Arc welding control method

Abstract

To maintain good welding quality even if a value of a welding voltage setting signal is changed in reciprocal feed arc welding.SOLUTION: An arc welding control method forwardly feeds a welding wire during an arc period, inversely feeds it during a short-circuit period, and controls a welding voltage Vw based on a welding voltage setting signal Vr. A welding current setting signal Ir is set; a reference value of the welding voltage setting signal Vr is set with the welding voltage setting signal Ir as input; a forward feed amplitude Wsr and an inverse feed amplitude Wrr of feeding are set with the welding current setting signal Ir as input. When the value of the welding voltage setting signal Vr is modified to increase compared with the reference value, the forward feed amplitude Wsr is modified to decrease and the inverse feed amplitude Wrr is modified to increase. When the value of the welding voltage setting signal Vr is modified to decrease compared with the reference value, the forward feed amplitude Wsr is modified to increase and the inverse feed amplitude Wrr is modified to decrease.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an arc welding control method for feeding a welding wire in the forward direction during an arc period and in the reverse direction during a short circuit period, and controlling a welding voltage based on a welding voltage setting signal. [Background technology]

[0002] In general consumable electrode arc welding, a welding wire, which is a consumable electrode, is fed at a constant speed and an arc is generated between the welding wire and the base metal to perform welding. In consumable electrode arc welding, the welding wire and the base metal are often in a welding state in which a short circuit period and an arc period are alternately repeated.

[0003] In order to further improve the welding quality, forward and reverse feed arc welding, in which the welding wire is fed alternately in a forward and reverse direction, is commonly used. In this forward and reverse feed arc welding, the cycle of repeated short circuits and arcs can be stabilized compared to the conventional technique with a constant feed speed, and therefore the welding quality can be improved by reducing the amount of spatter and improving the bead appearance.

[0004] In arc welding performed by feeding a welding wire, the welding voltage is constant-voltage controlled based on a welding voltage setting signal. When the value of the welding voltage setting signal changes, the arc width is controlled to be maintained at an appropriate value by constant voltage control. In the invention of Patent Document 1, in forward / reverse feed arc welding, the feeding amplitude is changed to improve the transient response of the arc length control when the value of the welding voltage setting signal changes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6125932 Summary of the Invention [Problem to be solved by the invention]

[0006] In forward / reverse feed arc welding, if the feed amplitude is changed in conjunction with a change in the value of the welding voltage setting signal, as in the conventional technology, the average feed speed will fluctuate, which may affect the welding quality.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an arc welding control method that is capable of maintaining good welding quality in forward / reverse feed arc welding even when the value of the welding voltage setting signal is changed. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the invention of claim 1 comprises: 1. A method for controlling arc welding, comprising forward feeding of a welding wire during an arc period and reverse feeding of a welding wire during a short circuit period, and controlling a welding voltage based on a welding voltage setting signal, A welding current setting signal is set, the welding current setting signal is used as an input to set a reference value for the welding voltage setting signal, and the welding current setting signal is used as an input to set the feeding Feed speed Set the forward and reverse amplitudes, When the value of the welding voltage setting signal is corrected to be greater than the reference value, the forward feed amplitude is corrected to be smaller and the reverse feed amplitude is corrected to be larger; When the value of the welding voltage setting signal is corrected to be smaller than the reference value, the forward feed amplitude is corrected to be larger and the reverse feed amplitude is corrected to be smaller. The present invention relates to an arc welding control method.

[0009] The invention of claim 2 is as follows: a voltage increase correction amount of the forward feed amplitude and a voltage increase correction amount of the reverse feed amplitude when the value of the welding voltage setting signal is corrected so as to be increased from the reference value are equal to each other, a voltage reduction correction amount of the forward feed amplitude and a voltage reduction correction amount of the reverse feed amplitude when the value of the welding voltage setting signal is corrected so as to be reduced below the reference value, the voltage reduction correction amount being equal to each other. 2. The method for controlling arc welding according to claim 1,

[0010] The invention of claim 3 is as follows: the voltage increase correction amount when the value of the welding voltage setting signal increases by 1 V from the reference value is smaller than the voltage decrease correction amount when the value of the welding voltage setting signal decreases by 1 V from the reference value. 3. The method for controlling arc welding according to claim 2. Effect of the Invention

[0011] According to the present invention, in forward / reverse feed arc welding, good welding quality can be maintained even when the value of the welding voltage setting signal is changed. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a welding device for carrying out an arc welding control method according to a first embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding device of FIG. 1, illustrating the arc welding control method according to the first embodiment of the present invention. [Diagram 3] FIG. 11 is a block diagram of a welding device for carrying out an arc welding control method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] [Embodiment 1] 1 is a block diagram of a welding device for carrying out an arc welding control method according to a first embodiment of the present invention. Each block will be described below with reference to the diagram.

[0015] The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V power supply, performs output control by inverter control or the like in accordance with an error amplified signal Ea described below, and outputs an output voltage E. Although not shown, this power supply main circuit PM includes a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified DC, an inverter circuit driven by the error amplified signal Ea described above that converts the smoothed DC into high-frequency AC, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency AC into DC.

[0016] The reactor WL smoothes the output voltage E. The inductance value of the reactor WL is, for example, 100 μH.

[0017] The feed motor WM receives a feed control signal Fc, which will be described later, and alternates between forward and reverse feed to feed the welding wire 1 at a feed speed Fw. A motor with fast transient response is used for the feed motor WM. In order to increase the rate of change of the feed speed Fw of the welding wire 1 and the reversal of the feed direction, the feed motor WM may be installed near the tip of the welding torch 4. Also, two feed motors WM may be used to form a push-pull type feed system.

[0018] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to the above-mentioned feed motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between a power feed tip (not shown) in the welding torch 4 and the base metal 2, and a welding current Iw flows through the wire 1. A shielding gas (not shown) is ejected from the tip of the welding torch 4.

[0019] The welding current setting circuit IR outputs a predetermined welding current setting signal Ir for setting the average value of the above-mentioned welding current Iw.

[0020] The welding voltage reference value setting circuit VSR receives the above-mentioned welding current setting signal Ir as an input and outputs a welding voltage reference value setting signal Vsr according to a predetermined voltage calculation function. The voltage setting function is a function for calculating the value of the welding voltage reference value setting signal Vsr that provides an appropriate arc length corresponding to the value of the welding current setting signal Ir, and is defined in advance by experiment.

[0021] The welding voltage fine adjustment circuit DVR outputs a predetermined welding voltage fine adjustment signal Dvr which has a positive or negative value for correcting the value of the above-mentioned welding voltage reference value signal Vsr.

[0022] The welding voltage setting circuit VR receives the above welding voltage reference value setting signal Vsr and the above welding voltage fine adjustment signal Dvr as inputs, adds the two values ​​to modify the value of the welding voltage reference value setting signal Vsr, and outputs the welding voltage setting signal Vr. It is assumed that when the welding current setting signal Ir=200A, the welding voltage reference value setting signal Vsr=21V. Also, when the welding voltage fine adjustment signal Dvr=-2V, the welding voltage setting signal Vr=21-2=19V.

[0023] The welding voltage detection circuit VD detects the above-mentioned welding voltage Vw and outputs a welding voltage detection signal Vd.

[0024] The voltage error amplifier circuit EV receives the welding voltage setting signal Vr and the welding voltage detection signal Vd, amplifies the error between the two signals, and outputs a voltage error amplified signal Ev.

[0025] A welding current detection circuit ID detects the above-mentioned welding current Iw and outputs a welding current detection signal Id.

[0026] The short circuit determination circuit SD receives the above-mentioned welding voltage detection signal Vd as input, and outputs a short circuit determination signal Sd that goes to a High level when this value is less than a predetermined short circuit determination value (approximately 10 V) and determines that the circuit is in a short circuit period, and goes to a Low level when this value is equal to or greater than this value and determines that the circuit is in an arc period.

[0027] The forward transfer acceleration period setting circuit TSUR outputs a predetermined forward transfer acceleration period setting signal Tsur.

[0028] The normal transmission deceleration period setting circuit TSDR outputs a predetermined normal transmission deceleration period setting signal Tsdr.

[0029] The reverse transport acceleration period setting circuit TRUR outputs a predetermined reverse transport acceleration period setting signal Trur.

[0030] The reverse transport deceleration period setting circuit TRDR outputs a predetermined reverse transport deceleration period setting signal Trdr.

[0031] The positive feed amplitude reference value setting circuit WSSR receives the welding current setting signal Ir and outputs a positive feed amplitude reference value setting signal Wssr according to a predetermined positive feed amplitude calculation function. The positive feed amplitude calculation function is a function for calculating a value of the positive feed amplitude reference value setting signal Wssr that provides a good welding condition corresponding to the value of the welding current setting signal Ir, and is defined in advance by experiment.

[0032] The reverse feed amplitude reference value setting circuit WRSR receives the welding current setting signal Ir and outputs a reverse feed amplitude reference value setting signal Wrsr according to a predetermined reverse feed amplitude calculation function. The reverse feed amplitude calculation function is a function for calculating a value of the reverse feed amplitude reference value setting signal Wrsr that provides a good welding state corresponding to the value of the welding current setting signal Ir, and is defined in advance by experiment.

[0033] The positive feed amplitude setting circuit WSR receives the positive feed amplitude reference value setting signal Wssr and the welding voltage fine adjustment signal Dvr as inputs, performs the following processing, and outputs the positive feed amplitude setting signal Wsr. 1) When Dvr ≥ 0, calculate and output Wsr = Wssr + Ks1 · Dvr. Here, Ks1 is a negative constant, which is the amount of decrease in the positive transmission amplitude when the value of Dvr increases by +1V. (Ks1 · Dvr) is the amount of voltage increase correction. 2) When Dvr<0, calculate and output Wsr=Wssr+Ks2·Dvr. Here, Ks2 is a negative constant, which is the increase in the positive amplitude when the value of Dvr decreases by -1V. (Ks2·Dvr) is the voltage decrease correction amount.

[0034] The reverse feed amplitude setting circuit WRR receives the reverse feed amplitude reference value setting signal Wrsr and the welding voltage fine adjustment signal Dvr, performs the following processing, and outputs the reverse feed amplitude setting signal Wrr. Although the reverse feed speed is a negative value, in the following description, the reverse feed amplitude is described as an absolute value. 1) When Dvr ≥ 0, calculate and output Wrr = Wrsr + Ks3 · Dvr. Here, Ks3 is a positive constant, and is the increase in reverse amplitude when the value of Dvr increases by +1V. (Ks3 · Dvr) is the voltage increase correction amount. 2) When Dvr<0, calculate and output Wrr=Wrsr+Ks4·Dvr. Here, Ks4 is a positive constant, which is the amount of decrease in the reverse amplitude when the value of Dvr decreases by -1V. (Ks4·Dvr) is the voltage decrease correction amount.

[0035] Hereinafter, a method for calculating the forward transmission amplitude setting signal Wsr and the reverse transmission amplitude setting signal Wrr will be described with reference to numerical examples. When the welding current setting signal Ir is 200 A, the welding voltage reference value setting signal Vsr is 21 V, the forward feed amplitude reference value setting signal Wssr is 50 m / min, and the reverse feed amplitude reference value setting signal Wrsr is 40 m / min. The constants Ks1 to Ks2 are the correction amounts of the feed speed m / min when the value of the welding voltage fine adjustment signal Dvr changes by 1 V. Let Ks1=-7, Ks2=-5, Ks3=6, and Ks4=4. (1) When the welding voltage fine adjustment signal Dvr is increased by +1 V, the values ​​of the forward feed amplitude setting signal Wsr and the reverse feed amplitude setting signal Wrr are as follows. Wsr = Wssr + Ks1 · Dvr = 50 + (-7) · (+1) = 43 m / min, and the voltage increase correction amount is -7 m / min. Wrr = Wrsr + Ks3 · Dvr = 40 + (+5) · (+1) = 45 m / min, and the voltage increase correction amount is +5 m / min. (2) When the welding voltage fine adjustment signal Dvr is decreased by −1 V, the values ​​of the forward feed amplitude setting signal Wsr and the reverse feed amplitude setting signal Wrr are as follows. Wsr = Wssr + Ks2 · Dvr = 50 + (-6) · (-1) = 56 m / min, and the voltage reduction correction amount is +6 m / min. Wrr = Wrsr + Ks4 · Dvr = 40 + (+4) · (-1) = 36 m / min, and the voltage decrease correction amount is -4 m / min.

[0036] The feed speed setting circuit FR receives the forward feed acceleration period setting signal Tsur, the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the reverse feed deceleration period setting signal Trdr, the forward feed amplitude setting signal Wsr, the reverse feed amplitude setting signal Wrr, and the short circuit determination signal Sd as inputs, and outputs a feed speed pattern generated by the following process as a feed speed setting signal Fr. When this feed speed setting signal Fr is 0 or more, it is a forward feed period, and when it is less than 0, it is a reverse feed period. 1) During the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, the feed speed setting signal Fr for accelerating from 0 to the forward feed amplitude Wsp determined by the forward feed amplitude setting signal Wsr is output. 2) Subsequently, during the forward feed peak period Tsp, the feed speed setting signal Fr for maintaining the forward feed amplitude Wsp is output. 3) When the short circuit discrimination signal Sd changes from a low level (arc period) to a high level (short circuit period), the process transitions to a forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and the feed speed setting signal Fr is output, which decelerates from the forward feed amplitude Wsp to 0. 4) Subsequently, during the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur, a feed speed setting signal Fr is output which accelerates from 0 to the reverse amplitude Wrp determined by the reverse amplitude setting signal Wrr. 5) Subsequently, during the reverse feed peak period Trp, the feed speed setting signal Fr for maintaining the above reverse feed amplitude Wrp is output. 6) When the short circuit detection signal Sd changes from a high level (short circuit period) to a low level (arc period), the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr begins, and the feed speed setting signal Fr is output to decelerate the reverse feed amplitude Wrp to 0. 7) By repeating the above steps 1) to 6), a feed speed setting signal Fr is generated having a feed pattern that changes like a positive and negative trapezoidal wave.

[0037] The feed control circuit FC receives the feed speed setting signal Fr as an input and outputs a feed control signal Fc to the feed motor WM for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr.

[0038] The current-limiting resistor R is inserted between the reactor WL and the welding torch 4. The value of this current-limiting resistor R is set to a value (about 0.5 to 3 Ω) that is 50 times or more larger than the short-circuit load (about 0.01 to 0.03 Ω). When this current-limiting resistor R is inserted into the current path, the energy stored in the reactor WL and the reactor of the external cable is suddenly discharged.

[0039] The transistor TR is connected in parallel with the current reducing resistor R, and is controlled to be turned on or off in accordance with a drive signal Dr, which will be described later.

[0040] The constriction detection circuit ND takes the above short - circuit discrimination signal Sd, the above welding voltage detection signal Vd, and the above welding current detection signal Id as inputs. When the short - circuit discrimination signal Sd is at the High level (short - circuit period), when the voltage rise value of the welding voltage detection signal Vd reaches the reference value, it determines that the constriction formation state has reached the reference state and becomes High level, and outputs a constriction detection signal Nd that becomes Low level when the short - circuit discrimination signal Sd changes to the Low level (arc period). Also, the constriction detection signal Nd may be changed to High level when the differential value of the welding voltage detection signal Vd during the short - circuit period reaches the corresponding reference value. Further, the value of the welding voltage detection signal Vd is divided by the value of the welding current detection signal Id to calculate the resistance value of the droplet, and the constriction detection signal Nd may be changed to High level when the differential value of this resistance value reaches the corresponding reference value.

[0041] The low - level current setting circuit ILR outputs a predetermined low - level current setting signal Ilr. The current comparison circuit CM takes this low - level current setting signal Ilr and the above welding current detection signal Id as inputs, and outputs a current comparison signal Cm that becomes High level when Id < Ilr and becomes Low level when Id ≧ Ilr.

[0042] The drive circuit DR takes the above current comparison signal Cm and the above constriction detection signal Nd as inputs, and outputs a drive signal Dr to the base terminal of the above transistor TR, which changes to Low level when the constriction detection signal Nd changes to High level, and then changes to High level when the current comparison signal Cm changes to High level. Therefore, when constriction is detected, this drive signal Dr becomes Low level, the transistor TR turns off, and the current - reducing resistor R is inserted into the energization path, so the welding current Iw passing through the short - circuit load rapidly decreases. Then, when the value of the rapidly decreased welding current Iw decreases to the value of the low - level current setting signal Ilr, the drive signal Dr becomes High level, the transistor TR turns on, and the current - reducing resistor R is short - circuited and returns to the normal state.

[0043] The first arc period setting circuit TA1R outputs a predetermined first arc period setting signal Ta1r.

[0044] The first arc period circuit STA1 receives as input the above-mentioned short circuit determination signal Sd and the above-mentioned first arc period setting signal Ta1r, and outputs a first arc period signal Sta1 that becomes high level during the first arc period Ta1 predetermined by the first arc period setting signal Ta1r from the point when the short circuit determination signal Sd changes to low level (arc period) and a predetermined delay period Tc has elapsed.

[0045] The first arc current setting circuit IA1R outputs a predetermined first arc current setting signal Ia1r.

[0046] The third arc period circuit STA3 receives the above-mentioned short circuit determination signal Sd as an input, and outputs a third arc period signal Sta3 which goes to a high level when a predetermined current drop time Td has elapsed since the short circuit determination signal Sd changed to a low level (arc period), and then goes to a low level when the short circuit determination signal Sd subsequently goes to a high level (short circuit period).

[0047] The third arc current setting circuit IA3R outputs a predetermined third arc current setting signal Ia3r.

[0048] The current control setting circuit ICR receives as inputs the short circuit determination signal Sd, the low level current setting signal Ilr, the constriction detection signal Nd, the first arc period signal Sta1, the third arc period signal Sta3, the first arc current setting signal Ia1r, and the third arc current setting signal Ia3r, performs the following processing, and outputs a current control setting signal Icr. 1) During the delay period from when the short circuit detection signal Sd changes to a low level (arc period) to when the first arc period signal Sta1 changes to a high level, a current control setting signal Icr having the value of the low-level current setting signal Ilr is output. 2) Thereafter, when first arc period signal Sta1 is at a high level (first arc period), current control setting signal Icr which becomes first arc current setting signal Ia1r is output. 3) During the period from when the first arc period signal Sta1 changes to low level to when the third arc period signal Sta3 changes to low level (the second arc period and third arc period), a current control setting signal Icr which becomes the third arc current setting signal Ia3r is output. 4) When the short circuit determination signal Sd changes to a high level (short circuit period), a predetermined initial current setting value is set during a predetermined initial period, and thereafter a current control setting signal Icr is output which rises with a predetermined short circuit slope to a predetermined short circuit peak setting value and maintains that value. 5) After that, when the squeezing detection signal Nd changes to a high level, the current control setting signal Icr having the value of the low-level current setting signal Ilr is output.

[0049] The current error amplifier circuit EI receives the current control setting signal Icr and the current detection signal Id as inputs, amplifies the error between the current control setting signal Icr(+) and the current detection signal Id(-), and outputs a current error amplified signal Ei.

[0050] The power supply characteristics switching circuit SW receives the current error amplified signal Ei, the voltage error amplified signal Ev, the first arc period signal Sta1, and the third arc period signal Sta3 as inputs, performs the following processing, and outputs an error amplified signal Ea. 1) During second arc period Ta2 from when first arc period signal Sta1 changes to low level until third arc period signal Sta3 changes to high level, voltage error amplified signal Ev is output as error amplified signal Ea. 2) During the other periods, the current error amplified signal Ei is output as the error amplified signal Ea. This circuit causes the welding power supply to have constant current characteristics during the short circuit period, delay period, first arc period Ta1 and third arc period Ta3, and constant voltage characteristics during second arc period Ta2.

[0051] Fig. 2 is a timing chart of each signal in the welding device of Fig. 1, which illustrates the arc welding control method according to the first embodiment of the present invention. Fig. 2(A) shows the change over time of the feed speed Fw, Fig. 2(B) shows the change over time of the welding current Iw, Fig. 2(C) shows the change over time of the welding voltage Vw, Fig. 2(D) shows the change over time of the short circuit determination signal Sd, Fig. 2(E) shows the change over time of the first arc period signal Sta1, and Fig. 2(F) shows the change over time of the third arc period signal Sta3. The operation of each signal will be explained below with reference to the figure.

[0052] The feed speed Fw shown in FIG. 1(A) is controlled by the value of the feed speed setting signal Fr output from the feed speed setting circuit FR in FIG. 1. The feed speed Fw is formed by the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur in FIG. 1, the forward feed peak period Tsp that continues until a short circuit occurs, the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr in FIG. 1, the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur in FIG. 1, the reverse feed peak period Trp that continues until an arc occurs, and the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr in FIG. 1. Furthermore, the forward feed amplitude Wsp is determined by the forward feed amplitude setting signal Wsr in FIG. 1, and the reverse feed amplitude Wrp is determined by the reverse feed amplitude setting signal Wrr in FIG. 1. As a result, the feed speed Fw has a positive value during the forward feed period and a negative value during the reverse feed period, resulting in a feed pattern that changes in a substantially positive and negative trapezoidal wave shape.

[0053] [Operation during the short circuit period from time t1 to t4] When a short circuit occurs at time t1 during the forward feed peak period Tsp, as shown in Fig. 1C, the welding voltage Vw suddenly drops to a short circuit voltage value of several volts, and the short circuit determination signal Sd changes to a high level (short circuit period) as shown in Fig. 1D. In response to this, a transition occurs to a predetermined forward feed deceleration period Tsd from time t1 to t2, and the feed speed Fw decelerates from the forward feed amplitude Wsp to 0 as shown in Fig. 1A. For example, the forward feed deceleration period Tsd is set to 1 ms.

[0054] As shown in FIG. 1A, the feed speed Fw enters a predetermined reverse acceleration period Tru from time t2 to t3, and accelerates from 0 to the reverse amplitude Wrp. During this period, the short circuit period continues. For example, the reverse acceleration period Tru is set to 1 ms.

[0055] When the reverse acceleration period Tru ends at time t3, as shown in FIG. 1A, the feed speed Fw enters the reverse peak period Trp and becomes the reverse amplitude Wrp. The reverse peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is a short circuit period. The reverse peak period Trp is not a predetermined value, but is about 3 ms. For example, the reverse amplitude Wrp is set to 40 m / min.

[0056] As shown in Fig. 1B, the welding current Iw during the short circuit period from time t1 to t4 is a predetermined initial current value during a predetermined initial period, after which the welding current Iw increases at a predetermined short circuit slope and, when it reaches a predetermined short circuit peak value, maintains that value.

[0057] As shown in Fig. 1C, the welding voltage Vw increases from the point where the welding current Iw reaches its peak value during short circuit. This is because a constriction gradually forms in the droplet at the tip of the welding wire 1 due to the reverse feed of the welding wire 1 and the pinching force caused by the welding current Iw.

[0058] Thereafter, when the voltage rise value of the welding voltage Vw reaches the reference value, it is determined that the state of the necking has reached the reference state, and the necking detection signal Nd in FIG. 1 changes to a high level.

[0059] In response to the squeezing detection signal Nd becoming high level, the drive signal Dr in FIG. 1 becomes low level, so that the transistor TR in FIG. 1 becomes off and the current reducing resistor R in FIG. 1 is inserted into the current path. At the same time, the current control setting signal Icr in FIG. 1 becomes small to the value of the low level current setting signal Ilr. For this reason, as shown in FIG. 1(B), the welding current Iw suddenly decreases from the peak value at the time of short circuit to the low level current value. Then, when the welding current Iw decreases to the low level current value, the drive signal Dr returns to the high level, so that the transistor TR becomes on and the current reducing resistor R is short-circuited. As shown in FIG. 1(B), the welding current Iw maintains the low level current value until the predetermined delay period Tc has elapsed since the arc re-strike, because the current control setting signal Icr remains the low level current setting signal Ilr. Therefore, the transistor TR is off only during the period from when the squeezing detection signal Nd changes to the high level to when the welding current Iw decreases to the low level current value. As shown in Fig. 1C, the welding voltage Vw decreases once and then rises sharply as the welding current Iw decreases. The above-mentioned parameters are set to the following values, for example: initial current = 40 A, initial period = 0.5 ms, short circuit slope = 180 A / ms, short circuit peak value = 400 A, low level current value = 50 A, delay period Tc = 0.5 ms.

[0060] [Arc period from time t4 to t7] At time t4, when the constriction progresses due to the pinch force caused by the reverse feed of the welding wire and the flow of the welding current Iw and an arc is generated, as shown in Fig. 1C, the welding voltage Vw suddenly increases to an arc voltage value of several tens of volts, and the short circuit determination signal Sd changes to a low level (arc period) as shown in Fig. 1D. In response to this, the process moves to a predetermined reverse feed deceleration period Trd from time t4 to t5, and the feed speed Fw decelerates from the reverse feed amplitude Wrp to 0 as shown in Fig. 1A. For example, the reverse feed deceleration period Trd is set to 1 ms.

[0061] When the reverse feed deceleration period Trd ends at time t5, it transitions to a predetermined forward feed acceleration period Tsu from time t5 to t6. During this forward feed acceleration period Tsu, as shown in FIG. 1A, the feed speed Fw accelerates from 0 to the forward feed amplitude Wsp. During this period, the arc period continues. For example, the forward feed acceleration period Tsu is set to 1 ms.

[0062] When the forward acceleration period Tsu ends at time t6, as shown in FIG. 1A, the feed speed Fw enters the forward peak period Tsp and becomes the forward amplitude Wsp. The arc period continues during this period. The forward peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. When a short circuit occurs, the operation returns to that at time t1. The forward peak period Tsp is not a predetermined value, but is about 5 ms. For example, the forward amplitude Wsp is set to 50 m / min.

[0063] When an arc is generated at time t4, as shown in FIG. 1C, the welding voltage Vw increases rapidly to an arc voltage value of several tens of volts. On the other hand, as shown in FIG. 1B, the welding current Iw continues to have a low current value from time t4 to the delay period Tc. This is because if the current value is increased immediately after the arc is generated, the reverse feed of the welding wire and the melting of the welding wire by the welding current are added together, causing the arc length to increase rapidly and resulting in an unstable welding state.

[0064] At time t51 during the forward feed acceleration period Tsu, when the delay period Tc ends, as shown in FIG. 1(E), the first arc period signal Sta1 changes to a high level, and a predetermined first arc period Ta1 from time t51 to t61 is entered. During this first arc period Ta1, constant current control continues, and as shown in FIG. 1(B), a predetermined first arc current Ia1 determined by the first arc current setting signal Ia1r in FIG. 1 flows. As shown in FIG. 1(C), the welding voltage Vw becomes a large value determined by the current value and the arc load. For example, the first arc period Ta1 is set to 0.5 ms, and the first arc current Ia1 is set to 400 A.

[0065] At time t62, when a predetermined current drop time Td has elapsed from the arc generation time point t4, as shown in FIG. 1(F), the third arc period signal Sta3 changes to a high level. The period from time t61 to t62 is the second arc period Ta2. During this second arc period Ta2, the welding voltage Vw is controlled to be constant voltage so that the value of the welding voltage setting signal Vr in FIG. 1 is equal to the value of the welding voltage detection signal Vd in FIG. 1. The welding voltage setting signal Vr is calculated by calculating the welding voltage reference value setting signal Vsr by a predetermined voltage calculation function using the welding current setting signal Ir in FIG. 1 as an input, and adding the welding voltage fine adjustment signal Dvr in FIG. 1 to this value. That is, Vr=Vsr+Dvr. As shown in FIG. 1(B), the second arc current Ia2 changes depending on the arc load, but is smaller than the first arc current Ia1 and is larger than the third arc current Ia3. That is, the output is controlled so that Ia1>Ia2>Ia3. As shown in Fig. 1C, the welding voltage Vw is controlled to a predetermined value by constant voltage control, and becomes an intermediate value between the voltage value of the first arc period Ta1 and the voltage value of the third arc period Ta3. The second arc period Ta2 is not a predetermined value, but is about 6 ms.

[0066] The period from time t62 when the third arc period signal Sta3 changes to a high level to time t7 when a short circuit occurs is the third arc period Ta3. Constant current control is performed during this third arc period Ta3. As shown in FIG. 1B, a predetermined third arc current Ia3 determined by the third arc current setting signal Ia3r in FIG. 1 is passed. As shown in FIG. 1C, the welding voltage Vw is a value determined by the current value and the arc load. For example, the third arc current Ia3 is set to 60 A. The third arc period Ta3 is not a predetermined value, but is about 0.5 ms.

[0067] The effects of the above-mentioned first embodiment will be described below. 1) Set the welding current setting signal Ir. 2) The value of the welding voltage reference value setting signal Vsr is calculated using a predetermined voltage calculation function with the value of the welding current setting signal Ir as an input. 3) The value of the positive feed amplitude reference value setting signal Wssr is calculated by a predetermined positive feed amplitude calculation function using the value of the welding current setting signal Ir as an input. 4) The value of the reverse feed amplitude reference value setting signal Wrsr is calculated by a predetermined reverse feed amplitude calculation function using the value of the welding current setting signal Ir as an input. 5) When the value of the welding voltage setting signal Vr is corrected to be greater than the value of the welding voltage reference value setting signal Vsr by setting the value of the welding voltage fine adjustment signal Dvr to a positive value, the value of the forward feed amplitude setting signal Wsr is corrected to be smaller than the value of the forward feed amplitude reference value setting signal Wssr, and the value of the reverse feed amplitude setting signal Wrs is corrected to be greater than the value of the reverse feed amplitude reference value signal Wrsr. In this way, when the value of the welding voltage setting signal Vr is corrected so as to be greater than the reference value, the welding state changes so that the time ratio of the short circuit period to the repetition period of the short circuit and arc (short circuit time rate) becomes smaller. As a result, if the forward feed amplitude and the reverse feed amplitude are constant, the average feed speed increases, and the welding quality such as the bead shape varies. To address this, by decreasing the forward feed amplitude and increasing the reverse feed amplitude as in this embodiment, the change in the average feed speed can be suppressed, and therefore the variation in the welding quality can be suppressed. 6) When the value of the welding voltage setting signal Vr is corrected to be less than the value of the welding voltage reference value setting signal Vsr by setting the value of the welding voltage fine adjustment signal Dvr to a negative value, the value of the forward feed amplitude setting signal Wsr is corrected to be greater than the value of the forward feed amplitude reference value setting signal Wssr, and the value of the reverse feed amplitude setting signal Wrs is corrected to be less than the value of the reverse feed amplitude reference value signal Wrsr. In this way, when the value of the welding voltage setting signal Vr is corrected to be less than the reference value, the welding state changes so that the short circuit time rate increases. As a result, if the forward feed amplitude and the reverse feed amplitude are constant, the average feed speed decreases, and the welding quality, such as the bead shape, fluctuates. To address this, if the forward feed amplitude is increased and the reverse feed amplitude is decreased as in this embodiment, the change in the average feed speed can be suppressed, and therefore the fluctuation in the welding quality can be suppressed.

[0068] More preferably, according to the first embodiment, the voltage increase correction amount of the forward feed amplitude and the voltage increase correction amount of the reverse feed amplitude are equal when the value of the welding voltage setting signal Vr is corrected to be greater than the reference value, and the voltage decrease correction amount of the forward feed amplitude and the voltage decrease correction amount of the reverse feed amplitude are equal when the value of the welding voltage setting signal Vr is corrected to be less than the reference value. In this way, even if the value of the welding voltage setting signal Vr changes and the short circuit time rate changes, the fluctuation of the average feed speed can be further suppressed, and good welding quality can be maintained.

[0069] More preferably, according to the first embodiment, the voltage increase correction amount when the value of welding voltage setting signal Vr increases by 1 V from the reference value is smaller than the voltage decrease correction amount when the value of welding voltage setting signal Vr decreases by 1 V from the reference value. When the value of welding voltage setting signal Vr is increased by 1 V compared to when it is decreased by 1 V, the change in the short circuit time rate is smaller when it is increased. By taking this into consideration and doing as described above, even if the value of welding voltage setting signal Vr increases or decreases and the short circuit time rate changes, the fluctuation in the average feed speed can be further suppressed, and good welding quality can be maintained.

[0070] [Embodiment 2] Fig. 3 is a block diagram of a welding device for carrying out an arc welding control method according to a second embodiment of the present invention. In the figure, the same blocks as those in Fig. 1 described above are given the same reference numerals, and their description will not be repeated. In the figure, a feed speed average value setting circuit FAR, a feed speed average value calculation circuit FAD, and a feed speed error amplifier circuit EF are added to Fig. 1. These blocks will be described below with reference to the figure.

[0071] The feed speed average value setting circuit FAR receives the welding current setting signal Ir and outputs a feed speed average value setting signal Far according to a predetermined feed speed calculation function. The feed speed setting function is a function that calculates the value of the feed speed average value setting signal Far corresponding to the value of the welding current setting signal Ir, and is defined in advance by experiment.

[0072] The feed speed average calculation circuit FAD receives the feed speed detection signal Fd from the encoder of the feed motor WM, the armature voltage, etc., calculates the average value, and outputs a feed speed average calculation signal Fad.

[0073] The feed speed error amplifier circuit EF receives the feed speed average value setting signal Far and the feed speed average value calculation circuit Fad, and outputs the error amplification value Ef=G (Far-Fad) of both values, where G is a predetermined positive amplification factor.

[0074] The feed amplitude control setting circuit WCR receives the feed speed error amplified signal Ef, the forward feed amplitude setting signal Wsr, and the reverse feed amplitude setting signal Wrr as inputs, calculates and outputs a forward feed amplitude control setting signal Wscr=Wsr+∫Ef·dt, and calculates and outputs a reverse feed amplitude control setting signal Wrcr=Wrr-∫Ef·dt.

[0075] In the figure, the feed speed setting circuit FR replaces the forward feed amplitude setting signal Wsr, which is an input signal, with the forward feed amplitude control setting signal Wscr described above, and replaces the reverse feed amplitude setting signal Wrr, which is an input signal, with the reverse feed amplitude control setting signal Wrcr described above. The processing content is the same as in FIG. 1, so the description will not be repeated.

[0076] The effects of the second embodiment described above will be described below. In the second embodiment, by adding the above circuit, the forward feed amplitude control setting signal Wscr and the reverse feed amplitude control setting signal Wrcr are changed by feedback control so that the feed speed average calculation signal Fad becomes equal to the feed speed average setting signal Far, which is the target value, even if the value of the welding voltage setting signal Vr changes and the short circuit time rate changes. In this feedback control, the forward feed amplitude setting signal Wsr and the reverse feed amplitude setting signal Wrr, which are initial values, are changed by the action of the first embodiment so that the feed speed average value becomes a substantially constant value, even if the value of the welding voltage setting signal Vr changes and the short circuit time rate changes. Therefore, the convergence value of the feedback control and the initial value become close to each other, so that the transition period until the steady state is converged to is shortened. As a result, the fluctuation of the welding quality can be further suppressed.

[0077] In the second embodiment, a push-pull feeding system may be formed by using two feeding motors WM, a push feeding motor controlled at a constant speed and a pull feeding motor controlled for forward and reverse feeding. A wire buffer for temporarily storing the welding wire may be provided between the two feeding motors. In this configuration, the average feeding speed can be made constant by feedback controlling the forward feed amplitude and reverse feed amplitude of the pull feeding motor so that the amount of wire stored in the wire buffer becomes a reference amount. Even in this configuration, the effect of the second embodiment described above can be achieved. [Explanation of symbols]

[0078] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll CM current comparison circuit Cm current comparison signal DR drive circuit Dr Drive signal DVR welding voltage fine adjustment circuit DVR welding voltage fine adjustment signal E Output voltage Ea Error amplification signal EF Feed speed error amplifier circuit Ef Feed speed error amplification signal EI Current Error Amplifier Circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev Voltage error amplified signal FAD Feed speed average calculation circuit Fad Feed speed average calculation signal FAR Feed speed average setting circuit Far Feed Speed ​​Average Setting Circuit FC feed control circuit Fc feed control signal Fd Feed speed detection signal FR feed speed setting circuit Fr feed speed setting signal Fw Feed speed G Amplification factor Ia1 First arc current IA1R First arc current setting circuit Ia1r 1st arc current setting signal Ia2 Second arc current Ia3 3rd arc current IA3R 3rd arc current setting circuit Ia3r 3rd arc current setting signal ICR Current control setting circuit Icr Current control setting signal ID Welding current detection circuit Id Welding current detection signal ILR Low level current setting circuit Ilr Low level current setting signal IR welding current setting circuit Ir Welding current setting signal Iw Welding current ND Constriction Detection Circuit Nd Constriction detection signal PM power supply main circuit R Current reducing resistor SD Short circuit detection circuit Sd Short circuit detection signal STA1 First arc period circuit Sta1 First arc period signal STA3 3rd arc period circuit Sta3 3rd arc period signal SW Power supply characteristic switching circuit TA1R First arc period setting circuit Ta1r 1st arc period setting signal Tc delay period Td Current fall time TR Transistor Trd Reverse feed deceleration period TRDR Reverse deceleration period setting circuit Trdr Reverse feed deceleration period setting signal Trp Backward Peak Period Tru Reverse acceleration period TRUR Reverse acceleration period setting circuit Trur Reverse acceleration period setting signal Tsd Forward feed deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp Peak forwarding period Tsu forward acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal VD Welding voltage detection circuit Vd Welding voltage detection signal VR welding voltage setting circuit Vr Welding voltage setting signal VSR Welding voltage reference value setting circuit Vsr Welding voltage reference value setting signal Vw welding voltage WCR feed amplitude control setting circuit WL Reactor WM Feed motor Wrcr Backward amplitude control setting signal Wrp Reverse feed amplitude WRR Backward Amplitude Setting Circuit Wrr Reverse amplitude setting signal WRSR Reverse amplitude reference value setting circuit Wrsr Reverse amplitude reference value setting signal Wscr Positive transmission amplitude control setting signal Wsp Forward feed amplitude WSR forward feed amplitude setting circuit Wsr Forward feed amplitude setting signal WSSR Positive transmission amplitude reference value setting circuit Wssr Positive transmission amplitude reference value setting signal

Claims

1. 1. A method for controlling arc welding, comprising forward feeding of a welding wire during an arc period and reverse feeding of a welding wire during a short circuit period, and controlling a welding voltage based on a welding voltage setting signal, a welding current setting signal is set, a reference value of the welding voltage setting signal is set by using the welding current setting signal as an input, and a forward feed amplitude and a reverse feed amplitude of the feed speed of the feed are set by using the welding current setting signal as an input; When the value of the welding voltage setting signal is corrected to be greater than the reference value, the forward feed amplitude is corrected to be smaller and the reverse feed amplitude is corrected to be larger; When the value of the welding voltage setting signal is corrected to be smaller than the reference value, the forward feed amplitude is corrected to be larger and the reverse feed amplitude is corrected to be smaller.

2. An arc welding control method comprising:

2. a voltage increase correction amount of the forward feed amplitude and a voltage increase correction amount of the reverse feed amplitude when the value of the welding voltage setting signal is corrected so as to be increased from the reference value are equal to each other, a voltage decrease correction amount of the forward feed amplitude and a voltage decrease correction amount of the reverse feed amplitude when the value of the welding voltage setting signal is corrected so as to be decreased below the reference value, the voltage decrease correction amount being equal to each other.

2. The method of claim 1, wherein the arc welding is controlled by the control circuit.

3. the voltage increase correction amount when the value of the welding voltage setting signal is increased by 1 V from the reference value is smaller than the voltage decrease correction amount when the value of the welding voltage setting signal is decreased by 1 V from the reference value.

3. The method of claim 2, wherein the arc welding control is performed in a controlled manner.

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