JPH0890230A - Arc welding monitor - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the device cost by eliminating the need for high-speed sampling and complicated calculation, enhance the CPU function, and further improve the measurement accuracy or monitoring accuracy by setting an arbitrary averaging time. [Configuration] An analog voltage signal VE representing the arc voltage E is obtained at the output terminal of the arc voltage detection circuit 18. V-
The F conversion circuit 20 receives the voltage signal VE and inputs a pulse signal PE having a frequency substantially proportional to the voltage level.
Is output. The counter 22 counts the pulse signal PE at regular time intervals and gives the count value NE to the CPU 24. An analog voltage signal VI representing the welding current I is obtained at the output terminal of the welding current detection circuit 28. The VF conversion circuit 20 receives this voltage signal VI and outputs a pulse signal PI having a frequency substantially proportional to its voltage level. The counter 22 counts the pulse signal PI at regular time intervals and gives the count value NI to the CPU 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding monitor device for monitoring arc welding.

[0002]

2. Description of the Related Art In arc welding, when a voltage is applied between a welding electrode (arc welding rod) and a material to be welded (base metal), the tip of the welding electrode is heated by arc heat to form droplets and become a base metal surface. It is a welding method for fusion welding the materials to be welded by utilizing the phenomenon of transition to No. 2, and is widely used for processing automobiles, electric / electronic parts and the like.

In arc welding, the welding current and arc voltage reflect the welding condition or welding result. However, since the ionosphere (gas) called arc constitutes a part of the welding circuit, the welding current is too high to measure the instantaneous value. And the arc voltage fluctuates drastically. Therefore, a method is used in which the welding current and the arc voltage are averaged at regular intervals and the average value is used as the measured value.

A conventional arc welding monitor device converts an analog output signal of a sensor for detecting a welding current or an arc voltage into a digital signal (sampling data) by an A / D converter, and A / D in a CPU (microprocessor). The sampling data from the D converter is accumulated at fixed time intervals T, and the accumulated value is divided by the accumulation time T to obtain the average value of the sampling data, and the average value of the welding current or arc voltage is then obtained. I was asking. Then, the average value is compared with the monitoring value, and the welding status or the welding result is determined from the comparison result.

FIG. 7 is a flow chart showing the arithmetic control operation of the CPU in the conventional arc welding monitor. C
Each time the PU takes in a digital signal (sampling data) from the A / D converter, the PU stores the sampling data in the memory (step 100). When sampling data for a certain averaging time T is fetched (step 102), the sampling data is accumulated, and the accumulated value is divided by the averaging time T to obtain the average value of the sampling data and thus the welding current. Alternatively, the average value (measured value) of the arc voltage is obtained (step 104), the average value (measured value) is stored in the memory, and at the same time, the used sampling data for one cycle is deleted (step 10).
6). Then, the average value (measured value) is compared with the monitored value to determine whether the arc welding in the averaging time (monitored section) T is normal or abnormal (step 10).
8) Display output of the determination result (steps 110, 11)
2). The above process is repeated until the welding time ends (steps 114 and 116).

[0006]

In the CPU processing in the conventional arc welding monitor apparatus as described above, if an attempt is made to increase the accuracy of measuring the welding current or the arc voltage, a high-speed (for example, sampling frequency of 5000 Hz) A
The / D converter is required, therefore the CPU also needs to have a high speed, and the memory for storing the sampling data also needs to have a large capacity, resulting in a high device cost.

In addition, since the CPU spends most of the processing time in fetching the sampling data, other monitoring control such as welding condition switching and switch control is performed during the measurement monitoring processing (100 to 116). It was difficult to do.

Further, since averaging calculation and storage management of sampling data are troublesome, the averaging time cannot be set arbitrarily, and at present, 20 msec and 50 mse.
Only one of the three averaging times of c and 100 msec is selected, which makes it difficult to adapt to various welding conditions. For example, in some arc welding, when the averaging time is set to 70 msec, the most accurate average value (measured value) should be obtained, but 50 ms
Since the measurement can be performed only with the averaging time of ec or 100 msec, an error may occur in the measurement accuracy or the monitoring accuracy.

The present invention has been made in view of the above problems. It reduces the cost of the apparatus by eliminating the need for high-speed sampling and complicated calculation, enhances the CPU function, and further, can be used for various welding conditions. An object of the present invention is to provide an arc welding monitor device capable of setting an averaging time and improving measurement accuracy or monitoring accuracy.

[0010]

In order to achieve the above object, a first arc welding monitor apparatus of the present invention is an arc welding monitor apparatus for monitoring arc welding by an arc welding machine, which comprises a welding electrode and a base metal. Of the welding current flowing through the welding current detection means for outputting an analog voltage signal representing the current value of the welding current, and a frequency substantially proportional to the voltage level of the analog voltage signal from the welding current detection means. A voltage-frequency conversion circuit for converting to a pulse signal having, pulse counting means for counting the pulse signal from the voltage-frequency conversion circuit at constant time intervals, and at constant time intervals based on the count value from the pulse counting means. Of welding current average value calculating means for obtaining the average value of the welding current, and based on the average value of the welding current obtained by the welding current average value calculating means It has a configuration comprising a determination means for determining welding conditions or welding results.

A second arc welding monitoring device of the present invention is an arc welding monitoring device for monitoring arc welding by an arc welding machine, detects an arc voltage between a welding electrode and a base metal, and detects the voltage of the arc voltage. An arc voltage detecting means for outputting an analog voltage signal representing a value, a voltage-frequency conversion circuit for converting the analog voltage signal from the arc voltage detecting means into a pulse signal having a frequency substantially proportional to its voltage level, A pulse counting means for counting the pulse signal from the voltage-frequency conversion circuit at regular time intervals, and an arc voltage average value for obtaining an average value of the arc voltage at constant time intervals based on the count value from the pulse counting means. A welding condition or a welding result is calculated based on the average value of the arc voltage obtained by the calculating means and the arc voltage average value calculating means. It has a configuration comprising a constant determining means.

[0012]

In the present invention, the pulse counting means counts the pulse signal output from the voltage-frequency conversion circuit at regular intervals. This pulse count value is proportional to the average value of the frequency of the pulse signal at the counting time, and in turn is proportional to the average value of the arc welding measurement target (welding current or arc voltage). Therefore, the average value of the arc welding measurement target can be obtained from the pulse count value without requiring a special calculation. By comparing this average value with the monitoring value, the welding status or welding result of arc welding can be determined based on the comparison result.

[0013]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the overall construction of an embodiment in which the arc welding monitor device of the present invention is applied to a DC arc welding machine. This DC arc welder applies a DC voltage between the welding electrode (welding wire) 14 and the base metal 16 on the welding torch 12 side of the power supply device 10 to perform MIG welding or MAG welding by the gas shield arc welding method. . Welding wire 1
4 and the base metal 16, an arc is generated in an atmosphere of a shielding gas composed of an inert gas or carbon dioxide gas, and the consumable welding wire 14 is melted and sent to the base metal 16 side at a predetermined speed. It is being paid.

In this arc welding machine, the arc welding monitor device of this embodiment is provided with means for detecting the arc voltage and the welding current as follows.

In order to detect arc welding, a pair of input terminals of an arc voltage detecting circuit 18 are connected to the welding wire 14 and the base material 16, respectively. Arc voltage detection circuit 1
The output terminal of 8 is connected to the input terminal of the VF (voltage-frequency) conversion circuit 20, and the output terminal of the VF conversion circuit 20 is connected to the input terminal of the counter 22. Counter 2
The output terminal of 2 is connected to the data terminal of the CPU 24. During arc welding, an analog voltage signal VE representing the arc voltage E is obtained at the output terminal of the arc voltage detection circuit 18. The V-F conversion circuit 20 receives the voltage signal VE and outputs a pulse signal PE having a frequency substantially proportional to the voltage level. The counter 22 counts the pulse signal PE at regular time intervals, and the counted value NE is CP.
Give to U24.

Further, in order to detect the welding current, a current detection coil 26 is attached to the conductor 17 connecting the power supply device 10 and the base material 16, and the output terminal of this coil 26 is the input terminal of the welding current detection circuit 28. Are connected. The output terminal of the welding current detection circuit 28 is connected to the input terminal of the VF conversion circuit 30, and the output terminal of the VF conversion circuit 30 is connected to the input terminal of the counter 32. The output terminal of the counter 32 is connected to the data terminal of the CPU 24. During arc welding, an analog voltage signal VI representing the welding current I is obtained at the output terminal of the welding current detection circuit 28. V
The -F conversion circuit 20 receives the voltage signal VI and inputs a pulse signal P having a frequency substantially proportional to the voltage level.
Output I. The counter 22 counts the pulse signal PI at regular time intervals and gives the count value NI to the CPU 24.

The CPU 24 includes a keyboard 34 and a ROM 3
6, RAM 38, display device 40, printer 42, external interface circuit 44, etc. are also connected, and ROM
By executing the program stored in 36, various calculations and controls in this arc welding monitor device are performed. The RAM 38 stores not only the data calculated by the CPU 24, but also various setting value data such as a monitoring value input through the keyboard 34 and an averaging time. The display device 40 and the printer 42 are used to output measurement values, determination results, and the like. The interface 44 is
It is used to connect to the controller of an arc welder.

FIG. 2 is a flow chart showing the processing operation of the CPU 24 when the arc welding monitoring apparatus uses the general averaging method to perform the arc welding monitoring processing. Here, the general averaging method is a measuring method for obtaining an average value within each averaging time Ti by periodically repeating the averaging time T on the time axis as shown in FIG.

When a welding current I as shown in FIG. 3A flows during arc welding, a voltage signal VI having a voltage waveform corresponding to the current waveform of the welding current I is generated by the welding current detection circuit 28.
Will be output. The voltage signal VI is converted into a pulse signal PI as shown in FIG. 3B by the VF conversion circuit 30. The pulse signal PI is input to the counter 32, and the count value of the pulse signal PI is obtained at the output terminal of the counter 32. For example, when the V-F conversion circuit 30 operates so as to output the pulse signal PI having a frequency of 1 MHz with respect to the input voltage of 10V, the voltage signal VI is 10 at 1V.
When it continues for msec, the counter 32 becomes 1000 during that period.
The number of (pulse) pulse signals PI will be counted.

In FIG. 2, the CPU 24 reads the output of the counter 32 at the end of each averaging time Ti and determines the pulse count value NIi for the averaging time Ti (steps 1 and 2). This count value NIi is proportional to the average value of the frequency of the pulse signal PI at the averaging time Ti, and thus to the average value of the voltage level of the voltage signal VI, that is, the current average value of the welding current I. Therefore, the average value MIi of the welding current I is obtained by multiplying the count value NIi by a predetermined constant (calibration value), and the CPU 24 once stores this average value MIi in the RAM 38 as a measured value (step 2). Next, the CPU 24 reads the average value MIi and the welding current monitoring value from the RAM 38 and compares them (step 3). The welding current monitoring value is set as an upper limit and a lower limit monitoring value. CPU 24
Indicates that the average value (measured value) MIi is within the range of the upper and lower limit monitoring values, the welding is normal, and if the average value MIi is out of the range, it is determined that the welding is abnormal. (Steps 4 and 5). Then, the above processing is repeated until the welding time ends (steps 6 and 7).

In addition, the step 1 is executed by the timer circuit,
The CPU 24 may process steps 2 to 6 by interruption. By doing so, the CPU 24 can devote a large amount of time to other processing such as condition switching and interface processing, so that the CPU processing can be made more sophisticated and multifunctional.

2 and 3 show the action of the portion (24 to 32) for monitoring the arc welding with respect to the welding current I, the portion (18 to 24) for monitoring the arc welding with respect to the arc voltage V is shown. Also has the same effect as above. These two monitoring systems may be operated selectively or simultaneously.

As described above, in the arc welding monitor apparatus of this embodiment, the pulse signals (PV, PI) output from the VF conversion circuits (20, 30) are counted (22, 32).
The pulse count value (MVi, MIi) per each averaging time Ti is directly proportional to the average value of the arc voltage E and the welding current I within each averaging time Ti. The CPU 24 can obtain the average value (measured value) of the arc voltage E and the welding current I without any special calculation by merely reading the outputs of the counters (22, 32) at the end of each averaging time Ti. it can. As described above, since it is not necessary to continuously take in the sampling data or to perform a troublesome average value calculation, it is possible to devote a lot of time to other processing.

The combination of the VF conversion circuit (20, 30) and the counter (22, 32) is a much cheaper circuit than the high speed A / D converter, and the CPU 24 is also particularly high speed. Since the RAM 36 does not need to store sampling data and a small-capacity memory is sufficient for the RAM 36, the apparatus cost is significantly reduced as compared with the conventional arc welding monitor apparatus.

Further, it is not necessary to reset the number of sampling data, the average value calculation formula, etc. every time the averaging time Ti is changed, and the averaging time Ti can be determined by managing (recognizing) the counting time. Even with the values, the average value of the arc voltage E and the welding current I at the averaging time Ti can be easily determined from the pulse count values (MVi, MIi) of the counters (22, 32), so that the averaging time Ti can be set to various types or arbitrarily. Can be set. Therefore, it is possible to set the optimum averaging time T for various welding conditions, and it is possible to improve the measurement or monitoring accuracy.

In addition, the flexibility of the averaging process in this embodiment has a great effect when the averaging measurement is performed by the moving average method.

FIG. 4 is a flow chart showing the processing operation of the CPU 24 when performing monitoring control of arc welding using the moving average method. Here, the moving average method means that the averaging time T is set to a constant pitch δ on the time axis as shown in FIG.
This is a measuring method for obtaining an average value within each averaging time Ti for each moving pitch δ while moving at (δ <T). For convenience of explanation, in FIG. 4, the voltage signal VI, that is, the waveform (A) of the welding current I and the waveform (B) of the pulse signal PI are the same as the waveforms (A) and (B) of FIG. 3, respectively. .

Also in the moving average method, a voltage signal VI having a voltage waveform corresponding to the current waveform of the welding current I is obtained at the output terminal of the welding current detection circuit 28, and this voltage signal VI is V-.
The pulse signal PI is converted by the F conversion circuit 30, and this pulse signal PI is input to the counter 32, and the count value of the pulse signal PI is obtained at the output terminal of the counter 32.

However, in the moving average method, the timing at which the CPU 24 reads the count value of the counter 32 is different from the general averaging method. That is, as shown in FIG.
Reads the output NI of the counter 32 at the end of the movement time .delta.i and determines the pulse count value N.delta.i for the movement time .delta.i (steps 1 ', 2A). In this way, the pulse count value Nδi calculated for each moving pitch is calculated and stored in the memory, whereby the averaging time Ti
The minute pulse count value NIi can be obtained from the following equation (step 2B). NIi = NIi-1 + N [delta] i-N [delta] i-3 (1)

Here, Nδi-3 is the immediately preceding averaging time T
It is the pulse count value Nδi corresponding to the moving time δi-3 corresponding to the difference between the starting points of i-1 and the current averaging time Ti. The processing (steps 3 to 7) after obtaining the pulse count value NIi for each averaging time Ti in this manner may be performed in the same manner as in the general averaging method.

4 and 5, the operation of the portion (24 to 32) for monitoring the arc welding with respect to the welding current I is shown, but the portion (18 to 24) for monitoring the arc welding with respect to the arc voltage V is shown. Also in, the same operation as described above may be performed.

According to such a moving average method, meaningless noise such as undershoot and overshoot contained in the measurement object (welding current, arc voltage) or measurement data,
The fluctuations can be removed or absorbed in a wide averaging time T, while at the same time, substantial arc fluctuations can be reduced in a narrow moving pitch δ.
Can be captured with certainty. For that purpose, it is preferable that the averaging time T and the moving pitch δ can be set to arbitrary values, respectively. However, as described above, the arc welding monitoring apparatus of the present embodiment meets this condition, and the moving average method is used. The practicality of can be improved.

The above calculation formula (1) is an example, and the average value calculation in the moving average method can be variously modified without burdening the software. In the moving average method, as shown in FIG. 6, a counter (for example, 32) is used.
, 32N are provided, and the counters 32A, 32B, ..., 32N are sequentially switched and counted for each moving time δi, so that the count value NIi for each averaging time Ti is any. The counter output can be obtained as it is. As a result, the CPU2
In No. 4, the average value can be immediately calculated by only reading the output of the counter at each moving time δi.

In the circuit configuration of FIG. 6, the moving pitch δ or the length of the averaging time T is set separately for each counter (for example, the averaging time is counted by the counter 32A).
Is 20 msec, counter 32B is 50 msec,
..., by allocating 100 msec to the counter 32N), it is possible to monitor arc welding in a more multi-view manner.

The arc welding machine in the above-mentioned embodiment is N
I did IG welding or MAG welding, but PI
The present invention can also be applied to an arc welder that performs G welding.

[0037]

As described above, according to the arc welding monitor apparatus of the present invention, the combination of the voltage-frequency conversion circuit and the pulse counting means eliminates the need for high-speed sampling and complicated calculation. The CPU function can be improved at the same time as the cost is reduced, and an arbitrary averaging time can be set for various welding conditions, so that the measurement accuracy or monitoring accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment in which an arc welding monitor device of the present invention is applied to a DC arc welding machine.

FIG. 2 is a flowchart showing a processing operation of a CPU when performing arc welding monitoring processing using a general averaging method in the arc welding monitoring apparatus of the embodiment.

FIG. 3 is a diagram for explaining an operation of average value measurement by a general averaging method in an example.

FIG. 4 is a CPU when performing arc welding monitoring processing using the moving average method in the arc welding monitoring apparatus of the embodiment.
3 is a flowchart showing the processing operation of FIG.

FIG. 5 is a diagram for explaining average value measurement by a moving average method in an example.

FIG. 6 is a block diagram showing a modification of the counter circuit in the arc welding monitor apparatus of the embodiment.

FIG. 7 is a flowchart showing an arithmetic control operation of a CPU in a conventional arc welding monitor device.

[Explanation of symbols]

 14 welding wire (welding electrode) 16 base material 18 arc voltage detection circuit 20,30 voltage-frequency conversion circuit 22,32 counter 24 CPU (microprocessor) 26 current detection coil 28 welding current detection circuit 36 ROM 38 RAM

Claims (2)

[Claims] 1. An arc welding monitoring device for monitoring arc welding by an arc welding machine, wherein a welding current flowing through a welding electrode and a base metal is detected and an analog voltage signal representing a current value of the welding current is output. A detection means; a voltage-frequency conversion circuit for converting the analog voltage signal from the welding current detection means into a pulse signal having a frequency substantially proportional to its voltage level; and the pulse signal from the voltage-frequency conversion circuit. With a pulse counting means for counting every fixed time, a welding current average value calculating means for obtaining an average value of the welding current for each constant time based on the count value from the pulse counting means, and the welding current average value calculating means. An arc for determining the welding condition or the welding result based on the obtained average value of the welding current. Contact monitoring device. 2. An arc welding monitor device for monitoring arc welding by an arc welding machine, which detects an arc voltage between a welding electrode and a base metal and outputs an analog voltage signal representing a voltage value of the arc voltage. Detecting means, a voltage-frequency converting circuit for converting the analog voltage signal from the arc voltage detecting means into a pulse signal having a frequency substantially proportional to its voltage level, and the pulse signal from the voltage-frequency converting circuit. With a pulse counting means for counting at fixed time intervals, an arc voltage average value calculating means for obtaining an average value of the arc voltage at constant time intervals based on the count value from the pulse counting means, and the arc voltage average value calculating means. Determination means for determining the welding status or the welding result based on the obtained average value of the arc voltage. Arc welding monitoring device for.