JP5506590B2 - Arc welding machine - Google Patents

Description

  The present invention relates to a technique for switching a maximum load voltage characteristic of an arc welder according to a welding mode.

  When covering arc welding with an arc welder, if there are not two types of characteristics, the first maximum load voltage characteristic without the tack welding mode and the second maximum load voltage characteristic with the tack welding mode, the ignition and extinction In tack welding that repeats arc, the arc cannot be easily extinguished because the maximum load voltage is high.

  FIG. 8 is an electrical connection diagram of a conventional arc welder. In the figure, a primary rectifier circuit DR1 and a smoothing capacitor C1 form a DC power supply circuit. The primary rectifier circuit DR1 rectifies an AC power supply AC to generate a rectified voltage, and the smoothing capacitor C1 is a rectifier having a pulsating current. The voltage is smoothed to generate a DC voltage.

  The first switching element TR1 to the fourth switching element TR4 form a full-bridge inverter circuit, which converts a DC voltage into a high-frequency AC voltage and outputs it. The main transformer INT converts the high-frequency AC voltage into a voltage suitable for arc machining, and the secondary rectifier circuit DR2 rectifies the output of the main transformer INT and supplies DC power to the manual welding rod via the DC reactor L. Supply.

  The change-over switch SW is a change-over switch that has two contacts, contact a and contact b, and selects the tack welding mode. By selecting the a contact, there is no tack welding mode, and by selecting the b contact, there is a tack welding mode. become.

  When tack welding is performed by covering arc welding using the arc welding machine of the prior art shown in FIG. 8, the tap 1a provided on the secondary winding of the main transformer INT with the changeover switch SW set to the contact a side. Is connected to the secondary rectifier circuit DR2. At this time, the maximum load voltage characteristic is reduced to the second maximum load voltage characteristic, and when performing the butt welding tacking work, the arc can be easily extinguished and workability is improved.

  In the arc welding machine described in Patent Document 1, a thyristor element is connected to each tap provided in the secondary winding of the main transformer INT, and each thyristor is energized according to the welding method. Each tap provided on the secondary winding is selected.

Japanese Patent Laid-Open No. 11-58009

  When covering arc welding is performed with the above-described arc welding machine, arc extinguishing becomes difficult due to the high maximum load voltage, and workability is remarkably deteriorated in tack welding, and the product quality is also lowered.

  As a countermeasure, in the prior art of Patent Document 1, a tap provided on the secondary side winding of the main transformer INT is selected with a changeover switch SW and a tap with a low output voltage on the secondary side is selected to reduce the maximum load voltage. In addition, by generating the second maximum load voltage characteristic, tack welding that repeats short-circuiting and pulling with a manual welding rod is facilitated.

  However, the conventional technology requires a separate tap on the secondary side winding of the main transformer INT, and also requires a switch or thyristor element that supports high current to select this tap. Also gets higher.

  Therefore, an object of the present invention is to provide an arc welder that can easily perform tack welding without providing a tap on the secondary winding of the main transformer INT.

In order to solve the above-described problem, the invention of claim 1 includes a DC power supply circuit that outputs a DC voltage by rectifying and smoothing a commercial AC power supply, an inverter circuit that converts the DC voltage into a high-frequency AC voltage, and A main transformer that converts a high-frequency AC voltage into an AC voltage suitable for welding, a secondary rectifier circuit that rectifies the output of the main transformer, an output detection circuit that detects the rectified output current, and the detected A main control circuit for controlling the inverter circuit based on the output current, and an arc welding machine comprising:
A selection circuit for selecting a tack welding mode is provided, and when the tack welding mode is selected, the main control circuit performs an external characteristic control for forming a maximum load voltage characteristic obtained by stepping down the maximum load voltage at each output current value. An arc welding machine characterized by performing.

  The invention according to claim 2 is the arc welder according to claim 1, wherein the external characteristic control is performed only when the output current value is equal to or less than a predetermined output current reference value.

  The invention according to claim 3 is the arc welder according to claim 1, wherein the step-down value of the maximum load voltage at each output current value is changed according to the output current value.

  According to a fourth aspect of the present invention, in the arc welder according to any one of the first to third aspects, the external characteristic control is performed by reducing a maximum ON / Duty of the inverter circuit. is there.

  According to a fifth aspect of the present invention, a step-up / step-down chopper circuit for controlling an output DC voltage to be equal to a predetermined target voltage setting value is provided between the DC power supply circuit and the inverter circuit, and the external characteristic control is performed. The arc welding machine according to claim 1, wherein the arc welding machine is performed by decreasing the target voltage set value.

  According to the first and fourth aspects of the present invention, when the tack welding mode is selected, the maximum load voltage at each output current value is reduced by merely reducing the maximum On · Duty of the pulse signal for controlling the inverter circuit. Since the load voltage characteristic can be formed, the arc breakage is improved by welding by repeatedly raising and lowering the manual welding rod and repeating arc extinction and ignition, improving workability and improving the quality of welding.

  According to the second and fourth aspects of the present invention, when the tack welding mode is selected, the output current value is compared with a predetermined output current reference value in the small current region, and the output current value is equal to or less than the output current reference value. Since the maximum load voltage is reduced, the arc break is suppressed when the output current is not less than the reference value of the output current, and the arc break is improved only when the output current is not more than the reference value, thereby further improving the welding quality.

  According to the third and fourth aspects of the present invention, when the tack welding mode is selected, if the step-down value of the maximum load voltage is changed according to the output current value, the optimum maximum load voltage is obtained for each output current value. Tack welding with good quality is possible and the quality of welding is greatly improved.

  According to claim 5 of the present invention, the maximum load voltage characteristic is adapted to the tack welding mode only by changing the target voltage value of the standard buck-boost chopper circuit provided in the arc welding machine for different voltages. Since the load voltage characteristics can be achieved, new functions can be added without adding parts in addition to handling different voltages.

3 is an electrical connection diagram of the arc welder according to Embodiment 1. FIG. FIG. 3 is a characteristic diagram showing a maximum load voltage characteristic having a constant current characteristic of coated arc welding according to the first embodiment. 6 is an electrical connection diagram of an arc welder according to Embodiment 2. FIG. FIG. 10 is a characteristic diagram showing a maximum load voltage characteristic having a constant current characteristic of the coated arc welding according to the second embodiment. 6 is an electrical connection diagram of an arc welder according to Embodiment 3. FIG. FIG. 3 is a characteristic diagram showing a maximum load voltage characteristic having a constant current characteristic of coated arc welding according to the first embodiment. 6 is an electrical connection diagram of an arc welder according to Embodiment 4. FIG. It is an electrical connection figure of the arc welding machine of a prior art.

  FIG. 1 is an electrical connection diagram of the arc welder according to the first embodiment. In the figure, components having the same reference numerals as those in the electrical connection diagram of the arc welding machine of the prior art shown in FIG. 8 perform the same operations, and thus description thereof will be omitted, and only components having different reference numerals will be described.

  The selection circuit WD shown in FIG. 1 selects the presence or absence of the tack welding mode. The output current setting circuit IR sets a predetermined output current setting signal Ir.

  When the selection circuit WD selects the tack welding mode, the main control circuit SC outputs the tack welding mode signal Wc, and compares and calculates the value of the output current setting signal Ir and the value of the output current detection signal Id. The comparison calculation signal Sc is output.

  The pulse width modulation circuit PWM shown in FIG. 1 performs PWM control for modulating the pulse width with a constant pulse frequency, and the first output control signal Pw1 and the second output control signal Pw2 according to the value of the comparison calculation signal Sc. And a predetermined first maximum On · Duty, and a second maximum On · Duty that is smaller than the first maximum On · Duty by a predetermined value.

  The inverter drive circuit DK outputs the first inverter drive signal Dk1 and the fourth inverter drive signal Dk4 according to the first output control signal Pw1, and the second inverter drive according to the second output control signal Pw2. The signal Dk2 and the third inverter drive signal Dk3 are output.

  FIG. 2 is a diagram showing the maximum load voltage characteristics with or without tack welding according to the present invention. The operation of the first embodiment will be described below with reference to FIGS.

  The main control circuit SC shown in FIG. 1 outputs a tack welding mode signal Wc when the selection circuit WD selects the tack welding mode. When the tack welding mode signal Wc is input, the pulse width modulation circuit PWM is switched from the first maximum On · Duty to the second maximum On · Duty. At this time, the maximum load voltage characteristic corresponding to the tack welding mode is formed by stepping down the maximum load voltage at each output current value shown in FIG.

  For example, when setting the output current to 150 A and performing a butt welding tacking work, the operator pulls up the hand welding rod and cuts the arc every time the tacking work is completed. Then, the hand welding rod is moved to the next tacking location to generate an arc again. At this time, if the hand welding rod is pulled up to increase the arc length, the load voltage shown in FIG. 2 increases, and when the maximum load voltage reaches point A, the load voltage gradually increases and the output current decreases. For example, when the arc is cut when the output current reaches a point B in the vicinity of 5 A, the maximum load voltage is about 58 V when the tack welding mode is present, and the maximum load voltage is about 68 V when the tack welding mode is not present. Become.

  From the above, when the tack welding mode is present, the arc is easily extinguished when the operator pulls up the manual welding rod to cut the arc by lowering the maximum load voltage, so that the arc is easily extinguished so Etc., the workability is improved and the weldability quality is also improved.

FIG. 3 is an electrical connection diagram of the arc welder of the second embodiment.
In the figure, components having the same reference numerals as those in the electrical connection diagrams of the arc welder shown in FIGS. 1 and 8 perform the same operations, and thus description thereof will be omitted, and only components having different reference numerals will be described.

  The output current reference setting circuit RF shown in FIG. 3 sets a predetermined output current reference setting signal Rf. The comparison circuit CP compares the value of the output current detection signal Id with the value of the output current reference setting signal Rf. When the value of the output current detection signal Id is smaller than the value of the output current reference setting signal Rf, the comparison signal Cp Is set to High level.

  When the selection circuit WD selects the tack welding mode present, the main control circuit SC shown in FIG. 3 determines whether the comparison signal Cp is high level or low level, and when the comparison signal Cp is high level, the tack welding mode signal Wc is output, and when it is at Low level, output is stopped. The pulse width modulation circuit PWM is switched from the first maximum On · Duty to the second maximum On · Duty when the tack welding mode signal Wc is input, and the second when the input of the tack welding mode signal Wc is stopped. Is switched from the maximum On · Duty of the first maximum On · Duty.

  As shown in FIG. 4, for example, when the operator performs the covering arc welding in the range of the output current of 50A to 400A, the pulse width modulation circuit PWM performs the covering arc welding at the first maximum On · Duty where the maximum load voltage becomes high. Therefore, stable welding without arc interruption becomes possible. For example, in the range where the output current is 50 A or less, the pulse width modulation circuit PWM is subjected to the covering arc welding with the second maximum On · Duty that reduces the maximum load voltage.

  When the butt welding tacking work is completed in the covering arc welding, the operator performs the work of lifting the hand welding rod and cutting the arc. At this time, when the arc length is lengthened by pulling up the manual welding rod, the value of the output current detection signal Id decreases as the arc length increases. The comparison circuit CP sets the comparison signal Cp to the high level when the value of the output current detection signal Id becomes smaller than the value of the output current reference setting signal Rf (for example, 50 A) (for example, 50 A).

  When the comparison signal Cp becomes High level, the main control circuit SC outputs the tack welding mode signal Wc, and the pulse width modulation circuit PWM switches from the first maximum On · Duty to the second maximum On · Duty. At this time, the maximum load voltage with an output current of 50 A or less shown in FIG. 4 is stepped down.

  When an operator sets the output current to 150 A and performs a butt welding tentative work, the operator pulls up the hand welding rod and cuts the arc every time the tempering work is completed at one place. Then, the hand welding rod is moved to the next tacking location to generate an arc again. At this time, when the arc length is increased by pulling up the manual welding rod, the load voltage shown in FIG. 4 increases. When the maximum load voltage reaches point A, the load voltage gradually increases and the output current decreases. At this time, when the arc length is lengthened by further lifting the manual welding rod, the value of the output current detection signal Id decreases as the arc length increases. The comparison circuit CP sets the comparison signal Cp to High level when the value of the output current detection signal Id becomes smaller than the value of the output current reference setting signal Rf (for example, 50 A).

  At this time, the maximum load voltage is stepped down. When the arc is cut when the output current reaches point B in the vicinity of 5 A, the load voltage is about 58 V when the tack welding mode is present, and is about 68 V when there is no tack welding.

  From the above, when the tack welding mode is present, the arc is easily extinguished when the operator pulls up the manual welding rod to cut the arc by lowering the maximum load voltage, so that the arc is easily extinguished so Etc., the workability is improved and the weldability quality is also improved.

  FIG. 5 is an electrical connection diagram of the arc welder of the third embodiment. The operation will be described below with reference to FIGS.

  Main control circuit SC outputs tack welding mode signal Wc when selection of presence of tack welding mode is selected by selection circuit WD.

  When the tack welding mode signal Wc is input, the pulse width modulation circuit PWM shown in FIG. 5 has a value obtained by adding, for example, 12V (32V + 0) to the standard load voltage characteristic calculated by (20V + 0.04 × IA) shown in FIG. .04 × IA) is generated.

When the operator sets the output current to 150 A and performs the butt welding temporary work, the maximum On · Duty is controlled by the formula (32V + 0.04 × IA), and the maximum load voltage 54 V at point A is stepped down. It becomes 38V.
Then, every time the tacking operation is completed, the operator pulls up the manual welding rod to cut the arc. At this time, when the arc length is increased by pulling up the hand welding rod, the load voltage shown in FIG. 6 increases, and when the load voltage reaches 38 V at point A, the load voltage gradually decreases and the output current also decreases. For example, when the arc is cut when the output current reaches point B in the vicinity of 5 A, the load voltage is about 32 V when the tack welding mode is present, and is about 68 V when the tack welding mode is not present.

  From the above, when the tack welding mode is present, the step-down value of the maximum load voltage is optimized for each output current value. Arcs can be extinguished easily, improving workability and improving weldability.

  FIG. 7 is an electrical connection diagram of the arc welder of the fourth embodiment. In the figure, components having the same reference numerals as those of the electrical connection diagram of the arc welder shown in FIGS. 1 and 8 perform the same operations, and thus description thereof will be omitted, and only components having different reference numerals will be described.

  The electrical connection diagram shown in FIG. 7 is a standard arc welding machine corresponding to a different commercial AC voltage, and a step-up / down voltage formed by a fifth switching element TR5, a diode D1, a second DC reactor DCL2, and a capacitor C2. A chopper circuit is provided as a standard between the DC power supply circuit and the inverter circuit, and supplies the DC voltage from the DC power supply circuit to the inverter circuit by making it equal to a predetermined target voltage setting value.

  When the selection circuit WD selects the presence of the tack welding mode, the main control circuit SC shown in FIG. 7 changes a predetermined On / Duty of the step-up / down chopper control signal Cc that is a pulse signal.

  The step-up / step-down chopper drive circuit CH outputs a step-up / step-down chopper drive signal Ch that drives the fifth switching element TR4 according to the step-up / step-down chopper control signal Cc.

Next, the operation will be described.
When the selection circuit WD selects the tack welding mode, the main control circuit SC shown in FIG. 7 outputs the step-up / step-down chopper control signal Cc changed to predetermined On · Duty and the value of the output current setting signal Ir. Is compared with the value of the output current detection signal Id to output a comparison calculation signal Sc.

  The pulse width modulation circuit PWM performs PWM control for modulating the pulse width with a constant pulse frequency, and the pulse widths of the first output control signal Pw1 and the second output control signal Pw2 according to the value of the comparison calculation signal Sc. To control.

  When the Ton / Toff On / Duty of the fifth switching element TR5 is changed from 1 to 0.9, for example, and the buck-boost chopper circuit operates as a buck circuit, the buck-boost chopper circuit operates as a DC voltage Vd of the DC power supply circuit. Is stepped down to 0.9Vd from the equation Vo = (Ton / Toff) × Vd and input to the inverter circuit. Then, it is possible to perform external characteristic control for forming a maximum load voltage characteristic in which the maximum load voltage at each output current value is stepped down by the step-down operation of the step-up / down chopper circuit.

  In the above description, an output current reference setting circuit RF and a comparison circuit CP (not shown) are provided. The comparison circuit CP compares the value of the output current detection signal Id with the value of the output current reference setting signal Rf, and outputs the output current detection signal. When the value of Id is smaller than the value of the output current reference setting signal Rf, the comparison signal Cp is set to High level.

  The main control circuit SC may change On / Duty of the step-up / step-down chopper control signal Cc when the comparison signal Cp becomes High level.

  From the above, the external characteristic control that forms the maximum load voltage characteristic can be controlled to the external characteristic suitable for the covered arc welding by simply controlling the On / Duty of the buck-boost chopper circuit provided in the arc welding machine. Therefore, it is not necessary to provide new parts.

C1 Smoothing capacitor C2 Capacitor Cc Buck-boost chopper control signal CP Comparison circuit Cp Comparison signal CH Buck-boost chopper drive circuit Ch Buck-boost chopper drive signal D1 First diode DK Inverter drive circuit Dk1 First inverter drive signal Dk2 Second inverter Drive signal Dk3 Third inverter drive signal Dk4 Fourth inverter drive signal DCL DC reactor DCL2 Second DC reactor DR1 Primary rectifier circuit DR2 Secondary rectifier circuit ES Manual welding rod ID Output current detection circuit ID Output current detection signal INT Main transformer IR output current setting circuit Ir output current setting signal (output current reference value)
RF output current reference setting circuit Rf Output current reference setting signal (output current reference setting value)
M Workpiece PWM pulse width modulation circuit Pw1 first output control signal Pw2 second output control signal SC main control circuit Sc comparison operation signal SW changeover switch TR1 first switching element TR2 second switching element TR3 third Switching element TR4 Fourth switching element TR5 Fifth switching element WD selection circuit Wc Tack welding mode signal

Claims (5)

A DC power supply circuit that outputs a DC voltage by rectifying and smoothing a commercial AC power supply, an inverter circuit that converts the DC voltage into a high-frequency AC voltage, and a main transformer that converts the high-frequency AC voltage into an AC voltage suitable for welding A secondary rectifier circuit that rectifies the output of the main transformer, an output detection circuit that detects the rectified output current, and a main control circuit that controls the inverter circuit based on the detected output current; In an arc welding machine equipped with
A selection circuit for selecting a tack welding mode is provided, and when the tack welding mode is selected, the main control circuit performs an external characteristic control for forming a maximum load voltage characteristic obtained by stepping down the maximum load voltage at each output current value. An arc welding machine characterized by performing.   The arc welding machine according to claim 1, wherein the external characteristic control is performed only when the output current value is equal to or less than a predetermined output current reference value.   The arc welding machine according to claim 1, wherein the step-down value of the maximum load voltage at each output current value is changed according to the output current value.   The arc welding machine according to any one of claims 1 to 3, wherein the external characteristic control is performed by reducing a maximum ON / Duty of the inverter circuit.   A step-up / step-down chopper circuit for controlling the output DC voltage to be equal to a predetermined target voltage setting value is provided between the DC power supply circuit and the inverter circuit, and the external characteristic control is reduced by the target voltage setting value. The arc welding machine according to any one of claims 1 to 3, wherein the arc welding machine is performed.

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