JP4879618B2 - Consumable electrode arc welding machine. - Google Patents

Description

  The present invention relates to a consumable electrode arc welder, and more particularly to improvement of arc startability at the start of welding.

  In the arc start of an arc welder using a consumable electrode, a small arc is generated at the same time as the consumable electrode contacts the work piece, and this grows and shifts to a steady welding arc. At this time, in order to perform the arc start smoothly, the rising speed of the start current at the time of the arc start needs to be sufficiently high.

  FIG. 7 is an electrical connection diagram of a conventional consumable electrode arc welder with improved arc start. In the figure, the AC power supply AC is a single-phase commercial AC or a three-phase commercial AC power. Primary rectifier circuit DR1 converts an alternating voltage from alternating current power supply AC into a direct current and outputs the direct current. The smoothing capacitor C1 smoothes the output of the primary rectifier circuit DR1. The inverter circuit INV converts the output of the smoothing capacitor C1 into a high frequency pulse voltage and outputs it. The transformer INT converts the high-frequency pulse voltage into a voltage suitable for arc machining and outputs it. The secondary rectifier circuit DR2 converts the output of the transformer INT into a direct current and outputs it.

  Reactor DCL limits an excessive current at the time of a short-circuit arc, warms up a rapid change in current, controls the arc phenomenon, and at the time of re-arcing, releases energy stored at the time of a short-circuit to prevent arc break. The thyristor SCR has an anode connected to the intermediate terminal of the reactor DCL and a cathode connected to the output terminal to conduct at the arc start.

  The voltage detection circuit VD detects the welding voltage Vw and outputs it as a welding voltage detection signal Vd. The voltage error amplification circuit EV performs error amplification on the voltage setting signal Vr set by the voltage setting circuit VR and the welding voltage detection signal Vd, and outputs a voltage error amplification signal Ev.

  The current detection circuit ID detects the welding current Iw and outputs it as a welding current detection signal Id. The current error amplification circuit EI performs error amplification on the current setting signal Ir set by the current setting circuit IR and the welding current detection signal Id, and outputs a current error amplification signal Ei.

  The main control circuit SC starts operation in response to the welding start signal Ts from the torch switch TS, and based on the voltage error amplification signal Ev and the current error amplification signal Ei, the inverter control signal In, the motor control signal Mc, and the drive signal Td is output.

  The thyristor drive circuit SR converts the drive signal Td output from the main control circuit SC into a signal for surely firing the thyristor SCR, and outputs it as a thyristor drive signal Sr.

  Reference numeral 1 denotes a welding torch, 2 denotes a workpiece, 3 denotes a feed roll, and 4 denotes a welding wire (consumable electrode).

  FIG. 8 is a waveform diagram for explaining the operation of the conventional consumable electrode arc welder shown in FIG. In the same figure, (A) shows the welding start signal Ts, (B) shows the welding voltage detection signal Vd, (C) shows the welding current detection signal Id, and (D) ) Shows the drive signal Td, FIG. 5E shows the thyristor drive signal Sr, and FIG. 4F shows the inter-terminal voltage Dv between the intermediate terminal and the output terminal of the reactor.

  At time t = t1 shown in FIG. 8A, when the torch switch TS is pressed and the welding start signal Ts becomes a high level, the main control circuit SC starts operation, and the inverter control signal In and the motor control signal Mc And the drive signal Td is output.

  The inverter circuit INV operates in response to the inverter control signal In, and a no-load voltage is output during a period from time t = t1 to t2 when the welding wire 4 contacts the workpiece 2.

  The thyristor drive circuit SR converts the drive signal Td output from the main control circuit SC into a thyristor drive signal Sr shown in FIG. 8E in which the thyristor SCR is reliably fired, and outputs the thyristor drive signal Sr.

  At time t = t2, the welding wire 4 contacts the work piece 2. At this time, the thyristor element SCR has already been turned on by the thyristor drive signal Sr shown in FIG. 8E, so that the intermediate terminal and the output terminal of the reactor DCL are short-circuited by the thyristor element SCR. Further, the position of the intermediate terminal is provided at a point where L1 ≦ L2 when the inductance value of the input terminal and the intermediate terminal is (L1) and the inductance value of the intermediate terminal and the output terminal is (L2), and the reactor DCL When the intermediate terminal and the output terminal are short-circuited, the inductance value of the reactor DCL rises only to L1, and the welding current detection signal Id rises relatively steeply as shown in FIG. 8C.

  In addition, since the input terminal, the output terminal, and the intermediate terminal of the reactor DCL are wound around the same iron core, an alternating voltage is excited between the output terminal and the intermediate terminal by the voltage between the intermediate terminal and the input terminal. Therefore, at time t = t4, as shown in FIG. 8F, the thyristor element SCR is reverse-biased and automatically becomes non-conductive.

  As described above, the anode side of the thyristor SCR is connected to the intermediate terminal of the reactor DCL, the cathode side of the thyristor SCR is connected to the output terminal, the thyristor SCR is conducted at the time of arc start, and the reactor DCL is short-circuited. A method for improving this is proposed. (For example, Patent Document 1)

JP 55-36048 A

  In a consumable electrode type arc welder, since the inductance value of the reactor provided in the output path in the welding power source is large at the time of arc start, the rise of the arc start current is delayed and the arc start performance is deteriorated. In the prior art, in order to improve arc arc startability, an arc terminal in which a welding wire is in contact with an object to be welded by providing an intermediate terminal in the reactor and a thyristor element in parallel between the output terminal and the intermediate terminal of the reactor. At the start, the thyristor element is made conductive, the intermediate terminal of the reactor and the output terminal are short-circuited, the inductance value is reduced, and the start current rises quickly.

  However, since the thyristor element cannot be shut off by itself, the counter electromotive voltage generated between the intermediate terminal of the reactor and the input terminal is applied between the anode and the cathode of the thyristor element to cut off. Therefore, when the thyristor element is used, only the intermediate terminal and the output terminal of the reactor are short-circuited, and the start current rises sufficiently due to the influence of the reactance value between the input terminal and the intermediate terminal of the reactor that is not short-circuited. However, there was a limit to the improvement of arc start performance.

  Then, in this invention, it is providing the consumable electrode type arc welding machine which can solve the subject mentioned above.

In order to solve the above-described problem, a first invention is a consumable electrode arc welding machine that supplies an output between a consumable electrode and an object to be welded via a reactor provided in an output path in a welding power source. An arc start circuit formed by connecting a source side of a switching element and an anode side of a diode in series, connecting a drain side of the switching element to an input terminal of the reactor, and connecting a cathode side of the diode to an output terminal of the reactor When the welding start signal is input, the switching element is turned on, and a high-current start current is passed between the consumable electrode and the workpiece to be welded for a predetermined time, and then the start-up current is ended. then the Sui when energization of transition to the initial current to an initial current of low current to shift the welding current of the terminated larger constant than the initial current The arc start control circuit for interrupting the quenching device is a consumable electrode arc welding machine, characterized by comprising.

According to a second aspect of the present invention, the arc start control circuit provides a predetermined fall time when the energization of the start current is finished and the transition to the low current initial current is performed. This is a consumable electrode type arc welding machine.

  According to the first aspect of the invention, the switching element is connected in parallel between the input terminal and the output terminal of the reactor, and the reactor is short-circuited by conducting the switching element at the time of arc start, so that the inductance value of the reactor at the time of arc start Is small, the start current rises sharply, and the arc start performance is improved. Further, since the switching element is cut off when the start of the switching element is cut off and the start current is turned on and the low-current initial current is turned on, the surge voltage due to the interruption is lowered to prevent the switching element from deteriorating.

  According to the second invention, when the low current initial current is further lowered when shifting from the high current start current to the low current initial current, the reactor is short-circuited by the switching element and the inductance value is small. When transitioning to current, the current may suddenly decrease, causing a current drop and causing an arc break. However, when a predetermined fall time is provided at the time of transition from the start current to the initial current and the start current is gradually decreased, the current drop is reduced, and the transition from the start current to the initial current is performed smoothly.

  According to the third aspect of the invention, the switching element is cut off when the transition of the steady welding current larger than the initial current is started, so that the switching element is cut off when the inverter circuit is operating at the maximum pulse width. The current drop due to this interruption is reduced by the current supplied through the reactor, and arc breakage is prevented.

[Embodiment 1]
FIG. 1 is an electrical connection diagram of a consumable electrode arc welder according to Embodiment 1 of the present invention. In the figure, components having the same reference numerals as those in the electrical connection diagram of the consumable electrode arc welder of the prior art shown in FIG. 6 perform the same operations, and therefore description thereof will be omitted, and only components having different reference numerals will be described.

  In the electrical connection diagram of the consumable electrode arc welder shown in FIG. 1, the arc start circuit ST is formed by a switching element (eg, IGBT) TR and a diode D1, and the drain side of the switching element TR is connected to the input terminal of the reactor DCL. The cathode side of the diode D1 is connected to the output terminal. Since the switching element (IGBT) has a low reverse voltage withstand voltage, a protective diode D2 is generally provided inside the module. If reactor DCL is short-circuited or short-circuit canceled only by this switching element TR, the energy charged in reactor DCL at the time of short-circuit cancellation is returned by protection diode D2 provided in the switching element, and the energy cannot be charged sufficiently. Therefore, by providing the diode D1 in series with the switching element TR, the reflux of the energy of the reactor DCL is prevented.

  FIG. 2 is a detailed diagram of the arc start control circuit SE shown in FIG. 1, and is formed by a flip-flop circuit FF, a current comparison circuit IC, a reference current setting circuit IRF, a timer circuit TM, and an OR logic circuit OR.

  The current comparison circuit IC compares the predetermined reference current set value Irf and the welding current detection signal Id, and when the reference current set value Irf becomes higher than the reference current set value Irf, outputs the current comparison signal Ic at the low level.

  The flip-flop circuit FF is set at the rising edge of the drive signal Td and outputs an output at a high level, and is reset at the rising edge of the current comparison signal Ic to set the output at a low level. At this time, reset is prohibited during a period in which the drive signal Td, which is a set signal, is at a high level.

  The timer circuit TM outputs a timer signal Tm having a predetermined time in response to the fall of the flip-flop signal Ff.

  FIG. 3 is a waveform diagram for explaining the operation of the consumable electrode arc welder according to Embodiment 1 of the present invention. In the same figure, (A) shows the welding start signal Ts, (B) shows the drive signal Td, (C) shows the welding voltage detection signal Vd, and (D) shows the welding. FIG. 8E shows the current comparison signal Ic, FIG. 9F shows the flip-flop signal Ff, FIG. 10J shows the timer signal Tm, and FIG. Indicates an arc start control signal Se.

  Next, the operation of the consumable electrode arc welder according to the first embodiment will be described using the above waveform diagram. When the welding start signal Ts is output from the torch switch TS at the time t = t1 shown in FIG. 3A and becomes High level, the main control circuit SC starts operation in accordance with the welding start signal Ts. The drive signal Td shown in (B), the inverter control signal In (not shown), and the motor control signal Mc are output.

  In the flip-flop circuit FF shown in FIG. 2, the drive signal Td is input to the set terminal, and the flip-flop signal Ff shown in FIG. 3 (F) is set to High level in response to the rise of the drive signal Td to the OR logic circuit OR. Output. The OR logic circuit OR performs the OR logic and outputs the arc start control signal Se shown in FIG. In the arc start circuit ST shown in FIG. 1, when the arc start control signal Se is at a high level, the switching element TR is turned on to short-circuit the reactor DCL.

  The inverter circuit INV operates in response to the inverter control signal In, and a no-load voltage is output during the period of time t = t1 to t2 until the welding wire 4 contacts the workpiece 2 and the voltage detection circuit VD. Detects a no-load voltage and outputs it as a welding voltage detection signal Vd shown in FIG.

  When the welding wire 4 contacts the workpiece 2 at time t = t2, a start current is energized. At this time, switching element TR is already in a conducting state by arc start control signal Se shown in FIG. 3 (H), and reactor DCL is short-circuited. Therefore, the start current rises sharply as shown in FIG. 3D without being affected by the inductance of the reactor DCL, so that an arc is easily generated.

  The current comparison circuit IC compares the reference current set value Irf with the welding current detection signal Id and determines that the start current is energized when the reference current set value Irf becomes higher at time t = t3, and determines the current comparison signal Ic. Output at Low level.

  At time t = t4, the start current is limited to a predetermined value (for example, about 500 A), and the start current is continued (for example, about 5 ms). Subsequently, when the energization of the start current is completed at time t = t5 and the transition to a low-current initial current (for example, about 50 A) is made, the reactor DCL is short-circuited by the switching element TR and the inductance value is small. A current drop (not shown) occurs. At this time, as shown in FIG. 3D, if the current falls slowly by providing a predetermined fall time T1 (for example, about 1 ms), the current drop becomes smaller, and the initial current is reduced from the start current. Transition is smooth. Furthermore, even if the initial current (for example, about 50 A) is made smaller, the initial current can be transferred from the start current.

  At time t = t6, the current comparison circuit IC compares the reference current set value Irf with the welding current detection signal Id again and determines that the current has shifted from the start current to the initial current when the reference current set value Irf is lower than the reference current set value Irf. The current comparison signal Ic is set to High level and output. Further, the low current initial current is obtained by forming the tip of the welding wire burned up by the high current start current during a period from time t = t7 to t9, and a steady welding current at time t = t9 when the forming is finished. Migrate to

  In the flip-flop circuit FF, the current comparison signal Ic shown in FIG. 3E is input to the reset terminal, and the flip-flop signal Ff shown in FIG. 3F is set to the Low level in response to the rising of the current comparison signal Ic. Output. Subsequently, the timer circuit TM outputs a timer signal Tm having a predetermined time according to the falling edge of the flip-flop signal Ff.

  The OR logic circuit OR performs the OR logic of the flip-flop signal Ff shown in FIG. 3 (F) and the timer signal Tm shown in FIG. 3 (J), and sets the arc start control signal Se to the low level at time t = t8. Output. When the arc start control signal Se becomes a low level, the switching element TR is cut off and the short circuit of the reactor DCL is completed. At this time, since the switching element TR is cut off when a low initial current is energized, the surge voltage due to the cut-off is lowered, and deterioration of the switching element can be prevented.

[Embodiment 2]
FIG. 4 is a detailed view of the second arc start control circuit SE2 according to the second embodiment. In the figure, components having the same reference numerals as those of the arc start control circuit SE of the first embodiment shown in FIG. Therefore, description thereof is omitted, and only components having different reference numerals will be described.

  The second arc start control circuit SE2 shown in FIG. 4 includes a flip-flop circuit FF, a current comparison circuit IC, a reference current setting circuit IRF, a second flip-flop circuit FF2, a second current comparison circuit IC2, and a second reference. It is formed by a current setting circuit IRF2 and an OR logic circuit OR.

  The second current comparison circuit IC2 compares the predetermined second reference current set value Irf2 with the welding current detection signal Id, and if it becomes higher than the second reference current set value Irf2, the second current comparison signal Ic2 is output. Output at High level.

  The second flip-flop circuit FF2 is set at the rising edge of the flip-flop signal Ff and outputs the output at the High level, and is reset at the rising edge of the second current comparison signal Ic2, and the output is set at the Low level. At this time, reset is prohibited while the flip-flop signal Ff, which is a set signal, is at a high level.

  The OR circuit OR performs an OR logic of the flip-flop signal Ff and the second flip-flop signal Ff2 and outputs the result as a second arc start control signal Se2.

  FIG. 5 is a waveform diagram for explaining the operation of the consumable electrode arc welder according to the second embodiment. In the same figure, (A) shows the welding start signal Ts, (B) shows the drive signal Td, (C) shows the welding voltage detection signal Vd, and (D) shows the welding. FIG. 8E shows the current comparison signal Ic, FIG. 10F shows the flip-flop signal Ff, FIG. 10G shows the second current comparison signal Ic2, and FIG. (H) shows the second flip-flop signal Ff2, and (I) shows the second arc start control signal Se2.

  Next, the operation of the consumable electrode arc welder according to the second embodiment will be described using the above waveform diagram. In FIG. 5, during the period from time t = t1 to t3, the same operation as the operation waveform diagram of the first embodiment shown in FIG.

  The second current comparison circuit IC2 compares the predetermined second reference current set value Irf2 with the welding current detection signal Id, and at time t = t31 when the second reference current set value Irf2 becomes higher than the second reference current set value Irf2. Current comparison signal Ic2 is set to High level and output.

  At time t = t4, the start current is limited to a predetermined value and continued. Subsequently, the energization of the start current ends at time t = t5, and a predetermined fall time T1 is provided when shifting to the low current initial current so that the current is gradually reduced.

  The second current comparison circuit IC2 compares the second reference current set value Irf2 with the welding current detection signal Id, and at time t = t51 when it becomes lower than the second reference current set value Irf2, FIG. The second current comparison signal Ic2 shown in FIG.

  At time t = t6, the current comparison circuit IC compares the reference current set value Irf and the welding current detection signal Id again and determines that the current has substantially shifted from the start current to the initial current when the reference current set value Irf is lower than the reference current set value Irf. The current comparison signal Ic is set to High level and output.

  The flip-flop circuit FF receives the current comparison signal Ic at the reset terminal, and outputs the flip-flop signal Ff shown in FIG. 5F at the Low level in response to the rising of the current comparison signal Ic.

  At time t = t10, the second current comparison circuit IC2 compares the second reference current set value Irf2 with the welding current detection signal Id again and becomes higher than the second reference current set value Irf2, from the start current. The second current comparison signal Ic2 is set to a high level and output after determining that the current state has shifted to a steady welding current.

  In the second flip-flop circuit FF2, the second current comparison signal Ic2 is input to the reset terminal, and the second flip-flop signal Ff2 shown in FIG. 5H is displayed in response to the rising of the second current comparison signal Ic2. Is set to Low level and output. The OR logic circuit OR performs the OR logic of the flip-flop signal Ff shown in FIG. 5F and the second flip-flop signal Ff2 shown in FIG. 5H, and performs the second arc start control at time t = t10. The signal Se2 is set to Low level and output.

When shifting to a steady welding current larger than the initial current, the main control circuit SC operates the inverter circuit INV with the maximum pulse width in order to cope with a sharp increase in the welding current.
At this time, if the switching element TR is interrupted, the switching element TR is interrupted when the inverter circuit INV is operating at the maximum pulse width, and the current drop due to the interruption is supplemented by a steep current supplied via the reactor. As a result, the current drop is reduced, and arc interruption due to the interruption of the switching element TR is prevented.

[Embodiment 3]
FIG. 6 is an electrical connection diagram of a consumable electrode arc welder that performs AC pulsed MIG welding. In the same figure, FIG. 1 is the same as the electrical connection diagram of the consumable electrode arc welder according to the first embodiment of the present invention, and the same reference numerals perform the same operation, so the description thereof is omitted and the reference numerals are different. Only explain

  The secondary-side inverter circuit INV2 shown in FIG. 6 is provided on the output side of the reactor DCL, and the low-frequency (for example, 50 to 200 Hz) necessary for the AC pulse MIG is an output smoothed to a direct current by the secondary rectifier circuit DR2 and the reactor DCL. ) To generate an AC arc.

  Other circuit configurations except the secondary inverter circuit INV2 described above are the same as the electrical connection diagram of the consumable electrode arc welder according to the first embodiment shown in FIG. Therefore, the means for starting the arc by making the switching element conductive at the time of arc start and shorting the reactor and making the start current rise steep is also effective in a consumable electrode arc welder that performs AC pulse MIG welding. Is a good starting point.

It is an electrical connection diagram of the consumable electrode type arc welder according to Embodiment 1 of the present invention. FIG. 2 is a detailed view of an arc start control circuit shown in FIG. 1. FIG. 6 is a waveform diagram for explaining the operation of the first embodiment. 6 is a detailed diagram of a second arc start control circuit according to Embodiment 2. FIG. FIG. 6 is a waveform diagram for explaining the operation of the second embodiment. 6 is an electrical connection diagram of a consumable electrode arc welder according to Embodiment 3. FIG. It is an electrical connection diagram of the consumable electrode type arc welding machine of a prior art. It is a wave form diagram explaining operation | movement of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding torch 2 Work piece 3 Wire feed motor 4 Welding wire C1 Smoothing capacitor D1 Diode D2 Protection diode DCL Reactor DR1 Primary rectifier circuit DR2 Secondary rectifier circuit EI Current error amplifier circuit Ei Current error amplifier signal EV Voltage error amplifier circuit Ev voltage error amplification signal FF flip-flop circuit FF2 second flip-flop circuit Ff flip-flop signal Ff2 second flip-flop signal IC current comparison circuit IC2 second current comparison circuit Ic current comparison signal Ic2 second current comparison signal ID Current detection circuit Id Output current detection circuit IR current setting circuit Ir current setting signal IRF reference current setting circuit IRF2 second reference current setting circuit Irf reference current setting value (signal)
Irf2 Second reference current set value (signal)
Ir Current setting signal In Inverter control signal INT Transformer INV Inverter circuit INV2 Secondary side inverter circuit Mc Motor control circuit OR OR logic circuit SC Main control circuit SE Arc start control circuit SE2 Second arc start control circuit Se Arc start control signal Se2 Second arc start control signal SR Thyristor drive circuit Sr Thyristor drive signal ST Arc start circuit SCR Thyristor element TM Timer circuit Tm Timer signal TS Torch switch TR Switching element Td Drive signal VD Voltage detection circuit Vd Output welding voltage detection signal VR Voltage Setting circuit Vr Voltage setting signal

Claims (2)

In a consumable electrode arc welding machine that supplies power between a consumable electrode and an object to be welded via a reactor provided in the output path in the welding power source, the source side of the switching element and the anode side of the diode are connected in series. An arc start circuit in which a drain side of the switching element is connected to an input terminal of the reactor and a cathode side of the diode is connected to an output terminal of the reactor, and the switching element is connected when a welding start signal is input. A high current start current is applied between the consumable electrode and the workpiece to be welded for a predetermined period of time, and then when the start current application is completed, a transition is made to a low current initial current and the initial current supply is performed. arc start control circuit for interrupting the switching device when completed moves to the welding current of greater constant than the initial current The consumable electrode arc welding machine, characterized by comprising. 2. The consumable electrode arc welding according to claim 1, wherein the arc start control circuit provides a predetermined fall time when energization of the start current is completed and transition to the low current initial current is performed. Machine.

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