JP2021041413A - Welding power supply device - Google Patents

Abstract

To provide a welding power supply device capable of restraining the occurrence of an arc shortage.SOLUTION: A welding power supply device 1 is a welding power supply device that outputs a welding current for arc stud welding for welding a stud S to a base material W, and includes: a main current output unit 12 having a thyristor and outputting a main current being a direct current; a pilot current output unit 13 that starts output of a pilot current being a DC current when welding is started and continues the output of the pilot current even after the main current output unit 12 started output of the main current; a welding current setting unit 141 that sets a preset value of the welding current; and a control unit 144 that, when the preset value is equal to or greater than a prescribed current value, stops the output of the pilot current from the pilot current output unit 13 in a period until the stud S and the base material W are short-circuited after the main current output unit 12 started the output of the main current.SELECTED DRAWING: Figure 1

Description

The present invention relates to a welding power supply device for performing arc stud welding.

Welding power supply devices that output welding current for arc stud welding that welds studs to the base metal are known. The welding power supply device for arc stud welding adjusts the welding current by phase control by a thyristor, for example, when handling a large current of about 2500 A. Patent Document 1 discloses a welding power supply device for arc stud welding including a thyristor. At the start of welding, the welding power supply device outputs a pilot current, which is a direct current of about several tens of A, and pulls the stud away from the base metal to generate a pilot arc. Then, the output current is switched from the pilot current to the welding current to generate the main arc. The welding power supply device outputs a direct current that is rectified by a circuit including a thyristor and smoothed by a direct current as a welding current.

Welding power supply devices for arc stud welding are required to be smaller and lighter for convenience such as movement between construction sites. To meet this demand, welding power supply devices that do not have a DC reactor or that have a small DC reactor with a small inductance value have been developed. In such a welding power supply device, the occurrence of arc breakage in a small current region has become a problem.

Japanese Unexamined Patent Publication No. 4-4977

The present invention has been devised under the above circumstances, and an object of the present invention is to provide a welding power supply device capable of suppressing the occurrence of arc breakage.

The welding power supply device provided by the present invention is a welding power supply device that outputs a welding current for arc stud welding in which a stud is welded to a base material, and has a thyristor and a main current which is a DC current. A pilot current that starts the output of the main current output unit to be output and the pilot current that is a DC current at the start of welding, and continues the output of the pilot current even after the main current output unit starts the output of the main current. The output unit, the welding current setting unit that sets the setting value of the welding current, and the stud after the main current output unit starts the output of the main current when the set value is equal to or more than a predetermined current value. It is provided with a control unit that stops the output of the pilot current from the pilot current output unit during the period until the base material is short-circuited.

In a preferred embodiment of the present invention, the control unit controls the welding current so as to increase from the pilot current to the set value, and at the timing of controlling the welding current to the set value, the pilot. Stop the current output.

In a preferred embodiment of the present invention, the control unit stops the output of the pilot current when the set value is less than the predetermined current value and the stud and the base material are short-circuited.

In a preferred embodiment of the present invention, a welding time setting unit for setting a welding time from the start of output of the main current to the short circuit between the stud and the base metal is further provided.
When the welding time is equal to or longer than a predetermined time, the control unit has the pilot current during the period from when the main current output unit starts to output the main current until the stud and the base material are short-circuited. Stops the output of.

In a preferred embodiment of the present invention, the main current output unit includes an input terminal for inputting an alternating current and an output terminal for outputting the main current, and the pilot current output unit includes the input terminal. It has a thyristor and a resistor connected to the output terminal and connected in series with each other.

According to the present invention, the pilot current output unit starts the output of the pilot current at the start of welding, and continues the output of the pilot current even after the main current output unit starts the output of the main current. Therefore, even when the welding current is small, the pilot current is also output, so that the occurrence of arc breakage can be suppressed. Further, the control unit stops the output of the pilot current when the set value of the welding current is equal to or higher than the predetermined current value. As a result, the load on the pilot current output unit can be reduced in a large current region where arc breakage is unlikely to occur.

It is a block diagram which shows the whole structure of the arc stud welding system provided with the welding power supply device which concerns on 1st Embodiment. It is a flowchart for demonstrating the arc stud welding process. It is a time chart for explaining the arc stud welding process. It is a time chart for demonstrating the arc stud welding process of the modification of the welding power supply device which concerns on 1st Embodiment. It is a block diagram which shows the whole structure of the arc stud welding system provided with the welding power supply device which concerns on 2nd Embodiment.

Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a diagram for explaining a welding power supply device according to the first embodiment, and is a block diagram showing an overall configuration of an arc stud welding system including the welding power supply device.

The arc stud welding system A includes a welding power supply device 1, power cables 21, 22, a welding gun G, a stud S, and a base material W. The output terminal a of the welding power supply device 1 is connected to the welding gun G by a power cable 21. The stud S is attached to the welding gun G and is arranged so as to come into contact with the base metal W. The output terminal b of the welding power supply device 1 is connected to the base material W by the power cable 22. The welding power supply device 1 converts an alternating current supplied from the commercial power supply P into a direct current and outputs the current. Further, the welding power supply device 1 controls the drive of the welding gun G. The welding power supply device 1 outputs a pilot current, which is a direct current of about several tens of A, when the gun switch of the welding gun G is pressed. Then, the welding gun G is driven to separate the stud S from the base material W to generate an arc. Next, the welding power supply device 1 outputs a welding current for a predetermined time to melt the stud S and the base material W by an arc, and then stops the driving of the welding gun G to press the stud S against the base material W. .. As a result, the stud S is welded to the base material W.

The welding power supply device 1 includes a transformer 11, a main current output unit 12, a pilot current output unit 13, and a control device 14.

The transformer 11 steps down (or boosts) the three-phase AC voltage input from the commercial power supply P, and in the present embodiment, it is a double-star connection transformer with an interphase reactor. In the present embodiment, the transformer 11 steps down the 200V AC voltage input from the commercial power supply P to an AC voltage of 100V and outputs it. The transformer 11 is provided with a delta-connected primary side winding 111 on the primary side, and Y-connected (star-shaped) secondary side windings 112 and 113 on the secondary side, respectively, with neutrality. The points are connected via an interphase reactor 114 to obtain a six-phase output. The primary winding 111 is connected to the commercial power supply P. The secondary windings 112 and 113 are connected to each input terminal of the main current output unit 12, and the center tap provided on the interphase reactor 114 is connected to the power cable 22 via the output terminal b. There is.

The circuit configuration of the transformer 11 is not limited to that described above. The reason why the output to the main current output unit 12 on the secondary side is six-phase is to smooth the output from the main current output unit 12 as much as possible. For example, the output may be 12 phases for smoothing. Further, in order to make the circuit simpler, the secondary side winding 113 and the interphase reactor 114 may not be provided, and the output may be three-phase. Further, in the present embodiment, the connection method between the primary side winding 111 and the secondary side windings 112 and 113 is Δ-Y connection, but Δ-Δ connection, Y-Δ connection, and YY connection. Other connection methods such as may be used.

The main current output unit 12 outputs a main current, which is a direct current that is the center of the welding current. The main current output unit 12 includes a plurality of thyristors, and adjusts the main current by phase control while rectifying the alternating current input from the transformer 11. In the present embodiment, the main current output unit 12 includes six thyristors. The anode terminals of each thyristor are connected to each other and are connected to the power cable 21 via the output terminal a. In this embodiment, no DC reactor is connected between the main current output unit 12 and the output terminal a. The cathode terminals of each thyristor are connected to the six-phase outputs of the transformer 11. Further, a trigger pulse for control is input from the control device 14 to the gate terminal of each thyristor. The control device 14 changes the turn-on timing of each thyristor by changing the phase of the trigger pulse, and adjusts the main current output by the main current output unit 12. The circuit configuration of the main current output unit 12 is not limited to that described above. For example, the main current output unit 12 may include a mixed bridge circuit including a thyristor and a diode, and perform full-wave rectification.

The pilot current output unit 13 outputs a pilot current. The pilot current output unit 13 includes three thyristors and resistors. Each thyristor functions as a rectifying element and also as a switch. The anode terminals of each thyristor are connected to each other and connected to one end of the resistor. The other end of the resistor is connected to the output terminal a. The cathode terminal of each thyristor is connected to each output of the secondary winding 112 of the transformer 11. That is, each thyristor is connected in series to a resistor, and a series circuit composed of each thyristor and the resistor is parallel to the input terminal and the output terminal (output terminal a of the welding power supply device 1) of the main current output unit 12. It is connected. As a result, the welding power supply device 1 can output the pilot current by superimposing it on the main current.

Further, a control signal for on / off switching is input from the control device 14 to the gate terminal of each thyristor. The control device 14 switches the output of the pilot current output unit 13 on and off according to the control signal. That is, the control device 14 turns on each thyristor by the control signal to conduct the output of the secondary winding 112 of the transformer 11 and the resistor to output the pilot current. On the other hand, by turning off each thyristor by the control signal, the output and the resistance of the secondary winding 112 of the transformer 11 are cut off, and the output of the pilot current is stopped.

The resistor adjusts the pilot current output by the pilot current output unit 13. The resistance value of the resistor is _{designed so that the set current I 1} of the pilot current is set to a desired current value. The set current I ₁ is a fixed current value determined by the resistance value of the resistor and the output voltage value of the secondary winding 112 of the transformer 11. In the present embodiment, the resistance value of the resistor is 2.5Ω, and the output voltage value of the secondary winding 112 of the transformer 11 is 100V. Therefore, the set current I ₁ is 46 (= 100 × 1.15 / 2. 5) It is about A. The resistance value of the resistor is not limited. Further, the allowable loss of the resistor is set based on the _{predetermined time T 0} , which is the maximum value of the time for passing the pilot current. In the present embodiment, the predetermined time T ₀ is, for example, 0.8 s. The predetermined time T ₀ is not limited. In this embodiment, the resistance value of the resistor is 2.5Ω, the output voltage value of the secondary winding 112 of the transformer 11 is 100V, and the cycle time of the usage rate is 10s. Therefore, the loss Wr in the resistor is Wr = {( 100 × 1.15) ^{2 /} 2.5} × (0.8 / 10) = 423W. Therefore, a resistor that can tolerate this is used.

The configuration of the pilot current output unit 13 is not limited to the above. For example, the pilot current output unit 13 may include a switch and a diode instead of the thyristor.

The control device 14 controls the welding power supply device 1 in various ways. The control device 14 includes a welding current setting unit 141, a welding time setting unit 142, a timekeeping unit 143, and a control unit 144.

The welding current setting unit 141 sets the set value I ₂ of the welding current. The welding time setting unit 142 sets the welding time T ₂ . The welding time T ₂ is the time from the start of the output of the main current to the short circuit between the stud S and the base metal W. The welding current set value I ₂ and the welding time T ₂ are set as standard welding conditions according to the stud diameter of the stud S to be used. The operator sets the welding current setting unit 141 and the welding time setting unit 142 by inputting _{the set value I 2} and the welding time T ₂ according to the stud S to be used by operating an operation unit (not shown). In the control device 14, the operator inputs the stud diameter and the product number of the stud S to set the set value I ₂ and the welding time T ₂ according to the stud S, and the welding current setting unit 141 and the welding time setting unit. It may be set to 142 automatically. The time measuring unit 143 is a timer for measuring the time, and measures the welding time T ₂ , the pilot time T ₁ described later, the post heat time T _{3, and the} like.

The control unit 144 controls the welding current output by the welding power supply device 1 by adjusting the main current output by the main current output unit 12. The control unit 144 outputs the main current by inputting a trigger pulse to each thyristor of the main current output unit 12, and changes the turn-on timing of each thyristor by changing the phase of the trigger pulse to change the main current. To adjust. Further, the control unit 144 controls the start and stop of the pilot current output by inputting a control signal to the pilot current output unit 13. When the pilot current output unit 13 outputs the pilot current, the current in which the pilot current is superimposed on the main current is controlled as the welding current and is output from the output terminals a and b. On the other hand, when the pilot current output unit 13 does not output the pilot current, the main current is controlled as the welding current and is output from the output terminals a and b. Further, the control unit 144 controls the drive of the welding gun G via a control line (not shown).

FIG. 2 is a flowchart for explaining the arc stud welding process performed by the control unit 144. The arc stud welding process is started when a signal indicating that the gun switch has been pressed is input from the welding gun G. The operator starts the arc stud welding process by pressing the gun switch of the welding gun G in a state where the stud S and the base material W are in contact with each other.

First, the output of the pilot current is started (S1). Specifically, the control unit 144 outputs a control signal for turning on each thyristor to the pilot current output unit 13. The pilot current output by the pilot current output unit 13 is output from the output terminals a and b, and flows through the contacted stud S and the base material W. Next, the passage of the pilot time T ₁ is awaited (S2). The pilot time T ₁ is set in advance, and in the present embodiment, it is, for example, about 20 ms. The pilot time T ₁ is not limited. Next, the welding gun G is driven (S3). Specifically, the control unit 144 outputs a drive command to the welding gun G. The welding gun G to which the drive command is input pulls the stud S away from the base material W. As a result, an arc is generated between the stud S and the base material W. The period from the start of the pilot current output to the _{elapse of the pilot time T 1} is hereinafter referred to as the "pilot period".

Next, the output of the main current is started (S4). Specifically, the control unit 144 outputs a trigger pulse for controlling each thyristor to the main current output unit 12. The main current output by the main current output unit 12 is superimposed on the pilot current and output from the output terminals a and b. Control unit 144, by changing the phase of the trigger pulse, the main current output section 12 adjusts the main current output from the welding the welding current from the pilot current the current setting unit set value to 141 I ₂ to gradually increase during the slope time T _4. The slope time T ₄ is set in advance, and in this embodiment, it is, for example, about 40 ms. The slope time T ₄ is not limited.

Next, the elapse of the slope time T ₄ is awaited (S5). When the slope time T ₄ elapses, the welding current output from the welding power supply device 1 is controlled to _{the set value I 2 set in the welding current setting unit 141.} The period from the start of the output of the main current to the _{elapse of the slope time T 4} is hereinafter referred to as the “slope period”. Since the output of the pilot current is also continued during the slope period, the current obtained by superimposing the pilot current on the main current is output as the welding current from the output terminals a and b.

Next, it is determined whether or not the set value I ₂ is equal to or greater than the predetermined current value I _{0 (S6).} The predetermined current value I ₀ is a threshold value for determining whether or not arc breakage may occur when the welding current is _{controlled to the set value I 2.} In this embodiment, the predetermined current value I ₀ is, for example, 800 A. The predetermined current value I ₀ is not limited. When the set value I ₂ is equal to or higher than the predetermined current value I ₀ (S6: YES), it can be determined that the arc breakage hardly occurs, so that the output of the pilot current is stopped (S7), and the process proceeds to step S9. Specifically, the control unit 144 outputs a control signal for turning off each thyristor to the pilot current output unit 13. As a result, the pilot current output unit 13 stops the output of the pilot current. That is, when the set value I ₂ is equal to or higher than the predetermined current value I ₀ , the pilot current output is stopped at the timing when the welding current is _{controlled to the set value I 2,} and only the main current is output from the output terminals a and b. Will be output as the welding current.

In step S6, when the set value I ₂ is less than the predetermined current value I ₀ (S6: NO), it is determined whether or not _{the welding time T 2} is equal to or more than the predetermined time T _{0 (S8).} When the welding time T ₂ is equal to or longer than the predetermined time T ₀ (S8: YES), the loss Wr at the resistance of the pilot current output unit 13 may exceed the allowable loss, so that the pilot current output is stopped (S8: YES). S7), the process proceeds to step S9. That is, when the welding time T ₂ is equal to or longer than the predetermined time T _{0 , the pilot current output is stopped at the timing when the welding current is controlled to the set value I 2,} and only the main current flows from the output terminals a and b. It will be output as a welding current. Strictly speaking, a loss occurs due to the resistance even during the pilot time T _{1 , so in step S8 (T 1} + T ₂ ) should be compared with the predetermined time T ₀ , but the pilot time T ₁ is the welding time T. _Since it is much smaller than _{2 and the predetermined time T 0} is set to a value with some margin, it is omitted here for comparison. In step S8, (T ₁ + T ₂ ) may be compared with _{T 0} for a predetermined time.

In step S8, when the welding time T ₂ is less than the predetermined time T ₀ (S8: NO), the loss Wr at the resistance of the pilot current output unit 13 does not exceed the allowable loss, so that the pilot current output is continued. Continue to step S9. In actual arc stud welding, when the set value I ₂ is less than the predetermined current value I ₀ (for example, 800 A), the welding time T ₂ does not exceed the predetermined time T ₀ (for example, 0.8 S). Therefore, the output of the pilot current is continued when the actual arc stud welding is being performed. _{On the other hand, when the set value I 2} is less than the predetermined current value I ₀ and the welding time T ₂ is set to the predetermined time T ₀ or more at the time of product inspection of the welding power supply device 1 or at the time of periodic ammeter calibration. There is. In this case, since the arc stud welding is not performed and it is not necessary to consider the arc breakage, no problem occurs even if the output of the pilot current is stopped.

Next, the elapse of the _{welding time T 2} is awaited after the output of the main current is started (S9). The period from the start of the output of the main current to the _{elapse of the welding time T 2} is hereinafter referred to as the "welding period". During this welding period, the arc heats and melts the stud S and the base metal W. Next, the driving of the welding gun G is stopped (S10). Specifically, the control unit 144 outputs a stop command to the welding gun G. The welding gun G to which the stop command is input presses the molten stud S against the molten base material W. As a result, the stud S is welded to the base material W.

Next, the output of the pilot current is stopped (S11). Since the stud S and the base material W are short-circuited and the arc is extinguished, a pilot current for suppressing the arc breakage is unnecessary. Next, the elapse of the post heat time T ₃ is awaited (S12). The post heat time T ₃ is preset according to the welding current I ₂ , and in this embodiment, it is, for example, about 0.1 to 0.2 s. The post heat time T ₃ is not limited. Next, the output of the main current is stopped (S13), and the arc stud welding process is completed. Specifically, the control unit 144 stops the output of the trigger pulse to the main current output unit 12. The period from when the welding gun G is stopped to when the post heat time T ₃ elapses and the main current stops is hereinafter referred to as a “post heat period”. During the post-heat period, the welding current _{remains controlled to the set value I 2} , and the energization during this period continues heating the stud S and the base material W, improving the welding condition between the stud S and the base material W. ..

The process shown in the flowchart of FIG. 2 is an example, and the arc stud welding process performed by the control unit 144 is not limited to the above. For example, the output of the main current may be stopped immediately after the end of the welding period without providing step S12 (without providing the post heat period).

FIG. 3 is a time chart for explaining the arc stud welding process. FIG. 3A shows the operating state of the gun switch of the welding gun G. FIG. 3B shows the driving state of the welding gun G. FIG. 3C shows the operating state of the pilot current output unit 13. FIG. 3D shows the operating state of the main current output unit 12. FIG. (E) shows the waveform of the output current output from the welding power supply device 1. FIG. (F) shows a waveform in which ripple is omitted from the waveform of the output current. In FIG. 3C, the case where the set value I ₂ is less than the predetermined current value I ₀ and the welding time T ₂ is less than the predetermined time T ₀ is shown by a solid line, and the set value I ₂ is predetermined. The case where the current value I ₀ or more or the welding time T ₂ is the predetermined time T ₀ or more is indicated by a thick broken line.

First, a case where the set value I ₂ is less than the predetermined current value I ₀ and the welding time T ₂ is less than the predetermined time T ₀ will be described.

At time t1, the gun switch is pressed and turned on (see FIG. 3A) to start welding. At this time, the pilot current output unit 13 is turned on (see FIG. 3C), and the pilot current output is started. As a result, the output current becomes the set current I ₁ of the pilot current (see FIG. 3 (f)). This state is continued in a pilot period from time t1 to pilot time T ₁ is passed.

At time t2 at the end of the pilot period, the welding gun G is driven and turned on (see FIG. 3B), the main current output unit 12 is turned on (see FIG. 3D), and the main current Output has started. In slope period from the time t2 to the time t3 the slope time T ₄ has elapsed, the output current (welding current) from the set current I ₁ of the pilot current to the set value I _2, gradually increases (Fig. 3 (f) reference). After that, the output current (welding current) is fixed at the _{set value I 2 from the time t 2} to the time t 4 when the welding time T 2 elapses.

At time t4 at the end of the welding period, the welding gun G is turned off (see FIG. 3B), the pilot current output unit 13 is turned off (see FIG. 3C), and the pilot current output is stopped. Has been done. However, the output current (welding current) continues in the post-heat period from the time t4 to the _{elapse of the post-heat time T 3 while being controlled by the set value I 2} (see FIG. 3 (f)).

At time t5 at the end of the postheat period, the main current output unit 12 is turned off (see FIG. 3D), and the main current output is stopped. As a result, the output current becomes zero (see FIG. 3 (f)).

Next, a case where the set value I ₂ is the predetermined current value I ₀ or more, or the welding time T ₂ is the predetermined time T ₀ or more will be described.

Since the times t1 to t3 are the same as above, the description thereof will be omitted. At time t3 at the end of the slope period, the pilot current output unit 13 is turned off (see the thick broken line in FIG. 3C), and the pilot current output is stopped. However, the output current (welding current) _{remains controlled by the set value I 2} (see FIG. 3 (f)). After that, the same applies to time t5 as described above, so the description thereof will be omitted.

Next, the operation and effect of the welding power supply device 1 according to the present embodiment will be described.

According to this embodiment, the welding power supply device 1 does not have a DC reactor between the main current output unit 12 and the output terminal a. Therefore, the main current with a large ripple is output as it is without being smoothed. Since the main current fluctuates violently, there is a moment when the current value of the main current approaches "0" during the slope period. However, in the present embodiment, the control unit 144 outputs a pilot current having a ripple smaller than that of the main current by superimposing it on the main current during the slope period (see FIG. 3E). Therefore, the welding power supply device 1 can suppress that the current supplied to the arc becomes too small and suppress the occurrence of arc breakage.

Further, according to the present embodiment, when the set value I ₂ of the welding current is less than the predetermined current value I ₀ and the welding time T ₂ is less than the predetermined time T ₀ , the control unit 144 has a pilot current during the welding period. Is continued, and the pilot current is superimposed on the main current to output (see FIG. 3 (e)). Therefore, the welding power supply device 1 can suppress that the current supplied to the arc becomes too small and suppress the occurrence of arc breakage. Further, since the welding time T ₂ is less than the predetermined time T ₀ , the loss Wr at the resistance of the pilot current output unit 13 does not exceed the allowable loss. Therefore, it is possible to prevent the resistance of the pilot current output unit 13 from burning out.

_{Further, the control unit 144 stops the output of the pilot current when the set value I 2} of the welding current is equal to or higher than the predetermined current value I ₀ (see the thick broken line in FIG. 3C). Therefore, since the loss Wr at the resistance of the pilot current output unit 13 does not exceed the permissible loss, it is possible to prevent the resistance of the pilot current output unit 13 from burning. Further, since the set value I ₂ is equal to or higher than the predetermined current value I ₀ , the arc breakage hardly occurs. Further, the control unit 144 stops the output of the pilot current when the _{welding time T 2} is equal to or longer than the predetermined time T _0. Therefore, since the loss Wr at the resistance of the pilot current output unit 13 does not exceed the permissible loss, it is possible to prevent the resistance of the pilot current output unit 13 from burning. The set value I ₂ is less than the predetermined current value I ₀ (for example, 800 A), and the welding time T ₂ is longer than the predetermined time T ₀ (for example, 0.8 S) at the time of product inspection or ammeter calibration. Since the actual arc stud welding is not performed and it is not necessary to consider the arc breakage, no problem occurs even if the output of the pilot current is stopped.

Further, according to the present embodiment, the pilot current output unit 13 parallels a series circuit including a thyristor and a resistor between the input terminal and the output terminal (output terminal a of the welding power supply device 1) of the main current output unit 12. It is connected. Therefore, the pilot current output unit 13 can be made into a simple circuit as compared with the case where a constant current circuit is separately provided, which contributes to the reduction in size and weight and the cost reduction of the welding power supply device 1.

In the present embodiment, is controlled and when the set value I ₂ is the predetermined current value I ₀ or more, when the welding time T ₂ is the predetermined time T ₀ or more, the welding current set value I ₂ Although the case where the output of the pilot current is stopped at the timing (the timing when the slope period ends) has been described, the timing at which the output of the pilot current is stopped is not limited to this. The timing of stopping the output of the pilot current may be any timing of the period from the start of the output of the main current to the short circuit between the stud S and the base material W. For example, it may be any timing in the middle of the slope period (for example, a predetermined time after the start of the slope period), or at any timing after the end of the slope period (for example, a predetermined time after the end of the slope period). May be good. However, if the timing of stopping the output of the pilot current is too early, the arc may be cut off in the middle of the slope period. Further, if the timing of stopping the output of the pilot current is too late, the loss Wr in the resistor of the pilot current output unit 13 may exceed the allowable loss. Therefore, it is desirable to set the timing when the slope period ends.

In the present embodiment, the case where the DC reactor is not provided has been described, but the present invention is not limited to this, and the DC reactor may be connected between the main current output unit 12 and the output terminal a. Even in this case, if the inductance of the DC reactor is small, the main current fluctuates with ripples. Therefore, superimposing the pilot current on the main current is effective for further suppressing the occurrence of arc breakage.

[Modification example]
FIG. 4 is a time chart for explaining an arc stud welding process of a modified example of the welding power supply device 1. Since the hardware configuration of the modification is the same as that of the welding power supply device 1, illustration and description thereof will be omitted. In this modification, the welding time T ₂ and the predetermined time T ₀ are not compared in the arc stud welding process. As shown in FIG. 4, in the arc stud welding process of the modified example, when the set value I ₂ is less than the predetermined current value I ₀ (S6: NO) in _{step S6, the welding time T 2} and the predetermined time T ₀ The process proceeds to step S9 without making a comparison with.

Also in this modified example, since the control unit 144 superimposes the pilot current on the main current and outputs it during the slope period, it is possible to suppress the occurrence of arc breakage. Further, since the control unit 144 _{stops the output of the pilot current when the set value I 2} of the welding current is equal to or higher than the predetermined current value I _0, it is possible to prevent the resistance of the pilot current output unit 13 from burning. Further, since the set value I ₂ is equal to or higher than the predetermined current value I ₀ , the arc breakage hardly occurs. Further, when the set value I ₂ of the welding current is less than the predetermined current value I ₀ , the control unit 144 continues the output of the pilot current during the welding period and superimposes the pilot current on the main current to output the arc. Can be suppressed from occurring.

[Second Embodiment]
FIG. 5 is a diagram for explaining the welding power supply device 10 according to the second embodiment, and is a block diagram showing an overall configuration of an arc stud welding system including the welding power supply device 10. In the figure, the same or similar elements as the arc stud welding system (see FIG. 1) provided with the welding power supply device 1 according to the first embodiment are designated by the same reference numerals, and redundant description will be omitted.

The welding power supply device 10 according to the present embodiment has a different configuration of the pilot current output unit 13 from the welding power supply device 1 according to the first embodiment.

The transformer 11 according to the present embodiment further includes a secondary winding 115. The secondary winding 115 is an auxiliary winding for taking out single-phase alternating current, and is connected to the pilot current output unit 13. The secondary winding 115 outputs the taken out single-phase alternating current to the pilot current output unit 13.

The pilot current output unit 13 according to the present embodiment includes a constant current circuit 131 and a switch 132. The constant current circuit 131 converts the single-phase AC input from the secondary winding 115 into _{a DC current of the set current I 1} and outputs it as a pilot current via the output terminals a and b. The internal configuration of the constant current circuit 131 is not limited, and a commonly known constant current circuit is used. The switch 132 is arranged on a power line connecting the secondary winding 115 and the constant current circuit 131, and switches between a state in which single-phase alternating current is input to the constant current circuit 131 and a state in which it is not input. When the control device 14 inputs a control signal for turning on the switch 132, the pilot current output unit 13 inputs a single-phase alternating current from the secondary winding 115 and outputs the pilot current. On the other hand, when the control signal for turning off the switch 132 is input from the control device 14, the single-phase alternating current is not input from the secondary winding 115 and the pilot current is not output. Unlike the pilot current output unit 13 according to the first embodiment, the pilot current output unit 13 does not have a resistor, so that it is not necessary to consider the burnout of the resistor. Therefore, the control device 14 (control unit 144 (not shown) performs the arc stud welding process (see FIG. 4) according to the modified example of the first embodiment. The configuration of the pilot current output unit 13 is not limited. The pilot current output unit 13 may be capable of controlling the start and stop of the pilot current output according to the control signal input from the control device 14.

Also in the present embodiment, since the control unit 144 superimposes the pilot current on the main current and outputs it during the slope period, it is possible to suppress the occurrence of arc breakage. Further, when the set value I ₂ of the welding current is less than the predetermined current value I ₀ , the control unit 144 continues the output of the pilot current during the welding period and superimposes the pilot current on the main current to output the arc. Can be suppressed from occurring. Further, the control unit 144 stops the output of the pilot current when _{the set value I 2} of the welding current is equal to or higher than the predetermined current value I _0. As a result, the load on the pilot current output unit 13 can be reduced in a large current region where arc breakage is unlikely to occur.

The welding power supply device according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the welding power supply device according to the present invention can be freely redesigned.

1,10: Welding power supply, 12: Main current output, 13: Pilot current output, 141: Welding current setting, 142: Welding time setting, 144: Control, S: Stud, W: Base material

Claims (5)

A welding power supply that outputs a welding current for arc stud welding that welds studs to the base metal.
A main current output unit that has a thyristor and outputs a main current that is a direct current,
A pilot current output unit that starts outputting a pilot current, which is a direct current, at the start of welding, and continues to output the pilot current even after the main current output unit starts outputting the main current.
A welding current setting unit that sets the welding current setting value, and a welding current setting unit.
When the set value is equal to or greater than a predetermined current value, the pilot current output unit sends the main current output unit during the period from when the main current output unit starts outputting the main current until the stud and the base material are short-circuited. A control unit that stops the output of the pilot current,
Welding power supply equipped with. The control unit controls the welding current so as to increase from the pilot current to the set value, and stops the output of the pilot current at the timing of controlling the welding current to the set value.
The welding power supply device according to claim 1. When the set value is less than the predetermined current value, the control unit stops the output of the pilot current when the stud and the base material are short-circuited.
The welding power supply device according to claim 1 or 2. Further, a welding time setting unit for setting a welding time from the start of output of the main current to the short circuit between the stud and the base metal is provided.
When the welding time is equal to or longer than a predetermined time, the control unit has the pilot current during the period from when the main current output unit starts to output the main current until the stud and the base material are short-circuited. Stop the output of
The welding power supply device according to claim 1 or 2. The main current output unit includes an input terminal for inputting an alternating current and an output terminal for outputting the main current.
The pilot current output unit includes a thyristor and a resistor connected between the input terminal and the output terminal and connected in series with each other.
The welding power supply device according to any one of claims 1 to 4.

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