JPH09253846A - Measuring method for electric characteristics of welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute optimum control of welding in real time by measuring one or more items among a peak value, pulse width, base width, pulse frequency and arc short circuiting width. SOLUTION: An electric current signal 13, voltage signal 32 of a welding power source 8, which welds a base metal 1, are measured by a measuring circuit 11. The signals 13, 32 are passed to low pass filters 14, 33 of the cut off frequency higher than the pulse frequency of pulse power source. An output of the filter 14 is turned to a digital signal 19 by a peak hold circuit 17 and A/D converting circuit 18. A comparator 21 compares a welding current 16 with threshold level signal 22 and obtains a pulse width, base width, arc short circuiting width. Only the high frequency part only superimposed to welding current/voltage wave form is smoothed. The comparator 37 compares a threshold signal 38 and voltage signal 34 from a controller 10, welding is executed by setting the threshold level in conformance with the welding condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring electric characteristics of a welding device having a pulse power source. in particular,
Arc output voltage control (arc short width control, etc.) and pulse accent (pulse width and pulse current) required for advanced control of automatic pipe circumference welding that performs automatic circumference welding of steel pipes while performing high-speed weaving. Waveform collapse)
The present invention relates to a method for measuring the electrical characteristics of a welding device that can contribute to the realization of control of welding. In addition, the arc short means that the distance between the welding wire (electrode) and the base metal or molten metal becomes too short,
This is a state in which a short circuit has occurred between the two.

[0002]

2. Description of the Related Art In conventional butt arc welding of pipes, driving of weaving or the like is generally performed by a pulse motor for relatively low speed and by a servo motor for high speed. And in order to keep the torch in the optimum position for the work during the welding,
It is also practiced to monitor the current and voltage during welding and perform feedback control of the position of the torch so that the values are appropriate. The current / voltage measuring method therefor is performed by the method shown in FIG. That is, the pulse welding current / voltage signal 60 is passed through a low pass filter (LPF) 61 to form a smoothing signal 62, and an A / D converter (A /
According to D), it is measured as a digital current / voltage signal. However, the cutoff frequency of the LPF 61 was set to be much lower than the repetition frequency of the pulse welding current / voltage (for example, the pulse frequency of 100 to 40).
Cut-off frequency 10Hz against 0Hz).

As a patent document for pipe circumference welding,
JP-A-63-183776 and JP-A-4-284.
There is a 973 publication. The technique described in Japanese Patent Laid-Open No. 63-183776 relates to an arc rotary all-position welding device. In this method, the groove shape is narrow and high precision machining is required, and it is difficult to apply the method to a work having a wide groove width. The technique described in Japanese Patent Laid-Open No. 4-284973 relates to an automatic arc welding method in which welding of a groove portion is controlled in real time, but the point of measuring a pulse welding current / voltage waveform has not been solved.

[0004]

In order to perform optimum welding in pipe circumference welding, high-speed weaving, etc., more precise measurement of pulse welding current / voltage waveform is possible, arc output voltage control, pulse accent ( It is necessary to contribute to prevention control of the pulse width and the waveform of the pulse current.

In the conventional pulse welding current / voltage measurement,
It was difficult to measure the current / voltage waveform with high speed and high accuracy, and the measurement was at a response time of at most 10 times the repetition cycle of the pulse welding current / voltage. Therefore, for example, even if an attempt is made to correct a pulse accent, an arc short, or the like, the timing of the current, voltage, weaving command, etc. for correction is delayed. Moreover, since the characteristics of the pulse welding current / voltage waveform for each cycle cannot be grasped, it is difficult to perform sufficient analysis and countermeasures. Furthermore, it was impossible to accurately measure current and voltage at both ends of the weaving, which requires precise measurement and control in the shortest time.

The present invention is directed to arc output voltage control (arc short width control, etc.) and pulse necessary for advanced control of a pipe circumference automatic welding apparatus for performing automatic circumference welding of a steel pipe while performing high-speed weaving. An object of the present invention is to provide a method for measuring the electrical characteristics of a welding apparatus that can contribute to the realization of control of accents (corruption of pulse width and pulse current waveform).

[0007]

In order to solve the above problems, a method of measuring the electrical characteristics of a welding apparatus of the present invention is a method of measuring the electrical characteristics of a welding apparatus having a pulse power source; Each time, one or more of the peak value, pulse width, base width, pulse period, and arc short width are measured.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION One aspect of the present invention relates to an automatic pipe circumference welding apparatus for welding a welding torch with a pulse welding current while weaving the welding torch in the left-right direction with respect to the welding advancing direction. Various means in this form are shown below.

(1) Welding current and voltage signals are obtained from the welding power source, filtered, peak hold circuit, A / D
The peak value, pulse width, base width, pulse period, arc short width, etc. of pulse welding current / voltage are measured by the conversion circuit, comparator, counter, and threshold level signal. (2) As the filter, a low pass filter having a cutoff frequency higher than the frequency of pulse welding current / voltage is used. (3) The threshold level signal has a pulse width and a base width and / or an arc short width. (4) The threshold level is made variable by software or the like.

The operation of the above means in the high-speed weaving control using the automatic pipe circumference welding apparatus will be described below. (1) Measurement of pulse welding current / voltage, that is, peak value,
Since the pulse width, base width, arc short width, etc. can be grasped for each waveform, it is necessary for controlling the arc output voltage (arc short width control, etc.) and pulse accent (deformation of pulse width and pulse current waveform). You can get information. (2) Only the high frequency component superimposed on the pulse welding current / voltage waveform is smoothed, and the pulse welding current / voltage waveform is kept as it is. (3) The pulse width, the base width, and the arc short width can be measured by the threshold level signal. (4) Since the threshold level can be changed by software, it can be arbitrarily set to changes in welding work conditions (pipe diameter, steel type, etc.).

As described above, the torch position is provided by providing a circuit for measuring the pulse welding current / voltage, that is, the peak value, the pulse width, the base width, the arc short width, etc. for each waveform. Control and pulse anti-corruption control can be performed to perform high-speed and high-accuracy automatic pipe circumference welding.

[0012]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram regarding measurement of a pulse welding current / voltage waveform of a pipe circumference automatic welding apparatus according to an embodiment of the present invention. Here, reference numeral 1 is a base material such as a pipe, 2
Is a groove, 3 is a weld metal, 4 is a welding wire, 5 is an arc, 6 is a torch, 7 is a welding current supply cable, and 8 is a welding power supply device for pulse MAG welding, for example. The torch 6 is weaved left and right in the groove 2.
The welding wire 4 is fed at a constant speed and is melted by the arc 5 to become the deposited metal 3, which solidifies in the groove 2 and joins the base material 1. The pulse MAG welding is described, for example, in “Welding Technology”, February 1989, pages 67 to 76.

The welding power source 8 supplies a large pulse current to the welding torch 6. Reference numeral 9 is a control cable, and 10 is a control device. The control device 10 is composed of a microcomputer, and controls the welding power supply device 8, a drive device (not shown) running, the weaving of the torch 6, the pulse welding current / voltage measuring circuit 11, and the like. The pulse welding current / voltage measuring circuit 11 obtains the pulse welding current signal 13 and the pulse welding voltage signal 32 from the welding power source device 8,
Input to filters 14 and 33 respectively. In addition,
The "voltage signal" and the "current signal" as used herein mean that the signals represent a welding voltage and a welding current, respectively, and that the signals are represented by a voltage level and a current level. is not. Normal,
These voltage and current signals are represented by voltage levels.

FIG. 2 shows an example (filter input) of the pulse welding current / voltage signal. In the figure, (a) shows the voltage signal 32 and (b) shows the current signal 13. Voltage signal 32
Is a pulse waveform of a predetermined cycle, and a high-frequency noise component 15 is superimposed. A base voltage portion 51 of the pulse waveform includes a voltage drop waveform portion 50 indicating occurrence of an arc short. The current signal 13 corresponding to the voltage signal 32 also includes the high-frequency noise component 15 like the voltage signal 32. A high-frequency noise component 15 is superimposed on the pulse welding current signal 13, and a waveform portion 52 corresponding to the waveform portion 50 of the voltage signal 32 is shown. As described above, the filters 14 and 33 have a cutoff frequency higher than the pulse frequency of the pulse power source, remove the high frequency noise component 15, and output the pulse welding current signal 16 and the pulse welding voltage signal 34. Thereby, it is possible to prevent a malfunction of the electrical characteristic measurement due to the high frequency noise. Further, by using a filter having such a cutoff frequency, the pulse waveforms of the current signal 13 and the voltage signal 32 can be maintained, and the electrical characteristics can be measured in pulse units by a method described later.

FIG. 3 shows an example of the pulse welding current / voltage signal output by the filters 14 and 33. 3A shows a voltage signal, and FIG. 3B shows a current signal. The pulse welding current signal 16 and the pulse welding voltage signal 34 are obtained by removing the respective high frequency noise components 15 from the voltage signal 32 and the current signal 13 by the filters 14 and 33. In the figure, I1 is the peak value of the current signal, E2 is the base voltage of the voltage signal, T1 is the pulse width of the current signal (and voltage signal), T2 is the base width of the current signal (and voltage signal), and T3 is the voltage signal. (And current signal) arc short width, T4 is current signal (and voltage signal) repetition period, and H1 is pulse width and base width measuring threshold level signal 22 for current signal 16.
, H2 is the level of the arc short width measuring threshold level signal 38 with respect to the voltage signal 34.

The peak hold circuit 17 in the measuring circuit 11 of FIG. 1 detects and holds the peak value of the pulse welding current signal 16 output from the filter 14 at each time interval determined by the timing signal 20. This peak value is converted into a digital signal 19 by the A / D conversion circuit 18 according to the timing signal 20. It should be noted that the timing signal 20 corresponds to the control device 10 by an interrupt circuit 24 described later.
The control device 10 outputs according to the interruption to

The comparator 21 compares the threshold level signal 22 given from the control device 10 with the pulse welding current signal 16 (see FIG. 3B), and when the pulse welding current signal 16 exceeds the threshold level signal 22. The output signal 23 is set to the low level, and when the pulse welding current signal 16 becomes smaller than the threshold level signal 22, the output signal 23 is set to the high level. Interrupt circuit 24
Outputs an interrupt signal to the control device 10 at the falling edge of the output signal 23. As a result, the control device 10 recognizes the rising edge of the pulse waveform of the welding current signal 13, generates the timing signal 20 described above, and outputs the timing signal 20 at the timing for processing such as welding line tracing control during arc during high speed weaving. Can be used as The output signal 23 is input to the counter 25, and the inverted signal of the output signal 23 by the inverting circuit 27 is input to the counter 30. The counter 25 keeps the output signal 23 at a high level (that is, the current signal 16 is at the threshold signal 22).
Lower level period), enabled, controller 10
Is counted. As a result, the time T2 of the current signal 16 is obtained and output as the base width 26. On the other hand, the counter 25 is enabled while the output signal 23 is at the low level (that is, the current signal 16 is at the higher level than the threshold signal 22) and counts the clock signal 44 from the control device 10. As a result, the time T1 of the current signal 16 is obtained, and the pulse width 3
Output as 1. Based on the pulse width 31, a pulse accent can be prevented. The pulse period T4 is
It is obtained by the addition process of time T1 and time T2. Alternatively, the pulse period can be obtained from the command value. The pulse period can be used together with the arc short width for the above-described welding line copying control in the arc.

The comparator 37 is provided with a threshold level signal 38 for arc short circuit provided from the controller 10.
And the voltage signal 34 are compared (see FIG. 3A), and the voltage signal 34 is the threshold level signal 38 for arc short circuit.
When the voltage becomes smaller, the output signal 39 is set to a high level, and when the voltage signal 34 exceeds the threshold level signal 38, the output signal 39 is set to a low level. Counter 41
Counts the clock signal 45 from the controller 10 while the output signal 39 is at a high level. As a result, the time T3 of the voltage signal 34 is obtained and output as the arc short width 42. The threshold level signal 22 and the arc shorting threshold level signal 38 can be variably controlled by the controller 10 according to changes in welding work conditions (pipe diameter, steel grade, etc.). In addition, 46 is a pulse current /
It is a signal between the voltage measurement circuit 11 and the control device 10, and includes the various signals described above. It should be noted that the clock signals 43, 44, and 4 are, of course, required for highly accurate measurement.
5 has a cycle sufficiently shorter than the time width of the measurement target.

FIG. 4 shows an outline of timing regarding each signal of the measuring circuit 11 shown in FIG. 1
Reference numerals 6 and 34 denote outputs of the filters 14 and 33, which are the same as those shown in FIG. At the rising edge of the current signal 16 output from the filter 14, the comparator 21
Output signal 23 falls, which causes the above-described interrupt circuit 24 to interrupt the control device 10. Control device 10
Generates a timing signal 20 in response to this. The output of the peak hold circuit 17 is reset by this timing signal 20, and then the next timing signal 20
The peak value of the signal 16 is detected and held until generation.
In this example, the peak value is the high level value of the pulse of signal 16 and is held until the next occurrence of timing pulse signal 20. The output signal 23 of the comparator 21 is
The level is high during the base width time T2 of the current signal 16, and this period is measured by the counter 25 as described above. The output signal 28 of the inverting circuit 27 has a waveform obtained by inverting the output signal 23, and its high level period corresponds to the pulse width time T1 of the current signal 16. This time T1 is measured by the counter 30 as described above. Comparator 3
The output signal 39 of 7 becomes high level during the arc short time T3 of the voltage signal 34, and this time T3 is measured by the counter 41 described above.

FIG. 6 shows another example of the pulse welding current / voltage measuring method. In the figure, (a) is a voltage signal and (b) is a current signal. Here, unlike the above-described FIG. 3, the peak value, the pulse width, and the base width are obtained from the voltage signal 34,
The arc short width is obtained from the current signal 16. By comparing the voltage signal 34 and the threshold level H3,
The pulse width T1 ', the base width T2', and the period T4 'can be obtained. Current signal 16 and threshold level H4
The arc short width T3 ′ can be obtained by comparing However, the data obtained in FIG. 3 is mainly used in consideration of the reliability of measurement due to the difference in signal amplitude.

As described above, the pulse welding current / voltage, that is, the peak value, the pulse width, the base width, the arc short width, etc. can be measured for each waveform, and the torch position control, the pulse accent prevention control, and the high speed are controlled. It is possible to perform welding line copying control in the arc during weaving, and to provide a high-speed and highly-accurate automatic pipe circumference welding device, which greatly contributes to the industry.

[0022]

According to the present invention, the following effects can be obtained. (1) Since the electrical characteristics such as the peak value, pulse width, base width, arc short width of the pulse welding current waveform and voltage waveform can be measured in real time, detailed welding can be performed for each pulse welding current waveform and voltage waveform. Data can be collected and optimal control can be performed in real time. (2) Similarly, since it is possible to measure the "current" and "voltage" at both end points of the weaving by being able to measure the above-mentioned various electrical characteristics in real time, weaving can be performed accurately and in real time even at high speed weaving. Copy control can be performed based on the difference between “current” and “voltage” in the left and right rows. (3) Pulse accent prevention control, arc voltage output control, etc. can be performed based on the values of the "current" and "voltage".

[Brief description of drawings]

FIG. 1 is a block diagram regarding measurement of a pulse welding current / voltage waveform of a pipe circumference automatic welding apparatus according to an embodiment of the present invention.

FIG. 2 is a chart showing an example (filter input) of a pulse welding current / voltage signal.

FIG. 3 is a chart showing an example (filter output) of a pulse welding current / voltage signal.

FIG. 4 is a chart showing an outline of timing.

FIG. 5 is a diagram schematically showing an outline of a filter and an input / output signal relating to conventional pulse welding current / voltage measurement.

FIG. 6 is a chart showing another example of a pulse welding current / voltage measuring method.

[Explanation of symbols]

1 ... Base material, 2 ... Bevel, 3 ... Weld metal, 4 ... Welding wire,
5 ... Arc, 6 ... Torch, 8 ... Welding power supply, 10 ...
Control device, 11 ... Circuit for measuring pulse welding current / voltage, 1
3 ... Pulse welding current signal, 14 ... Filter, 22 ... Threshold level signal, 26 ... Pulse width, 31 ... Base width, 32 ... Base voltage, 33 ... Filter, 38 ... Arc short threshold level, 42 ... Arc short width, 50 ... Arc short waveform part

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Ikuo Mibu 2982-3 Sugaya, Naka-machi, Naka-gun, Ibaraki Prefecture (72) Kenichi Maeda 1225-47 Tenjinbayashi, Hitachiota-shi, Ibaraki Prefecture

Claims (6)

[Claims] 1. A method for measuring the electrical characteristics of a welding apparatus having a pulsed power supply; for each pulse, one or more of its peak value, pulse width, base width, pulse period and arc short width. A method for measuring electrical characteristics of a welding apparatus, which is characterized by measuring items. 2. The method for measuring electric characteristics of a welding apparatus according to claim 1, wherein the welding current and the welding voltage are measured through a low-pass filter having a cutoff frequency higher than the pulse frequency of the pulse power source. 3. The measurement of the electrical characteristics of the welding apparatus according to claim 1, wherein a threshold value is provided to obtain the pulse width and the base width, and the threshold value and the welding current and / or welding voltage are compared. Method. 4. The method for measuring the electrical characteristics of a welding apparatus according to claim 1, wherein a threshold value is provided to obtain the arc short width, and the threshold value is compared with a welding current and / or a welding voltage. 5. The method for measuring the electrical characteristics of a welding device according to claim 3, wherein the threshold value can be arbitrarily changed according to the conditions of welding work. 6. The pipe circumference automatic welding device according to any one of claims 1 to 5, wherein the welding device is a pipe circumferential welding device for butt-welding steel pipes with a pulse welding current while weaving the welding torch in the left-right direction with respect to the welding proceeding direction. 2. A method for measuring the electrical characteristics of a welding device according to claim 1.