JPS60148677A - Method and device for automatic welding - Google Patents

Abstract

PURPOSE:To obtain a titled device for shifting a torch without being influenced by a state of a weld zone, by detecting a constant period of a torch oscillation, and the same frequency component of a current or its higher harmonic component, and moving the torch oscillating center in the direction where the current frequency component becomes small. CONSTITUTION:A current detecting 52 signal 54 and an oscillation quantity detecting 58 signal 62 are multiplied by a multiplier 70 of a control device 56. This value 80 and a signal 64 of an oscillating position detector 60 are integrated by an integrator 72 and the same frequency component (current value) Z82 as the oscillation is calculated. An oscillating center position correcting value by which the Z value becomes ''0'' is derived from a storage device 74 by a discrimination of the same phase or the opposite phase of the Z value 82 and an oscillating center value 64, and the oscillating center position is corrected by driving a motor 28a from a driving signal output part 76. A torch is shifted correctly without being influenced by a state of a weld zone such as a drop of a droplet, a wire bend, a feed variation, an ununiform melting way, whether a tack welding part exists or not, etc.

Description

[Detailed description of the invention] (b) Technical field The present invention relates to an automatic welding method and apparatus.

(b) Prior art When welding is performed by automatically moving a welding torch along the shape of the welded part, a method that uses mechanical contact or a visual device such as a television camera is used to detect the welded part. Methods that utilize changes in physical phenomena such as voltage, current, sound, and magnetism during welding are used. Among methods that utilize changes in physical phenomena, methods that utilize changes in voltage or current during welding have the advantage that there is no need to install special equipment around the welding torch. FIG. 1 shows a welding torch and a welded area when detecting a welded area using changes in welding current. The contact surface ends of the objects to be welded 10 and 12 are the welding portion 14 to be arc welded. welding torch 16
is arranged above the welding part 14 and moves in a direction perpendicular to the plane of the paper to weld the welding part 14. At this time, the welding torch 16 is swung in a plane perpendicular to the direction of movement of the welding torch 16 (a plane parallel to the plane of the paper). The welding current during welding is measured, and the welding torch 16 is moved in the X direction or Y direction so that the current values at swing end points A and B are always equal. By doing this, welding torch 1
The swing center position C of No. 6 is held at a position directly above the welding portion 14. In this method, the objects to be welded 10 and 12 are
It is based on the idea that since the welding torch 16 is geometrically symmetrical with respect to the vertical plane passing through it, if the swing center position C of the welding torch 16 is within the vertical plane, the welding currents at the swing end points A and B should be equal. ing.

However, with the conventional methods as described above, it is difficult to reliably detect a welded part under all welding conditions and automatically perform welding with high precision in accordance with the detected welded part. This is because arc welding utilizes an unstable discharge phenomenon, and various conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence of tack joints change during welding. In reality, the welding current changes in a very complex manner, as shown in FIG. 2, for example, and the relationship between the difference in welding current at the end point of the swing and the deviation of the welding torch 16 from the welding part 14 is always clear. That's because it's not. Therefore, under welding conditions where the relationship between the change in welding current and the deviation of the welding torch 16 is relatively clear, such as the so-called downward welding method in which the welding torch 16 is directed directly upward as shown in FIG. Although automatic welding can be performed by conventional methods such as
It was difficult to reliably move the material along the welded portion 14.

(C) Purpose of the Invention The present invention is capable of reliably detecting a welded part without being affected by changes in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence or absence of tacked parts. The object of the present invention is to provide an automatic welding method and device that can automatically perform welding using the following methods.

(D) Structure of the Invention The present invention provides a method for detecting positional deviation between a welding torch and a welded part based on a change in a predetermined frequency component (predetermined frequency spectrum) of a welding current when the welding torch is oscillated at a predetermined frequency. The above purpose is achieved by detecting. That is, the automatic welding method according to the present invention involves moving the welding torch at a constant period in a plane perpendicular to the direction of movement of the welding torch, and using the same frequency component as the oscillation period of the welding torch among the frequency components of the welding current. Alternatively, the present invention is characterized by detecting the harmonic component thereof, and moving the swing center position of the welding torch in a direction in which the detected frequency component becomes smaller. Further, the automatic welding apparatus according to the present invention includes a welding torch, a swinging device for swinging the welding torch, a lateral movement device capable of moving the 1-meter swinging device in the swinging direction of the welding torch, and a swinging device for swinging the welding torch. a vertical movement device movable in a direction perpendicular to the swing plane of the welding torch, a wire feeding device that feeds the wire to the welding torch, a welding power source that supplies current to the wire, and a current that detects the current of the welding power source. a detector, a swing position detector that outputs a signal when the welding torch is at a predetermined swing position, and a swing amount detector that detects the swing amount from the swing center of the welding torch as an analog signal. and a control device that outputs a command signal to the lateral movement device based on input signals from the current detector, the swing position detector, and the swing amount detector. A multiplier that multiplies the signal from the oscillation amount detector by the signal from the oscillation amount detector, and a multiplier that integrates the signal from the multiplier and calculates the integral value to O for each oscillation period using the signal from the oscillation position detector. a memory for storing an output signal from the integrator immediately before the integrator is liquidated; and a lateral movement device for reducing the output signal from the integrator based on the signal from the memory. and a drive signal output section that outputs a drive signal for actuation.

The reason why the positional deviation of the welding torch can be detected with the above configuration is based on the following principle. That is, among the frequency components of the welding current, the magnitude of the frequency component that is the same as the oscillation frequency of the welding torch changes depending on the magnitude of the displacement of the welding torch from the welding part. On the other hand, the influence of changes in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence or absence of temporary attachment parts is due to the effects of changes in conditions such as falling droplets, bending of the wire, and the presence or absence of temporary attachment parts. It has almost no effect on the magnitude of the frequency component that is the same as the oscillation frequency. Therefore, by detecting only the same frequency component as the oscillation frequency of the welding torch or its harmonic component, and moving the welding latch so that the magnitude of the frequency component becomes smaller, the fluctuation of the welding conditions as described above can be detected. The position of the welding torch can be matched to the welding part without being affected. In addition,
The moving direction of the welding torch is determined using the forward and reverse phases of the frequency components with respect to the swinging of the welding torch.

(e) Examples Examples of the present invention will now be described with reference to FIGS. 3 to 7 of the accompanying drawings.

FIG. 3 shows an automatic welding device according to the present invention. This is an example in which the present invention is applied to downward fillet welding. Welding torch 20 is swingably supported by swing device 22 . The swinging device 22 can swing the welding torch 20 at regular intervals.

A wire 26 is supplied to the welding torch 20 from a wire feeding device 24.
can be sent. The rocking device 22 is a lateral movement device 28
are connected to each other via a support member 30. The lateral movement device 28 has a motor 28a, and the motor 28a
By operating the support member 30, the support member 30 can be moved in the horizontal direction in FIG. That is, motor 28
By driving a, the swinging device 22 and the welding torch 20 supported by the swinging device 22 can be moved in the horizontal direction. The lateral movement device 28 has a bearing 3 on the frame 32.
It is provided on a carriage 38 which is supported so as to be movable in the horizontal direction (direction perpendicular to the plane of the paper) via 4 and 36.

Note that a drive device that drives the traveling platform 38 is not shown. This carriage 38 and the drive device constitute a longitudinal movement device.

By moving the carriage 38, the welding torch 20 can be moved in a direction perpendicular to the plane of the paper. The objects to be welded 40 and 42 are placed on a table 44 . Object to be welded 40
and 42 are the welding portions 46 to be welded.

The wire feeding device 24 and the stand 44 are connected to a welding power source 50 by power supply lines 47 and 48, respectively. The welding power source 50 is provided with a current detector 52, and a signal 54 from the current detector 52 is input to a control device 56. The current detector 52 is, for example, a magnetic current detector using a Hall element or a shunt resistor, and generates a signal 54 proportional to the welding current. Signals 62 and 64 from a swing amount detector 58 and a swing position detector 60 provided in the swing device 22 are also input to the control device 56 . Oscillation amount detector 58
Detects an analog signal corresponding to the swinging position of the welding torch 20 during swinging, and is constituted by, for example, a potentiometer. When the swing device 22 swings the welding torch 20 in a sinusoidal manner, the signal 62 from the swing amount detector 58 becomes an analog electrical signal that changes in a sinusoidal manner. Further, the swing position detector 60 generates a pulse-like signal 64 when the welding torch 20 passes the swing center position from one direction (that is, once per swing cycle). For example, it can be configured by a slit mechanism and a photoelectric switch that work together with the welding torch 20. The control device 56 can output a signal 66 that commands the amount and direction of rotation to the motor 28a. The configuration of the control device 56 is shown in a block diagram in FIG. The control device 56 receives a signal 54 from the current detector 52, a signal 62 from the swing amount detector 58, and a signal 64 from the swing position detector 60.
is input, and a signal 66 is output to the motor 28a. The control device 56 includes a multiplier 70, an integrator 72, a memory 74, and a drive signal output section 76. Multiplier 70 generates a signal 80 that is proportional to the product of signal 54 from current detector 52 and signal 62 from swing amount detector 58. The integrator 72 has the function of integrating the signal 80 from the multiplier 7° and settling the integrated value to O every swing cycle using the signal 64 from the swing position detector 60. Memory device 74
has the function of storing the value immediately before the signal 82 from the integrator 72 is cleared. The drive signal output unit 76 outputs a signal 66 that drives the motor 28a at a rotational speed proportional to the signal 84 from the memory 74 for a certain period of time immediately after the signal 64 is input.

Next, the operation of this embodiment will be explained. Welding is performed using the apparatus shown in FIGS. 3 and 4 in the following manner. The welding torch 20 is oscillated in a plane parallel to the plane of the paper by the swing device 22 and moved by the traveling base 38 in a direction perpendicular to the plane of the paper, thereby arc-welding the welding portion 46. The control device 5 controls the welding torch 20 so that it passes directly above the welding part 46.
The motor 28a is rotated by the signal 66 from the welding torch 20, and the welding torch 20 is moved in the horizontal direction. The control device 56 receives a signal 62 from the swing amount detector 58, a signal 64 from the swing position detector 60, and the like. Based on the signal 54 from the current detector 52, the signal 66 to be output to the motor 28a is determined as follows. That is, first, the signal 5 from the current detector 52
4 and a sine wave signal 62 from the swing amount detector 58 in a multiplier 70. Signal 8 multiplied by multiplier 70
0 is integrated in the integrator 72, and the integrated value is settled to 0 each time the signal 64 from the swing position detector 60 is input to the integrator 72. The integrator 72 outputs the integral value immediately before being cleared to 0 as a signal 82. Therefore,
Of the frequency components included in the signal 54 from the current detector 52, only the sine wave frequency component (that is, the frequency component that matches the oscillation period of the welding torch 20) is extracted as the signal 82. That is, the magnitude of the output value of the signal 82 is approximately proportional to the magnitude of the frequency component of the oscillation frequency of the welding torch 20, and the positive or negative of the output value of the signal 82 is equal to the positive or negative phase of the frequency component with respect to the oscillation. We are doing so. That is, among the many frequency components contained in the welding current, the welding torch 20
The same frequency component as the oscillation period and the positive and negative phases are detected. This relationship is shown in FIGS. 5 to 7 using drawings. That is, as shown in FIG. 5, the horizontal positional deviation of the welding torch 20 from the welding part 46 is defined as X, and among the frequency components of the welding current, the frequency component that is the same as the oscillation frequency of the welding torch 20 is If the size is 2,
The relationship between X and 2 is as shown in FIG. That is,
As the absolute value of X increases, the value of 2 also increases. Also,
As shown in FIG. 7, the phase is reversed depending on the direction of displacement of the welding torch 20 (that is, whether the value of X is positive or negative). This allows the direction of displacement of the welding torch 20 to be detected. The signal 82 obtained by the integrator 72 is stored in the memory 74, and the signal 84 from the memory 74 is input to the drive signal output section 76.

The drive signal output section 76 outputs a signal 66 that drives the motor 28a for a certain period of time immediately after the signal 64 is input at a rotation speed proportional to the signal 84 from the memory 74.

Therefore, the motor 28a is driven by a predetermined amount according to the signal 84 from the memory 74 every swing period of the welding torch 20.

In other words, the welding torch 2
The horizontal position of 0 will be adjusted. The amount of movement of welding torch 20 is proportional to the magnitude of signal 84.

The welding torch 2 is controlled by the action of the control device 56 as described above.
0 is controlled so that it is always located directly above the welding part 46. For example, if the position of the welding torch 20 is shifted from directly above the welding part 46, the frequency aIt included in the welding current
Since the frequency component of the G component that is the same as the oscillation period of the welding torch 20 becomes large (see FIG. 6), the signal 82 stored in the memory 74 becomes large. The drive signal output section 76 rotates the motor 28a in a direction that reduces this signal 82. The rotational direction of the motor 28a is determined depending on whether the signal 82 is positive or negative, and the welding torch 20 is moved to a position directly above the welding part 46. When the welding torch 20 is located directly above the welding part 46, among the frequency components included in the welding current, the frequency component that is the same as the oscillation period of the welding torch 20 is extremely small, so it is stored in the memory 74. The stored signal 82 also becomes approximately O, and the motor 28a hardly rotates and the welding torch 20 does not move. As described above, welding torch 2
The position of the welding torch 20 is controlled so that it is directly above the welding part 46 every cycle of the oscillation, and the welding torch 20 is always positioned directly above the welding part 46 during welding.
Welding is performed by moving the carriage 38. During welding, fluctuations occur in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, uneven melting of the wire, and the presence or absence of temporary attachment parts, but the frequency components of these fluctuations is different from the frequency component of the oscillation frequency of the welding torch 20, and has almost no effect on the frequency component that is the same as the oscillation frequency of the welding torch. Therefore, despite the above-mentioned fluctuations in welding conditions, the welding torch 20
is securely held directly above the weld 46.

In addition, in the above embodiment, the frequency component that is the same as the oscillation period of the welding torch is detected, but the frequency component that is twice this frequency,
The same action and effect can be obtained by detecting a quadrupled harmonic component.

(f) As described in detail, the method of the present invention involves swinging the welding torch at a constant period in a plane orthogonal to the direction of movement of the welding torch, and By detecting the same frequency component as the motion period or its harmonic component, and moving the center position of the welding torch in the direction where the detected frequency component becomes smaller, we are able to prevent droplets from falling during welding and the wire from falling during welding. bending, fluctuations in wire feeding speed,
The welding torch can be moved along the welding area without being affected by the unevenness of the wire melting direction, the presence or absence of temporary attachment parts, etc., and the welding torch can be moved as desired without being limited to downward fillet welding. Arc welding can be performed. Further, an automatic welding device that implements the above method includes a welding torch, a rocking device that rocks the welding torch, a lateral movement device that can move the rocking device in the rocking direction of the welding torch, and a rocking device. a vertical moving device that can move in a direction perpendicular to the swinging plane of the welding torch, a wire feeding device that feeds the wire to the welding torch, a welding power source that supplies current to the wire, and a welding power source that controls the current of the welding power source. a current detector that detects the current; a swing position detector that outputs a signal when the welding torch is at a predetermined swing position;
A swing amount detector detects the amount of swing from the center of the welding torch's swing as an analog signal, and commands are given to the lateral movement device based on input signals from the current detector, swing position detector, and swing amount detector. The control device includes a multiplier that multiplies the signal from the current detector and the signal from the swing amount detector, and a multiplier that integrates the signal from the multiplier and outputs the swing amount detector. An integrator that settles the integral value to 0 for each swing period by the signal from the moving position detector, a memory that stores the output signal from the integrator immediately before the integrator is cleared, and a memory that stores the output signal from the integrator immediately before the integrator is cleared. a drive signal output section that outputs a drive signal that operates the lateral movement device in a direction that reduces the output signal from the integrator based on the signal, and a drive signal output section that outputs a drive signal that operates the lateral movement device in a direction that reduces the output signal from the integrator. Arc welding can be performed along the line.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a welding torch and a welding part in a conventional welding method, Fig. 2 is a diagram showing changes in welding current with respect to the swing position, and Fig. 3 is a diagram showing an automatic welding device according to the present invention. Fig. 4 is a block diagram showing the control device of the automatic welding equipment shown in Fig. 3, Fig. 5 is a diagram showing the welding torch in a misaligned state, and Fig. 6 is a diagram showing the relationship between the amount of misalignment and the frequency component current value. Diagram showing the relationship. FIG. 7 is a diagram showing the relationship between positional deviation and phase. 20... Welding torch, 22... Rocking device, 24...
e-wire feeding device, 26...wire, 28...lateral movement device, 28a...motor, 30...-support material, 32...frame, 34.36...bearing, 38・
...Traveling stand, 40, 42...O welded member, 44...
Stand, 46... Welding part, 47.48... Power supply line, 50
...Welding power source, 52φ...Current detector, 54, 62.
64.66...signal, 56...control device, 58...
Medium swing amount detector, 60/φ/swing position detector, 70...
- Multiplier, 72... Integrator, 74... Memory device, 76
... Drive signal output section, 80, 82, 84... Signal. Patent Applicant Nikki Steel Co., Ltd. Agent Patent Attorney Toshiyuki Miyauchi Figure 5 =: Figure 8 Zeng Figure 7 Q2-

Claims (1)

[Claims] 1. In an automatic welding method in which arc welding is performed by automatically moving a welding torch along a welding part, the welding torch is oscillated at a constant cycle in a plane orthogonal to the direction of movement of the welding torch. Detecting a frequency component of the welding current that is the same as the oscillation period of the welding torch or its harmonic component, Shifting the oscillation center position of the welding torch in a direction where the detected frequency component becomes smaller. An automatic welding method characterized by: 2. A welding torch, a rocking device that rocks the welding torch, a lateral movement device that can move the rocking device in the rocking direction of the welding torch, and a rocking device that is perpendicular to the rocking plane of the welding torch. a wire feeding device that feeds the wire to the welding torch; a welding power source that supplies current to the wire; a current detector that detects the current of the welding power source; A swing position detector that outputs a signal when the welding torch is at a predetermined swing position, a swing amount detector that detects the swing amount from the swing center of the welding torch, a current detector, a swing position detector, and The control device outputs a command signal to the lateral movement device based on the input signal from the swing amount detector, and the control device outputs a command signal from the current detector and the swing amount detector. a multiplier that multiplies the signal, an integrator that integrates the signal from the multiplier and settles the integrated value into O for each swing period by the signal from the swing position detector, and a a memory device that stores an output signal from the integrator; a drive signal output unit that outputs a drive signal that operates the lateral movement device in a direction that reduces the output signal from the integrator based on the signal from the memory device; Automatic welding equipment with.