JPS6217163Y2 - - Google Patents

Description

[Detailed description of the invention] This invention enables wire feeding to quickly follow changes in arc length in the small and large welding current ranges, allowing for good welding. This article relates to a pulse arc welding machine.

In general, in a pulse arc welding machine that feeds a consumable welding wire for welding, when the arc length increases due to a sudden decrease in the wire feed speed during welding or due to a dent in the workpiece, the wire melting rate decreases and the arc length shortens again to return to the specified arc length, and conversely, when the arc length shortens for some reason, the wire melting rate increases and the arc length lengthens again to return to the specified arc length. That is, the pulse arc welding machine has a so-called self-regulating function of the arc, but in order to stabilize the melting of the wire even if the welding voltage fluctuates during normal welding, a constant current control of the base current is performed.

However, in this case, even if the arc length becomes longer during welding, a large amount of power is supplied to the welding load, so the arc length remains long and it takes a long time to return to the predetermined arc length. The disadvantage is that the arc on the side spreads, lowering the shielding and making welding defects more likely.

Therefore, as means for keeping the welding voltage approximately constant, means for detecting the arc voltage when the arc length changes and controlling the pulse width of the pulse current based on the detected voltage, means for controlling the base current, Measures have been taken to change the frequency of the pulsed current, but due to the large change in heat input during pulsed current, the molten ball becomes too large or there are too many molten balls, making it difficult to achieve good welding. I can't do it.

Therefore, a pulse arc welder is implemented in which the welding voltage when the arc length changes is detected and the wire feed speed is controlled based on the detected voltage.
For example, it may be configured as shown in Figures 1 to 3. In these figures, reference numeral 1 denotes a pulse arc power supply unit connected to an AC power supply and supplying a welding current consisting of a base current and a pulse current to a welding load, 2 denotes a consumable welding wire fed by roller 4 from wire roll 3, 5 denotes a base metal constituting the welding load together with wire 2, 6 denotes a current detector provided between power supply unit 1 and base metal 5 and detecting the welding current and outputting a detection signal, 7 denotes an output current setter outputting a command signal for setting the base current or the base current and the pulse current to a predetermined value, and 8 denotes a power supply control device which receives the detection signal from current detector 6 and the command signal from output current setter 7 and controls the output of power supply unit 1 to a constant current so that the welding current is constant.

9 is a wire feeding motor M that detects the welding voltage.
This is a wire feeding speed control device that controls the rotation speed of the wire, and consists of a circuit configuration surrounded by a chain line in FIG. That is, the positive of the wire feeding speed control device 9,
Negative input terminals a and b are connected to the wire 2 and the base material 5, respectively, and first and second resistors R1 and R2 for voltage division are provided in series between both input terminals a and b, and the first resistor R1 One end of the third resistor R3 is connected to the connection point between the and the second resistor R2, and the arc length setting device is composed of a reference DC power source E and a variable resistor VR.
The positive terminal of the DC power supply E of AS and one end of the variable resistor VR are connected to the positive input terminal a, and one end of the fourth resistor R4 is connected to the voltage dividing terminal of the variable resistor VR, and the non-inverting input terminal is the positive input terminal. The third and fourth resistors R are connected to the inverting input terminal of the operational amplifier Q connected to the terminal a.
3. The other end of R4 is connected, and the welding voltage signal at both ends of the first resistor R1 and the setting voltage signal for setting the arc length between the voltage dividing terminal of the variable resistor VR and the positive input terminal a are input. , a fifth output resistor R5 is connected between the inverting input terminal and the output terminal of the operational amplifier Q, and an operational amplifier (not shown) is connected to the output terminal of the operational amplifier Q via a sixth current-limiting resistor R6. The input end of the wire feeding motor control device MC is connected, the output end of the motor control device MC is connected to the wire feeding motor M, and a predetermined driving voltage is applied to the motor M by the motor control device MC. .

When starting the welding machine, the pulse arc power supply 1 applies a no-load voltage to the welding load consisting of the wire 2 and the base metal 5, and
The no-load voltage is divided by the first and second resistors R1 and R2 of the wire feed speed control device 9, and the voltage across the first resistor R1, which is the welding voltage signal, is divided by the third resistor R1 and R2.
The voltage of the DC power supply E of the arc length setting device AS is input to the inverting input terminal of the operational amplifier Q via the resistor R3, and is divided by the variable resistor VR.
The voltage between the voltage dividing terminal of the variable resistor VR and the positive input terminal a, which is a set voltage signal, is inputted to the inverting input terminal of the operational amplifier Q via the fourth resistor R4, and the operational amplifier Q adds the two voltages, The motor control device is connected from the output terminal of the operational amplifier Q through the sixth resistor R6.
A control command voltage signal is output to the MC, and the drive voltage applied to the motor M by the motor control device MC is fed back into the motor control device MC, and the voltage of the command voltage signal is adjusted by the operational amplifier of the motor control device MC. and the drive voltage are compared, and the motor control device is configured so that the difference between the two voltages becomes 0.
A driving voltage is applied from the MC to the motor M, the motor M rotates, and feeding of the wire 2 is started.

At this time, the no-load voltage from the power supply device 1 is higher than the predetermined welding voltage during welding, and the voltage across the first resistor R1, that is, the input voltage to the operational amplifier Q is high. The voltage of the command voltage signal is large, the driving voltage applied to the motor M is also large, the motor M rotates at high speed and feeds the wire 2, and the wire 2 is short-circuited to the base material 5, causing the wire 2 and the base material to be short-circuited. A current flows between wire 5 and wire 2, causing an arc to be generated and the welding machine to start.

Next, when welding is performed steadily after arc generation, the voltage between the wire 2 and the base metal 5 decreases from the no-load voltage to the predetermined welding voltage due to the generation of the arc. The voltage across the resistor R1 also decreases, and the voltage of the command voltage signal from the operational amplifier Q decreases to a predetermined value, causing the motor control device to
A predetermined drive voltage is applied to the motor M by the MC, the wire 2 is fed at a predetermined speed, and stable welding with a constant arc length is performed.

In addition, if the feeding speed of the wire 2 suddenly decreases during welding and the arc length increases, or if the
When the arc length becomes longer due to a depression in the welding part, the impedance between the wire 2 and the base metal 5 increases, so the voltage applied between the wire 2 and the base metal 5 by the power supply 1 increases as described above. higher than the predetermined welding voltage. And the first resistor R
1 increases from the normal state, the voltage of the command voltage signal from the operational amplifier Q increases and exceeds a predetermined value, and the motor controller MC applies a drive voltage to the motor M that is larger than the predetermined value. applied,
The wire 2 is fed to the base metal 5 side at high speed, the arc length is shortened again, and the steady welding state described above is quickly returned to perform stable welding. Also, when the arc length becomes shorter, the operational amplifier Q
The voltage of the command voltage signal from the wire 2 decreases to below a predetermined value, and the motor control device MC applies a drive voltage smaller than the predetermined value to the motor M.
is fed to the base metal 5 side at a low speed, the arc length becomes long again, and a steady welding state is quickly returned to perform stable welding.

However, when an iron wire with a diameter of 1.2 mm is pulse-arc welded using the pulse arc welding machine shown in Figure 2 in a shielding gas containing 20% carbon dioxide gas and 80% argon gas, the solid line in Figure 3 When the welding current exceeds 200A, the change in welding voltage is smaller than the change in welding current, and in the large current range of welding current of 200A or more, the change in welding voltage is affected by the change in arc length. The followability of feeding the wire 2 is getting worse. Also, oxygen is 2
%, diameter in shielding gas with 98% argon gas
When 1.2 mm stainless steel wire is pulsed arc welded, as shown by the broken line in the same figure, in the high current range of 200 A or more, the change in welding voltage is not as small as with iron wire, but the change in welding voltage is still small. The ability to follow the change in the arc length by detecting the welding voltage is poor.

Therefore, the power supply control device 8 causes the power supply device 1 to
When controlling the output of The followability of feeding the wire 2 deteriorates, making it impossible to perform good welding.

This invention has been made with the above-mentioned points in mind, and next, this invention will be explained in detail with reference to the drawings from FIG. 4 showing one embodiment of the invention.

In those drawings, the same symbols as in FIGS. 1 and 2 indicate the same things, and
The difference from the diagram is that in the wire feed speed control device 9', one end of the seventh resistor R7 is connected to the connection point between the first resistor R1 and the second resistor R2, and a Zener diode is connected to the other end of the seventh resistor R7. At the same time, the anode of Zener diode ZD is connected, and the cathode of Zener diode ZD is connected to the inverting input terminal of operational amplifier Q. A compensation circuit CC is configured to increase the amplification degree of Q, and one end of the 8th to 10th resistors R8 to R10 having different resistance values is connected to each contact of the changeover switch SW, and the common contact of the changeover switch SW and the 8th to - The other ends of the tenth resistors R8 to R10 are respectively connected to both ends of the compensation circuit CC.

Then, operate the changeover switch SW according to the material, diameter, etc. of the wire 2, and select the 8th to 10th resistors R8 to R1.
Select the appropriate one from 0 and set the output current setting device 7.
When the welding current from the power supply device 1 is set to a current value in the small current range by the power supply control device 8 to perform constant current control and welding, the welding voltage between the welding loads is low, so the Zener diode ZD becomes conductive. Therefore, the compensation circuit CC does not operate, and when the welding machine is started and in steady state, the voltage across the first resistor R1 increases to the eighth to The voltage between the voltage dividing terminal of the variable resistor VR and the positive input terminal a is input to the inverting input terminal of the operational amplifier Q through one of the resistors R8 to R10 selected from among the resistors R8 to R10. Resistor R4
is input to the operational amplifier Q through the operational amplifier Q.
A command voltage signal is output from the motor control device MC via the sixth resistor R6, and a driving voltage is applied to the motor M by the motor control device MC.
The welding machine is started and steady welding is performed. In addition, when the arc length becomes longer or shorter during welding, the same operation as in Figs. 1 and 2 is performed so that the wire 2 quickly follows the changes in the arc length and is fed. be provided.

Next, when welding is performed by controlling the welding current from the power supply 1 to a current value in a large current range using the output current setting device 7 and the power supply control device 8, the welding voltage between the welding loads is high. , the Zener diode ZD becomes conductive and the compensation circuit CC is activated.
When the welding machine is started and in steady state, the voltage across the first resistor R1, that is, the welding voltage signal, is
Since it is input to the inverting input terminal of the operational amplifier Q via a selected one of the 8th to 10th resistors R8 to R10 and the compensation circuit CC, the 7th resistor R7 and the 8th to 10th resistors R8 to R10 The amplification degree of the operational amplifier Q is adjusted by the parallel combined resistance with either of the compensating circuits.
As shown in Figure 5, when the welding current exceeds a predetermined value, the output of the operational amplifier Q, that is, the voltage value of the command voltage signal, changes in response to a change in the welding current. increases, the drive voltage applied to the motor M by the motor control device MC increases, the rotational speed of the motor M increases, and the followability of the feeding of the wire 2 to changes in the arc length improves.

Therefore, by providing the compensation circuit CC, the feed of the wire 2 can quickly follow changes in the arc length in both small and large welding current ranges, and the wire 2 can be fed quickly to the base metal 5 side. The arc does not spread, the shielding properties are good, a stable molten ball can be obtained, and good welding can be performed. In addition, by providing the 8th to 10th resistors R8 to R10 with different resistance values, which can be changed freely by the changeover switch SW, the material and diameter of the wire 2 can be changed.
Welding can be performed in accordance with the components of the shielding gas.

As described above, this invention includes a pulsed arc power supply device that supplies a welding current consisting of a base current and a pulsed current to a welding load, a partial voltage resistor connected to both ends of the welding load, and an arc length of the welding load. An arc length setting device that outputs a set voltage signal for setting, a non-inverting input terminal connected to one end of the welding load, and an inverting input terminal connected to the output end of the arc length setting device and the voltage dividing point of the voltage dividing resistor. an operational amplifier connected through a resistor to output a command voltage signal; and a motor control device that controls a wire feeding motor connected to the output end of the operational amplifier to control the feeding speed of the consumable welding wire. In the pulse arc welding machine, a compensation circuit including a series circuit of a Zener diode and a resistor is provided between the voltage dividing point of the voltage dividing resistor and the inverting input terminal.

Therefore, according to this invention, since a compensation circuit consisting of a series circuit of a Zener diode and a resistor is provided at the inverting input terminal of the operational amplifier, this compensation circuit is activated when the welding current exceeds a predetermined value. By increasing the amplification degree of the operational amplifier, the wire feeding can be made to quickly follow changes in the arc length in the small current range and large current range of the welding current, and good welding can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a pulse arc welding machine, Fig. 2 is a conventional wiring diagram of a part of Fig. 1, and Fig. 3 is the relationship between welding current and welding voltage in Fig. 1 using the wiring shown in Fig. 2. Figure 4 and the following drawings show one embodiment of the pulse arc welding machine of this invention, Figure 4 is a wiring diagram of the main parts, and Figure 5 is a diagram showing the relationship between welding current and output voltage of the operational amplifier. be. 1...Pulse arc power supply device, 9'...Wire feeding speed control device, AS...Arc length setting device,
Q...Operation amplifier, 2...Wire, M...Wire feeding motor, CC...Compensation circuit, SW...Selector switch, R8 to R10...Resistance.

Claims (1)

[Scope of utility model registration request] a pulsed arc power supply device that supplies a welding current consisting of a base current and a pulsed current to a welding load;
a partial voltage resistor connected to both ends of the welding load; an arc length setting device that outputs a setting voltage signal for setting the arc length of the welding load; and a non-inverting input terminal connected to one end of the welding load; an operational amplifier whose input terminal is connected to the output end of the arc length setting device and the voltage dividing point of the voltage dividing resistor via a resistor and outputs a command voltage signal; and an operational amplifier connected to the output end of the operational amplifier and wire feeding. In the pulse arc welding machine, a Zener diode and a resistor are connected between the voltage dividing point of the voltage dividing resistor and the inverting input terminal. A pulse arc welding machine equipped with a compensation circuit consisting of a series circuit.