Welding device

Abstract

The welding device performs consumable electrode type arc welding. The welding device is provided with: a power supply circuit having an inverter circuit and supplying welding power that changes periodically to an arc; and a control circuit that controls the power supply circuit. The control circuit sets a target effective current or a target effective voltage in a period after a current point in time so that a current effective value and a voltage effective value of the welding power exist on a characteristic line corresponding to the set external characteristic, and controls the welding power according to the set target effective current or the target effective voltage so that the current effective value and the voltage effective value of the welding power exist on the characteristic line corresponding to the set external characteristic. The instantaneous welding current or the instantaneous welding voltage is controlled.

Description

Technical Field

[0001] This disclosure relates to welding apparatus. Background Technology

[0002] Conventional welding apparatuses include those for performing consumable electrode arc welding. For example, Patent Document 1 discloses a conventional welding apparatus (welding power source). The welding apparatus described in Patent Document 1 generates a given external characteristic and performs output control corresponding to the generated external characteristic. In this output control, the welding apparatus sets an instantaneous target current value based on the external characteristic and performs sequential control so that the welding current becomes the target current value.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-178763 Summary of the Invention

[0006] -The problem the invention aims to solve-

[0007] In AC welding with alternating current output, the welding current varies sinusoidally, for example. Therefore, in current control based on instantaneous current target values, the welding current and welding voltage may deviate from the external characteristic curve. In other words, it can sometimes be difficult to perform output control corresponding to the external characteristics, and the stability of the arc may decrease. This is not limited to AC welding but can also occur in welding with periodically varying welding power output (e.g., DC pulse welding).

[0008] This disclosure was made in view of the above circumstances, and its object is to provide a welding apparatus that can suppress the decrease in arc stability in welding with periodically varying welding power output.

[0009] -Methods for solving problems-

[0010] The welding apparatus provided by this disclosure is a welding apparatus for performing consumable electrode arc welding, comprising: a power supply circuit having an inverter circuit for supplying periodically varying welding power to the arc; and a control circuit for controlling the power supply circuit, wherein the control circuit sets a target effective current or a target effective voltage for the next cycle from the current time point, such that the effective current value and effective voltage value of the welding power exist on a characteristic line corresponding to the set external characteristics, and controls the instantaneous welding current or instantaneous welding voltage according to the set target effective current or target effective voltage.

[0011] In a preferred embodiment of the welding apparatus, the control circuit sets the target effective current or the target effective voltage for each cycle of the welding power.

[0012] In a preferred embodiment of the welding apparatus, the control circuit calculates the waveform of the welding current based on the set target effective current, or the waveform of the welding voltage based on the set target effective voltage, with a calculation cycle shorter than one cycle of the welding power, and sets the target effective current or the target effective voltage for each calculation cycle.

[0013] In a preferred embodiment of the welding apparatus, the control circuit uses the effective value of the current and the effective value of the voltage in the previous cycle from the current time point to calculate the target effective current in the next cycle from the current time point, and determines the current waveform in the next cycle from the current time point, so that the effective value of the welding current in the next cycle from the current time point becomes the target effective current in the next cycle from the current time point.

[0014] In a preferred embodiment of the welding apparatus, the control circuit uses the target effective current from the previous cycle from the current time point instead of the effective current value from the previous cycle from the current time point.

[0015] In a preferred embodiment of the welding apparatus, the control circuit uses the target effective voltage from the previous cycle from the current time point instead of the effective voltage value from the previous cycle from the current time point.

[0016] In a preferred embodiment of the welding apparatus, the control circuit uses the target effective current from the previous cycle from the current time point to replace the effective current value from the previous cycle from the current time point, and uses the average value of the instantaneous output voltage from the previous cycle from the current time point to replace the effective voltage value from the previous cycle from the current time point.

[0017] In a preferred embodiment of the welding apparatus, the set current is set to Iset, the set voltage is set to Vset, the slope of the characteristic line corresponding to the external characteristic through the set current Iset and the set voltage Vset is set to R, the AC period is set to Δt, the virtual inductance is set to L, the target effective current in the previous period from the current time point is set to Itgt(n-1), and the effective value of the output voltage in the previous period from the current time point is set to Vfb. The control circuit calculates the target effective current Itgt(n) in the next period from the current time point through the operation shown in equation (1) below.

[0018] [Number 1]

[0019]

[0020] In a preferred embodiment of the welding apparatus, the power supply circuit supplies alternating current to the electric arc as the welding power.

[0021] In a preferred embodiment of the welding apparatus, an operation unit is further provided that can specify the parameters of the external characteristic. The control circuit can switch between a standard value mode and a free setting mode. In the standard value mode, a standard value corresponding to welding-related information is set as the setting value of the external characteristic. In the free setting mode, a specified value specified by the operation unit is set as the setting value of the external characteristic.

[0022] -Invention Effects-

[0023] The welding apparatus of this disclosure sets a target effective current or a target effective voltage so that the effective values ​​of the welding current and welding voltage exist on the characteristic lines corresponding to the external characteristics, thereby controlling the instantaneous welding current or instantaneous welding voltage. Therefore, the welding current and welding voltage are controlled by effective values, not instantaneous target values, thus enabling output control corresponding to the external characteristics even when the welding current varies sinusoidally or pulsedly. In other words, according to the welding apparatus of this disclosure, in welding with periodically varying welding power output, the reduction in arc stability can be suppressed. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing a structural example of the welding apparatus according to the first embodiment.

[0025] Figure 2 This is a diagram illustrating a structural example of the power supply device of the welding apparatus according to the first embodiment.

[0026] Figure 3 This is a diagram illustrating an example of the external characteristics set in the power supply device (control circuit) of the welding apparatus according to the first embodiment.

[0027] Figure 4 This is a flowchart illustrating an example of current control performed by the power supply device (control circuit) of the welding apparatus according to the first embodiment.

[0028] Figure 5 This is a flowchart illustrating an example of current control performed by the power supply device (control circuit) of the welding apparatus according to the second embodiment.

[0029] Figure 6This is an example of a waveform representing one cycle of the alternating current and welding voltage.

[0030] Figure 7 This is a diagram illustrating an example of the operation of the welding apparatus according to the fifth embodiment.

[0031] Figure 8 This is a diagram illustrating a structural example of the welding apparatus involved in the modified example.

[0032] Figure 9 This is a schematic diagram showing a structural example of the welding apparatus according to the sixth embodiment. Detailed Implementation

[0033] Hereinafter, preferred embodiments of the welding apparatus of this disclosure will be described with reference to the accompanying drawings. Hereinafter, the same or similar structural elements will be labeled with the same reference numerals, and repeated descriptions will be omitted.

[0034] Figure 1 and Figure 2 This is a structural diagram showing the welding apparatus A1 according to the first embodiment. The welding apparatus A1 performs submerged arc welding. Figure 1 As shown, the welding apparatus A1 includes a control device 1, a power supply device 2, a trolley 4, a wire feed device 5, a wire reel 6, a distribution device 7, and an electrode 8. While moving the trolley 4 along the welding line of the workpiece W, the welding apparatus A1 distributes granular flux stored in the hopper of the distribution device 7, and feeds the wire into the flux via the wire feed device 5. The wire is supplied from the wire reel 6. The power supply 2 converts the AC power supplied from a commercial power source P into welding-appropriate power and outputs it, generating an electric arc between the tip of the wire, i.e., the electrode 8, and the workpiece W within the flux. Welding is performed by the heat of this electric arc. Thus, welding is performed along the welding line of the workpiece W. Alternatively, the workpiece W can be moved or rotated instead of using the trolley 4.

[0035] Control device 1 performs various controls on welding apparatus A1. Control device 1 can be installed on a general-purpose computer with a program for controlling welding apparatus A1, or it can be a dedicated device for controlling welding apparatus A1. Control device 1 moves trolley 4 at a given speed. The speed is set according to the material and thickness of the workpiece W being welded. Control device 1 instructs the dispensing device 7 to distribute flux. Control device 1 instructs the wire feed device 5 to start and stop the wire feeding. It also instructs the wire feed speed, which is set according to the set welding current, etc. Control device 1 instructs the power supply device 2 to output power. Furthermore, control device 1 sets the welding current and welding voltage through user operation and outputs these settings to power supply device 2 (control circuit 28 described later). The set values ​​for welding current and welding voltage are, for example, effective values.

[0036] Power supply unit 2 converts the AC power supplied from commercial power supply P into AC power of the desired frequency. Power supply unit 2 supplies the converted AC power to the arc as welding power. Alternatively, a structure in which multiple power supply units 2 are connected in parallel (specifically, the output terminals a of each power supply unit 2 are connected to each other and to the workpiece W, and the output terminals b are connected to each other and to the welding wire) can also be used instead of power supply unit 2.

[0037] like Figure 2 As shown, the power supply device 2 includes a power supply circuit 20, a current sensor 26, a voltage sensor 27, and a control circuit 28.

[0038] The power supply circuit 20 converts the AC power supplied from the commercial power source P into AC power of the desired frequency. The power supply unit 2 supplies the converted AC power to the electric arc as welding power. The power supply circuit 20 includes a rectifier and smoother circuit 21, an inverter circuit 22, a transformer 23, a rectifier and smoother circuit 24, and an inverter circuit 25. However, the power supply circuit 20 is not limited to this structure; it can be used as long as it can output AC power (welding power).

[0039] The rectifier-smoothing circuit 21 converts the AC power input from the commercial power supply P into DC power and outputs it. The rectifier-smoothing circuit 21 includes a rectifier circuit for rectifying the AC current and a smoothing capacitor for smoothing the current. Furthermore, the structure of the rectifier-smoothing circuit 21 is not limited.

[0040] Inverter circuit 22 is, for example, a single-phase full-bridge PWM-controlled inverter with four switching elements. Inverter circuit 22 switches the switching elements according to the drive signal input from control circuit 28, thereby converting the DC power input from rectifier smoothing circuit 21 into high-frequency power and outputting it. Alternatively, inverter circuit 22 can simply convert DC power to high-frequency power; for example, it can be a half-bridge type or other inverter circuit structures.

[0041] Transformer 23 transforms the high-frequency voltage output from inverter circuit 22 and outputs it to rectifier smoothing circuit 24. Transformer 23 has a primary winding 23a and a secondary winding 23b. Each input terminal of the primary winding 23a is connected to each output terminal of inverter circuit 22. Each output terminal of the secondary winding 23b is connected to each input terminal of rectifier smoothing circuit 24. The output voltage of inverter circuit 22 is transformed according to the turns ratio of primary winding 23a and secondary winding 23b and input to rectifier smoothing circuit 24. Secondary winding 23b is insulated from primary winding 23a, thus preventing current from the commercial power supply P from flowing through the secondary circuit. Furthermore, transformer 23 transforms the high-frequency voltage output from inverter circuit 22, thus it is smaller and lighter than transformers that transform the AC voltage of commercial power supply P.

[0042] The rectifier-smoothing circuit 24 converts the high-frequency power input from the transformer 23 into DC power and outputs it. The rectifier-smoothing circuit 24 includes a rectifier circuit for rectifying the high-frequency current and a DC reactor for smoothing. Furthermore, the structure of the rectifier-smoothing circuit 24 is not limited.

[0043] Inverter circuit 25 is, for example, a single-phase full-bridge PWM-controlled inverter with four switching elements. Inverter circuit 25 switches the switching elements according to the drive signal input from control circuit 28, thereby converting the DC power input from rectifier-smoothing circuit 24 into AC power and outputting it. Alternatively, inverter circuit 25 can simply convert DC power to AC power; for example, it can be a half-bridge type or other inverter circuit structures.

[0044] The current sensor 26 detects the output current (welding current) of the power supply unit 2. In this embodiment, the current sensor 26 is disposed on the connection line connecting one output terminal of the inverter circuit 25 to output terminal a. The welding current detected by the current sensor 26 is approximately equal to the current flowing through the electrode 8. The current sensor 26 outputs a current value signal corresponding to the instantaneous value of the detected current to the control circuit 28. Furthermore, the structure of the current sensor 26 is not limited, as long as it detects current from the connection line. Moreover, the placement location of the current sensor 26 is not limited. For example, the current sensor 26 may also be disposed on the connection line connecting the other output terminal of the inverter circuit 25 to output terminal b. Alternatively, the current sensor 26 may be disposed externally to the power supply unit 2.

[0045] Voltage sensor 27 detects the output voltage (welding voltage) of power supply device 2. In this embodiment, voltage sensor 27 detects the voltage between output terminal a and output terminal b. This voltage is approximately equal to the voltage applied between the workpiece W (base material) and the tip of electrode 8 (welding torch). Voltage sensor 27 outputs a voltage value signal corresponding to the detected instantaneous voltage value to control circuit 28. Furthermore, the structure of voltage sensor 27 is not limited, as long as it is a structure that detects the voltage between output terminal a and output terminal b. Moreover, the placement location of voltage sensor 27 is not limited. Voltage sensor 27 can also be disposed externally to power supply device 2, for example, it can be configured to detect the tip voltage between workpiece W (base material) and electrode 8 (welding torch).

[0046] Control circuit 28 is a circuit used to control power supply device 2, and is implemented, for example, by a microcomputer. Control circuit 28 receives current value signals from current sensor 26 and voltage value signals from voltage sensor 27. Control circuit 28 outputs drive signals to each inverter circuit 22 and 25 respectively.

[0047] Control circuit 28 controls the welding power (AC power) applied to the arc so that the effective values ​​of the current and voltage exist on the characteristic line (hereinafter referred to as the "external characteristic line") corresponding to the desired external characteristics. Hereinafter, this control is sometimes referred to as "external characteristic effective value control." The external characteristic represents the relationship between the welding current and the welding voltage; in this embodiment, the external characteristic is set by the relationship between the effective values ​​of the current and the effective values ​​of the voltage. Furthermore, the external characteristic in this embodiment is, for example, a constant voltage characteristic, but it could also be a drooping characteristic or a constant current characteristic, or other characteristics. The external characteristic is represented by a function corresponding to that characteristic, and the formula based on this function is set in control circuit 28. For example, Figure 3 This is a graph illustrating an example of constant voltage characteristics. The horizontal axis of the graph represents the effective value of the welding current, and the vertical axis represents the effective value of the welding voltage. Figure 3The external characteristic shown is a straight line passing through the point (Ie, Ve) where the voltage becomes V0 when the current is 0 (Ie is the effective value of the current, and Ve is the effective value of the voltage). However, the external characteristic is not limited to a straight line; it can also be a curve, and the function corresponding to the external characteristic can be a separate expression. In this embodiment, the case where the control circuit 28 controls the welding power through current control is used as an example for explanation, but the welding power can also be controlled through voltage control.

[0048] Control circuit 28 sets the target effective current in the nth cycle (n is a positive integer) of the AC power, so that the effective values ​​of the current and voltage in the nth cycle exist on the set external characteristic line (e.g., refer to...). Figure 3 In the case where the power supply unit 2 controls the welding power through current control, the control circuit 28 sets the target effective current. In this case, the control circuit 28 calculates the effective value of the AC voltage Ve (effective voltage value) for n-1 cycles based on the voltage value signal input from the voltage sensor 27. Then, the effective voltage value for the n-1th cycle is applied to the above-mentioned formula for the external characteristics to derive the effective value of the AC current for the n-1th cycle (effective current value Ie), and the derived effective current value Ie for the n-1th cycle is set as the target effective current for the nth cycle.

[0049] When setting a target effective current, control circuit 28 generates a current waveform command signal based on the set target effective current. The current waveform command signal represents the current waveform of the nth cycle, which can be, for example, a sine wave, but also other waveforms such as a rectangular wave (trapezoidal wave). For example, when using a perfect sine wave as the current waveform, this current waveform is a sine wave where the peak current is √2 times the target effective current. Control circuit 28 generates the current waveform command signal with a cycle shorter than one cycle of the welding power (alternating current welding current). Unlike this structure, in this embodiment, one cycle of the welding power and the cycle for generating the current waveform command signal can be the same.

[0050] When generating the current waveform command signal, control circuit 28 generates a drive signal for controlling the switching elements of inverter circuit 22 based on the current value signal input from current sensor 26 and the internally generated current waveform command signal, and outputs it to inverter circuit 22. Furthermore, based on the current waveform command signal, it controls the switching elements of inverter circuit 25 to generate a drive signal for switching the power supply polarity to electrode positive and electrode negative polarities, and outputs it to inverter circuit 25. In other words, control circuit 28 performs feedback control to ensure that the waveform of the welding current matches the waveform commanded by the waveform command signal. Thus, an alternating current corresponding to the current waveform command signal is output from power supply unit 2. The generation period of the drive signals for each inverter circuit 22, 25 is, for example, shorter than the generation period of the aforementioned current waveform command signal. Alternatively, control circuit 28 may generate drive signals based solely on the current waveform command signal without using the current value signal.

[0051] Furthermore, unlike the example above, when welding power is controlled by voltage control, the control circuit 28 performs the following processing. First, the control circuit 28 sets the target effective voltage. In this case, the control circuit 28 calculates the effective value Ie (effective current value) of the AC current for n-1 cycles based on the current value signal input from the current sensor 26. Then, the effective current value Ie for the n-1th cycle is applied to the above-mentioned formula for the external characteristic to derive the effective value Ve (effective voltage value) of the AC voltage for the n-1th cycle, and the derived effective voltage value Ve for the n-1th cycle is set as the target effective voltage for the nth cycle. When setting the target effective voltage, the control circuit 28 generates a voltage waveform command signal based on the set target effective voltage. The voltage waveform command signal is a signal representing the voltage waveform for the nth cycle, which may be, for example, a sine wave, but may also be other waveforms such as a rectangular wave (trapezoidal wave). When generating the voltage waveform command signal, the control circuit 28 generates drive signals for controlling the switching elements of each inverter circuit 22, 25 based on the voltage value signal input from the voltage sensor 27 and the waveform command signal generated internally, and outputs these signals to the corresponding inverter circuits 22, 25. In other words, the control circuit 28 performs feedback control to ensure that the waveform of the welding voltage matches the waveform commanded by the voltage waveform command signal. Consequently, the power supply unit 2 outputs an AC voltage corresponding to the voltage waveform command signal.

[0052] Figure 4 This is a flowchart illustrating the current control of the welding power performed by the control circuit 28 in the welding apparatus A1. Figure 4 The flowchart shown illustrates the case where control circuit 28 controls welding power via current control, but welding power can also be controlled via voltage control. In this case, Figure 4 You can simply replace "voltage" and "current" with their respective values.

[0053] First, the control circuit 28 calculates the effective voltage value of the previous AC cycle based on the voltage signal input from the voltage sensor 27 (S101). There are no limitations on the method for calculating the effective value. Furthermore, since there is no voltage signal from the previous AC cycle after the initial output of welding power, the set voltage can be used as the effective voltage value of the previous AC cycle.

[0054] Next, the effective voltage value of the previous cycle is applied to the function of the external characteristic to derive the effective current value of the previous AC cycle (S102). Thus, the effective voltage and effective current values ​​of the previous AC cycle are obtained. Since the effective current value is derived using the function of the external characteristic, both the effective voltage and effective current values ​​exist on the external characteristic line.

[0055] Next, the effective value of the current from the previous AC cycle is set as the target effective current for the current AC cycle (S103).

[0056] Next, a current waveform command signal is generated, such that the effective value of the current in the current AC cycle becomes the set target effective current (S104). For example, the waveform commanded by the generated current waveform command signal is a sine wave.

[0057] Next, the instantaneous welding current is controlled so that the current value signal input from the current sensor 26 becomes a waveform commanded by the current waveform command signal (S105).

[0058] During the output of welding power, welding device A1 repeatedly performs current control from steps S101 to S105 according to each AC cycle. Furthermore, in the above control example, the previous cycle and the current cycle can be divided based on a certain point in time of the AC cycle of the welding power (e.g., the timing of switching from negative to positive), or they can be divided based on the current point in time, from the period before one cycle of the AC cycle to the period after one cycle of the AC cycle.

[0059] In welding apparatus A1, a target effective current is set, and the instantaneous current is controlled so that the effective values ​​of the welding current and welding voltage (effective current and effective voltage) exist on the external characteristic line. Based on this structure, the instantaneous current is controlled with a target effective value, thus enabling output control corresponding to the external characteristics in welding with AC welding power. This is not limited to the case of output control of welding power via current control; the same applies to the case of output control of welding power via voltage control. In other words, by setting a target effective voltage instead of a target effective current to control the instantaneous voltage, output control corresponding to the external characteristics can be performed in welding with AC welding power. Therefore, welding apparatus A1 can suppress the decrease in arc stability in welding with AC power output (whether current-controlled or voltage-controlled). Furthermore, welding apparatus A1 is not limited to outputting AC power; it can also suppress the decrease in arc stability in welding with periodically varying welding power output (e.g., DC pulse welding).

[0060] Next, the welding apparatus A2 according to the second embodiment will be described. The calculation method for the target effective current in the welding power control differs between welding apparatus A2 and welding apparatus A1. The structure of welding apparatus A2 is similar to that of welding apparatus A1 (see reference). Figure 1 )same.

[0061] The control circuit 28 of the welding device A2 is described below. It sets the target effective current in the AC cycle of the nth cycle of the AC power so that the effective values ​​of the current and voltage in the AC cycle of the nth cycle exist on the set external characteristic line. Assume that the set current is Iset, the set voltage is Vset, and the external characteristic line is a straight line with a slope of R passing through the point (Iset, Vset) on the IV plane. In addition, the AC cycle is set to Δt, the virtual inductance is set to L, the effective value of the welding current in the (n-1)th cycle is set to Ifb, and the effective value of the welding voltage in the (n-1)th cycle is set to Vfb. The control circuit 28 calculates the target effective current Itgt(n) in the AC cycle of the nth cycle using the following equation (2).

[0062] [Number 2]

[0063]

[0064] The above equation (2) is derived from the following equation (3) described in Patent Document 1 (Equation (3) in Patent Document 1). In the following equation (3), Irc is the welding current control setting value, which is the instantaneous command current at that point in time. Furthermore, in the following equation (3), Lr is the inductance setting value, v is the welding voltage, and i is the welding current.

[0065] Irc=∫((Er(i)v) / Lr)dt···(3)

[0066] In equation (3) above, the relationship v = Er(i) represents the external characteristic. Here, in equation (3) above, if the output voltage setting value (equivalent to the above-mentioned setting voltage Vset) is set to Er, and the output current setting value (equivalent to the above-mentioned setting current Iset) is set to Ir, then in Patent Document 1, the external characteristic is given by a straight line passing through the point (0, Er) with a slope of Rr, and the function of the external characteristic is as follows (4). In contrast, in welding apparatus A2, the external characteristic is given by a straight line passing through the point (Ir, Er) with a slope of Rr, and the function of the external characteristic is as follows (5).

[0067] Er(i)=Er-Rr·I···(4)

[0068] Er(i)=Er-Rr·i-Ir)···(5)

[0069] If we substitute equation (5) into equation (3) above, then Irc = ∫((Er-Rr·(i-Ir)-v) / Lr)dt. If we differentiate both sides using t, we get equation (6) below.

[0070] dIrc / dt=(Er-Rr·(i―Ir)-v) / Lr···(6)

[0071] Furthermore, if the effective value of the output current in the nth cycle is set as Itgt(n), and the feedback current (the effective value of the output current in the (n-1)th cycle) is set as Ifb, then the left side of the above equation (6) becomes dIrc / dt≈(Itgt(n)-Ifb) / Δt. In addition, since the control is performed with the welding current i=Itgt(n), the right side of the above equation (6) becomes (Er-Rr·(Itgt(n)―Ir)-v) / Lr. If Itgt(n) is solved, the following equation (7) is obtained.

[0072] Itgt(n)={Lr·Ifb+Δt(Er+Rr·Ir-v)} / (Lr+Rr·Δt)···(7)

[0073] Here, in the symbols of the above equation (7), the output voltage setting value Er is equivalent to the setting voltage Vset in the welding device A2, the output current setting value Ir is equivalent to the setting current Iset in the welding device A2, the inductance setting value Lr is equivalent to the virtual inductance L in the welding device A2, the slope of the external characteristic line Rr is equivalent to the slope of the external characteristic line R in the welding device A2, and the welding voltage v is equivalent to the feedback voltage (the effective value of the welding voltage in the (n-1)th cycle) Vfb in the welding device A2. Therefore, if we replace it with Er→Vset, Ir→Iset, Lr→L, Rr→R, v→Vfb, it becomes the above equation (2). Thus, in Patent Document 1, the formula for the target value to become an instantaneous value is extended to the formula for the target value to become an effective value in the welding device A2.

[0074] Figure 5 This is a flowchart illustrating the current control of welding power performed by the control circuit 28 in welding apparatus A2. Compared to the current control of welding power in welding apparatus A1, the current control of welding power in welding apparatus A2 changes from step S101 to step S103, and steps S201 and S202 are performed.

[0075] First, the control circuit 28 calculates the effective voltage value of the previous AC cycle based on the voltage signal input from the voltage sensor 27, and calculates the effective current value of the previous AC cycle based on the current signal input from the current sensor 26 (S201). There are no limitations on the method for calculating the effective values. Furthermore, after the welding power output begins, since there are no voltage and current signals from the previous AC cycle, the set voltage and set current can be used as the effective voltage and current values ​​of the previous AC cycle.

[0076] Next, the control circuit 28 calculates the target effective current Itgt(n) of the current AC cycle using the formula corresponding to the external characteristics, namely formula (2) above (S202). At this time, formula (2) above is a formula corresponding to the external characteristics. If the target effective current Itgt(n) is obtained using this formula, then the effective values ​​of the welding current and welding voltage of the current AC cycle exist on the external characteristic line. This is because the instantaneous value is derived by replacing the effective value in formula (3) described in Patent Document 1. Then, the control circuit 28 sets the target effective current Itgt(n) to the calculated value.

[0077] Subsequently, the control circuit 28 performs the same process as the control circuit 28 in the welding apparatus A1 to generate the aforementioned current waveform command signal (step S104) and control the aforementioned instantaneous welding current (step S105).

[0078] Like welding apparatus A1, welding apparatus A2 sets a target effective current based on the effective values ​​of welding current and welding voltage (effective current and effective voltage) existing on the external characteristic line, and controls the instantaneous current. Therefore, like welding apparatus A1, welding apparatus A2 controls the instantaneous current with a target effective value, thus enabling output control corresponding to external characteristics in welding with AC power output. In other words, welding apparatus A2 can suppress the decrease in arc stability in welding with AC power output.

[0079] Next, the welding apparatus A3 according to the third embodiment will be described. The calculation formula for the target effective current Itgt(n) differs between welding apparatus A3 and welding apparatus A2. The structure of welding apparatus A3 is different from the structure of welding apparatus A2 (i.e., the structure of welding apparatus A1: see [reference]). Figure 1 )same.

[0080] The control circuit 28 of welding apparatus A3 uses the target effective current Itgt(n-1) in the AC cycle of the (n-1)th cycle to replace the effective value Ifb of the welding current in the (n-1)th cycle in the above equation (2). In other words, the control circuit 28 of welding apparatus A3 calculates the target effective current Itgt(n) in the AC cycle of the nth cycle through the operation of the following equation (8). Especially in submerged arc welding, it is not easy to cause a sharp load change on the secondary side caused by short circuits, etc. Therefore, in the (n-1)th cycle, the effective value Ifb of the welding current becomes a value that is approximately close to the target effective current Itgt(n-1). In other words, the target effective current Itgt(n-1) can be used instead of the effective value Ifb of the current. The control circuit 28 in welding apparatus A3 can be modified from the control circuit 28 in welding apparatus A2 by changing the operation formula used in the process of step S202 to the following equation (8).

[0081] [Number 3]

[0082]

[0083] Like welding apparatus A2, welding apparatus A3 sets a target effective current based on the effective values ​​of welding current and welding voltage (effective current and effective voltage) existing on the external characteristic line, controlling the instantaneous current. Therefore, in welding with AC welding power output, it can suppress the decrease in arc stability. Furthermore, compared to welding apparatus A2, welding apparatus A3 does not require the calculation of the effective current value Ifb. Therefore, compared to welding apparatus A2, welding apparatus A3 can reduce computational complexity.

[0084] Next, the welding apparatus A4 according to the fourth embodiment will be described. The calculation formula for the target effective current Itgt(n) differs between welding apparatus A4 and welding apparatus A3. The structure of welding apparatus A4 is different from the structure of welding apparatus A3 (i.e., the structure of welding apparatus A1: see [reference]). Figure 1 )same.

[0085] The control circuit 28 in welding apparatus A4 uses the average value Vavg(n-1) of the welding voltage in the (n-1)th cycle to replace the effective value Vfb of the welding voltage in the (n-1)th cycle in equation (8) above. In other words, the control circuit 28 of welding apparatus A4 calculates the target effective current Itgt(n) in the AC cycle of the nth cycle through the operation of equation (9) below. The welding current varies (controlled) in various forms, such as the sine wave waveform described above, but the welding voltage is as follows: Figure 6 As shown, the shape is not necessarily similar to the welding current, but rather resembles a rectangular wave. This is because a fixed voltage is required to maintain the arc. In such a rectangular wave waveform, the difference between the effective value and the average value becomes smaller, so the effective value Vfb of the welding voltage in the (n-1)th cycle can be approximated by the average value Vavg(n-1). The control circuit 28 in welding apparatus A4 can be modified from the control circuit 28 in welding apparatus A2 by changing the formula used in the process of step S202 to the following formula (9).

[0086] [Number 4]

[0087]

[0088] Like welding devices A2 and A3, welding device A4 sets a target effective current based on the effective values ​​of welding current and welding voltage (effective current and effective voltage) existing on the external characteristic line, controlling the instantaneous current. Therefore, in welding with AC welding power output, it can suppress the decrease in arc stability. Furthermore, compared to welding device A3, welding device A4 does not require the calculation of the effective voltage value Vfb. Therefore, welding device A4 reduces the computational load compared to welding device A3. In other words, compared to welding device A2, welding device A4 does not require the calculation of both the effective current value and the effective voltage value, thus significantly reducing the computational load compared to welding device A2.

[0089] In the second to fourth embodiments described above, examples are shown of the power supply device 2 controlling the welding power through current control, but it is not limited to this. The power supply device 2 can also control the welding power through voltage control. In this case, equations (2), (8), and (9) above can be replaced with formulas corresponding to the external characteristics with the target effective voltage of the welding power in the nth cycle as the left side. Detailed explanation of these formulas is omitted.

[0090] Next, the welding apparatus A5 according to the fifth embodiment will be described. The welding apparatus A5 differs from the welding apparatus A1 in the calculation cycle of the target effective current (or target effective voltage). Specifically, in the welding apparatus A1, the control circuit 28 calculates the target effective current (or target effective voltage) in each AC cycle of the AC power (welding power), but in the welding apparatus A5, the control circuit 28 calculates the target effective current (or target effective voltage) in each generation cycle of the current waveform command signal (or voltage waveform command signal). Hereinafter, an example of calculating (setting) the target effective current to control the welding current (AC current) will be described, but the same applies to the case of calculating (setting) the target effective voltage to control the welding voltage (AC voltage).

[0091] The control circuit 28 of welding apparatus A5 generates a current waveform command signal based on the set target effective current, similar to the control circuit 28 of welding apparatus A1. The generation of this current waveform command signal is shorter than one cycle of the AC welding power (e.g., welding current). The same applies to the control circuit 28 of welding apparatus A1. In other words, the control circuit 28 generates the current waveform command signal with a calculation period shorter than one cycle of the AC welding power (welding current). For example, if one cycle of the AC welding power (welding current) is 20 ms (the frequency of the welding power is 50 Hz), the calculation period of the current waveform command signal is 50 μsec. However, the relationship between one cycle of the AC welding power (welding current) and the calculation period of the current waveform command signal is not limited to this example. In the relationship between the AC power cycle and the calculation period of the current waveform command signal, the control circuit 28 of welding apparatus A5 calculates (sets) the target effective current during the timing of generating the current waveform command signal. In other words, in the control circuit 28 of welding apparatus A5, the start of the calculation period of the current waveform command signal is taken as the start of the nth period of the calculation period of the target effective current, and the target effective current of the nth period is set in each calculation period of the current waveform command signal. Therefore, in welding apparatus A5, the period for calculating (setting) the target effective current is shorter than that in welding apparatus A1. Furthermore, in the control circuit 28 of welding apparatus A5, the method for calculating the target effective current can also use any of the methods described in welding apparatuses A1 to A4. In this embodiment, the nth period is the period from the current time point to one cycle of welding power (AC power), and the (n-1)th period is the period from the current time point to one cycle of welding power (AC power).

[0092] Figure 7 This diagram illustrates the operation of welding apparatus A5, showing the waveform of the welding current. Figure 7In this diagram, T1 is one cycle of the welding power (alternating current), and T2 is the calculation cycle of the current waveform command signal. In the illustrated example, T2 is 1 / 8 of T1, but the ratio of T1 to T2 is not fixed. Furthermore, in... Figure 7 During the period shown, the effective value of the welding current did not change significantly.

[0093] At time point t1, control circuit 28 uses information from the period preceding one cycle T1 from time point t1 to calculate and set the target effective current. Furthermore, as described above, the calculation of this target effective current can be performed using any of the welding apparatuses A1 to A4 described above. Then, based on the target effective current set at time point t1, control circuit 28 generates a current waveform command signal regarding the current waveform from time point t1 to the period following one cycle T1.

[0094] Next, at time point t2 (=t1+T2), after the aforementioned calculation period T2 from time point t1, control circuit 28 uses information from the period preceding one period T1 starting from time point t2 to calculate and set the target effective current. Then, based on the target effective current set at time point t2, control circuit 28 generates a current waveform command signal for the current waveform from time point t2 to the period following one period T1. The same process is repeated at time point t3 (=t2+T2).

[0095] As understood from the above example, in the control circuit 28 of the welding apparatus A5, the target effective current is updated for each calculation cycle T2 of the current waveform command signal. Then, based on the updated target effective current, a current waveform command signal is generated to control the welding current.

[0096] In welding apparatus A5, the target effective current is updated with a shorter cycle (calculation cycle of the current waveform command signal) than that of welding apparatuses A1 to A4. During welding, the welding voltage varies according to the arc length. Welding apparatus A5 can improve the current response to voltage variations in response to these welding voltage changes.

[0097] In the first to fifth embodiments described above, an example is shown where the control circuit 28 controls the welding power so that it exists on a characteristic line corresponding to a preset external characteristic. Alternatively, a different configuration may be implemented, allowing adjustment of the preset external characteristic. Figure 8 This indicates the welding apparatus involved in such a variation. Additionally, in Figure 8 The document describes the control circuit 28 and the control device 1, with other structures similar to those described above. Figure 1 as well as Figure 2 same.

[0098] Figure 8The welding apparatus shown includes an operation unit 91 and a display unit 92. In the illustrated example, the operation unit 91 and the display unit 92 are located in the control device 1. In contrast, the operation unit 91 and the display unit 92 may also be located in the power supply device 2. In this case, the operation unit 91 and the display unit 92 are connected to the control circuit 28.

[0099] The operation unit 91 accepts user operations. The operation unit 91 inputs values ​​for various parameters of the external characteristic through user operations. These parameters include the type of external characteristic (constant voltage, constant current, or drooping characteristic) and the slope of the external characteristic line. The parameters of the external characteristic are not limited to these two parameters. In one example, the slope of the external characteristic line can be specified within the range of -0.5V / 100A to 40V / 100A via the operation unit 91. Furthermore, the value of the slope of the external characteristic line can be specified, but it is not limited to this range. For example, the slope of the external characteristic line can be specified as 0 (e.g., 0V / 100A), thereby allowing the specification of a completely constant current characteristic (current remains constant even when voltage changes) or a completely constant voltage characteristic (voltage remains constant even when current changes) through combination with the type of external characteristic. The control device 1 outputs the values ​​of the external characteristic parameters specified by the operation unit 91 to the power supply device 2 (control circuit 28).

[0100] The display unit 92 may be composed of, for example, a liquid crystal display, an OEL (Organic Electro-Luminescence) display, or a segmented display. The display unit 92 displays various information about the welding apparatus. For example, when the operation unit 91 specifies the parameters of the external characteristics, the display unit 92 displays the values ​​of each parameter.

[0101] The control circuit 28 includes an external characteristic setting unit 281. The external characteristic setting unit 281 switches between a standard value mode and a free setting mode. The standard value mode sets a standard value corresponding to welding-related information as the external characteristic to be set. Welding-related information includes, for example, the welding polarity (AC, DC negative, or DC positive), control method (constant voltage control mode (constant feed rate control mode), constant current control mode (variable feed rate control mode)), welding current, and welding voltage settings. Welding-related information is not limited to these. The standard value is a value recommended for this welding-related information. The free setting mode sets a specified value (input) by the operation unit 91 as the external characteristic to be set. The external characteristic setting unit 281 is set to free setting mode when the values ​​of each parameter of the external characteristic are specified through the operation of the operation unit 91, that is, when the specified values ​​of each parameter of the external characteristic are input from the operation unit 91. On the other hand, if the values ​​of each parameter of the external characteristic are not specified through the operation of the operation unit 91, that is, if the values ​​of each parameter of the external characteristic specified from the operation unit 91 are not entered, the standard value mode is set.

[0102] In standard value mode, control circuit 28 uses the recommended standard value as the external characteristic and performs effective value control of the external characteristic as shown in the first to fifth embodiments. On the other hand, in free setting mode, the specified value designated by operation unit 91 is used as the external characteristic, and effective value control of the external characteristic as shown in the first to fifth embodiments is performed.

[0103] exist Figure 8 In the welding apparatus described in the modified example, the user can easily adjust the appropriate parameters of the external characteristics (type of external characteristics and slope of the external characteristic line) according to the welding object, welding material, feed control method, wire protrusion length, and other welding conditions. For example, for operators with low welding skill, using standard (recommended) external characteristics in the standard value mode can suppress the reduction of welding quality. On the other hand, for operators with high welding skill, the parameters of the external characteristics can be adjusted according to the aforementioned welding conditions in the free setting mode, thereby improving welding quality.

[0104] The ability to adjust the aforementioned external characteristics (parameters) is not limited to welding apparatuses that perform AC welding. For example, it can also be applied to welding apparatuses that perform DC pulse welding, and also to welding apparatuses that perform DC welding.

[0105] Next, the welding apparatus A6 according to the sixth embodiment will be described. The welding apparatus A6 differs from the welding apparatus A1 in the following aspects. It differs in that the control device 1 provides feedback control of the output voltage (RMS value) of the power supply device 2 by adjusting the wire feed speed through a variable speed control. For example, the power supply device 2 controls the arc length through a constant voltage characteristic in the external characteristic RMS control. When using a thin-diameter welding wire with a diameter of 1.6 mm or less, the arc length is appropriately controlled by the constant voltage characteristic. However, in submerged arc welding, welding wires with diameters of, for example, 2.4 mm, 3.2 mm, 4.0 mm, 4.8 mm, and 6.4 mm are used. Furthermore, the diameter of the welding wire used in the welding apparatus of this disclosure is not limited to these. When a thick-diameter welding wire is used, it is difficult to obtain a control effect on the amount of welding wire melt based on current changes. In the welding apparatus A6 of this embodiment, in addition to arc length control based on constant voltage characteristics, arc length control based on variable speed control of the welding wire feed is also used. Therefore, as... Figure 9 As shown, the control device 1 includes a speed setting unit 11 and a speed correction unit 12 as a functional structure for variable speed control of welding wire feed.

[0106] The speed setting unit 11 is a functional structure that sets a standard wire feed speed, i.e., a reference speed, corresponding to the welding conditions. The speed setting unit 11 stores the reference speed corresponding to the set voltage Vset and outputs the reference speed corresponding to the set voltage Vset to the speed correction unit 12. The reference speed is not limited, but is 10 m / min or less.

[0107] The speed correction unit 12 is a functional structure that sets a set speed after correcting the reference speed input from the speed setting unit 11. The speed correction unit 12 calculates the deviation between the effective voltage value Ve (the effective value of the AC voltage for n-1 cycles) calculated by the control circuit 28 and the set voltage Vset. The speed correction unit 12 performs calculations on the calculated deviation, for example, based on integral control, to calculate a calculated value. Then, the speed correction unit 12 calculates the set speed by adding the integral control calculated value to the reference speed input from the speed setting unit 11. When the effective voltage value Ve is less than the set voltage Vset, the speed correction unit 12 sets a set speed smaller than the reference speed (slower) to the wire feed device 5 by adding a calculated value corresponding to the negative deviation. As a result, the wire feed speed decreases, the arc length increases, and the welding voltage increases. On the other hand, when the effective voltage value Ve is greater than the set voltage Vset, the speed correction unit 12 sets a set speed larger than the reference speed (faster) to the wire feed device 5 by adding a calculated value corresponding to the positive deviation. As a result, the wire feed speed increases, the arc length decreases, and the welding voltage is reduced.

[0108] As described above, the control device 1 of the welding apparatus A6 controls the output voltage of the power supply device 2 to the set voltage Vset by adjusting the wire feed speed. Furthermore, the internal structure of the control device 1 is not limited to the structure described above. The control device 1 controls the output voltage (RMS value) of the power supply device 2 to the set voltage Vset by adjusting the wire feed speed. In the above example, the target effective current Itgt(n) is calculated by the control circuit 28, and the output voltage (RMS value) of the power supply device 2 is controlled to the set voltage Vset by the variable wire feed speed control of the control device 1. However, when the target effective voltage is set by the control circuit 28, the output current (RMS value) of the power supply device 2 can be controlled to the set current Iset by the variable wire feed speed control of the control device 1.

[0109] According to the welding apparatus A6, the power supply unit 2 controls the arc length through the constant voltage characteristic in the external characteristic effective value control. Furthermore, the wire feed device 5 controls the arc length by adjusting the feed speed so that the output voltage (effective voltage value) of the power supply unit 2 becomes the set voltage Vset. Even when using a large-diameter welding wire, where it is difficult to achieve arc length control based on the constant voltage characteristic, the welding apparatus A6 can appropriately control the arc length by incorporating arc length control based on changes in feed speed. Therefore, even when the external characteristic is made constant voltage, the welding apparatus A6 can suppress welding instability.

[0110] In the first to sixth embodiments (and including variations) described above, the function of either the control circuit 28 or the control device 1 can also be built into either the control circuit 28 or the control device 1.

[0111] In the first to sixth embodiments (and including variations) described above, AC welding (welding with AC power output) was used as an example. However, the welding apparatus of this disclosure can be applied to welding apparatuses that output periodically varying welding power (e.g., DC pulse welding with power outputting a DC pulse waveform). In other words, according to the welding apparatus of this disclosure, not only in AC welding, but also in welding with periodically varying welding power output (e.g., DC pulse welding), the reduction in arc stability can be suppressed.

[0112] In the first to sixth embodiments (and including variations) described above, a welding apparatus for submerged arc welding was used as an example. However, the welding apparatus disclosed herein can be any apparatus for performing consumable electrode arc welding (e.g., GMA (GasMetal Arc) welding).

[0113] The welding apparatus disclosed herein is not limited to the embodiments described above. Various design modifications can be made to the specific structures of the various parts of the welding apparatus disclosed herein.

[0114] -Explanation of Figure Markers-

[0115] A1~A6: Welding equipment, 1: Control device, 2: Power supply device, 20: Power supply circuit, 22, 25: Inverter circuit, 28: Control circuit, 281: External characteristic setting unit, 91: Operation unit.

Claims

1. A welding apparatus for performing consumable electrode arc welding. have: The power supply circuit includes an inverter circuit that supplies periodically varying welding power to the electric arc; and Control circuit, controls the power supply circuit, The control circuit sets the target effective current or target effective voltage for the next cycle from the current time point, so that the effective current value and effective voltage value of the welding power exist on the characteristic line corresponding to the set external characteristics, and controls the instantaneous welding current or instantaneous welding voltage according to the set target effective current or target effective voltage.

2. The welding apparatus according to claim 1, wherein, The control circuit sets the target effective current or the target effective voltage for each cycle of the welding power.

3. The welding apparatus according to claim 1, wherein, The control circuit calculates the waveform of the welding current based on the set target effective current, or the waveform of the welding voltage based on the set target effective voltage, with a calculation cycle shorter than one cycle of the welding power, and sets the target effective current or the target effective voltage for each calculation cycle.

4. The welding apparatus according to claim 2 or 3, wherein, The control circuit uses the effective current value and the effective voltage value from the previous cycle starting from the current time point to calculate the target effective current in the next cycle starting from the current time point, and determines the current waveform in the next cycle starting from the current time point, so that the effective value of the welding current in the next cycle starting from the current time point becomes the target effective current in the next cycle starting from the current time point.

5. The welding apparatus according to claim 4, wherein, The control circuit uses the target effective current from the previous cycle starting from the current time point to replace the effective current value from the previous cycle starting from the current time point.

6. The welding apparatus according to claim 4, wherein, The control circuit uses the target effective voltage from the previous cycle starting from the current time point to replace the effective voltage value from the previous cycle starting from the current time point.

7. The welding apparatus according to claim 4, wherein, The control circuit uses the target effective current from the previous cycle from the current time point to replace the effective current value from the previous cycle from the current time point, and uses the average value of the instantaneous output voltage from the previous cycle from the current time point to replace the effective voltage value from the previous cycle from the current time point.

8. The welding apparatus according to claim 5, wherein, The set current is set to Iset, the set voltage is set to Vset, the slope of the characteristic line corresponding to the external characteristic through the set current Iset and the set voltage Vset is set to R, the AC period is set to Δt, the virtual inductance is set to L, the target effective current in the previous period from the current time point is set to Itgt(n-1), and the effective value of the output voltage in the previous period from the current time point is set to Vfb. The control circuit calculates the target effective current Itgt(n) in the next period from the current time point through the operation shown in equation (1) below. [Number 1] 。 9. The welding apparatus according to any one of claims 1 to 3, wherein, The power supply circuit supplies alternating current to the electric arc as the welding power.

10. The welding apparatus according to any one of claims 1 to 3, wherein, It also includes an operation unit capable of specifying parameters for the external characteristics. The control circuit can switch between a standard value mode and a free setting mode. In the standard value mode, a standard value corresponding to welding-related information is set as the setting value of the external characteristic. In the free setting mode, a specified value specified by the operation unit is set as the setting value of the external characteristic.

Images