JP2013043213A - Welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding device capable of achieving a stable growth of droplets and stable generation of an arc.SOLUTION: The welding device 100 includes an electric power supply circuit 102 and a power supply controller 104. The power supply controller 104 controls the electric power supply circuit 102 such that a high level current is output in a first arc period Ta1 in an initial period of an arc period subsequent to a short circuit period and an arc current corresponding to a constant voltage controlled welding voltage is output in a second arc period Ta2 in a latter period of the arc period. In addition, the power supply controller 104 controls the electric power supply circuit 102 to superimpose a repeatedly increasing and decreasing waveform on an amplitude center current so as to generate a high level current. Furthermore, the power supply controller 104 calculates a recommended voltage Vc corresponding to a current set value of a welding current and increases or decreases the amplitude center current Ihcr depending on a voltage difference between the recommended voltage Vc and a voltage set value Vr of a welding voltage. In this way, the arc is prevented from being unstable even when the voltage set value Vr is altered.

Description

  The present invention relates to a welding apparatus, and more particularly to a welding apparatus that performs carbon dioxide arc welding.

  Japanese Examined Patent Publication No. 4-4074 (Patent Document 1) discloses a consumable electrode type arc welding method in which a short circuit and arc generation are repeated between a consumable electrode and a base material. This consumable electrode type arc welding method repeats the process of forming a droplet and the process of transferring the droplet to a base material.

  FIG. 13 is a diagram for explaining a consumable electrode arc welding method that repeats short-circuiting and arc generation.

  Referring to FIG. 13, in the consumable electrode type arc welding method that repeats short-circuiting and arc generation, processes (a) to (f) described below are repeatedly executed in order. (A) Short-circuit initial state in which the droplet contacts the molten pool, (b) Short-circuit intermediate state in which the contact between the droplet and the molten pool is ensured and the droplet is transferred to the molten pool, (c) The droplet The short-circuit late state in which the constriction occurs in the droplet between the welding wire and the molten pool due to the transition to the molten pool side, (d) the state in which the short circuit is opened and the arc is generated, and (e) the end of the welding wire is Arc generation state in which molten droplets grow by melting, (f) Arc generation state immediately before droplets grow and short-circuit with the molten pool.

Japanese Patent Publication No. 4-4074 Japanese Patent No. 4702375

  In the conventional short circuit transfer welding disclosed in Japanese Examined Patent Publication No. 4-4074, arcs and short circuits occur regularly. However, when welding is performed by the carbon dioxide arc welding method at a high current (current exceeding 200 A when the diameter of the welding wire is 1.2 mm), in the globule transition accompanied by a short circuit, the droplets drop on the upper part of the wire due to the arc reaction force. As a result, the arc time is prolonged and it becomes difficult to generate periodic short circuits, and arcs and short circuits occur irregularly.

  As described above, when the cycle of the short circuit and the arc fluctuates irregularly, the droplet size at the time of the short circuit becomes indefinite and the alignment of the bead toe ends becomes worse.

  In addition, the high current causes an excessive arc force to act at irregular positions with respect to the molten pool, so that the molten pool is vibrated large and irregularly, and in particular, the pumping bead is pushed by pushing the molten pool to the side opposite to the welding direction. Is likely to occur.

  In particular, in order to improve productivity, it is required to increase the welding speed, and in high-speed welding, deterioration of the welding quality due to the influence of the above-mentioned problem appears remarkably. In order to increase the welding speed, it is necessary to increase the wire feeding speed in order to increase the unit welding amount. Accordingly, there is a relationship that the welding current increases.

  Further, many welding apparatuses have a function of automatically setting a recommended voltage (also referred to as a unitary voltage) when a set current or a wire feeding speed is set. On the other hand, the operator often sets the welding voltage to be different from the recommended voltage while looking at the quality of welding. However, if the set voltage is raised or lowered extremely with respect to the recommended voltage, the arc tends to become unstable.

  An object of the present invention is to provide a welding apparatus capable of realizing stable droplet growth and stable arc generation.

  In summary, the present invention provides a welding apparatus that uses carbon dioxide gas as a shielding gas and performs welding by a carbon dioxide arc welding method in which a short circuit state and an arc state are alternately repeated, and a voltage is applied between a torch and a base material. A power supply circuit for supplying power and a control unit for controlling the voltage of the power supply circuit. The control unit outputs a high-level current during the first arc period in the initial arc period following the short-circuit period, and outputs an arc current corresponding to the welding voltage subjected to constant voltage control in the second arc period after the arc period. Control the power supply circuit. The control unit further controls the power supply circuit so that a high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current. The control unit further calculates a recommended voltage value corresponding to the current setting value of the welding current, and increases or decreases the amplitude center current according to the voltage difference between the recommended voltage value and the voltage setting value of the welding voltage.

  In another aspect, the present invention provides a welding apparatus that uses carbon dioxide gas as a shielding gas and performs welding by a carbon dioxide arc welding method that alternately repeats a short-circuit state and an arc state, between a torch and a base material. A power supply circuit for applying a voltage and a control unit for controlling the voltage of the power supply circuit are provided. The control unit outputs a high-level current during the first arc period in the initial arc period following the short-circuit period, and outputs an arc current corresponding to the welding voltage subjected to constant voltage control in the second arc period after the arc period. Control the power supply circuit. The control unit further controls the power supply circuit so that a high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current. The control unit further calculates a recommended voltage value corresponding to the current setting value of the welding current, and increases or decreases the first arc period according to the voltage difference between the recommended voltage value and the voltage setting value of the welding voltage.

  In yet another aspect, the present invention provides a welding apparatus that performs welding by a carbon dioxide arc welding method in which carbon dioxide is used as a shielding gas and alternately repeats a short-circuit state and an arc state, between the torch and the base material. A power supply circuit for applying a voltage and a control unit for controlling the voltage of the power supply circuit are provided. The control unit outputs a high-level current during the first arc period in the initial arc period following the short-circuit period, and outputs an arc current corresponding to the welding voltage subjected to constant voltage control in the second arc period after the arc period. Control the power supply circuit. The control unit further controls the power supply circuit so that a high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current. The control unit further calculates a recommended voltage value corresponding to the current setting value of the welding current, and if the voltage difference between the recommended voltage value and the voltage setting value of the welding voltage is in the first range, the control unit calculates the recommended voltage value. Accordingly, the amplitude center current is increased / decreased, and when the voltage difference is the second range different from the first range, the first arc period is increased / decreased according to the voltage difference.

  Preferably, in any of the above welding apparatuses, the waveform that repeats the increase and decrease is a triangular wave or a sine wave.

  Preferably, in any one of the above-described welding apparatuses, the control unit performs constriction detection control for reducing the short-circuit current when the constriction of the droplet is detected during the short-circuit period.

  According to the present invention, in the carbon dioxide arc welding method, stable current growth is achieved by superimposing a waveform that increases or decreases at a constant frequency and with an amplitude matched to the size of the droplet on the current at the beginning of the arc period. Can be realized. Thereby, an unnecessary short circuit does not occur at the initial stage of the arc, and high welding stability can be obtained. Further, even if the set voltage is changed from the recommended voltage set by the welding apparatus, the arc is prevented from becoming unstable.

1 is a block diagram of a welding apparatus according to Embodiment 1. FIG. 6 is an operation waveform diagram showing a welding voltage and a welding current when welding is performed by the welding apparatus according to Embodiment 1. FIG. It is the figure which showed the state of the welding part in t = t3 of FIG. It is the figure which showed the state of the welding part in t = t4 of FIG. It is the figure which showed the state of the welding part in t = t5 of FIG. It is the figure which showed the state of the welding part in t = t7 of FIG. It is the block diagram which showed the structure of 100 A of welding apparatuses which concern on Embodiment 2. FIG. It is the block diagram which showed the structure of the welding apparatus 100B which concerns on Embodiment 3. FIG. It is the block diagram which showed the structure of 100 C of welding apparatuses which concern on Embodiment 4. FIG. FIG. 10 is an operation waveform diagram showing a welding voltage, a welding current, and a control signal when welding is performed by the welding apparatus according to the fourth embodiment. It is the block diagram which showed the structure of welding apparatus 100D which concerns on Embodiment 5. FIG. It is the block diagram which showed the structure of the welding apparatus 100E which concerns on Embodiment 6. FIG. It is a figure for demonstrating the consumable electrode type arc welding method which repeats a short circuit and arc generation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. The welding method described in the present embodiment is a welding method that repeats a short circuit state and an arc state, and is different from the pulse arc welding method.

[Embodiment 1]
FIG. 1 is a block diagram of the welding apparatus according to the first embodiment.

  Referring to FIG. 1, welding device 100 includes a power supply circuit 102, a power supply control device 104, a wire feeding device 106, and a welding torch 4.

  The power supply control device 104 controls the power supply circuit 102 to control the welding current Iw and the welding voltage Vw output to the welding torch 4 to values suitable for welding.

  The wire feeding device 106 feeds the welding wire 1 to the welding torch 4. Although not shown, a shielding gas containing carbon dioxide as a main component is released from the tip portion of the welding torch 4. An arc 3 is generated between the welding wire 1 protruding from the tip of the welding torch 4 and the base material 2, and the welding wire 1 is melted to weld the base material 2. The wire feeding device 106 includes a feeding speed setting circuit FR, a feeding control circuit FC, a feeding motor WM, and a feeding roll 5.

  Power supply circuit 102 includes a power supply main circuit PM, reactors WL1 and WL2, a transistor TR1, a voltage detection circuit VD, and a current detection circuit ID.

  The power source main circuit PM receives a commercial power source (not shown) such as a three-phase 200V, performs output control by inverter control according to an error amplification signal Ea described later, and obtains a welding current Iw and a welding voltage Vw suitable for arc welding. Output. Although not shown, the power supply main circuit PM includes, for example, a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current, and arcs the high frequency alternating current A high-frequency transformer that steps down to a voltage value suitable for welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and performs pulse width modulation control using the error amplification signal Ea as an input. And a driving circuit for driving.

  Reactor WL1 and reactor WL2 smooth the output of power supply main circuit PM. A transistor TR1 is connected in parallel to the reactor WL2. The transistor TR1 is turned off only in the second arc period Ta2 in response to a NAND logic signal Na that becomes Low in the second arc period described later with reference to FIG.

  The feed speed setting circuit FR outputs a feed speed setting signal Fr corresponding to a predetermined steady feed speed setting value. The feeding control circuit FC outputs a feeding control signal Fc for feeding the welding wire 1 at a feeding speed corresponding to the value of the feeding speed setting signal Fr to the feeding motor WM. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 of the wire feeding device 106, and an arc 3 is generated between the welding wire 1 and the base material 2.

  The current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd.

  The power supply control device 104 includes an arc detection circuit AD, a timer circuit TM, a NAND circuit NAND, an inverting circuit NOT, a gain setting circuit G1R, an amplitude center current setting circuit IHCR, a frequency setting circuit FH, An amplitude setting circuit WH, a welding current setting circuit IR, a current error amplification circuit EI, a welding voltage setting circuit VR, a reference voltage setting circuit VCR, voltage error amplification circuits EV and EC, a voltage averaging circuit VA, And an external characteristic switching circuit SW.

  The arc detection circuit AD receives the welding voltage detection signal Vd, and receives the arc detection signal Ad that becomes a high level when the occurrence of an arc is determined when the value of the welding voltage detection signal Vd exceeds a threshold value. Output. The timer circuit TM receives the arc detection signal Ad, and receives a timer signal Tm that is at a high level for a predetermined period after the arc detection signal Ad is at a low level and for a predetermined period after the arc detection signal Ad is at a high level. Output. The NAND circuit NA receives a signal obtained by inverting the timer signal Tm by the inverting circuit NOT and the arc detection signal Ad, and outputs a NAND logic signal Na.

  The welding voltage setting circuit VR outputs a welding voltage setting signal Vr (corresponding to the voltage Vr in FIG. 2) set by an operator or the like. The voltage averaging circuit VA outputs an average voltage detection signal Va obtained by averaging the welding voltage detection signal Vd. The voltage error amplification circuit EV amplifies an error between the welding voltage setting signal Vr and the average voltage detection signal Va and outputs a voltage error amplification signal Ev.

  The reference voltage setting circuit VCR outputs a reference voltage setting signal Vcr indicating a voltage setting value determined in advance so as to have an appropriate arc length corresponding to welding conditions such as a wire feed speed and a welding speed. This reference voltage setting signal Vcr corresponds to the unitary voltage center. The voltage error circuit EC calculates an error between the welding voltage setting signal Vr and the reference voltage setting signal Vcr, and outputs a reference voltage error signal Ec.

The gain setting circuit G1R outputs a predetermined first gain setting signal G1r. The amplitude center current setting circuit IHCR receives the first gain setting signal G1r and the reference voltage error signal Ec (= Vr−Vcr) and outputs an amplitude center current setting signal Ihcr represented by the following equation (1).
Ihcr = Ihcr0 + G1r * (Vr−Vcr) (1)
Here, Ihcr represents an amplitude center current setting signal, Ihcr0 represents a reference amplitude center current setting signal corresponding to the reference voltage setting signal Vcr, G1r represents a first gain setting signal, and Vr represents a welding voltage setting signal. Vcr represents a reference voltage setting signal. G1r can be set to, for example, 10 to 50 (A / V). This indicates that the change width of the amplitude center current setting signal Ihcr is 10 to 50 A with respect to the voltage deviation 1V.

  The frequency setting circuit FH outputs a predetermined frequency setting signal Fh. The amplitude setting circuit WH outputs a predetermined amplitude setting signal Wh. The welding current setting circuit IR receives the amplitude center current setting signal Ihcr, the frequency setting signal Fh, and the amplitude setting signal Wh, and outputs a welding current setting signal Ir. The current error amplification circuit EI amplifies an error between the welding current setting signal Ir and the welding current detection signal Id and outputs a current error amplification signal Ei.

  External characteristic switching circuit SW receives timer signal Tm, current error amplification signal Ei, and voltage error amplification signal Ev as inputs.

  When the timer signal Tm is at a high level, the external characteristic switching circuit SW switches to the input terminal a side and outputs the current error amplification signal Ei as the error amplification signal Ea. At this time, since the current error is fed back to the power supply main circuit PM, constant current control is performed.

  When the timer signal Tm is at the low level, the external characteristic switching circuit SW switches to the input terminal b side and outputs the voltage error amplification signal Ev as the error amplification signal Ea. The welding current Iw is controlled by these blocks. At this time, since the voltage error is fed back to the power supply main circuit PM, constant voltage control is performed.

  FIG. 2 is an operation waveform diagram showing a welding voltage and a welding current when welding is performed by the welding apparatus according to the first embodiment.

  Referring to FIGS. 1 and 2, welding proceeds by repeating a short circuit period Ts and an arc period. The arc period is divided into an initial first arc period Ta1 and a later second arc period Ta2.

  In the short-circuit period Ts at times t0 to t2, the welding wire 1 and the base material 2 come into contact with each other, a short-circuit current flows, Joule heat is generated at the tip of the welding wire 1, and the tip of the welding wire 1 becomes high temperature.

  When the droplet at the tip of the welding wire 1 moves and an arc is generated at time t2, the power supply control device 104 determines that the arc has occurred in response to the rapid increase in the welding voltage. In response to this, the power supply control device 104 switches the control to the constant current control, and shifts to the first arc period Ta1. The welding current rises to a high level current (the amplitude center is the amplitude center current Ihcr). Thereafter, a high level current is passed as a welding current for a certain period. The high level current is suppressed to a current value that does not cause the droplet to rise due to the arc force. The welding current flowing during the first arc period Ta1 is referred to as a high level current.

  When the wire feed speed or the welding current (average value) is set in the welding apparatus 100, the corresponding recommended voltage (unified voltage) Vcr is determined. On the other hand, the operator can set the set voltage Vr by the welding voltage setting signal Vr.

  Then, power supply control device 104 increases or decreases amplitude center current Ihcr in accordance with the voltage difference between set voltage Vr (corresponding to welding voltage setting signal Vr) and reference voltage Vcr (corresponding to reference voltage setting signal Vcr).

  When the set voltage Vr is low, the amplitude center current Ihcr is lowered to prevent the wire from being melted too much at the beginning of the arc period (first arc period Ta1), and constant voltage control in the latter half of the arc period (second arc period Ta2). The output voltage is likely to drop.

  Conversely, when the set voltage Vr is high, the amplitude center current Ihcr is increased to sufficiently melt the wire at the beginning of the arc period (first arc period Ta1), and constant voltage control in the second half of the arc period (second arc period Ta2). This makes it easy to increase the output voltage.

  Furthermore, in the example of FIG. 2, a waveform (for example, a triangular wave) that increases or decreases is superimposed on the high-level current. Even when the waveform to be increased or decreased is not superimposed on the high level current, the amplitude center current Ihcr may be increased or decreased as described above to be the high level current. However, even higher quality welding can be obtained if the increased and decreased waveforms are superimposed.

The melting rate Vm of the welding wire is expressed as Vm = αI + βI ² R. Here, α and β indicate coefficients, I indicates a welding current, and R indicates a resistance value of a portion (protrusion length) where the welding wire protrudes from the contact tip at the tip of the torch. It can be seen that when the welding current I is increased, the melting rate Vm of the welding wire also increases.

  However, when the welding current I is increased, the upward arc force acting on the droplet also increases. The arc force is proportional to the square of the welding current I. On the other hand, since gravity also acts on the droplet, an upward force works if the current value is large, and a downward force works if the current value is small, at the current value where the gravity and arc force are just balanced. When an alternating current is superimposed on the welding current I, an upward force and a downward force act alternately on the droplet. According to the inventor of the present application, when the current is increased or decreased in this manner, the upward and downward forces are alternately applied to the droplets to increase the overall current so that the upward force is continuously applied to the droplets. It was found that the droplets were more stable than those, and spatter could be reduced. Therefore, in the present embodiment, the current is increased or decreased during the first arc period to achieve stable and stepwise growth of the droplet.

  In the first arc period Ta1, a triangular wave described below is superimposed on the amplitude center current Ihcr during the period from time t3 to t6.

  The triangular wave to be superimposed is centered on the amplitude center current Ihcr (200 to 400 A), the frequency is 2.5 kHz to 5 kHz, and the first arc period Ta1 is 0.3 ms to 3.0 ms. The amplitude is + -50 to 100A. For example, the amplitude center current Ihcr may be set to Ihcr = 400 A, the frequency may be set to f = 4 kHz, the first arc period may be set to Ta1 = 1.0 ms, and the triangular wave to be superimposed may be set to four cycles. Note that the waveform to be superimposed is not limited to a triangular wave, but may be another waveform such as a sine wave.

Hereinafter, the state of the welded part in the first arc period Ta1 will be described in detail.
(1) 0-1 / 2 period of triangular wave FIG. 3: is the figure which showed the state of the welding part in t = t3 of FIG. t = t3 is a point in time when the superposition of the triangular wave is started.

  Referring to FIG. 3, arc 3 is generated between the tip of welding wire 1 and base material 2. The tip of the welding wire 1 is heated by the heat generated by the arc 3 to melt the tip, and a droplet 6 is formed. The welding wire 1 is fed in the direction of the base material 2 by a feeding device.

  The superposed current increases the wire melting rate and enlarges the droplet, and the force applied to the droplet is maximized in a quarter cycle, and the droplet rises due to the arc reaction force. However, since the arc reaction force decreases as the current decreases toward the ½ cycle, the rising can be prevented.

  FIG. 4 is a diagram showing the state of the welded portion at t = t4 in FIG. t = t4 is the time when a half period of the triangular wave has elapsed. As shown in FIG. 4, the droplet 6 at the tip of the welding wire 1 has grown slightly and is in a slightly raised state.

(2) 1/2 to 3/4 period of triangular wave During this period, the welding current is reduced from the amplitude center current Ihcr by the power supply control device 104, and the arc reaction force against the droplet is further lowered.

(3) 3/4 to 1 period of triangular wave In 3/4 to 1 period of triangular wave, the welding current is increased again from the lower peak value of the triangular wave to the amplitude center current Ihcr.

  FIG. 5 is a diagram showing the state of the welded portion at t = t5 in FIG. t = t5 is the time when one cycle of the triangular wave has elapsed. As shown in FIG. 5, since the arc reaction force is reduced, the gravity acting on the droplet 6 and the arc reaction force are in a good balance. As a result, the rising of the droplet 6 is eliminated, and the droplet 6 is in a suspended state.

  Then, the triangular wave described in (1) to (3) is repeated a predetermined number of times and superimposed on the amplitude center current Ihcr. Thereby, the droplet size is gradually increased while preventing the rising due to the arc reaction force, and a droplet having a desired size is formed.

  Note that the inductance value WL1 in the first arc period Ta1 is set to be smaller than the next second arc period Ta2 (inductance value is WL1 + WL2) in order to facilitate the superposition of the triangular wave.

Hereinafter, the state of the welded part in the second arc period Ta2 will be described in detail.
Referring to FIG. 2 again, at time t2, the first arc period Ta1 ends and shifts to the second arc period Ta2. In the second arc period Ta2, the power supply control device 104 increases the inductance value of the power supply circuit 102 and switches the control from constant current control to constant voltage control for arc length control. In FIG. 1, this switching corresponds to switching the external characteristic switching circuit SW from the terminal a to the terminal b. Since the inductance is large, the welding current gradually decreases according to the arc load. In addition, the welding voltage decreases gradually.

FIG. 6 is a view showing the state of the welded portion at t = t7 in FIG.
As shown in FIG. 6, the droplet formed in the first arc period Ta <b> 1 approaches the molten pool while rising slightly in the second arc period Ta <b> 2 without rising. Since the change in the arc length due to the rise is prevented and the arc length is adjusted by the constant voltage control, and the change in the arc force becomes gentle, the molten pool is hardly vibrated. Further, since the welding current is gradually reduced, the heat input to the base material is sufficiently performed, and the familiarity of the toe portion of the bead is improved.

  At time t8 in FIG. 2, when the droplet contacts the molten pool and a short circuit occurs, the welding voltage drops rapidly. The power supply control device 104 in FIG. 1 increases the welding current at a desired rising speed when a short circuit is determined by the rapid drop in the welding voltage. As the welding current rises, an electromagnetic pinch force acts on the upper part of the droplet to cause constriction, and the droplet 6 moves to the molten pool 7.

  As described above, the welding method shown in the first embodiment is a carbon dioxide arc welding method in which low spatter control is performed, but is different from the pulse arc welding method.

  That is, the welding method shown in Embodiment 1 is a welding method that repeats a short circuit state and an arc state. In such a welding method, when the welding current is increased in order to increase the welding speed, welding is performed in the globule transition region, and the repetition of the short circuit state and the arc state becomes irregular.

  Therefore, in the welding method shown in the first embodiment, a high level current is output during the first arc period Ta1 of a certain period, and constant current control is performed during the first arc period Ta1, so that an alternating current, for example, a triangular wave, Alternatively, a low-frequency current having a constant frequency that periodically changes such as a sine wave is superimposed. Thereby, it is possible to prevent the droplet from rising due to the arc reaction force, and to realize stable droplet growth.

  Then, the amplitude center current Ihcr is increased or decreased according to the voltage difference between the set voltage Vr (corresponding to the welding voltage setting signal Vr) and the reference voltage Vcr (corresponding to the reference voltage setting signal Vcr).

  When the set voltage Vr is low, the amplitude center current Ihcr is lowered to prevent the wire from being melted too much at the beginning of the arc period (first arc period Ta1), and constant voltage control in the latter half of the arc period (second arc period Ta2). The output voltage is likely to drop.

  Conversely, when the set voltage Vr is high, the amplitude center current Ihcr is increased to sufficiently melt the wire at the beginning of the arc period (first arc period Ta1), and constant voltage control in the second half of the arc period (second arc period Ta2). This makes it easy to increase the output voltage.

  When the first arc period Ta1 elapses, the control of the welding power source is switched from constant current control to constant voltage control in order to perform arc length control in the second arc period Ta2. The inductance value of the reactor of the welding power source is made larger than the first arc period Ta1, and the welding current is gradually reduced. As a result, the change in the arc force becomes gentle, so that the molten pool is less vibrated. Further, since the welding current is gradually reduced, the heat input to the base material is sufficiently performed, and the familiarity of the toe portion of the bead is improved.

  In the first embodiment described above, the actual reactor WL2 is inserted in the second arc period Ta2 in order to make the inductance value of the reactor of the welding power source larger than the first arc period Ta1. Instead, the inductance may be increased by electronically controlling the reactor.

  In the first embodiment described above, in the short-circuit period Ts, the current may be raised to a desired value while maintaining constant voltage control, or the current may be raised to a desired value by switching to constant current control. .

  In the above-described first embodiment, an example in which a triangular wave is superimposed on a high-level current is shown. However, even if a triangular wave is not superimposed, the high-level current is based on the voltage difference between the set voltage Vr and the reference voltage Vcr. It is possible to prevent the arc from becoming unstable even if the angle is changed.

[Embodiment 2]
In the first embodiment, the magnitude of the high level current is changed based on the voltage difference between the set voltage Vr and the reference voltage Vcr. However, in the second embodiment, the period of the high level current shown in FIG. One arc period Ta1) is changed based on the voltage difference between the set voltage Vr and the reference voltage Vcr.

  FIG. 7 is a block diagram showing a configuration of welding apparatus 100A according to the second embodiment. In the following description, only parts different from the first embodiment will be described, and the same parts as those of the first embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 7, welding apparatus 100 </ b> A includes power supply circuit 102, power supply control apparatus 104 </ b> A, wire feeding apparatus 106, and welding torch 4.

  Power supply control device 104A includes a gain setting circuit G2R instead of gain setting circuit G1R in the configuration of power supply control device 104 shown in FIG. The gain setting circuit G2R outputs a predetermined second gain setting signal G2r. The output of the gain setting circuit G2R is input to the timer circuit TM.

  In FIG. 1, the amplitude center current setting circuit IHCR outputs the amplitude center current setting signal Ihcr based on the reference voltage error signal Ec, but in FIG. 7, the amplitude center current setting circuit IHCR is determined in advance. The amplitude center current setting signal Ihcr is output.

  The reference voltage error signal Ec output from the voltage error circuit EC is input to the timer circuit TM instead of being input to the amplitude center current setting circuit IHCR.

The timer circuit TM receives the arc detection signal Ad, the second gain setting signal G2r, and the reference voltage error signal Ec, and when the arc detection signal Ad is at a low level and the arc detection signal Ad is at a high level. To output a timer signal Tm that becomes high level only during the first arc period Ta1. The first arc period Ta1 is expressed by the following equation (2).
Ta1 = Ta10 + G2r * (Vr−Vcr) (2)
Here, Ta1 indicates a first arc period, Ta10 indicates a reference first arc period corresponding to the reference voltage setting signal Vcr, G2r indicates a second gain setting signal, Vr indicates a welding voltage setting signal, Vcr represents a reference voltage setting signal. In addition, G2r can be 100-500 (microsecond / V), for example. This indicates that the change width of the first arc period Ta1 is 100 to 500 μs with respect to the voltage deviation 1V.

  Since the configuration of other parts of power supply control device 104A is similar to that of power supply control device 104 shown in FIG. 1, description thereof will not be repeated.

  The welding apparatus 100A of the second embodiment is the same as that of the first embodiment even when the set voltage Vr is changed by changing the first arc period Ta1 based on the voltage difference between the set voltage Vr and the reference voltage Vcr. It is possible to prevent the arc from becoming unstable.

[Embodiment 3]
In the first embodiment, only the amplitude center current setting signal Ihcr is increased or decreased according to the voltage difference (Vr−Vcr), and in the second embodiment, only the first arc period Ta1 is increased or decreased.

  In the third embodiment, upper and lower threshold values are provided for the voltage difference, and only the amplitude center current setting signal Ihcr is increased or decreased until the threshold value, and the voltage difference exceeding the threshold value or the voltage less than the threshold value is set. For the difference, only the first arc period Ta1 is increased or decreased.

  FIG. 8 is a block diagram showing a configuration of welding apparatus 100B according to the third embodiment. In the following description, only parts different from the first embodiment will be described, and the same parts as those of the first embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 8, welding apparatus 100 </ b> B includes a power supply circuit 102, a power supply control apparatus 104 </ b> B, a wire feeding apparatus 106, and a welding torch 4.

  The power supply control device 104B includes a reference voltage error signal distribution circuit DEC and a gain setting circuit G2R in addition to the configuration of the power supply control device 104 shown in FIG. The gain setting circuit G2R outputs a predetermined second gain setting signal G2r.

  The reference voltage error signal distribution circuit DEC receives the upper limit threshold value Tv1, the lower limit threshold value Tv2, and the reference voltage error signal Ec, and outputs a reference voltage error distribution current signal Eri and a reference voltage distribution time signal Ert.

  The reference voltage error distribution current signal Eri is input to the amplitude center current setting circuit IHCR together with the first gain setting signal G1r instead of the reference voltage error signal Ec.

  The reference voltage distribution time signal Ert is input to the timer circuit TM together with the second gain setting signal G2r.

The upper limit of the increase amount of the amplitude center current setting signal Ihcr from the reference amplitude center current setting signal Ihcr0 is defined as Ih1. In equation (1), the amount of increase is G1r * (Vr−Vcr), and therefore the predetermined upper limit threshold value Tv1 of the voltage difference (Vr−Vcr) is represented by the following equation (3).
Tv1 = Ih1 / G1r (3)
For example, when the first gain setting signal G1r is 10 A / V, if the increase amount upper limit Ih1 is 50 A, Tv1 is 5 V.

  The reference voltage error signal distribution circuit DEC outputs the reference voltage error signal Ec as the reference voltage error distribution current signal Eri until the reference voltage error signal Ec reaches the upper limit threshold value Tv1. In this case, the amplitude center of the high-level current is changed based on Expression (1) as in the first embodiment.

  When the reference voltage error signal Ec exceeds the upper limit threshold value Tv1, the reference voltage error signal distribution circuit DEC outputs the upper limit threshold value Tv1 as the reference voltage error distribution current signal Eri (reference voltage error signal Ec -The upper threshold value Tv1) is output as the reference voltage distribution time signal Ert. In this case, the amplitude center of the high level current is changed by a voltage corresponding to the upper limit threshold value Tv1. For the change exceeding the upper limit threshold value Tv1, as described in the second embodiment, the change is made only for the time corresponding to the first arc period Ta1.

Further, the lower limit of the amount of decrease in the amplitude center current setting signal Ihcr from the reference amplitude center current setting signal Ihcr0 is defined as Ih2. Since the increase amount is G1r * (Vr−Vcr) in the equation (1), the predetermined lower limit threshold value Tv2 of the voltage difference (Vr−Vcr) is expressed by the following equation (4).
Tv2 = Ih2 / G1r (4)
The reference voltage error signal distribution circuit DEC outputs the reference voltage error signal Ec as the reference voltage error distribution current signal Eri until the reference voltage error signal Ec reaches the lower threshold value Tv2. In this case, the amplitude center of the high-level current is changed based on Expression (1) as in the first embodiment.

  The reference voltage error signal distribution circuit DEC outputs the lower limit threshold value Tv2 as the reference voltage error distribution current signal Eri when the reference voltage error signal Ec becomes less than the lower limit threshold value Tv2. Ec-lower threshold value Tv2) is output as the reference voltage distribution time signal Vrt. In this case, the amplitude center of the high level current is changed by a voltage corresponding to the lower limit threshold Tv2. As for the change lower than the lower limit threshold Tv2, as described in the second embodiment, the change is made only for the time corresponding to the first arc period Ta1.

  In the third embodiment, the increase / decrease in the amplitude center current Ihcr of the high-level current described in the first embodiment and the change in the first arc period Ta1 described in the second embodiment are matched with the degree of change in the set voltage. By using in combination, the arc is prevented from becoming unstable.

  The third embodiment shows an example in which the amplitude center current Ihcr of the high level current is increased or decreased when the voltage difference is within a predetermined range, and the first arc period Ta1 is changed when the voltage difference is outside the predetermined range. However, the amplitude center current Ihcr and the first arc period Ta1 may be changed simultaneously.

[Embodiment 4]
In the fourth embodiment, in addition to the welding method described in the first embodiment, by detecting the constriction of the droplet before the arc is generated, the current is reduced before the arc is generated to reduce spatter.

  FIG. 9 is a block diagram showing a configuration of welding apparatus 100C according to the fourth embodiment. In the following description, only parts different from the first embodiment will be described, and the same parts as those of the first embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 9, welding device 100 </ b> C includes a power supply circuit 102 </ b> A, a power supply control device 104 </ b> C, a wire feeding device 106, and welding torch 4.

  The power supply circuit 102A includes a transistor TR2 and a current limiting resistor R in addition to the configuration of the power supply circuit 102 shown in FIG. Transistor TR2 is inserted in series with reactors WL1 and WL2 at the output of power supply main circuit PM. A current limiting resistor R is connected in parallel with the transistor TR2. Since the configuration of other parts of power supply circuit 102A is similar to that of power supply circuit 102 in FIG. 1, description thereof will not be repeated.

  The power supply control device 104C includes a constriction detection circuit ND, a constriction detection reference value setting circuit VTN, and a drive circuit DR in addition to the configuration of the power supply control device 104 shown in FIG. Since the configuration of other parts of power supply control device 104C is the same as that of power supply control device 104 in FIG. 1, description thereof will not be repeated.

  FIG. 10 is an operation waveform diagram showing a welding voltage, a welding current, and a control signal when welding is performed by the welding apparatus according to the fourth embodiment.

  Where the waveform in FIG. 10 differs from the waveform in the first embodiment in FIG. 2, the welding current is reduced when the constriction of the droplet is detected at time t1a, and then an arc is generated at time t2. This is the point.

  Since the amount of spatter is proportional to the magnitude of the current value when the arc is generated at time t2, the occurrence of spatter can be reduced by reducing the current value when the arc is generated.

  Referring to FIGS. 9 and 10, the squeezing detection reference value setting circuit VTN outputs a squeezing detection reference value signal Vtn. The squeezing detection circuit ND receives the squeezing detection reference value signal Vtn, the welding voltage detection signal Vd and the welding current detection signal Id described with reference to FIG. Detection of a squeeze that becomes high level when the value of Vtn is reached (time t1a) and becomes low level when the value of the welding voltage detection signal Vd becomes equal to or greater than the arc discrimination value Vta (time t2). The signal Nd is output. Therefore, a period in which the squeezing detection signal Nd is at a high level is a squeezing detection period Tn.

  When the differential value of the welding voltage detection signal Vd during the short-circuit period reaches the value of the squeezing detection reference value signal Vtn set so as to correspond thereto, the squeezing detection signal Nd is changed to a high level. May be. 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 welding current detection signal Id, and the squeezing detection reference value signal set so that the differential value of the resistance value corresponds to this value. When the value of Vtn is reached, the squeezing detection signal Nd may be changed to a high level. The constriction detection signal Nd is input to the power supply main circuit PM. The power supply main circuit PM stops output during the constriction detection period Tn.

  When the squeezing detection signal Nd is at a low level (when non-necking is detected), the driving circuit DR outputs a driving signal Dr that turns on the transistor TR2. In the constriction detection period Tn, the drive signal Dr is at a low level, so that the transistor TR2 is turned off. As a result, the current limiting resistor R is inserted into the energization path of the welding current Iw (path from the power supply main circuit PM to the welding torch 4). The value of the current limiting resistor R is set to a value (approximately 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (approximately 0.01 to 0.03Ω). For this reason, the energy accumulated in the DC reactor in the welding power source and the reactor of the cable is suddenly discharged, and the welding current Iw decreases rapidly as shown in time t1a to t2 in FIG. Become.

  When the short circuit is released and the arc is regenerated at time t2, the welding voltage Vw becomes equal to or higher than a predetermined arc discrimination value Vta. By detecting this, the squeezing detection signal Nd becomes low level, and the drive signal Dr becomes high level. As a result, the transistor TR2 is turned on, and thereafter, the arc welding control described in the first embodiment with reference to FIG. 2 is performed. Since the subsequent first arc period Ta1 and second arc period Ta2 have been described with reference to FIG. 2, description thereof will not be repeated.

  Since the welding apparatus according to the fourth embodiment can reduce the current value at the time of arc re-occurrence at the time of arc re-occurrence (time t2), in addition to the effect exhibited by the welding apparatus described in the first embodiment, the arc Spattering at the start of generation can be further reduced.

  In the fourth embodiment, the method of inserting the current limiting resistor R into the energizing path as means for rapidly reducing the welding current Iw when the constriction is detected has been described. As another means, a capacitor is connected in parallel between the output terminals of the welding apparatus via a switching element, and when the constriction is detected, the switching element is turned on and a discharge current is supplied from the capacitor to rapidly reduce the welding current Iw. You may use the method of making it.

[Embodiment 5]
In the fifth embodiment, in addition to the welding method described in the second embodiment, by detecting the constriction of the droplet before the arc is generated, the current is lowered before the arc is generated to reduce spatter.

  FIG. 11 is a block diagram showing a configuration of welding apparatus 100D according to the fifth embodiment. In the following description, only parts different from the second embodiment will be described, and the same parts as those of the second embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 11, welding apparatus 100 </ b> D includes a power supply circuit 102 </ b> A, a power supply control apparatus 104 </ b> D, a wire feeding apparatus 106, and welding torch 4.

  The power supply circuit 102A includes a transistor TR2 and a current limiting resistor R in addition to the configuration of the power supply circuit 102 shown in FIG. Transistor TR2 is inserted in series with reactors WL1 and WL2 at the output of power supply main circuit PM. A current limiting resistor R is connected in parallel with the transistor TR2. Since the configuration of other parts of power supply circuit 102A is similar to that of power supply circuit 102 in FIG. 7, the description thereof will not be repeated.

  Power supply control device 104D includes a constriction detection circuit ND, a constriction detection reference value setting circuit VTN, and a drive circuit DR in addition to the configuration of power supply control device 104A shown in FIG. Since the configuration of other parts of power supply control device 104C is the same as that of power supply control device 104A in FIG. 7, description thereof will not be repeated.

  Since the operations of the squeezing detection circuit ND, the squeezing detection reference value setting circuit VTN, and the drive circuit DR related to the squeezing detection have been described in the fourth embodiment, description thereof will not be repeated.

  Since welding apparatus 100D of the fifth embodiment can also reduce the current value at the time of arc re-generation at the time of arc re-generation, in addition to the effect exhibited by the welding apparatus described in the second embodiment, at the time of arc generation start Spatter can be further reduced.

[Embodiment 6]
In the sixth embodiment, in addition to the welding method described in the third embodiment, by detecting the constriction of the droplet before the arc is generated, the current is lowered before the arc is generated to reduce spatter.

  FIG. 12 is a block diagram showing a configuration of welding apparatus 100E according to the sixth embodiment. In the following description, only parts different from the third embodiment will be described, and the same parts as those of the third embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 12, welding apparatus 100 </ b> E includes a power supply circuit 102 </ b> A, a power supply control apparatus 104 </ b> E, a wire feeding apparatus 106, and welding torch 4.

  The power supply circuit 102A includes a transistor TR2 and a current limiting resistor R in addition to the configuration of the power supply circuit 102 shown in FIG. Transistor TR2 is inserted in series with reactors WL1 and WL2 at the output of power supply main circuit PM. A current limiting resistor R is connected in parallel with the transistor TR2. Since the configuration of other parts of power supply circuit 102A is similar to that of power supply circuit 102 in FIG. 8, description thereof will not be repeated.

  The power supply control device 104E includes a constriction detection circuit ND, a constriction detection reference value setting circuit VTN, and a drive circuit DR in addition to the configuration of the power supply control device 104B shown in FIG. Since the configuration of other parts of power supply control device 104C is the same as that of power supply control device 104B in FIG. 7, description thereof will not be repeated.

  Since the operations of the squeezing detection circuit ND, the squeezing detection reference value setting circuit VTN, and the drive circuit DR related to the squeezing detection have been described in the fourth embodiment, description thereof will not be repeated.

  Since welding apparatus 100E of the sixth embodiment can also reduce the current value at the time of arc re-occurrence at the time of arc re-generation, in addition to the effect exhibited by the welding apparatus described in the third embodiment, Spatter can be further reduced.

  Embodiment 6 shows an example in which the amplitude center current Ihcr of the high-level current is increased or decreased when the voltage difference is within a predetermined range, and the first arc period Ta1 is changed when the voltage difference is outside the predetermined range. However, the amplitude center current Ihcr and the first arc period Ta1 may be changed simultaneously.

Finally, the first to sixth embodiments will be summarized again with reference to FIG.
The welding apparatuses of Embodiments 1 to 6 are welding apparatuses that use carbon dioxide gas as a shielding gas and perform welding by a carbon dioxide arc welding method that alternately repeats a short circuit state and an arc state. Welding apparatuses 100 and 100A to 100E include power supply circuits 102 and 102A for applying a voltage between torch 4 and base material 2, and power supply control apparatuses 104 and 104A to 104E for controlling the voltages of power supply circuits 102 and 102A. Is provided. In the power supply control devices 104, 104A to 104E, a high level current is output in the first arc period Ta1 of the initial arc period following the short circuit period, and constant voltage control is performed in the second arc period Ta2 of the latter period of the arc period. The power supply circuits 102 and 102A are controlled so that an arc current corresponding to the voltage is output. The power supply control devices 104 and 104A to 104E further control the power supply circuits 102 and 102A so that a high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current.

  Power supply control devices 104 and 104C according to the first and fourth embodiments further calculate a recommended voltage value (reference voltage Vcr) corresponding to the current setting value of the welding current, and the recommended voltage value (reference voltage Vcr) and the welding voltage. The amplitude center current Ihcr is increased or decreased according to the voltage difference from the voltage set value Vr.

  Power supply control devices 104A and 104D of the second and fifth embodiments further calculate a recommended voltage value (reference voltage Vcr) corresponding to the current setting value of the welding current, and the recommended voltage value (reference voltage Vcr) and the welding voltage. The first arc period Ta1 is increased or decreased according to the voltage difference from the voltage set value Vr.

  The power supply control devices 104B and 104E of the third and sixth embodiments further calculate a recommended voltage value (reference voltage Vcr) corresponding to the current setting value of the welding current, and the recommended voltage value (reference voltage Vcr) and the welding voltage. When the voltage difference from the voltage set value Vr is within the first range (between the upper limit threshold Th1 and the lower limit threshold Th2), the amplitude center current is increased or decreased according to the voltage difference, and the voltage difference is When the second range is different from the first range (above the upper limit threshold Th1 or lower than the lower limit threshold Th2), the first arc period is increased or decreased according to the voltage difference.

  Preferably, in welding apparatuses 100, 100A to 100E, the waveform that repeatedly increases and decreases is a triangular wave or a sine wave.

  Preferably, in welding apparatuses 100C to 100E, power supply control devices 104C to 104E perform constriction detection control for reducing the short-circuit current when the constriction of the droplet is detected during the short-circuit period, as described with reference to FIG. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Welding wire, 2 base material, 3 arc, 4 welding torch, 5 feeding roll, 6 droplet, 7 molten pool, 100,100A-100E welding apparatus, 102,102A power supply circuit, 104,104A-104E power supply control apparatus , 106 Feeder, AD arc detection circuit, DEC reference voltage error signal distribution circuit, DR drive circuit, EC voltage error circuit, EV voltage error amplifier circuit, EI current error amplifier circuit, FC feed control circuit, FH frequency setting circuit , FR feed speed setting circuit, G1R, G2R gain setting circuit, ID current detection circuit, IHCR amplitude center current setting circuit, IR welding current setting circuit, NA NAND circuit, ND necking detection circuit, NOT inverting circuit, R current limiting resistor , SW External characteristic switching circuit, TM timer circuit, TR1, TR2 transistor, VA voltage Averaging circuit, VCR reference voltage setting circuit, VD voltage detection circuit, VR welding voltage setting circuit, VTN detection reference value setting circuit, WH amplitude setting circuit, WL1, WL2 reactor.

Claims (5)

A welding apparatus that uses carbon dioxide gas as a shielding gas and performs welding by a carbon dioxide arc welding method that alternately repeats a short circuit state and an arc state,
A power supply circuit for applying a voltage between the torch and the base material;
A control unit for controlling the voltage of the power supply circuit,
The control unit outputs an arc current corresponding to a welding voltage, in which a high level current is output in a first arc period in an initial period of an arc following a short circuit period, and constant voltage control is performed in a second arc period in the latter period of the arc period. Control the power supply circuit so that is output,
The control unit controls the power supply circuit so that the high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current,
The control unit calculates a recommended voltage value corresponding to the current setting value of the welding current, and increases or decreases the amplitude center current according to a voltage difference between the recommended voltage value and the voltage setting value of the welding voltage. . A welding apparatus that uses carbon dioxide gas as a shielding gas and performs welding by a carbon dioxide arc welding method that alternately repeats a short circuit state and an arc state,
A power supply circuit for applying a voltage between the torch and the base material;
A control unit for controlling the voltage of the power supply circuit,
The control unit outputs an arc current corresponding to a welding voltage, in which a high level current is output in a first arc period in an initial period of an arc following a short circuit period, and constant voltage control is performed in a second arc period in the latter period of the arc period. Control the power supply circuit so that is output,
The control unit controls the power supply circuit so that the high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current,
The control unit calculates a recommended voltage value corresponding to a current setting value of a welding current, and increases or decreases the first arc period according to a voltage difference between the recommended voltage value and a voltage setting value of a welding voltage. apparatus. A welding apparatus that uses carbon dioxide gas as a shielding gas and performs welding by a carbon dioxide arc welding method that alternately repeats a short circuit state and an arc state,
A power supply circuit for applying a voltage between the torch and the base material;
A control unit for controlling the voltage of the power supply circuit,
The control unit outputs an arc current corresponding to a welding voltage, in which a high level current is output in a first arc period in an initial period of an arc following a short circuit period, and constant voltage control is performed in a second arc period in the latter period of the arc period. Control the power supply circuit so that is output,
The control unit controls the power supply circuit so that the high level current is generated by superimposing a waveform that repeatedly increases and decreases on the amplitude center current,
The control unit calculates a recommended voltage value corresponding to the current setting value of the welding current, and when the voltage difference between the recommended voltage value and the voltage setting value of the welding voltage is within a first range, the voltage difference is calculated. A welding apparatus that increases or decreases the amplitude center current according to the voltage difference, and increases or decreases the first arc period according to the voltage difference when the voltage difference is a second range different from the first range.   The welding apparatus according to claim 1, wherein the waveform is a triangular wave or a sine wave.   The welding apparatus according to any one of claims 1 to 4, wherein the control unit performs a necking detection control for reducing a short-circuit current when the necking of a droplet is detected during the short-circuit period.

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