JP2011050967A - Arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of welding quality caused by the temperature rising of a welding torch temperature and the reduction of welding electric current value through repeated welding in consumable electrode arc welding. <P>SOLUTION: The arc welding method is such that, during a welding period Ta, a welding wire is fed from a welding torch at a feeding speed Fw corresponding to a welding current set value Ir, with a welding current Iw energized to perform welding, that, during a suspension period Tb, the feeding of a welding wire is stopped to suspend welding, and that welding is performed by repeating these periods. In this method, the welding current I1 during the welding period Ta is detected, with the suspension period Tb set up in accordance with deviation between the welding current set value Ir and the welding current detection value I1. As a result, the temperature rising of the welding torch is indirectly detected by the deviation, with the suspension period extended, so that the welding torch temperature is lowered, suppressing an adverse effect on welding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an arc welding method capable of compensating for a change in welding quality accompanying a rise in temperature of a welding torch.

  FIG. 5 is a general configuration diagram of a consumable electrode arc welding apparatus using a robot. Hereinafter, each component will be described with reference to FIG.

  The teach pendant TP is connected to the robot controller RC and teaches the operation trajectory of the robot RM and sets welding conditions. The robot controller RC outputs an operation control signal Mc for controlling the operation of the robot RM to a plurality of servo motors (not shown) provided in the robot RM. A feed motor WM and a welding torch 4 are mounted on the robot RM. The feed motor WM and the welding torch 4 are connected by a conduit cable 4 a, and the welding wire 1, shield gas (not shown) and electric power are supplied to the welding torch 4.

  The welding power source PS outputs a welding voltage Vw and a welding current Iw for generating the arc 3, and a feed control signal Fc for controlling the feed motor WM. The welding wire 1 is fed by the feeding motor WM through the conduit cable 4a at a feeding speed Fw (cm / min), and an arc 3 is generated between the welding wire 1 and the base material 2.

  An interface signal If is communicated between the robot controller RC and the welding power source PS. The interface signal If includes a welding start signal St, a welding current setting signal Ir, and a welding voltage setting signal Vr transmitted from the robot controller RC, and a current energization signal Wcr transmitted from the welding power source PS. It is. The welding start signal St is a signal for controlling the output of the welding power source PS and the start / stop of the feeding of the welding wire 1. The welding current setting signal Ir is a signal that is converted into the feeding speed setting signal Fr in the welding power source PS and sets the feeding speed Fw of the welding wire 1. In consumable electrode arc welding, since the output of the welding power source PS is controlled at a constant voltage, the welding current Iw is determined by the feed speed Fw. Said welding voltage setting signal Vr is a signal which sets the welding voltage Vw by which constant voltage control is carried out. The current energization signal Wcr is a signal that becomes a high level when the welding current Iw is energized. When the current energization signal Wcr becomes High level at the start of welding, the robot controller RC starts the movement of the robot RM along the welding line.

  FIG. 6 is a timing chart of each signal in the above-described welding apparatus when welding is repeatedly performed. FIG. 4A shows the time change of the welding start signal St, FIG. 3B shows the time change of the feeding speed Fw, and FIG. 4C shows the time change of the welding current Iw. Further, the broken line shown in FIG. 3C indicates the welding current setting signal Ir = Ir1. This figure shows a case where one kind of workpieces conveyed one after another are repeatedly welded. Hereinafter, a description will be given with reference to FIG.

  At time t1, the robot RM moves from the standby position to the welding start position and stops, and the welding start signal St becomes High level as shown in FIG. In response to this, the welding wire 1 is fed at a feeding speed Fw corresponding to the feeding speed setting signal Fr = Fr1, as shown in FIG. At the same time, the welding current Iw starts energization as shown in FIG. When the welding current Iw starts energization, a current energization signal Wcr (not shown) is transmitted from the welding power source PS to the robot controller RC, so that the robot RM starts moving along the welding line at a predetermined welding speed. Welding is performed. The feed speed setting signal Fr1 is a value obtained by converting the welding current setting signal Ir1.

  When the robot RM reaches the welding end position at time t2, the robot RM stops, and the welding start signal St becomes low level as shown in FIG. In response to this, as shown in FIG. 5B, feeding of the welding wire 1 is stopped, so that the feeding speed Fw = 0. At the same time, the energization of the welding current Iw is stopped and the welding is finished. When the energization of the welding current Iw is completed, the current energization signal Wcr becomes the low level, and the robot RM moves to the standby position. And the workpiece | work which completed welding is carried out, the next workpiece | work is carried in, and it mounts in a predetermined position. When the placement of the work is determined by a program logic controller (PLC) or the like (not shown in FIG. 5), the robot controller RC is notified. Upon receiving this notification, the robot controller RC moves the robot RM from the standby position to the welding start position and stops it. This time is time t3.

  Here, the period from time t1 to t2 is referred to as a welding period Ta = Ta1, and the period from time t2 to t3 is referred to as a pause period Tb = Tb0. The welding period Ta is a time obtained by dividing the length of the weld line of the workpiece (welding length) by the welding speed. In addition, the pause period Tb is a time required for the robot RM to start moving to the standby position, replace the workpiece, and move again to the welding start position and stop the robot RM. Therefore, the welding period Ta and the rest period Tb are not directly set values.

  A change in the welding current Iw in the welding period Ta1 between times t1 and t2 will be described. As shown in FIG. 6C, the welding current Iw becomes I11 which is substantially equal to the welding current setting signal Ir1 indicated by the broken line immediately after time t1, decreases with time, and becomes I12 at the welding end time t2. The current value I12 is a value slightly smaller than the welding current setting signal Ir1. And the average value of the welding current Iw of the time t1-t2 becomes I1. The reason why the value of the welding current Iw gradually decreases with the passage of time is that the temperature of the welding torch 4 rises due to the energization of the welding current Iw and the heat from the arc. This is because it also rises. When the temperature of the welding wire 1 rises, the welding wire 1 having the same feeding speed can be melted even if the value of the welding current Iw decreases. As a result, when the temperature of the welding torch 4 rises and the temperature of the welding wire 1 rises, the value of the welding current Iw decreases when the feed speed is constant.

  The operation during the welding period from time t3 to t4 is the same as the operation during time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I21 immediately after the start of welding and becomes I22 at the end of welding. The average value of the welding current Iw during this period is I2. Here, since the temperature of the welding torch 4 is further increased than the period from the time t1 to the time t2, I21 <I11, I22 <I12 and I2 <I1. The operation in the pause period from time t4 to t5 is the same as the operation from time t2 to t3 described above, and the movement of the robot RM to the standby position, the workpiece exchange, and the movement of the robot RM to the welding start position are performed. The length of the welding period from time t3 to t4 is Ta1 that is the same as that from time t1 to t2, and the length of the rest period from time t4 to t5 is Tb0 that is the same as from time t2 to t3.

  The operation during the welding period from time t5 to t6 is the same as that during the period from time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I31 immediately after the start of welding and becomes I32 at the end of welding. The average value of the welding current Iw during this period is I3. Here, since the temperature of the welding torch 4 is further increased than the period of time t3 to t4, I31 <I21, I32 <I22 and I3 <I2. The operation in the pause period from time t6 to t7 is the same as the operation from time t2 to t3 described above, and the movement of the robot RM to the standby position, the workpiece exchange, and the movement of the robot RM to the welding start position are performed. The length of the welding period from time t5 to t6 is Ta1 that is the same as that from time t1 to t2, and the length of the rest period from time t6 to t7 is Tb0 that is the same as from time t2 to t3.

  The operation during the welding period from time t7 to t8 is the same as that during the period from time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I41 immediately after the start of welding, and becomes I42 at the end of welding. The average value of the welding current Iw during this period is I4. Here, since the temperature of the welding torch 4 is further increased from the time t5 to t6, I41 <I31, I42 <I32, and I4 <I3. The operation in the pause period from time t8 to t9 is the same as the operation from time t2 to t3 described above, and the movement of the robot RM to the standby position, the workpiece exchange, and the movement of the robot RM to the welding start position are performed. The length of the welding period from time t7 to t8 is Ta1, which is the same as that from time t1 to t2, and the length of the pause period from time t8 to t9 is Tb0, which is the same as from time t2 to t3.

  As described above, when the temperature of the welding torch increases, the value of the welding current Iw decreases. When the value of the welding current Iw changes, the bead penetration, the bead width, etc. change, and uniform welding quality cannot be obtained. In order to deal with this problem, the conventional techniques described below are effective.

  The invention of Patent Document 1 provides an efficient water-cooled welding torch. As the welding torch, there are an air-cooled type and a water-cooled type. The air-cooled welding torch does not perform forced cooling and has a structure of natural air cooling. On the other hand, the water-cooled welding torch has a forced cooling structure in which water flows inside. If a water-cooled welding torch is used as the welding torch, a temperature increase accompanying energization of the welding current Iw can be suppressed, so that a decrease in the welding current Iw can be suppressed and uniform welding quality can be obtained.

  The invention of Patent Document 2 uses a flux-cored wire as the welding wire, supplies a substantially constant welding current to the welding wire, and eliminates the deviation between the welding voltage detection value and the welding voltage setting value. According to the welding method, the feeding speed is increased or decreased to maintain the arc length substantially constant. That is, a constant welding current is applied by constant current control in spite of consumable electrode arc welding. With constant current control, arc length control cannot be performed, so that good welding cannot be performed. For this purpose, the arc length control is performed by increasing or decreasing the feed speed by feedback controlling the deviation between the welding voltage detection value corresponding to the arc length and the welding voltage set value which is the target value. In this welding method, since the value of the welding current Iw does not change even when the temperature of the welding torch rises, uniform welding quality can be obtained.

JP 2002-301572 A Japanese Unexamined Patent Publication No. 2000-668

  In the case of using a water-cooled welding torch, there are the following problems with respect to the problem that the welding quality fluctuates due to a decrease in welding current accompanying the temperature rise of the welding torch. Since the water-cooled welding torch has a structure in which water flows inside, the price is higher than that of the air-cooled welding torch, the use place is limited, and the maintainability is poor. For this reason, the actual condition is that the water-cooled welding torch is not used much except when the welding current has a large current value. Therefore, there is a strong demand to solve the above-described problem by using an air-cooled welding torch that is easy to handle.

  When the welding method of Patent Document 2 is applied to the problem that the welding quality fluctuates due to a decrease in the welding current accompanying the temperature rise of the welding torch, there are the following problems. The welding method of Patent Document 2 uses a flux-cored wire as the welding wire. This is because, in arc welding using a flux-cored wire, the droplets become granular and move continuously without being short-circuited. For this reason, since the speed of fluctuation of the arc length due to disturbance is relatively slow, the fluctuation of the arc length can be suppressed by controlling the feeding speed at a variable speed. However, in general consumable electrode arc welding using a solid wire, the droplets are transferred by short-circuit transfer, globule transfer, or the like, so that the arc length fluctuation speed due to disturbance increases. For this reason, this arc length variation cannot be suppressed by variable speed control of the feeding speed. That is, the welding method of Patent Document 2 cannot be applied to consumable electrode arc welding using a solid wire.

  Therefore, an object of the present invention is to provide an arc welding method that uses an air-cooled welding torch and can maintain uniform welding quality even when the temperature of the welding torch rises.

In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that welding is performed by feeding a welding wire from a welding torch at a feeding speed corresponding to a welding current set value and energizing the welding current during the welding period. In the arc welding method in which welding is stopped by stopping feeding of the welding wire during the pause period, and welding is repeated by repeating these periods.
Detecting the welding current during the welding period, and setting the pause period according to a deviation between the welding current set value and the welding current detection value;
This is an arc welding method characterized by the above.

The invention of claim 2 is characterized in that the welding current detection value is an average value of the welding current during the welding period.
The arc welding method according to claim 1, wherein:

In the invention of claim 3, the welding current detection value is the value of the welding current at the end of the welding period.
The arc welding method according to claim 1, wherein:

The invention of claim 4 is forcibly cooled by blowing air from the outside to the welding torch during the pause period.
It is an arc welding method of any one of Claims 1-3 characterized by the above-mentioned.

The invention of claim 5 is forcibly cooled by immersing the welding torch in a liquid during the idle period.
It is an arc welding method of any one of Claims 1-3 characterized by the above-mentioned.

  According to the present invention, the degree of temperature rise of the welding torch is detected by calculating the deviation between the welding current set value and the welding current detection value (welding current average value, welding current value at the end time), and this deviation Depending on, the length of the rest period is set. For this reason, even if the welding torch is air-cooled, the temperature of the welding torch is lowered to a temperature that does not affect the welding quality, so that uniform welding quality can be obtained. Furthermore, since the idle period is set to the minimum time that does not affect the welding quality, the reduction in production efficiency can be minimized.

It is a block diagram of the welding power supply for enforcing the arc welding method which concerns on Embodiment 1 of this invention. It is a figure which shows an example of a rest period setting function. It is a timing chart of each signal in FIG. It is a block diagram of the welding power supply which concerns on Embodiment 2 of this invention. It is a block diagram of the consumable electrode arc welding apparatus using the robot in a prior art. It is a timing chart of each signal of FIG.

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

[Embodiment 1]
The configuration of the welding apparatus for carrying out the arc welding method according to the first embodiment of the present invention is the same as that shown in FIG. However, the circuit blocks constituting the welding power source PS are different, as shown in FIG. Along with this, a pause period setting signal Tbr is newly added to the interface signal If and transmitted from the welding power source PS to the robot controller RC. Therefore, the interface signal If includes a welding start signal St, a welding current setting signal Ir, and a welding voltage setting signal Vr transmitted from the robot controller RC, and a current conduction signal Wcr transmitted from the welding power source PS and The pause period setting signal Tbr is included.

  FIG. 1 is a block diagram of a welding power source PS for performing the arc welding method according to Embodiment 1 of the present invention. Hereinafter, each circuit 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 such as inverter control in accordance with a drive signal Dv described later, and generates a welding voltage Vw and a welding current for generating the arc 3. Iw is output. Although not shown, the power supply main circuit PM has a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current according to the drive signal Dv, and high frequency alternating current It consists of a high-frequency transformer that steps down to a voltage value suitable for arc welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current.

  The welding wire 1 is fed through the welding torch 4 by a feeding roll 5 coupled to a feeding motor WM, and an arc 3 is generated between the base metal 2 and the welding wire 1.

  The interface circuit IF communicates an interface signal If with the robot controller RC. The interface circuit IF outputs a welding start signal St, a welding current setting signal Ir, and a welding voltage setting signal Vr, and a current conduction signal Wcr and a rest period setting signal Tbr are input.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current energization determination circuit WCR receives the welding current detection signal Id, and when this value is equal to or greater than a predetermined current determination value, determines that the welding current Iw is energized and becomes a high level current energization signal. Wcr is output to the interface circuit IF.

  The voltage error amplification circuit EV amplifies an error between the welding voltage setting signal Vr from the interface circuit IF and the welding voltage detection signal Vd, and outputs a voltage error amplification signal Ev. The drive circuit DV receives the voltage error amplification signal Ev and the welding start signal St from the interface circuit IF, and when the welding start signal St is at a high level, the pulse width modulation control is performed based on the voltage error amplification signal Ev. To output the drive signal Dv. Therefore, the welding voltage Vw is output by constant voltage control when the welding start signal St is at a high level, and the output is stopped when the welding start signal St is at a low level.

  The feeding speed setting circuit FR receives the welding current setting signal Ir from the interface circuit IF as described above, and calculates and outputs a feeding speed setting signal Fr by a predetermined current value / feeding speed conversion function. The feed control circuit FC receives the feed speed setting signal Fr and the welding start signal St from the interface circuit IF, and corresponds to the value of the feed speed setting signal Fr when the welding start signal St is at a high level. A feeding control signal Fc for feeding the welding wire 1 at the feeding speed Fw is output to the feeding motor WM.

  The welding current average value calculation circuit IAV receives the above welding current detection signal Id, calculates an average value for each welding, and outputs a welding current average value signal Iav. The deviation calculation circuit DI calculates a deviation between the welding current setting signal Ir from the interface circuit IF and the welding current average value signal Iav, and outputs a deviation signal ΔI = Ir−Iav. Here, since the welding current Iw decreases as the temperature of the welding torch increases, the deviation signal ΔI ≧ 0. The pause period setting signal TBR receives the deviation signal ΔI, calculates a pause period using a preset pause period setting function described later in FIG. 2, and outputs the pause period setting signal Tbr to the interface circuit IF.

  FIG. 2 is a diagram showing an example of a pause period setting function built in the pause period setting circuit TBR described above. In the figure, the horizontal axis indicates the deviation signal ΔI (A), and the vertical axis indicates the pause period setting signal Tbr (seconds). The function shown in the figure is Tbr = Tb0 when ΔI = 0, and is a straight line with a slope of a rising to the right. Therefore, the equation of the straight line is Tbr = a · ΔI + Tb0. Here, Tb0 is the minimum time required to move the robot to the standby position and change the workpiece during the pause period. That is, the pause period cannot be shorter than this time Tb0. Since the time required to move the robot to the standby position is as short as several hundred ms, it can be substantially ignored. Therefore, the minimum time Tb0 is a time required only to change the workpiece. The temperature rise of the welding torch is indirectly detected by the value of the deviation signal ΔI, and the length of the pause period is determined. In consideration of productivity, the function is set so that the value of the suspension period setting signal Tbr is the minimum time during which the temperature of the welding torch falls to a temperature that does not affect the welding quality. This function is set to an appropriate value by experiment according to the welding conditions such as the type of the welding torch, the material of the welding wire, the diameter, the feeding speed, and the wire protruding length. In the figure, the function is represented as a straight line, but may be a curved line rising to the right or a step shape rising to the right.

  FIG. 3 is a timing chart of each signal of the welding power source described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 3B shows the time change of the feeding speed Fw, and FIG. 4C shows the time change of the welding current Iw. Further, the broken line shown in FIG. 3C indicates the welding current setting signal Ir = Ir1. This figure corresponds to FIG. 6 described above, and shows a case where one kind of workpieces conveyed one after another are repeatedly welded. The following description will be made with reference to the same drawing, focusing on the differences from FIG.

  At time t1, the robot RM moves from the standby position to the welding start position and stops, and the welding start signal St becomes High level as shown in FIG. In response to this, the welding wire 1 is fed at a feeding speed Fw corresponding to the feeding speed setting signal Fr = Fr1, as shown in FIG. At the same time, the welding current Iw starts energization as shown in FIG. When the welding current Iw starts energization, a current energization signal Wcr (not shown) is transmitted from the welding power source PS to the robot controller RC, so that the robot RM starts moving along the welding line at a predetermined welding speed. Welding is performed. The feed speed setting signal Fr1 is a value obtained by converting the welding current setting signal Ir1.

  A change in the welding current Iw in the welding period Ta1 between times t1 and t2 will be described. As shown in FIG. 6C, the welding current Iw becomes I11 which is substantially equal to the welding current setting signal Ir1 indicated by the broken line immediately after time t1, decreases with time, and becomes I12 at the welding end time t2. The current value I12 is a value slightly smaller than the welding current setting signal Ir1. And the average value of the welding current Iw of the time t1-t2 becomes I1. Therefore, the deviation signal ΔI = Ir1−I1 is obtained, and the pause period setting signal Tbr = Tb1 is calculated by the pause period setting function described above with reference to FIG. Here, the value of the pause period setting signal Tb1 is larger than Tb0 in FIG.

  When the robot RM reaches the welding end position at time t2, the robot RM stops, and the welding start signal St becomes low level as shown in FIG. In response to this, as shown in FIG. 5B, feeding of the welding wire 1 is stopped, so that the feeding speed Fw = 0. At the same time, the energization of the welding current Iw is stopped and the welding is finished. When the energization of the welding current Iw is completed, the current energization signal Wcr becomes the low level, and the robot RM moves to the standby position. At the same time, the pause period setting signal Tbr is transmitted from the welding power source PS to the robot controller RC. And the workpiece | work which completed welding is carried out, the next workpiece | work is carried in, and it mounts in a predetermined position. The robot controller RC stops at the standby position until the period determined by the pause period setting signal Tbr elapses after the current energization signal Wcr becomes the Low level (time t2). When the set pause period elapses, the robot controller RC moves the robot RM from the standby position to the welding start position and stops it. This time is time t3. Therefore, strictly speaking, when a period determined by the suspension period setting signal Tbr elapses from time t2, the robot RM starts moving to the welding start position. However, since the time required for the robot RM to move from the standby position to the welding start position is short, the period from time t2 to t3 can be regarded as the period Tb1 determined by the pause period setting signal Tbr.

  As described above, when the temperature of the welding torch 4 rises and the welding current Iw decreases, the rest period is lengthened according to the reduction width (deviation signal ΔI), and the temperature of the welding torch 4 decreases. .

  The operation during the welding period from time t3 to t4 is the same as the operation during time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I11 immediately after the start of welding, and becomes I12 at the end of welding, similarly to the times t1 to t2. The average value of the welding current Iw during this period is I1. Therefore, the value of the deviation signal ΔI is Ir1−I1 similarly to the period from the time t1 to the time t2, and the value of the pause period setting signal Tbr is also Tb1. The operation during the suspension period from time t4 to t5 is the same as the operation from time t2 to t3 described above, and the current energization signal Wcr = Low level and the suspension period setting signal Tbr are transmitted to the robot controller RC. Then, the robot RM is moved to the standby position, the workpiece is exchanged, and the robot RM is moved to the welding start position. The length of the welding period from time t3 to t4 is Ta1 that is the same as that from time t1 to t2, and the length of the rest period from time t4 to t5 is Tb1 that is the same as from time t2 to t3.

  The operation during the welding period from time t5 to t6 is the same as that during the period from time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I11 immediately after the start of welding, and becomes I12 at the end of welding, similarly to the times t1 to t2. The average value of the welding current Iw during this period is I1. Therefore, the value of the deviation signal ΔI is Ir1−I1 similarly to the period from the time t1 to the time t2, and the value of the pause period setting signal Tbr is also Tb1. The operation in the suspension period from time t6 to t7 is the same as the operation in time t2 to t3 described above, and the current energization signal Wcr = Low level and the suspension period setting signal Tbr are transmitted to the robot controller RC. Then, the robot RM is moved to the standby position, the workpiece is exchanged, and the robot RM is moved to the welding start position. The length of the welding period from time t5 to t6 is Ta1 which is the same as that from time t1 to t2, and the length of the rest period from time t6 to t7 is Tb1 which is the same as from time t2 to t3.

  The operation during the welding period from time t7 to t8 is the same as that during the period from time t1 to t2 described above. That is, as shown in FIG. 9A, the welding start signal St is at a high level during this period. Further, as shown in FIG. 7B, the feeding speed Fw during this period is a value corresponding to the feeding speed setting signal Fr1. Further, as shown in FIG. 5C, the welding current Iw gradually decreases from I11 immediately after the start of welding, and becomes I12 at the end of welding, similarly to the times t1 to t2. The average value of the welding current Iw during this period is I1. Therefore, the value of the deviation signal ΔI is Ir1−I1 similarly to the period from the time t1 to the time t2, and the value of the pause period setting signal Tbr is also Tb1. The operation in the suspension period from time t8 to t9 is the same as the operation in time t2 to t3 described above, and the current energization signal Wcr = Low level and the suspension period setting signal Tbr are transmitted to the robot controller RC. Then, the robot RM is moved to the standby position, the workpiece is exchanged, and the robot RM is moved to the welding start position. The length of the welding period from time t7 to t8 is the same Ta1 as that from time t1 to t2, and the length of the pause period from time t8 to t9 is the same Tb1 as from time t2 to t3.

  According to the first embodiment described above, the degree of temperature rise of the welding torch is detected by calculating the deviation between the welding current set value and the welding current detection value (welding current average value), and according to this deviation, Sets the length of the pause period. For this reason, even if the welding torch is air-cooled, the temperature of the welding torch is lowered to a temperature that does not affect the welding quality, so that uniform welding quality can be obtained. Furthermore, since the idle period is set to the minimum time that does not affect the welding quality, the reduction in production efficiency can be minimized.

[Embodiment 2]
The second embodiment of the present invention differs from the first embodiment described above in the method of calculating the deviation signal ΔI. That is, in the first embodiment, the deviation signal ΔI is calculated by subtracting the welding current setting signal Ir and the welding current average value signal Iav. On the other hand, in Embodiment 2, instead of the welding current average value signal Iav, a welding current value at the end of each welding period (end time welding current value signal Ie) is used. Therefore, in the second embodiment, the deviation signal ΔI = Ir−Ie. Hereinafter, the second embodiment will be described with reference to the drawings.

  FIG. 4 is a block diagram of a welding power source for carrying out the arc welding method 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 as those in FIG. 1 and their description is omitted. In the figure, the welding current average value calculation circuit IAV in FIG. 1 is replaced with an end-point welding current value detection circuit IE indicated by a broken line, and the deviation calculation circuit DI in FIG. 1 is replaced by a second deviation calculation circuit DI2 indicated by a broken line. Is. Hereinafter, these blocks will be described with reference to the drawings.

  The end point welding current value detection circuit IE receives the welding current detection signal Id, detects the welding current value at the end point of each welding period, and outputs the end point welding current value signal Ie. The second deviation calculating circuit DI2 calculates a deviation between the welding current setting signal Ir and the welding current value signal Ie at the end time, and outputs a deviation signal ΔI = Ir−Ie. Here, since the welding current Iw decreases as the temperature of the welding torch increases, the deviation signal ΔI ≧ 0.

  2 and FIG. 3 in the first embodiment are substantially adapted to the second embodiment as they are, and their description is omitted. The effect of the second embodiment is the same as that of the first embodiment.

[Embodiment 3]
In the third embodiment of the present invention, in addition to the first and second embodiments described above, a step of forcibly cooling the welding torch from the outside during the idle period is provided. For this reason, the description of the first and second embodiments can be applied to the third embodiment as it is. Therefore, the added steps will be described below.

  As shown in FIG. 3A, when the welding start signal St becomes a low level at the time t2 in FIG. 3 described above, the feeding of the welding wire is stopped as shown in FIG. As shown in (C), energization of the welding current Iw is stopped. For this reason, the current energization signal Wcr becomes the Low level and is notified from the welding power source PS to the robot controller RC. When receiving this notification, the robot controller RC moves the robot RM to the cooling position, unlike the first and second embodiments. In this cooling position, the welding torch is forcibly cooled by blowing air from a blower. As another cooling method, forced cooling may be performed by immersing the tip (nozzle portion) of the welding torch in a liquid that does not adversely affect the welding, such as a spatter adhesion preventing liquid. During this cooling, the workpiece is exchanged. Then, when the pause period set from time t2 has elapsed, the robot controller RC moves the robot RM to the welding start position and stops it.

  In the third embodiment, since the welding torch is forcibly cooled during the rest period, the temperature decrease rate is increased. Therefore, it is necessary to change the suspension period setting function of FIG. 2 described above so as to be adapted to the forced cooling. That is, the value of the pause period setting signal Tbr with respect to the value of the deviation signal ΔI is smaller than those in the first and second embodiments.

  According to the above-described third embodiment, the welding torch is forcibly cooled from the outside during the pause period, so that the temperature drop of the welding torch can be speeded up. For this reason, since the suspension period can be shortened, production efficiency can be increased in addition to the effects of the first and second embodiments.

  In the first to third embodiments described above, the case where one type of workpiece is repeatedly welded is illustrated, but the present invention can also be applied to cases where there are a plurality of welding locations in one workpiece. It can also be applied to a case where a plurality of workpieces are mixed and welded.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 4a Conduit cable 5 Feed roll DI Deviation calculation circuit DI2 2nd deviation calculation circuit DV Drive circuit Dv Drive signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feeding control signal FR Feeding speed setting circuit Fr Feeding speed setting signal Fw Feeding speed IAV Welding current average value calculation circuit Iav Welding current average value signal ID Current detection circuit Id Welding current detection signal IE Ending welding current value detection circuit Ie End welding current value signal IF Interface circuit If Interface signal Ir Welding current setting signal Iw Welding current Mc Operation control signal PM Power supply main circuit PS Welding power supply RC Robot controller RM Robot St Welding start signal Ta Welding period Tb Rest period TBR Rest Period setting circuit Tbr Pause period setting signal TP Te Over Chi Pendant VD voltage detection circuit Vd welding voltage detection signal Vr welding voltage setting signal Vw welding voltage WCR current application discriminating circuit Wcr current energization signal WM feed motor ΔI deviation signal

Claims (5)

During the welding period, welding is performed by feeding the welding wire from the welding torch at a feeding speed corresponding to the welding current set value and energizing the welding current, and during the pause period, the welding wire is stopped and welding is performed. In the arc welding method that pauses and repeats these periods for welding,
Detecting the welding current during the welding period, and setting the pause period according to a deviation between the welding current set value and the welding current detection value;
An arc welding method characterized by that. The welding current detection value is an average value of the welding current during the welding period.
The arc welding method according to claim 1. The welding current detection value is the value of the welding current at the end of the welding period.
The arc welding method according to claim 1. During the suspension period, forced cooling is performed by blowing air from the outside to the welding torch.
The arc welding method according to any one of claims 1 to 3. During the rest period, forced cooling by immersing the welding torch in a liquid,
The arc welding method according to any one of claims 1 to 3.

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