JP3443413B2 - Output control method of AC TIG welding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC TIG welding output control method for improving welding performance such as arc concentration by changing an AC frequency.

[0002]

2. Description of the Related Art The AC TIG welding method is widely used as a high quality welding method for aluminum and aluminum alloys (hereinafter referred to as aluminum alloys and the like). In a welding power supply device used for recent AC TIG welding, constant current control is generally performed by inverter control. Therefore, the electrode minus current Ien and the electrode plus current Iep, which are equal to the current control setting signal Isc which is the target value of the constant current control, are conducted.

FIG. 1 is a current waveform diagram of general AC TIG welding. The same figure (A) shows the time change of the welding current Iw, and the same figure (B) shows the time change of the current control setting signal Isc. In the same figure (A), the portion above 0 [A] has the negative polarity of the electrode and the negative electrode current Ien is applied,
The portion below [A] has an electrode plus polarity, and an electrode plus current Iep is conducted. Hereinafter, description will be given with reference to FIG.

Time period t1 to t2 (electrode minus rise period Tnu) At time t1, when the current control setting signal Isc = Ip is changed and the polarity is switched as shown in FIG. As shown in A), the state is switched from the state in which the polarity switching current Ic with the positive polarity of the electrode is conducted to the state in which the polarity switching current Ic with the negative polarity of the electrode is conducted. After that, the welding current Iw in the electrode minus rising period Tnu from time t1 to t2 has a slope and increases, and reaches a predetermined peak value Ip at time t2. Despite the current control setting signal Isc = Ip, the reason why the welding current Iw increases with a slope during this period is that the internal impedance of the reactor or the like inside the welding power source device and the external impedance of the welding cable or the like ( Hereinafter, it will be referred to as cable impedance and the like). Therefore, the time length of this period varies depending on the value of the cable impedance and the like, but is generally about 1 [ms]. The value of the polarity switching current Ic is generally 5
It is set to about 0 [A].

Time period from t2 to t3 (electrode minus peak period Tnp) As shown in FIG. 7B, current control setting signal Isc = Ip
Therefore, as shown in (A) of FIG.
~ T3 Electrode minus peak welding period Tnp welding current I
w becomes equal to the peak value Ip.

Period from time t3 to t4 (electrode minus falling period Tnd) At time t3, when the current control setting signal Isc = Ic is changed as shown in FIG. 7B, as shown in FIG. In addition, the welding current Iw decreases with a slope from the peak value Ip due to the influence of the above-described cable impedance, and reaches the substantially polarity switching current Ic at time t4. The time length of the electrode minus falling period Tnd between the times t3 and t4 is set to about 1 [ms]. Therefore, the value of the welding current Iw at time t4 may be a little larger than the polarity switching current Ic depending on the value of the cable impedance described above. As described above, the reason why the welding current Iw is reduced to the polarity switching current Ic to switch the polarity is that the transistor for polarity switching, which will be described later with reference to FIG. This is to prevent destruction.

Period from Time t4 to t5 (Electrode Plus Rising Period Tpu) At time t4, when the current control setting signal Isc = Ip is changed and the polarity is switched as shown in FIG. As shown in A), the state in which the polarity switching current Ic in the negative polarity of the electrode is conducted is switched to the state in which the polarity switching current Ic in the positive polarity of the electrode is conducted. After that, the welding current Iw during the electrode plus rising period Tpu from time t4 to t5 has a slope and increases due to the influence of the above-described cable impedance, and reaches the peak value Ip at time t5. The time length of the electrode plus rising period Tpu varies depending on the value of the cable impedance or the like as in the case of the above item, but is usually about 1 [ms].

Period from time t5 to t6 (electrode plus peak period Tpp) As shown in FIG. 7B, current control setting signal Isc = Ip
Since it remains as it is, as shown in FIG.
Welding current Iw during the electrode plus peak period Tpp from to t6
Becomes equal to the peak value Ip.

Period from time t6 to t7 (electrode plus falling period Tpd) At time t6, when the current control setting signal Isc = Ic is changed as shown in FIG. 7B, as shown in FIG. In addition, the welding current Iw decreases with a slope from the peak value Ip due to the influence of the cable impedance described above, and reaches the substantially polarity switching current Ic at time t7. The time length of the electrode plus falling period Tpd from time t6 to t7 is set to about 1 [ms]. Therefore, time t
The value of the welding current Iw at time 7 may be a little larger than the polarity switching current Ic depending on the value of the cable impedance described above. As described above, the reason why the welding current Iw is reduced to the polarity switching current Ic to switch the polarity is the same as in the above item.

The above periods (1) to (3) are repeated as one cycle. The frequency of this repetition is the AC frequency Fs [Hz]
Becomes As described above, the electrode negative current Ien and the electrode positive current Iep are substantially trapezoidal current waveforms having a rising and falling slope, and the peak values Ip of both current waveforms are equal. The TIG welding method in which alternating current is applied is called the balanced trapezoidal wave AC TIG welding method.

FIG. 2 is a block diagram of a welding power source device for carrying out the above-mentioned balanced trapezoidal wave AC TIG welding method. Hereinafter, each circuit block will be described with reference to FIG.

The commercial power source AC is an input power source for the welding power source device, and usually three-phase 200/220 [V] is often used. The output control circuit INV, whose internal circuit is not shown, has a primary side rectifying circuit for rectifying the commercial power source AC, a smoothing circuit for smoothing the rectified rippled voltage, and a smoothed direct current. Formed from an inverter circuit that converts a voltage into a high frequency alternating current, a drive circuit of a plurality of sets of power transistors that form the inverter circuit, and a PWM control circuit that performs PWM control of the above-mentioned inverter circuit according to a current error amplification signal Ei described later. To be done.

The high frequency transformer INT steps down the high frequency alternating current to a voltage value suitable for an arc load. The secondary side rectifiers D2a to D2d rectify the stepped down high frequency alternating current into direct current. The polarity switching drive circuit DR uses a polarity switching signal Snp, which will be described later, as an input signal, and the polarity switching signal Snp is Hi.
At gh level, electrode negative polarity drive signal Ndr
Is output (High level) and the polarity switching signal Snp is Lo.
At the w level, the electrode plus polarity drive signal Pdr is output (High level). Therefore, when the electrode negative polarity drive signal Ndr is output, the electrode positive polarity drive signal Pdr is not output, and conversely, when the electrode negative polarity drive signal Ndr is not output, the electrode positive polarity drive signal Pdr is output. , Which are logically opposite to each other. The electrode minus polarity transistor NTR becomes conductive when the above electrode minus polarity drive signal Ndr is output, and the output of the welding power source device has the electrode minus polarity. On the other hand, the electrode positive polarity transistor PTR becomes conductive when the electrode positive polarity drive signal Pd is output, and the output of the welding power source device has the electrode positive polarity.

The reactor WL smoothes a rippled output for energizing the negative electrode polarity transistor NTR or the positive electrode polarity transistor PTR and supplies it to the arc 3. The negative electrode current I shown in FIG.
en is the work piece 2 → non-consumable electrode 1 → NTR → WL → D2c
Or, energize along the route of D2d. On the other hand, electrode plus current Iep
Is energized in the route of D2a or D2b → PTR → WL → non-consumable electrode 1 → weld object 2. The non-consumable electrode 1 is attached to the tip of the welding torch 4, and an arc 3 is generated between the non-consumable electrode 1 and the welding target 2.

The AC frequency setting circuit FS outputs an AC frequency setting signal Fs having a desired value. Polarity ratio setting circuit RS
Outputs a polarity ratio setting signal Rs having a desired value. The period calculation circuit CT receives the AC frequency setting signal Fs and the polarity ratio setting signal Rs as described above, and calculates and outputs the electrode minus peak value setting period setting signal Tns and the electrode plus peak value setting period setting signal Tps. The calculation method is as follows. The polarity ratio setting signal Rs includes the AC frequency setting signal Fs [Hz] and the electrode minus period Ten [s].
Is defined by Rs = Ten · Fs Equation (1) Further, the electrode minus period Ten is, as described above with reference to FIG. 1, the electrode minus peak value setting period setting signal Tns [s].
And the electrode minus fall period Tnd [s]. Ten = Tns + Tnd Expression (2) When the above Expression (2) is substituted into the above Expression (1) and arranged, the following Expression is obtained. Tns = Rs / Fs-Tnd Formula (3) Here, since the electrode minus fall period Tnd is a predetermined constant, the AC frequency setting signal F is calculated by the above (3).
The electrode minus peak value setting period setting signal Tns can be calculated by inputting s and the polarity ratio setting signal Rs. Similarly, the electrode plus peak value setting period setting signal Tps
[S] is given by the following formula. Tps = (1−Rs) / Fs−Tpd (4) Equation (4) Here, since the electrode plus falling period Tpd is a predetermined constant, the AC frequency setting signal Fs is calculated by the above (4).
Also, the electrode plus peak value setting period setting signal Tps can be calculated by inputting the polarity ratio setting signal Rs.

In the electrode minus peak value setting period timer circuit TN, the electrode plus falling period signal Tpd described later is Lo.
When it changes to the w level, from that point on, the period H determined by the electrode minus peak value setting period setting signal Tns
An electrode minus peak value setting period signal Tn that is at the high level is output. Electrode minus falling period timer circuit T
ND is the above-mentioned electrode minus peak value setting period signal Tn
Changes to the Low level, it outputs the electrode minus falling period signal Tnd which is at the High level for a predetermined period from that point. The electrode plus peak value setting period timer circuit TP is configured such that the electrode minus falling period signal Tnd is L.
When it changes to the ow level, from that point on, the period H determined by the electrode plus peak value setting period setting signal Tps
High level electrode plus peak value setting period signal T
Output p. Electrode plus falling period timer circuit TPD
Indicates that the electrode plus peak value setting period signal Tp is Lo.
When the level changes to w level, a predetermined period H from that point
The electrode plus falling period signal Tpd which becomes the high level is output.

The first OR circuit OR1 performs a logical sum of the electrode minus peak value setting period signal Tn and the electrode plus peak value setting period signal Tp, and is a current setting switching signal Si which is a high level signal for both periods. Is output. During the period in which the current setting switching signal Si is at the high level, as shown in FIG. 1B described above, the time t1 to t3 and the time t4 to t6 when the current control setting signal Isc = Ip is satisfied.
It is both periods.

The peak value setting circuit IP outputs a peak value setting signal Ip having a desired value. Polarity switching current setting circuit IC
Outputs the polarity switching current setting signal Ic having a desired value. The current setting switching circuit SI is switched to the side a when the above current setting switching signal Si is at the high level, and outputs the above peak value setting signal Ip as the current control setting signal Isc, and the above current setting switching signal Si. Is low level, the polarity switching current setting signal Ic is output as the current control setting signal Isc. The current detection circuit ID detects the welding current Iw and outputs a full-wave rectified current detection signal Id. The current error amplification circuit EI amplifies the error between the current control setting signal Isc and the current detection signal Id to obtain the current error amplification signal E.
Output i. As described above, the output control circuit INV
Performs output control according to the current error amplified signal Ei.

The second OR circuit OR2 ORs the electrode minus peak value setting period signal Tn and the electrode minus falling period signal Tnd, and outputs a polarity switching signal Snp. Therefore, the polarity switching signal Snp is at the high level during the electrode minus period Ten and is at the low level during the electrode plus period Tep.

By the above-mentioned operation, the polarity switching signal Snp
Is high level, a welding current Iw equal to the current control setting signal Isc is supplied with the negative polarity of the electrode, and a welding current Iw equal to the current control setting signal Isc with positive polarity of the electrode is supplied when the polarity switching signal Snp is low level. To do. Further, at the time of welding, the peak value setting signal Ip, the AC frequency setting signal Fs, and the polarity ratio setting signal Rs described above are set to appropriate values in accordance with the material, plate thickness, joint shape, etc. of the object to be welded. To do.

FIG. 3 is a timing chart of each signal in the above-mentioned conventional welding power source device. The same figure (A) shows the time change of the welding current Iw, the same figure (B) shows the time change of the current control setting signal Isc, and the same figure (C) shows the time change of the electrode minus peak value setting period signal Tn. The same figure (D) shows the time change of the electrode minus fall period signal Tnd, the same figure (E) shows the time change of the electrode plus peak value setting period signal Tp, and the same figure (F) shows the electrode plus rise period. The time change of the down period signal Tpd is shown, (G) shows the time change of the current setting switching signal Si, and (H) shows the time change of the polarity switching signal Snp. 1A and 1B are the same as FIG. 1 described above. Hereinafter, description will be given with reference to FIG.

Period from Time t1 to t3 (Electrode Minus Peak Value Setting Period Tn) At time t1, when the electrode minus peak value setting period signal Tn changes to High level as shown in FIG. As shown in H), the polarity switching signal Snp is at the high level, so that the output of the welding power source device has a negative electrode polarity. At the same time, the current setting switching signal Si becomes High level as shown in (G) of the figure, so that the current control setting signal Isc =
Ip. As a result, as described above in the description of FIG. 1, the electrode minus current Ien shown in FIG.

Period from Time t3 to t4 (Electrode Minus Fall Period Tnd) At time t3, the electrode minus fall period signal Tnd changes to High level as shown in FIG. ), The polarity switching signal Snp is Hi.
Since it remains at the gh level, the output remains at the electrode minus polarity. At the same time, the current setting switching signal Si becomes Low level as shown in FIG. 7G, so that the current control setting signal Isc = Ic as shown in FIG. As a result, as described above in the description of FIG. 1, the electrode minus current Ien shown in FIG. 1 (A) decreases with a slope from the peak value Ip and becomes substantially equal to the polarity switching current Ic.

Period from Time t4 to t6 (Electrode Plus Peak Value Setting Period Tp) At time t4, when the electrode plus peak value setting period signal Tp changes to High level as shown in FIG. As shown in H), the polarity switching signal Snp is L
Since it becomes the ow level, the output becomes the electrode plus polarity.
At the same time, as shown in FIG.
Since i goes to the high level, the current control setting signal Isc = Ip, as shown in FIG. As a result, as described above in the description of FIG. 1, the electrode plus current Iep shown in FIG. 9A having a rising slope is energized.

Period from Time t6 to t7 (Electrode Plus Fall Period Tpd) At time t6, the electrode plus fall period signal Tpd changes to High level as shown in FIG.
As shown in FIG. 3H, the polarity switching signal Snp remains at the Low level, so the output remains at the electrode plus polarity. At the same time, the current setting switching signal Si becomes Low level as shown in FIG. 7G, so that the current control setting signal Isc = Ic as shown in FIG. As a result, as described above in the description of FIG. 1, the electrode plus current Iep shown in FIG. 1A decreases with a slope from the peak value Ip and becomes substantially equal to the polarity switching current Ic.

[0026]

In the above-mentioned balanced trapezoidal wave AC TIG welding, the AC frequency Fs has an appropriate value within the range of about 50 to 200 [Hz] depending on the plate thickness of the work piece, the joint shape, and the like. Is set. When the AC frequency Fs has a low frequency, the spread of the arc becomes large, and conversely, when the AC frequency Fs has a high frequency, the spread of the arc becomes small and the concentration of the arc improves. Therefore, the plate thickness of the work piece is several [m
When it is a medium or thick plate above m], an arc with a large spread will improve welding workability and welding quality.
The AC frequency Fs is often set to a low value within the above range. On the other hand, when the plate thickness of the work piece is less than several [mm], the average value of the welding current becomes small and the arc spread fluctuates irregularly, which tends to cause an unstable state. For this reason, when welding a thin plate, the AC frequency Fs is set to a high value to improve the concentration of the arc and suppress the above-mentioned unstable state, thereby ensuring good welding workability and welding quality. . However, in the balanced trapezoidal wave AC TIG welding, when the AC frequency Fs is changed for the above purpose, there are the following problems to be solved.

FIG. 4 is a current waveform diagram when the AC frequency Fs is low and high in the balanced trapezoidal wave AC TIG welding. The same figure (A) is AC frequency Fs = 50 [Hz]
In the figure, (B) shows the AC frequency Fs = 100.
It shows the case of [Hz]. FIG. 1A shows the above-mentioned FIG.
It has the same waveform as (A). Hereinafter, description will be given with reference to FIG.

As shown in FIGS. 9A and 9B, even if the AC frequency Fs changes, the electrode minus rise period Tn
The time lengths of u, the electrode minus fall period Tnd, the electrode plus rise period Tpu, and the electrode plus fall period Tpd remain substantially the same value and do not change. For this reason, the welding current average value Iav obtained by full-wave rectifying and averaging the welding current Iw decreases in inverse proportion to the increase in the AC frequency Fs.

As previously mentioned in the description of FIG. 1, Tnu =
Since it can be considered that Tnd = Tpu = Tpd, if the value is taken as the inclination time Ts, the welding current average value Iav of the welding current waveforms shown in FIGS. 9A and 9B can be expressed by the following equation. Iav = (1-2 · Ts · Fs) · (Ip−Ic) + Ic (5) In the above formula, even if the AC frequency Fs changes, the tilt time T
Since s, the peak value Ip, and the polarity switching current Ic are constant values, the welding current average value Iav increases when the AC frequency Fs increases.
Becomes smaller. For example, the tilt time Ts = 1 [ms], the peak value p = 150 [A], and the polarity switching current Ic = 50.
Substituting [A] into equation (5) yields the following equation. Iav = 150−0.2 · Fs Equation (6) In the above equation, AC frequency Fs = 50 to 200 [Hz]
, The welding current average value Iav
= 140 to 110 [A]. That is,
In balanced trapezoidal wave AC TIG welding, the welding current average value Iav decreases as the AC frequency Fs increases.

By the way, it is an essential condition for ensuring good welding quality that the penetration depth is an appropriate value depending on the plate thickness, joint shape, etc. of the object to be welded. Generally, the welding current average value Iav and the penetration depth are in a substantially proportional relationship. As described above, when the AC frequency Fs is changed to improve the arc concentration, the welding current average value I is correspondingly changed.
Since av also changes, the penetration depth changes and deviates from the proper value. Therefore, the welding operator needs to readjust the peak value Ip so that the penetration depth becomes an appropriate value every time the setting of the AC frequency Fs is changed.

FIG. 5 is a diagram illustrating changes in the penetration depth when the AC frequency Fs changes. In the figure, an aluminum alloy is used for the object to be welded, and the peak value Ip = 150 [A] and the inclination time Ts = as in the case of the above formula (6).
1 [ms] and the polarity switching current Ic = 50 [A], and the AC frequency Fs shown on the horizontal axis is 50 to 200 [Hz].
The changes in the penetration depth shown on the vertical axis when changing in the range of are shown. Welding was performed by bead-on-plate welding.

The welding current average value Iav when the AC frequency Fs = 50 [Hz] is 140 [A] as described above, and the penetration depth at that time is about 3 as shown in FIG.
[Mm]. The welding current average value Iav decreases as the AC frequency Fs increases, and as is clear from the figure,
The penetration depth becomes shallow. And AC frequency Fs = 20
The welding current average value Iav at 0 [Hz] is 110 [A].
And the penetration depth becomes shallow to 1.6 [mm]. As described above, in the conventional technique, when the AC frequency Fs is increased, the penetration depth may be largely changed and the welding quality may be poor.

Therefore, in the present invention, in balanced trapezoidal wave AC TIG welding, the welding current average is maintained even if the AC frequency Fs changes, while the effect of improving the arc concentration by increasing the AC frequency Fs is maintained. A value control method for AC TIG welding is provided in which the value Iav does not change, and as a result, the penetration depth does not change.

[0034]

According to the invention of claim 1 at the time of filing, as shown in FIG. 6, a period Tnu and a peak value during which an increasing current is applied with a slope after switching to the negative polarity of the electrode. After reaching Ip, during a predetermined electrode minus period Ten formed from a period Tnp in which a current having a peak value Ip is supplied and a period Tnd in which a current having a slope and decreasing from the peak value Ip is supplied. After the electrode negative current Ien of a substantially trapezoidal wave is supplied, and subsequently the electrode positive polarity is switched, an increasing current having a slope is supplied for a period Tpu and after reaching the peak value Ip of the same value as above. The period Tpp during which the current having the peak value Ip is applied and the peak value Ip
During a predetermined electrode plus period Tep, which is formed from a period Tpd in which a current that has a slope and decreases, is applied, a substantially trapezoidal electrode plus current Iep is applied, and the electrode minus period Ten and the electrode plus period In an output control method of balanced trapezoidal wave AC TIG welding in which Tep is one cycle and is repeated at a frequency of a preset AC frequency set value Fs, the electrode minus current Ien and the electrode plus current Iep are full-wave rectified and averaged. This is an output control method for AC TIG welding in which the peak value Ip is increased or decreased so that the average current value Iav becomes substantially equal to the predetermined current setting value Is.

The invention of claim 2 at the time of filing is shown in FIGS.
As shown in FIG. 5, after switching to the negative polarity of the electrode, a period Tnu in which a current having an inclination and an increasing current is passed and a period Tnp in which a current of the peak value Ip is passed after reaching the peak value Ip and the above-mentioned peak value During a predetermined electrode minus period Ten, which is formed from a period Tnd in which a current that has a slope and decreases from Ip is supplied, the electrode minus current I of a substantially trapezoidal wave is formed.
After en is energized and then the electrode is switched to the positive polarity, a period Tpu in which an increasing current having a slope is energized and a peak value Ip of the same value as above is reached, and then the current of this peak value Ip is energized. During the predetermined electrode plus period Tep formed from the period Tpp and the period Tpd in which a current having a slope is reduced from the peak value Ip, a substantially trapezoidal electrode plus current Iep is conducted and the electrode is In the output control method of balanced trapezoidal wave AC TIG welding in which the minus period Ten and the electrode plus period Tep are set as one cycle and repeated at a frequency of a preset AC frequency set value Fs, the AC frequency set value Fs and the preset current set value are used. With Is as input,
The electrode minus current Ien and the electrode plus current Iep
The peak value Ip is calculated by a predetermined peak value calculation function Ip = f (Fs, Is) so that the welding current average value Iav obtained by full-wave rectifying and averaging is substantially equal to the current setting value Is. This is an output control method of AC TIG welding to be set.

The invention of claim 3 at the time of filing is as shown in FIG. 9 and FIG.
As shown in 0, the AC frequency setting value Fs and the predetermined polarity ratio setting value Rs are input, and the electrode minus period Ten
= (1 / Fs) .Rs and electrode plus period Tep = (1 /
Fs) · (1−Rs) is set by the above calculation, the AC frequency set value Fs and the polarity ratio set value Rs are input, and the AC surface frequency set value Fs is changed and the surface of the workpiece to be welded 3. The polarity ratio setting value Rs is corrected and set by a predetermined polarity ratio correction function f (Fs, Rs) so that the cleaning width Wc of the above is substantially constant without changing. The output control method for AC TIG welding described in 1.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the inventions of Examples 1 to 4 will be described as embodiments of the present invention. [Embodiment 1] The invention of embodiment 1 described below corresponds to the invention of claim 1 at the time of filing. The invention of the first embodiment increases or decreases the peak value Ip so that the welding current average value Iav obtained by full-wave rectifying and averaging the electrode negative current Ien and the electrode positive current Iep becomes substantially equal to the predetermined current setting value Is. This is an output control method for balanced trapezoidal wave AC TIG welding. Hereinafter, the invention of the first embodiment will be described with reference to FIG.

FIG. 6 is a block diagram of the welding power source device of the first embodiment. In the figure, the same circuit blocks as those in FIG. 2 described above are designated by the same reference numerals, and their description will be omitted. Hereinafter, the current averaging circuit AV, the current setting circuit IS, the current average value error amplification circuit EAV, and the peak value control setting circuit IPC, which are circuit blocks indicated by dotted lines different from FIG. 2, will be described.

The current averaging circuit AV outputs a welding current average value signal Iav obtained by averaging the full-wave rectified current detection signal Id of the AC welding current Iw. Current setting circuit IS
Outputs the current setting signal Is of a desired value. The average current value error amplifying circuit EAV uses the above welding current average value signal Iav.
The error between the current setting signal Is and the current setting signal Is is amplified, and the peak value correction signal ΔIp is output. Peak value control setting circuit IPC
Receives the above-mentioned peak value correction signal ΔIp and outputs a peak value control setting signal Ipc. By the above-described operation, the peak value Ip is increased or decreased by modifying the peak value control setting signal Ipc so that the welding current average value signal Iav and the current setting signal Is are substantially equal.

Therefore, in the invention of the first embodiment, even if the AC frequency Fs changes, the peak value Ip is controlled so that the welding current average value Iav becomes equal to the preset current setting value Is, so that the welding current is The average value Iav does not change. Therefore, even if the AC frequency Fs changes, the penetration depth remains at an appropriate value and does not change.

[Embodiment 2] The invention of embodiment 2 described below corresponds to the invention of claim 2 as filed. In the invention of the second embodiment, the welding current average value Iav obtained by full-wave rectifying the electrode minus current Ien and the electrode plus current Iep with the AC frequency setting value Fs and the predetermined current setting value Is as input is the above current. This is an output control method for AC TIG welding in which the peak value Ip is set according to a peak value calculation function Ip = f (Fs, Is) that is predetermined so as to be substantially equal to the set value Is. Hereinafter, the invention of the second embodiment will be described with reference to FIG. 7.

FIG. 7 is a block diagram of the welding power source device of the second embodiment. In the figure, the same circuit blocks as those in FIG. 2 described above are designated by the same reference numerals, and their description will be omitted. Hereinafter, the current setting circuit IS and the peak value calculation circuit IPO, which are circuit blocks indicated by a dotted line different from FIG. 2, will be described.

The current setting circuit IS outputs a current setting signal Is of a desired value. The peak value calculation circuit IPO receives the AC frequency setting signal Fs and the above current setting signal Is as input, and a predetermined peak value calculation function Ipc = f (Fs, I
s) is calculated and the peak value control setting signal Ipc is output. The above peak value calculation function Ipc = f (Fs, Is)
Is defined in advance so that the welding current average value Iav is substantially equal to the current setting signal Is. An example of this peak value calculation function is shown below.

First Example of Peak Value Calculation Function As described above, the welding current average value Iav and the AC frequency Fs
And the relationship with the peak value Ip are given by the equation (5), and the equation is transformed into the following equation. Ip = (Iav-Ic) / (1-2.Ts.Fs) + Ic (7) Formula Here, the ramp time Ts and the polarity switching current Ic are constants. In the above equation, the peak value Ip is replaced with the peak value control setting signal Ipc, and the welding current average value Iav is replaced with the current setting signal Ipc.
Substituting for s gives: Ipc = (Is−Ic) / (1-2 · Ts · Fs) + Ic (8) By defining the above equation as the peak value calculation function Ipc = f (Fs, Is), the AC frequency Fs changes. Also,
The welding current average value Iav does not change because it is always equal to the current setting value Is.

Second Example of Peak Value Calculation Function In the above item, equation (8) calculated assuming that the current waveform in balanced trapezoidal wave AC TIG welding is the standard waveform described above with reference to FIG. Based on this, a peak value calculation function was defined. However, when the AC frequency changes, the values of the above-described cable impedance and the like change, so that the slopes of the rising and falling of the current waveform change. For this reason, a difference occurs between the actual current waveform and the standard waveform described above, and an error occurs in the calculation by the equation (8). Therefore, the second method is a method of experimentally calculating the peak value calculation function, as shown below.

FIG. 8 is a diagram showing an example of a peak value calculation function calculated by experiment. This figure shows the welding current average value Iav during welding when the AC frequency setting signal Fs is changed.
So that the peak value control setting signal Ipc becomes 150 [A].
AC frequency setting signal F shown on the horizontal axis when changing
The relationship between s and the peak value control setting signal Ipc shown on the vertical axis is shown. In the same figure, the dotted line shows the peak value control setting signal Ipc calculated by the above equation (8), and the practice shows the peak value calculation function f1 (Fs, Is) calculated by the experiment. Even when the current setting signal Is is other than 150 [A], the peak value calculation function f is calculated for each current setting signal Is.
1, f2 ... fn are calculated in advance by experiments.

[Example 3] In AC TIG welding of an aluminum alloy or the like, it is necessary to remove (clean) the oxide film existing on the surface of the object to be welded. It is important to secure a cleaning width Wc [mm] wider than the bead width Wb [mm] during welding in order to obtain good welding quality without welding defects. That is, when the cleaning width Wc is narrower than the bead width Wb, or when the cleaning width Wc is not sufficient compared to the bead width Wb, an oxide film is caught in the bead after welding, resulting in a welding defect. May be. In AC TIG welding, cathode spots are formed on the surface of the object to be welded during the electrode plus period, and the oxide film is removed by the formation of the cathode spots. As described above, the smaller the polarity ratio Rs, the larger the ratio of the electrode plus period to the entire period.
The period during which the above-mentioned removing action works becomes longer, and the cleaning width Wc becomes wider. Therefore, in AC TIG welding, it is necessary to set the polarity ratio Rs to an appropriate value so that the cleaning width Wc is optimum according to the bead width Wb. The cleaning width Wc becomes narrower as the polarity ratio Rs becomes larger, and conversely the cleaning width Wc becomes smaller as the polarity ratio Rs becomes smaller.
c becomes wider.

However, even if the polarity ratio Rs is a constant value, the cleaning width Wc is proportional to the AC frequency Fs.
Is known to be narrower. Therefore, as described above, in order to improve the concentration of the arc, the AC frequency F
When s is increased, the cleaning width Wc becomes narrower accordingly, and welding defects are likely to occur. Therefore, the inventions of Example 3 and Example 4 described below have the effect of the inventions of Example 1 and Example 2 that the penetration depth does not change even if the AC frequency Fs changes. Then, the problem that the cleaning width Wc changes when the AC frequency Fs further changes is solved.

The invention of the third embodiment described below corresponds to the invention of claim 3 as filed. The third embodiment of the invention is the same as the first embodiment, except that the AC frequency set value Fs and the polarity ratio set value Rs are input to the AC frequency set value Fs.
Of the predetermined polarity ratio correction function f so that the cleaning width when welding is performed by changing
This is an output control method for AC TIG welding in which the polarity ratio set value Rs is corrected and set by (Fs, Rs). Hereinafter, the invention of the third embodiment will be described with reference to FIG.

FIG. 9 is a block diagram of the welding power source device of the third embodiment. In the figure, the same circuit blocks as those in FIG. 6 described above are designated by the same reference numerals, and the description thereof will be omitted. The polarity ratio control setting circuit RSC, which is a circuit block indicated by a dotted line different from FIG. 6, will be described below.

The polarity ratio control setting circuit RSC receives the AC frequency setting signal Fs and the polarity ratio setting signal Rs as input, and calculates a predetermined polarity ratio correction function f (Fs, Rs) to obtain the polarity ratio control setting signal Rsc. Is output. The polarity ratio correction function Rsc = f (Fs, Rs) is defined in advance so that the cleaning width of the surface of the workpiece is not changed even if the AC frequency Fs is changed. An example of this polarity ratio correction function is shown below. Rsc = Rs−K · (Fs−50) However, K is a constant and 50 ≦ Fs [Hz] ≦ 200. In the above equation, if K = 0.06 and Rs = 0.7, then Rsc = 0.7 when Fs = 50 [Hz] and Rsc = 0.61 when Fs = 200 [Hz]. . The value of the constant K is preset to an appropriate value within the range of about 0.01 to 0.1 depending on the current setting signal Is, the material of the workpiece, and the like.

As described above, in the invention of the third embodiment, in addition to the effect of the invention of the first embodiment, the polarity ratio Rs is corrected to an appropriate value in accordance with the change of the AC frequency Fs, so that the cleaning width is substantially. It will be constant.

[Fourth Embodiment] The invention of a fourth embodiment described below corresponds to the invention of claim 3 as filed. The fourth embodiment of the invention is the same as the second embodiment, except that the AC frequency set value F is
s and the polarity ratio set value Rs are input, and a predetermined polarity ratio correction function f (Fs, Rs) is set so that the cleaning width when the AC frequency set value Fs is changed and welded does not change. Is an output control method for AC TIG welding in which the polarity ratio set value Rs is corrected and set. Hereinafter, the invention of the fourth embodiment will be described with reference to FIG.

FIG. 10 is a block diagram of the welding power source device of the fourth embodiment. In the figure, the same circuit blocks as those in FIG. 7 described above are designated by the same reference numerals, and the description thereof will be omitted. In the figure, only the polarity ratio control setting circuit RSC shown by the dotted line is different from FIG. The polarity ratio control setting circuit RSC has been described in the section of the description of FIG. 9, and thus the description thereof is omitted here. Therefore, in the invention of the fourth embodiment, when the setting of the AC frequency setting signal Fs changes, the peak value control circuit IPO changes the peak value control setting signal Ipc so that the welding current average value Iav becomes substantially equal to the current setting signal Is. In addition to being corrected, the polarity ratio control setting circuit RSC corrects the polarity ratio control setting signal Rsc so that the cleaning width of the surface of the workpiece is not changed and becomes substantially constant.

As described above, in the invention of the fourth embodiment, in addition to the effect of the invention of the second embodiment, the polarity ratio Rs is corrected to an appropriate value in accordance with the change of the AC frequency Fs, so that the cleaning width is substantially. It will be constant.

[Effect] FIG. 11 shows an AC frequency Fs (horizontal axis) for showing the effect of the present invention in comparison with the above-mentioned FIG.
It is a figure which shows the change of penetration depth (vertical axis) when changes. The welding conditions in the figure are the same as in FIG. 5, the dotted line shows the change in penetration depth in the case of the prior art of FIG. 5, and the solid line shows the change in penetration depth in the case of the present invention. As is clear from the figure, the AC frequency F
When s changes in the range of 50 to 200 [Hz], the penetration depth changes in the range of 3 to 1.6 [mm] in the prior art.
On the other hand, in the present invention, the fluctuation range of the penetration depth is 3 to
It becomes considerably small at 2.5 [mm]. Therefore, even if the AC frequency Fs is changed, the penetration depth does not change and remains at an appropriate value.

FIG. 12 shows changes in the bead width Wb and the cleaning width Wc (vertical axis) when the AC frequency Fs (horizontal axis) changes to show the effects of the inventions of the third and fourth embodiments. It is a figure. The welding conditions in the figure are the same as those in FIG. 5 described above. In the figure, the dotted line shows the case of the prior art and the solid line shows the case of the present invention. As is clear from the figure, the AC frequency Fs is 50 to 200 [H
The bead width Wb does not change much in the prior art and the present invention even when it changes in the range of z]. On the other hand, the cleaning width Wc changes largely in the conventional technique, but it hardly changes in the present invention and is substantially constant. Therefore, even if the AC frequency Fs is changed, the cleaning width Wc with respect to the bead width Wb does not change, so that good welding quality can be obtained.

[0058]

According to the output control method of the AC TIG welding of the present invention, the AC frequency is adjusted in order to make the arc concentration, welding workability, etc. in a good state in accordance with the plate thickness of the work piece, the joint shape, etc. Even if it is changed, the welding current average value does not change, and therefore the penetration depth remains the proper value and does not change. Therefore, good welding quality can always be obtained. further,
In addition to the above effects, in the inventions of the third and fourth embodiments, the polarity ratio is corrected according to the change of the AC frequency, so that the cleaning width can be maintained at an appropriate value, and a good welding quality can always be obtained. Obtainable.

[Brief description of drawings]

FIG. 1 Current waveform diagram of general AC TIG welding

FIG. 2 is a block diagram of a conventional AC TIG welding power supply device.

FIG. 3 is a timing chart of each signal in the conventional welding power supply device.

FIG. 4 is a current waveform diagram when the AC frequency Fs is low and high.

FIG. 5 is a diagram illustrating a change in penetration depth when the AC frequency Fs changes.

FIG. 6 is a block diagram of the welding power supply device according to the first embodiment.

FIG. 7 is a block diagram of a welding power supply device according to a second embodiment.

FIG. 8 is a diagram illustrating a peak value calculation function calculated by an experiment.

FIG. 9 is a block diagram of a welding power supply device according to a third embodiment.

FIG. 10 is a block diagram of a welding power supply device according to a fourth embodiment.

FIG. 11 is a relationship diagram between the AC frequency Fs and the penetration depth showing the effect of the present invention.

FIG. 12 is a graph showing the relationship between the AC frequency Fs, the bead width Wb, and the cleaning width Wc showing the effect of the present invention.

[Explanation of symbols]

1 Non-consumable electrode 2 Objects to be welded 3 arc 4 welding torch AC commercial power supply AV current averaging circuit CT period calculation circuit D2a ~ D2d Secondary side rectifier DR polarity switching drive circuit EAV current average value error amplification circuit EI current error amplifier circuit Ei Current error amplification signal FS AC frequency setting circuit Fs AC frequency (set value / signal) Iav welding current average value (signal) IC polarity switching current setting circuit Ic polarity switching current (setting signal) ID current detection circuit Id current detection signal Ien electrode negative current Iep electrode positive current INT high frequency transformer INV output control circuit IP peak value setting circuit Ip peak value (setting signal) IPC peak value control setting circuit Ipc peak value control setting signal IPO peak value calculation circuit IS current setting circuit Is current setting signal Isc current control setting signal Iw welding current Ndr electrode minus drive signal NTR electrode negative polarity transistor OR1 First OR circuit OR2 Second OR circuit Pdr electrode plus drive signal PTR electrode plus polarity transistor RS polarity ratio setting circuit Rs polarity ratio (setting signal) RSC polarity ratio control setting circuit Rsc polarity ratio control setting signal SI current setting switching circuit Si current setting switching signal Snp polarity switching signal Ten electrode minus period Tep electrode plus period TN electrode minus peak value setting period timer circuit Tn electrode minus peak value setting period (signal) TND electrode minus falling period timer circuit Tnd electrode minus falling period (signal) Tnp electrode minus peak period Tns electrode minus peak value setting period setting signal Tnu electrode minus rise period TP electrode plus peak value setting period timer circuit Tp electrode plus peak value setting period (signal) TPD electrode plus falling period timer circuit Tpd electrode plus falling period (signal) Tpp electrode plus peak period Tps electrode plus peak value setting period setting signal Tpu electrode plus rising period Wb bead width Wc cleaning width WL reactor ΔIp peak value correction signal

Claims (3)

(57) [Claims] 1. After switching to the negative polarity of the electrode, there is a period during which an increasing current is applied with a gradient and a peak value is reached after reaching a peak value, and a gradient is provided from the peak value. Then, a substantially trapezoidal electrode negative current is applied during a predetermined electrode negative period, which is formed from the period in which a decreasing current is applied, and then increases with a slope after switching to the electrode positive polarity. A predetermined period that is formed from a period of conducting a current and a period of conducting a current of this peak value after reaching a peak value of the same value as that described above and a period of conducting a current that decreases with a slope from the peak value. A balanced trapezoid in which a substantially trapezoidal wave electrode plus current is passed during the electrode plus period, and the electrode minus period and the electrode plus period are defined as one cycle and are repeated at a frequency of a preset AC frequency setting value. In the output control method of AC TIG welding, the peak value is increased or decreased so that the welding current average value obtained by full-wave rectifying and averaging the electrode negative current and the electrode positive current is substantially equal to a predetermined current setting value. Output control method for AC TIG welding. 2. After switching to the negative polarity of the electrode, there is a period in which an increasing current is applied with a slope and a peak value is reached after reaching the peak value, and a period from which the peak value of the current is applied and a slope from the peak value. Then, a substantially trapezoidal electrode negative current is applied during a predetermined electrode negative period, which is formed from the period in which a decreasing current is applied, and then increases with a slope after switching to the electrode positive polarity. A predetermined period that is formed from a period of conducting a current and a period of conducting a current of this peak value after reaching a peak value of the same value as that described above and a period of conducting a current that decreases with a slope from the peak value. A balanced trapezoid in which a substantially trapezoidal wave electrode plus current is passed during the electrode plus period, and the electrode minus period and the electrode plus period are defined as one cycle and are repeated at a frequency of a preset AC frequency setting value. In the output control method of AC TIG welding, the AC frequency set value and a predetermined current set value are input, and the welding current average value obtained by averaging full-wave rectification of the electrode negative current and the electrode positive current is the current. An output control method for AC TIG welding, wherein the peak value is calculated and set by a predetermined peak value calculation function so as to be substantially equal to the set value. 3. An electrode minus period Ten = using an AC frequency set value Fs and a predetermined polarity ratio set value Rs as inputs.
(1 / Fs) .Rs and electrode plus period Tep = (1 / F
s) · (1−Rs) is set by the above calculation, and the AC frequency set value Fs and the polarity ratio set value Rs are input, and the AC surface frequency set value Fs is changed and the surface of the workpiece to be welded 2. The polarity ratio setting value Rs is corrected and set by a predetermined polarity ratio correction function so that the cleaning width of R is substantially constant without changing.
Alternatively, the output control method of AC TIG welding according to claim 2.