welding wire as a consumable electrode to be fed out, a welding arc 9 and a base material 10 as an object to be welded, and the above is the main circuit portion of the consumable electrode type AC arc welding machine.

11 is a welding output voltage V appearing at the output terminal 6.
_{Based on} the size of _O , it is determined whether the welding wire 8 is short-circuited in contact with the base material 10 or an arc is generated, and an arc / short circuit determination signal A / S is output to the arithmetic control unit 15 described later. It is a detection unit. Reference numeral 12 is a welding output current detector for detecting the welding output current I _O for feedback control. Reference numeral 13 denotes a secondary inverter control unit that controls ON / OFF of the reverse polarity switching element QP and the positive polarity switching element QN of the secondary side inverter unit 4. Reference numeral 14 is a superposition circuit unit for applying re-ignition superposition voltages V _EP and V _EN for smoothly performing polarity reversal. Reference numeral 15 denotes an arithmetic control unit for smoothly and appropriately executing each control. Reference numeral 16 is a welding current setting device, 17 is a welding voltage setting device, and 18 is a positive ratio setting device for setting a positive ratio (a ratio of a period in which the welding wire 8 as a consumable electrode has a negative polarity). Reference numeral 19 is a primary inverter control unit that controls the primary-side inverter unit 2. Reference numeral 23 is a welding current detector. The above is the control circuit portion of the consumable electrode type AC arc welding machine.

The operation will now be described. When the welding start signal (torch switch signal that turns on and off in synchronization with the torch switch) TS for starting welding is input to the arithmetic control unit 15, the welding current detection unit 12 confirms that there is no output current, and 2 The next inverter control unit 13 is instructed that the EN ratio is 0% regardless of the setting of the EN ratio setting unit 18, and the primary inverter control unit 19 is instructed to output a no-load voltage. At the same time, regardless of the setting of the welding current setting device 16, the wire 8 is moved to the base metal 10 by the slow-down wire feeding speed for smooth arc start.
Is supplied toward the contact and a welding current flows to generate a welding arc 9.

When the welding arc 9 is generated, the information on the presence of welding current is input to the arithmetic control unit 15 from the welding current detection unit 12 via the welding current detector 23. As a result, the arithmetic control unit 15 starts counting and sequentially calculates the EN ratio by E.
A command is output to the secondary inverter control unit 13 and the superposition circuit unit 14 so that the set value of the N ratio setting unit 18 is obtained. At the same time, the arithmetic control unit 15 inputs the arc short circuit determination signal A / S output from the arc short circuit detection unit 11, and when an arc is generated, the arithmetic control unit 15 previously set by the welding current setter 16 is set. The EP / EN signal stored in is corrected by the setting of the welding voltage setting unit 17 and the positive polarity ratio setting unit 18, and the EP / EN signal is output to the superposition circuit unit 14 and the secondary inverter control unit 13. If the arc short-circuit determination signal A / S is arc short-circuited, the EN ratio is 0% regardless of the setting of the positive polarity ratio setting device 18, that is, the EP / EN signal is set to EP only and the superposition circuit unit is set. 14 and the secondary inverter control unit 13 and a current command value for suppressing the welding output current I ₀ detected from the welding output current detection unit 12 via the welding current detector 23 and the output current at the time of arc short circuit And outputs an EP signal that does not exceed the current command value for suppression to the secondary inverter control unit 13.

A control method in the conventional consumable electrode type AC arc welding machine will be described below with reference to FIG. FIG. 8 is a control timing chart in the consumable electrode type AC arc welding machine. In FIG. 8, (a) is a positive polarity period output signal EN for outputting a positive polarity voltage from the secondary inverter unit 4 to make the welding wire 8 a negative polarity and the base material 10 a positive polarity, and in the period T ₁ . It becomes high level and becomes low level in other periods, and the secondary inverter control unit 13
From the positive polarity to the gate of the switching element QN. (B) is a reverse polarity period output signal EP for causing the secondary inverter unit 4 to output a reverse polarity voltage to make the welding wire 8 a positive polarity and the base material 10 a negative polarity.
_{At 2} it becomes high level, and at other periods it becomes low level and is supplied from the secondary inverter control unit 13 to the gate of the reverse polarity switching element QP. A period t _{1 in} which both the positive polarity period output signal EN and the reverse polarity period output signal EP are simultaneously at the low level, that is, after the positive polarity period output signal EN falls, the reverse polarity period output signal EP
Until rising edge and reverse polarity period output signal EP
Is a dead time until the positive-polarity period signal EN rises after the falling edge.

Now, the signal waveforms supplied from the arithmetic control unit 15 to the secondary inverter unit 4 via the secondary inverter control unit 13 and the superposition circuit unit 14 will be described with reference to FIGS. 9 and 10. FIG. 9 specifically shows the circuit configuration of the superposition circuit unit 14 in FIG. 7, while collectively showing the arithmetic control unit 15, the secondary inverter control unit 13, and the primary inverter control unit 19 as a control circuit unit 30. The welding current setting device 16, the welding voltage setting device 17, the positive polarity ratio setting device 18, and the arc / short-circuit detection unit 21 are omitted from the illustration, and are substantially the same as the circuit of FIG. 7. Reference numeral 31 indicates a torch switch.

The superposition circuit section 14 is a reverse polarity superposition circuit section 14
A and a positive polarity superposition circuit section 14B. The reverse polarity superimposing circuit section 14A includes a reverse polarity DC power supply E ₁ , a reverse polarity switching element Q _EP2 , a resistor R _P1 , a diode D _P1, and a smoothing capacitor C _P1 . In addition, the positive polarity superposition circuit unit 1
4B is composed of a reverse polarity DC power source E ₂ , a reverse polarity switching element Q _EN2 , a resistor R _N1 , a diode D _N1 and a smoothing capacitor C _N1 .

The control circuit section 30 applies the voltage V _QN1 to the positive polarity switching element Q _{EN1 of the} secondary inverter section 4 and the voltage V _{QP 1} to the reverse polarity switching element Q _EP1 . the voltage V _QN2 is applied for positive polarity superimposing circuit section 14B, is adapted to apply a voltage V _QP2 against reverse polarity superimposition circuit portion 14A. The points other than the above are the same as those of the circuit of FIG.

FIG. 10 is a timing chart showing the signal waveform of each part of FIG.
It is a chart, (a) is a welding output voltage V_OIndicates that
(B) is the welding output current I_OIs shown. (C),
(D), (e), (f) are reverse polarity switching elements Q
_EP1, Switching element Q for positive polarity_EN1, Reverse polarity switch
Switching element Q_EP2And positive polarity switching element Q
_{EN Two}Shows the on / off state of. (G) is for reverse polarity
Switching element Q_EP2Current I flowing through_P2Indicates (h)
Is the switching element Q for positive polarity_EN2Current I flowing through _N2To
Is shown. (I) is a smoothing capacitor C_EPOccur at both ends of
Voltage V_CP(J) is a smoothing capacitor C_ENBoth ends of
Generated voltage V_CNIs shown. T_EPIs the reverse polarity period
, T_ENIs the positive polarity period and T_PNIs both periods T_EPand
T_ENIs the sum of

The dead time is such that the positive polarity switching element Q _EN1 which outputs a positive polarity and the reverse polarity switching element Q _EP1 which outputs a reverse polarity are both non-conductive (O
FF state), in which both the positive polarity switching element Q _EN1 that outputs the positive polarity and the reverse polarity switching element Q _EP1 that outputs the reverse polarity due to the delay of the switching operation are in the conductive state. It is provided to prevent the switching elements Q _EN1 and Q _EP1 from being destroyed by being in the (ON state).

In FIG. 8, (c) is the same as (a) in FIG.
_Shows a welding output current I _O when the positive polarity period output signal EN and the reverse polarity period output signal EP as shown in (b) are applied to the gates of the positive polarity switching element Q _EN1 and the reverse polarity switching element Q _EP1 . (D) shows the arc / short circuit determination signal A / S output from the arc / short circuit detection unit 11. A is an arc signal and S is a short circuit signal.

From FIG. 8, the switching element Q for positive polarity is shown.
In the period (dead time) t _{1 to EN1} and switching element Q _{EP 1} for reverse polarity are both non-conductive state (OFF state), arc arc short-circuit detector 11 is misjudged the state of the consumable electrode type AC arc welder・ Short-circuit discrimination signal A /
S is set to the state of the short circuit signal S, so that at the time of polarity reversal, that is, at the time of switching from the positive polarity period to the reverse polarity period or from the reverse polarity period to the positive polarity positive period,
The short-circuit current suppression control (dip control) for canceling the short circuit operates to suppress the rising of the welding output current I _O and control the pulse current after the short circuit is cleared. This erroneous determination occurs because the welding output voltage V _O appearing at the output terminal 6 becomes zero during the dead time period t _{1 as in the} case of a short circuit.

The short-circuit current suppression control (dip control) for canceling the short-circuit operates not only when the polarity is reversed, but also when the output terminal 6 is short-circuited.
The operation of canceling the short circuit is performed, and the welding wire 8 and the base material 10 which is the object to be welded are contact-shorted to suppress the generation of spatter due to the rising of the current at the time of the short circuit, and the arc can be smoothly regenerated from the short circuit. It is a thing.

As described above, in the conventional consumable electrode type AC arc welding, the arc is extinguished each time the polarity of the welding arc is reversed,
Since the arc is generated again, at the time of polarity reversal, the arc / short circuit detection unit 11 can
By erroneously determining that the welding wire 8 and the base material 10, which is the object to be welded, are short-circuited by contact and outputting the short-circuit signal S, the short-circuit current suppression control (dip control) is driven, and the current rise at the time of polarity reversal is suppressed. As a result, it is difficult to smoothly reverse the polarity, and arc breakage often occurs, resulting in an unstable arc.

[0016]

In the conventional method for controlling the consumable electrode type AC arc welding machine described above, the arc / short circuit detecting section 11 welds when the welding arc is reversed in polarity, that is, when the arc is extinguished. Wire 8 and base material 10 which is the object to be welded
And the arc is being generated, the short circuit current suppression control (dip control) for canceling the short circuit operates at the time of polarity reversal because the contact short circuit is erroneously determined and the short circuit signal S is output. However, there is a problem in that the current rising is suppressed, smooth polarity reversal becomes difficult, arc breakage occurs frequently, and the arc becomes unstable.

An object of the present invention is to provide a control method for a consumable electrode type AC arc welder which can eliminate welding defects such as arc instability due to arc breakage during polarity reversal and can smoothly perform polarity reversal. Is.

[0018]

According to a first aspect of the present invention, there is provided a consumable electrode type AC arc welding machine control method, wherein a welding wire having a positive polarity is provided between a welding wire which is a consumable electrode and a base material which is an object to be welded. Arc welding is performed by applying an alternating voltage that alternately repeats the reverse polarity period and the positive polarity period in which the welding wire has a negative polarity with a dead time in between,
The welding output current is used to determine whether the welding wire is in contact with the base metal or a short circuit is generated from the voltage value appearing between the welding wire and the base metal, and to suppress the short-circuit current when it is determined to be a contact short circuit. It is characterized in that the determination result of the contact short circuit or the arc occurrence is forcibly fixed to the arc occurrence during the dead time and a predetermined delay time thereafter.

With the above construction, when the polarity of the AC voltage applied between the welding wire and the base material is reversed, the result of discrimination between contact short circuit and arc generation is given for a dead time and a predetermined delay time thereafter. Since it is forcibly fixed to the arc generation, it is erroneously determined that there is a contact short circuit between the welding wire and the base metal even though the arc is occurring, and as a result, the short circuit current suppression control (dip control) operates. Then, the rise of the current at the time of polarity reversal is not suppressed, and the current rise at the time of polarity reversal is made steep to shift to the pulse current, smooth polarity reversal becomes possible, and a stable arc can be generated.

According to a second aspect of the present invention, there is provided a method of controlling a consumable electrode type AC arc welding machine, wherein a reverse polarity period in which the welding wire has a positive polarity is provided between a welding wire which is a consumable electrode and a base material which is an object to be welded. Arc welding is performed by applying alternating voltage that alternates positive and negative polarities of the welding wire with a dead time in between. When the welding output current is controlled so as to suppress the short-circuit current when it is determined from the voltage value that appears between the welding wire and the base metal and when it is determined that there is a contact short circuit, between the dead time and the predetermined delay time that follows. It is characterized in that it retains the determination result of contact short circuit or arc occurrence immediately before the dead time.

With the above structure, when the polarity of the AC voltage applied between the welding wire and the base metal is reversed, a contact short circuit or an arc is generated immediately before the dead time during a dead time and a predetermined delay time thereafter. Since the determination result is retained, it is erroneously determined that it is a contact short circuit between the welding wire and the base metal even though the arc is being generated.
As a result, the short-circuit current suppression control (dip control) does not operate to suppress the rising of the current at the time of polarity reversal, and the current rises at the time of polarity reversal becomes steep and shifts to the pulse current, resulting in smooth polarity reversal. It becomes possible and a stable arc can be generated. Moreover, in the case where a contact short circuit occurs immediately before the polarity reversal, there is no inconvenience that the short circuit current suppression control (dip control) is stopped as soon as the dead time is reached.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram of a main circuit and a control circuit of a consumable electrode type AC arc welding machine according to a first embodiment of the present invention.
In FIG. 1, 1 is a power input terminal of an AC arc welding machine from a three-phase AC power source, 2 is a primary inverter part, 3 is a welding transformer, 4 is a secondary inverter part, 5 is a reactor for current limiting, 6 Is an output terminal of an AC arc welding machine, 7 is a contact tip for energization, 8 is a welding wire which is a consumable electrode fed from the contact tip 7 for energization, 9 is a welding arc, and 10 is a base material which is a workpiece. The above is the main circuit portion of the consumable electrode type AC arc welding machine in the present embodiment.

Reference numeral 12 is a welding output current detector for detecting the welding output current I _O for feedback control. 13
Is a switching element Q for the reverse polarity of the secondary side inverter unit 4.
_{EP1 is} a secondary inverter control unit that controls ON / OFF of the positive polarity switching element Q _EN1 . Reference numeral 14 is a superposition circuit unit for applying re-ignition superposition voltages V _EP and V _EN for smoothly performing polarity reversal. Reference numeral 15 denotes an arithmetic control unit for smoothly and appropriately executing each control. Reference numeral 16 is a welding current setting device, 17 is a welding voltage setting device, and 18 is a positive ratio setting device for setting a positive ratio (a ratio of a period in which the welding wire 8 as a consumable electrode has a negative polarity). Reference numeral 19 is a primary inverter control unit that controls the primary-side inverter unit 2. Reference numeral 20 denotes a dead time delay signal output control unit that sets the dead time delay signal X to a high level during the dead time and a predetermined delay time thereafter, and 21 indicates the magnitude of the welding output voltage V _O appearing at the output terminal 6. It is determined whether the welding wire 8 is in contact with the base material 10 to cause a short circuit or an arc is generated, and the arc / short circuit determination signal A / S is output, and the dead time delay signal of the dead time delay signal output control unit 20 is determined. It is an arc / short circuit detector that forcibly fixes the arc / short circuit determination signal A / S to the state of the arc signal A while X is at a high level. The above is the control circuit portion of the consumable electrode type AC arc welding machine in the present embodiment, in which the arc / short circuit detection unit 21 is the conventional arc / short circuit detection unit 11.
The difference from the conventional example is that the above is changed and that the dead time delay signal output control unit 20 is added. The dead time delay signal output control unit 20 instructs the secondary inverter control unit 13 and the superposition circuit unit 14 so that the arithmetic control unit 15 starts counting and the EN ratios are sequentially set to the set value of the EN ratio setting unit 18. When outputting the
Command is given from.

FIG. 2 is a block diagram showing a concrete structure of the arc / short circuit detector 21 and the dead time delay signal output controller 20. In FIG. 2, reverse polarity switching that performs reverse polarity output to the positive polarity output signal EN that is the drive signal of the positive polarity switching element Q _EN1 that performs positive polarity output of the secondary inverter unit 4 of the consumable electrode type AC arc welding machine. The reverse polarity output signal EP, which is a drive signal for the element Q _EP1 , is input to the dead time delay signal output control unit 20, and the dead time delay signal output control unit 20 outputs the dead time delay signal X.
Is output. Then, the arc / short circuit detection signal A / is obtained by the OR logic of the output dead time delay signal X and the logic element 21a of the welding output voltage V _O of the consumable electrode type AC welding machine.
Output S. That is, the welding output voltage V _O is the logic element 2
When it is higher than the input threshold value of 1a or when the dead time delay signal X is high level, the arc signal A (high level) is output, the welding output voltage V _O is lower than the input threshold value of the logic element 21a, and When the dead time delay signal X is low level, the short circuit signal S (low level) is output. In other words, the short-circuit signal S is output when the welding output voltage V _O is lower than the threshold value, the arc signal A is output when the welding output voltage V _O is higher than the threshold value, and the dead time delay signal X is at a high level (dead time and thereafter). (For a predetermined delay time), the arc / short circuit determination signal A / S is forcibly fixed to the state of the arc signal A.

FIG. 3 is a block diagram showing a specific configuration of the dead time delay signal output control section 20. In FIG. 3, 201 is a positive polarity output signal EN and a reverse polarity output signal E.
A logic element (NOR logic) that takes the NOR of P, 202
Is a delay circuit that delays the trailing edge of the output signal of the logic element 201 by setting a predetermined delay time. This logic element (NOR logic) 201 produces a logic result signal X ′ from the positive polarity output signal EN and the reverse polarity output signal EP. By passing this logic result signal X ′ through the delay circuit 202, the above-mentioned dead time delay signal X is output.

[0026]

[Table 1]

The operation of the consumable electrode type AC arc welding machine configured as described above will be described with reference to FIG. In FIG. 4, (a) is the same positive polarity period output signal EN as in FIG. 8 (a), and (b) is the same reverse polarity period output signal EP as in FIG. 8 (b). (C) is a dead time delay signal X, which has a high level during the sum of the positive period output signal EN and the reverse polarity period output signal EP both at low level t ₁ and the delay time t _X immediately thereafter, and The period is low level. 8D shows the welding output current I _O, which is compared with the welding output current I _O in FIG. 8C.
The rise and fall at the dead time are sharp. 8E shows the arc / short circuit determination signal A / S, which is continuously in the state of the arc signal A (high level) unlike the case of FIG. 8D. However, this waveform is subject to the condition that no contact short circuit has occurred.

First, the positive polarity switching element Q _EN1 that outputs positive polarity and the reverse polarity switching element Q _EP1 that outputs reverse polarity are both in a non-conducting state (OFF state) (dead time), that is, positive polarity. The dead time delay signal output control unit 20 creates a dead time delay signal X with a delay time t _X added during a period (dead time) t ₁ in which both the output signal EN and the reverse polarity output signal EP are at a low level, and this is generated. The dead time delay period T _X. The formula of the dead time delay period is shown below.

(Dead time delay period) = (dead time) + (delay time) That is, T _X = t ₁ + t _X (at the time of polarity reversal) In the above, not only the dead time but also the delay time t _X immediately thereafter. Also, the arc signal A is forcibly set, and the reason will be described. If an arc signal is used only during the dead time, an arc short circuit signal may be output when the dead time is switched due to a control error, that is, there is a possibility of an erroneous judgment.Therefore, a delay time is set and the arc judgment is performed during that time. To do.

During the dead time delay period T _X , the arc / short-circuit detecting portion 21 makes a short-circuit contact between the welding wire 8 and the base material 10 which is the object to be welded even though the arc is being generated. The arc / short circuit detection unit 21 outputs the short circuit signal S and outputs the short circuit signal S so that the short circuit current suppression control (dip control) does not operate and suppress the rising of the current at the time of polarity reversal. The short circuit detection signal A / S can be forcibly output the arc signal A, and the rising of the current at the time of polarity reversal can be made steep to instantly make a pulse current.

According to this embodiment, when the polarity of the AC voltage applied between the welding wire 8 and the base material 10 is reversed, during the dead time and the predetermined delay time that follows.
Since the determination result of the contact short circuit or the arc generation is forcibly fixed to the arc generation, it is erroneously determined to be the contact short circuit between the welding wire 8 and the base metal 10 even though the arc is being generated, As a result, the short-circuit current suppression control (dip control) does not operate to suppress the rising of the current at the time of polarity reversal, and the current rises at the time of polarity reversal becomes steep and shifts to the pulse current, resulting in smooth polarity reversal. It becomes possible and a stable arc can be generated.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.
FIG. 5 shows a specific configuration of the arc / short circuit detector 22.
In FIG. 5, V _O is a welding voltage, X is a dead time delay signal, A / S is an arc / short circuit detection signal, and the above is the same as the configuration of FIG. 2 is different from that shown in FIG. 2 in that the arc / short circuit detection unit 22 for outputting the arc / short circuit detection signal A / S includes a D flip-flop 22a and a logic element (A
This is because the ND logic) 22b and the logic element (OR logic) 22c are used so that the dead time and the predetermined delay time immediately thereafter follow the arc / short circuit state immediately before the polarity reversal. That is, the arc / short circuit detector 22 holds the state of the arc / short circuit determination signal A / S immediately before the polarity reversal during the dead time and the predetermined delay time immediately after that, and other configurations are the same. This is similar to the embodiment of FIG.

The operation of the arc / short circuit detector 11 constructed as described above will be described below with reference to FIG. In FIG. 6, (a) shows the dead time delay signal X, (b) shows the welding output voltage V _O , and (c).
Indicates the output signal Q of the D flip-flop 22a,
(D) shows the inverted output signal Q'of the logic element 22b,
(E) shows the arc / short circuit determination signal A / S.

To explain the operation, first, the welding output voltage V _O and the dead time delay signal X are supplied to the data input terminal D and the clock input terminal C of the D flip-flop 22a, respectively.
K and the D flip-flop 22a
Takes the output signal Q and the AND logic between the dead time delayed signal X by the logic element 22b, the OR logic by the logic element 22c results Q 'and the welding output voltage V _O of the AND logic, arc short-circuit detection in FIG. 6 As shown in the control timing chart of the part 21, when it is determined that the welding output voltage V _O is arcing immediately before the polarity reversal, the arc / short circuit detection signal A / is detected during the dead time and the delay time immediately after that. S is an arc state (state of arc signal S),
When it is determined that the output welding voltage V _O is short circuit immediately before the polarity reversal, the arc / short circuit detection signal A / S is set to the short circuit state (state of the short circuit signal S) for the same period. Note that M is a dead time, which is a period during which the welding output voltage V _O is zero.

As described above, the arc / short circuit determination signal A /
S is a D flip-flop 22a and logic elements 22b, 2
By using 2c, it is possible to conform to the arc / short circuit state immediately before the polarity reversal, that is, the state of the arc / short circuit determination signal A / S immediately before the polarity reversal can be held.
In other words, when the arc is generated immediately before the polarity reversal, the arc generation state is maintained, and when the arc is generated immediately before the polarity reversal, the short circuit state is maintained.

With the above structure, the welding wire 8 and the base material 10
When the polarity of the AC voltage applied during the reversal, the dead wire and the predetermined delay time that follows thereafter hold the determination result of contact short circuit or arc occurrence immediately before the dead time. Between the base metal 10 and the base material 10 is erroneously determined to be a contact short circuit even though the arc is being generated, and as a result, the short circuit current suppression control (dip control) operates to suppress the rise of the current at the time of polarity reversal. However, the current rises at the time of polarity reversal becomes steep and the current shifts to a pulse current, and smooth polarity reversal becomes possible and a stable arc can be generated. Moreover, in the case where a contact short circuit occurs immediately before the polarity reversal, there is no inconvenience that the short circuit current suppression control (dip control) is stopped as soon as the dead time is reached.

[0037]

According to the control method of the consumable electrode type AC arc welding machine according to the first aspect of the invention, the arc
Even though the short-circuit detector is generating an arc, the welding wire and the base metal, which is the workpiece, are erroneously determined to be a contact short-circuit, and a short-circuit signal is output and the current is controlled by the short-circuit current suppression control (dip control). Rise is suppressed, arc breakage occurs, polarity reversal becomes difficult and arc is not unstable, current rises sharply and instantly becomes pulse current, so smooth polarity reversal without arc breakage is possible, It is possible to realize a stable arc with good directivity.

According to the control method of the consumable electrode type AC arc welding machine as set forth in claim 2, the welding wire and the mother to be welded are in spite of the arc being generated in the arc / short circuit detection portion at the time of polarity reversal. Misjudging that the material is a contact short circuit,
Outputs a short circuit signal and controls short circuit current (dip control)
The current rise is suppressed, arc breakage occurs, polarity inversion becomes difficult and the arc does not become unstable, and the current rises sharply and instantly becomes a pulse current, so there is no arc breakage and smooth polarity reversal is possible. It is possible to realize a stable arc with good directivity. Moreover, in the case where a contact short circuit occurs immediately before the polarity reversal, there is no inconvenience that the short circuit current suppression control (dip control) is stopped as soon as the dead time is reached.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a consumable electrode type AC arc welding machine according to a first embodiment of the present invention.

FIG. 2 shows an arc according to the first embodiment of the present invention.
It is a block diagram which shows the specific structure of a short circuit detection part.

FIG. 3 is a block diagram showing a specific configuration of a dead time delay signal output control section in the first embodiment of the present invention.

FIG. 4 is a control timing chart of the consumable electrode type AC arc welding machine according to the first embodiment of the present invention.

FIG. 5 shows an arc according to a second embodiment of the present invention.
It is a block diagram which shows the specific structure of a short circuit detection part.

FIG. 6 is a control timing chart of an arc / short circuit detection signal by the consumable electrode type AC arc welding machine according to the second embodiment of the present invention.

FIG. 7 is a circuit block diagram showing a configuration of a conventional consumable electrode type AC arc welding machine.

FIG. 8 is a control timing chart of a conventional consumable electrode type AC arc welding machine.

FIG. 9 is a circuit diagram showing a configuration of a conventional consumable electrode type AC arc welding machine.

10 is a time chart of signals at various parts of the consumable electrode type AC arc welding machine of FIG.

[Explanation of symbols]

 1 Power input terminal for arc welding machine 2 Primary inverter section 3 Welding transformer 4 Secondary inverter section 5 Reactor 6 Output terminal for welding power source 7 Energizing contact tip 8 Welding wire which is a consumable electrode 9 Welding arc 10 Workpiece Base material 11 Arc / short-circuit detection unit 12 Welding current detection unit 13 Secondary inverter control unit 14 Superposition circuit unit 15 Calculation control unit 16 Welding current setting device 17 Welding voltage setting device 18 Positive polarity ratio setting device 19 Primary inverter control Part 20 Dead time delay signal output control part 21 Arc / short circuit detection part 21a Logic element 22 Arc / short circuit detection part 22a D flip-flop 22b Logic element 22c Logic element 23 Welding current detector 201 Logic element (NOR logic) 202 Delay circuit

Claims (2)

[Claims] 1. A dead period between a consumable electrode, a welding wire, and a base material, which is an object to be welded, is a reverse polarity period in which the welding wire has a positive polarity and a positive polarity period in which the welding wire has a negative polarity. Arc welding is performed by applying alternating voltage that alternates with time in between, and it appears between the welding wire and the base metal whether the welding wire is in contact with the base metal or short circuiting. A method for controlling a consumable electrode type AC arc welding machine, which determines a voltage value and controls a welding output current so as to suppress a short circuit current when it is determined that a contact short circuit occurs, wherein the dead time and a predetermined delay following the dead time. During the time
A control method for a consumable electrode type AC arc welding machine, characterized in that the determination result of contact short circuit or arc occurrence is forcibly fixed to the arc occurrence. 2. A dead polarity period in which the welding wire has a positive polarity and a positive polarity period in which the welding wire has a negative polarity are dead between a welding wire that is a consumable electrode and a base material that is a workpiece. Arc welding is performed by applying alternating voltage that alternates with time in between, and it appears between the welding wire and the base metal whether the welding wire is in contact with the base metal or short circuiting. A method for controlling a consumable electrode type AC arc welding machine, which determines a voltage value and controls a welding output current so as to suppress a short circuit current when it is determined that a contact short circuit occurs, wherein the dead time and a predetermined delay following the dead time. During the time
A method for controlling a consumable electrode type AC arc welding machine, characterized in that a result of determination as to whether a contact short circuit or an arc has occurred immediately before the dead time is held.