JP2022042308A - Welding device - Google Patents

Abstract

To solve a problem in which both of resistance and a transistor are needed in order to reduce welding currents at a time point when a constriction is detected, which makes downsizing difficult.SOLUTION: A welding device comprises: a welding power source part PM that outputs welding currents Iw for performing consumable electrode-type arc-welding; a constriction detecting part ND that detects a constriction of molten metal caused at a tip of a welding wire 1 during short-circuit; a transistor TR provided on a current-carrying passage of the welding currents Iw; and a driving part DR that drives the transistor TR by a detection signal Nd of the constriction detecting part ND. When the constriction detecting part ND detects the constriction, the driving part DR drives the transistor TR in an active area to reduce the welding currents Iw.SELECTED DRAWING: Figure 1

Description

The present invention relates to a welding apparatus that reduces a welding current and regenerates an arc when a droplet constriction is detected.

In the inventions of Patent Documents 1 and 2, in the consumable electrode type arc welding in which an arc and a short-circuited state are repeated between the welding wire and the base metal, the constriction of droplets, which is a precursory phenomenon in which the arc is regenerated from the short-circuited state, is detected and constricted. It is described that the welding current is reduced at the time when the above is detected and the arc is regenerated in the state of a small current to reduce the amount of spatter generated.

Patent Gazette No. 5950747 Patent Gazette No. 4907892

Patent Documents 1 and 2 provide a method of reducing the welding current when a constriction is detected by connecting a resistor in parallel with the switching element and turning off the switching element. .. However, a resistor connected in parallel to the switching element and the switching element is required, and there is a problem that the device cannot be miniaturized and the cost cannot be reduced.

An object of the present invention is to provide a welding apparatus capable of downsizing and reducing the cost of a circuit that reduces a welding current when a constriction is detected.

In order to solve the above-mentioned problems, the invention of claim 1 is
Welding power supply unit that outputs welding current for performing consumable electrode type arc welding,
A constriction detector that detects the constriction of molten metal that occurs at the tip of the weld wire during the short-circuit period,
A transistor provided in the current-carrying path of the welding current and
A drive unit that drives the transistor by the detection signal of the constriction detection unit, and
Equipped with
When the constriction detecting unit detects a constriction, the driving unit drives the transistor in the active region to reduce the welding current.
It is a welding device characterized by this.

The invention of claim 2 is
The period during which the driving unit drives the transistor in the active region is a period from the time when the constriction detecting unit detects the constriction to the time when the welding current drops to a predetermined value.
The welding apparatus according to claim 1.

The invention of claim 3 is
The drive unit drives the transistor in the saturation region during a period other than the period in which the transistor is driven in the active region.
The welding apparatus according to claim 1 and 2.

According to the present invention, since the resistance connected in parallel to the switching element can be omitted, it is possible to reduce the size and cost of the circuit that reduces the welding current when the constriction is detected.

It is a connection diagram of the welding apparatus which concerns on embodiment of this invention, and is a block diagram of each function. It is a timing chart which shows the operation at the time of short circuit of the welding apparatus which concerns on embodiment of this invention.

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

FIG. 1 is a connection diagram of a welding apparatus according to an embodiment of the present invention and a block diagram of each function. Hereinafter, each block will be described with reference to the figure.

The welding power supply circuit PM receives a commercial power supply (not shown) such as three-phase 200V as an input, performs output control by inverter control or the like according to an error amplification signal Ea described later, and outputs an output voltage E. Although not shown, this welded power supply circuit PM is driven by a primary rectifier that rectifies a commercial power supply, a smoothing capacitor that smoothes the rectified DC, and the above-mentioned error amplification signal Ea that converts the smoothed DC into high-frequency AC. It is equipped with an inverter circuit, a high-frequency transformer that steps down high-frequency AC to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency AC to DC.

The reactor WL smoothes the welding current Iw and maintains a stable arc 3.

The feed motor WM feeds the welding wire 1 at a constant feed rate Fw by inputting a feed control signal Fc from the welding power supply circuit PM.

The welding wire 1 is fed in the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the feeding tip (not shown) in the welding torch 4 and the base metal 2, and the welding current Iw is energized. Shielding gas (not shown) is ejected from the tip of the welding torch 4 to shield the arc 3 from the atmosphere.

The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E, and outputs an output voltage detection signal Ed.

The voltage error amplification circuit EV takes the above-mentioned output voltage setting signal Er and the above-mentioned output voltage detection signal Ed as inputs, and amplifies the error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (-). , The voltage error amplification signal Ev is output.

The current detection circuit ID detects the above welding current Iw and outputs a current detection signal Id. The welding voltage detection circuit VD detects the above welding voltage Vw and outputs a welding voltage detection signal Vd. The short-circuit discrimination circuit SD receives the above welding voltage detection signal Vd as an input, and when this value is less than the predetermined short-circuit discrimination value (about 10V), it determines that it is in the short-circuit period and becomes the High level, and the short-circuit discrimination value is reached. In the above case, the short-circuit discrimination signal Sd, which is determined to be in the arc period and becomes the Low level, is output.

The current setting circuit IR outputs as a current setting signal Ir during the short circuit period.

The current error amplification circuit EI amplifies the error between the current setting signal Ir (+) and the current detection signal Id (-) by using the above current setting signal Ir and the above current detection signal Id as inputs, and amplifies the current error. The signal Ei is output.

The power supply characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the short circuit discrimination signal Sd as inputs, performs the following processing, and outputs the error amplification signal Ea.
1) During the short-circuit period from the time when the short-circuit discrimination signal Sd changes to the High level (short-circuit period) to the time when the short-circuit discrimination signal Sd changes to the Low level (arc period), the current error amplification signal Ei is used as an error amplification signal. Output as Ea.
2) During the arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
By this circuit, the characteristics of the welding power supply during the short-circuit period become the constant current characteristic, and the characteristics of the welding power supply become the constant voltage characteristic during the other period.

The constriction detection circuit ND receives the above-mentioned short-circuit discrimination signal Sd, the above-mentioned welding voltage detection signal Vd, and the above-mentioned current detection signal Id as inputs, and the short-circuit discrimination signal Sd is a welding voltage detection signal at the High level (short-circuit period). When the voltage rise value of Vd reaches the reference value, it is determined that the constriction formation state has reached the reference state and becomes the High level, and when the short circuit determination signal Sd changes to the Low level (arc period), it becomes the Low level. The constriction detection signal Nd is output. Further, the constriction detection signal Nd may be changed to the High level when the differential value of the welding voltage detection signal Vd during the short-circuit period reaches the corresponding reference value. Further, the resistance value of the droplet is calculated by dividing the value of the welding voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of this resistance value reaches the corresponding reference value, the constriction detection signal Nd May be changed to High level.

The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM takes the low level current setting signal Ilr and the current detection signal Id as inputs, and outputs a current comparison signal Cm that becomes High level when Id <Ilr and Low level when Id ≧ Ilr. ..

In the transistor TR, the collector terminal c is connected to the reactor WL and the emitter terminal e is connected to the welding torch 4. When the constriction is detected and the welding current Iw is reduced by the drive circuit DR described later, the active region is used. It operates in the saturation region for the rest of the period. As the transistor TR, a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is used.

The on-voltage detector VCE measures the voltage between the emitter terminal e (−) and the collector terminal c (+) of the transistor TR, and outputs the on-voltage signal Vce.

The on-resistance measuring instrument RCE divides the on-voltage signal Vce measured by the on-voltage detector VCE by the current detection signal Id measured by the current detection circuit ID, and divides the on-voltage signal Vce between the emitter terminal e and the collector terminal c of the transistor TR. Calculate Rce.

The drive circuit DR uses the on-resistance Rce calculated by the on-resistance measuring instrument RCE, the current comparison signal Cm of the current comparison circuit CM, and the constriction detection signal Nd of the constriction detection circuit ND as inputs, and inputs the gate terminal g of the transistor TR as shown below. The gate signal Dr to be driven is output.
1) When the constriction detection signal Nd is Low, the gate signal Dr that drives the gate terminal g of the transistor TR is output so that the on-resistance Rce of the transistor TR becomes almost zero, and the transistor TR is driven in the saturation region.
2) When the constriction detection signal Nd is High and the current comparison signal Cm is Low, the gate signal Dr that drives the gate terminal g of the transistor TR is output so that the on-resistance Rce of the transistor TR becomes a predetermined value, and the transistor is output. Drive the TR in the active region. The predetermined value of the on-resistance Rce is appropriately in the range of 0.5Ω to 3Ω, and in the present embodiment, the on-resistance Rce is 0.8Ω.
3) When the constriction detection signal Nd is High and the current comparison signal Cm is High, the gate signal Dr that drives the gate terminal g of the transistor TR is output so that the on-resistance Rce of the transistor TR becomes almost zero. The transistor TR is driven in the saturation region.
Therefore, when the constriction is detected, this drive signal Dr is driven in the active region so that the on-resistance Rce of the transistor TR becomes a predetermined value, and the on-resistance Rce of the transistor TR is inserted into the current-carrying path. The welding current Iw decreases sharply. Then, when the value of the rapidly reduced welding current Iw decreases to the value of the low level current setting signal Ilr, the drive signal Dr is driven in the active region so that the on-resistance Rce of the transistor TR becomes almost zero, and the transistor TR is turned on. Since it will be in a state, it will return to the normal state.

FIG. 2 is a timing chart showing the operation of the welding apparatus according to the embodiment of the present invention when a short circuit occurs. The figure (A) shows the welding current Iw, the figure (B) shows the welding voltage Vw, the figure (C) shows the short circuit discrimination signal Sd, and the figure (D) shows the constriction signal Nd. FIG. (E) shows the current comparison signal Cm, FIG. (F) shows the Vce of the transistor TR, FIG. (G) shows the on-resistance Rce of the transistor TR, and FIG. show. Hereinafter, the operation of each signal will be described with reference to the figure.

t0: At time t0, the arc period is in progress, and as shown in FIG. 3C, the short-circuit determination signal Sd is Low. During this arc period, the tip of the welding wire 1 is melted to generate a molten metal ball, and the period is waiting for contact with the base metal 2.

t1 to t2: At time t1, the moment when the molten metal ball generated at the tip of the welding wire 1 comes into contact with the base metal 2, and as shown in FIG. .. During the initial time from t1 to t2, the initial current is suppressed to a low current in order to help the molten metal balls in contact with the base material 2 smoothly move to the base material 2. In the present embodiment, the initial time = 0.5 mS and the initial current = 40 A.

t2 to t3: During the period from time t2 to t3, as shown in FIG. maintain. As shown in FIG. 3B, the welding voltage Vw rises from the point where the welding current Iw reaches the peak value at the time of short circuit. This is because a constriction is gradually formed in the droplets at the tip of the welding wire 1 due to the action of the pinch force due to the welding current Iw. In the present embodiment, the short-circuit inclination = 180 A / mS and the short-circuit peak value = 400 A.

t3: At time t3, when the voltage rise value of the welding voltage Vw subsequently reaches the reference value, it is determined that the constriction formation state has reached the reference state, and as shown in FIG. Changes to the High level.

t3 to t4: In response to the constriction detection signal Nd reaching the High level at time t3, as shown in FIG. Since the signal is driven in the active region so as to be, as shown in FIG. 6 (G), the on-resistance Rce = 0.8Ω of the transistor TR, and the on-resistance Rce = 0.8Ω at the transistor TR in FIG. The resistance of is inserted into the current-carrying path. Therefore, as shown in FIG. 6A, the welding current Iw sharply decreases from the peak value at the time of short circuit to the low level current value Ilr. In this embodiment, the low level current value Ilr = 50A.

t4: When the welding current Iw decreases to the low level current value Ilr at time t4, the current comparison signal Cm switches from Low to High as shown in FIG. Then, as shown in FIG. 1 (E), the drive signal Dr returns to the signal that drives the transistor TR in the saturation region so that the on-resistance Rce ≈ 0Ω. Therefore, the transistor TR is turned on. The resistance 0.8Ω inserted in the current-carrying path is removed by the transistor TR of.

t4 to t5: At the tip of the welding wire 1 where the constriction has once occurred, even if the welding current Iw is reduced to the low level current value Ilr, the squeezing progresses at an accelerating rate due to the surface tension of the molten metal. As shown in the above, the welding voltage Vw decreases once at time t4 and then rises sharply until time t5 when the short circuit is switched to the arc.

t5: When an arc is generated at time t5, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. 3B. Therefore, as shown in FIG. Sd switches from High to Low. During the arc period when the short-circuit determination signal Sd is Low, the feedback control of the welding power supply is performed by the voltage error amplification signal Ev of FIG. 1, so that the constant voltage characteristic is obtained. Therefore, as shown in FIG. 6A, the value of the welding current Iw during the arc period changes depending on the arc load, and the tip of the welding wire 1 is melted again to generate a molten metal ball, which comes into contact with the base metal 2. It returns to the state of the time t0 waiting for.

As described above, in the present embodiment, by switching the transistor TR between the saturation region and the active region and driving the transistor TR, it is possible to omit the resistance connected in parallel to the switching element.

1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll CM Current comparison circuit Cm Current comparison signal DR Drive circuit Dr Drive signal E Output voltage Ea Error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EI Current error amplification Circuit Ei Current error amplification signal ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal Fc Feeding control signal Fw Feeding speed ID Current detection circuit Id Current detection signal ILR Low level current setting circuit Ilr Low level current setting signal IR Current setting circuit Ir Current setting signal Iw Welding current ND Constriction detection circuit Nd Constriction detection signal PM Welding power supply circuit RCE On-resistance measuring instrument Rce On-resistance SD Short-circuit discrimination circuit Sd Short-circuit discrimination signal SW Power supply characteristic switching circuit TR Transistor VCE On-voltage detector Vce On-voltage VD Welding voltage detection circuit Vd Welding voltage detection signal WL Reactor WM Feed motor

Claims (3)

Welding power supply unit that outputs welding current for performing consumable electrode type arc welding,
A constriction detector that detects the constriction of molten metal that occurs at the tip of the weld wire during the short-circuit period,
A transistor provided in the current-carrying path of the welding current and
A drive unit that drives the transistor by the detection signal of the constriction detection unit, and
Equipped with
When the constriction detecting unit detects a constriction, the driving unit drives the transistor in the active region to reduce the welding current.
Welding equipment characterized by that. The period during which the driving unit drives the transistor in the active region is a period from the time when the constriction detecting unit detects the constriction to the time when the welding current drops to a predetermined value.
The welding apparatus according to claim 1. The drive unit drives the transistor in the saturation region during a period other than the period in which the transistor is driven in the active region.
The welding apparatus according to claim 1 and 2.

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