Arc welding control method

Abstract

To obtain a favorable weld quality by maintaining the average value of a pull side feeding speed at a prescribed value even when a feeding resistance fluctuates steeply and considerably in a forward / reverse-feeding arc welding method.SOLUTION: An arc welding control method comprises: feeding a welding wire 1 by a push-pull feeding control by a forward-rotating push side feeding motor WMP and a pull side feeding motor WM repeating the forward and reverse rotations; setting an intermediate wire storage part WB temporarily storing the welding wire 1 between the feeding routes of the push side and pull side feeding motors WMP and WM; and welding by repeating the short circuit period and arc period. In the method, the push side feeding speed Fwp of the push side feeding motor WMP is corrected based on the storage amount Wb of the intermediate wire storage part WB, and the waveform parameter of a pull side feeding speed Fw is corrected so that the average feeding speed Fad of the pull side feeding motor WM equals to a previously-set pull side average feeding speed set value Far.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an arc welding control method for feeding and welding a welding wire by push-pull feed control using a push-side feed motor that rotates in the forward direction and a pull-side feed motor that repeats forward and reverse rotations. [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, a forward / reverse feed arc welding method has been proposed in which the welding wire is fed alternately in a forward and reverse direction. This forward / reverse feed arc welding method can stabilize the cycle of short circuits and arcs compared to the conventional technique with a constant feed speed, and therefore can improve the welding quality by reducing the amount of spatter and improving the bead appearance.

[0004] In forward and reverse feed arc welding, it is necessary to switch the forward and reverse feed of the welding wire at high speed and high accuracy at about 100 Hz. For this reason, a push-pull feeding method is often adopted as the feeding method. Furthermore, an intermediate wire storage section that temporarily stores the welding wire is often provided between the feeding paths of the push side feeding motor and the pull side feeding motor.

[0005] In the forward / reverse feed arc welding method, the forward feed period and the reverse feed period are switched in synchronization with the occurrence timing of the short circuit period and the arc period. Therefore, when the welding conditions such as the set value of the welding voltage and the projection length change and the time ratio between the short circuit period and the arc period changes, the time ratio between the forward feed period and the reverse feed period also changes, so that the average feed speed of the welding wire changes. When the average feed speed changes, the deposition amount changes, so that the welding quality deteriorates. To address this problem, in the invention of Patent Document 1, the push side motor feeds the wire forward at a constant speed, the capacity of the intermediate wire housing section is detected, and the pull feed speed of the pull side motor is corrected and controlled based on this capacity. This correction control suppresses the average feed speed from changing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-99945 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional correction control of the forward and reverse feed arc welding method, the forward feed peak value and the reverse feed peak value of the pull feed speed are changed based on the capacity of the intermediate wire housing. However, if the feed path changes abruptly and significantly during welding, the feed resistance increases and the correction control of the pull feed speed may not be able to keep up. As a result, the average value of the pull feed speed fluctuates, resulting in a problem of poor welding quality.

[0008] Therefore, an object of the present invention is to provide an arc welding control method in a forward / reverse feed arc welding method, which is capable of maintaining the average pull feed speed at a predetermined value and obtaining good welding quality even when the feed resistance fluctuates suddenly and significantly. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a welding wire feeder that feeds a welding wire by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations, an intermediate wire accommodating portion for temporarily accommodating the welding wire is provided between the push-side feed motor and the pull-side feed motor; 1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising: correcting a push feed speed of the push-side feed motor based on a storage capacity of the intermediate wire storage section; The average feed speed of the pull-side feed motor is set to a predetermined pull average feed speed setting value. The pull side feed motor The waveform parameters of the pull feed rate are Correction , The correction of the waveform parameters is performed by correcting a forward feed peak value and / or a reverse feed peak value at a phase where the pull feed speed is 0. The present invention relates to an arc welding control method. Effect of the Invention

[0013] According to the present invention, in the forward / reverse feed arc welding method, even if the feed resistance changes suddenly and significantly, the average pull feed speed can be maintained at a predetermined value, thereby obtaining good welding quality. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram of a welding power source 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 power source 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 power source for carrying out an arc welding control method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] [Embodiment 1] 1 is a block diagram of a welding power source 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.

[0017] 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.

[0018] The reactor WL smoothes the output voltage E. The inductance value of the reactor WL is, for example, 100 μH.

[0019] The push side feed motor WMP receives a push feed control signal Fcp (described later) as an input and rotates in the forward direction to feed the welding wire 1 in the forward direction at a push feed speed Fwp. The pull side feed motor WM receives a pull feed control signal Fc (described later) as an input and alternately rotates in the forward direction and reverse direction to feed the welding wire 1 in the forward and reverse feed speed Fw. The push side feed motor WMP is provided on the upstream side of the feed path, and the pull side feed motor WM is provided on the downstream side. Both feed motors are speed controlled. Both feed motors constitute a push-pull feed control system.

[0020] The intermediate wire housing WB is provided in the feed path between the push-side feed motor WMP and the pull-side feed motor WM, temporarily houses and accommodates the welding wire 1, and outputs a capacity signal Wb corresponding to the capacity. The intermediate wire housing WB is commonly used in the prior art, so a detailed structure thereof will be omitted. The capacity of the welding wire 1 is detected by a mechanical principle, an electrical principle, an optical principle, a magnetic principle, or a combination of these principles.

[0021] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to the above-mentioned pull-side 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 it. A shielding gas (not shown) is ejected from the tip of the welding torch 4 to shield the arc 3 from the atmosphere.

[0022] The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E, and outputs an output voltage detection signal Ed.

[0023] The voltage error amplifier circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed as inputs, amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-), and outputs a voltage error amplified signal Ev.

[0024] The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD receives the voltage detection signal Vd as input and outputs a short circuit determination signal Sd that goes to High level when this value is less than a predetermined short circuit determination value (about 10 V) and determines that the short circuit period is occurring, and goes to Low level when this value is equal to or greater than this value and determines that the arc period is occurring.

[0025] The push feed speed initial value setting circuit FSRP outputs a push feed speed initial value setting signal Fsrp that is a predetermined positive value.

[0026] The capacity setting circuit WBR outputs a predetermined capacity setting signal Wbr which is a target value. The capacity error amplifier circuit EW receives the capacity setting signal Wbr and the capacity signal Wb, amplifies the error between the capacity setting signal Wbr(+) and the capacity signal Wb(-), and outputs a capacity error amplified signal Ew. Ew=G·(Wbr-Wb), where G is a positive amplification factor. Therefore, when the capacity signal Wb is larger than the capacity setting signal Wbr which is the target value, the capacity error amplified signal Ew is a negative value, and when the capacity signal Wb is smaller than the capacity setting signal Wbr which is the target value, the capacity error amplified signal Ew is a positive value.

[0027] The push feed speed correction circuit FHP receives the above push feed speed initial value setting signal Fsrp and the above storage amount error amplification signal Ew as inputs, performs correction control of Frp=Fsrp+∫Ew·dt, and outputs the push feed speed setting signal Frp.

[0028] The push feed control circuit FCP receives the push feed speed setting signal Frp as an input and outputs a push feed control signal Fcp to the push side feed motor WMP for feeding the welding wire 1 at a push feed speed Fwp corresponding to the value of the push feed speed setting signal Frp.

[0029] The forward transfer acceleration period setting circuit TSUR outputs a predetermined forward transfer acceleration period setting signal Tsur.

[0030] The normal transmission deceleration period setting circuit TSDR outputs a predetermined normal transmission deceleration period setting signal Tsdr.

[0031] The reverse transport acceleration period setting circuit TRUR outputs a predetermined reverse transport acceleration period setting signal Trur.

[0032] The reverse transport deceleration period setting circuit TRDR outputs a predetermined reverse transport deceleration period setting signal Trdr.

[0033] The positive transmission peak initial value setting circuit WSS outputs a predetermined positive transmission peak initial value setting signal Wss.

[0034] The reverse transmission peak initial value setting circuit WRS outputs a predetermined reverse transmission peak initial value setting signal Wrs.

[0035] The pull average feed speed setting circuit FAR outputs a pull average feed speed setting signal Far, which is a predetermined target value. The pull average feed speed detection circuit FAD receives a pull feed speed setting signal Fr, which will be described later, as an input, calculates an average value, and outputs a pull average feed speed detection signal Fad. The number of revolutions of the pull side feed motor WM may be detected by an encoder or the like, and the pull average feed speed detection signal Fad may be output. The pull average feed speed error amplification circuit EF receives the above pull average feed speed setting signal Far and the above pull average feed speed detection signal Fad as input, amplifies the error between the pull average feed speed setting signal Far(+) and the pull average feed speed detection signal Fad(-), and outputs a pull average feed speed error amplification signal Ef. Ef=Gf·(Far-Fad), where Gf is a positive amplification factor. Therefore, when the pull average feed speed detection signal Fad is greater than the target value of the pull average feed speed setting signal Far, the pull average feed speed error amplification signal Ef has a negative value, and when the pull average feed speed detection signal Fad is smaller than the target value of the pull average feed speed setting signal Far, the pull average feed speed error amplification signal Ef has a positive value.

[0036] The pull feed speed correction circuit FH receives the forward feed peak initial value setting signal Wss, the reverse feed peak initial value setting signal Wrs, and the pull average feed speed error amplification signal Ef as inputs, selects one of the following processes 1) to 5), performs correction control, and outputs a forward feed peak value setting signal Wsr and a reverse feed peak value setting signal Wrr. The correction control (modulation control) shown below is performed at every predetermined control period. The control period is a period longer than one period of forward and reverse feed, which is about 5 ms, and is, for example, 5 to 100 ms. The correction control shown below is for a case where the control system is P control, but it may be PI control or PID control. Process 1) When correcting and controlling only the forward peak value The forward feed peak initial value setting signal Wss is corrected (modulated) by the pull average feed speed error amplification signal Ef to output the forward feed peak value setting signal Wsr=Wss+Ef, and the reverse feed peak initial value setting signal Wrs is output as it is as the reverse feed peak value setting signal Wrr=Wrs. Process 2) When only the reverse peak value is corrected and controlled The reverse feed peak initial value setting signal Wrs is corrected (modulated) by the pull average feed speed error amplification signal Ef to output the reverse feed peak value setting signal Wrr=Wrs+Ef. The forward feed peak initial value setting signal Wss is output as it is as the forward feed peak value setting signal Wsr=Wss. Process 3) When correcting and controlling the forward and reverse peak values The forward feed peak initial value setting signal Wss is corrected (modulated) by the pull average feed speed error amplified signal Ef to output a forward feed peak value setting signal Wsr = Wss + Ef, and the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the pull average feed speed error amplified signal Ef to output a reverse feed peak value setting signal Wrr = Wrs + Ef. Process 4) First case of correcting and controlling the forward feed peak value and the reverse feed peak value according to the sign of the pull average feed speed error amplification signal Ef When the pull average feed speed error amplified signal Ef≧0, the forward feed peak initial value setting signal Wss is corrected (modulated) by the pull average feed speed error amplified signal Ef to output a forward feed peak value setting signal Wsr=Wss+Ef. On the other hand, when the pull average feed speed error amplified signal Ef<0, the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the pull average feed speed error amplified signal Ef to output a reverse feed peak value setting signal Wrr=Wrs+Ef. Process 5) A second case in which the forward feed peak value and the reverse feed peak value are corrected and controlled according to the sign of the pull average feed speed error amplification signal Ef When the pull average feed speed error amplified signal Ef<0, the forward feed peak initial value setting signal Wss is corrected (modulated) by the pull average feed speed error amplified signal Ef to output the forward feed peak value setting signal Wsr=Wss+Ef. On the other hand, when the pull average feed speed error amplified signal Ef≧0, the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the pull average feed speed error amplified signal Ef to output the reverse feed peak value setting signal Wrr=Wrs+Ef.

[0037] The pull 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 peak value setting signal Wsr, the reverse feed peak value setting signal Wrr, and the short circuit determination signal Sd as inputs, and outputs a pull feed speed pattern generated by the following process as a pull feed speed setting signal Fr. When this pull 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 pull feed speed setting signal Fr that linearly accelerates from 0 to the forward feed peak value Wsp, which is a positive value determined by the forward feed peak value setting signal Wsr, is output. 2) Subsequently, during the forward feed peak period Tsp, the pull feed speed setting signal Fr for maintaining the forward feed peak value 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 system transitions to a forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and outputs a pull feed speed setting signal Fr that linearly decelerates from the forward feed peak value Wsp to 0. 4) Next, during the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur, the pull feed speed setting signal Fr is output, which linearly accelerates from 0 to the reverse peak value Wrp, which is a negative value determined by the reverse peak value setting signal Wrr. 5) Subsequently, during the backward feed peak period Trp, the pull feed speed setting signal Fr for maintaining the above-mentioned backward feed peak value 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 pull feed speed setting signal Fr that linearly decelerates from the reverse feed peak value Wrp to 0 is output. 7) By repeating the above steps 1) to 6), a pull feed speed setting signal Fr is generated having a feed pattern that changes like a positive and negative trapezoidal wave.

[0038] The pull feed control circuit FC receives the pull feed speed setting signal Fr as an input and outputs a pull feed control signal Fc to the pull side feed motor WM for feeding the welding wire 1 at a pull feed speed Fw corresponding to the value of the pull feed speed setting signal Fr.

[0039] 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.

[0040] 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.

[0041] The constriction detection circuit ND takes the above short - circuit discrimination signal Sd, the above voltage detection signal Vd, and the above 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 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 voltage detection signal Vd during the short - circuit period reaches the corresponding reference value. Further, the value of the voltage detection signal Vd is divided by the value of the 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.

[0042] 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 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.

[0043] 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, this drive signal Dr becomes Low level when constriction is detected, the transistor TR becomes 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 becomes on, and the current - reducing resistor R is short - circuited and returns to the normal state.

[0044] The current control setting circuit ICR receives the short circuit determination signal Sd, the low level current setting signal Ilr, and the constriction detection signal Nd as inputs, performs the following processing, and outputs a current control setting signal Icr. 1) When the short circuit determination signal Sd is at a low level (arcing period), a current control setting signal Icr which becomes a low-level current setting signal Ilr is output. 2) 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. 3) 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.

[0045] 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.

[0046] The current fall time setting circuit TDR outputs a predetermined current fall time setting signal Tdr.

[0047] The small current period circuit STD receives as input the above-mentioned short circuit determination signal Sd and the above-mentioned current drop time setting signal Tdr, and outputs a small current period signal Std that goes to a high level when a time determined by the current drop time setting signal Tdr 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).

[0048] The power supply characteristics switching circuit SW receives the current error amplified signal Ei, the voltage error amplified signal Ev, the short circuit determination signal Sd, and the small current period signal Std as inputs, performs the following processing, and outputs an error amplified signal Ea. 1) During the period from the point when the short circuit determination signal Sd changes to a high level (short circuit period) to the point when a predetermined delay period has elapsed after the short circuit determination signal Sd changes to a low level (arc period), the current error amplified signal Ei is output as the error amplified signal Ea. 2) During the subsequent high current arc period, the voltage error amplified signal Ev is output as the error amplified signal Ea. 3) During the subsequent small current arc period when the small current period signal Std is at a high level, 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 and small current arc period, and constant voltage characteristics during other large current arc periods.

[0049] Fig. 2 is a timing chart of each signal in the welding power source 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 pull 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 small current period signal Std, and Fig. 2(F) shows the change over time of the push feed speed Fwp. The operation of each signal will be explained below with reference to the figure.

[0050] The pull feed speed Fw shown in FIG. 1(A) is controlled by the value of the pull feed speed setting signal Fr output from the pull feed speed setting circuit FR in FIG. 1. The pull 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 peak value Wsp is determined by the forward feed peak value setting signal Wsr in FIG. 1, and the reverse feed peak value Wrp is determined by the reverse feed peak value setting signal Wrr in FIG. 1. As a result, the pull feed speed setting signal Fr becomes a feed pattern that changes in a substantially trapezoidal wave shape of positive and negative. 1. Moreover, the push feed speed Fwp shown in FIG. 1(F) is the forward feed speed determined by the push feed speed setting signal Frp in FIG.

[0051] [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, the system transitions to a predetermined forward feed deceleration period Tsd from time t1 to t2, and the pull feed speed Fw decelerates from the forward feed peak value Wsp to 0 as shown in FIG. 1A. For example, the forward feed deceleration period Tsd is set to 1 ms.

[0052] As shown in FIG. 1A, the pull feed speed Fw enters a predetermined reverse acceleration period Tru from time t2 to t3, and accelerates from 0 to the reverse peak value Wrp. During this period, the short circuit period continues. For example, the reverse acceleration period Tru is set to 1 ms.

[0053] When the reverse acceleration period Tru ends at time t3, as shown in FIG. 1A, the pull feed speed Fw enters the reverse peak period Trp and becomes the reverse peak value Wrp. The reverse peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is the short circuit period. The reverse peak period Trp is not a predetermined value, but is about 2 ms.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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. 1B, 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. 1B, the welding current Iw maintains the low level current value until a predetermined delay period has elapsed since the arc re-ignition, 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 = 175 A / ms, short circuit peak value = 400 A, low level current value = 50 A, delay period = 0.5 ms.

[0058] [Arc period from time t4 to t7] At time t4, when the pinch force caused by the reverse feed of the welding wire and the passage of the welding current Iw causes the necking to progress and an arc to be generated, as shown in FIG. 1C, the welding voltage Vw rapidly rises 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 system transitions to a predetermined reverse feed deceleration period Trd from time t4 to t5, and the pull feed speed Fw decelerates from the reverse feed peak value Wrp to 0 as shown in FIG. 1A. For example, the reverse feed deceleration period Trd is set to 1 ms.

[0059] 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 pull feed speed Fw accelerates from 0 to the forward feed peak value Wsp. During this period, the arc period continues. For example, the forward feed acceleration period Tsu is set to 1 ms.

[0060] When the forward acceleration period Tsu ends at time t6, as shown in FIG. 1A, the pull feed speed Fw enters the forward feed peak period Tsp and becomes the forward feed peak value Wsp. The arc period continues during this period. The forward feed 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 feed peak period Tsp is not a predetermined value, but is about 4 ms.

[0061] 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-level current value during the delay period from time t4 to t41. After that, from time t41, the welding current Iw increases rapidly to a peak value, and then decreases gradually to a large current value. During this high-current arc period from time t41 to t61, the welding power source is feedback-controlled by the voltage error amplification signal Ev in FIG. 1, resulting in a constant voltage characteristic. Therefore, the value of the welding current Iw during the high-current arc period varies depending on the arc load.

[0062] At time t61, when the current drop time determined by the current drop time setting signal Tdr in FIG. 1 has elapsed since the arc was generated at time t4, the small current period signal Std changes to a high level, as shown in FIG. 1(E). In response to this, the welding power source is switched from the constant voltage characteristics to the constant current characteristics. For this reason, as shown in FIG. 1(B), the welding current Iw drops to a low level current value and maintains that value until time t7 when a short circuit occurs. Similarly, as shown in FIG. 1(C), the welding voltage Vw also drops. When a short circuit occurs at time t7, the small current period signal Std returns to a low level.

[0063] In the figure, the forward feed peak value Wsp (forward feed peak value setting signal Wsr) and / or the reverse feed peak value Wrp (reverse feed peak value setting signal Wrr) are corrected and controlled by the pull feed speed correction circuit FH in Fig. 1 by selecting one of processes 1) to 5). In the correction control, the forward feed peak value Wsp and / or the reverse feed peak value Wrp are corrected so that the value of the pull average feed speed detection signal Fad in Fig. 1 becomes equal to the value of the predetermined pull average feed speed setting signal Far in Fig. 1. As a result, the average value of the pull feed speed Fw becomes the value of the pull average feed speed setting signal Far.

[0064] Further, the push feed speed Fwp shown in Fig. 1(F) (push feed speed setting signal Frp in Fig. 1) is corrected and controlled by the push feed speed correction circuit FHP in Fig. 1. In the correction control, the push feed speed Fwp is corrected so that the value of the storage amount signal Wb from the intermediate wire storage portion WB in Fig. 1 becomes equal to the value of the predetermined storage amount setting signal Wbr in Fig. 1.

[0065] According to the above-mentioned embodiment 1, the push feed speed of the push side feed motor is corrected based on the capacity of the intermediate wire housing, and the waveform parameter of the pull feed speed is corrected so that the average feed speed of the pull side feed motor is equal to the predetermined pull average feed speed setting value. The waveform parameter is a forward feed peak value and / or a reverse feed peak value. In the conventional technology, when the feed path changes abruptly and significantly during welding, the feed resistance increases, and the correction control of the pull feed speed cannot follow, resulting in a problem that the average value of the pull feed speed fluctuates. In contrast, in this embodiment, even if the feed resistance changes abruptly, the push feed speed is corrected and controlled so that the capacity of the intermediate wire housing becomes the target value. As a result, the load on the pull side feed motor is reduced, and the followability of the correction control of the pull feed speed can be improved. Therefore, in this embodiment, even if the feed resistance changes significantly, the average value of the pull feed speed can be maintained constant, and good welding quality can be maintained.

[0066] [Embodiment 2] In the invention of the embodiment 2, the correction control of the pull feed speed described above in the embodiment 1 is performed in synchronization with a predetermined phase of the waveform parameter of the pull feed speed. The predetermined phase is, for example, a phase where the pull feed speed becomes 0.

[0067] Fig. 3 is a block diagram of a welding power source for implementing an arc welding control method according to a second embodiment of the present invention. This figure corresponds to Fig. 1 described above, and the same blocks are given the same reference numerals and their description will not be repeated. In this figure, the pull feed speed correction circuit FH in Fig. 1 is replaced with a second pull feed speed correction circuit FH2. This block will be described below with reference to this figure.

[0068] The second pull feed speed correction circuit FH2 receives the pull feed speed setting signal Fr, the forward feed peak initial value setting signal Wss, the reverse feed peak initial value setting signal Wrs, and the pull average feed speed error amplification signal Ef as inputs, selects one of the processes 1) to 5) described above in the first embodiment, performs correction control based on the pull average feed speed error amplification signal Ef at the time when the waveform of the pull feed speed setting signal Fr reaches a predetermined phase, and outputs the forward feed peak value setting signal Wsr and the reverse feed peak value setting signal Wrr.

[0069] The timing chart of each signal in Fig. 3 is omitted because it is the same as that in Fig. 2 described above. However, it is different in that the update of the pull feed speed Fw by the correction control is performed in synchronization with a predetermined phase of the pull feed speed Fw. The predetermined phase includes the following cases shown in Fig. 2(A). 1) The start of the forward deceleration period Tsd at time t1 (the time when a short circuit occurs) 2) At time t2, the pull feed speed Fw=0 when the forward feed is switched to the reverse feed 3) The start of the back-transmission peak period Trp at time t3 4) The start of the reverse deceleration period Trd at time t4 (the time when the arc occurs) 5) At time t5, the pull feed speed Fw=0 when the reverse feed is switched to the forward feed 6) The start point of the forward peak period Tsp at time t6

[0070] According to the above-mentioned embodiment 2, the pull feed speed is corrected in synchronization with a predetermined phase of the waveform parameter of the pull feed speed. In this way, the pull feed speed is updated in the same welding state, so that the welding state is stabilized.

[0071] Furthermore, it is more preferable that the predetermined phase is a phase where the pull feed speed is 0. In this way, the pull feed speed is updated smoothly without abrupt changes, so that the welding state becomes more stable. [Explanation of symbols]

[0072] 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 E Output voltage Ea Error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EF pull average feed speed error amplifier circuit Ef Pull average feed speed error amplified signal EI Current Error Amplifier Circuit Ei Current error amplification signal ER Output voltage setting circuit Er Output voltage setting signal EV voltage error amplifier circuit Ev Voltage error amplified signal EW Capacity Error Amplifier Circuit Ew Capacity error amplified signal FAD pull average feed speed detection circuit Fad pull average feed speed detection signal FAR pull average feed speed setting circuit Far pull average feed speed setting signal FC pull feed control circuit Fc Pull feed control signal FCP Push feed control circuit Fcp Push feed control signal FH pull feed speed correction circuit FH2 2nd pull feed speed compensation circuit FHP Push feed speed correction circuit FR pull feed speed setting circuit Fr Pull feed speed setting signal Frp push feed speed setting signal FSRP Push feed speed initial value setting circuit Fsrp Push feed speed initial value setting signal Fw pull feed speed Fwp Push Feeding Speed ICR Current control setting circuit Icr Current control setting signal ID Current Detection Circuit Id Current detection signal ILR Low level current setting circuit Ilr Low level 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 STD Low current period circuit Std Small current period signal SW Power supply characteristic switching circuit TDR current fall time setting circuit Tdr Current fall time setting signal 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 voltage detection circuit Vd Voltage detection signal Vw welding voltage WB Intermediate wire storage Wb Capacity Signal WBR Capacity Setting Circuit Wbr Capacity setting signal WL Reactor WM pull side feed motor WMP Push side feed motor Wrp Reverse peak value Wrr Reverse transmission peak value setting signal WRS Back-transmission peak initial value setting circuit Wrs Backward peak initial value setting signal Wsp forward peak value Wsr Positive transmission peak value setting signal WSS Positive transmission peak initial value setting circuit Wss Positive transmission peak initial value setting signal

Claims

1. The welding wire is fed by push-pull feed control using a push-side feed motor that rotates in a forward direction and a pull-side feed motor that repeats forward and reverse rotations; an intermediate wire accommodating portion for temporarily accommodating the welding wire is provided between the push-side feed motor and the pull-side feed motor; 1. A method for controlling arc welding in which a short circuit period and an arc period are repeated, comprising: correcting a push feed speed of the push-side feed motor based on a storage capacity of the intermediate wire storage section; correcting a waveform parameter of a pull feed speed of the pull-side feed motor so that the average feed speed of the pull-side feed motor becomes equal to a predetermined pull average feed speed setting value; The correction of the waveform parameters is performed by correcting a forward feed peak value and / or a reverse feed peak value at a phase where the pull feed speed is 0.

2. An arc welding control method comprising:

Images