JPH08257751A - Automatic welding torch controller - Google Patents

Abstract

PURPOSE: To provide an automatic welding torch controller capable of high precision welding. CONSTITUTION: A voltage amplifying circuit 2 is connected to a voltage detecting terminal 1 and a fluctuation detecting range automatic set circuit 3 is connected to the voltage amplifying circuit 2. Further, an effective value transforming circuit 4 is connected to the fluctuation detecting range set circuit 3, also, a reference value storage circuit 5 is connected to the effective value transforming circuit 4. Further, a difference comparing circuit 6 is connected to both effective value transforming circuit 4 and reference value memory circuit 5. Further, a torch up/down drive circuit 7 is connected to the difference comparing circuit 6, also, a system control circuit 8 is connected to the reference value storage circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention moves a mechanical section based on a signal generated by processing a welding current value or a voltage value,
The present invention relates to an automatic welding torch control device that automatically controls the height of a welding torch according to the height of a welding line.

[0002]

2. Description of the Related Art Generally, in arc welding, in order to maintain a stable melt transfer of the welding core wire to the base metal and to improve the metallurgical and mechanical properties of the welded portion, the entire welding period is required. It is necessary to keep the arc length constant. Therefore, conventionally, in arc welding, a method has been used in which the welding current and welding voltage are measured and the height of the welding torch is controlled based on the measured values to keep the arc length constant.

Here, in arc welding using a consumable electrode wire, since the torch height changes due to the use of a power source having a constant voltage characteristic, the welding current changes greatly, so a current change is detected. Also, the output characteristics of the power supply are 2-3 V / 1
Since it has a gradient of about 00 A, a method of detecting a change in arc voltage is also used. On the other hand, in arc welding performed using a non-consumable electrode, since a power source having a drooping characteristic is used, a method of detecting a change in arc voltage is used.

Control objects using such a method for detecting changes in arc current and arc voltage include welding line tracing, torch height, welding amount and back bead formation. Further, as the control method, means such as lift, average value, reference value comparison, reference value comparison of the number of arc short circuits, etc. are used. further,
The control principle includes integration value, frequency component value, pattern matching, reference value comparison and the like. The sensor that detects changes in the arc current and arc voltage is generally called an arc sensor.

In general, a method of changing the arc length by directly controlling the welding current value and the voltage value with respect to the change in the height of the welding line by using the signal from such an arc sensor is used. There is. Further, a method is used in which a holding portion of a welding torch is slidably driven by using a signal from an arc sensor to follow a change in height of a welding line.

[0006]

However, the welding apparatus using the conventional arc sensor as described above has the following problems. That is, when detecting a change in current or voltage, in actual welding, the change in current or voltage due to weaving or applying a pulse current is large, so a slight current or It is very difficult to identify changes in voltage.

Further, in automatic welding using a consumable electrode, a power source having a constant current characteristic is used, and CO ₂ welding or MAG using a steel-based welding wire in which the electrode repeats a short circuit to the base metal during welding.
In welding, it is possible to detect a change in current when a short circuit occurs. However, in MIG welding using an aluminum wire, a splay transition does not occur and an arc short circuit does not occur, so that the current and voltage change little, and therefore the arc sensor cannot be used.

Further, in AC arc welding, the arc voltage waveform differs depending on the polarity, and in the inverter type welding machine, the time ratio between the positive electrode and the reverse electrode is arbitrary in order to make the cleaning action effective for welding aluminum. Since it can be set to, it is difficult to take the reference value and the sampling timing.

Further, some welding machines do not have a reference value circuit. In such a welding machine, a change in excess or deficiency of current or voltage is calculated based on which value, and how much is corrected. It's not easy to decide if you need. On the other hand, even a welder with a built-in reference value comparison circuit and correction circuit is useful for stabilizing current and voltage, but if it reacts hypersensitively to changes in the height of the weld, the arc will stabilize. Without good quality welding is not possible. In addition, there is a limit to the height of the welded material that can cope with changes, and the desired welding may not be possible.

The present invention has been proposed in order to solve the above-mentioned problems of the prior art, and the purpose thereof is to set and change the reference current and voltage as desired. It is an object of the present invention to provide an automatic welding torch control device that can be attached to an arc welding machine and smoothly responds to changes in the height of the welding line and enables highly accurate welding.

[0011]

According to a first aspect of the present invention, a current or voltage during arc welding is compared with a reference value, and a servomotor for driving a welding torch up and down is controlled based on the difference. In the automatic welding torch control device, a voltage detection terminal for detecting the welding current or welding voltage, a voltage amplification circuit that expands a minute voltage waveform, and a part of the voltage waveform that is expanded as a reference value or fluctuations and taken out. , A fluctuation detection range automatic setting circuit for setting the sampling level, and an effective value conversion circuit for converting the fluctuation into an effective value,
The value of the fluctuation at the start of welding is stored as a reference value, and this reference value is made variable when necessary, and the reference value storage circuit that stores a new reference value each time is compared with the reference value and the read value. A difference comparison circuit that outputs the difference as an error signal, a torch vertical drive circuit that moves the welding torch up and down so as to eliminate the difference between the variation and the reference value based on the drive signal of the servo motor, and a reference value. And a system control circuit that generates a timing signal for sampling of fluctuations.

According to a second aspect of the invention, in the automatic welding torch control device according to the first aspect, when the voltage detection terminal detects a welding current, a voltage is provided by providing a contact at the ammeter terminal of the welding machine. The present invention is characterized in that it is configured to detect a drop, and in the case of detecting a welding voltage, a contact is provided between welding electrodes to detect the voltage.

According to a third aspect of the present invention, in the automatic welding torch control apparatus according to the first or second aspect, the reference value is sampled from a waveform of current or voltage during welding at an arbitrary timing and level. It is characterized by being set as a value.

[0014]

According to the present invention, since the voltage during welding is detected from the ammeter terminal or between the arc electrodes, which is the basic structure of the welding machine, the electric wire cord for detection is externally applied to any welding machine. Can be installed easily. Also,
With the voltage amplifier circuit, a minute voltage waveform can be expanded to facilitate sampling. In addition, since the fluctuation detection range automatic setting circuit expands and extracts a part of the voltage waveform as a reference value or fluctuation and sets the sampling level, it is also applicable to welding methods with few voltage changes. can do.

Further, the fluctuation can be stabilized by converting the fluctuation into the effective value by the effective value conversion circuit. Further, in the reference value storage circuit, the value of the fluctuation amount at the start of welding during which welding is stable is stored as a reference value, and this reference value is made variable when necessary, and a new reference value is stored each time. Therefore, stable and highly accurate welding is possible.

Further, the difference comparison circuit compares the fluctuation amount of the current or voltage detected during welding, enlarged and further converted into an effective value with the reference value, and outputs the difference as an error signal. Based on this command of the error signal, the torch vertical drive circuit outputs a drive signal for the torch drive servomotor, and the torch can be moved up and down so as to eliminate the difference between the variation and the reference value. Further, the system control circuit can generate a signal having a timing for sampling the reference value and the variation, and a timing for synchronizing the operation of the entire device such as weaving.

As a result, even if the welding line changes vertically, the position of the welding torch itself is also properly controlled in the vertical direction, so welding can be performed with a stable current or voltage in accordance with the reference value.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings.

The automatic welding torch control device of this embodiment is constructed as shown in FIG. That is, the voltage detection terminal 1 for detecting the welding current or the welding voltage,
A voltage amplifying circuit 2 is connected which enlarges a minute voltage waveform to facilitate sampling, and a part of the voltage waveform is enlarged and taken out as a reference value or a variation in the voltage amplifying circuit 2, and its sampling level is taken out. The fluctuation detection range automatic setting circuit 3 for setting is connected. The voltage detecting terminal 1 is configured to detect a voltage drop by providing a contact at an ammeter terminal of a welding machine when detecting a welding current, and when detecting a welding voltage, a welding electrode. A contact is provided between them to detect the voltage.

Further, the fluctuation amount detection range automatic setting circuit 3 is connected with an effective value conversion circuit 4 for converting the fluctuation amount into an effective value and stabilizing it, and the effective value conversion circuit 4 has a reference value. The value storage circuit 5 is connected. The reference value storage circuit 5 stores, as a reference value, a variation value at the start of welding in which welding is stable, and when necessary, the reference value is made variable and a new reference value is stored each time. Is. A difference comparison circuit 6 is connected to both the effective value conversion circuit 4 and the reference value storage circuit 5. The difference comparison circuit 6 compares the reference value with the read value and outputs the difference as an error signal.

The difference comparison circuit 6 is connected to the torch vertical drive circuit 7. Then, based on the drive signal of the torch drive servomotor output from the torch vertical drive circuit 7, the torch is moved up and down so as to eliminate the difference between the variation and the reference value. further,
A system control circuit 8 is connected to the reference value storage circuit 5. The system control circuit 8 generates a timing signal so as to synchronize the sampling timing of the reference value and the variation and the operation of the entire device such as weaving.

The automatic welding torch control device of this embodiment having such a structure operates as described below. That is, the voltage waveform detected by the voltage detection terminal 1 is sent to the voltage amplifying circuit 2, and the voltage amplifying circuit 2 expands a minute voltage waveform so as to facilitate sampling. Subsequently, the fluctuation detection level automatic setting circuit 3 automatically sets the fluctuation detection level, and the effective value conversion circuit 4 converts the fluctuation into an effective value.

Further, in the reference value storage circuit 5, the value of the fluctuation amount at the start of welding during which the welding is stable is stored as a reference value, and this reference value is made variable when necessary, and a new reference value is provided each time. The value is stored. Next, the difference comparison circuit 6 compares the sampled fluctuation amount with the reference value, and outputs the difference as an error signal. Then, based on the command of this error signal, a signal for driving the torch drive servomotor is output from the torch vertical drive circuit 7, and the torch is moved up and down so as to eliminate the difference between the variation and the reference value. . On the other hand, the system control circuit 8 outputs a timing signal for sampling the reference value and the sampling of the variation, and a timing signal for synchronizing the operation of the entire device such as weaving.

As described above, according to the present embodiment, the current-voltage detection contact is provided at the ammeter terminal which is the basic construction of the welding machine to detect the voltage drop, or the contact is made between the arc electrodes. Since it is configured to detect the voltage during welding, the old type arc welder without a current control circuit to the inverter type new arc welder, etc.
It can be easily mounted externally to any welding machine. Further, since the voltage amplifying circuit 2 can enlarge a minute voltage waveform, sampling becomes easy. As a result, even if the vertical difference of the work is small, it is possible to use the work with high sensitivity even when the conventional method cannot cope with the poor sensitivity. Further, according to the present invention, it is possible to cope with the case where the vertical difference of the work is large and the variation range cannot be coped with only by the electric control because the sliding stroke is secured.

Further, since the fluctuation amount detection range automatic setting circuit 3 can automatically set the fluctuation amount detection level, only the fluctuation amount can be enlarged, and the voltage change can be suppressed by setting a high magnification. It can be applied even when there are few welding methods.

Further, although the pulsating flow component is considerably included in the welding current and voltage fluctuation portion, the fluctuation component can be converted into an effective value and stabilized by the effective value conversion circuit 4. Further, the reference value storage circuit 5 stores, as the reference value, the value of the fluctuation amount at the start of welding during which the welding is stable, and when necessary, the reference value is made variable and a new reference value is stored each time. be able to. As a result, even if the welding line changes in the vertical direction, the position of the welding torch itself is also appropriately controlled in the vertical direction, so that welding can always be performed with a stable current or voltage in accordance with the reference value.

Further, since the response speed is moderate to the welding arc, it has excellent arc stability over the entire range of small current to large current, and enables high-speed and high-efficiency welding with a good bead appearance. .

FIG. 2 is a schematic configuration diagram when the automatic welding torch control device of the present invention is applied to a welding device.
That is, as shown in FIG. 2, when welding a workpiece 9 of V-groove having a height change made of an aluminum material in multi-layer welding, a moving mechanism for driving the welding torch 10 so as to move on a circular locus ( A welding torch 10 is attached to a weaving mechanism (not shown), a torch vertical drive mechanism 11 (not shown). As the welding power source 12, an inverter type pulse MIG welding machine was used. Further, a cable 13 for voltage measurement derived from an automatic welding torch control device 14 is connected to a terminal of an ammeter of the welding machine. Further, the automatic welding torch control device 14 includes the voltage amplification circuit 2, the fluctuation amount detection range automatic setting circuit 3, the effective value conversion circuit 4, the reference value storage circuit 5, the difference comparison circuit 6, the torch vertical drive circuit 7, and the system. The circuit boards of the control circuit 8 are connected.

In the automatic welding torch control device 14, a sampling value from the voltage waveform about 3 seconds after the arc is stabilized from the start of welding is used as the first reference value, and the sampled reference value Vs is the sampling voltage Vs. As xα, the value of α was changed to obtain an appropriate enlargement factor for the variation.

In the welding apparatus as shown in FIG. 2, the welding torch starts welding at a preset torch height and welding conditions. Then, when the torch moves along the circular orbit along the welding line, the welding line is lowered, so that the protruding length of the wire is increased and the welding current is reduced. here,
The automatic welding torch control device 14 of the present embodiment detects this decrease in welding current, compares the variation sampled as described above with the reference value, and drives the torch based on this error signal command. Lower the torch to keep the welding current at the set value. Then, since the welding line rises when it goes over the bottom end of the welding machine, the welding torch is raised contrary to the past. Further, even when performing the welding of the second layer, the welding position is raised by the amount of the welding beads of the first layer, but the height of the welding torch is automatically adjusted by the automatic welding torch control device 14.

In the second layer welding, the reference value and the sampling time can be changed externally so as to change the welding condition and the weaving width. Furthermore, as welding continues, the temperature of the work rises, the penetration deepens at the same current, and the bead width widens, but the molten metal surface rises depending on the welding conditions. In order to correct this, the torch height can be controlled with a new reference value that is preset and stored every fixed number of times of sampling. As a result, it is possible to perform high-quality welding with a smooth appearance even on a work whose welding line shown in FIG. 2 changes vertically.

As described above, according to this embodiment, it is possible to perform automatic current control in pulse MIG welding of aluminum using an inverter welding machine, which has been difficult until now. Further, automatic copying can be performed even on a work in which the welding line changes up and down, such as rising and falling. Further, the sampling timing pulse for storing the reference value and the variation for a certain period of time can be applied by switching from the inside to the outside, so that it can be used in combination with the weaving, and better welding can be performed. Also, the conditions for multi-layer welding can be changed by automatically changing the reference value, and the vertical shift of the torch can be automatically followed.

The present invention is not limited to the above-described embodiment, and aluminum welding can be performed by connecting the automatic welding torch control device of the present invention to an inverter type AC arc welding machine. In this case, by setting the conditions so that the voltage can be sampled at the timing when the polarity changes to the polarity opposite to the positive polarity, the torch can be moved up and down in response to the up and down changes of the work, so it is stable. This enables highly accurate welding. Also, by controlling the biaxial slide and changing the torch mounting direction, fillet welding can be supported. Furthermore, since it can be dealt with by stopping the control when there is a crater, the presence or absence of a crater does not pose a problem.

[0034]

As described above, according to the present invention, it is possible to arbitrarily set and change the reference current and the voltage, and it is possible to attach it to any arc welding machine, and the height of the welding line. It is possible to provide an automatic welding torch control device that enables highly accurate welding by smoothly responding to changes.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an automatic welding torch control device of the present invention.

FIG. 2 is a schematic view showing an example of a welding machine to which the automatic welding torch control device of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Voltage detection terminal 2 ... Voltage amplification circuit 3 ... Fluctuation detection range automatic setting circuit 4 ... Effective value conversion circuit 5 ... Reference value storage circuit 6 ... Difference comparison circuit 7 ... Torch vertical drive circuit 8 ... System control circuit 9 ... Work 10 ... Welding torch 11 ... Torch vertical drive mechanism 12 ... Welding power source 13 ... Voltage measurement cable 14 ... Automatic torch control device

Claims (3)

[Claims] 1. An automatic welding torch controller for comparing a current or voltage during arc welding with a reference value and controlling a servomotor for driving a welding torch up and down based on the difference between the welding current and the welding voltage. A voltage detection terminal for detection, a voltage amplification circuit that expands a minute voltage waveform, a part of the voltage waveform is expanded as a reference value or fluctuation, and is taken out, and the sampling level is set. The circuit, the effective value conversion circuit that converts the fluctuation into the effective value, the value of the fluctuation at the start of welding is stored as the reference value, and this reference value is made variable when necessary, and a new reference value is set each time. A reference value storage circuit that stores the difference, a difference comparison circuit that compares the reference value and the read value and outputs the difference as an error signal, and a change value based on the drive signal of the servo motor. The automatic welding featured a torch vertical drive circuit that moves the welding torch up and down so as to eliminate the difference between the reference value and the reference value, and a system control circuit that generates a sampling timing signal for the reference value and fluctuations. Torch control device. 2. The voltage detection terminal is configured to detect a voltage drop by providing a contact at an ammeter terminal of a welding machine when detecting a welding current, and when detecting a welding voltage, A contact is provided between the welding electrodes so as to detect the voltage.
The automatic welding torch control device described. 3. The method according to claim 1, wherein the reference value is a value sampled from an electric current or voltage waveform during welding at an arbitrary timing and level.
The automatic welding torch control device described.