JPH08118030A - Method and device for eliminating arc sound of ac plasma welding - Google Patents

Abstract

PURPOSE: To prevent noise in plasma welding of rectangular wave with simple means by detecting plasma arc welding current wave form in welding of AC plasma arc welding and generating the sound wave of reversed phase at the position to reduce noise against the arc sound generated by plasma arc. CONSTITUTION: The noise sound wave 2 generated from a welding arc 1 contains a component 3 harmful to human ear. The sound wave 4 similar to the harmful component 3 is generated from a speaker 5 to make minus by the same intensity as the sound pressure of harmful component 3 is turned to plus. When both sound waves are overlapped, the harmful component 3 is canceled with the sound wave from speaker 5 to be eliminated or attenuated. Thus, a worker executing AC plasma welding is not required to use ear plug. The noise attenuated is particularly of harmful arc sound only, because of being different from ear plugged case, other signal sound can be heard, thus, efficient and safety of work are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for eliminating a characteristic arc noise generated during welding using a rectangular wave AC plasma welding machine.

[0002]

2. Description of the Related Art AC welding using a shielding gas is a welding method which is used for welding aluminum and the like and utilizes the property of destroying the oxide film (alumina) of aluminum when the polarity is reversed (when the base metal is minus). is there. Conventionally, a sine wave alternating current using a commercial frequency was used, but with a sine wave, half of the welding energy is consumed in the destruction of alumina due to the reverse polarity, and in the case of plasma welding or TIG welding, the positive electrode that becomes the actual welding energy. The time was half and there was a problem in efficiency.

With the recent widespread use of inverter power supplies, it has become possible to use a rectangular wave alternating current whose reverse polarity is only 10 to 20% in one cycle, and it has been proved that alumina can be sufficiently removed at that ratio, and various types are generally used. It has begun to be used for welding machines, and the same is true for plasma welding machines.
However, in plasma welding, unlike other welding methods, a plasma gas is used, so jet noise is also added, which is a harmful noise peculiar to switching between forward and reverse rectangular waves. For example, 200A positive electrode normal welding can be used for stainless steel 8
60 mm at a distance of 1 m when performing mm keyhole welding
As for the noise of B or less, if it is necessary to weld 200 mm of square wave plasma welding with 20% of the reverse polarity component added, aluminum of 4 mm will reach 95 dB at the same distance.

[0004]

The sound pressure of 95 dB is comparable to the noise generated when a large truck is traveling, and the earplugs of the operator are a necessity. It is desired to reduce this noise to 60 dB or less, which is the sound pressure of daily conversation. Currently, sound barriers are considered as a noise countermeasure other than earplugs, but they significantly impede the work flow at the welding site and are expensive. An object of the present invention is to reduce noise of rectangular wave plasma welding by a simple means.

[0005]

Means for Solving the Problems The present invention is to solve the above problems, and detects a plasma arc current waveform or a voltage waveform during welding in AC plasma arc welding, and detects an arc sound generated by the plasma arc. This is a method of eliminating arc sound in AC plasma arc welding, characterized in that both sound waves are attenuated by generating sound waves having opposite phases at a position where noise should be reduced.

Further, a detector for taking in a signal synchronized with the plasma arc sound, a waveform shaper for taking out a desired signal from the taken-in signal, and a phase adjuster for adjusting the phase of the signal waveform shaped by the waveform shaper AC plasma arc welding, characterized in that it comprises a level adjuster for adjusting the output of the phase adjuster to a magnitude for canceling a noise waveform, and a speaker for inputting an electrical output obtained through each of the devices. It is a silencer of the arc sound in.

[0007]

The present invention takes in a rectangular current waveform from a welding machine, shapes a waveform similar to the arc noise generated during the switching between the positive pole and the reverse pole, which is a peculiar high-pitched sound generation point, and outputs it from a speaker. By superimposing it on the arc noise, the phase is reversed by 180 ° at the position where the noise should be reduced, and only the peculiar treble is canceled, attenuated and eliminated. Similar waveforms are created with a built-in oscillator in the shaper, but can also be created from the actual arc sound collected by the microphone. In principle, the arc noise also changes depending on the normal welding conditions, but a shaping switch is incorporated with a switch for switching the oscillation waveform due to keying and keyhole welding, which have a particularly large effect. In addition, a plurality of speakers may be used to increase the area to be muted. A detailed description will be given below with reference to the drawings.

FIG. 1 is an overall block diagram showing the method and apparatus of the present invention. Noise sound wave 2 generated from welding arc 1
Contains ingredient 3, which is harmful to the human ear. The harmful component 3
The sound wave 4 similar to is generated by the speaker 5 so that when the sound pressure of the harmful component 3 becomes positive, it becomes negative by the same strength. When both sound waves overlap, the harmful component 3
Is canceled or canceled by the sound wave 4 from the speaker. The muted range 6 is the range of the angle θ of the sound wave from the speaker 5.

Since the noise sound wave 2 has a functional relationship with the current waveform 8 inside the AC plasma welding machine 7, the muffling output generator 9 takes in the current waveform 8 and performs various shaping, and the sound wave 4
Is a device for generating the above, and each function inside the device will be described later with reference to FIG. It should be noted that the muffling output here means an electrical output for muffling the sound before it is put into the speaker 5. At this time, the waveform to be taken is the current waveform 8, but the plasma arc voltage during welding may be input as the detection waveform. This is because the characteristic of the power source used for plasma welding is the drooping characteristic, and since the current and the voltage have a correlation, the input level may be adjusted and used as the input signal at the time of capturing. Furthermore, it is also possible to take out a current output command signal (not shown) for adjusting the output current inside the welding power source, carry out level adjustment, and then input this signal as a detection signal. In the figure, 10 is a plasma torch, 11 is a base material (workpiece), and 13 is a sound wave after being silenced.

The speaker mounting bracket 12 is the speaker 5
Is installed on the torch 10 in order to keep the distance d between the arc 1 and the source of the noise sound wave 2 constant. The phase of the noise sound wave 2 and the sound wave 4 for canceling the noise can be adjusted also by an electric circuit, but in order to adjust this, the position of the speaker is finely adjusted forward and backward using a feed screw or the like to form an arc. The distance d may be changed. This is convenient because it can be moved from a distance by a motor and can be adjusted while actually listening to the sound.

FIG. 2 is an internal block diagram of the muffling output generator 9, and FIG. 3 is an electric signal waveform and a sound wave waveform of each part of the present invention. In FIG. 2, the shaper 21 forms the basis of the current waveform corresponding to the sound wave 4 in FIG. 1 based on the current waveform taken from the AC plasma welding machine 7. That is, in FIG. 3, (a) is an alternating current waveform of the arc, and the frequency is, for example, 200 Hz (cycle 5 ms). Further, (b) is a waveform of a sound wave for noise elimination shown by reference numeral 4 in FIG. Figure (c) is a partial enlargement of the time axis of this,
There is a sine wave of about 16000 Hz (cycle 62.5 μs) at 80 μs when the arc current rectangular wave is switched between positive and negative.

As an auxiliary function (1), a knob 22 (FIG. 2) that can finely adjust the frequency of the waveform (c) in FIG. 3 by ± 10% of the basic value is provided. In addition, as an auxiliary function (2), the welding condition is keyed and keyhole welding is performed.
A switch 23 capable of switching the frequency of (c) is provided. As the auxiliary function (3), the sound pickup microphone 24 (FIG. 2) is used in consideration of the case where the waveform of FIG. 3 (c) is arranged not only by the internal oscillator but also the actual noise sound wave 2 (FIG. 1). The terminal 25 is provided.

The basic waveform from the shaper 21 is sent to the phase shifter 26, and the wave height is adjusted to the position where the sound wave 4 similar to the harmful component cancels the harmful sound wave 3. Therefore, a phase adjusting function 27 for adjusting the phase according to the distance between the arc 1 and the speaker 5 is provided. That is, the wavelength of the rectangular wave of the arc is 1 m75 cm at a sound velocity of 350 m / s when the frequency is 200 Hz, and the position of the arc and the speaker is 3
If they are separated by 0 cm, the phase angle shifts by about 62 degrees. Therefore, it is necessary to adjust the phase in order to match the position of the pulsed wave having the width of 80 μs shown in FIG. The switching of the positive and negative phases of the pulsed wave may be performed by connecting the terminals of the speaker in reverse, or by using a phase shifter.

The level adjuster 28 shown in FIG.
A speaker driver having a positive electrode height adjustment knob 29, a reverse pole height adjustment knob 30, and a total level adjustment knob 31 of the waveform of (c). In this way, the noise sound wave shown in FIG. 3 (d) is canceled by the noise eliminating sound wave of FIG.

[0015]

EXAMPLE The method of eliminating arc noise in AC plasma welding according to the present invention was applied to measure the noise reduction effect. The welding target is flat plate butt welding of an Al plate having a thickness of 5 mm, and frequency 2
Keyhole welding was performed with a square wave alternating current of 00 Hz and a positive electrode current of 250 A and a reverse polarity current of 250 A. The arc length is 5 mm. The speakers are arranged as shown in FIG. 1, and the distance d between the arc and the speaker is 30 cm.
Table 1 shows the noise levels at the distances of 1 m, 2 m, and 3 m from the arc on the extension of the line connecting the arc and the speaker. For comparison, Table 1 also shows the result of measuring the noise at the same position as the above without producing sound from the speaker.

[0016]

[Table 1]

When the device of the present invention is used, noise of 95 dB is 6 at a distance of 1 m from the arc when the device is not used.
It becomes 0 dB and is attenuated by 30 dB or more. Further, in the sound deadening area 6 in FIG. 1, θ was obtained at 30 degrees or more. 95d
B is a noise generated when a large truck is running or generated by a pop music band, 60 dB is a noise of daily conversation in an office, and a DC plasma welding arc sound is about 60 dB.

[0018]

According to the present invention, an operator performing AC plasma welding does not need to use earplugs. The only noise that can be attenuated is the harmful arc sound, and other signal sounds can be heard by humans, unlike when earplugs are used, thus improving work efficiency and safety.

[Brief description of drawings]

FIG. 1 is an overall block diagram showing a method and apparatus of the present invention.

FIG. 2 is an internal configuration diagram of the muffling output generator.

FIG. 3 is an electric signal waveform and a sound wave waveform of each part of the apparatus, where (a) is an alternating current waveform, (b) is a sound wave of reference numeral 4 in FIG. 1, (c) is an enlargement of 80 μs in (b), d) is Figure 1
The noise sound wave of reference numeral 2 and (e) the sound wave of reference numeral 13 in FIG.

[Explanation of symbols]

 1 Arc 2 Noise Sound wave 3 Harmful component 4 Sound wave similar to harmful component 5 Speaker 6 Range of silence 7 AC plasma welder 8 Current waveform 9 Silence output generator 10 Torch 11 Base metal 12 Speaker mounting bracket 13 After silenced Sound wave 21 Shaper 22 Frequency knob 23 Frequency selector switch 24 Sound collecting microphone 25 Terminal 26 Phase shifter 27 Phase adjustment function 28 Level adjuster 29 Positive pole height adjustment knob 30 Reverse pole height adjustment knob 31 All level adjustment knob

Claims (3)

[Claims] Claim: What is claimed is: 1. By detecting a plasma arc current waveform during welding in AC plasma arc welding, and by generating a sound wave having an opposite phase at a position where noise and noise generated by the plasma arc should be reduced, both sound waves are generated. A method of eliminating arc sound in AC plasma arc welding, which comprises attenuating the arc. 2. A two-sided sound wave by detecting a plasma arc voltage waveform during welding of AC plasma arc welding and generating a sound wave having an opposite phase at a position where noise and noise generated by the plasma arc should be reduced. A method of eliminating arc sound in AC plasma arc welding, which comprises attenuating the arc. 3. A detector for taking in a signal synchronized with a plasma arc sound, a waveform shaper for taking out a target signal from the taken-in signal, and a phase adjuster for adjusting the phase of the signal waveform shaped by the waveform shaper. AC plasma arc welding, characterized in that it comprises a level adjuster for adjusting the output of the phase adjuster to a magnitude for canceling a noise waveform, and a speaker for inputting an electrical output obtained through each of the devices. Silencer for arc sounds in Japan.