JP2003010971A - Output voltage control method of welding power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection value Nd of the number of short circuits between a welding wire during welding and an object to be welded and a predetermined number of short circuits in AC pulse arc welding of aluminum or an alloy thereof using a welding robot. In an output voltage control method for controlling an output voltage of a welding power supply device for each control cycle Tc so that the set value Ns becomes substantially equal, a change in a material of a workpiece, a welding speed, a welding position, a shape of a weld joint or a welding location. As a result, the apparent arc length fluctuates and the welding quality deteriorates. SOLUTION: The present invention relates to a material to be welded, a welding speed,
This is an output voltage control method of a welding power supply device that sets the time length of the control cycle Tc to an appropriate value by a teach pendant in accordance with at least one of a welding posture, a weld joint shape, and a welding location.

Description

Description: BACKGROUND OF THE INVENTION [0001] The present invention relates to a welding robot.
Arc welding of aluminum or its alloys
The number of short circuits between the welding wire and the workpiece during welding.
The detected value and the preset value of the number of short circuits are almost equal.
To control the output voltage of the welding power supply for each control cycle.
The present invention relates to a force voltage control method. 2. Description of the Related Art In consumable electrode gas shielded arc welding,
By controlling the output voltage of the welding power supply,
Maintain an appropriate value for the arc length, which has a significant effect on quality
You. The reason for controlling the output voltage is to directly detect the arc length.
It is difficult to perform
Indirectly controlling the arc length by controlling the output voltage
It is to control. However, the work to be welded is aluminum
Or its alloys (hereinafter referred to as aluminum alloys, etc.)
), The cleaning action is performed as described later.
Length is not proportional to output voltage due to the influence of
In some cases, the arc length is controlled by controlling the output voltage.
It may not be possible to maintain an appropriate value. this problem
In order to solve the problem, welding of aluminum alloy etc.
Welding wire and workpiece are in inverse proportion to arc length.
The number of short circuits becomes equal to the target value using the number of short circuits
The arc length by controlling the output voltage
An output voltage control method that maintains the value has been proposed. Less than
Below, first, as the conventional technology 1, the normal output voltage control described above is used.
After explaining the control method,
The output voltage control method based on the number of short circuits
You. [Prior art 1] FIG. 1 shows a case where a welding robot is used.
For welding gas shielded arc welding of consumable electrodes
It is a block diagram of a contact device. Hereinafter, description will be given with reference to FIG.
You. The welding operator uses the teach pendant 9 to
A wire feeding speed for a robot controller 8 described later,
The welding conditions Ws such as output voltage and welding speed are set. robot
The controller 8 controls the operation of the manipulator 7 described later.
An operation control signal Ms for performing control is output, and
Wire feed speed set by teach pendant 9
Formed from temperature setting signal, voltage setting signal, output start signal, etc.
The interface signal If is transmitted to a welding power supply
To the device 6. The manipulator 7 feeds the wire
With the motor WM and welding torch 4 mounted,
The tip position (TCP) of the welding torch 4 according to the control signal Ms
Is moved along the motion trajectory taught in advance. Welding wire
The ear 1 is driven by the wire feed motor WM.
It is fed through the welding torch 4. [0004] The welding power supply 6 is provided with the above-mentioned interface.
Signal If and receives the voltage setting signal
The corresponding output voltage Vo is output. As a result,
Arc 3 is generated between the wire 1 and the workpiece 2 and the output current
Io is energized. Further, the welding power supply device 6 is provided with a feed control signal.
And outputs the signal Fc to control the wire feed motor WM.
I do. In the following description, the consumable electrode gas
As one example of the cold arc welding method,
AC pulse arc welding method often used for welding
explain. Figure 2 shows the current and voltage of AC pulse arc welding
It is a waveform diagram. FIG. 7A shows the time change of the output current Io.
FIG. 7B shows the time change of the output voltage Vo.
Figures (C1) to (C4) show the arc occurrence state at each time.
Is shown. In the figure, EN indicates the negative polarity of the electrode.
EP indicates an electrode plus polarity. Refer to the figure below
Will be explained. The period from time t1 to t2 (peak period T
p) As shown in FIG. 3A, the electrode has a positive polarity EP, and
During a predetermined peak period Tp, a predetermined peak current Ip
Is energized. Usually, this peak period Tp and peak current
The value of Ip is set so that the welding wire is heated by one pulse per arc.
It is set to transfer droplets. Its value is the peak period
The interval Tp is about 1 to 3 [ms], and the peak current Ip
Is about 300 to 550 [A]. Also, FIG.
As shown in FIG.
The peak voltage Vp is equal to the welding wire (+) and the workpiece (-).
And between them. The period from time t2 to t3 (electrode minus
Period Ten) At time t2, the electrode positive polarity EP changes to the electrode minor.
When switching to the polarity EN, as shown in FIG.
In addition, during the predetermined electrode minus period Ten,
The electrode negative current Ien is supplied. Usually, this electrode
The values of the eggplant period Ten and the electrode negative current Ien are
Depending on the material, plate thickness, shape, etc.
It is set to an appropriate value within the box. The value is the electrode minus period
The interval Ten is about 1 to 10 [ms].
The flow Ien is about 30 to 120 [A]. Also,
As shown in (B), the flow of the above-mentioned electrode minus current Ien
The electrode minus voltage Ven corresponding to the current
The voltage is applied between (−) and the workpiece (+). The period from time t3 to time t4 (base period T
b) At time t3, the electrode is switched again from the electrode minus polarity EN.
When switching to the positive polarity EP, it is shown in FIG.
As described above, during the base period Tb, the droplets are not transferred.
(Approximately 20 to 70 [A]) and a predetermined base current Ib.
Is energized. In addition, as shown in FIG.
Base voltage Vb corresponding to the supply of
The voltage is applied between the wire (+) and the workpiece (-). the above
Is automatically controlled by the modulation control shown below.
Is determined. That is, as shown in FIG.
At the end of the scanning period Tb (time t4),
Output voltage Vo during EP period and predetermined voltage set value Vs
At which the integrated value Iv of the error becomes 0 [V].
In the case of the figure, the output voltage Vo during the period of the electrode plus polarity EP is
Is the same as the peak voltage Vp during the peak period Tp described above.
And the base voltage Vb during the scanning period Tb. But
Thus, the peak voltage value Vp during the peak period Tp and the above voltage
Integral value Iv1 of error from pressure set value Vs = 誤差 (Vp−Vs)
dt, the base voltage value Vb during the base period Tb, and
Integral value Iv2 of error from voltage set value Vs = 誤差 (Vb−V
s) The following equation is used so that the addition value with dt becomes 0 [V].
Thus, the end point (time t4) of the base period Tb is determined. Iv = ∫ (Vp−Vs) dt + ∫ (Vb−Vs) dt = 0 (1) After time t4, the above-mentioned operations of (1) to (4) are defined as one cycle.
The welding is performed repeatedly. [0009] Arc generation state in each period described above
As shown in FIG. 2C, the peak period Tp
In the middle, welding is performed by applying a large current peak current Ip.
The melting of the tip of the wire 1 is promoted, and the droplet 1a becomes large.
Lengthen. At this time, the cathode point of arc 3 is cleaned.
Of the workpiece 2 whose oxide film has not been removed by the action
Formed on the surface. Next, as shown in FIG.
In the latter half of the peak period Tp, the peak
The upper portion of the droplet 1a due to the pinch force caused by the current Ip
Constriction occurs. Further, as shown in FIG.
Term peak period Tp ends and electrode plus polarity EP
Immediately after time t2 when the electrode switches to the electrode minus polarity EN.
The droplet 1a separates from the welding wire 1 and
Move to 2. Immediately before the transfer of the droplet, the droplet 1a is
Shortening of the welding wire 1 and the workpiece 2 due to contact with the workpiece 2
Tangles may occur. How often this short circuit occurs
The number of short circuits per unit time)
It increases as the shortest distance (arc length) to the weldment 2 decreases,
The longer, the less, the two are inversely related. Further
In addition, as shown in FIG.
During the current period Ten, the negative electrode current Ien is applied.
The droplet grows gradually. The cathode point of arc 3 at this time
Speeds the entire droplet and the non-molten portion under the welding wire 1
Arc 3 is formed by droplets and
It occurs from the entire lower part of the contact wire 1. Same figure as above
As shown in (C1) to (C4), droplet formation, growth and
Welding is performed by repeating each process of transfer and transfer. FIG. 3 shows the AC pulse arc welding described above.
FIG. 3 is a block diagram of a welding power supply device 6 to be implemented. Less than
Hereinafter, each circuit block will be described with reference to FIG.
The commercial power supply AC is an input power supply of the welding power supply, and is usually
Uses three-phase 200/220 [V]. Output control times
Although the illustration of the internal circuit is omitted in the path INV,
A primary-side rectifier circuit for rectifying a commercial power supply AC;
A smoothing circuit for smoothing a voltage with ripples,
An inverter circuit that converts DC voltage to high-frequency AC,
Sets of power transistors forming an inverter circuit
Drive circuit and a current error amplified signal Ei to be described later.
Therefore, the PWM for performing the PWM control of the above inverter circuit
And a control circuit. The high-frequency transformer INT is connected to the high-frequency AC
To a voltage value suitable for the arc load. Secondary rectifier
D2a to D2d rectify the stepped down high frequency AC to DC
You. The polarity switching drive circuit DR includes an electrode minor described later.
When the input period signal Ten is input (High level).
Outputs an electrode negative polarity drive signal Ndr (Hig
h level) and not input (Low level)
Outputs the electrode positive polarity drive signal Pdr (High level)
Bell). Therefore, the electrode negative polarity drive signal
Electrode plus polarity drive when signal Ndr is output
The signal Pdr is not output.
When the drive signal Ndr is not output,
The live signal Pdr is output.
It is in a reversed relationship. Electrode plus polarity transistor PTR
Outputs the above-mentioned electrode plus polarity drive signal Pd.
When the electrode is in the positive polarity period.
You. On the other hand, the electrode negative polarity transistor NTR is
The electrode negative polarity drive signal Ndr described above is output.
When the electrode is in the negative polarity period.
You. The polarity switching drive circuit DR and the electrode
Lath polarity transistor PTR and electrode minus polarity tiger
A polarity switching circuit SWP is formed by the transistor NTR.
You. This polarity switching circuit SWP outputs an electrode minus period signal.
When Ten is input (High level), the power supply
DC output (output of secondary side rectifier D2a ~ D2d)
Switch to minus polarity, no input (Low level)
When the DC output of the power supply is
Replace it. The reactor WL has the above-mentioned electrode plus polarity.
Transistor PTR or transistor with negative polarity
Smooth output with ripple to energize NTR and arc
Supply 3 During the electrode plus polarity period described above with reference to FIG.
The peak current Ip and the base current Ib are D2a or D2b →
Energize in the path of PTR → WL → welding wire 1 → workpiece 2
I do. On the other hand, during the negative electrode polarity period,
Flow Ien is to be welded 2 → welding wire 1 → NTR → WL →
Power is supplied through the path of D2c or D2d. The welding wire 1 is connected to a feeder of a wire feeder.
The feed through the welding torch 4 by the
Power from the contact tip at the tip of the welding torch 4
Thus, an arc 3 is generated between the workpiece 2 and the workpiece 2. The peak period timer circuit TP has a
When the set signal Cp is input (High level),
Peak period signal which becomes High level for a predetermined period
Output Tp. Electrode minus period timer circuit TEN
Means that the peak period signal Tp is changed from the High level to L
When the level changes to the ow level, Hig is set for a predetermined period of time.
An electrode minus period signal Ten at the h level is output. The voltage detection circuit VD detects the output voltage Vo
Then, a voltage detection signal Vd is output. In the description section of FIG.
As described above, the setting by the teach pendant 9
Interface signal from the robot controller 7 after
The voltage setting signal Vs transmitted as a part of If
The voltage during the positive polarity period (the peak voltage V described above with reference to FIG. 2)
It becomes the target value of the average value of p and the base voltage Vb). Voltage
The error circuit EV performs the above-described error calculation of Vd−Vs,
It outputs a voltage error signal Ev. The integration circuit IV is as described above.
No electrode minus period signal Ten is input (Lo
w level), the above voltage error signal Ev is integrated.
And outputs an integrated value signal Iv. In the above, the electrode
When the negative period signal Ten is not input,
This is during the positive polarity period. Therefore, the above integral
The circuit IV has a relation Iv = ∫ (Vd−
Vs) dt = ∫ (Vp−Vs) dt + ∫ (Vb−Vs)
dt is integrated. The comparison circuit CP calculates the integration
When the value signal Iv becomes 0 [V], the High level
The reset signal Cp serving as a bell is output. This reset
The signal Cp is input to the above-described peak period timer circuit TP.
Then, a trigger signal for starting output of the peak period signal Tp and
Become. The above-described voltage error circuit EV and integration circuit IV
The modulation circuit MC is formed by the
The following processing corresponding to the above described equation (1) is performed. Sandals
That is, the modulation circuit MC starts outputting the peak period signal Tp.
Voltage detection signal Vd and voltage during electrode plus polarity period from point
The integral value Iv of the error from the setting signal Vs has become 0 [V].
Sometimes, the peak period timer circuit TP starts outputting again.
A reset signal Cp serving as a trigger signal is output. The peak current setting circuit IP controls the droplet transfer.
Output a predetermined peak current setting signal Ip to a value to be set.
You. The electrode minus current setting circuit IEN detects the droplet transfer.
The electrode negative current setting signal Ien
Output. The base current setting circuit IB makes the droplet transfer.
Outputs a predetermined base current setting signal Ib to a non-existent value
You. The peak period switching circuit SP performs the above-described peak period signal.
A side when the signal Tp is input (High level)
And the current is controlled by the peak current setting signal Ip.
It is output as the setting signal Isc and is not input (Low
Level), switch to the b side and switch setting signal described later
Se is output as a current control setting signal Isc. Electrode My
The eggplant period switching circuit SE is provided with the above-described electrode minus period signal.
A when the signal Ten is input (High level)
To switch the above-mentioned electrode minus current setting signal Ien.
Is output as the switching setting signal Se and is not input (Lo
(w level), switch to the b side to set the base current
The constant signal Ib is output as the switching setting signal Se. above
Peak period switching circuit SP and electrode minus period switching circuit
A current control setting circuit ISC is formed by SE, and
Is as follows. That is, the current control setting
When the peak period signal Tp is input, the circuit ISC
The current setting signal Ip is input to the electrode minus period signal Ten.
When input, the electrode minus current setting signal Ien is
When neither of the signals Tp and Ten is input
Let the base current setting signal Ib be a current control setting signal Isc
Output. The current detection circuit ID is an output current which is an alternating current.
Io is detected, the value is converted to an absolute value, and a current detection signal
Output Id. The current error amplifying circuit EI outputs the above current
Amplify the error between the detection signal Id and the current control setting signal Isc.
And outputs a current error amplified signal Ei. This current error increase
According to the width signal Ei, the output control circuit INV described above outputs
The current value of the force current Io is controlled. Therefore, Isc = I
When p, the peak current Ip flows, and when Isc = Ien
Indicates that the electrode negative current Ien is conducted and when Isc = Ib
The base current Ib flows. FIG. 4 shows a welding power supply of the above-mentioned prior art 1.
6 is a timing chart of each signal in the device 6. Same figure
(A) shows a time change of the output current Io, and FIG.
FIG. 7C shows a time change of the output voltage Vo, and FIG.
FIG. 4D shows a time change of the inter-signal Tp, and FIG.
(E) shows the time change of the scan period signal Ten, and FIG.
FIG. 5F shows a time change of the signal Iv, and FIG.
5 shows a time change of Cp. Figures (A) and (B) are as described above.
FIG. Hereinafter, description will be made with reference to FIG. The period from time t1 to t2 (peak period T
p) As shown in the same figure (D), during this period, the electrode minus period
Since the inter signal Ten is not output (Low level)
Then, the electrode has the positive polarity EP. Also shown in FIG.
As shown, the peak period signal Tp is output (High level).
(A), the peaks as shown in FIG.
The current Ip flows. Further, as shown in FIG.
In addition, the integrated value signal Iv has a peak voltage V shown in FIG.
p and the voltage setting signal Vs, Iv = ∫ (Vp−V
s) The integral value of dt is obtained. At this time, Vp> Vs
Therefore, the integral value increases with time. The period from time t2 to t3 (electrode minus
Period Ten) As shown in FIG. 4D, during this period, the electrode minus period
Since the inter signal Ten is output (High level)
Then, the electrode has a negative polarity EN, as shown in FIG.
Thus, the electrode negative current Ien flows. Also,
As shown in (E), the above-mentioned electrode minus period signal Ten
Is output, the integration process stops, and the integrated value signal
Iv does not change during this period. A period from time t3 to t4 (base period T
b) During this period, as shown in FIG.
Since the inter signal Ten is not output (Low level)
Then, the electrode becomes the positive polarity EP again. In addition, FIG.
The peak period signal Tp shown in FIG.
Neither the negative period signal Ten is output (Low level).
(B), the base current I as shown in FIG.
b is energized. Further, as shown in FIG.
The value signal Iv is based on the base voltage Vb and the voltage Vb shown in FIG.
According to the pressure setting signal Vs, Iv = に よ っ て (Vb−Vs) dt
It becomes the integral value. At this time, since Vb <Vs,
The integral value decreases with the passage of time, and at time t4
0 [V]. The integrated value signal Iv becomes 0 [V].
When the reset signal Cp is short, as shown in FIG.
High level during this time, and as a result,
The output of the peak period signal Tp starts. As described above, in the conventional art 1, the electrode plug is used.
Of the peak voltage Vp and the base voltage Vb during the lath polarity period.
The output voltage is controlled so that the average value becomes equal to the voltage set value Vs.
Control to maintain the arc length at an appropriate value.
Can be. [Prior Art 2] As described above, the output voltage
When the arc length is proportional to
Optimum arc length by output voltage control method of technology 1
Can be maintained. However, such as aluminum alloy
In arc welding, the output voltage and
Because it is not proportional to the arc length, the output of prior art 1
With the voltage control method, the arc length can be maintained at an appropriate value.
I can't. Hereinafter, the reason will be described with reference to FIG.
You. FIG. 5 shows arc welding of an aluminum alloy or the like.
FIG. 4 is a diagram showing an arc generation state in FIG. FIG.
To indicate the removal range of the oxide film on the surface of the work
Fig. (B) shows the case where the horning width Wc1 [mm] is narrow.
This is a case where the cleaning width Wc2 [mm] is wide. Also,
The figure shows that the welding wire 1 is the anode and the workpiece 2 is the cathode.
This is when the electrode has negative polarity. Refer to the figure below
Will be explained. Normally, the cathode point of the arc 3 is where electrons are emitted.
Easy to clean oxide film
Formed in the region where Therefore, as shown in FIG.
Then, an anode is formed at the point A of the tip of the welding wire 1,
A cathode spot is formed around the outer peripheral point B of the shining area. this
Therefore, the distance Lt1 [mm] between point A and point B is the true arc length.
It becomes. On the other hand, point A of the welding wire tip
The distance La1 [mm] from point C on the workpiece below is apparent
Work length. What is the arc length in the explanation so far?
This is the arc length. This true arc length Lt1
The output voltage is proportional to the apparent arc length La1.
It is not proportional to the output voltage. Therefore, as mentioned above
In the output voltage control method of the prior art 1, the true arc length is reduced by one.
This means that it is maintained at a constant value. However, penetration
The welding quality, such as depth and bead appearance, depends on the apparent arc length L.
a1 is greatly affected, and the true arc length is
small. That is, in order to obtain good welding quality,
It is necessary to maintain the dummy arc length at an appropriate value. Place
In the case of arc welding of steel, there is no oxide film on the surface
Therefore, the cathode point is located around point C where the arc path is the shortest.
Form. Therefore, the true arc length Lt1 and apparent arc
Is approximately equal to the peak length La1. For this reason, the prior art 1
Controlling the true arc length by the output voltage control method
Controls the apparent arc length at the same time. Surface condition (dirt, etc.) of the workpiece during welding;
The shielding state of the shielding gas and the temperature of the workpiece as the welding progresses
The cleaning width Wc of the workpiece is
It changes greatly. Cleaning width during welding
(B) from the cleaning width Wc1 [mm] shown in (A).
When the cleaning width is increased to Wc2 [mm] shown below,
The arc generation state changes as shown in FIG. That is,
As shown in (B), the cathode spot is located at the outer periphery of the cleaning area.
It is formed around the point E. At this time, as described above,
The true arc length (point D-
(Point E) is Lt1 [mm] having the same value as in FIG. This
As a result, the apparent positional relationship
Is shortened to La2 [mm]. Contrary to the above,
If the cleaning width is reduced during welding, an apparent arc
The length increases. As described above, an aluminum alloy or the like
In arc welding, the output voltage control method of the prior art 1 is used.
Appears as the cleaning width fluctuates during welding.
The problem is that the weld length changes and the welding quality deteriorates.
Was. In order to solve this problem, the conventional
An output voltage control method based on the number of short circuits of the technology 2 has been proposed.
I have. That is, in the output voltage control method of the prior art 2,
As described above in the description of FIG.
Frequency of generated short circuits (number of short circuits per unit time)
Utilizing the fact that the arc length is inversely proportional to
Control the output voltage so that the number of short circuits becomes equal to the target value.
To maintain the apparent arc length at an appropriate value.
Is the way. Hereinafter, the prior art 2 will be described with reference to the drawings.
explain. FIG. 6 shows an output voltage control method according to prior art 2.
Block of the welding power supply 61 for controlling the number of short circuits
FIG. In this figure, the same circuit as in FIG.
The same reference numerals are given to the blocks, and their description is omitted.
You. Hereinafter, a circuit block different from that of FIG.
Short circuit frequency detection circuit ND, short circuit frequency setting circuit NS and short circuit
The number-of-entangles error integration circuit ENI will be described. The number-of-short-circuits detection circuit ND outputs the voltage detection signal V
The short circuit is determined by the voltage value of d
The number of short circuits is counted, and a short circuit frequency detection signal Nd is output.
1 [s] is used as the unit time. Short circuit count setting
The circuit NS is based on the teach pendant 9 described above with reference to FIG.
Including the short circuit count set value
Outputs short circuit count setting signal Ns with signal If as input
You. Therefore, the short circuit count setting signal Ns
Set by chip pendant. Short-circuit error integration circuit
ENI is the above-mentioned short circuit number detection signal Nd and short circuit number setting
With the signal Ns as an input, the following equation is calculated and voltage control is performed.
The setting signal Vsc (n) is output. Vsc (n) = Vsc (n-1) + G * (Nd-Ns) (2) where G is a predetermined amplification factor. Performance of the above formula (2)
In the calculation, G × (Nd) is performed every predetermined control cycle Tc [s].
−Ns) and calculate the previous voltage control setting signal Vsc (n-1).
The current voltage control setting signal Vsc (n) is calculated by the addition.
This control cycle Tc corresponds to the unit time described above.
In the steady state, it is set to about 1 [s]. However,
When the error of Nd−Ns in the above equation (2) is large,
In order to improve the transient response of the control system,
There is also a method to change so that it becomes transiently shorter according to the error
Proposed. The subsequent operations are the same as those in FIG.
Therefore, the description is omitted. As mentioned above
Conventional technology 2 corresponds to the appropriate value of the apparent arc length.
The short circuit count setting signal Ns is set, and the number of short circuits during welding is set.
The detection signal Nd is substantially equal to the short circuit number setting signal Ns.
Thus, the output voltage of the welding power supply is controlled. The object to be welded is aluminum
When the alloy is a magnesium-magnesium (Al-Mg) alloy
In pulse arc welding, the surface properties of the workpiece
The shape of the arc typified by the cage cleaning width changes suddenly
Variation in the number of short circuits due to droplet transfer
Key is small, and the output voltage control method of the prior art 2 described above is
Therefore, the apparent arc length can be maintained at an appropriate value.
You. However, the work to be welded is aluminum
-Pulse arc when it is a silicon (Al-Si) alloy
In welding, the surface properties of the workpiece vary widely.
The shape of the arc represented by the cleaning width changes suddenly
Droplet transfer may be slightly unstable,
The variation in the number of short circuits due to the transfer of droplets increases. others
In the output voltage control method of the prior art 2,
The variation of the arc length becomes large, the penetration depth,
The appearance of the weld changes and the welding quality deteriorates. Also aluminum
DC pulse arc welding of AC alloys such as
Droplet transfer is slightly unstable compared to arc welding
Then, the same problem as described above occurs. FIG. 7 shows a short circuit illustrating a specific example of the problem described above.
It is a frequency | count and apparent arc length fluctuation diagram. Figure (A) is short
The time change of the number-of-entanglement detection signal Nd is shown in FIG.
5 shows a temporal change of a dummy arc length La. The figure shows the welded
AC pulse using aluminum-silicon alloy for object
This is the case of arc welding. Hereinafter, description will be given with reference to FIG.
You. As described above, the object to be welded is aluminum.
-Silicon alloy and the welding method is AC pulsed
The droplet transfer becomes slightly unstable due to the use of the welding method.
For this reason, as shown in FIG.
The detection signal Nd of the number of short circuits fluctuates greatly. This short circuit times
Output voltage control using number detection signal Nd as feedback signal
Output voltage (not shown)
Fluctuates, and as a result, as shown in FIG.
Also greatly fluctuates. Because of this, penetration
Depth, bead appearance, etc. change, resulting in poor welding quality. The welding speed, welding position, welding joint shape,
When the welding location changes, the apparent arc length changes
You. That is, when the welding speed is low, the molten pool
Because it is directly below the wire tip and the weld pool just below the wire
Is the apparent arc length. However, the welding speed
When the speed is faster, the molten pool is behind the wire just below
And the distance between the wire tip and the weld pool (apparent arc length)
Becomes longer. Therefore, the welding speed increases during welding
Thus, the apparent arc length becomes longer. Also, the welding position
Depending on the advance angle of the welding torch,
The distance (apparent arc length) from the molten pool in the ear feeding direction is
Change. Therefore, the advance angle of the welding position changes during welding.
As a result, the apparent arc length changes. In addition, welding seam
Hand shape changes from lap fillet joint to butt joint, for example
When changed, apparently because the cleaning state changes
Changes the arc length. Also, the shape and thickness of the welding location
Changes, the temperature of the weld changes due to arc heat
The cleaning condition changes and the apparent arc length
Change. As described above, the apparent arc length changes.
Then, since the number of short circuits changes, the output voltage of the prior art 2
The apparent arc length returns to the original appropriate value depending on the control method.
I do. As described above, the control cycle Tc of the output voltage is steady.
In the state, the arc length is 1 [s], so the apparent arc length is once
After a large change in the number of short circuits, the detected value
Control cycle Tc is too large because the error between
The apparent arc length returns to its original proper value
I do. Therefore, during a long control cycle Tc in a steady state,
Once the apparent arc length changes greatly,
Recovery time Td1 [s] until the arc length returns to the appropriate value
Becomes longer. As a result, the apparent arc length became longer
Welding quality changes due to changes in penetration depth and bead appearance
Gets worse. Note that the control cycle Tc in the steady state is 1 [s].
Is set to a steady state under various welding conditions.
Control stability (change in apparent arc length)
That's because. FIG. 8 shows a short circuit illustrating a specific example of the problem described above.
It is a frequency | count and apparent arc length fluctuation diagram. Figure (A) is short
The time change of the number-of-entanglement detection signal Nd is shown in FIG.
5 shows a temporal change of a dummy arc length La. The figure shows the welding process.
This is the case where the welding speed is increased at the middle time t1. As shown in FIG. 3A, at time t1
As the welding speed increases, the apparent
The short circuit count detection signal Nd is
It becomes smaller than the number setting signal Ns. For this,
Also, the output voltage (Vsc) is reduced by the equation (2).
Is controlled. As a result, the apparent arc length is
Returns to the value. However, as mentioned above,
In the state, the calculation of the expression (2) is performed every control cycle Tc = 1 [s].
As shown in FIG.
The clock length La changes greatly after the time t1 until the time t2.
Returns to an appropriate value after a long return time Td1 [s] elapses. This
Therefore, during the period from time t1 to t2, the apparent arc length
Since La is longer than the appropriate value, the penetration depth
The welding quality is degraded due to changes in the appearance and the like. As described in the section and the section above, the aluminum
Technology 1 in AC pulse arc welding of aluminum alloys
And in the prior art 2, the material of the workpiece, welding speed, welding
Due to changes in posture, weld joint shape or weld location
Because of the change in the arc length, the penetration depth and bead
Solution that appearance and other properties change and welding quality deteriorates
There were challenges. Therefore, in the present invention, the material of the workpiece,
Changes in welding speed, welding position, weld joint shape or welding location
Nevertheless, the apparent arc length can always be maintained at an appropriate value.
To provide an output voltage control method for a welding power supply device. According to the first aspect of the present invention, FIG.
As shown in the figure, welding conditions by the teach pendant 9
Is set, and the welding power supply device 6 and the welding robot 7 are used.
Pulse arc melting of aluminum or its alloys
The welding wire 1 being welded to the workpiece 2
The detection value Nd of the number of short circuits and a predetermined short circuit number Ns
Are substantially equal to each other at each control cycle Tc.
In the output voltage control method for controlling the output voltage Vo of the device 6
The material to be welded, welding speed, welding position, weld joint type
Corresponding to at least one of the
The time length of the control cycle Tc is added to the teach pendant 9.
Therefore, the output voltage control method of the welding power supply set to an appropriate value
Is the law. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments described below are
This corresponds to the invention of claim 1. In this embodiment, the welding robot
Pulse arc melting of aluminum alloy etc.
In welding, the material of the workpiece, welding speed, welding position,
Corresponds to at least one of the joint shape or welding location
The time length of the control cycle Tc by the teach pendant
Is set to an appropriate value, and the short circuit frequency detection value Nd during welding is
So that the set value of the number of short circuits Nr
The output voltage of the welding power supply device is controlled at every control cycle Tc described above.
Output voltage control method. Hereinafter, description will be made with reference to FIG.
I do. FIG. 9 shows an output voltage control method according to the present invention.
Block diagram of the control cycle variable welding power supply 62 for performing
It is. In this figure, the same circuit block as that of FIG.
The same reference numerals are given to the same symbols, and their description is omitted. Less than
Below, the control cycle variable short circuit detection circuit indicated by a dotted line different from FIG.
Path CND, control cycle setting circuit TC and control cycle variable short circuit
The number-of-times error integrating circuit CEN will be described. The control cycle variable short circuit count detection circuit CND
A short circuit is determined based on the voltage value of the voltage detection signal Vd, which will be described later.
The number of short circuits in each control cycle Tc is counted, and the counted value is
Converted to the number of short circuits per unit time,
The signal Nd is output. The control cycle setting circuit TC is the same as that shown in FIG.
The control cycle set by the teach pendant 9 described above
The interface signal If including the period Tc is input,
The control cycle setting signal Tc is output. This control cycle setting signal
The value of the signal Tc depends on the material of the workpiece, the welding speed, the welding position,
Teach to an appropriate value according to the shape of the weld joint or welding location
Set by pendant. Control cycle variable short circuit frequency error integration circuit CEN
Are the above-mentioned short circuit number detection signal Nd and short circuit number setting signal N
s as an input, and the above described control period Tc
Calculates the equation (2) and outputs the voltage control setting signal Vsc (n).
Power. As described above, in the present embodiment, the workpiece
Material, welding speed, welding position, weld joint shape or welding piece
At least one of the control periods T
Set the time length of c to an appropriate value using the teach pendant.
Always maintain the apparent arc length at an appropriate value.
be able to. [Effect] FIG. 10 shows the effect of the present invention.
The number of short circuits and apparent arc corresponding to Fig. 7
FIG. FIG. 3A shows the short-circuit count detection signal Nd.
FIG. 8B shows the change in the apparent arc length La.
Shows the time change. The same figure as in FIG.
AC pallets using aluminum-silicon alloy for the implant
This is the case of sark welding. In the same figure, the control cycle
Tc is adjusted to the above welding conditions with a teach pendant.
This is a case where it is appropriately set to 2 [s]. Refer to the figure below
Will be explained. As described above, the object to be welded is aluminum.
-Silicon alloy and the welding method is AC pulsed
The droplet transfer becomes slightly unstable due to the use of the welding method.
For this reason, the number of short circuits detected in a short cycle is large.
However, the control cycle Tc is increased to 2 [s].
As shown in the same figure (A),
In addition, the fluctuation width of the number of times of short circuit detection signal Nd becomes small. this
Outputs the number of short circuit detection signal Nd as a feedback signal
Since voltage control is performed, the output voltage
The moving width becomes smaller. As a result, as shown in FIG.
In addition, the fluctuation width of the apparent arc length La becomes small,
The value is stably maintained. FIG. 11 shows another effect of the present invention.
The number of short-circuits and apparent
FIG. FIG. 7A shows a short-circuit count detection signal N.
FIG. 6B shows the apparent arc length L.
The time change of a is shown. This figure is similar to FIG. 8 described above.
When the welding speed is increased at time t1 during welding
is there. The figure also shows the time
The control cycle Tc immediately after the time t1 or after the time t1 is set to the time
In the case where it is set in advance so as to be shorter than before t1.
You. As shown in FIG. 5A, at time t1
As the welding speed increases, the apparent arc length increases.
Therefore, the short circuit count detection signal Nd is
s. For this reason, the above equation (2)
Therefore, the output voltage (Vsc) is controlled to be small.
You. As a result, the apparent arc length returns to the original appropriate value.
You. In this control, immediately before time t1 or the same as time t1.
Sometimes the control cycle Tc is longer than that in the steady state.
Feedback from length to short duration
The transient response of the correct / error system is improved. For this purpose,
As shown in (A), the return time is Td1 in FIG.
[S] is greatly reduced to Td2 [s]. Accordingly
As shown in FIG. 3B, the apparent arc length La is
Returns to the proper value in a short time. By the way, the welding worker is required to
Quality, welding speed, welding position, weld joint shape, shape of welding location
Know the shape before welding. Therefore, welding work
The contractor will change the welding conditions according to the welding location where the welding conditions change.
Appropriate control cycle Tc with teach pendant before contact
Can be set to a value. For this reason, in the present invention,
The material of the workpiece, welding speed, welding position, weld joint shape or
In response to at least one change in the weld location
Immediately before or simultaneously with the change of the control cycle Tc to an appropriate value
So that the apparent arc length is always maintained at an appropriate value.
Can be According to the present invention, a pallet made of aluminum alloy or the like is used.
In sark welding, the material, welding speed,
At least one of the contact position, weld joint shape or welding location
In response to the above, the number of short circuits
The output voltage control cycle Tc is set to an appropriate value.
The apparent arc length can always be maintained at an appropriate value,
Good welding quality can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a consumable electrode gas shielded arc welding device using a welding robot. FIG. 2 is a current / voltage waveform diagram of AC pulse arc welding. FIG. FIG. 4 is a timing chart of a welding power supply device according to prior 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 prior art 2; FIG. 8 is a diagram showing a change in the number of short circuits and an apparent arc length showing a problem to be solved. FIG. 8 is a block diagram showing a change in the number of short circuits and an apparent arc length showing another problem to be solved. FIG. 11 is a diagram showing a change in the number of short circuits and an apparent arc length showing the effect of the present invention. FIG. 11 is a diagram showing a change in the apparent arc length and the number of short circuits showing another effect of the present invention. Weldment 3 4 Welding torch 5a Feeding roll of wire feeder 6 Welding power supply 61 Short-circuit frequency control welding power supply 62 Controllable variable welding power supply 7 Welding robot (manipulator) 8 Robot controller 9 Teach pendant AC Commercial power supply CEN Control cycle variable short-circuit count error integration circuit CND Control cycle variable short-circuit count detection circuit CP Comparison circuit Cp Reset signal D2a to D2d Secondary rectifier DR Polarity switching drive circuit EI Current error amplifier Ei Current error amplifier signal EN Electrode negative polarity ENI Short circuit Frequency error integration circuit EP Electrode plus polarity EV Voltage error circuit Ev Voltage error signal Fc Feeding 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 minus current setting circuit Ien electrode negative 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 Integration value (signal) La Apparent arc Length Lt True arc length MC Modulation circuit Ms Operation control signal ND Short circuit frequency detection circuit Nd Short circuit frequency detection signal Ndr Electrode negative polarity drive signal NS Short circuit frequency setting circuit Ns Short circuit frequency setting signal NTR Electrode negative polarity transistor Pdr Electrode positive 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 setting circuit Tc control cycle (setting signal) Td return time TEN electrode minus period timer Ma circuit Ten electrode minus period (signal) TP peak period timer circuit Tp peak period (signal) Vb base voltage VD voltage detection circuit Vd voltage detection signal Ven electrode minus voltage Vo output voltage Vp peak voltage VS voltage setting circuit Vs voltage setting (value / Signal) Vsc Voltage control setting signal Wc Cleaning width WL Reactor WM Wire feed motor

Continuation of front page    (72) Inventor 紅 Red Army             2-1-1 Tagawa, Yodogawa-ku, Osaka-shi, Osaka             Daihen Corporation F term (reference) 4E082 AA01 EC17 ED01                 5H790 BA03 BB08 CC02 DD06 EA02                       EA03 EA07 EA15 EB03 EB04

Claims (1)

The present invention relates to pulse arc welding of aluminum or an alloy thereof using a welding power source device and a welding robot, wherein welding conditions are set by a teach pendant. In an output voltage control method of controlling an output voltage of the welding power supply device in each control cycle so that a detected value of the number of short circuits with a welded object and a predetermined set value of the number of short circuits are substantially equal, the material of the object to be welded, An output voltage control method for a welding power supply device, wherein a time length of the control cycle is set to an appropriate value by the teach pendant in accordance with at least one of a welding speed, a welding position, a weld joint shape, and a welding location.