JP2001259837A - Method and device for high-frequency pulse welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve conventional problems that in high-frequency pulse welding, when handling a high-frequency pulse having a sharp rise and fall, a welding arc voltage and an arc current acting actually and effectively, are not proportional to an average current and an average torch voltage obtained by averaging simply pulse currents and voltage waveforms. Therefore, by a control like making the average current or the average voltage equal to a standard value as usual, there are problems that an arc is not stable, the depth of penetration of welding and weld width are changed with the elapse of time depending on a welding condition, and stable welding has been hard to various conditions. SOLUTION: To solve the above problems, by detecting an effective current and an effective voltage acting actually and effectively to a command current and a command voltage, by controlling these, and by controlling a power supply for high-frequency pulse welding so that the effective current and the effective voltage become equal to the command current and the command voltage, the stable welding is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a welding device,
In particular, the present invention relates to a control method and a power supply device for a high-frequency pulse welding power supply.

[0002]

2. Description of the Related Art Conventionally, DC welding or AC welding is mainly used, and pulse welding is often performed at a low frequency.
Japanese Patent Application No. 28568 discloses a high-frequency pulse welding which has features such as good straightness of arc and narrow groove welding with a narrow groove and deep penetration. The control was to control the average value of the arc voltage (torch voltage, welding voltage) or the average value of the welding current to be constant.
The problem when using high-frequency pulses is that the power supply unit including the pulse generator for welding, the welding torch, the inductance L of the cable to the welding base metal, and the increase in resistance R due to the skin effect due to the high frequency. As a result, the waveform becomes dull and the cable loss increases. Therefore, in order to make the welding current a high-frequency pulse, the voltage of the power supply device is made higher than that of the conventional DC welding or low-pulse welding to sharpen the rise and fall of the pulse.

[0003]

When dealing with such a high-frequency pulse having sharp rising and falling edges, the welding arc voltage and the arc current that actually act effectively are simply the average of the pulse current and the voltage waveform. It is not proportional to the current or the average torch voltage. Therefore, in the conventional control in which the average current or the average voltage is adjusted to the reference value, there is a problem that the arc is not stabilized due to the welding conditions, and the penetration depth and the welding width of the welding change with time. And stable welding was difficult.

[0004]

In order to solve the above-mentioned problems, an effective current and an effective voltage that actually act effectively on a command current and a command voltage are detected, and the effective current and the effective voltage are controlled to control the effective current and the effective voltage. The high-frequency pulse welding power supply is controlled so as to be equal to the command current and command voltage to enable stable welding.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 9, a general configuration of welding is that an alternating current supplied from a commercial power supply Syo is converted into a pulse by a power supply section Dng and attached to the tip of the torch section Th via a cable Cab. An arc Arc is generated from the electrode Pol and the welding base material Bo is welded. One embodiment of the present invention is shown in FIG. FIG. 1 shows a configuration of a power supply for high-frequency pulse welding, and shows electrical details of a power supply unit Dng, a cable Cab, and an arc unit Arc shown in FIG. The power supply unit Dng includes an AC-DC conversion unit ADC and a high-frequency pulse generation unit Pug. The AC-DC converter ADC shown by a dashed line for converting AC to DC from the commercial power source Syo converts it to a DC constant voltage, and its output is made by a high-frequency pulse generator Pug shown by a dashed line to generate a pulse, which is shown by a dashed line. Cable C
Operates to generate arc Arc via ab.

FIG. 8 shows the waveform of each part of the high-frequency pulse generator Pug of the present invention. The illustrated high-frequency pulse current i has a peak value ip, is composed of a waveform having a steep rise and fall, and has a high frequency of 5 to 20 kHz. Welding by such an electric current has such features that the straightness of the arc is good, narrow groove welding with a narrow groove is possible, and the penetration depth can be increased. Also, in order to pass such current, the cable
Considering the inductance Lh of Cab and the resistance Rh, the voltage Vb of the pulse generating power supply Pug is as shown in the figure. The arc voltage Vt (the voltage of the electrode or the torch voltage of the torch portion Th shown in FIG. 9) becomes like the illustrated voltage Vt due to the influence of the inductance Lh and the resistance Rh of the cable Cab. Arc voltage is Vt current
The waveform is close to I but not completely proportional. Therefore, control for making the arc voltage constant and control for making the current constant are performed as control methods. However, in the waveforms shown in the figure, the effective value and the average value that are actually effective are significantly different from each other, and it can be understood that accurate control cannot be performed by the conventional method of detecting the average voltage or the average current. In one example of the present invention, the average value of the voltage and the current showed only the effective value of 0.16 to 0.7, though it varied depending on the conditions.

FIG. 1 will be described in detail for each block. The AC-DC converter ADC rectifies the AC from the commercial power supply Syo with a diode bridge Rec that rectifies the AC, and a capacitor.
Smooth with C1 to DC. Then switching elements Q1, Q
The primary side of the transformer TF is connected via a bridge circuit composed of the second and diodes D1 and D2. The secondary side of the transformer TF is rectified and smoothed by diodes D3 and D4, inductance L1 and capacitor C2. This output is compared with the reference voltage Vrv, and the output controls the switching elements Q1 and Q2 via the pulse width controller PWM1. Since this constitutes a general double-forward type DC-DC converter, this output voltage V is kept constant.

Next, the pulse generator Pug is an AC-DC converter A
A DC circuit having a constant voltage V obtained from DC is input, and a switching circuit Q3, Q4 and diodes D5, D6 constitute a bridge circuit. The output of the bridge circuit generates an arc Arc via a cable Cab. Since a high-frequency pulse current flows through the cable section, a high-frequency effective inductance Lh and a high-frequency effective resistance Rh are generated as illustrated. In one example of the present invention, the high-frequency effective resistance was about 10 times the DC resistance. In addition, the instantaneous output current of the high-frequency pulse generator Pug is measured by the current sensor CD,
This is converted to an effective current by the effective value circuit Rms. This effective current is compared with the reference value Vrei, and the result is compared with the pulse width controller.
The switching elements Q3 and Q4 are controlled via PWM2 to control the arc effective current to be equal to the command effective value current corresponding to the reference value. With such a configuration, the effective current, which is a current that actually acts effectively, is controlled, so that stable welding can be performed. In particular, stable welding can be performed even with a small current. In addition, the heat that contributes to welding becomes constant, and the welding depth and welding width can be made uniform.

Next, another embodiment shown in FIG. 2 will be described.
FIG. 2 shows the control unit, the cable Cab, and the arc unit Arc of the high-frequency pulse generation unit Pug in FIG. 1, and the same symbols as those in FIG. 1 have the same functions. The control configuration of FIG. 2 converts the arc voltage Vt (which is substantially the same as the torch voltage measured at the torch unit) into an effective value by an effective value circuit Rms, and outputs the output to a reference value Vrev corresponding to the commanded arc voltage and an adder. Addition is performed by Ad1, and the output is added to the pulse width controller PWM2. The pulse width controller PWM2 generates a signal having a pulse width proportional to an error of the effective arc voltage with respect to the reference value Vrev output from the adder Ad1, and performs an AND operation.
Add to gate An1. The current detected by the current sensor CD is compared with the reference value ir1 by the comparator Cnp1, and the output is compared with the AND gate An.
Add 1 to 1 input terminal. The arc voltage Vt is compared with a reference value Vr3, and the output is applied to another terminal of the NAND gate Na1. AN
The output of the D gate An1 is connected to the gate of the switching element Q4, and the gate of Q3 is connected to the output of the pulse width controller PWM2.

As shown in FIG. 8, the current has a waveform which is small at the beginning of the current flow but gradually increases. When the current is smaller than the reference value ir1 which is the peak current set value, the effective voltage command value Vrev and the arc effective voltage Since Vt is compared and the error is fed back, switching elements Q3 and Q4 are turned on by a signal having a pulse width corresponding to the error, and power supply voltage V is applied to the arc portion through cable Cab, so that the current rapidly rises. At this time, E = (1
/ 2) Li ・ i ² energy is stored. When the current exceeds the reference value ir1, which is the peak current set value, the output of the AND gate An1 becomes L level, and only the switching element Q4 is turned off.Therefore, due to the energy stored in the inductance Lh of the cable Cab, the diode D6 The current is forward biased and the current continues to flow through the switching element Q3. Next, when the pulse generated by the pulse width controller PWM2 is turned off, the switching elements Q3 and Q4 are turned off, and due to the energy stored in the inductance Lh of the cable Cab, the diodes D6 and D5 are forward-biased, and Since the reverse voltage -V of the power supply voltage V is applied to the arc portion via Cab, the current rapidly falls, and when the current becomes zero, the diode is not forward biased and turns off. Thus, the effective voltage command value
Since Vrev and the arc voltage Vt are added and the error is fed back to control the width of the high frequency pulse, the arc effective voltage Vt is controlled to be constant. By repeating the above, the effective value arc voltage of the high frequency pulse is obtained.

FIG. 3 is a control configuration showing another embodiment. The same symbols as in FIG. 2 perform the same function. The instantaneous value of the current is detected by the current sensor CD, connected to the input of the effective value circuit Rms, compared with the reference value ir1 by the comparator Cm1, and the output is connected to the gate of the AND gate An1. RMS circuit Rm
The output converted to the effective value by s is added to the reference value Vrei corresponding to the effective current by the adder Ad1, and the output is added to the pulse width controller PWM2. The pulse width controller PWM2 generates a signal having a pulse width proportional to the error of the effective current with respect to the reference value Vrei output from the adder Ad1, and applies the signal to the AND gate An1. A
The output of the ND gate An1 is connected to the gate of the switching element Q4, and the gate of Q3 is connected to the output of the pulse width controller PWM2. As shown in FIG. 8, the current has a small waveform at the beginning of the current flow but gradually increases. The current command value Vrei is detected while the current is smaller than the reference value ir1, which is the peak current set value. The rms current is added by the adder Ad1, and the error is fed back, so that both the switching elements Q3 and Q4 are turned on by a signal having a pulse width corresponding to the error, and the power supply voltage V is applied to the arc section through the cable Cab.
The current rises rapidly because At this time, energy of E = (1) L · i ² is stored in the inductance Lh of the cable. Reference value ir where the current is the peak current set value
When it exceeds 1, the output of the AND gate An1 becomes L level and only the switching element Q4 is turned off.Therefore, due to the energy stored in the inductance Lh of the cable Cab, the diode D6 is forward-biased and the current flows through the switching element Q3. Keep flowing. Next, when the pulse generated by the pulse width controller PWM is turned off, the switching elements Q3 and Q4 are turned off, and due to the energy stored in the inductance Lh of the cable Cab, the diodes D6 and D5 are forward-biased and the cables D6 and D5 are forward-biased. Since the reverse voltage -V of the power supply voltage V is applied to the arc portion via the Cab, the current rapidly falls, and when it becomes zero, the diode is not forward biased. As described above, the current command value Vrei is compared with the effective value current, and the error is fed back to control the width of the high frequency pulse. Therefore, the effective value current is controlled to be constant. By repeating the above, the effective value current proportional to the command value of the high frequency pulse continues to flow.

FIG. 4 is a control block diagram showing another embodiment of the present invention. This configuration is characterized in that the control of FIGS. 2 and 3 can be switched and used. 2 and 3 perform the same operation. The arc voltage Vt (which is substantially the same as the torch voltage measured by the torch unit) is converted into an effective value by the effective value circuit Rms2, and the output is input to the switching circuit Kr via the effective value circuit Rm2. Further, the instantaneous value of the current is detected by the current sensor CD, and the detected instantaneous value is connected to another input of the switching circuit Kr via the effective value circuit Rms1. The output of the switching circuit Kr is added to the reference value Vrev of the torch voltage command or the reference value Vrei of the current command by the adder Ad, and the output is added to the pulse width controller PWM2. The pulse width controller PWM2 generates a signal having a pulse width proportional to the output of the adder Ad, and outputs the signal to the AND gate An1.
Add to The current detected by the current sensor CD is compared with the reference value ir1 by the comparator Cnp1, and the output is applied to one input terminal of the AND gate An1. The output of AND gate An1 is a switching element
Connect to the gate of Q4, and the gate of Q3 is the pulse width controller PWM2
Connect to the output of When the switching circuit Kr is connected to the effective current, a command is given to the reference value Veri of the current command, and the reference value Verv of the arc voltage command is set to zero. With such a configuration, the operation is the same as that of FIG. 3, and the error is fed back by adding the current command value Vrei and the detected effective value current to control the width of the high frequency pulse.
The effective value current is controlled to be constant. By repeating the above, the effective value current proportional to the command value of the high frequency pulse continues to flow.

When the switching circuit Kr is connected to the effective voltage side, a command is given to the reference value Verv of the arc voltage command, and the reference value Veri of the current command is set to zero. With this configuration, the operation is the same as that of FIG.
Since Vrev and the detected effective value arc voltage are added and the error is fed back to control the width of the high frequency pulse, the effective value voltage is controlled to be constant. By repeating the above, an effective value arc voltage proportional to the command value of the high-frequency pulse is obtained.

FIG. 5 is a control block diagram showing another embodiment of the present invention. This configuration is obtained by adding a protection circuit to FIG. The same thing as the symbol of FIG. 4 performs the same operation. FIG.
And the comparator Cm2 compares the output of the current sensor with a reference value Vr2 for protecting the current, and connects the output to a NAND gate Na1. Further, the comparator Cm3 compares the arc voltage Vt with a reference value Vr2 for protecting the voltage, and connects its output to another input of the NAND gate Na1. The output of the NAND gate Na1 is connected to the reset terminal of the flip-flop FF, and the output of the flip-flop FF is connected to one input terminal of the AND gate An2 and the flip-flop F
The set input terminal of F is connected to the voltage Vcc via the switch SW1. The output of the AND gate An2 is connected to the gate of the switching element Q3 and another input terminal of the AND gate An1, and the output of the AND gate An1 is connected to the gate of the switching element Q4.

Assuming that the current and the arc voltage are below the reference values Vr2 and Vr3 and the flip-flop FF is set by SW1, one of the inputs of the AND gate An1 is provided while the current is smaller than the reference value ir1. At the H level, the output of the AND gate An1 operates the same as the output of the AND gate An2. The two inputs of the NAND gate Na1 are at H level,
The output of Na1 is at L level, and the output of flip-flop FF is also at H level. Therefore, the output of the AND gate An2 becomes the same as the output signal of the pulse width controller PWM2. Therefore, FIG.
Works the same as.

In this state, it is assumed that a component breaks down and a large current or a large voltage is applied. Reference value ir2 where the current is greater than reference value ir1 which is the peak current setting
In this case, the output of the comparator Cm2 becomes H level, and NA
Since the output of the ND gate Na1 changes from L to H level and the flip-flop FF is reset to set the output to L level, A
The outputs of the ND gates An2 and An1 are also at the L level, and both the switching elements Q3 and Q4 are kept off. Similarly, when a large voltage is generated in the arc portion, the arc voltage Vt becomes larger than the reference value Vr3, the output of the comparator Cm3 changes from L to H level, the output of the NAND gate Na1 changes from L to H level, and the Since the output of the flip-flop FF is reset to the L level, the switching elements Q3 and Q4 are both kept off to prevent the failure from spreading and secure the safety.

FIG. 6 shows another embodiment, which is an improvement of FIG. The same symbols as in FIG. 2 perform the same operation. Arc voltage
Vt is detected and converted to an effective value voltage Vr by the effective value circuit Rms and input to the arithmetic unit Div. The detected arc voltage V
The value obtained by converting t into the peak value voltage Vp by the peak value circuit Pek is input to the calculator Div, and the peak value voltage Vp / effective value voltage Vr is calculated, and the result is added to the reference value Vpdr by the adder Ad. The output is input to the pulse width controller PWM2. With such a configuration, control is performed so that the peak value / effective value of the arc voltage matches the reference value. In high frequency pulse arc welding, the ratio of peak voltage to effective voltage is more important than DC arc, and by controlling this peak voltage to effective voltage ratio,
There is an effect that an arc having good straightness can be stably held.

FIG. 7 shows another embodiment, which is an improvement of FIG. 3 operate in the same manner. The arc current is detected by the current sensor CD and converted into an effective value current ir by the effective value circuit Rms and input to the arithmetic unit Div. Also, the result of converting the detected arc current into the peak current ip by the peak value circuit Pek is input to the calculator Div, and the peak value circuit Pek /
Calculate the effective value circuit Rms and add the result to the reference value i by the adder Ad.
The result is added to pdr and the output is input to the pulse width controller PWM2. With such a configuration, the peak value of the arc current ip /
The control is performed such that the effective value ir matches the reference value ipdr. In high frequency pulse arc welding, the ratio of peak current to effective current is more important than DC arc current, and controlling this peak current to effective current ratio has the effect of stably maintaining an arc with good straightness. .

[0019]

As described above, according to the present invention, even in high-frequency pulse welding with excellent arc straightness, the welding penetration depth and welding width do not change with time and are always suitable for various welding conditions. The effect is that stable welding can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power supply for high-frequency pulse welding showing an embodiment of the present invention.

FIG. 2 is a control configuration diagram showing another embodiment of the present invention.

FIG. 3 is a control configuration diagram showing another embodiment of the present invention.

FIG. 4 is a control configuration diagram showing another embodiment of the present invention.

FIG. 5 is a control configuration diagram showing another embodiment of the present invention.

FIG. 6 is a control configuration diagram showing another embodiment of the present invention.

FIG. 7 is a control configuration diagram showing another embodiment of the present invention.

FIG. 8 is a waveform diagram of each part of the high-frequency pulse generator of the present invention.

FIG. 9 is a diagram showing a general configuration of high frequency pulse welding.

[Explanation of symbols]

Q1, Q2, Q3, Q4 ... Switching elements, D1, D2, D3, D4, D5, D6 ...
Diode, L1… Inductance, Cab… Cable, Lh
… Cable high frequency inductance, Rh… Cable high frequency resistance, R1 to R17… Resistance, Syo… Commercial power supply, CD… Current sensor, Pug… High frequency pulse generator, PWM1, PWM2… Pulse width controller, Mut… Multiplier, Arc… Arc, Vt… Arc voltage,
Ad0, Ad1, Ad2 ... adder, Cm1 ... comparator, Kr ... switching circuit, Rms, Rm1, Rm2 ... effective value circuit, Hei ... smoothing circuit, Pek ...
Peak value circuit, Div… Calculator.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Kumasaka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory, Ltd. (72) Mitsuo Kato 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 F term in Hitachi Research Laboratory, Hitachi, Ltd. (reference) 4E082 DA02 EA02 EB11 EC03 EC13 ED01 EE01 EE04 EE05 EF02 EF07 EF15 FA01 FA04 FA06

Claims (11)

[Claims] 1. A high-frequency pulse generator for converting a direct current into a high-frequency pulse by a switching element that turns on and off at a high frequency. A high-frequency pulse current flows from the high-frequency pulse generator to an electrode and a welding base material via a cable. In a high-frequency pulse welding for performing welding, a high-frequency pulse welding method characterized in that an effective value of a pulse current is detected and on / off of a high-frequency pulse generator is controlled so that the detected effective current becomes equal to a command current. 2. A high-frequency pulse generator for converting a direct current into a high-frequency pulse by a switching element that turns on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In the high-frequency pulse welding for welding, the effective value and the peak value of the pulse current are detected, and the high-frequency pulse generator is turned on and off so that the ratio of the detected effective current to the peak current becomes equal to the ratio of the command effective current to the peak current. A high-frequency pulse welding method characterized in that turning off is controlled. 3. A high-frequency pulse generator for converting a direct current into a high-frequency pulse by a switching element that is turned on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high-frequency pulse welding for welding, the average value and peak value of the pulse current are detected, and the high-frequency pulse generator is turned on and off so that the ratio of the detected average value to peak value is equal to the ratio of the command average value to peak value. A high-frequency pulse welding method characterized in that turning off is controlled. 4. The high-frequency pulse welding method according to claim 2, wherein a command peak current value is used instead of a detected peak current value. 5. A high-frequency pulse generator for converting a direct current to a high-frequency pulse by a switching element that turns on and off at a high frequency, and a high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high-frequency pulse welding for welding, the effective value of the arc voltage between the electrode and the welding base material was detected, and the on / off of the high-frequency pulse generator was controlled so that the detected effective value of the arc voltage became equal to the command value. A high-frequency pulse welding method characterized in that: 6. A high-frequency pulse generator for converting a direct current to a high-frequency pulse by a switching element that is turned on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high frequency pulse welding for welding, the effective value and peak value of the arc voltage between the electrode and the welding base material are detected, and the high frequency pulse generator is turned on so that the ratio of the detected effective voltage to the peak voltage becomes equal to the command value. A high-frequency pulse welding method characterized in that off is controlled. 7. A high-frequency pulse generator for converting a direct current into a high-frequency pulse by a switching element that is turned on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high-frequency pulse welding for welding, the average value and peak value of the arc voltage between the electrode and the welding base material are detected, and the high-frequency pulse generator is turned on so that the ratio of the detected average voltage to peak voltage becomes equal to the command value. A high-frequency pulse welding method characterized in that off is controlled. 8. The high-frequency pulse welding method according to claim 6, wherein a commanded peak voltage value is used instead of the detected peak voltage value. 9. A high-frequency pulse generator for converting a direct current into a high-frequency pulse by a switching element that turns on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high-frequency pulse welding for welding, control to detect the pulse current and the effective value of the arc voltage between the electrode and the welding base metal, and control the on / off of the high-frequency pulse generator so that the detected effective current becomes equal to the command current. A high-frequency pulse welding method, wherein a system and a control system for controlling on / off of the high-frequency pulse generator are switched so that the detected effective voltage becomes equal to the command voltage. 10. A high-frequency pulse generator for converting a direct current to a high-frequency pulse by a switching element that is turned on and off at a high frequency, and a high-frequency pulse current is supplied from the high-frequency pulse generator to an electrode and a welding base material via a cable. In high-frequency pulse welding for welding, the pulse current or the effective value of the arc voltage between the electrode and the welding base metal is detected, and the high-frequency pulse generator is turned on so that the detected effective current or effective voltage becomes equal to the command current or command voltage. A high-frequency pulse welding method, wherein the high-frequency pulse generator is stopped when the detected current value exceeds a reference value larger than a normal value. 11. A high-frequency pulse generator for converting a direct current to a high-frequency pulse by a switching element that is turned on and off at a high frequency. A high-frequency pulse current is supplied from the high-frequency pulse generator to the electrode and the welding base material via a cable. In high-frequency pulse welding to perform welding, a means for detecting a pulse current or an effective value of an arc voltage between an electrode and a welding base metal, and a means for feeding back the detected effective current or effective voltage, the feedback to a command current or command voltage A high-frequency pulse welding apparatus comprising: a high-frequency pulse generator that controls on / off of a high-frequency pulse generator so that an effective current or an effective voltage becomes equal.