JP3466166B2 - Rotary arc welding equipment and welding speed setting equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary arc welding control device, and more particularly to a rotary arc welding device adapted to obtain a constant bead leg length in fillet welding.

[0002]

2. Description of the Related Art High-speed rotary arc welding is a method of welding a torch to which a welding voltage is applied at a high speed of 20 to 100 Hz along a welding line, and does not require a special additional device around the torch and can be easily performed. Real-time control is possible and a smooth weld bead can be obtained. Even in high-speed rotary arc welding, there is a demand for labor saving by using robots and automatic machines. The main disturbance elements that must be controlled when mechanization of fillet welding is mechanics are welding line deviation and insufficient bead leg length. Of these, the weld line deviation is
This can be eliminated by measuring the arc voltage during rotation and controlling the position of the welding torch so that the voltage distribution across the welding direction is balanced on the left and right.

By the way, in fillet welding, a gap may occur between the lower plate member and the standing plate member joined to the lower plate member. Since the molten metal flows into the gap when there is a gap, the weld bead becomes smaller and the leg length becomes shorter than when there is no gap. The lack of bead leg length is due to this gap becoming too large depending on the location. Conventionally,
The fillet welding by the automatic welding device was similarly welded according to the welding conditions initially set, even if there was a gap on the welding line. When performing high-speed rotating arc welding, the gap amount is 2 because of the bead smoothing effect.
If the length is equal to or less than mm, the bead leg length is not short enough to cause a problem. However, if the gap becomes larger than this, the molten metal flows into the gap, so that the molten metal forming the bead becomes insufficient and the bead leg length becomes insufficient.

Japanese Patent Laid-Open No. 10-263821 discloses a welding condition adaptive control method for obtaining stable welding quality when performing fillet welding using an arc rotating at a high speed. In the disclosed method, the waveform of the welding voltage or welding current for one revolution of the arc is used, and the difference between the integrated value of the voltage or current in the phase section at the rear part of the arc rotation position and the integral value of the remaining portion, that is, the voltage. The waveform difference is used as a parameter for estimating the gap.

In the disclosed method, an experiment is conducted in advance to obtain a database of welding conditions considered to be appropriate for each size of the root gap, and the relationship between the size of the root gap and the parameter value under the given welding conditions. , Record in a storage device. Then, calculate the gap estimation parameter during welding, estimate the current gap amount from the correspondence table of the parameter value and the root gap under the same welding conditions, and weld under the same welding conditions unless the gap amount exceeds the allowable value. When the gap amount exceeds the permissible value, another proper welding condition which is obtained in advance is selected from the database and set again so that welding is performed.

Therefore, it is necessary to obtain the appropriate welding condition for each gap amount and the relationship between the gap amount and the parameter value for each welding condition in advance and make them into a database, so that various conditions can be met. Up to a huge amount of testing is required. Furthermore, when it is desired to change the weld bead leg length, it is necessary to prepare a database corresponding to the new weld bead leg length, and it is not easy to change the applicable range.

[0007]

Therefore, the problem to be solved by the present invention is to perform welding control for preventing shortage of the bead leg length even when there is an excessive gap or the like when performing horizontal fillet welding by high-speed rotary arc welding. A rotary arc welding apparatus using the method, and in particular, a rotary arc welding apparatus capable of feedback control with relatively few adjustment parameters.

[0008]

In order to solve the above problems, a rotary arc welding device according to the present invention comprises an arc voltage measuring device, a computing device, a control device, and a welding speed adjusting device, and is required by the arc voltage measuring device. The arc voltage value during arc rotation is input to the arithmetic unit, the arithmetic unit obtains a bead index given as a difference between respective average values of arc voltages in two phase regions having different arc revolutions, and the set feedback is set. The welding bead leg length is controlled to be constant by adjusting the welding speed so that the deviation from the target value of the bead index becomes small under the gain.

Even if other welding conditions such as welding voltage setting value, welding current setting value, distance between torch and work are not changed,
If the welding speed is slowed, the weld bead becomes large regardless of the presence or absence of a gap, and if the welding speed is fast, the weld bead becomes small. Further, the arc length is determined by the distance to the surface of the welding bead, and the change in arc length can be detected as the change in arc voltage generated in the arc.
In rotary arc welding, a change in bead shape, that is, a change in bead leg length can be observed as a change in arc voltage waveform pattern during arc rotation.

As a result of earnest research, the inventor of the present invention has found a method of obtaining a bead index that accurately reflects a bead shape by using an arc voltage waveform during arc rotation. The inventor
When the vertical plate is fillet-welded to the lower plate, the arc voltage waveform during rotation changes as the gap (also called the root gap) between the lower plate and the vertical plate increases, and the tendency of the change is the arc. It was found that it depends on the rotational phase region. The tendency of change has different stability depending on the phase position.

That is, the value obtained by integrating the arc voltage in a region corresponding to the lower plate where the position of the arc is in the forward direction of the welding is reduced as the gap is widened, and this tendency is considerably reproducible. Further, the value obtained by integrating the arc voltage in an appropriate region where the arc is located behind and in the rear of the welding proceeding direction is larger as the gap is opened, and this tendency is also highly reproducible. It was found that the arc voltage integrated value did not show a remarkable tendency or the reproducibility was poor in other phase regions.

Based on such knowledge, the inventor of the present application uses a difference between an integrated value of an arc voltage value in a rotating arc over a predetermined phase region and an integrated value over a predetermined region different from that as a bead index value. To do. In particular, in the phase region between the arc voltage integrated value in the phase region where the arc is in front of the welding advancing direction and is in contact with the lower plate portion of the welding member, and the predetermined angle between the positions where the arc is directly behind in the welding advancing direction. A bead index value (called a bead index) that closely matches the tendency of the gap, that is, the bead, and has stable interrelationship by using the difference in the integrated value of the arc voltage.
Becomes

If fillet welding is applied to a portion having a gap,
The arc length increases as the molten metal flows into the gap and the beads become smaller. However, the surface of the molten metal does not deteriorate so much on the front side of the rotation of the rotary torch because the molten pool is shallow, whereas on the rear side, the thickened molten metal is blown by the arc pressure and pushed into the gap, Since the amount of decrease on the surface of the molten metal is large, the change in arc length on the rear side of rotation is large. The fluctuation of the arc voltage is almost proportional to the fluctuation of the arc length. Thus, when the bead size changes due to the gap, the difference in arc voltage between the front side and the rear side of the arc rotation changes. It is considered that the bead index is related to the bead by the above mechanism.

The tendency that the arc voltage on the front side of the arc rotation becomes smaller as the gap becomes larger is particularly due to the torch axial copying control for adjusting the distance between the torch and the welded portion so that the welding current becomes constant. It is believed to be even more prominent in the device. In the torch axial direction scanning control, when the bead is small, the torch is adjusted closer to the lower plate. Then, the arc length becomes shorter and the arc voltage becomes lower. Therefore, when the gap becomes large and the bead becomes small, the arc voltage when the torch is in the front phase of rotation becomes small.

On the other hand, the change in the distance between the torch and the molten pool on the rear side in the welding proceeding direction becomes larger than the moving distance of the torch, so that the tendency of the arc voltage increase becomes more remarkable as the bead becomes smaller. Therefore, as the gap between the upright plate and the lower plate becomes larger and the bead becomes smaller, the arc voltage difference between the phase region where the arc is in the front of the welding advancing direction and the phase region where the arc is in the rear of the advancing direction becomes larger, and the bead size increases. Will reflect that.

Fillet welding is performed while changing the welding speed from high speed to low speed and from low speed to high speed with no gap, and the relationship between the bead index and the actual throat thickness or bead leg length of fillet welding is calculated for each welding speed. Upon inspection, the correlation coefficient between the actual throat thickness and the bead index is about -0.8 up to the actual throat thickness of about 8 mm, and the correlation coefficient between the bead leg length and the bead index is about -0.6 up to about 7 mm. It was proved that there is a property.

Also, according to an experiment of fillet welding a member assembled so that the gap amount gradually changes, the bead index does not change until the gap exceeds 2 mm,
It was confirmed that the bead index increased with the expansion of the gap in the larger region. Note that in high-speed rotary arc welding, the bead index corresponds very well to the bead leg length, considering that a gap of about 2 mm does not affect the bead leg length.

Similarly, by examining the relationship between the bead index and the actual throat thickness, it has been found that the bead index monotonically decreases as the actual throat thickness increases from about 2.5 mm. In this way, the bead index decreases as the bead leg length increases and the actual throat thickness increases.
It can be seen that the bead index corresponds to the bead size.

According to this bead index, Japanese Patent Laid-Open No. 10-2
Unlike the method disclosed in 63821, it is not necessary to estimate the gap value from the parameter value using the correspondence table, and it can be directly used as a substitute variable for feedback control. Furthermore, by adjusting the welding speed and maintaining the bead index at a constant value, the welding bead can be maintained in a constant shape even if there is a certain amount of gap. In addition,
A method of adjusting the supply amount of the welding wire for the purpose of adjusting the bead leg length may be considered. However, the method of controlling the wire supply amount has an advantage that the construction efficiency does not decrease, but since the welding voltage command value and the welding current command value of the welding power source must be adjusted according to the wire supply amount, the control is It has the drawback of being complicated. In addition, there is a problem that the characteristic of the bead index changes as the welding voltage supplied by the welding power source changes.

In the rotary arc welding device of the present invention,
The welding speed may be set at certain time intervals. Since the bead index is obtained by using the integral value for a predetermined phase region during arc rotation, the calculation result does not appear until at least one rotation of the torch. Further, when welding control is performed by an automatic machine such as a robot, it is controlled by a sequencer or the like, so there is no point in issuing a setting change command at intervals shorter than the control cycle.

In fillet welding, the gap amount rarely changes abruptly, and the bead shape does not change abruptly. Therefore, when the bead leg length is controlled using the alternative index, the controllability is not significantly impaired even by the intermittent control based on the measurement values obtained intermittently. Therefore, the command value may be calculated at an appropriate interval so as not to affect the welding quality, and the welding control device may be instructed.

Therefore, the rotary arc welding apparatus of the present invention may be constructed so that the welding speed can be set at an appropriate time interval longer than the time required for one rotation of the torch. When using intermittent control,
The calculation load of the control device is reduced, and it is not necessary to have sophisticated functions, and an economical welding system can be constructed.

Further, in the rotary arc welding apparatus of the present invention,
When changing the shape of the weld bead, for example, changing the bead leg length of 6 mm to 4 mm, the purpose is achieved only by resetting the target value of the bead index. It should be noted that when the bead index is changed, the welding conditions are changed, so it is preferable to reset the feedback gain that matches the new bead index.

The appropriate values of the bead index and feedback gain corresponding to the bead leg length and the actual throat thickness can be obtained in advance by a simple experiment. In such a configuration, the adjustment parameter is only two, that is, the bead index target value and the feedback gain, and therefore the adjustment is easy. Further, unlike the method disclosed in Japanese Patent Application Laid-Open No. 10-263821, it is not necessary to obtain the appropriate welding conditions and the like every time the gap amount changes, and the applicable range can be easily expanded.

Further, the welding speed setting device for a rotary arc welding device of the present invention comprises an arithmetic device and a control device, and the arithmetic device inputs the arc voltage value during arc rotation to obtain the phase voltage in different phase regions. Obtain the bead index given as the difference between the average arc voltage values, and use the feedback gain recorded by the controller to calculate the welding speed setting value so that the deviation between the bead index and its predetermined target value becomes small. And output. The welding speed setting device of the present invention can be incorporated into a new rotary arc welding device to function, and can be applied to an existing rotary arc welding device to control the bead leg length. And has great economic value.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION A rotary arc welding apparatus according to the present invention will be described below in detail with reference to the drawings based on embodiments.
FIG. 1 is a configuration diagram showing a configuration example of a high-speed rotary arc welding apparatus of the present embodiment, FIG. 2 is an explanatory diagram of a rotary torch for performing high-speed rotary arc welding, and FIG. 3 is a concept showing a periodic change of arc voltage in the present embodiment. FIG. 4, FIG. 4 is a block diagram of the control method used in the present embodiment, FIG. 5 is a drawing for explaining the relationship between the weld bead leg length and the arc length, and FIG. 6 is the arc voltage average value in the rotation phase region with respect to the gap amount. 7 is a graph showing the behavior of the difference between the arc voltage average values of two different rotational phase regions with respect to the gap amount, FIG. 8 is a graph showing the phase region for calculating the bead index, and FIG. Is a graph showing a correspondence relationship between a bead index and a welding bead, FIG. 10 is a graph showing a correspondence relationship between a bead index and an actual throat thickness, FIG. 11 is a waveform diagram explaining how to obtain a welding speed set value, and FIG. 12 is a bead index. Set value and Conceptual diagram showing settable ranges of over-back gain, graph 13 showing the test results of the fillet welding was performed by rotating arc welding apparatus of this embodiment, FIG. 1
4 is a graph showing another test result, and FIG. 15 is a graph showing a test result of welding without control of this embodiment for comparison.

As shown in FIG. 1, the rotary arc welding apparatus of the present embodiment comprises a rotary torch 1, a welding robot 2, a welding power source 3, a welding control device 4, and a computing device 5 for performing fillet welding of a work 6. It is done automatically. The welding power source 3 is
One electrode terminal is connected to the rotary torch 1, the other electrode terminal is connected to the work 6, and a welding current is supplied to the welding wire. The welding control device 4 comprehensively controls the rotary torch 1, the welding robot 2, and the welding power source 3 to perform accurate welding.

FIG. 2 conceptually shows the function of the tip portion of the rotary torch 1. A similar mechanism is disclosed in, for example, Japanese Patent Laid-Open No. 10-249523. An eccentric gear 12 is attached to the base of the electrode 11 of the rotary torch 1. The gear 12 is rotationally driven by a rotary motor 13 and rotates at a high speed at a maximum of 100 Hz. Rotary motor 1
The power of 3 can be supplied from the welding control device 4.
The welding wire 14 is applied to the lower plate 16 and the standing plate 17 at an angle that is approximately half the angle formed by the lower plate 16 and the standing plate 17, and is provided so as to rotate in a plane parallel to the welding line.

The welding wire 14 is supplied into the electrode 11 by a wire supply device (not shown), protrudes from the tip of the electrode 11 and rotates near the welding portion, and is melted by the arc 15 generated by the welding current supplied from the welding power source 3. Then, the lower plate 16
While the molten metal is placed between the vertical plate 17 and the vertical plate 17, fillet welding is performed by advancing on the joining line between the two. When the rotary torch 1 moves along the welding line, a welding bead 18 is formed at the abutting portion of the lower plate 16 and the upright plate 17, and both are welded.

When the electrode 11 is rotated to rotate the arc 15 emitted from the tip of the welding wire 14, the welding wire 1
Since the distance between the tip of No. 4 and the surface of the welding bead 18 changes periodically, the arc voltage V changes periodically according to the rotation of the welding wire 14. FIG. 3 is a diagram showing a change in arc voltage over almost one cycle. As shown by the solid line in FIG. 3, the arc voltage V during fillet welding rises when the welding wire 14 is in the front-rear direction with respect to the welding proceeding direction and decreases when it is in the left-right direction. To do.

When the welding wire 14 is rotating with the center of rotation being located in the center of the lower plate 16 and the upright plate 17, the waveform of the arc voltage V has a substantially symmetrical shape close to a sine wave.
When the center position of the welding wire 14 is biased to either the lower plate 16 or the standing plate 17, the waveform of the phase hitting the left side of the traveling direction and the waveform of the phase hitting the right side are displaced in opposite directions, as shown by the dotted line in FIG. . By utilizing this property, the welding line tracing control can be performed by performing the horizontal position control of the welding wire 14 so that the error amount from the sine waveform of the arc voltage V becomes zero.

The welding robot 2 holds the welding torch 1 at the tip of the arm, controls the position and posture of the welding torch 1 according to the instruction of the welding control device 4, and instructs the welding torch 1 along the welding line of the work 6. Move at the specified speed to weld. The welding power source 3 adjusts the welding voltage and the welding current according to the instruction of the welding control device 4 and supplies necessary electric power to the rotary torch 1. The welding current may be supplied via the wire supply device. The arc voltage applied to the welding torch 1 is measured at a position where electric power is supplied from the welding power source 3 to the welding wire 14, and the measured value every moment is digitally converted and transmitted to the arithmetic unit 5. The digital conversion of the arc voltage may be performed by the arithmetic unit 5.

FIG. 4 is a block diagram for explaining the control algorithm executed by the arithmetic unit 5. The arithmetic unit 5 is
Comprised of a small electronic calculator, the section average value calculator 2
2. A bead index calculator 24 and a welding speed controller 25 are provided, an arc voltage waveform is input from the welding controller 4, a calculation unique to the present invention is performed to calculate a bead index B, and appropriate welding is performed based on this. The speed S is obtained and the robot controller 30 of the welding control device 4 is instructed. The functions of the welding control device 4 and the arithmetic device 5 can be appropriately shared. For example, the arithmetic unit 5 inputs the bead index B to input the welding speed S
It is also possible to mount only the function for obtaining the above, and to execute the remaining part by the welding control device 4.

The welding control device 4 acquires the arc voltage value measured by the rotary torch 1 or the welding power source 3 in the welding process 20. When the welding power is applied by the wire supply device, the arc voltage may be measured by the welding wire supply device. The section average value calculator 22 inputs the arc voltage measurement value V acquired by the welding control device 4 from the welding process 20 via the input / output interface, and integrates the specified two phase regions according to the following equation (1). Then, the section average values Af and Ar are obtained, respectively. The phase region refers to a phase range in the rotation of the arc. The first designated region is an appropriate range (tc to td) in front of the welding advancing direction, and the other designated region is an appropriate range in the rear of the welding advancing direction ( ta to tb). ^{_{Ar = ∫ ta tb Vdt / (}} tb-ta) Af = ∫ tc td Vdt / (td-tc) (1)

The section average values Af and Ar are intermittently fetched by the bead index calculator 24 by the sampling device 23 which is synchronized with the robot driving timing. Bead index calculator 2
4 calculates the bead index B based on the section average value A according to the following equation (2). B = Ar−Af (2) The welding speed controller 25 includes a bead index setting device or a bead index reference value generator 26, a subtractor 27, a welding speed calculator 28, and a sampling device 29.

The bead index reference value generator 26 generates a bead index B reference value Bref which is selected and set based on a desired bead size such as bead leg length and actual throat thickness. Note that the functional relationship between the bead index reference value Bref and the bead shape has little change at least with respect to the welding speed, so it may be confirmed in advance by a simple experiment. Therefore, it is not necessary to conduct a large number of experiments to confirm the functional relationships different for each condition and to make a database as in the prior art example given as the prior art. The subtractor 27 is
An error R between the previously calculated bead index B and the bead index reference value Bref is calculated according to the following equation (3). R = Bref-B (3)

The welding speed calculator 28 uses the set coefficient Kp.
And holds the subtracter 27 based on the equation (4) below.
A new welding speed S (k + 1) is calculated and output by adding a value obtained by multiplying the error R input from the above by a coefficient Kp to the current welding speed S (k). S (k + 1) = S (k) + Kp × R (4) Here, k is a function representing the time when the calculation interval is 1, and S (k) is the welding speed setting value at the time k.
The welding speed S (k + 1) thus obtained is given to the robot controller 30 of the welding control device 4 as a target value. Welding speed is the speed at which the welding arc moves along the welding line.The slower the welding speed, the larger the weld bead grows and the larger it becomes.Therefore, if the welding speed is adjusted, the bead index can be maintained at a predetermined value. it can.

If the arc voltage is fast, 100H
Since there is one cycle of change in z, that is, 10 ms, the integral of the arc voltage measurement value is obtained, for example, every 10 ms. However, the control of the robot 2 is intermittently performed using a logic circuit such as a sequencer, for example, about every 30 ms. Therefore, it is sufficient for the calculation of the welding speed calculator 28 to be performed intermittently according to the robot control operation interval. Further, since the welding progress speed is not so high, it is not necessary to change the set value of the welding speed very rapidly. Therefore, it goes without saying that the welding speed setting value S may be given to the robot controller 30 at appropriately long intervals, not at every robot control operation interval.

The robot controller 30 controls the hand position and posture of the robot 2. In the rotary arc welding apparatus according to this embodiment, the welding speed setting value given by the welding speed controller 25 is used to set the robot speed. The rotating torch 1 held by the arm of the robot is moved at a predetermined speed. In addition to the welding speed, the welding process 20 has various input functions that affect the welding state, such as welding power, welding wire feeding speed, arc rotation speed, and welding line tracing control. Output the index. The control of the present embodiment is characterized in that the bead leg length is controlled by forming a control loop using the arc voltage as an alternative control variable and the welding speed as an operation variable from these various input / output signals.

The rotary arc welding apparatus of this embodiment will be described in more detail below, including the operating principle and the results of the execution. FIG. 5 illustrates the state of the welding bead 18 and the arc 15 when the electrode 11 rotates in order to explain the difference in arc voltage between when there is no gap and when there is a gap at the abutting portion of the lower plate 16 and the standing plate 17. It is sectional drawing cut and shown along a central axis. When there is no gap, the surface of the weld bead 18 is sufficiently high as shown by Fn, whereas when there is a gap, the molten metal flows into the gap, so the weld bead 18 is shown as Fg in the figure. The leg length becomes smaller accordingly.

The difference in the shape of the weld bead 18 when there is no gap and when there is a gap appears as a change in the arc length. A change in arc length can be detected as a change in arc voltage V. When the fillet welding is performed by rotating the electrode 11, the arc voltage V changes periodically as shown in FIG. In particular, when the rotating surface of the tip of the welding wire 14 is substantially parallel to the surface of the weld bead 18 in a molten state and proper fillet welding is being performed, the arc voltage V is lower than the lower plate side and the vertical plate side. Shows a sinusoidal waveform with valleys of almost equal depth.

If there is a gap between the lower plate 16 and the upright plate 17, the weld bead is lowered and the surface of the molten metal becomes smooth. Therefore, in the rear of the welding advancing direction, the distance from the tip of the welding wire 14 to the molten pool increases and the arc voltage rises, while in the front of the advancing direction, the arc length hardly changes and the arc voltage hardly changes. When the welding torch is subjected to vertical scanning control using the welding current as an index, when the surface of the welding bead 18 lowers, the control of bringing the tip of the welding wire closer to the lower plate surface is performed. The arc voltage drops in the front phase.

Therefore, in order to confirm the relationship between the gap amount and the arc voltage, two plates having a plate thickness of 12 mm were butted and the gap was gradually changed from 0 mm to 4 mm, which was MAG welded by a high-speed rotating arc. When the arc voltage for each rotation phase of the rotating arc was observed, the results shown in FIG. 6 could be obtained. Note that this test was performed using vertical scanning control.

In FIG. 6, the horizontal axis represents the gap amount, and the vertical axis represents the value obtained by integrating and averaging arc voltage values in a typical rotation phase in an appropriate interval, and plotting the values on an arbitrary scale. The rotation phases shown in the figure are P1, P shown in FIG.
It is a position corresponding to the points of 2 and P3. P1 is a position at which the welding wire is advanced by about 45 degrees from the side right in the welding direction and is expected to well reflect the relationship between the tip of the welding wire and the lower plate. P2 is a position substantially perpendicular to the traveling direction. Further, P3 corresponds to a position almost right behind the traveling direction.

The average value of the arc voltage does not change up to approximately 2.5 mm for any phase. However, in a gap larger than that, the arc voltage average value in the region sandwiching P1 increases as the gap increases, and the arc voltage average value in the region sandwiching P3 decreases. Further, the arc voltage in the region sandwiching P2 has no remarkable tendency. Examining the reproducibility of these changes, for P1 and P3,
It was found that there is sufficient reproducibility, but P2 has poor reproducibility.

Therefore, paying attention to these arc voltage tendencies, the difference between the average arc voltage obtained around P1 and the average arc voltage obtained around P3 was calculated, and the relationship with the gap amount was plotted. 8 is a graph of FIG. 7. In FIG. 7, the horizontal axis represents the gap amount and the vertical axis represents the difference between the average values. From the graph, it can be seen that the gap amount and the monovalent function correspond well in the region where the gap amount is 2.5 mm or more. Here, this average value difference is called a bead index.

In order to use the bead index for online control, it is required that the bead index can be calculated by an easy-to-calculate method.
Therefore, as shown in FIG. 8, for example, based on the time associated with the rotation phase of the welding wire, an appropriate first calculation region (tc to t) while the welding wire is in the forward direction of the welding direction.
d) and an appropriate second calculation area (ta to tb) between the areas behind the welding direction are defined, arc voltage values Af and Ar over these areas are integrated and averaged, and the difference between the average values is taken. Bead index B.

Here, in order to make the index better correspond to the state of the bead, the first calculation region is a region from the point where the rotational phase is directly lateral to the traveling direction to the point where the rotational phase is directed straight ahead, It is preferable that the calculation region of is set at 45 ° with a direction directly behind the traveling direction sandwiched therebetween. In addition,
The reason why the widths of the phase angles in the first and second regions are the same 90 ° is that both have the same integration time and the procedure is shared to simplify the calculation. It goes without saying that the area may be designated.

In order to verify the correspondence between the bead index and the weld bead, fillet welding was performed with a high-speed rotating arc in a state in which the vertical plate was aligned so that there was no gap with respect to the lower plate, and the relationship between the bead index and the bead shape. The results of observation are shown in FIG.
In FIG. 9, the welding speed is taken as a parameter on the horizontal axis, and the bead index, the bead leg length, and the actual throat thickness are taken on the vertical axis. 100 cm / min with welding speed as a parameter
In the test conducted while decelerating from 10 cm / min to 10 cm / min, the bead index, actual throat thickness, and leg length do not change much while the welding speed is reduced to about 50 cm / min, but at lower speeds, the bead index decreases. It is observed that both the actual throat thickness and the leg length increase as a result. Welding speed from 10 cm / min to 100 cm / mi
The same tendency was observed when these states were observed while gradually increasing the speed to n. In this test, it was demonstrated that the correlation coefficient between the bead index and the actual throat thickness is -0.82, and the correlation coefficient between the bead index and the leg length is -0.59.

FIG. 10 is a graph showing the relationship between the bead index and the actual throat thickness. In the figure, the horizontal axis represents the actual throat thickness, and the vertical axis plots the bead index. The bead index is an average value around the time when each actual throat thickness is taken in the test for determining FIG.
Observing this relationship, the bead index decreases monotonically as the actual throat thickness increases, and it can be seen that there is a strong correspondence between the two. In addition, the reason why the gradient of the graph changes in the vicinity of the actual throat thickness of 3.7 mm is probably that the welding phenomenon changes somewhere around this. From the above, it can be seen that the bead index can be used as an alternative variable for the actual throat thickness or leg length.

The rotary arc welding apparatus of this embodiment calculates the bead index B which is an alternative variable of the bead leg length, obtains the deviation from the bead index set value Bref, and multiplies this by the appropriate feedback coefficient Kp to perform welding. Calculate the speed setting value S,
The bead leg length is controlled to a desired value by adjusting the welding electrode feed speed of the welding robot based on this.

FIG. 11 illustrates how to obtain the welding speed set value S in this embodiment. FIG. 11 shows
The horizontal axis shows time and the scale shows sample time.
The vertical axis shows the bead index and the welding speed. The scale of the bead index is given in arbitrary units. Also, although a numerical value is given for the welding speed,
The appropriate range depends on the conditions and is for reference only.

Since the bead index B is obtained for each arc rotation, it is almost continuously given to the control system every 10 ms, for example. On the other hand, the formation of weld beads is a much slower event compared to this, so it is sufficient to adjust the welding speed at appropriate intervals. Therefore, an appropriate sampling cycle is set, the current set value is corrected based on the bead index value at the current sampling timing, and a new welding speed set value is calculated. The sampling interval is determined in consideration of the capability specification of the arithmetic device and the reduction of the calculation load.

For example, the 50th welding speed set value S
When calculating (50), the bead index B (49) at the time of sampling is obtained, and the current speed set value S (49) is calculated by multiplying the deviation from the bead index set value Bref by the proportional coefficient Kp which is a feedback gain. ) Is corrected. If the bead index is large, the welding speed must be set low.

The bead index set value Bref is determined by the size of the target welding bead, but the control performance depends on the value of the feedback gain Kp, so if a bead having an appropriate shape is to be obtained, further control is performed. It is necessary to determine the gain Kp suitable for the bead index set value Bref. Figure 1
In FIG. 2, the horizontal axis represents the bead index setting value Bref and the vertical axis represents the feedback gain Kp, which conceptually represents an appropriate settable range as a relationship between the two.

If the bead index set value Bref is small, the welding bead is large. However, the bead index setting value Bref
If the value is too small, the welding bead becomes too large and the shape collapses. If the bead index setting value Bref is too large, the welding bead becomes too small and welding cannot be performed. Further, if the feedback gain Kp is large, the response speed of the welding speed change increases, but in the excessive response state, abnormal welding occurs such that the width of the bead changes periodically, and if the response speed is too small, disturbance occurs. Sometimes this cannot be eliminated. The upper limit of the welding speed may be set to a reference speed that can generate an appropriate welding bead when there is no gap. As described above, although there is an appropriate setting range for all the parameters, the feedback gain Kp is determined to have an appropriate range corresponding to the bead index setting value Bref.

Therefore, when the leg length is changed, the bead index set value Bref may be changed appropriately, but when the changed value is large, it is preferable to further set the feedback gain Kp to the optimum value. In the rotary arc welding apparatus of the present embodiment, it is sufficient to set these two parameters in order to adjust the bead leg length and the actual throat thickness to predetermined values, so the adjustment is extremely simple compared with the conventional apparatus. As a result, the required level of performance of the apparatus is lowered and the operator's setting work is simplified.

In the rotary arc welding apparatus of this embodiment, the response speed is adjusted by a proportional constant that multiplies the error amount, but if it substantially acts as a feedback gain, the same effect can be obtained. It goes without saying that the integral coefficient may be used or the coefficient may be set in the robot controller. Needless to say, instead of directly setting the feedback gain Kp, the value of a parameter that substantially affects the feedback gain Kp may be set. Further, although the arithmetic device is configured by using a small electronic calculator, it may be another device having a calculation function. Further, although the arithmetic operation in the control system which the arithmetic device is supposed to perform is specified, the other elements such as the robot controller also have a calculation function, and therefore the arithmetic operation may be distributed to other elements and executed. Needless to say.

FIG. 13 exemplifies the result of trial fillet welding performed by the rotary arc welding apparatus of this embodiment. The horizontal axis represents the welding movement amount on an arbitrary scale, and the vertical axis represents the welding speed, the gap amount, the leg length, and the actual throat thickness.
The test uses a work piece formed by diagonally increasing the gap from 0 mm to 4 mm by standing the standing plate on the lower plate, and adjusting the welding speed so as to maintain the bead index constant. It was welded along.

Welding was performed in the direction in which there was no gap and in the direction of expansion, the welding speed was monitored during welding, and after the welding was completed, the actual throat thickness, lower plate side leg length, and vertical plate side leg length were measured. Was plotted. Gap amount is 2.5mm
It can be seen that the welding speed is rapidly decreasing from around the point above. As a result, both the actual throat thickness and the leg length are formed substantially constant regardless of the gap amount, and good fillet welding is performed.

FIG. 14 is a drawing showing another test example of fillet welding by the rotary arc welding apparatus of this embodiment. In this test, the vertical plate with a gentle wedge-shaped slope that becomes deepest in the center on the side surface is applied to the lower plate, and the gap amount increases from 0 mm to 4.5 mm along the welding line and then again to 0 mm. The work is made to be reduced, and the fillet welding is performed by the rotary arc welding device of the present embodiment.

The welding speed is decreased as the gap becomes larger, and then the welding speed is increased as the gap becomes smaller. As a result, the lower plate side leg length, the standing plate side leg length, and the actual throat thickness are all controlled within an extremely narrow range. In the previous test, the control performance up to about 4 mm was confirmed, but it is clear from this test that even larger ones can be welded with good quality fillets depending on the state of the gap.

For comparison, FIG. 15 shows the result of welding by the conventional method without the control of this embodiment. Here, welding was performed while maintaining a constant welding speed regardless of the gap amount. As a result, the lower plate-side leg length, the standing plate-side leg length, and the actual throat thickness decrease as the gap amount increases, and increase as the gap amount decreases. For a gap of 4 mm, changes in actual throat thickness of 3 mm to 4 mm and leg lengths of 3 mm to 5 mm are observed. As described above, the effect of the rotary arc welding apparatus of the present embodiment is remarkable, and it was proved that the bead shape can be controlled to be constant even if there is some gap.

[0064]

As described above, by using the rotary arc welding apparatus of the present invention, it is possible to prevent the bead leg length from being insufficient even if there is an excessive gap in the welded portion of the work, and the size of the weld bead is large. Even when changing, the high-speed rotary arc welding can be automatically performed by setting relatively few adjustment parameters.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration example of a high-speed rotary arc welding device of the present invention.

FIG. 2 is an explanatory diagram of a rotary torch that performs high-speed rotary arc welding in this embodiment.

FIG. 3 is a conceptual diagram showing a periodic change in arc voltage in the present embodiment.

FIG. 4 is a block diagram illustrating a control algorithm executed by the arithmetic unit according to the present embodiment.

FIG. 5 is a cross-sectional view illustrating the relationship between the welding bead and the arc length in this embodiment.

FIG. 6 is a graph showing a behavior of an arc voltage average value in a rotation phase region with respect to a gap amount in the present embodiment.

FIG. 7 shows the difference of 2 with respect to the gap amount in this embodiment.
It is a graph which shows the behavior of the difference of the arc voltage average value of each rotation phase area.

FIG. 8 is a graph showing a phase region for calculating a bead index in this example.

FIG. 9 is a graph showing a correspondence relationship between a bead index and a weld bead in this example.

FIG. 10 is a graph showing a correspondence relationship between a bead index and an actual throat thickness in this example.

FIG. 11 is a waveform diagram illustrating how to obtain a welding speed set value in the present embodiment.

FIG. 12 is a conceptual diagram showing a settable range of a bead index set value and a feedback gain in the present embodiment.

FIG. 13 is a graph showing the test results of fillet welding performed by the rotary arc welding apparatus of this example.

FIG. 14 is a graph showing another test result of fillet welding performed by the rotary arc welding apparatus of the present embodiment.

FIG. 15 is a graph showing test results of fillet welding performed by a conventional rotary arc welding device.

[Explanation of symbols]

1 rotary torch 2 Welding robot 3 welding power source 4 Welding control device 5 arithmetic unit 6 work 11 electrodes 12 Eccentric gear 13 rotation motor 14 Welding wire 16 Lower plate 17 Stands 15 arc 18 weld beads 22 Section average value calculator 24 bead index calculator 25 Welding speed controller 30 robot controller 20 Welding process 23 Sampling device 26 Bead Index Reference Value Generator 27 Subtractor 28 Welding speed calculator 29 Sampling device

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-80971 (JP, A) JP-A-60-210357 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 9/127 B23K 9/095

Claims (5)

(57) [Claims] 1. A rotary arc welding apparatus comprising an arc voltage measuring device, a computing device, a control device, and a welding speed adjusting device, wherein the arc voltage measuring device obtains an arc voltage value during arc rotation, and the computing device. Is the input of the arc voltage value to obtain the average value of the arc voltage in different phase regions of the arc rotation to obtain the bead index given as the difference between the average values, and the controller uses the feedback gain set. The welding speed adjusting device is controlled so that the deviation between the bead index and its predetermined target value becomes small, and the welding speed adjusting device adjusts the welding speed according to the control device, thereby controlling the welding bead leg length to be constant. One of the different phase regions during the arc rotation
Is the lower plate part of the welded member with the arc in front of the welding direction
Is the phase region that is hitting the
Specified position across the position where the ark strikes directly behind the welding direction.
A rotary arc welding device characterized by a phase region between angles . Wherein the control device is rotating arc welding apparatus according to claim 1, characterized in that the setting of the welding speed for each appropriate time interval. Wherein the control device is rotating arc welding apparatus according to claim 1 or 2, wherein the determining the weld bead leg length by adjusting the target value of the bead indices. 4. The rotary arc welding according to claim 3, wherein the control device inputs a feedback gain selected corresponding to the bead index and improves the control performance by using the feedback gain. apparatus. 5. A welding speed setting device for a rotary arc welding device, comprising an arithmetic unit and a control unit, wherein the arithmetic unit inputs an arc voltage value during arc rotation and arcs in different phase regions of arc rotation. The average value of the voltage values is obtained to obtain the bead index given as the difference between the average values, and the control device uses the recorded feedback gain so that the deviation between the bead index and its predetermined target value becomes small. A welding speed setting device characterized by calculating and outputting a set value of welding speed.