JP2003340574A - Control method for output voltage of welding power source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for output voltage of a welding power source device capable of setting an appropriate initial voltage setting value corresponding to the setting value of an EN ratio to adjust the arc voltage and the arc length immediately after arc start to an appropriate value, in AC pulse arc welding. <P>SOLUTION: In the AC pulse arc welding for welding by changing at least either a negative electric current of electrode or a negative term of electrode according to the setting value of the EN ratio, a previously set initial voltage setting value is made to be a setting voltage at the time of arc start, then, the setting voltage is corrected in every control cycle after the arc start, so that the detected value of a short circuit frequency between a welding wire and an object to be welded during welding can be substantially equal to the setting value of a predetermined short circuit frequency, thereby controlling the output voltage of the welding power source device. The function between the setting value of the EN ratio and the initial voltage setting value is previously set, and the initial voltage setting value corresponding to the setting value of the EN ratio is set according to the function to control the output. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to AC pulse arc welding using a welding robot, in which the detected value of the number of short circuits between the welding wire being welded and the object to be welded and the predetermined set value of the number of short circuits are substantially the same. The present invention relates to an improvement in an output voltage control method for controlling an output voltage of a welding power supply device for each control cycle so that the output voltage is equalized.

[0002]

2. Description of the Related Art In consumable electrode gas shielded arc welding,
By controlling the output voltage of the welding power source, the arc length, which has a significant influence on the welding quality, is maintained at an appropriate value. The reason for controlling the output voltage in this way is that it is difficult to directly detect the arc length, so that the arc length is indirectly controlled by controlling the output voltage that is in a substantially proportional relationship with the arc length. is there. However, when the object to be welded is aluminum or its alloy (hereinafter referred to as aluminum alloy etc.), the arc length and the output voltage may not be in a proportional relationship due to the effect of the cleaning action, as described later. Moreover, there are cases where the arc length cannot be maintained at an appropriate value by controlling the output voltage. In order to solve this problem, conventionally, in the welding of aluminum alloys, etc., the number of short circuits between the welding wire and the workpiece to be welded, which is in inverse proportion to the arc length, is used so that the number of short circuits becomes equal to the target value. By controlling the output voltage,
An output voltage control method that maintains the arc length at an appropriate value has been proposed. In the following, first, as the conventional technique 1, the above-described normal output voltage control method is described, and then the conventional technique 2 is described.
The output voltage control method based on the number of short circuits described above will be described.

[Prior Art 1] FIG. 1 is a block diagram of a welding apparatus for performing consumable electrode gas shielded arc welding using a welding robot. Hereinafter, description will be given with reference to FIG. The welder uses the teach pendant 9
Wire feeding speed to a robot controller 8 described later,
Welding conditions Ws such as output voltage and welding speed are set. The robot controller 8 outputs an operation control signal Ms for controlling the operation of the manipulator 7 described later, and from the wire feed speed setting signal, the voltage setting signal, the output start signal, etc. set by the teach pendant 9 described above. The formed interface signal If is transmitted to the welding power source device 6 described later. The manipulator 7 is equipped with the wire feed motor WM and the welding torch 4, and moves the tip position (TCP) of the welding torch 4 along a pre-teached motion locus according to the motion control signal Ms. The welding wire 1 is fed through the welding torch 4 by the wire feeding motor WM.

The welding power source device 6 receives the interface signal If and outputs an output voltage Vo corresponding to a voltage setting signal included therein. As a result, the arc 3 is generated between the welding wire 1 and the work piece 2 and the output current Io is conducted. Further, the welding power source device 6 outputs the feed control signal Fc to control the wire feed motor WM.

In the following description, as an example of the consumable electrode gas shield arc welding method, an AC pulse arc welding method which is often used for welding aluminum alloys and the like will be described. FIG. 2 is a current / voltage waveform diagram of AC pulse arc welding. The same figure (A) shows the time change of the output current Io, the same figure (B) shows the time change of the output voltage Vo, and the same figure (C1)-(C4) shows the arc generation state at each time. In the figure, EN represents the negative polarity of the electrode that carries the output current Io from the work piece side in the welding wire direction, and EP represents the positive electrode that carries the output current Io from the welding wire side in the work piece direction. Shows polarity. Hereinafter, description will be given with reference to FIG.

A period from time t1 to t2 (peak period T
p) As shown in (A) of the same figure, with the electrode plus polarity EP, a predetermined peak current Ip is conducted during a predetermined peak period Tp. Normally, the values of the peak period Tp and the peak current Ip are set so that the welding wire is transferred by one pulse per droplet by arc heat. The value is about 1 to 3 [ms] in the peak period Tp, and about 300 to 550 [A] in the peak current Ip. Further, as shown in FIG. 3B, the peak voltage Vp corresponding to the energization of the peak current Ip is applied between the welding wire (+) and the object to be welded (-).

Period between Times t2 and t3 (Electrode Minus Period Ten) At time t2, when the electrode positive polarity EP is switched to the electrode negative polarity EN, as shown in FIG.
A predetermined electrode negative current Ien is applied during a predetermined electrode negative period Ten. Usually, the values of the electrode minus period Ten and the electrode minus current Ien are
Depending on the material, plate thickness, shape, etc. of the object to be welded, it is set to an appropriate value within the range in which droplet transfer does not occur. The value is about 1 to 10 [ms] in the electrode minus period Ten, and about 30 to 120 [A] in the electrode minus current Ien. Further, as shown in FIG. 7B, the electrode negative voltage Ven corresponding to the energization of the electrode negative current Ien is applied between the welding wire (−) and the object to be welded (+).

A period from time t3 to t4 (base period T
b) At time t3, when the electrode minus polarity EN is switched again to the electrode plus polarity EP, as shown in FIG. 7A, within the range in which droplets are not transferred during the base period Tb (20 to 70 [A ]), A predetermined base current Ib is energized. Further, as shown in FIG.
The base voltage Vb corresponding to the energization of the above base current Ib
Is applied between the welding wire (+) and the object to be welded (-). The base period Tb is automatically determined by the modulation control shown below. That is, as shown in FIG. 7B, at the end point (time t4) of the base period Tb, the integrated value Iv of the error between the output voltage Vo during the electrode plus polarity EP period and the predetermined voltage setting value Vs. However, it is the time when it becomes 0 [V]. In the case of the figure, the output voltage Vo in the electrode plus polarity EP period includes the peak voltage Vp in the peak period Tp and the base voltage Vb in the base period Tb described above. Therefore, the integrated value Iv1 of the error between the peak voltage value Vp during the peak period Tp and the above voltage setting value Vs =
∫ (Vp-Vs) dt, the integral value Iv2 of the error between the base voltage value Vb during the base period Tb and the above voltage setting value Vs.
= ∫ (Vb-Vs) dt, the end time of the base period Tb (time t
4) is decided. Iv = ∫ (Vp−Vs) dt + ∫ (Vb−Vs) dt = 0 (1) Expression After time t4, the operations of the above items 1 to 4 are repeated as one cycle to perform welding.

Arc Generation State in Each Period As described above, as shown in (C1) of FIG.
The inside of the welding wire 1 is promoted to be melted by energization of the peak current Ip having a large current value, and the droplet 1a grows large. At this time, the cathode spot of the arc 3 is the work piece 2 whose oxide film has not been removed by the cleaning action.
Formed on the surface of. Next, as shown in (C2) of the same figure, in the latter half of the peak period Tp in the above item, the pinch force due to the conduction of the peak current Ip causes a constriction in the upper portion of the droplet 1a.

Further, as shown in (C3) of the figure, the peak period Tp of the above term ends, and the electrode plus polarity EP
Immediately after the time t2 when the electrode is switched to the electrode minus polarity EN, the droplet 1a is separated from the welding wire 1 and is transferred to the welded object 2. Immediately before this droplet transfer, the droplet 1a and the workpiece 2 may come into contact with each other, causing a short circuit between the welding wire 1 and the workpiece 2. The frequency of occurrence of this short circuit (the number of short circuits per unit time) increases as the shortest distance (arc length) between the tip of the welding wire 1 and the work piece 2 decreases, and decreases as it increases. It is in. Further, as shown in (C4) of the figure, during the electrode minus period Ten of the above item, the droplet gradually grows by the energization of the electrode minus current Ien. Since the cathode spot of the arc 3 at this time is formed while moving at high speed in the entire droplet and the lower unmelted portion of the welding wire 1, the arc 3 is formed from the droplet and the entire lower portion of the welding wire 1. Occur. As shown in the above figures (C1) to (C4), welding is performed by repeating the processes of forming, growing, and transferring droplets.

FIG. 3 is a block diagram of a welding power supply device for carrying out the above-mentioned AC pulse arc welding. Hereinafter, each circuit block will be described with reference to FIG.
The commercial power source AC is an input power source for the welding power source device, and normally three-phase 200/220 [V] is used. The output control circuit INV, whose internal circuit is not shown, has a primary side rectifying circuit for rectifying the commercial power source AC, a smoothing circuit for smoothing the rectified rippled voltage, and a smoothed direct current. An inverter circuit that converts a voltage into a high-frequency alternating current, a drive circuit of a plurality of sets of power transistors that form the inverter circuit, and a PWM that performs PWM control of the inverter circuit according to a current error amplification signal Ei described later.
And a control circuit.

The high frequency transformer INT steps down the high frequency alternating current to a voltage value suitable for an arc load. The secondary side rectifiers D2a to D2d rectify the stepped down high frequency alternating current into direct current. The polarity switching drive circuit DR outputs an electrode minus polarity drive signal Ndr (Hi when an electrode minus period signal Ten described later is input (High level).
GH level) and no signal is input (Low level), the electrode plus polarity drive signal Pdr is output (High level).
h level). Therefore, when the electrode minus polarity drive signal Ndr is output, the electrode plus polarity drive signal Pdr is not output, and conversely, when the electrode minus polarity drive signal Ndr is not output, the electrode plus polarity drive signal Pdr is Outputs are logically inverted from each other. The electrode positive polarity transistor PTR becomes conductive when the electrode positive polarity drive signal Pd is output, and the electrode positive polarity period is started. Also, the electrode minus polarity transistor NT
R becomes conductive when the above-mentioned electrode minus polarity drive signal Ndr is being output, and is in the electrode minus polarity period.

A polarity switching circuit SWP is formed by the polarity switching drive circuit DR, the electrode plus polarity transistor PTR and the electrode minus polarity transistor NTR. The polarity switching circuit SWP switches the DC output (outputs of the secondary side rectifiers D2a to D2d) of the power supply device to the electrode negative polarity when the electrode negative period signal Ten is input (High level) and is input. Not (Low
Level), the DC output of the power supply device is switched to the positive electrode polarity.

The reactor WL smoothes the rippled output that is supplied to the electrode positive polarity transistor PTR or the electrode negative polarity transistor NTR and supplies it to the arc 3. The peak current Ip and the base current Ib during the electrode plus polarity period described above with reference to FIG. 2 are D2a or D2b.
→ PTR → WL → welding wire 1 → welding object 2 is energized in the route. Further, the electrode minus current Ien during the electrode minus polarity period is as follows: Workpiece 2 → Welding wire 1 → WL → NT
Electricity is energized through the route of R → D2c or D2d.

The welding wire 1 is fed through the welding torch 4 by the feeding roll 5a of the wire feeding device, and is fed from the contact tip at the tip of the welding torch 4 to be welded to the object 2 to be welded. An arc 3 is generated between them.

The peak period timer circuit TP outputs a peak period signal Tp which is at a high level for a predetermined fixed period when a reset signal Cp (described later) is input (high level). Electrode minus period timer circuit TE
When the peak period signal Tp changes from the High level to the Low level, N is H for a predetermined fixed period.
The electrode minus period signal Ten that is at the high level is output.

The voltage detection circuit VD detects the output voltage Vo and outputs a voltage detection signal Vd. As described above in the description of FIG. 1, the voltage setting signal Vs transmitted from the robot controller 8 as a part of the interface signal If after being set by the teach pendant 9 is the voltage during the electrode plus polarity period ( It becomes the target value of the average value of the peak voltage Vp and the base voltage Vb) described above with reference to FIG. The voltage error circuit EV performs the above error calculation of (voltage detection signal Vd-voltage setting signal Vs) and outputs a voltage error signal Ev. The integrating circuit IV, when the electrode minus period signal Ten described above is not input (Low level),
The above voltage error signal Ev is integrated to output an integrated value signal Iv. In the above description, when the electrode minus period signal Ten is not input is during the electrode plus polarity period. Therefore, the integration circuit IV described above has Iv = ∫ (Vd−Vs) dt = ∫ (Vp shown in the above-mentioned equation (1).
The integration of −Vs) dt + ∫ (Vb−Vs) dt is performed. In the comparison circuit CP, the integrated value signal Iv is 0 [V].
Then, the reset signal Cp that becomes High level for a short time is output. The reset signal Cp is input to the above-described peak period timer circuit TP and becomes a trigger signal for starting the output of the peak period signal Tp.

The voltage error circuit EV and the integration circuit IV described above
Then, the modulation circuit MC is formed by the comparison circuit CP and performs the following processing corresponding to the above-mentioned expression (1). That is, the modulation circuit MC peaks when the integrated value Iv of the error between the voltage detection signal Vd and the voltage setting signal Vs in the electrode plus polarity period from the output start time of the peak period signal Tp becomes 0 [V]. The period timer circuit TP outputs a reset signal Cp which is a trigger signal for starting output again.

The peak current setting circuit IP outputs a peak current setting signal Ip which has a predetermined value for causing droplet transfer. The electrode minus current setting circuit IEN outputs a predetermined electrode minus current setting signal Ien to a value that does not cause droplet transfer. The base current setting circuit IB has a base current setting signal Ib which is preset to a value that does not cause droplet transfer.
Is output. When the above-mentioned peak period signal Tp is input (High level), the peak period switching circuit SP switches to the a side and outputs the above peak current setting signal Ip as the current control setting signal Isc, which is input. If not (Low level), it switches to the b side and outputs the switching setting signal Se described later as the current control setting signal Isc.
The electrode minus period switching circuit SE switches to the side a when the electrode minus period signal Ten described above is input (High level), and outputs the electrode minus current setting signal Ien as the switching setting signal Se for input. When it is not turned on (Low level), it switches to the b side and outputs the base current setting signal Ib as the switching setting signal Se. A current control setting circuit ISC is formed by the peak period switching circuit SP and the electrode minus period switching circuit SE, and the processing is as follows. That is,
The current control setting circuit ISC receives the peak current setting signal Ip when the peak period signal Tp is input, and receives the electrode negative current setting signal Ien when the electrode negative period signal Ten is input.
When neither of the period signals Tp and Ten is input, the base current setting signal Ib is output as the current control setting signal Isc.

The current detection circuit ID detects an alternating output current Io, converts the value into an absolute value, and outputs a current detection signal Id. The current error amplification circuit EI amplifies the error between the current detection signal Id and the current control setting signal Isc and outputs the current error amplification signal Ei. The output control circuit INV described above controls the energization value of the output current Io according to the current error amplified signal Ei. Therefore, Isc =
The peak current Ip is conducted when Ip, the electrode minus current Ien is conducted when Isc = Ien, and the base current Ib is conducted when Isc = Ib.

FIG. 4 is a timing chart of each signal in the welding power source device 6 of the prior art 1 described above. The same figure (A) shows the time change of the output current Io, the same figure (B) shows the time change of the output voltage Vo, the same figure (C) shows the time change of the peak period signal Tp, and the same figure (D). ) Shows a time change of the electrode minus period signal Ten, (E) shows a time change of the integrated value signal Iv, and (F) shows a time change of the reset signal Cp. 2A and 2B are the same as FIG. 2 described above. Hereinafter, description will be given with reference to FIG.

Period from time t1 to t2 (peak period T
p) As shown in (D) of the same figure, since the electrode minus period signal Ten is not output during this period (Low level), the electrode has a positive polarity EP. Further, as shown in FIG. 7C, the peak period signal Tp is output (High level), so that the peak current Ip is conducted as shown in FIG. Further, as shown in FIG. 7E, the integrated value signal Iv has the peak voltage V shown in FIG.
Iv = ∫ (Vp-V depending on p and the voltage setting signal Vs
s) The integrated value of dt. At this time, since Vp> Vs, the integrated value increases with the passage of time.

Period between Times t2 and t3 (Electrode Minus Period Ten) As shown in FIG. 6D, during this period, the electrode minus period signal Ten is output (High level), so the electrode minus polarity EN Therefore, as shown in FIG. 7A, the electrode minus current Ien is applied. Further, as shown in FIG. 7E, the electrode minus period signal Ten
Is output, the integration process is stopped, and the integrated value signal Iv does not change during this period.

A period of time t3 to t4 (base period T
b) As shown in FIG. 6D, since the electrode minus period signal Ten is not output during this period (Low level), the electrode plus polarity EP is obtained again. In addition, the same figure (C)
Since neither the peak period signal Tp shown in FIG. 6 nor the electrode minus period signal Ten shown in FIG. 9D is output (Low level), as shown in FIG.
b is energized. Further, as shown in FIG. 7E, the integrated value signal Iv is Iv = ∫ (Vb−Vs) dt depending on the base voltage Vb and the voltage setting signal Vs shown in FIG.
Is the integral value of. At this time, since Vb <Vs, the integrated value becomes smaller with the passage of time and becomes 0 [V] at time t4. When the integrated value signal Iv becomes 0 [V], the reset signal Cp becomes High level for a short time as shown in FIG. 6F, and as a result, the output of the peak period signal Tp shown in the above section is started again. .

As described above, in the prior art 1, the arc length is controlled by controlling the output voltage so that the average value of the peak voltage Vp and the base voltage Vb during the electrode plus polarity period becomes equal to the voltage setting value Vs. It can be maintained at an appropriate value.

[Prior Art 2] As described above, when the output voltage and the arc length are in a proportional relationship, the arc length can be maintained at an appropriate value by the above-described output voltage control method of the prior art 1. . However, in arc welding of an aluminum alloy or the like, the output voltage and the arc length are not in a proportional relationship for the following reason, and thus the output voltage control method of the conventional technique 1 cannot maintain the arc length at an appropriate value. The reason for this will be described below with reference to FIG.

FIG. 5 is a view showing an arc generation state in arc welding of aluminum alloy or the like. Same figure (A)
Shows the case where the cleaning width Wc1 [mm] showing the removal range of the oxide film on the surface of the workpiece by the arc is narrow, and FIG. 6B shows the case where the cleaning width Wc2 [mm] is wide.
Further, in the figure, the welding wire 1 serves as an anode, and the workpiece 2
Is the cathode plus the polarity. Hereinafter, description will be given with reference to FIG.

Usually, the cathode spot of the arc 3 is formed in a region where an uncleaned oxide film exists, which easily emits electrons. Therefore, as shown in FIG. 3A, an anode is formed at the tip A of the welding wire 1 and a cathode is formed around the outer periphery B of the cleaning area. Therefore, the distance Lt1 [mm] between the points A and B becomes the true arc length. Further, the distance La1 [mm] between the tip A of the welding wire and the point C on the workpiece directly below the welding wire is
It becomes the apparent arc length. The arc length in the above description is the apparent arc length. The true arc length Lt1 is proportional to the output voltage, and the apparent arc length La1 is not proportional to the output voltage. Therefore, in the above-described output voltage control method of the related art 1, the true arc length is maintained at a constant value. But,
Welding qualities such as penetration depth and bead appearance are greatly affected by the apparent arc length La1 and are less affected by the true arc length. That is, in order to obtain good welding quality, it is necessary to maintain the apparent arc length at an appropriate value.
By the way, in the arc welding of steel, the cathode spot is formed around the point C where the arc path is the shortest. Therefore, the true arc length Lt1 and the apparent arc length La1 become substantially equal. For this reason, controlling the true arc length by the output voltage control method of the prior art 1 simultaneously controls the apparent arc length.

The surface condition (dirt, etc.) of the object to be welded during welding,
The cleaning width Wc of the object to be welded changes greatly depending on the shielding state of the shield gas and the temperature of the object to be welded accompanying the progress of welding. During the welding, the cleaning width changes from the cleaning width Wc1 [mm] shown in FIG.
When the cleaning width Wc2 [mm] shown in is increased, the arc generation state changes as follows. That is, as shown in FIG. 7B, the cathode spot is formed around the outer peripheral point E of the cleaning area. At this time, as described above,
The true arc length (point D-point E) becomes Lt1 [mm], which is the same value as in FIG.
As a result, as apparent from the geometrical positional relationship, the apparent arc length is shortened to La2 [mm]. Contrary to the above, when the cleaning width becomes narrow during welding, the apparent arc length becomes long.

As described above, in the arc welding of aluminum alloy or the like, in the output voltage control method of the prior art 1, the apparent arc length changes with the variation of the cleaning width during welding, and the welding quality deteriorates. There was a problem. In order to solve this problem, an output voltage control method according to the number of short circuits of the prior art 2 described below has been proposed. That is, in the output voltage control method of the prior art 2,
As described above in the description of FIG. 2, by utilizing the fact that the frequency of short circuits (the number of short circuits per unit time) occurring immediately before the droplet transfer and the apparent arc length are in inverse proportion,
This is a method of maintaining the apparent arc length at an appropriate value by controlling the output voltage so that the number of short circuits becomes equal to the target value. Prior art 2 will be described below with reference to the drawings.

FIG. 6 is a block diagram of a welding frequency control welding power source device 61 for implementing the output voltage control method of the prior art 2. In the figure, the same circuit blocks as those in FIG. 3 described above are designated by the same reference numerals, and their description will be omitted. Hereinafter, the short circuit number detection circuit ND, the short circuit number setting circuit NS, the short circuit number error integrating circuit ENI, and the initial voltage setting circuit VS1 shown by the dotted line which are circuit blocks different from FIG. 3 will be described.

The short circuit frequency detection circuit ND has a voltage detection signal V
A short circuit is determined based on the voltage value of d, the number of short circuits in a predetermined control cycle Tc [s] is counted, and a short circuit count detection signal Nd is output. The short circuit number setting circuit NS receives the interface signal If including the short circuit number setting value set by the teach pendant 9 described above with reference to FIG. 1, and outputs the short circuit number setting signal Ns. Therefore, the short circuit number setting signal Ns is set by the teach pendant. The initial voltage setting circuit outputs a predetermined initial voltage setting signal Vs1 immediately after the start of the arc until the end of the control cycle Tc [s]. The short-circuit number error integration circuit ENI receives the short-circuit number detection signal Nd and the short-circuit number setting signal Ns as inputs, performs the following formula, and outputs the voltage control setting signal Vsc. Vsc = Vs1 + G × ∫ (Nd−Ns) (2) where G is a predetermined amplification factor. In the calculation of the above formula (2), G × (Nd−N) is obtained for each control cycle Tc [s].
s) is calculated and integrated, and added to the initial voltage setting signal Vs1 to calculate the voltage control setting signal Vsc. This control cycle Tc
Is set to about 1 [s] in the steady state. Since the operation thereafter is the same as that in the case of FIG. 3 described above, description thereof will be omitted. As described above, in Conventional Technique 2, the short circuit number setting signal Ns corresponding to the appropriate value of the apparent arc length is set so that the short circuit number detection signal Nd during welding is substantially equal to the short circuit number setting signal Ns. , Controls the output voltage of the welding power supply.

[0033]

In the above-mentioned prior art 2, the following problems will be explained regarding the setting of the initial voltage set value Vs1 and the EN ratio En. First, if the ratio of the average electrode minus current to the average welding current calculated from the absolute value of the output current Io in one cycle of AC shown in FIG. 2 is defined as the EN ratio En, it is expressed by the following formula. En = {| electrode minus current Ien × electrode minus period Ten | / (peak current Ip × peak period Tp + base current Ib × base period Tb + | electrode minus current Ien × electrode minus period Ten |) × 100 (3) formula

In the AC pulse arc welding, during the electrode minus period, the cathode spots irregularly move on the surface of the welding wire, and the arc easily rises upward, so that the arc heat is effectively utilized. As a result, the melting speed of the welding wire becomes faster in the electrode minus period than in the electrode plus period. Therefore, when the EN ratio En is increased to increase the negative period of the electrode, the melting speed of the welding wire is increased,
In order to make the arc length constant, as shown in FIG. 7, the average welding current calculated from the absolute value of the output current Io decreases. FIG. 7 is a diagram showing an average welding current [A] (vertical axis) when the EN ratio En [%] (horizontal axis) is changed,
The material is aluminum alloy A5356 and the diameter is 1.2.
Welding wire of [mm], wire feeding speed is 1.2 [m
/ Min] and 0.8 [m / min]. As a result, since the average welding current and the arc voltage are in a substantially proportional relationship, as shown in FIG.
Increasing n will decrease the arc voltage.
FIG. 8 is a diagram showing the arc voltage [V] (vertical axis) when the EN ratio En [%] (horizontal axis) is changed, and the material of the wire and the wire feeding speed are the same as those in FIG. 7 described above. Is.

In AC pulse arc welding, usually E
The N ratio En is set in the range of 0 [%] to 40 [%]. When the EN ratio En is fixed and the average welding current is changed, the relationship between the average welding current and the wire feeding speed is represented by a straight line, as shown in FIG. FIG. 9 shows the EN ratio E
It is a figure which shows wire feed speed [m / min] when n is fixed to each of 0 [%]-40 [%] and average welding current [A] (horizontal axis) is changed, The case where the material is aluminum alloy A5356 and the welding wire having a diameter of 1.2 [mm] is fed is shown.

Usually, in the above-mentioned initial voltage setting circuit VS1, the welding voltage determined from the wire feeding speed corresponding to the average welding current when the EN ratio En is fixed at 20% is set as the initial voltage setting value Vs1. Is set. Therefore, when the EN ratio En is set to, for example, 40 [%] during the welding operation, the arc voltage decreases as shown in FIG. However, since the arc voltage when the EN ratio is 20 [%] is set as the initial voltage set value Vs1, this initial voltage set value Vs1 is set higher than the desired voltage set value. Therefore, it is necessary to set the gain G in the equation (2) for obtaining the above voltage control setting signal Vsc to a large value to speed up the responsiveness of voltage adjustment of the welding power source device.

On the other hand, at the time of main welding, the short-circuiting of the droplets is random, so that the number of short-circuits per control cycle Tc changes even if the arc length is constant. Therefore, when the responsiveness of the voltage adjustment of the welding power source device is set early, the welding voltage is adjusted even when stable welding is performed, and due to changes in the welding conditions, the welding voltage changes as shown in FIGS. As shown, the arc voltage and the arc length are likely to fluctuate, and the voltage adjustment of the welding power source device becomes unstable. Figure 1
0 and FIG. 11 are diagrams showing the time changes of the arc voltage and the arc length when the responsiveness of the voltage adjustment of the welding power source device is set quickly, and the EN ratio En is 40 [%] and the material is aluminum alloy. A5356 with a diameter of 1.2 [m
m] welding wire with a wire feed rate of 1.2 [m / mi
n].

According to the present invention, in the AC pulse arc welding, an appropriate initial voltage setting value corresponding to the setting value of the EN ratio En can be set so that the arc voltage and the arc length immediately after the arc start can be set to appropriate values. An object of the present invention is to provide a method for controlling an output voltage of a welding power source device.

[0039]

In order to achieve the above-mentioned object, the invention according to claim 1 is to transfer droplets in an electrode plus polarity EP in which an output current Io is energized from the welding wire side in the direction of the object to be welded. An electrode minus polarity EN that energizes a pulse current composed of a peak current Ip of a peak period Tp to be performed and a base current Ib of a base period Tb in which droplet transfer is not performed, and energizes an output current Io from the workpiece side in the welding wire direction
Then, the electrode minus current Ien of the electrode minus period Ten in which the droplets are not transferred is applied, and the EN ratio En = {| electrode minus current Ien × electrode minus period Ten | / (peak current Ip × peak period Tp + base current Ib × base Period Tb + | electrode minus current Ien × electrode minus period Ten
|) × 100 The set value of the electrode minus current I
In AC pulse arc welding in which at least one of en and the electrode minus period Ten is changed and welded, a preset initial voltage setting value is set as a set voltage at the time of arc start, and a welding wire 1 is being welded after the arc start. Output voltage for controlling the output voltage of the welding power source device by correcting the set voltage for each control cycle so that the detected value of the number of short circuits between the welding target 2 and the welded object 2 becomes substantially equal to the preset value of the number of short circuits. In the control method, a function of the set value of the EN ratio En and the initial voltage set value is predetermined, and the output is controlled by setting the initial voltage set value corresponding to the set value of the EN ratio En according to the function. This is a method for controlling the output voltage of the welding power supply device.

According to the second aspect of the present invention, the welding condition is set by the teach pendant 9 and the AC pulse arc welding is performed by using the welding power supply device and the welding robot. The EN ratio setting from the teach pendant 9 is performed. The EN ratio En is set by the signal, and the initial voltage set value corresponding to the set value of the EN ratio En is set according to a predetermined function of the set value of the EN ratio En and the initial voltage set value, and the output is output. The method for controlling an output voltage of a welding power source device according to claim 1, wherein the method is controlled.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 12 is a block diagram of an initial voltage setting variable welding power supply device for carrying out the output voltage control method of the welding power supply device of the present invention. In the figure, the same circuit blocks as those in FIG. 6 described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, the EN ratio setting circuit ENS and the initial voltage control setting circuit VC indicated by the dotted line different from FIG. 6 will be described.

The EN ratio setting circuit ENS has an EN ratio E set by the teach pendant 9 described above with reference to FIG.
The interface signal If including n is input to EN.
The ratio setting signal En is output. The value of the EN ratio En is set to an appropriate value by the teach pendant 9 according to the material of the object to be welded, the welding speed, the welding posture, the shape of the welded joint, or the welding point.

The initial voltage control setting circuit VC includes, for example,
A function of the EN ratio En and the initial voltage setting value shown in FIG. 13 is incorporated, and the EN ratio setting signal En is input, and an appropriate initial voltage setting value is selected from the functions of the EN ratio En and the initial voltage setting value. Then, the initial voltage control setting signal Vc is output. FIG. 13 shows the EN ratio En [%] (horizontal axis).
FIG. 3 is a diagram showing an example of a relationship between the initial voltage setting value [V] (vertical axis) and a welding wire having a material of aluminum alloy A5356 and a diameter of 1.2 [mm] and a wire feeding speed of 1.
The case of feeding at 2 [m / min] is shown.

The short circuit number error integrating circuit ENI receives the above initial voltage control setting signal Vc, the short circuit number detection signal Nd and the short circuit number setting signal Ns as input, and performs the calculation of the following equation,
The voltage control setting signal Vsc is output. Vsc = Vc + G × ∫ (Nd−Ns) (4) where G is a predetermined amplification factor. In the calculation of the above formula (4), G × (Nd−N) is obtained for each control cycle Tc [s].
s) is calculated and integrated, and added to the initial voltage control setting signal Vc to calculate the voltage control setting signal Vsc.

As a result, when the EN ratio En is set by the teach pendant, the initial voltage control setting circuit VC
Selects an appropriate initial voltage setting value from the function of the EN ratio En and the initial voltage setting value and outputs it as the initial voltage control setting signal Vc, which is input to the modulation circuit MC. Therefore, an appropriate initial voltage setting value corresponding to the EN ratio En is set, so that the arc voltage and the arc length immediately after the arc start can be set to appropriate values, as shown in FIGS. 14 and 15. In addition, since the voltage control response of the welding power supply device is not accelerated, it hardly reacts to irregular short circuits other than disturbances, and fluctuations in the arc voltage and arc length during main welding are reduced, resulting in less disturbance. It is possible to maintain the arc length constant by adjusting the arc voltage with an appropriate responsiveness. FIG. 14 and FIG. 15 are diagrams respectively showing changes with time of the arc voltage and the arc length of the method for controlling the output voltage of the welding power source device of the present invention. A welding wire with a diameter of 1.2 [mm] has a wire feeding speed of 1.
The case of feeding at 2 [m / min] is shown.

Although the present invention has been described with respect to the case of welding an aluminum alloy, the present invention is not limited to the aluminum alloy and can be applied to the case of welding other metals such as iron and copper.

[0047]

INDUSTRIAL APPLICABILITY The present invention provides an appropriate initial voltage setting value corresponding to the setting value of the EN ratio En from the predetermined function of the setting value of the EN ratio En and the initial voltage setting value in AC pulse arc welding. Can be selected and set as the initial voltage control set value, the arc voltage and arc length immediately after the arc start can be set to appropriate values. In addition, since the voltage control response of the welding power supply device is not accelerated, it hardly reacts to irregular short circuits other than disturbances, and fluctuations in the arc voltage and arc length during main welding are reduced, resulting in less disturbance. It is possible to maintain the arc length constant by adjusting the arc voltage with an appropriate responsiveness.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a consumable electrode gas shielded arc welding apparatus using a welding robot.

FIG. 2 is a current / voltage waveform diagram of AC pulse arc welding.

FIG. 3 is a block diagram of an AC pulse arc welding power supply device of prior art 1.

FIG. 4 is a timing chart of a welding power supply device according to Related Art 1.

FIG. 5 is a diagram showing an arc generation state of an aluminum alloy or the like.

FIG. 6 is a block diagram of a welding power supply device according to Related Art 2.

FIG. 7 is a diagram showing an average welding current [A] (vertical axis) when the EN ratio En [%] (horizontal axis) is changed.

FIG. 8 is a diagram showing an arc voltage [V] (vertical axis) when a ratio En [%] (horizontal axis) is changed.

FIG. 9 shows the wire feeding speed [m / min] when the ratio En is fixed to each of 0% to 40% and the average welding current [A] (horizontal axis) is changed. It is a figure.

FIG. 10 is a diagram showing a time change of the arc voltage when the responsiveness of voltage adjustment of the welding power source device is set early.

FIG. 11 is a diagram showing changes over time in the arc length when the responsiveness of voltage adjustment of the welding power supply device is set fast.

FIG. 12 is a block diagram of an initial voltage setting variable welding power supply device for carrying out the output voltage control method of the welding power supply device of the present invention.

FIG. 13 is a diagram showing an example of a relationship between an EN ratio En [%] (horizontal axis) and an initial voltage setting value [V] (vertical axis).

FIG. 14 is a diagram showing changes over time in the arc voltage of the method for controlling the output voltage of the welding power source device of the present invention.

FIG. 15 is a diagram showing changes over time in the arc length of the output voltage control method for the welding power source device of the present invention.

[Explanation of symbols]

1 welding wire 1a Droplet 2 Objects to be welded 3 arc 4 welding torch 5a Feeding roll of wire feeding device 6 Welding power supply 61 Short-circuit control welding power supply device 62 Initial voltage setting variable welding power supply device 7 Welding robot (manipulator) 8 Robot controller 9 Teach pendant AC commercial power supply CP comparison circuit Cp reset signal D2a ~ D2d Secondary side rectifier DR polarity switching drive circuit EI current error amplifier circuit Ei Current error amplification signal EN electrode negative polarity En EN ratio (setting signal) ENI Short circuit count error integration circuit ENS EN ratio setting circuit EP electrode plus polarity EV voltage error circuit Ev voltage error signal Fc feed control signal G amplification factor IB base current setting circuit Ib base current (setting signal) ID current detection circuit Id current detection signal IEN Electrode negative current setting circuit Ien negative electrode current (setting signal) If interface signal INT high frequency transformer INV output control circuit Io output current IP peak current setting circuit Ip peak current (setting signal) ISC current control setting circuit Isc current control setting signal IV integration circuit Iv integral value (signal) La apparent arc length Lt True arc length MC modulation circuit Ms operation control signal ND short circuit detection circuit Nd short circuit count detection signal Ndr electrode negative polarity drive signal NS short circuit count setting circuit Ns Short circuit count setting signal NTR electrode negative polarity transistor Pdr electrode plus polarity drive signal PTR electrode plus polarity transistor SE electrode minus period switching circuit Se switching setting signal SP peak period switching circuit SWP polarity switching circuit Tb base period Tc control cycle TEN electrode minus period timer circuit Ten electrode minus period (signal) TP peak period timer circuit Tp peak period (signal) Vb base voltage VC initial voltage control setting circuit Vc initial voltage control setting signal VD voltage detection circuit Vd voltage detection signal Ven electrode negative voltage Vo output voltage Vp peak voltage Vs voltage setting (value / signal) VS1 initial voltage setting circuit Vs1 initial voltage setting signal Vsc voltage control setting signal Wc cleaning width WL reactor WM wire feeding motor

Claims (2)

[Claims] 1. A pulse current consisting of a peak current during a peak period during which droplets are transferred and a base current during a base period during which droplets are not transferred in the case of an electrode plus polarity in which an output current is passed from the welding wire side toward the object to be welded. Electrode energized and output current is energized in the welding wire direction from the work piece side Electrode that does not transfer droplets in the minus polarity Electrode minus current during the minus period is energized and EN ratio = {| electrode minus current x electrode minus period ｜ / (Peak current × Peak period +
Arc current in AC pulse arc welding in which at least one of the electrode negative current and the electrode negative period is changed according to a set value of base current × base period + | electrode negative current × electrode negative period |) × 100. Sometimes the preset initial voltage set value is set as the set voltage so that after the arc start, the detected value of the number of short circuits between the welding wire during welding and the object to be welded and the predetermined short circuit frequency set value become substantially equal. In an output voltage control method of correcting the set voltage for each control cycle to control the output voltage of a welding power source device, a function of the set value of the EN ratio and the initial voltage set value is predetermined, and the EN is set according to the function. An output voltage control method for a welding power source device, wherein the initial voltage set value corresponding to the set value of the ratio is set and the output is controlled. 2. In AC pulse arc welding in which welding conditions are set by a teach pendant and using a welding power supply and a welding robot, the EN ratio is set by an EN ratio setting signal from the teach pendant, The welding power source device according to claim 1, wherein a previous period initial voltage set value corresponding to the set value of the EN ratio is set and the output is controlled according to a predetermined function of the set value of the EN ratio and the set value of the initial voltage. Output voltage control method.