JP6158652B2 - Power supply apparatus for arc welding and welding state determination method of arc welding - Google Patents

Description

  The present invention relates to a power supply device for consumable electrode arc welding in which a short circuit and an arc state occur alternately, and a welding state determination method of arc welding used for control of the power supply device.

  In consumable electrode arc welding, welding is performed by alternately repeating short-circuiting and arcing between the wire electrode and the object to be welded, but this arc welding power supply device determines the short-circuiting and arcing. Appropriate output current settings are made from time to time, including state determination. Therefore, it is one of the important factors in improving the welding quality that the determination of the short circuit / arc state is more appropriate.

For example, the technology disclosed in Patent Document 1 detects a voltage (output current) between terminals of a DC reactor connected to an output circuit, and when the voltage between the terminals is positive, a short-circuited state, and when the voltage between the terminals is negative, an arc Each state is determined as a state. That is, when the voltage between terminals is e, the DC reactor is L, and the current change amount per unit time is di / dt,

e = −L × di / dt

Can be expressed as If the output current changes such that the output current increases in a short-circuit state and decreases in an arc state, the current change amount di / dt has a positive value in a short-circuit state and a negative value in an arc state.

  However, the above disclosed technique is based on a current waveform in which the current change amount di / dt during the short circuit period is positive, the current change amount di / dt during the arc period is negative, and the sign does not change in each state. ing. That is, although the output current control (output current waveform) can be applied to a relatively simple one, the recent output current control (output current waveform) as shown in FIG. Because the output current is suddenly decreased or the output current is suddenly increased during the arc period as indicated by an arrow x2 in the figure, the sign of the current change amount di / dt changes during each period, and the short circuit / arc state Misjudgment will occur.

  In contrast to the above disclosed technique, for example, in the disclosed technique disclosed in Patent Document 2, the determination of the short circuit / arc state is performed based on the comparison between the output voltage (welding voltage) and the reference value, and immediately after the switching of the short circuit / arc state. In order to prevent erroneous determination at the time of sudden change, the reference value is calculated from time to time.

JP-A-5-329640 JP 2009-195952 A

  By the way, when the power supply device and the wire electrode (torch) are separated from each other, the power cable installed between them is extended, thereby increasing the resistance value on the electric circuit between them. Then, as shown in FIG. 7, a delay time Td occurs in the output voltage of the mode in which the power cable is extended with respect to the output voltage of the mode in which the power cable is not extended, and the behavior becomes dull. Incidentally, the delay time Td is a time that can be several hundred μs or more. As a result, erroneous determination of the welding state can be suppressed, but a delay occurs in each determination of the short circuit and the arc state based on the delay time Td.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power supply apparatus for arc welding that can more appropriately determine a short circuit / arc state and contribute to improvement in welding quality, and the power supply apparatus. Another object of the present invention is to provide a method for determining the welding state of arc welding used for controlling the above.

  A power supply apparatus for arc welding that solves the above problem includes a switching circuit that adjusts output power for arc welding based on a switching operation, and a control circuit that controls the switching operation. A power supply apparatus for arc welding, comprising: a welding state determination unit that determines a short circuit / arc state in welding; and a switching control unit that controls the operation of the switching circuit including the determination of the welding state. Further includes a current change amount monitoring unit that detects a current change amount of the output current of the power supply device, wherein the welding state determination unit is configured to output the output current during the ON period of the switching circuit acquired through the current change amount monitoring unit. When the current change amount is larger than the judgment value, the short-circuited state, and when the current change amount is smaller than the judgment value, the arc Determined to be a state.

  According to this configuration, the welding state determination is a short circuit state when the current change amount of the output current is larger than the determination value during the ON period of the switching circuit, and an arc state when the current change amount is smaller than the determination value. Is determined. In other words, the output current increases during the ON period of the switching circuit, but the output current increases so that the load is small and the current increase is large in the short circuit state, and the load is large and the current increase is small in the arc state. The difference in the amount of current increase appears relatively large. Paying attention to this, the effect of the length of the power cable installed between the power supply device and the electrode to be welded can be determined by determining the short-circuit / arc state based on the current change amount (current increase amount) of the output current. The welding state is appropriately determined without receiving. Therefore, the switching circuit control including the determination of the welding state is appropriate for the switching operation of the switching circuit from time to time, the output power of the power supply device at that time is appropriate, and the welding quality is improved. Can be expected.

  In the arc welding power supply device described above, the determination value used in the welding state determination unit is different from the determination value for determining the short-circuit state and the determination value for determining the arc state, and is spaced from each other. It is preferable that it is set.

  According to this configuration, since the determination value for determining the short-circuit state larger than that and the determination value for determining the arc state smaller than that are set to different values at intervals, higher values than eliminating the noise element are set. An accurate determination is made.

  In addition, the arc welding welding state determination method for solving the above-mentioned problem is to adjust the output power for arc welding by controlling the switching operation of the switching circuit. A state determination method, based on a current change amount of an output current during an ON period of the switching circuit, when a current change amount is larger than a determination value, a short circuit state, and when a current change amount is smaller than a determination value It determines with it being in an arc state.

  According to this configuration, similarly to the above-described arc welding power supply device, the determination of the short circuit / arc state is appropriately performed based on the current change amount (current increase amount) of the output current, and improvement in welding quality can be expected. .

  According to the arc welding power supply apparatus and the arc welding welding state determination method of the present invention, it is possible to more appropriately determine a short circuit / arc state and contribute to improvement in welding quality.

It is a lineblock diagram of a consumable electrode type arc welding machine (power supply device for arc welding) in one embodiment. It is a wave form chart for explaining a judgment mode of a welding state in one embodiment. It is a wave form diagram for demonstrating the relationship between the inverter operation | movement and output current variation | change_quantity in one Embodiment. It is explanatory drawing about the setting of the determination value of the welding state in one Embodiment. Waveform diagram of output current and output voltage by conventional control. Waveform diagram of output current and output voltage by conventional control. The wave form diagram for demonstrating the determination aspect of the conventional welding state.

Hereinafter, an embodiment of a power supply device for arc welding and a welding state determination method for arc welding will be described.
As shown in FIG. 1, in the consumable electrode type arc welding machine 10, a wire electrode 12 supported by a torch TH is connected to a positive output terminal of a power supply device 11, and welding is performed on the negative output terminal of the power supply device 11. Arc welding is performed by connecting the target M and applying the DC output power generated by the power supply device 11 to the wire electrode 12. At this time, since the wire electrode 12 is consumed during welding, the wire supply device 13 feeds the wire electrode 12 according to the consumption.

  The power supply device 11 converts three-phase AC input power supplied from a commercial power source into DC output power suitable for arc welding. The AC input power is converted into DC power by a rectifying / smoothing circuit 21 including a diode bridge and a smoothing capacitor, and the converted DC power is converted into high-frequency AC power by an inverter circuit 22. The inverter circuit 22 is configured by a bridge circuit using a switching element TR such as an IGBT, and PWM control by the control circuit 31 is performed.

  The high-frequency AC power generated by the inverter circuit 22 is converted to secondary AC power adjusted to a predetermined voltage value by the welding transformer 23. The secondary side AC power of the welding transformer 23 is converted into DC output power suitable for arc welding by a rectifier circuit 24 using a diode and a DC reactor 25.

  The control circuit 31 includes a PWM control unit 31a, a welding state determination unit 31b, and a current change amount monitoring unit 31c. The PWM control unit 31a performs a PWM control by outputting a pulse control signal Sp to the switching element TR of the inverter circuit 22, and performs a control to make the DC output power an appropriate value from time to time. The control circuit 31 acquires the output current Io and the output voltage Vo based on the input of detection signals from the current sensor 32 and the voltage sensor 33, and is used for control by the PWM control unit 31a.

  The welding state determination unit 31b has a short circuit state in which the wire electrode 12 contacts the welding object M in the short circuit / arc state alternately repeated in arc welding, or an arc is generated between the wire electrode 12 and the welding object M. It is determined which welding state is in the arc state. At this time, the welding state is determined in consideration of the magnitude of the current change amount ΔIo (see FIG. 2) of the output current Io performed by the current change amount monitoring unit 31c.

  Here, as shown in FIG. 3, the output current increases when the inverter circuit 22 is turned on by the switching operation. However, since the load is small in the short circuit state in the welding state and the load is large in the arc state, the output current is large. The difference in the amount of current increase appears relatively large. Specifically, in the on period of the inverter circuit 22 between the times t11 and t12, since the load is small and the load is small, the current increase amount of the output current is large, but in the on period of the inverter circuit 22 between the times t13 and t14, the arc state Because of the large load, the increase in output current is small.

  Based on this, the welding state determination unit 31b acquires the current change amount (current increase amount) ΔIo of the output current Io during the ON period of the inverter circuit 22 through the current change amount monitoring unit 31c, and determines the short circuit / arc state, respectively. The welding state is determined in comparison with the determination values ΔIs and ΔIa to be performed. 4 plots the average value of the current change amount ΔIo of the output current Io during the ON period of the inverter circuit 22, and the set of the short-circuit state and the set of the arc state are relatively clearly separated. Then, based on FIG. 4, a determination value ΔIs that is greater than that and a determination value ΔIa that is determined to be a short-circuit state is set, and a determination value ΔIa that is smaller than that is determined to be an arc state, and between the determination value ΔIs and the determination value ΔIa An interval is provided.

  The PWM control unit 31a outputs a pulse control signal to the inverter circuit 22 (switching element TR) based on the determination of the short circuit / arc state by the welding state determination unit 31b in addition to the acquired output current Io and output voltage Vo. The duty of Sp is set appropriately. That is, the control circuit 31 performs PWM control of the inverter circuit 22 as described above, and appropriately adjusts the output power at that time.

Next, the operation (action) of arc welding according to this embodiment will be described.
At the time of arc welding, the switching operation of the inverter circuit 22 based on the PWM control of the control circuit 31 (PWM control unit 31a) is performed. At that time, in the welding state determination unit 31b, the short circuit / arc state is determined while the inverter circuit 22 is on.

  During the time t1-t2, the time t3-t4, and the time t5-t6 shown in FIG. In the ON period of the inverter circuit 22 between the times t1 and t2, since the current change amount (current increase amount) ΔIo of the output current Io acquired by the current change amount monitoring unit 31c is smaller than the determination value ΔIa, the welding state determination unit 31b. It is determined that the arc state. The determination of the arc state is maintained during the off period of the inverter circuit 22 between the time t2 and the time t3 immediately after.

  Next, in the ON period of the inverter circuit 22 between time t3 and t4, since the current change amount ΔIo of the output current Io is smaller than the determination value ΔIa until time t3a, it is determined that the arc state continues. Is done. After the time t3a, the current change amount ΔIo of the output current Io becomes larger than the determination value ΔIs, so that it is determined that the short-circuit state has been switched. This determination of the short-circuit state is maintained during the off period of the inverter circuit 22 between time t4 and time t5 immediately after.

  Next, in the ON period of the inverter circuit 22 between time t5 and t6, the current change amount ΔIo of the output current Io is larger than the determination value ΔIs until the time t5a, so that it is determined that the short circuit state continues. Is done. After time t5a, the current change amount ΔIo of the output current Io is smaller than the determination value ΔIa, so it is determined that the arc state has been switched. This determination of the arc state is maintained during the off period of the inverter circuit 22 after time t6 immediately after.

  In this manner, the short circuit / arc state during arc welding is determined and reflected in the control of the inverter circuit 22. That is, since the appropriate welding state is determined without being affected by the length of the power cable installed between the power supply device 11 and the wire electrode 12, the switching operation of the inverter circuit 22 is appropriately performed at that time. Thus, the output power of the power supply device 11 at that time becomes appropriate, and improvement in welding quality can be expected.

  In the welding state determination method of the present embodiment, the OFF period of the inverter circuit 22 cannot be determined and becomes a dead zone. Therefore, although there is a concern that a delay may occur in the determination of the welding state, the switching frequency of the inverter circuit 22 is about 100 kHz, and the delay time due to this is about 10 μs at the maximum. Moreover, the opportunity is only during the off period.

  On the other hand, the delay time accompanying the extension of the power cable of the output voltage used for determining the welding state, which has been a problem in the past, can be 100 μs or more. In addition, since a delay occurs regardless of the on / off period of the inverter in the past, the influence on the control of the inverter circuit 22 with respect to the delay in the determination of the welding state concerned in this embodiment, that is, the influence of the welding quality is extremely small. ing. Further, at the time of high output where the influence of the welding quality is large, the on-period of the inverter circuit 22 is long and the off-period is short. Even with this in mind, it can be expected that the arc welding of this embodiment will improve the welding quality.

Next, characteristic effects of the present embodiment will be described.
(1) The determination of the welding state of the present embodiment is performed when the current change amount ΔIo of the output current Io is larger than the determination value ΔIs during the ON period of the inverter circuit 22, and the current change amount ΔIo is determined from the determination value ΔIa. When it is small, it is determined that it is in an arc state. That is, the output current Io increases during the ON period of the inverter circuit 22, but the load is small and the current increase amount is large in the short circuit state, and the load is large and the current increase amount is small in the arc state. The difference in the current increase amount of the output current Io appears relatively large. Focusing on this, by determining the short-circuit / arc state based on the current change amount (current increase amount) ΔIo of the output current Io, the length of the power cable installed between the power supply device 11 and the wire electrode 12 is determined. It is possible to appropriately determine the welding state without being affected. Therefore, in the control of the inverter circuit 22 including the determination of the welding state, the switching operation of the inverter circuit 22 becomes an appropriate operation from time to time, the output power of the power supply device 11 from time to time becomes appropriate, and welding is performed. It can contribute to quality improvement.

(2) Since the determination values ΔIs and ΔIa for determining the welding state are set to different values at intervals, more accurate determination can be performed without the noise element.
In addition, you may change the said embodiment as follows.

Although the determination values ΔIs and ΔIa for determining the welding state are set to different values at intervals, one determination value may be used.
A configuration using a switching circuit other than the inverter circuit 22 may be used.

A configuration using switching control other than PWM control may be used.
In addition, the configuration of the power supply device 11 may be changed as appropriate.
Next, a technical idea that can be grasped from the above embodiment and another example will be added below.

(A) In the welding state determination method of arc welding according to claim 3,
The determination value used in the determination of the welding state is a value different from the determination value for determining the short-circuit state and the determination value for determining the arc state, and arc welding is characterized in that they are set at intervals. (B) An arc welding machine comprising the power supply device for arc welding according to claim 1.

11 Power supply device (Power supply device for arc welding)
22 Inverter circuit (switching circuit)
31 control circuit 31a PWM control unit (switching control unit)
31b Welding state determination unit 31c Current change amount monitoring unit Io Output current ΔIo Current change amount ΔIa, ΔIs determination value

Claims (3)

A switching circuit for adjusting output power for arc welding based on the switching operation; and a control circuit for controlling the switching operation, wherein the control circuit determines a short circuit / arc state in the arc welding. An arc welding power supply device comprising: a switching control unit that controls the operation of the switching circuit including determination of the welding state;
The control circuit further includes a current change amount monitoring unit that detects a current change amount of the output current of the power supply device,
Based on the current change amount of the output current during the ON period of the switching circuit acquired through the current change amount monitoring unit, the welding state determination unit is in a short circuit state when the current change amount is larger than a determination value. An arc welding power supply device characterized in that an arc state is determined when the amount of change is smaller than a determination value. In the power supply apparatus for arc welding according to claim 1,
The determination value used in the welding state determination unit is a value in which a determination value for determining a short-circuit state and a determination value for determining an arc state are different from each other, and the arc is set with an interval between them. Power supply for welding. In the adjustment of the output power for arc welding by controlling the switching operation of the switching circuit, a welding state determination method of arc welding for determining a short circuit / arc state,
Based on the current change amount of the output current during the ON period of the switching circuit, it is determined that the short circuit state is present when the current change amount is greater than the determination value, and the arc state is present when the current change amount is smaller than the determination value. A welding state determination method of arc welding characterized by the above.