JP2018008304A - Output control method for arc welding power supply - Google Patents

Abstract

To improve arc stability in a welding method in which a feed speed of a welding wire is alternately switched between a forward feed period and a reverse feed period to perform control for removing abnormal voltage. Abnormal voltage removal control is performed to limit a detection value of a welding voltage Vw within a predetermined allowable range centered on a reference voltage value corresponding to a detection value of a welding current Iw and calculate a voltage limit value Vf. And output control of the welding voltage Vw is performed based on the voltage limit value Vf. The allowable range of the abnormal voltage removal control is set to a larger value as the volume% of the inert gas in the shield gas increases. As the inert gas ratio increases, the change in arc length increases and the change in welding voltage Vw also increases. According to the present invention, it is possible to prevent a large change in the welding voltage Vw from being erroneously determined as an abnormal voltage, so that arc stability can be improved. [Selection] Figure 2

Description

  According to the present invention, the welding wire feeding speed is alternately switched between the forward feeding period and the reverse feeding period, the short-circuit period and the arc period are repeatedly welded, the abnormal voltage superimposed on the welding voltage is removed, and this welding voltage is set. The present invention relates to an output control method for an arc welding power source that performs output control based on the output.

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

  In order to further improve the welding quality, a method has been proposed in which welding is performed by periodically repeating forward and reverse feeding of the welding wire. In invention of patent document 1, it is set as the average value of the feeding speed according to the welding current setting value, and the frequency and amplitude of the forward feed and reverse feeding of the welding wire are values according to the welding current setting value. In the welding method that repeats forward and reverse feeding of the welding wire, it is possible to stabilize the repetition cycle of the short circuit and the arc as compared with the conventional technique of constant speed feeding.

  In consumable electrode arc welding, maintaining the apparent arc length (hereinafter simply referred to as arc length), which is the shortest distance between the tip of the welding wire and the base metal, to an appropriate value is to obtain good welding quality. Is important. For this reason, the arc welding power source is controlled at a constant voltage during the arc period. This is based on the fact that the arc length and welding voltage are in a proportional relationship, and the arc length is detected by the welding voltage, and the welding voltage detection value is output so as to be equal to the voltage setting value corresponding to the appropriate arc length. This is because the arc length is maintained at an appropriate value by controlling. Therefore, in order to stabilize the arc length control, it is necessary to detect the arc length with high accuracy by the welding voltage.

  Since consumable electrode arc welding is usually performed with electrode positive polarity EP, an anode spot is formed at the tip of the welding wire, a cathode spot is formed on the surface of the base material, and between the anode spot and the cathode spot. An arc is generated. The anode point hardly moves when it is formed near the tip of the wire. On the other hand, the cathode spot moves steadily toward a portion having an oxide film on the surface of the base material. Furthermore, the cathode spot fluctuates due to contamination of the surface of the base material, the movement state of the molten pool, gas discharge from the molten pool, and the like. Even if the cathode spot formation position changes in a short time, the apparent arc length does not change. This is because the apparent arc length changes depending on the difference between the wire feed speed and the wire melting speed, and can only change minutely in a short time of 10 or less ms. However, if the cathode spot fluctuates due to the various causes described above, an abnormal voltage is superimposed on the welding voltage. This abnormal voltage is a voltage that is not proportional to the apparent arc length. For this reason, if output control is performed based on the welding voltage on which this abnormal voltage is superimposed, the arc length control system becomes unstable and the welding quality deteriorates. Patent Document 2 discloses a method for generating a welding voltage detection value that is proportional to an apparent arc length by removing an abnormal voltage from the welding voltage detection value.

  In the invention of Patent Document 2, the current capacity of the welding power source is divided into a plurality of current regions, and a reference welding voltage value is set for each of these current regions. The welding current and welding voltage are detected, a current region that matches the detected value of the welding current is selected, and the detection value of the welding voltage is limited within the allowable range with the reference welding voltage value of the selected current region as the center value. The welding voltage limit value from which the abnormal voltage is removed is calculated. The welding voltage is output controlled based on the welding voltage limit value.

Japanese Patent No. 52012266 Japanese Patent No. 5214859

  A welding method that repeats forward feeding and reverse feeding of a welding wire and performs output control based on a welding voltage from which an abnormal voltage has been removed is mainly used when the base material is a steel material. When this welding method is applied to a stainless steel material, there is a problem that the arc becomes unstable and the amount of spatter increases. This is because, firstly, the change in the apparent arc length increases because the feeding speed continuously and steeply changes during the arc period. Second, since the arc stability of stainless steel has a lower arc stability than the arc welding of steel, the apparent arc length changes greatly.

  Therefore, in the present invention, in the welding method in which the feed rate of the welding wire is alternately switched between the forward feed period and the reverse feed period and the output is controlled based on the welding voltage from which the abnormal voltage is removed, the base material is made of stainless steel. Even so, an object of the present invention is to provide an output control method of an arc welding power source that enables welding with stable arc and less spatter generation.

In order to solve the above-described problems, the invention of claim 1
The welding wire feed speed is alternately switched between the forward feed period and the reverse feed period, and the welding is repeated by repeating the short circuit period and the arc period.
An abnormality in which a welding current and a welding voltage are detected, and a voltage limit value is calculated by limiting the detected value of the welding voltage within a predetermined allowable range centered on a reference voltage value corresponding to the detected value of the welding current Perform voltage removal control,
In the output control method of the arc welding power source that controls the output of the welding voltage based on the voltage limit value,
The tolerance is set to a larger value when the base material is stainless steel than when it is steel.
This is an output control method of an arc welding power source characterized by the above.

The invention of claim 2 sets the allowable range to a larger value as the volume% of the inert gas occupying the shield gas increases.
The output control method for an arc welding power source according to claim 1.

The invention according to claim 3 stops the abnormal voltage removal control during a predetermined period including a period in which a change rate of the welding current during the arc period is equal to or higher than a reference change rate.
The output control method for an arc welding power source according to claim 1 or 2.

The invention according to claim 4 stops the abnormal voltage removal control during a predetermined period including a period in which the feed speed is a reverse feed deceleration value.
The output control method for an arc welding power source according to any one of claims 1 to 3.

  According to the present invention, in the welding method in which the feed rate of the welding wire is alternately switched between the forward feed period and the reverse feed period, and the output is controlled based on the welding voltage from which the abnormal voltage is removed, the material of the base material is stainless steel. Even so, it is possible to perform welding with a stable arc and a low spatter generation amount.

It is a block diagram of the welding power supply for implementing the output control method of the arc welding power supply which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 1 which shows the output control method of the arc welding power supply which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power source for enforcing the output control method of the arc welding power source which concerns on Embodiment 2 of this invention. It is a figure which shows the relationship between the inert gas ratio setting signal Ar (%) shown on a horizontal axis | shaft, and the tolerance | permissible_range setting signal Hr (V) shown on a vertical axis | shaft. It is a block diagram of the welding power supply for implementing the output control method of the arc welding power supply which concerns on Embodiment 3 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 5 which shows the output control method of the arc welding power supply which concerns on Embodiment 3 of this invention. It is a block diagram of the welding power supply for implementing the output control method of the arc welding power supply which concerns on Embodiment 4 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 7 which shows the output control method of the arc welding power supply which concerns on Embodiment 4 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
In the invention of the first embodiment, the allowable range of the abnormal voltage removal control is set to a larger value when the base material is stainless steel than when it is steel.

  FIG. 1 is a block diagram of a welding power source for carrying out an output control method for an arc welding power source according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control by inverter control or the like according to an error amplification signal Ea described later, and outputs an output voltage E. Although not shown, the power main circuit PM is driven by a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, and the error amplification signal Ea that converts the smoothed direct current to a high-frequency alternating current. An inverter circuit, a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current.

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

  The feed motor WM receives a feed control signal Fc described later and feeds the welding wire 1 at a feed speed Fw by alternately repeating forward feed and reverse feed. A motor with fast transient response is used as the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

  When the welding operator selects a number corresponding to the material of the base material, the material selection circuit MS outputs a material selection signal Ms that is the value of the number. For example, if steel is selected, Ms = 1, and if stainless steel is selected, Ms = 2.

  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 described above, and when this value is less than a predetermined short-circuit determination value (about 10 V), it determines that the short-circuit period is in effect and becomes a High level. A short circuit determination signal Sd which is determined to be in the arc period and becomes Low level is output.

  The reference voltage value setting circuit VC receives the current detection signal Id and outputs a predetermined reference voltage value signal Vc corresponding to the value of the current detection signal Id. For example, this circuit stores a function of Vc = a × Id + b. a and b are positive constants.

  The allowable range setting circuit HR receives the material selection signal Ms as described above and outputs a predetermined allowable range setting signal Hr suitable for the material selection signal Ms.

  The abnormal voltage removal circuit VF receives the voltage detection signal Vd, the reference voltage value signal Vc, and the tolerance range setting signal Hr as input, and sets the value of the voltage detection signal Vd to the reference voltage value signal Vc as a central value. The voltage limit value signal vf is output within the allowable range Vc ± Hr.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr.

  The voltage error amplifier EV receives the voltage setting signal Vr and the voltage limit value signal Vf as input, amplifies an error between the voltage setting signal Vr (+) and the voltage limit value signal Vf (−), An error amplification signal Ev is output.

  The forward feed acceleration period setting circuit TSUR outputs a predetermined forward feed acceleration period setting signal Tsur.

  The forward feed deceleration period setting circuit TSDR outputs a predetermined forward feed deceleration period setting signal Tsdr.

  The reverse acceleration period setting circuit TRUR outputs a predetermined reverse acceleration period setting signal Trur.

  The reverse feed deceleration period setting circuit TRDR outputs a predetermined reverse feed deceleration period setting signal Trdr.

  The forward feed peak value setting circuit WSR outputs a predetermined forward feed peak value setting signal Wsr.

  The reverse peak value setting circuit WRR outputs a predetermined reverse peak value setting signal Wrr.

The feed speed setting circuit FR includes 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 are input, and the feed speed pattern generated by the following processing is output as the feed speed setting signal Fr. When the 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) Feed speed setting signal Fr that linearly accelerates from 0 to a positive feed peak value Wsp determined by a forward feed peak value setting signal Wsr during the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur. Is output.
2) Subsequently, during the forward feed peak period Tsp, the feed speed setting signal Fr for maintaining the forward feed peak value Wsp is output.
3) When the short-circuit determination signal Sd changes from the Low level (arc period) to the High level (short-circuit period), it shifts to the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and from the forward feed peak value Wsp. A feed speed setting signal Fr that linearly decelerates to 0 is output.
4) Subsequently, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the feed speed that linearly accelerates from 0 to the negative reverse feed peak value Wrp determined by the reverse feed peak value setting signal Wrr. A setting signal Fr is output.
5) Subsequently, during the reverse feed peak period Trp, the feed speed setting signal Fr that maintains the reverse feed peak value Wrp is output.
6) When the short circuit determination signal Sd changes from the High level (short circuit period) to the Low level (arc period), it shifts to the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr, and from the reverse feed peak value Wrp. A feed speed setting signal Fr that linearly decelerates to 0 is output.
7) By repeating the above 1) to 6), a feed rate setting signal Fr of a feed pattern that changes in a positive and negative trapezoidal shape is generated.

  The feed control circuit FC receives the feed speed setting signal Fr and receives a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. It outputs to said feed motor WM.

  The current reducing resistor R is inserted between the reactor WL and the welding torch 4. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (about 0.01 to 0.03Ω). When the current reducing resistor R is inserted into the energization path, the energy accumulated in the reactor WL and the reactor of the external cable is suddenly discharged.

  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 described later.

  The constriction detection circuit ND receives the short circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id as inputs, and the voltage detection signal Vd when the short circuit determination signal Sd is at a high level (short circuit period). When the voltage rise value reaches the reference value, it is determined that the constriction formation state has become the reference state, and becomes a high level. When the short circuit determination signal Sd changes to the low level (arc period), the constriction detection that becomes the low level is detected. The signal Nd is output. In addition, the squeezing detection signal Nd may be changed to a high level when the differential value of the voltage detection signal Vd during the short circuit period reaches a reference value corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the corresponding reference value, the constriction detection signal Nd is calculated. You may make it change to a High level.

  The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as input, and outputs a current comparison signal Cm that is at a high level when Id <Ilr and is at a low level when Id ≧ Ilr. Output.

  The drive circuit DR receives the current comparison signal Cm and the squeezing detection signal Nd as input, and changes to a low level when the squeezing detection signal Nd changes to a high level, and then changes to a high level after the current comparison signal Cm changes to a high level. The drive signal Dr that changes to High level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. Therefore, the welding current Iw for energizing the short-circuit load decreases rapidly. . When the sharply decreased welding current Iw value decreases to the low level current setting signal Ilr value, the drive signal Dr becomes a high level and the transistor TR is turned on. Return to the state.

The current control setting circuit ICR receives the short circuit determination signal Sd, the low level current setting signal Ilr, and the squeezing detection signal Nd as input, and outputs the current control setting signal Icr.
1) When the short circuit determination signal Sd is at the low level (arc period), the current control setting signal Icr that becomes the low level current setting signal Ilr is output.
2) When the short-circuit determination signal Sd changes to the high level (short-circuit period), the initial current setting value is set during a predetermined initial period, and thereafter, the preset peak setting value during short-circuiting is set with a predetermined inclination during short-circuiting. The current control setting signal Icr that rises to and maintains that value is output.
3) After that, when the squeezing detection signal Nd changes to the high level, the current control setting signal Icr that is the value of the low level current setting signal Ilr is output.

  The current error amplifier circuit EI receives the current control setting signal Icr and the current detection signal Id as input, amplifies an error between the current control setting signal Icr (+) and the current detection signal Id (−), and An error amplification signal Ei is output.

  The small current period circuit STD receives the short-circuit determination signal Sd as described above, and goes to a high level when a predetermined current drop time elapses from when the short-circuit determination signal Sd changes to a low level (arc period). When the short circuit determination signal Sd becomes High level (short circuit period), a small current period signal Std which becomes Low level is output.

The power supply characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, the short circuit determination signal Sd, and the small current period signal Std as input, and performs the following processing to obtain an error amplification signal. Ea is output.
1) During the period from the time when the short circuit determination signal Sd changes to the high level (short circuit period) to the time when the predetermined delay period elapses after the short circuit determination signal Sd changes to the low level (arc period) The error amplification signal Ei is output as the error amplification signal Ea.
2) During the subsequent arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) During the subsequent arc period, the current error amplification signal Ei is output as the error amplification signal Ea during the period when the small current period signal Std becomes High level.
With this circuit, the characteristics of the welding power source are constant current characteristics during a short circuit period, a delay period, and a small current period, and constant voltage characteristics during other arc periods.

  FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the output control method of the arc welding power source according to the first embodiment of the present invention. (A) shows the time change of the feeding speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, (D) ) Shows a time change of the short circuit determination signal Sd, FIG. 5E shows a time change of the small current period signal Std, and FIG. 5F shows a time change of the voltage limit value signal Vf. Hereinafter, the operation of each signal will be described with reference to FIG.

  The feed speed Fw shown in FIG. 6A is controlled to the value of the feed speed setting signal Fr output from the feed speed setting circuit FR of FIG. The feed speed Fw is determined 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, and the forward feed deceleration period setting signal Tsdr in FIG. The reverse transmission period Tsd, the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur in FIG. 1, the reverse peak period Trp that continues until the arc is generated, and the reverse transmission determined by the reverse deceleration period setting signal Trdr in FIG. It is formed from the deceleration period Trd. Further, the forward peak value Wsp is determined by the forward peak value setting signal Wsr in FIG. 1, and the backward peak value Wrp is determined by the backward peak value setting signal Wrr in FIG. As a result, the feed speed setting signal Fr has a feed pattern that changes in a substantially positive and negative trapezoidal waveform.

[Operation in the short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the forward feed peak period Tsp, the welding voltage Vw rapidly decreases to a short circuit voltage value of several V as shown in FIG. The short circuit determination signal Sd changes to a high level (short circuit period). In response to this, a transition is made to a predetermined forward feed deceleration period Tsd between times t1 and t2, and the feed speed Fw is reduced from the forward feed peak value Wsp to 0 as shown in FIG. . For example, the normal feed deceleration period Tsd = 1 ms is set.

  As shown in FIG. 5A, the feed speed Fw enters a predetermined reverse feed acceleration period Tru at times t2 to t3, and accelerates from 0 to the reverse feed peak value Wrp. During this period, the short circuit period continues. For example, the reverse feed acceleration period Tru = 1 ms is set.

  When the reverse acceleration period Tru ends at time t3, the feed speed Fw enters the reverse peak period Trp and becomes the reverse peak value Wrp as shown in FIG. The reverse feed 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 transmission peak period Trp is not a predetermined value, but is about 4 ms. For example, the reverse peak value Wrp is set to −30 m / min.

  As shown in FIG. 5B, the welding current Iw during the short-circuit period from time t1 to t4 has a predetermined initial current value during a predetermined initial period. Thereafter, the welding current Iw rises with a predetermined slope at the time of short circuit, and maintains that value when it reaches a predetermined peak value at the time of short circuit.

  As shown in FIG. 6C, the welding voltage Vw increases from the point where the welding current Iw becomes the short circuit peak value. This is because a constriction is gradually formed in the droplet at the tip of the welding wire 1 due to the reverse feed of the welding wire 1 and the action of the pinch force caused by the welding current Iw.

  After that, when the voltage increase value of the welding voltage Vw reaches the reference value, it is determined that the constriction formation state has become the reference state, and the constriction detection signal Nd in FIG. 1 changes to the high level.

  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 is turned off and the current reducing resistor R in FIG. Inserted. At the same time, the current control setting signal Icr in FIG. 1 is reduced to the value of the low level current setting signal Ilr. For this reason, as shown in FIG. 5B, the welding current Iw rapidly decreases from the short-circuit peak value to the low-level current value. 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 is turned on and the current reducing resistor R is short-circuited. As shown in FIG. 6B, the welding current Iw is the low level current until the predetermined delay period elapses after the arc is regenerated because the current control setting signal Icr remains the low level current setting signal Ilr. Keep the value. Therefore, the transistor TR is turned off only during a period from when the squeezing detection signal Nd changes to the high level until the welding current Iw decreases to the low level current value. As shown in FIG. 5C, the welding voltage Vw rapidly increases after once decreasing because the welding current Iw becomes small. As shown in FIG. 5F, the voltage limit value signal Vf is similar to the welding voltage Vw shown in FIG. 5C because the abnormal voltage removal control is not performed during the short-circuit period from time t1 to time t4. It becomes the waveform.

  Each parameter mentioned above is set to the following values, for example. Initial current = 40 A, initial period = 0.5 ms, short circuit slope = 2 ms, short circuit peak value = 400 A low level current value = 50 A, delay period = 1 ms.

[Operation during arc period from time t4 to t7]
At time t4, when the constriction progresses due to the pinch force caused by the reverse feeding of the welding wire and the energization of the welding current Iw, and an arc is generated, the welding voltage Vw is an arc voltage value of several tens of volts as shown in FIG. Therefore, as shown in FIG. 4D, the short circuit determination signal Sd changes to the low level (arc period). In response to this, a transition is made to a predetermined reverse feed deceleration period Trd at times t4 to t5, and the feed speed Fw is reduced from the reverse feed peak value Wrp to 0 as shown in FIG. . For example, the reverse deceleration period Trd is set to 1.5 ms.

  When the reverse feed deceleration period Trd ends at time t5, the process proceeds to a predetermined forward feed acceleration period Tsu at times t5 to t6. During the normal feed acceleration period Tsu, the feed speed Fw is accelerated from 0 to the normal feed peak value Wsp as shown in FIG. During this period, the arc period continues. For example, the normal feed acceleration period Tsu = 1 ms is set.

  When the normal feed acceleration period Tsu ends at time t6, the feed speed Fw enters the normal feed peak period Tsp as shown in FIG. 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 the operation at time t1. The forward feed peak period Tsp is not a predetermined value, but is about 4 ms. Further, for example, the forward peak value Wsp is set to 35 m / min.

  When an arc is generated at time t4, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. On the other hand, as shown in FIG. 5B, the welding current Iw continues to have a low level current value during a delay period from time t4 to time t41 in the reverse feed deceleration period Trd. Constant current control is continued during the delay period. Switching to constant voltage control starts at time t41 when the delay period ends. For this reason, as shown in FIG. 5B, the welding current Iw increases steeply from time t41 to time t51 in the forward feed acceleration period Tsu. During the period from time t51 to time t61 in the forward feed peak period Tsp, the welding current Iw gradually decreases.

  At time t61 when a predetermined current drop time elapses after the arc is generated at time t4, the small current period signal Std changes to the high level as shown in FIG. In response to this, the welding power source is switched from the constant voltage characteristic to the constant current characteristic. For this reason, as shown in FIG. 5B, the welding current Iw decreases to a low level current value, and maintains that value until time t7 when a short circuit occurs.

  As shown in FIG. 6C, the welding voltage Vw increases rapidly when the arc occurs at time t4, and increases because the arc length is increased by reverse feed until time t41. During the period from time t41 to t51, the welding current Iw increases, so that melting of the welding wire tip is promoted, and the welding voltage Vw continues to increase. During the period from time t51 to time t61, the welding voltage Vw is basically gradually decreased because the welding wire is fed forward and the welding current Iw is also decreased. However, an abnormal voltage is superimposed in a part of the period. The welding voltage Vw during the abnormal voltage superimposition period is a larger value than the period before and after that. At time t61, when the small current period starts, the welding voltage Vw decreases rapidly. The small current period signal Std returns to the Low level when a short circuit occurs at time t7. Since the current drop time is set to about 5 ms, the timing at time t61 is during the forward feed peak period Tsp.

  As shown in FIG. 5F, the voltage limit value signal Vf during the arc period from time t4 to t7 has a waveform similar to the welding voltage Vw except during the abnormal voltage superposition period during time t51 to t61. . This is because the value of the welding voltage Vw during these periods is within the allowable range Vc ± Hr. The voltage limit value signal Vf during the abnormal voltage superposition period has a waveform that is limited by cutting the high voltage portion. This is because the value of the welding voltage Vw during the abnormal voltage superposition period exceeds the upper limit value Vc + Hr of the allowable range, and this portion is limited to Vc + Hr.

The abnormal voltage removal control is performed as follows.
1) The welding current Iw and the welding voltage Vw are detected, and the current detection signal Id and the voltage detection signal Vd are output.
2) The corresponding reference voltage value signal Vc is calculated from a predetermined function with the current detection signal Id as an input.
3) The allowable range setting signal Hr suitable for steel or stainless steel is set according to the value of the material selection signal Ms. The value of the allowable range setting signal Hr is set so that the value for stainless steel is larger than that for steel. This is because the change in arc length is greater in the case of arc welding of stainless steel than in the case of arc welding of steel. In the case of arc welding of stainless steel, if the value of the allowable range setting signal Hr is set to the same value as in the case of arc welding of steel, the value of the voltage detection signal Vd accompanying the change in arc length is erroneously determined as an abnormal voltage. It will be removed. As a result, arc length control becomes unstable.
4) An allowable range Vc ± Hr corresponding to the current detection signal Id is set.
5) The value of the voltage detection signal Vd is limited within the allowable range as follows.
When Vd <Vc−Hr, Vf = Vc−Hr
When Vc−Hr ≦ Vd ≦ Vc + Hr, Vf = Vd
When Vc + Hr ≦ Vd, Vf = Vc + Hr

  According to the first embodiment described above, in arc welding that repeats forward and reverse feeding of the welding wire, the allowable range of the abnormal voltage removal control is greater than when the base material is stainless steel than when it is steel. Also set a large value. Stainless steel arc welding has a greater change in ike length than steel arc welding. Furthermore, since the feeding speed of the welding wire is changing instead of being low, the change in the arc length is further increased. Therefore, by increasing the allowable range of the abnormal voltage removal control, the change in the welding voltage accompanying the change in the arc length is not removed. As a result, in the present embodiment, in the welding method in which the feeding speed of the welding wire is alternately switched between the normal feeding period and the reverse feeding period, and output control is performed based on the welding voltage from which the abnormal voltage is removed, the material of the base material Even if the material is stainless steel, the arc is stable and welding with less spatter generation is possible.

[Embodiment 2]
In the invention of the second embodiment, the allowable range of the abnormal voltage removal control is set to a larger value as the volume% of the inert gas in the shield gas increases.

  FIG. 3 is a block diagram of a welding power source for carrying out the output control method of the welding power source according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. In the figure, the material selection circuit MS of FIG. 1 is replaced with an inert gas ratio setting circuit AR, and the allowable range setting circuit HR of FIG. 1 is replaced with a second allowable range setting circuit HR2. Hereinafter, these blocks will be described with reference to FIG.

  The inert gas ratio setting circuit AR outputs an inert gas ratio setting signal Ar for setting the volume% of the inert gas in the shield gas. When the shielding gas is 100% carbon dioxide, Ar = 0. When the shielding gas is 80% carbon dioxide + 20% argon gas, Ar = 20. When M2 gas is carbon dioxide 2% + argon gas 98%. Ar = 98, and Ar = 100 when the argon gas is 100%.

  The second allowable range setting circuit HR2 calculates the allowable range based on a predetermined allowable range calculation function using the inert gas ratio setting signal Ar as an input and the inert gas ratio setting signal Ar as an input, An allowable range setting signal Hr is output. The allowable range calculation function will be described later with reference to FIG.

  FIG. 4 is a diagram showing the relationship between the inert gas ratio setting signal Ar (%) indicated on the horizontal axis and the allowable range setting signal Hr (V) indicated on the vertical axis. As shown in the figure, Hr = 2V when Ar = 0%, and Hr = 4V when Ar = 100%. When the material of the base material is steel, a shielding gas in the range of Ar = 0 to 20% is used. In the case of stainless steel, Ar = 98 to 100% shielding gas is used. As can be seen from the figure, the allowable range increases as the inert gas ratio increases. This is because the change in arc length increases as the inert gas ratio increases. That is, as the inert gas ratio increases, the change in the arc length increases, and unless the allowable range is increased, the welding voltage proportional to the arc length is erroneously determined as an abnormal voltage and removed.

  According to the above-described second embodiment, the allowable range increases as the inert gas ratio increases. For this reason, since an appropriate allowable range can be set according to the inert gas ratio of the shield gas to be used, the stability of the arc can be further improved.

[Embodiment 3]
In the invention of the third embodiment, the abnormal voltage removal control is stopped during a predetermined period including a period in which the change rate of the welding current during the arc period is equal to or higher than the reference change rate.

  FIG. 5 is a block diagram of a welding power source for carrying out the output control method of the welding power source according to Embodiment 3 of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by adding a current change rate discriminating circuit DI to FIG. 1 and replacing the abnormal voltage removing circuit VF of FIG. 1 with a second abnormal voltage removing circuit VF2. Hereinafter, these blocks will be described with reference to FIG.

  The current change rate determination circuit DI receives the current detection signal Id and the short-circuit determination signal Sd as input, and the change rate (differentiated value) of the current detection signal Id when the short-circuit determination signal Sd is at the low level (arc period). ) Is calculated, and a current change rate determination signal Di that is at a high level is output during a period in which this value is a predetermined reference change rate abnormality and is off-delayed by a predetermined period. That is, this circuit determines a period in which the change in the welding current Iw during the arc period is steeply abnormal in the reference value.

  The second abnormal voltage removal circuit VF2 receives the voltage detection signal Vd, the reference voltage value signal Vc, the allowable range setting signal Hr, and the current change rate determination signal Di, and receives the current change rate determination signal Di. Is at the Low level, the value of the voltage detection signal vd is limited within an allowable range Vc ± Hr with the reference voltage value signal Vc as the center value, and the voltage limit value signal vf is output. By this circuit, the abnormal voltage removal control is stopped (prohibited) during a predetermined period including a period in which the rate of change of the welding current during the arc period becomes the reference change rate abnormality.

  FIG. 6 is a timing chart of each signal in the welding power source of FIG. 5 showing an output control method of the arc welding power source according to the third embodiment of the present invention. (A) shows the time change of the feeding speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, (D) ) Shows the time change of the short circuit determination signal Sd, FIG. 5E shows the time change of the small current period signal Std, FIG. 5F shows the time change of the voltage limit value signal Vf, and is added to FIG. FIG. 5G shows the time change of the current change rate determination signal Di. This figure corresponds to FIG. 2 described above, and the description of the same operation will not be repeated. This figure differs from FIG. 2 only in the operation of the current change rate determination signal Di shown in FIG. Hereinafter, the operation of the current change rate determination signal Di will be described with reference to FIG.

  In the figure, the period from time t4 to t7 is the arc period. During this arc period, as shown in FIG. 5B, the period in which the rate of change of the welding current Iw is equal to or greater than the reference rate is the period immediately after time t41 to t51 and time t61. For this reason, as shown in FIG. 5G, the current change rate determination signal Di is at a high level during times t41 to t51 + off delay period and a period immediately after time t61 + off delay period. The abnormal voltage removal control is stopped while the current change rate determination signal Di is at the high level. The reason for this is as follows. Since the welding current Iw is changing steeply during the period of Di = High level, the arc length changes sharply. Along with this, the welding voltage Vw also changes greatly. There is a possibility that a large change in the welding voltage Vw is erroneously determined as an abnormal voltage. Therefore, erroneous determination is prevented by stopping the abnormal voltage removal control during the period of Di = High level. As a result, the arc stability can be further improved.

  According to the above-described third embodiment, the abnormal voltage removal control is stopped during a predetermined period including a period in which the change rate of the welding current during the arc period is equal to or higher than the reference change rate. As a result, it is possible to prevent erroneously determining that a change in the welding voltage due to a sharp change in the welding current during the arc period is an abnormal voltage. For this reason, the stability of the arc can be further improved. Although the present embodiment is based on the first embodiment, the same applies to the case based on the second embodiment.

[Embodiment 4]
In the invention of the fourth embodiment, the abnormal voltage removal control is stopped during a predetermined period including a period in which the feed speed becomes the reverse feed deceleration value.

  FIG. 7 is a block diagram of a welding power source for carrying out the output control method of the welding power source according to Embodiment 4 of the present invention. This figure corresponds to FIG. 5 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by adding a reverse deceleration period determination circuit DT to FIG. 5 and replacing the second abnormal voltage removal circuit VF2 of FIG. 1 with a third abnormal voltage removal circuit VF3. Hereinafter, these blocks will be described with reference to FIG.

  The reverse feed deceleration period discriminating circuit DT receives the feed speed setting signal Fr, discriminates the reverse feed deceleration period from the change in the feed speed setting signal Fr, and delays the reverse feed deceleration period by a predetermined period. During the period, a reverse transmission deceleration period determination signal Dt that is at a high level is output.

  The third abnormal voltage removing circuit VF3 includes the voltage detection signal Vd, the reference voltage value signal Vc, the allowable range setting signal Hr, the current change rate determination signal Di, and the reverse transmission deceleration period determination signal Dt. When the current change rate determination signal Di is at the low level and the reverse feed deceleration period determination signal Dt is at the low level, the value of the voltage detection signal vd is centered on the reference voltage value signal Vc. The voltage limit value signal vf is output within the allowable range Vc ± Hr. With this circuit, the abnormal voltage removal control is stopped (prohibited) during a predetermined period including a period in which the rate of change of the welding current during the arc period becomes the reference change rate abnormality or during a predetermined period including the reverse feed deceleration period.

  FIG. 8 is a timing chart of each signal in the welding power source of FIG. 7 showing an output control method of the arc welding power source according to Embodiment 4 of the present invention. (A) shows the time change of the feeding speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, (D) ) Shows the time change of the short circuit determination signal Sd, FIG. 5E shows the time change of the small current period signal Std, FIG. 5F shows the time change of the voltage limit value signal Vf, and FIG. ) Shows the time change of the current change rate determination signal Di, and in addition to FIG. 6, (H) shows the time change of the reverse feed deceleration period determination signal Dt. This figure corresponds to FIG. 6 described above, and the description of the same operation will not be repeated. This figure differs from FIG. 6 only in the operation of the reverse feed deceleration period determination signal Dt shown in FIG. Hereinafter, the operation of the reverse feed deceleration period determination signal Dt will be described with reference to FIG.

  In the figure, the period from time t4 to t5 is the reverse feed deceleration period Trd. Therefore, as shown in FIG. 5H, the reverse feed deceleration period determination signal Dt is high during the reverse feed deceleration period Trd + off delay period. Become a level. The abnormal voltage removal control is stopped while the reverse feed deceleration period determination signal Dt is at a high level. The reason for this is as follows. During the period of Dt = High level, it is during the arc period and the welding wire is being fed back, so the arc length changes sharply. Along with this, the welding voltage Vw also changes greatly. There is a possibility that a large change in the welding voltage Vw is erroneously determined as an abnormal voltage. Therefore, erroneous determination is prevented by stopping the abnormal voltage removal control during the period of Dt = High level. As a result, the arc stability can be further improved.

  According to the above-described fourth embodiment, the abnormal voltage removal control is stopped during a predetermined period including a period in which the feed speed becomes the reverse feed deceleration value. Thereby, it can prevent misidentifying that the change of the welding voltage accompanying the welding wire being reversely fed during the arc period is an abnormal voltage. For this reason, the stability of the arc can be further improved. Although the present embodiment is based on the third embodiment, the same applies to the first or second embodiment.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AR Inert gas ratio setting circuit Ar Inert gas ratio setting signal CM Current comparison circuit Cm Current comparison signal DI Current change rate discrimination circuit Di Current change rate discrimination signal DR Drive circuit Dr Drive signal DT Reverse feed deceleration period discrimination circuit Dt Reverse feed deceleration period discrimination signal E Output voltage Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EP Electrode plus polarity EV Voltage error amplification circuit Ev Voltage error amplification signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fw feed speed HR tolerance range setting circuit Hr tolerance range setting signal HR2 second tolerance range setting circuit 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 MS Material selection circuit Ms Material selection signal ND Constriction detection circuit Nd Constriction detection signal PM Power supply main circuit R Current reducing resistor SD Short circuit determination circuit Sd Short circuit determination signal STD Small current period circuit Std Small current period signal SW Power supply characteristics Switching circuit TR transistor reverse feed deceleration period TRDR reverse feed deceleration period setting circuit Trrd reverse feed deceleration period setting signal Trp reverse feed peak period Tru reverse feed acceleration period TRUR reverse feed acceleration period setting circuit Trur reverse feed acceleration period setting signal Tsd forward feed Deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp Forward feed peak period Tsu Su Forward feed acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal VC Reference voltage setting circuit Vc Reference voltage value signal VD voltage detection circuit Vd voltage detection signal VF abnormal voltage removal circuit Vf voltage limit value signal VF2 second abnormal electric power Removal circuit VF3 Third abnormal voltage removal circuit VR Voltage setting circuit Vr Voltage setting signal Vw Welding voltage WL Reactor WM Feeding motor Wrp Reverse feed peak value WRR Reverse feed peak value setting circuit Wrr Reverse feed peak value setting signal Wsp Forward feed peak value WSR Forward feed peak value setting circuit Wsr Forward feed peak value setting signal

Claims (4)

The welding wire feed speed is alternately switched between the forward feed period and the reverse feed period, and the welding is repeated by repeating the short circuit period and the arc period.
An abnormality in which a welding current and a welding voltage are detected, and a voltage limit value is calculated by limiting the detected value of the welding voltage within a predetermined allowable range centered on a reference voltage value corresponding to the detected value of the welding current Perform voltage removal control,
In the output control method of the arc welding power source that controls the output of the welding voltage based on the voltage limit value,
The tolerance is set to a larger value when the base material is stainless steel than when it is steel.
An output control method for an arc welding power supply characterized by the above. The allowable range is set to a larger value as the volume% of the inert gas in the shielding gas increases.
The output control method for an arc welding power source according to claim 1. During a predetermined period including a period in which the change rate of the welding current during the arc period is equal to or higher than a reference change rate, the abnormal voltage removal control is stopped.
The output control method for an arc welding power source according to claim 1 or 2. The abnormal voltage removal control is stopped during a predetermined period including a period in which the feeding speed is a reverse deceleration value.
The output control method of an arc welding power source according to any one of claims 1 to 3.

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