JPH0328979B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a groove adaptive control method in consumable electrode arc welding in which the groove is welded while a welding torch is oscillated in the width direction of the groove. [Prior Art] This type of groove adaptive control method is conventionally described in Japanese Utility Model Publication No. 57-36373. In consumable electrode arc welding, in order to obtain a proper weld bead, the oscillation width of the welding torch is adjusted according to the groove width, and the welding wire feeding speed or welding speed is controlled to adjust the weld bead height. At the same time, the welding line is controlled to follow left and right to prevent the weld bead from being biased or meandering toward one or the other of the left and right ends of the groove. In order to make this control effective, it is necessary to accurately recognize the condition of the groove (presence or absence of fluctuation in the groove width, degree of fluctuation, position of the weld line, etc.). By the way, in consumable electrode type arc welding, if the welding wire feeding speed is W, the welding current is I, and the welding wire protrusion length (the protrusion length from the current-carrying tip) is l, then W=K ₁・I+K ₂・I There is a characteristic expressed as ²・l. However, K ₁ and K ₂ are proportionality constants. Now, when welding wire feeding speed W is kept constant, welding current I increases as welding wire protrusion length l becomes shorter.
When the groove width becomes narrower, the weld bead height becomes higher, so the welding wire protrusion length l becomes shorter and the welding current I increases. Conversely, when the groove width becomes wider, the welding bead height becomes lower and the welding wire protrudes more. As the length l increases, the welding current I decreases. From this, it is possible to indirectly know the fluctuations in the groove width by monitoring the fluctuations in the welding current I, and whether the welding current I increases or If it decreases, the welding bead height can be maintained at an appropriate level by increasing or decreasing the welding speed in accordance with the variation. However, the above-mentioned fluctuations in welding current are also caused by fluctuation factors other than fluctuations in groove width. The biggest factor in this variation is the surface of the base metal as a workpiece at the welding site due to inclination or bending in the groove longitudinal direction, and the welding torch holding part (the groove width It is a change in the distance between the welding torch and the reference position on the welding torch side, where the distance from the base metal reference position is constant even when oscillating in the torch width direction.If the distance changes, the groove width will change. Even if there is no welding wire, the welding current I changes because the welding wire protrusion length l changes. In order to eliminate the influence of this variation, Japanese Patent Laid-Open No. 109576/1983 discloses a method of controlling the welding speed while keeping the welding torch at a constant height from the surface of the base metal. This conventional method constantly compares the welding current detection signal and the reference welding current signal, converts the deviation into a level to produce a welding speed deviation signal, and calculates the sum of this welding speed deviation signal and the reference welding speed signal for welding. The welding current detection signal is used as a speed command value to control the cart drive motor, but the welding current detection signal has a minimum value when the arc is near the center between the groove walls, and a minimum value when the arc is near the groove walls. Since the signal has the maximum waveform, there is a problem in that the drive motor follows the oscillation position and repeats speed increase and deceleration. The above-mentioned Japanese Utility Model Publication No. 57-36373 discloses that the welding current detection point is specified at the center point of the oscillation pattern, which can solve the above problem, but this prior art has the following problems. There are problems as described. In other words, the instantaneous value of the welding current at the center point of the oscillation pattern is extracted and used here, but in difficult position welding (upright or upward position), the welding current is at a low level, and droplets from the welding wire are Since the transition is also short-circuit transition or gravure transition, the instantaneous value of the welding current is unstable. Furthermore, in this prior art, a standard welding speed, a high welding speed, and a low welding speed are specified in advance, and when a deviation occurs between the detected welding current and the standard welding current, the high welding speed or the low welding speed is changed to the above-mentioned high welding speed or low welding speed. If the speed command is changed and the deviation is eliminated as a result, the speed command is returned to the standard welding speed in the next oscillation half cycle, as shown in Fig. 9f.
If the above deviation is not eliminated, the same speed (the above-mentioned high welding speed or low welding speed) is maintained. That is, even if a welding speed suitable for the groove width of the groove being welded is obtained, in the next oscillation half cycle, this appropriate welding speed is abandoned and welding is performed at the standard welding speed. However, the actual groove is as shown in Figure 9a.
As shown in Figure 2, the groove width changes continuously in a tapered manner to become wider or narrower. As the welding progresses, the welding speed increases as the welding progresses, and there is a risk of a hunting condition in which the welding speed repeatedly increases or decreases rapidly every half period of the oscillation, and it is difficult to obtain a uniform bead height over the entire length of the groove. be. In addition, conventional welding line left/right tracing control, for example,
As shown in the above-mentioned Japanese Utility Model Publication No. 57-36373, the instantaneous value of the welding current is picked up at the left or right end point of the oscillation pattern of the welding torch, stored in a memory, and then detected. The instantaneous value of the welding current is compared with the stored current value by a comparator, and based on the comparison result, the motor for tracing the welding line left and right is controlled. However,
This method uses the instantaneous value of the welding current, which is unstable as described above, which may lead to malfunctions, especially under welding conditions where the arc is unstable, and it is difficult to obtain good tracing accuracy. The instantaneous welding current value is input into the comparator and memory unit after passing through a low-pass filter that causes a time delay, so there is a phase shift between this instantaneous welding current value and the actual position of the welding torch. This causes a decrease in copying accuracy. The automatic control of the oscillation width of the welding torch is such that the oscillation width is automatically increased or decreased based on the welding speed, as shown in the above-mentioned two publications. However, the welding speed itself obtained by the automatic welding speed control of these conventional techniques will be in the hunting state as described above, so the oscillation width cannot be increased or decreased appropriately in response to the increase or decrease in the target groove width. There is a problem. This invention was made to solve the above-mentioned conventional problems, and it is possible to make welding speed faithfully follow changes in groove width, and also to provide accurate and highly adaptable welding line left/right tracing control and oscillation width. The purpose of this study is to obtain a groove adaptive control method for consumable electrode type arc welding that makes it possible to realize control. [Means for Solving the Problems] In order to achieve the above object, the present invention provides (a) a welding method in which a welding current measurement value, which is measured as an average value of welding current for a predetermined period every oscillation half cycle, is initially set; Compare it with the current reference value, take out the deviation as the first welding current deviation, calculate the first welding speed correction command value based on this first welding current deviation, and set the above-mentioned first welding current deviation to the previous welding current deviation. The second welding speed correction command value is determined based on the second welding current deviation obtained by adding it to the deviation measured in the previous oscillation half cycles, and then the second welding speed correction command value is output for a predetermined period within each oscillation half cycle. A third welding speed correction command value is obtained by adding the first welding speed correction command value and the second welding speed correction command value output during each oscillation half cycle, and this third welding speed correction command value is The welding speed command value obtained by adding the initial welding speed command value and the welding speed command value is set as the welding speed command value for the next oscillation half cycle. After setting the oscillation center position correction value for each of a plurality of sections divided according to the magnitude of the deviation between the welding current average values of a predetermined section in the position, the oscillation center position of the welding torch is Measure the welding current average values in a predetermined section at the other end side position and compare them with each other to determine the deviation between both welding current average values, and determine which of the above preset categories the magnitude of the deviation corresponds to. In the second invention, the oscillation center position is corrected every predetermined oscillation cycle based on the oscillation center position correction value corresponding to the discriminated classification.
In addition, (c) the oscillation width is increased or decreased every predetermined oscillation half cycle in response to the second welding current deviation or the second welding speed correction command value obtained every oscillation half cycle. It is something. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a consumable electrode type gas-shielded arc welding apparatus (in an upward welding position) to which the present invention is applied. In the figure, 1 is a base material to be welded which has a V-shaped groove with a groove width, 2 is a ceramic backing material used in the first layer of Uranami welding, 3 is a restraining plate of base material 1, and 4 is a welding torch, 5 is a welding wire, 6 is a rail, 7 is a trolley that runs on the rail 6, 8 is a trolley drive motor,
9 is a vertical axis slider, 10 is a vertical axis slider drive motor, 11 is a left and right axis slider, 12 is a left and right axis slider drive motor, 13 is a welding torch 4 connected to base material 1
14 is a drive motor for the oscillating device, 15 is a contact type detection unit for detecting the surface position of the base material 1, and 15 is a contact type detection unit for detecting the surface position of the vertical axis slider 9 relative to the slide base position. The displacement of the surface position (height) of the material 1 is detected. This detector 15 is connected to the oscillator 13
It is also attached to the left and right axis slider 11. 16 is an arc welding power source, 17 is a current detector for detecting a welding current, and 18 is a control device, each of which has a block configuration shown in FIG. In FIG. 2, reference numeral 19 denotes a vertical positional deviation determination circuit, which takes in the displacement (signal) detected by the detector 15 and determines whether the displacement increases or decreases. 20 is a servo amplifier that drives the vertical axis slider drive motor 10 (M4) in the direction in which the slide base moves upward or downward in accordance with the increase or decrease command output by the vertical position deviation determination circuit 19, and The distance between the surface position of the base material 1 and the slide base position of the shaft slider 9 is adjusted to a set distance H ₀ set by the vertical position setting device 21.
Thereby, the reference position of the holding part of the welding torch 4 follows the vertical displacement of the surface of the base material 1. 22 is a servo amplifier for the left and right axis slider drive motor 12 (M3), 23 is a left and right position setting device,
This is manually operated to cause the left and right axis slider 11 to perform an inching operation. 24 is a servo amplifier for the drive motor 14 (M2) of the oscillating device 13, and has a function of controlling the oscillating pattern. 25 is a manually operated oscillation width setting device, 26
is a manually operated oscillation period setting device. 27
is a timing signal generation circuit which generates a timing signal for control, which will be described later, based on an oscillation left end stop signal _PL of the welding torch 4, an oscillation right end stop signal _PR and an operation sequence signal from the oscillation pattern control signal of the servo amplifier 24. _P1
~Create _P7 . The welding current (signal) output by the current detector 17 is passed through a low-pass filter 28 and then sent to an amplifier circuit 29.
is amplified. This low-pass filter 28 is provided to remove high frequency components caused by the commercial frequency of the arc welding current 16 and noise components accompanying the transfer of arc droplets. 30 is an average value circuit which takes in the welding current I amplified by the amplifier circuit 29 and measures the welding current average value I _A in synchronization with the timing signal from the timing signal generation circuit 27. 31 and 32 are sample hold circuits, and the sample hold circuit 31 is connected to the welding torch 4.
The sample hold circuit 32 samples and holds the welding current average value I _ALR measured by the average value circuit 30 when the welding torch 4 is oscillated from the right end to the right end. The welding current average value I _ARL measured by the value circuit 30 is sampled and held. Welding current average values I _ALR and I _ARL held in these sample hold circuits 31 and 32, respectively
Both are guided to the adder circuit 33. Addition circuit 3
3 is the value I _AS = (I _ALR + I _ARL )/
2 (hereinafter, this value will be referred to as the welding current measurement value) and output the updated value. Welding current measurement value I _AS is A/
After being read into the D converter 34, the D/A converter 3
5, and the differential amplifier circuit 36. The A/D converter 34 receives a reading command created by an operator operation after welding starts. Further, the D/A converter 35 holds the welding current measurement value I _AS inputted by the read command as the welding current reference value I _AC . The differential amplifier circuit 36 then outputs the welding current reference value.
The welding current deviation ΔI between I _AC and the measured welding current value I _AS is amplified and sent to the dead band circuit 37. Dead band circuit 3
7 performs dead band processing on the welding current deviation ΔI and converts the processed signal ΔI _DN (hereinafter referred to as the first welding current deviation) into the first
level conversion circuit 38 and deviation update processing circuit 3
Output to 9. The first level conversion circuit 38 converts the level of the first welding current deviation I _DN into a first welding speed correction command value ΔS _{DN, and converts this first welding speed correction command value ΔS DN into} an oscillation half cycle. A switch circuit 40 that is conductive only for a predetermined period within the oscillation half cycle each time.
The output signal is output to the adder circuit 41 via the adder circuit 41. On the other hand, the deviation update processing circuit 39 adds and updates the first welding current deviation ΔI _DN every oscillation half cycle, and converts the processed signal ΔI _DNSUM (hereinafter referred to as the second welding current deviation) into the second welding current deviation. It is output to the level conversion circuit 42. This level conversion circuit 42 converts the second welding current deviation
The level of I _DNSUM is converted into a second welding speed correction command value ΔS _DNSUM , and this second welding speed correction command value ΔS _DNSUM is output to the addition circuit 41 over the oscillation half cycle. The addition circuit 41 receives the first welding speed correction command value ΔS _DN from the switch circuit 40 and the second welding speed correction command value ΔS DN from the second level conversion circuit 42.
and the welding speed correction command value ΔS _DNSUM are added and output as the third welding speed correction command value ΔS _N. Further, 43 is an adder circuit, and this adder circuit 43 receives the initial welding speed command value S _KO created by the initial welding speed command device 44 and the third
and the welding speed correction command value Δ _SN are added and supplied to the servo amplifier 45 for driving the trolley drive motor 8 (M1). Reference numeral 46 denotes an inching speed setting device for manually inching the trolley 7. Note that, as shown in FIG. 3, the adder circuit 33 includes an operational amplifier A1, and the differential amplifier circuit 3
6 is configured with an operational amplifier A2. The differential amplifier 36 also includes an abnormal deviation detection circuit 36A.
is attached, and this abnormal deviation detection circuit 36A
are operational amplifiers A3 and A4, voltage comparators C1 to C
3 and NOT gate G1, and drives an analog switch AS1 in order to cope with short-term arc breakage and arc instability that occur during welding. Furthermore, as shown in FIG. 4, the dead band circuit 37 includes operational amplifiers A5 to A7, and outputs a zero value when the welding current deviation ΔI is within the dead band (E ₂ to −E ₂ ). The first level conversion circuit 38 includes operational amplifiers A8 and A9, and the deviation update processing circuit 39 includes a sample hold circuit SH1, a sample hold circuit SH2 that holds the output of the sample hold circuit SH1, and an operational amplifier. The switch circuit 40 includes analog switches AS2 and AS3, and the adder circuit 41 includes an operational amplifier A10.
It consists of 11 parts. Further, the second level conversion circuit 42 includes operational amplifiers A12 and A13, and the addition circuit 43 includes an operational amplifier A14. Next, a circuit section for controlling left and right welding line tracing will be explained. In FIG. 2, 47 is an average value circuit which takes in the welding current I amplified by the amplifier circuit 29 and calculates the welding current average value every half period of oscillation in synchronization with the timing signal from the timing signal generation circuit 27. Measure I _B. Reference numerals 48 and 49 are sample and hold circuits, and the sample and hold circuit 48 samples and holds the oscillated right-end side welding current average value I _AR measured by the average value circuit 47, and the sample and hold circuit 49 The oscillation left end side welding current average value I _AL measured by the average value circuit 47 is sampled and held. 50 is a differential amplifier circuit, which has an oscillation right end side welding current average value I _AR
Then, the average value IAL of the welding current on the left end side of the oscillation is derived, and the deviation ΔI _A between the two is measured. This deviation ΔI _A is removed by the abnormal deviation detection circuit 51 to become a welding current deviation ΔI _B , and this deviation ΔI _B is input to the deviation determination discrimination circuit 52. The deviation judgment discrimination circuit 52 has a plurality of sections divided in advance according to the size of the deviation ΔI _B (in this embodiment, as will be described in detail later, if the deviation is small, including no deviation, if the deviation is small, if the deviation is The oscillation center position correction value is set for each of the three categories (in the case of a large degree and in the case of a large case), and the deviation judgment discrimination circuit 52 detects a weld that indicates the deviation of the oscillation width center position with respect to the target weld line (groove line). Determine and discriminate whether the current deviation ΔI _B corresponds to any of the above categories, and send a slider shift command to the servo amplifier 22 to control the movement of the left-right axis slider 11 based on the correction value corresponding to the discriminated category. I try to do that. Note that FIG. 5 shows the sample and hold circuits 48, 4.
9. Differential amplifier circuit 50 and abnormal deviation detector 51
FIGS. 6 and 7 are circuit diagrams specifically showing the deviation determination discrimination circuit 52. In FIG. 5, A16 to A18 are operational amplifiers, and C4 to
C6 is a voltage comparator, GN is a NOT gate, and AS4 is an analog switch. In addition, in FIG. 6, A19 to A23 are operational amplifiers, and in FIG. 7, A24 is an operational amplifier, C7 to C10 are voltage comparators, 101 to 111 are NOT gates, and 1
12-121 are AND gates, 122-125 are
OR gate, 126-133 are NAND gates, IC
1 to IC4 are BCD counters for discriminating judgment, T1
~T4 is a timer, VR10, VR20, VR30,
VR40 is a variable resistor, TR1 to QR4 are transistors, and RR and RL are relays. In addition, Figure 5~
The detailed functions of the circuit shown in FIG. 7 will be described later. The operation of the above device will be explained below based on the timing signals _P1 to _P15 shown in FIG. In FIG. 8, I indicates the welding current signal input to the average value circuit 30 (actually, it is a sinusoidal waveform with distortion in synchronization with the oscillation period of the welding torch 4, but for convenience, (shown as a triangular wave). The oscillation left end position signal P _L and the oscillation right end position signal P _R are each oscillated by the oscillator 1.
3 is a pulse that rises when it reaches the left end L and right end R and stops, and then falls when it starts moving in the opposite direction. The period t ₀ is the operating period of the welding torch 4 within the oscillation half cycle (the stopping period is period). The timing signal P ₁ is the signal P _L ,
The _timing signal P ₂ is an extremely narrow pulse that rises in synchronization with the rise of _P It becomes a command. The timing signal P ₃ is a pulse with an extremely narrow width that is generated in synchronization with the even numbered sequence of the timing signal P ₁ and serves as a sample/hold command for the sample and hold circuit 31 . When the timing signals P ₂ and P ₃ are both at H level, they serve as a sampling command, and when they are at L level, they serve as a hold command. Further, the timing signal _P4 is a pulse with a predetermined width _tDS that rises in synchronization with the falling of the position signals P _L and P _R , and the average value circuit 30 is reset during the H level period of the timing signal _P4 . , welding current average values I ALR and _{I ARL} for periods t _ALR and t _ARL from the falling edge of the signal to the falling edge of the timing signals P ₃ and P ₂ , respectively, are calculated. In addition,
Normally, the pulse widths of the position signals _PL and _PR are set to be equal, so the periods t _ALR and t _ARL are equal. Furthermore, the timing signal _P4 period _tDS is provided to eliminate the influence of variations in the oscillation rate width on the groove width. For example, if the oscillation half cycle is about 1 second, the period t _DS is about 300 msec. Furthermore, the timing signal _P5 is the timing signal
This pulse has an extremely narrow width and rises in synchronization with the falling edge of _P1 , and serves as a sample/hold command to the sample/hold circuit SH1 of the deviation update processing circuit 39 shown in FIG. Timing signal _P6
is an extremely narrow pulse that rises in synchronization with the falling edge of the timing signal _P5 , and is a sample hold circuit of the deviation update processing circuit 39 shown in FIG.
This is a sample/hold command for SH2.
Both of these timing signals P ₅ and P ₆ serve as a sampling command when at an H level, and serve as a hold command when at an L level. The timing signal _P7 is a pulse with a predetermined width _tS that rises in synchronization with the rise of the timing signal _P1 , and
0 switch ON/OFF command. On the other hand, the timing signal _P8 is a pulse with a predetermined width _tDA that rises in synchronization with the rise of the position signals P _L and P _R , and the timing signal _P9 has a predetermined width that rises in synchronization with the fall of the timing signal _P8 . _tA
This is the pulse of The timing signal P ₁₀ is a pulse with an extremely narrow width that rises in synchronization with the falling edge of the timing signal P ₉ that occurs every odd number, and serves as a sample/hold command for the sample and hold circuit 49 shown in FIG. Further, the timing signal _P11 is a pulse with an extremely narrow width that rises in synchronization with the falling edge of the timing signal _P9 that occurs in an even numbered order, and serves as a sample/hold command for the sample and hold circuit 48 shown in FIG. Both of these timing signals P ₁₀ and P ₁₁ serve as a sampling command when at an H level, and serve as a hold command when at an L level. The average value circuit 47 is reset by the H level of the timing signal P ₆ and starts measuring the welding current average value I B from the rise of the timing signal P ₉ , but the sample hold circuit 49 starts measuring the welding current average value I _B from the rise of the timing signal P ₉ . The average value of welding current I AL is held on the left side of the period t _AL from the rise of the timing signal P 10 to the fall of the timing signal P 10, and the sample hold circuit ₄₈ holds the welding current average value I _AL on the left side of the period t _AR from the rise of the timing signal P ₉ to the fall of the timing signal P ₁₁ . Welding current average value I _AR
hold. Furthermore, as shown in FIG. 8, the timing signal _P12 is a very narrow pulse that rises in synchronization with the falling edge of the timing signal _P10 or _P11 , and rises twice every 1.5 oscillation periods. , the deviation judgment discrimination signal of the deviation judgment discrimination circuit 52 (AND gates 114 to 117, 119,
121), and this timing signal
It is used to judge and discriminate the value of welding current deviation _ΔIB during the H level period of _P12 . Furthermore, the timing signal _P13 is a narrow pulse that falls once every 1.5 oscillation cycles in synchronization with the falling edge of _the timing signal _P9 , without being synchronized with the timing signal P12. ₁₄ is a narrow rising pulse obtained by inverting the timing signal P ₁₃ and then slightly delaying the timing signal P ₁₃ .
BCD counter IC1 for deviation judgment discrimination in 2
Load signal to IC4, timing signal _P14
are BCD counters IC1 to IC4 for deviation judgment discrimination in the deviation judgment discrimination circuit 52 also shown in FIG.
These are preset signals inputted to the respective OR gates 122-125. As shown in FIG. 8, the timing signal P ₁₅ is connected to the timing signal P ₁₂ only once every 1.5 oscillation periods.
This signal rises from the rising edge of P14 to the rising edge of the timing signal _P14 , and is a carry signal output from the BCD counters IC1 to IC4 for discriminating deviation determination shown in FIG. Now, prior to starting welding, welding condition parameters are set by the operator. When oscillation welding is started, an operation is started to maintain a constant distance between the reference position of the holding part of the welding torch 4 and the surface of the base metal 1, and the welding current is detected through the current detector 17. The welding current is passed through a low-pass filter 28 and an amplifier 29 to an average value circuit 3.
It is input to 0. Among the welding current average values I _A calculated by the average value circuit 30, the average value I _ALR of the above period t _ALR
is held in the sample hold circuit 31 by the timing signal _P3 , and the average value of the above period t _ARL
I _ARL is held in the sample hold circuit 32 by the timing signal _P2 . Then, the held average values I _ALR and I _ARL are added to an adder circuit 3 with a gain of 1/2.
3, and its output is the welding current measurement value I _AS
We get = (I _ALR + I _ARL )/2. This welding current measurement value
The value of I _AS is updated every oscillation half cycle by timing signals P ₃ and P ₂ (including cases where the value does not change) in accordance with the oscillation welding signal. Here, the meaning of using the value I _AS as the welding current measurement value is to eliminate the variation in the average value of the welding current measured every half cycle of the oscillation, which occurs even when there is no increase or decrease in the groove width. This is to measure changes in welding current due to fluctuations in width at every oscillation half cycle. After welding starts, the operator checks the welding condition parameters and readjusts each parameter if necessary. The welding speed set value _SKO is adjusted using the initial welding speed command device 44. After the adjustment is completed, the operator issues a reading command to the A/D converter 34 by operating, for example, a reading stamp on an operation panel (not shown). This reading command is for initializing the welding current reference value, and upon receiving it, the A/D converter 34 takes in the above-mentioned welding current measurement value I _AS from the addition circuit 33 and converts it into a digital signal value. It is converted and sent to the D/A conversion circuit 35. The D/A converter 35 converts the digital measured value I _AS into an analog signal value and holds it as a welding current reference value I _AC until the end of welding. After setting the welding current reference value I _AC , switch SW1 in Fig. 4, which had been in the ON state, is turned OFF, and switch SW1, which had been in the OFF state until then, is turned OFF.
Welding speed control is started by turning on the switch SW2 shown in the figure. Thereafter, the welding current measurement value I _AS measured every half period of the oscillation is compared with the welding current reference value I _AC , and the welding current deviation ΔI =
G·(I _AS −I _AC ) is output from the differential amplifier circuit 36 (G is the gain). Here, the abnormal deviation detection circuit 36A shown in FIG.
I will explain about it. Note that this abnormal deviation detection circuit 36A is omitted from illustration in FIG. The abnormal deviation detection circuit 36A is provided with a set value _E1 , and when the absolute value of the output ΔI of the differential amplifier circuit 36 becomes larger than the set value _E1 , the analog switch AS1 is turned on and the differential amplifier circuit 3 is turned on.
The output ΔI of 6 is connected to ground via a resistor. As a result, the dead band circuit 37 in FIG.
Since =0 is input, the welding speed (traveling speed of the trolley 7) is maintained at the speed before ΔI=0 was input. In addition, the differential amplifier circuit 3
When the absolute value of the output ΔI of 6 is within the set value E ₁ ,
The analog switch AS1 is in the OFF state and is in a normal state, that is, the output ΔI of the differential amplifier circuit 36 is input to the dead band circuit 37 as is. In this way, the abnormal deviation detection circuit 36A can deal with short-term arc breakage and arc instability that occur during welding. Note that the set value _E1 is set to, for example, a value of about 10 amperes. Now, the welding current deviation ΔI from the differential amplifier circuit 36 is input to the dead zone circuit 37 shown in FIG. The dead band circuit 37 is provided with a dead band setting value ±E ₂ , and when the deviation ΔI is −E ₂ ≦ΔI ≦E ₂ , ΔI _DN =
0, when ΔI>E ₂ , ΔI _DN = ΔI−E ₂ , ΔE ₂ <−E ₂
In this case, the dead band circuit 37 outputs a signal ΔI _DN that has been subjected to dead band processing such that ΔI _DN =ΔI+E ₂ .
Here, the set value _E2 is set to, for example, a value of about 1 ampere. The current deviation ΔI _DN obtained by the dead zone circuit 37 is defined as a first welding current deviation, and this first welding current deviation ΔI _DN is sent to the first level conversion circuit 38 and the deviation update processing circuit 39 . The first level conversion circuit 38 converts the signal value level of the first welding current deviation ΔI _DN into a first welding speed correction command value ΔS _DN , and the speed-converted first welding speed correction command value ΔS _DN . is sent to the adder circuit 41 via the analog switch AS2 of the switch circuit 40. Note that the analog switch AS2 is turned on when the timing signal _P7 is at the H level (predetermined width _ts ), and turned off when the timing signal P7 is at the low level. Conversely, the analog switch AS3 is turned OFF when the timing signal P7 is at the H level, and turned ON when the timing signal _P7 is at the L level.
As a result, the first welding speed correction command value ΔS _DN is input to the addition circuit 41 over a predetermined period t _S within each oscillation half cycle. Here, the period t _S is, for example, about 300 msec in the upward first layer welding of this embodiment. The relationship between this period t _S and the left and right end stop periods _PL and _PR of the oscillation is preferably such that t _S ≦ _PL and _PR . On the other hand, the sample hold circuit SH1 of the deviation update processing circuit 39 uses the first welding current deviation ΔI _DN measured in the current oscillation half cycle using the timing signal _P5 , and the sample hold circuit SH2 according to the timing signal _P6 . Sample and hold the added value ΔI _DNSUM with the output ΔI _DN-1SUM . Here, ΔI _DN-1SUM = _N-1 〓 ^N=0 ΔI _DN (However, ΔI _D0 = 0), and this value is the current from the completion of setting the welding current reference value I _AC to the previous half cycle of oscillation. This is the accumulated value (total value) of the deviation ΔI _DN , and the obtained additional value ΔI _DNSUM is the accumulated value (total value) of the welding current deviation ΔI _DN from the completion of setting the welding current reference value I _AC to the current oscillation half cycle. ). In other words, the deviation update processing circuit 39 updates the welding current deviation ΔI _DN measured every oscillation half cycle from the time when the setting of the welding current reference value I _AC is completed and the speed control operation is started until now.
Functions as a register to accumulate. Note that, as a matter of course, the welding current deviation ΔI _DN takes values of 0, positive, and negative. The welding current deviation ΔI _DNSUM obtained by the sample hold circuit SH1 in this manner is set as a second welding current deviation, and this second welding current deviation ΔI _DNSUM is sent to the second level conversion circuit 42. The level conversion circuit 42 converts the second welding current deviation ΔI _DNSUM into a second welding current deviation ΔI DNSUM.
The signal value level is converted into a welding speed correction command value ΔS _DNSUM and sent to the addition circuit 41. The addition circuit 41 adds the first welding speed correction command value ΔS _DN from the switch circuit 40 and the second welding speed correction command value ΔS _DNSUM from the second level conversion circuit 42 to obtain the third welding speed correction command value ΔS DNSUM. Welding speed correction command value ΔS _N (=ΔS _DN +
ΔS _DNSUM ) is determined and sent to the adder circuit 43 at the next stage. Then, the addition circuit 43 outputs the initial welding speed command value S _KO set by the variable resistor VR1 in the initial welding speed command device 44 and the third
and the welding speed correction command value ΔS _N and send the obtained added value S _N+1SUM (=S _KO +ΔS _N ) to the servo amplifier 45 as the welding speed command value in the next oscillation half cycle. Depending on the welding current reference value
The welding speed [the speed of the trolley drive motor 8 (M1)] is controlled to increase or decrease so as to cancel the deviation ΔI between I _AC and the measured welding current value I _AS . In addition, among the welding current average values I _B measured by the average value circuit 47, the left end side welding current average value I _AL in the period t _AL is held in the sample hole circuit 49 by the command of the timing signal P ₁₀ , and The right-end side welding current average value _IAR at _AR is held in the sample hole circuit 48 in response to a timing signal _P11 . Then, the differential amplifier circuit 50 operationally amplifies the deviation between the left end side welding current average value I _AL and the right end side welding current average value I _AR from these sample hold circuits 48 and 49 to obtain a welding current deviation ΔI _A = Output as G・(I _AL −I _AR ) (where G is gain). This welding current deviation ΚI _A is determined by the abnormal deviation detection circuit 5
1, this abnormal deviation detection circuit 51
is configured in the same manner as the above-mentioned abnormal deviation detection circuit 36A, and has a set value E _AN in advance, and when the absolute value of the output ΔI _A of the differential amplifier circuit 50 becomes larger than the set value E _AN , the analog switch AS4 is activated. It is in the ON state and the output ΔI _A of the differential amplifier circuit 50 is connected to the ground via the resistor. As a result, ΔI _B =0 is input to the shift determination discrimination circuit 52, and the oscillation center position is not corrected, but the oscillation center position is maintained. Furthermore, when the absolute value of the output ΔI _A of the differential amplifier circuit 50 is within the set value E _AN , the analog switch AS4
The state is OFF, and the normal state is entered, that is, a state in which the output ΔI _A of the differential amplifier circuit 50 is inputted as is to the deviation determination discrimination circuit 52 (ΔI _B =ΔI _A ).
In this way, the abnormal deviation detection circuit 51 can deal with short-term arc breakage and arc instability that occur during welding. Note that the above setting value E _AN
For example, a value of about 10 amperes is set. Next, the welding current deviation ΔI _B from the differential amplifier circuit 50
The displacement judgment discrimination circuit 52 will be explained with reference to FIGS. 6 and 7. The basic operation of this deviation judgment discrimination circuit 52 is to perform three-value judgment discrimination on welding current deviation ΔI _B having positive and negative polarities. Figure 6 shows the first upper limit value E _U1 = E ₂ for determining the welding current deviation ΔI _B ;
Second upper limit value E _U2 = (E ₂ + E ₃ ), first lower limit value E _L1 = (E ₂
−E ₄ ), and the second lower limit E _L2 =−(E ₂ +E ₃ ). Here, if the set value E ₄ =2E ₂ , the first lower limit value E _L1 becomes −E ₂ . These setting values are set to, for example, approximately E _U1 =2.5 amperes (A), E _U2 =5.0 amperes, E _L1 =-2.5 amperes, and E _L2 =-5.0 amperes. In addition, in the circuit shown in Figure 6, each set value E _U1 , E _U2 , E _L1 , E _L2 can be changed in the positive or negative direction simply by resetting the set value E ₂ using a variable resistor. . For this reason, it is possible to control the left and right tracing of the weld line not only in multilayer welding with one pass for each layer, but also in distributed welding in multiple passes for each layer. Now _{, the} deviation _judgment discrimination circuit ₅₂ in _FIG . Output to. That is, E _L1 ≦ΔI _B ≦
AND gate 1 when E _U1 or |ΔI _A |＞E _AN
Each output of 14 to 117 becomes L level, and E _U1 <
When I _B ≦E _U2 , the error judgment discrimination signal (timing signal) _P12 is the clock terminal of BCD counter IC2.
CK, and when E _U2 < ΔI _B ≤ E _AN , the signal P ₁₂
is input to the clock terminal CK of the BCD counter IC1. Then, when E _L2 ≦ΔI _B < E _L1 , the signal P ₁₂ is
The signal P12 is input to the clock terminal CK of the BCD counter IC4, and when -E _AL ≦ΔI _B <E _L2 , the signal _P12 is input to the BCD counter IC3. Here, the BCD counters IC1 to IC4 are set so that the welding current deviation ΔI _B obtained in two consecutive oscillation half cycles falls into one of the sections divided as described above.
By confirming that the welding torch 4 continues to exist, it is possible to eliminate malfunctions due to the adverse effects of welding current fluctuations caused by arc instability, and to accurately recognize the positional deviation of the welding torch 4. For this, BCD
Counters IC1 to IC4 are supplied with timing signal _P13 and
_P14 is input every 1.5 oscillation cycles, and BCD7 is preset in each BCD counter IC1-IC4. Then, for example, it is determined that the welding current deviation ΔI _B is E _U1 <ΔI _B ≦E _U2 , and the deviation determination discrimination signal P ₁₂ is output to the BCD counter IC2.
If it arrives twice within the period t _C (see Figure 8), then
The contents of BCD counter IC2 count up from BCD7 to BCD9, and timing signal _P15 is output from carry terminal CO. Then, at the rising edge of the timing signal _P15 , the triggered timer T2 turns on, and the transistor TR
Turn on relay RR via 2. The ON time of timer T2 is set by variable resistor VR20. When the relay RR turns on, the relay contact signal is sent to the servo amplifier 22, and the drive motor 12 (M3) drives the left and right axis slider 11.
The oscillation center position is corrected by moving the oscillation center position to the right by a predetermined oscillation center position correction value. Furthermore, when relay RR is turned on, the position is corrected to the right.
When relay RL is turned on, the position is corrected to the left. Further, it is desirable that each position correction is completed within half an oscillation cycle after the timing signal _P15 rises. In addition, in this embodiment, the correction operation (correction value includes zero time) is 1.5 of the oscillation period.
The configuration is such that commands are given every cycle, and the welding current deviation ΔI _B
Although the size is divided into three categories, the correction period and the number of categories are not limited to these. Below, using Tables 1 and 2, the judgment discrimination operation of the welding current deviation ΔI _B according to this embodiment is summarized.
In Table 1, No. 1 is when the magnitude of the welding current deviation ΔI _B is small (including zero), and No. 2 and No. 3 are when the magnitude of the deviation ΔI _B is medium and the sign is opposite. In case No. 6, an abnormal state is detected by the abnormal deviation detection circuit 51.

【table】

[Table] No. 2 to No. 5 are cases in which each welding current deviation ΔI _B is judged and discriminated twice in a row within the period t _C.
No. 7 and No. 8 in Table 2 have moderate deviations ΔI _B within the period t _C.
The operation is shown when ΔI B is determined once and a large deviation ΔI _B is determined once. In this case, in this embodiment, the same correction value as the medium deviation ΔI _B is output. Here, the reason why the magnitude of the welding current deviation ΔI _B is differentiated into medium and large cases and different oscillation center position correction values (0.3 mm, 0.5 mm) are set for each case will be explained. The reason for this is that from the experimental results, when the deviation ΔI _B is medium, it is a deviation caused by the deviation between the oscillation center position and the target weld line, and when the deviation ΔI _B is large, it is a sudden deviation. This is due to the knowledge that the deviation is caused by the bending of the welding wire that occurs in the welding process or the overlap between the bending of the welding wire and the welding line. In this way, in this embodiment, the initially set welding speed command value S _KO is
Welding is performed while correcting the welding speed correction command value ΔS _N , and the welding speed command value S _N+1SUM becomes the initial welding speed command value S _KO at the N+1st oscillation half cycle.
and the first welding speed correction command value ΔS DN and the second welding speed correction command value ΔS _DN obtained based on the first welding current deviation ΔI _DN and the second welding current deviation ΔI _DNSUM measured in the Nth oscillation half cycle. This is the added value of the third welding speed correction command value ΔS _N , which is the sum of the welding speed correction command value ΔS _DNSUM [see FIGS. 9c and d]. In other words, the welding speed command value S _N+1SUM is
Welding speed command value in the Nth oscillation half cycle
This is the sum of S _NSUM and (ΔS _N −ΔS _N-1 ), and the speed command value ΔS _N obtained by measuring the current deviation in this time (Nth oscillation half cycle) is the same as the previous value (ΔS N −ΔS N-1).
Only when the welding speed correction command value ΔS _N-1 obtained in the first oscillation half cycle has increased or decreased, the welding speed command value S _NSUM is corrected by the increase or decrease and the next N+1st The welding speed command value is set to a half-oscillation cycle. Here, the first welding speed correction command value ΔS _DN and the second welding speed correction command value ΔS _DNSUM created from the welding current deviation ΔI _DN and ΔI _DNSUM are described below.
Explain the meaning of. Conversion ratio of second welding speed correction command value ΔS _DNSUM to second welding current deviation ΔI _DNSUM (second level conversion circuit 42
gain) is fixed, so only the second welding speed correction command value ΔS _DNSUM is used as the initial welding speed command value.
When calculating the welding speed command value by adding it to S _KO , the groove width fluctuation, which is indirectly detected as the welding current fluctuation, and the second welding speed correction command value ΔS _DNSUM
A deviation inevitably occurs between the welding speed and the welding speed, resulting in poor responsiveness. Therefore, a new first welding speed correction command value ΔS _DN is introduced, and the superposition of the first welding speed correction command value ΔS _DN and the second welding speed correction command value ΔS _DNSUM is used as the welding speed correction command value. By doing so, sufficient followability can be obtained. This is because the first welding speed correction command value ΔS _DN complements the excess or deficiency of the welding speed caused by the second welding speed correction command value ΔS _DNSUM , and also has a differential element with respect to increases and decreases in the groove width. This is because a rapid response effect can be obtained by using the same method. By the way, in this embodiment, the current values used to determine the positional deviation of the welding torch 4 in the left-right direction (groove width direction) with respect to the target welding line are the left-end average value I _AL and the right-end average current value I Since it is _AR ,
Even under unstable welding conditions, the arc accompanied by short-circuit droplet transfer can be sufficiently eliminated, so accurate left-right positional deviation can be determined, and accurate left-right tracing of the welding line can be achieved. Moreover, welding current deviation ΔI _B
Since the value of is divided into multiple sections and the oscillation center position correction value of the welding torch 4 is set for each section, adaptive control can be quickly performed even in the event of arc breakage or sudden bending of the welding wire. can be done. In addition, in the case where the groove width fluctuates as shown in FIG. 9a, the output pattern of the welding speed command value according to the embodiment of the present invention is shown in FIGS. 9c and d, and the welding speed command according to the conventional technology The value output pattern is shown in FIG. 9f. However, Fig. 9c shows the output pattern of the ideal welding speed command value, and Fig. 9d shows the output pattern of the ideal welding speed command value.
shows the output pattern of the actually obtained welding speed command value. Further, in the above embodiment, the speed control method in oscillated welding has been explained, but even in straight welding in which the welding torch 4 is not oscillated, signals corresponding to the position signals P _L and P _R in FIG. 8 or 9b can be used. By creating , the method of the present invention can be applied. [Embodiment of the Second Invention] FIG. 10 shows an embodiment of the second invention, which differs from the embodiment of the first invention in that it has an oscillation width control function. In FIG. 10, 53 is a third level conversion circuit, 54 is an addition circuit, and these third level conversion circuits 53
and an adder circuit 54 are added to the embodiment of the first invention. Further, as shown in FIG. 11, the third level conversion circuit 53 is composed of operational amplifiers A25 and A26, and a switch.
While connected to the adder circuit 54 via SW3,
The adder circuit 54 includes an operational amplifier A27, and the oscillation width setter 25 described above.
It is configured as a variable resistor that outputs an oscillation width initial command value W. 10 and 11, the third level conversion circuit 53 receives the second welding speed correction command value ΔS _DNSUM output from the second level conversion circuit 42,
The signal value level of the command value ΔS _DNSUM is converted into an oscillation width increase/decrease value ΔW. The converted oscillation rate increase/decrease value ΔW is input to the adder circuit 54 via the switch SW3, which is turned on by the oscillation width control start command, and the adder circuit 54 inputs the oscillation width initial value set by the oscillation width setter 25 to the adder circuit 54. It is added to the command value W. Then, the output (W-ΔW) from the adder circuit 54 is sent to the servo amplifier 24 as an oscillation width command value. here,
The oscillation width command value (W - ΔW) becomes ΔW < 0 and the value increases when the groove width is wider than the current one, and ΔW > 0 and the value increases when the groove width becomes narrower than the current one. Since the groove width decreases, the oscillation width can be controlled by following the variation in the groove width. In this way, in this embodiment, the second welding speed correction command value ΔS _DNSUM used for this oscillation width control is a more faithful and stable groove control value than the welding speed command value obtained by the conventional technology. Since it is a value indicating the increase/decrease variation in width, it is possible to control the oscillation width by extremely accurately following the variation in groove width. In addition, in the case where the groove width fluctuates as shown in FIG. 9a, the output pattern of the second welding speed correction command value ΔS _DNSUM according to this embodiment is
The welding speed correction command values are shown in Fig. 9e. Further, in this second invention, the same result can be naturally obtained even if the second welding current deviation ΔI _DNSUM is used instead of the second welding speed correction command value ΔS _DNSUM . [Effects of the Invention] As described above, in the present invention, the welding speed command value created for each oscillation half cycle is a third welding speed command value created by superimposing the first welding speed correction command value and the second welding speed correction command value. The first welding speed correction command value is obtained as the addition value of the welding speed correction command value of It has a differential element for the increase/decrease fluctuation in the groove width, and the welding speed command value is created by correcting the groove fluctuation in the welding speed that reached the previous oscillation half cycle. In addition to being able to faithfully and quickly adapt to fluctuations, the left-right tracing control of the welding line uses the average value of the welding current at the left and right ends of the oscillation, so there is no malfunction even under unstable arc conditions. Accurate tracing can be performed, and the welding current deviation, which represents positional deviation, is divided into multiple categories and judged, so bending of the welding wire or arc breakage can be quickly dealt with. According to the invention, more accurate and stable automatic control of the oscillation width can be realized.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an example of a welding device embodying the present invention, Fig. 2 is a block diagram of a control device in the above embodiment, and Figs. 3 to 7 each show a part of the above control device in detail. 8 is a waveform time chart of the timing signal in the above embodiment, FIG. 9a is a diagram showing an example of variation in groove width, and FIG. 9b is an output of the oscillation left and right end stop signals. Figures 9c and 9d are diagrams showing the pattern of the welding speed command value in the above embodiment, and Figure 9e is a diagram showing the pattern of the second welding speed correction command value in the above embodiment. , FIG. 9f is a diagram showing a pattern of welding speed command values in a conventional welding speed control method, FIG. 10 is a block diagram showing another embodiment of the present invention, and FIG. 11 is one of the above other embodiments. FIG. In the figure, 1...Base material as the object to be welded, 4
... Welding torch, 13 ... Oscillating device, 19
... Vertical positional deviation determination circuit, 30 ... Average value circuit, 31, 32 ... Sample hold circuit, 33
... Addition circuit, 34 ... A/D conversion circuit, 35 ...
...D/A conversion circuit, 36...Differential amplifier circuit, 37
... Dead band circuit, 38 ... First level conversion circuit, 39 ... Deviation update processing circuit, 40 ... Switch circuit, 41 ... Addition circuit, 42 ... Second level conversion circuit, 43 ... Addition circuit , 47... Average value circuit, 48, 49... Sample hold circuit, 5
0... Differential amplifier circuit, 51... Abnormal deviation detection circuit, 52... Deviation judgment discrimination circuit, 53... Third level conversion circuit, 54... Addition circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In consumable electrode arc welding in which arc welding is performed while the welding torch is oscillated in the width direction of the groove while maintaining a constant distance between the welding torch holder and the surface of the workpiece, Measure the average value of the welding current for a predetermined period within each oscillation half cycle of the welding torch, and initialize this welding current measurement value as the welding current reference value. After initializing the welding speed, every oscillation half cycle. Compare the welding current measurement value measured in the current welding current reference value with the welding current reference value, and measure the deviation between the welding current measurement value and the welding current reference value in the current oscillation half cycle as a first welding current deviation. , a first welding speed correction command value is determined based on this first welding current deviation, and the first welding current deviation is added to the deviation measured in the previous oscillation half cycle to perform the second welding. After determining the current deviation and determining the second welding speed correction command value based on this second welding current deviation, the first welding speed correction command value and each oscillation rate are output for a predetermined period within each oscillation half cycle. A third welding speed correction command value is obtained by adding the above-mentioned second welding speed correction command value output during a half cycle, and this third welding speed correction command value and the initial welding speed command value are added. The welding speed of the next oscillation half cycle is controlled by the welding speed command value obtained by After setting the oscillation center position correction value for each of multiple sections divided according to the size of the After measuring each value and comparing them with each other to find the deviation between the average values of both welding currents, and determining which of the above preset categories the magnitude of the deviation corresponds to,
A groove adaptive control method for consumable electrode type arc welding, characterized by performing left and right tracing of a weld line, correcting the oscillation center position at every predetermined oscillation cycle based on the oscillation center position correction value corresponding to the discriminated classification. . 2. The consumable electrode type arc according to claim 1, wherein the welding current measurement value is an arithmetic average value of welding current average values for a predetermined period within two consecutive oscillation half cycles. Welding groove adaptive control method. 3. In consumable electrode arc welding in which arc welding is performed while the welding torch is oscillated in the groove width direction while maintaining a constant distance between the welding torch holder and the surface of the workpiece, each oscillation rate of the welding torch is The average value of the welding current for a predetermined period within a half cycle is measured, and this welding current measurement value is initially set as the welding current reference value, and after the welding speed is initialized, the above-mentioned welding that is measured every oscillation half cycle is performed. The current measurement value is compared with the welding current reference value, and the deviation between the welding current measurement value and the welding current reference value in the current oscillation half cycle is measured as a first welding current deviation. A first welding speed correction command value is determined based on the current deviation, and a second welding current deviation is determined by adding the first welding current deviation to the deviation measured in the previous oscillation half cycle. After determining a second welding speed correction command value based on the second welding current deviation, the first welding speed correction command value is output for a predetermined period within each oscillation half cycle.The first welding speed correction command value is output during each oscillation half cycle. A third welding speed correction command value is obtained by adding the second welding speed correction command value, and the welding speed obtained by adding the third welding speed correction command value and the initial welding speed command value. The welding speed of the next half cycle of oscillation is controlled by the command value, and the welding current is controlled in advance according to the magnitude of the deviation between the welding current average values in a predetermined section at the oscillation position of the welding torch at one end side position and the other end side position. After setting the oscillation center position correction value for each of the plurality of divisions, measure the welding current average value of the welding torch in a predetermined section at one end side position and the other end side position of the welding torch, and compare them with each other. After comparing and determining the deviation between the average values of both welding currents and determining which of the above preset categories the magnitude of the deviation corresponds to,
The oscillation center position is corrected every predetermined oscillation cycle based on the oscillation center position correction value corresponding to the discriminated classification.The welding line is traced left and right, and on the other hand, the above-mentioned second welding line obtained every oscillation half cycle is performed. 1. A groove adaptive control method for consumable electrode type arc welding, characterized in that the oscillation width is increased or decreased every predetermined oscillation half period in response to a current deviation or a second welding speed correction command value. 4. The consumable electrode type arc according to claim 3, wherein the welding current measurement value is an arithmetic average value of welding current average values for a predetermined period within two consecutive oscillation half cycles. Welding groove adaptive control method.