Pulse arc welding power supply

Abstract

This invention provides a pulsed arc welding power supply with good transient response and steady-state stability when the pulse parameters of the welding current are automatically controlled to an appropriate value in a consumable electrode pulsed arc welding master view. It includes a power control unit (PM) and further includes: a short circuit occurrence period detection unit (TSA) that detects the occurrence period (Tsa) of a short circuit between the welding wire (1) and the base material (2) in each pulse cycle; a cumulative correction amount calculation unit (SD) that calculates a cumulative correction amount (Sd) by accumulating a predetermined correction amount corresponding to the occurrence period (Tsa) of the short circuit in each given pulse cycle; and a pulse parameter correction unit (PC) that corrects the pulse parameters of the waveform of the welding current (Iw) based on the cumulative correction amount (Sd).

Description

Technical Field

[0001] This invention relates to a pulsed arc welding power supply capable of automatically adjusting pulse parameters. Background Technology

[0002] In consumable electrode pulsed arc welding, the welding wire is fed, and during the rise phase, a transition current is applied that rises from the base current to the peak current. During the peak phase, the peak current is applied. During the fall phase, a transition current is applied that falls from the peak current to the base current. During the base phase, the base current is applied. Welding is performed with a welding current that constitutes one pulse cycle. In pulsed arc welding, by setting a state where one droplet transitions every one pulse cycle—a state known as 1-pulse-cycle 1-droplet transition—high-quality welding with low sputtering and good weld appearance can be achieved. To achieve the 1-pulse-cycle 1-droplet transition state, pulse parameters such as the peak period and peak current need to be set to appropriate values.

[0003] Even welding wires conforming to the same JIS standard can have different compositions due to brand variations, resulting in different appropriate values ​​for the pulse parameters. Furthermore, these appropriate values ​​vary depending on factors such as the distance between the welding nozzle and the base material (torch height), feed rate, and welding speed. Therefore, a control method that automatically adjusts the pulse parameters to appropriate values ​​is proposed (see Patent Document 1).

[0004] In the invention of Patent Document 1, the occurrence period of the short circuit between the welding wire and the base material is detected in each pulse cycle, and an index characterizing the distribution of the short circuit occurrence period per unit time is calculated. Based on this index, the pulse parameters in the waveform of the welding current are changed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: JP 2014-226677

[0008] In pulsed arc welding, when welding at high speeds, it is preferable to shorten the arc length by setting the welding voltage lower than the standard value to suppress undercut. However, a shorter arc length makes short circuits more likely and significantly increases the amount of sputtering.

[0009] In the above-described prior art, the pulse parameters can be appropriately adjusted based on the distribution of short-circuit occurrence times per unit time to reduce sputtering generation. However, in the prior art, since it is based on distribution, it takes time to converge to an appropriate value, resulting in poor transient response. Summary of the Invention

[0010] Therefore, the objective of this invention is to provide a pulsed arc welding power source that can achieve good transient response and steady-state stability in the automatic correction control of pulse parameters.

[0011] To address the aforementioned issues, technical solution 1 is a pulsed arc welding power supply that feeds a welding wire and includes an electrical control unit that outputs a transition current rising from a base current to a peak current during the rise period, outputs the peak current during the peak period, outputs a transition current falling from the peak current to the base current during the fall period, outputs the base current during the base period, and outputs a welding current with these outputs as one pulse cycle. The pulsed arc welding power supply is characterized by: a short-circuit occurrence period detection unit that detects the occurrence period of a short circuit between the welding wire and the base material in each pulse cycle; a cumulative correction amount calculation unit that calculates the cumulative correction amount by accumulating a predetermined correction amount corresponding to the short-circuit occurrence period in each given pulse cycle; and a pulse parameter correction unit that corrects the pulse parameters of the welding current waveform based on the cumulative correction amount.

[0012] The invention of technical solution 2 is based on the pulsed arc welding power source described in technical solution 1, and is characterized in that the occurrence period of the short circuit is classified into four periods: the rising period, the peak period, the falling period, and the base period.

[0013] The invention of technical solution 3 is based on the pulsed arc welding power source described in technical solution 1 or 2, characterized in that the pulse parameters are the peak period and / or the peak current.

[0014] The effects of the invention

[0015] According to the present invention, good transient response and steady-state stability can be achieved in the automatic correction control of pulse parameters. Especially in high-speed welding, the pulse parameters can be rapidly converged to an appropriate value, and the steady-state stability is also good, thus enabling high-quality welding with low sputtering output. Attached Figure Description

[0016] Figure 1 This is a block diagram of a pulsed arc welding power source according to an embodiment of the present invention.

[0017] Figure 2 yes Figure 1 Timing diagram of each signal in the welding power supply.

[0018] Explanation of reference numerals in the attached figures

[0019] 1 Welding wire

[0020] 1a Welding wire reel

[0021] 2. Base Material

[0022] 3. Electric arc

[0023] 4 Welding torch

[0024] 5 feed rollers

[0025] DV drive circuit

[0026] Dv drive signal

[0027] EI current error amplifier circuit

[0028] Ei Current Error Amplification Signal

[0029] EV voltage error amplifier circuit

[0030] Ev Voltage Error Amplification Signal

[0031] FC feed control circuit

[0032] Fc feed control signal

[0033] FR feed rate setting circuit

[0034] Fr feed rate setting signal

[0035] Ib base current

[0036] IBR base current setting circuit

[0037] Ibr base current setting signal

[0038] ICR current control setting circuit

[0039] Icr current control setting signal

[0040] ID Welding Current Detection Circuit

[0041] Id welding current detection signal

[0042] Ip peak current

[0043] Initial value of Ip0 peak current

[0044] Ipr peak current setting signal

[0045] IR welding current average setting circuit

[0046] Ir welding current average setting signal

[0047] Iw welding current

[0048] Kt and Ki coefficients

[0049] PC Pulse Parameter Correction Circuit

[0050] PM power control circuit

[0051] SA Short Circuit Detection Circuit

[0052] Sa Short-circuit discrimination signal

[0053] SD cumulative correction calculation circuit

[0054] Sd cumulative correction signal

[0055] Tb base period

[0056] During the Td decline

[0057] TDR descent period setting circuit

[0058] Tdr setting signal during descent

[0059] Tf pulse period (signal)

[0060] TM Timer Circuit

[0061] Tm timer signal

[0062] During Tp peak period

[0063] The initial value during the peak period of Tp0

[0064] Tpr peak period setting signal

[0065] TSA Short Circuit Detection Circuit

[0066] Tsa Short Circuit Detection Signal

[0067] Tu during its rising period

[0068] TUR rise period setting circuit

[0069] Tur sets signal during rise

[0070] The circuit calculates the average welding voltage using VAV.

[0071] Vav welding voltage average signal

[0072] VD welding voltage detection circuit

[0073] Vd welding voltage detection signal

[0074] VF Voltage-to-Frequency Conversion Circuit

[0075] VR welding voltage setting circuit

[0076] Vr welding voltage setting signal

[0077] Vw welding voltage

[0078] WM welding wire feed motor Detailed Implementation

[0079] The embodiments of the present invention will be described below with reference to the accompanying drawings.

[0080] Figure 1 This is a block diagram of a pulsed arc welding power source according to an embodiment of the present invention. The following description refers to this diagram.

[0081] The power control circuit PM takes a 3-phase 200V commercial power supply (not shown in the diagram) as input and performs inverter-based output control according to the drive signal Dv described later, outputting welding current Iw and welding voltage Vw. Although the diagram is omitted, the power control circuit PM includes: a primary rectifier that rectifies the commercial power supply; a capacitor that smooths the rectified DC; an inverter circuit that converts the smoothed DC into high-frequency AC according to the aforementioned drive signal Dv; a high-frequency transformer that steps down the high-frequency AC to a voltage suitable for arc welding; a secondary rectifier that rectifies the stepped-down high-frequency AC; and a reactor that smooths the rectified DC.

[0082] Welding wire 1 is wound on a wire spool 1a. Welding wire 1 is fed into the welding torch 4 by the rotation of the feed roller 5, which is connected to the wire feed motor WM, and an electric arc 3 is generated between the wire 1 and the base material 2 for welding. A welding current Iw is passed through the electric arc 3, and a welding voltage Vw is applied between the welding wire 1 and the base material 2.

[0083] The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage average value calculation circuit VAV takes the welding voltage detection signal Vd as input, averages it through a low-pass filter, and outputs a welding voltage average value signal Vav. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV amplifies the error between the welding voltage setting signal Vr and the above-mentioned welding voltage average value signal Vav, and outputs a voltage error amplification signal Ev.

[0084] The voltage / frequency conversion circuit VF takes the aforementioned voltage error amplification signal Ev as input and outputs a pulse periodic signal Tf with a frequency corresponding to the value of the voltage error amplification signal Ev. This pulse periodic signal Tf is a signal that becomes a short high-level signal for each pulse period.

[0085] The short-circuit detection circuit SA takes the welding voltage detection signal Vd mentioned above as input, determines the short-circuit state based on its value, and outputs a high-level short-circuit detection signal Sa.

[0086] The short circuit occurrence detection circuit TSA takes the short circuit discrimination signal Sa and the timer signal Tm (described later) as inputs, performs the following processing, and outputs the short circuit occurrence detection signal Tsa.

[0087] 1) When the short-circuit discrimination signal Sa changes to a high level when the timer signal Tm = 1 (during the rise of Tu), the short-circuit occurrence detection signal Tsa = 1 is output.

[0088] 2) When the short-circuit discrimination signal Sa changes to a high level when the timer signal Tm = 2 (peak period Tp), the short-circuit occurrence detection signal Tsa = 2 is output.

[0089] 3) When the short-circuit discrimination signal Sa changes to a high level when the timer signal Tm = 3 (during the falling period Td), the short-circuit occurrence detection signal Tsa = 3 is output.

[0090] 4) When the short-circuit discrimination signal Sa changes to a high level during the timer signal Tm = 4 (base value period Tb), the short-circuit occurrence detection signal Tsa = 4 is output.

[0091] The cumulative correction calculation circuit SD takes the short-circuit occurrence detection signal Tsa as input. In each pulse cycle, it outputs a predetermined correction amount Sd1 when Tsa = 1, a predetermined correction amount Sd2 when Tsa = 2, a predetermined correction amount Sd3 when Tsa = 3, and a predetermined correction amount Sd4 when Tsa = 4. It accumulates these correction amounts in each given pulse cycle and outputs the cumulative correction amount signal Sd. For detailed operation of this circuit, see [link to circuit description]. Figure 2 This will be discussed later.

[0092] The rise period setting circuit TUR outputs a predetermined rise period setting signal Ur. The fall period setting circuit TDR outputs a predetermined fall period setting signal Tdr.

[0093] The pulse parameter correction circuit PC takes the aforementioned cumulative correction signal Sd as input, calculates Tpr = Tp0 + ∑(Sd × Kt) for each given pulse period, and calculates Ipr = Ip0 + ∑(Sd × Ki), outputting the peak period setting signal Tpr and the peak current setting signal Ipr. Tp0 and Ip0 are predetermined initial values, and Kt and Ki are predetermined coefficients. Detailed operation of this circuit is described in... Figure 2 This will be discussed later.

[0094] The timer circuit TM takes the pulse period signal Tf, the rise period setting signal Tur, the peak period setting signal Tpr, and the fall period setting signal Tdr as inputs. If the pulse period signal Tf changes to a short-term high level, it outputs the following timer signal Tm: during the rise period Tu determined by the rise period setting signal Tur, the value of the timer signal Tm is 1; during the peak period Tp determined by the peak period setting signal Tpr, the value of the timer signal Tm is 2; during the fall period Td determined by the fall period setting signal Tdr, the value of the timer signal Tm is 3; and during the base period Tb until the pulse period signal Tf becomes a short-term high level, the value of the timer signal Tm is 4.

[0095] The base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

[0096] The current control setting circuit ICR takes the timer signal Tm, the peak current setting signal Ipr, and the base current setting signal Ibr as inputs, performs the following processing, and outputs the current control setting signal Icr.

[0097] 1) When the timer signal Tm = 1 (during the rise period Tu), the current control setting signal Icr is output, which rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr.

[0098] 2) When the timer signal Tm = 2 (peak period Tp), the output is the current control setting signal Icr, which becomes the value of the peak current setting signal Ipr.

[0099] 3) When the timer signal Tm = 3 (during the falling period Td), output the current control setting signal Icr, which decreases from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr.

[0100] 4) When the timer signal Tm = 4 (base value period Tb), the output is the current control setting signal Icr, which becomes the value of the base value current setting signal Ibr.

[0101] The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplifier circuit EI amplifies the error between the current control setting signal Icr and the welding current detection signal Id, and outputs a current error amplification signal Ei. The drive circuit DV uses this current error amplification signal Ei as input for PWM control and outputs a drive signal Dv to drive the inverter circuit of the power control circuit PM.

[0102] The welding current average setting circuit IR outputs a predetermined welding current average setting signal Ir. The feed speed setting circuit FR takes this welding current average setting signal Ir as input, calculates the feed speed setting signal Fr corresponding to the value of the welding current average setting signal Ir using a pre-built formula relating the welding current average and feed speed, and outputs it. The feed control circuit FC takes this feed speed setting signal Fr as input, and outputs a feed control signal Fc, used to feed the welding wire 1 at the feed speed determined by this value, to the aforementioned welding wire feed motor WM.

[0103] Figure 2 yes Figure 1 The following diagram shows the timing of various signals in the welding power supply. Diagram (A) represents the time variation of the welding current Iw, diagram (B) represents the time variation of the welding voltage Vw, and diagram (C) represents the time variation of the short-circuit detection signal Sa. The operation of each signal will be explained below with reference to this diagram.

[0104] During the rising period Tu from time t1 to t2, as shown in Figure (A), the welding current Iw rises from the base current Ib to the peak current Ip, and as shown in Figure (B), the welding voltage Vw rises from the base voltage to the peak voltage. During the peak period Tp from time t2 to t3, as shown in Figure (A), the welding current Iw becomes the peak current Ip, and as shown in Figure (B), the welding voltage Vw becomes the peak voltage. During the falling period Td from time t3 to t4, as shown in Figure (A), the welding current Iw decreases from the peak current Ip to the base current Ib, and as shown in Figure (B), the welding voltage Vw decreases from the peak voltage to the base voltage. During the base period Tb from time t4 to t5, as shown in Figure (A), the welding current Iw becomes the base current Ib, and as shown in Figure (B), the welding voltage Vw becomes the base voltage. The period from time t1 to t5 is defined as one pulse period Tf. The peak current Ip and the peak period Tp are set so that the droplet transitions within each pulse period Tf. The base current Ib is set to a small value to prevent droplet formation. The peak current Ip is... Figure 1 The peak current setting signal Ipr is used to set the base current Ib, and the base current is set by... Figure 1 The base current setting signal Ibr is used to set the value. During the rise period, Tu is... Figure 1 The rise period is set by the signal Tur, and the peak period is set by... Figure 1 The peak period is set by the signal Tpr, and the fall period is set by... Figure 1 The setting signal Tdr is used to set the descent period.

[0105] The pulse period Tf is modulated to make the average value of the welding voltage Vw ( Figure 1The welding voltage average signal Vav becomes similar to Figure 1 The welding voltage setting signal Vr is equal to the welding voltage setting signal. Therefore, the arc length is controlled to an appropriate value.

[0106] In this figure, at time t31 during the falling period Td, a short circuit occurs briefly between the welding wire and the base material, as shown in Figure (B), and the welding voltage Vw becomes a short-circuit voltage value of several V. Therefore, at time t31, as shown in Figure (C), the short-circuit detection signal Sa becomes a short-term high level. As shown in Figure (A), the welding current Iw rises during the short-circuit period. Therefore, Figure 1 The short-circuit occurrence detection circuit TSA outputs a short-circuit occurrence detection signal Tsa = 3. Upon receiving this output, Figure 1 The circuit SD is calculated based on the cumulative correction amount, and the circuit outputs a predetermined third correction amount Sd3 corresponding to the detection signal Tsa=3 during the short circuit occurrence period. The correction amount is accumulated for each given pulse period and the cumulative correction amount signal Sd is output.

[0107] Here, let's assume a given period of, for example, 5. In the nth pulse period, if a short circuit occurs during the rising period Tu, then Tsa = 1, and the correction becomes the first correction Sd1. In the (n+1)th pulse period, if a short circuit occurs during the peak period Tp, then Tsa = 2, and the correction becomes the second correction Sd2. In the (n+2)th pulse period, if a short circuit occurs during the falling period Td, then Tsa = 3, and the correction becomes the third correction Sd3. In the (n+3)th pulse period, if a short circuit occurs during the base period Tb, then Tsa = 4, and the correction becomes the fourth correction Sd4. In the (n+4)th pulse period, if a short circuit occurs during the peak period Tp, then Tsa = 2, and the correction becomes the second correction Sd2. The result is the cumulative correction signal Sd = Sd1 + Sd2 + Sd3 + Sd4 + Sd2. Here, for example, if we set Sd1 = 1, Sd2 = -1, Sd3 = -0.6, and Sd4 = 0, then it becomes Sd = -1.6.

[0108] Next, Figure 1 The pulse parameter correction circuit PC takes the aforementioned cumulative correction signal Sd as input and calculates Tpr = Tp0 + ∑(Sd × Kt) for each given pulse period, and then calculates Ipr = Ip0 + ∑(Sd × Ki). Here, if we set the coefficient Kt = 10μs and Ki = 5A, then Sd × Kt = -1.6 × 10 = -16μs, and Sd × Ki = -1.6 × 5 = -8A. Therefore, at the end of the (n+4)th pulse period, a correction is performed that shortens the peak period Tp by 16μs and reduces the peak current Ip by 8A.

[0109] The short-circuit occurrence period is classified into four periods: the rising period Tu, the peak period Tp, the falling period Td, and the base period Tb, because the welding conditions differ depending on the short-circuit occurrence period, as shown below. Appropriate pulse parameters can be achieved by adjusting the pulse parameters to converge the short-circuit occurrence period to the base period.

[0110] (1) The rise period Tu is the preparation period for the growth of molten droplets at the tip of the welding wire. A short circuit occurs during this period because the heat input required to form a 1-pulse-cycle 1-droplet transition state is insufficient, resulting in a multi-pulse-cycle 1-droplet transition state. In this case, it is necessary to increase the peak period Tp and / or the peak current Ip.

[0111] (2) The peak period Tp is the period during which the droplets grow larger. Short circuits occur during this period because the heat input for droplet transition is excessive, resulting in a multi-droplet transition state within a single pulse cycle. In this case, it is necessary to reduce the peak period Tp and / or the peak current Ip.

[0112] (3) The droplet formation and necking during the droplet formation period (Td) facilitates the transition. A short circuit occurs during this period because the heat input is slightly excessive. In this case, it is necessary to slightly reduce the peak period (Tp) and / or the peak current (Ip).

[0113] (4) The base period Tb is the transition period during which droplet growth stops. A short circuit occurs during this period because a stable 1-pulse-period, 1-droplet transition state is achieved. In this case, the peak period Tp and / or peak current Ip are appropriate values ​​and do not require correction. Alternatively, the pulse parameters can be optimized by classifying the base period into an early base period and a late base period, making the short circuit occurrence period the early base period. In this case, because the heat input is insufficient when the short circuit occurrence period becomes the late base period, the peak period Tp and / or peak current Ip increase.

[0114] The following are numerical examples of the pulse parameters mentioned above.

[0115] The initial value during the peak period is Tp0 = 1.5 ms, and the initial value of the peak current is Ip0 = 500 A.

[0116] Rise period Tu = 1ms, fall period Td = 1ms, base current Ib = 50A

[0117] Pulse period Tf (modulation amplitude) = 4~10ms, given pulse period = 3~10ms

[0118] In the above, upper and lower limits can be set for the correction of peak current Tp and peak current Ip. This helps to prevent the correction control from becoming unstable. Furthermore, in the case of multiple short circuits occurring within one pulse cycle, it is preferable to target the correction control at the initial short circuit occurrence time. This is because the initial short circuit occurrence time is important for determining the appropriateness of the heat input. Furthermore, the convergence value of the pulse parameters can be stored, and welding can begin from the convergence value in subsequent welding operations. This allows a stable one-pulse-cycle, one-droplet transition state to be formed from the very beginning of welding.

[0119] The pulsed arc welding power source according to the above-described embodiment includes: a short-circuit occurrence period detection unit that detects the occurrence period of a short circuit between the welding wire and the base material per pulse cycle; a cumulative correction amount calculation unit that calculates a cumulative correction amount by accumulating a predetermined correction amount corresponding to the short-circuit occurrence period for each given pulse cycle; and a pulse parameter correction unit that corrects the pulse parameters of the welding current waveform based on the cumulative correction amount. Furthermore, the short-circuit occurrence period is classified into four periods: a rise period, a peak period, a fall period, and a base period. Furthermore, the pulse parameters are the peak period and / or the peak current. In this embodiment, good transient response is achieved by setting a correction amount corresponding to the short-circuit occurrence period. Furthermore, good steady-state stability is achieved by accumulating the correction amount for each pulse cycle for each given pulse cycle. As a result, in this embodiment, good transient response and steady-state stability can be achieved in the automatic correction control of the pulse parameters.

Claims

1. A pulsed arc welding power source, feeding a welding wire, comprising an electrical control unit that outputs a transition current rising from a base current to a peak current during the rise period, outputs the peak current during the peak period, outputs a transition current falling from the peak current to the base current during the fall period, outputs the base current during the base period, and outputs a welding current with these outputs as one pulse cycle. The pulsed arc welding power source is characterized by having: A short circuit occurrence detection unit detects the occurrence of a short circuit between the welding wire and the base material during each pulse cycle. The cumulative correction calculation unit calculates the cumulative correction amount by accumulating a predetermined correction amount corresponding to the occurrence period of the short circuit over each given pulse cycle; and A pulse parameter correction unit that corrects the pulse parameters of the welding current waveform based on the cumulative correction amount.

2. The pulsed arc welding power source according to claim 1, characterized in that, The occurrence period of the short circuit is classified into four periods: the rising period, the peak period, the falling period, and the base period.

3. The pulsed arc welding power source according to claim 1 or 2, characterized in that, The pulse parameters are the peak period and / or the peak current.

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