JP2009178763A - Output control method of welding power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve weld quality by electronically forming desirable external characteristics and required inductance values in a consumable electrode arc welding power source. <P>SOLUTION: An external characteristic function circuit ERF, containing a plurality of the external characteristics, takes a welding current detection signal id as an input and outputs an output voltage setting signal Er of welding power source. An inductance setting circuit LR outputs an inductance setting signal Lr to setup a proper inductance value for the welding power source. A current setting variance calculation circuit DIR calculates a current setting variance signal ΔIr=(Er-vd)/Lr by taking the output voltage setting signal Er, a welding voltage detection signal vd and the inductance setting signal Lr as inputs. A current setting integration circuit IIR calculates a welding current control setting signal Irc by integrating the current setting variance signal ΔIr. Output control of the welding current i is carried out based on the welding current control setting signal Irc. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an output control method for a welding power source capable of setting a proper inductance value and a proper external characteristic to desired values in the welding power source.

  FIG. 4 is a configuration diagram of a general consumable electrode arc welding apparatus. The welding power source PS is output-controlled so that the external characteristic becomes a constant voltage characteristic, and outputs a welding voltage v and a welding current i suitable for welding. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the wire feeding motor WM, and is also fed with power via the power feed tip 4a to the base material 2. Arc 3 is generated.

FIG. 5 is a diagram illustrating an example of external characteristics of the above-described welding power source. In the figure, the horizontal axis represents the welding current i, and the vertical axis represents the welding voltage v. This figure shows the case of constant voltage characteristics used for general consumable electrode arc welding. In the figure, when i = 0, v = E, and if the slope of the external characteristic is −Rm, the external characteristic is expressed by the following equation.
v = E−Rm · i

  Since the stability of the welding state depends on the external characteristics, a technology has been developed to form optimal external characteristics by electronic control according to welding conditions such as the welding method, base material, and wire feed speed. (For example, refer to Patent Documents 1 and 2).

  FIG. 6 is a typical voltage / current waveform diagram of consumable electrode arc welding. FIG. 4A shows the welding voltage v, and FIG. 4B shows the welding current i. This figure shows the case of short-circuit transfer welding in which the short-circuit period Ts and the arc period Ta are alternately repeated. During the short circuit period Ts from time t1 to t2, the welding wire and the base material are in a short circuit state, and the welding voltage v is a low value as shown in FIG. The welding current i gradually increases. During the arc period Ta from time t2 to t3, the arc is generated between the welding wire and the base metal, and the welding voltage v increases to the arc voltage as shown in FIG. ), The welding current i gradually decreases. The increase and decrease rates of the welding current i are determined by the inductance value of the current conducting path and the welding load. The inductance value is a total value of the inductance value of the reactor provided inside the welding power source and the inductance generated by the routing of the welding cable. An appropriate increase and decrease rate of the welding current i is one of the important factors for obtaining a stable welding state. Since an appropriate increase and decrease rate of the welding current i differs depending on welding conditions such as a welding method, a base material, and a wire feeding speed, it is necessary to set an optimum inductance value according to the welding conditions.

  Although the reactor is manufactured by winding a cable around an iron core, it is difficult to change the inductance value because of its structure. For this reason, a technique for forming a reactor by electronic control has been developed (see, for example, Patent Document 3). In this electronic reactor control method, it is possible to form an optimum inductance value according to the welding conditions. Hereinafter, this prior art will be described.

  FIG. 7A is an equivalent circuit diagram of the welding power source PS. E represents a constant voltage source, Lm represents an appropriate inductance value, and Rm represents an appropriate resistance value. The resistance value is the sum of the wiring resistance value inside the welding power source and the resistance value of the welding cable, and this value determines the slope of the external characteristics.

The equivalent circuit of the figure can be expressed by the following equation.
E = Rm · i + Lm · di / dt + v (1) In this equation, the relationship between the welding voltage v and the welding current i when the current change di / dt = 0 is an external characteristic. Substituting di / dt = 0 into the above equation yields the following equation.
v = E−Rm · i
The above equation represents the external characteristics described above with reference to FIG.
When the above equation (1) is arranged, the following equation is obtained.
di / dt = (E−V−Rm · i) / Lm
Integrating both sides gives the following formula.
i = ∫ ((E−V−Rm · i) / Lm) · dt
Here, the welding current i is set to the welding current control set value Irc, the output voltage E is set to the output voltage set value Er, the appropriate external characteristic slope Rm is set to the external characteristic slope set value Rr, and the appropriate inductance value Lm is set to the inductance set value Lr. When each is replaced, the following formula is obtained.
Irc = ∫ ((Er−v−Rr · i) / Lr) · dt (2) Equation An equivalent circuit corresponding to this equation is shown in FIG. In the figure, the welding voltage v and the welding current i are detected, and the welding current control set value Irc corresponding to the welding current i of the constant current source CC is controlled to be the calculated value of the above equation (2).

  By performing the above-described control, it is possible to electronically form a desired inductance value Lr and a desired external characteristic slope -Rr.

JP-A-6-170538 JP-A-7-1130 JP 2003-305571 A

  In the prior art, the desired inductance value Lr and the slope -Rr of the external characteristic can be electronically formed, so that the welding state can be stabilized. However, the external characteristic that can be formed by this prior art is only in the case of a straight line with a downward slope where Rr> 0 and the slope −Rr <0.

  In order to further improve the welding quality such as the reduction of the amount of spatter generated and the improvement of the bead appearance, it is necessary to form the external characteristic L1 of the broken line as shown in FIG. The external characteristic L1 shown in the figure has a downward-sloping drooping characteristic when i ≦ It1 and an upward-rising characteristic when It1> i. It is necessary to form the external characteristic L1 of such a broken line and to form a desired inductance value Lr.

  Accordingly, an object of the present invention is to provide an output control method for a welding power source capable of electronically forming external characteristics of a broken line and a desired inductance value simultaneously.

In order to solve the above-described problem, the first invention
An external characteristic function that outputs the welding power supply output voltage setting value Er with the welding current detection value id as an input is set in advance, and an inductance setting value Lr that sets an appropriate inductance value for the welding power supply is set in advance.
The welding current and welding voltage during welding are detected, the welding current detection value id is input, the output voltage setting value Er is calculated by the external characteristic function, the output voltage setting value Er, the welding voltage detection value vd, and The inductance setting value Lr is used as an input to calculate a current setting change amount ΔIr = (Er−vd) / Lr. The current setting change amount ΔIr is integrated to calculate a welding current control setting value, and the welding current detection value id is calculated. To control the output so that is substantially equal to the welding current control set value,
This is an output control method for a welding power source.

2nd invention sets the said external characteristic function as a function which is different when a welding state is a short circuit state, and an arc generation state,
An output control method for a welding power source according to the first aspect of the invention.

3rd invention sets the said external characteristic function as a function which changes with wire feeding speeds,
An output control method for a welding power source according to the first or second aspect of the invention.

  According to the first aspect of the invention, it is possible to form a desired external characteristic of a broken line and form a desired inductance value. For this reason, an external characteristic and an inductance value can be optimized according to welding conditions, and the stability of a welding state can be improved. The external characteristics that can be formed are a constant voltage characteristic, a rising characteristic, a drooping characteristic, and a combination of these characteristics.

  According to the second aspect of the present invention, it is possible to form optimum external characteristics that are different between the short circuit state and the arc generation state. At the same time, a desired inductance value can be formed. For this reason, since external characteristics and an inductance value can be optimized according to various welding conditions, welding quality can be further improved.

  According to the third aspect, the external characteristics can be optimized according to the wire feed speed. At the same time, a desired inductance value can be formed. For this reason, since external characteristics and an inductance value can be optimized according to various welding conditions, welding quality can be further improved.

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

[Embodiment 1]
A basic arithmetic expression for the output control method of the welding power source according to the present invention will be described below. The above-described equation (2) is established among the output voltage setting value Er, the inductance setting value Lr, the external characteristic inclination setting value Rr, the welding current i, the welding voltage v, and the welding current control setting value Irc.
Irc = ∫ ((Er−v−Rr · i) / Lr) · dt
Here, (Er−Rr · i) represents the external characteristic as described above. Therefore, when this is expanded and replaced with the function Er (i), the following equation is obtained.
Irc = ∫ ((Er (i) −v) / Lr) · dt (3) This equation is the basic equation of the present invention.

FIG. 1 is a diagram illustrating an example of an external characteristic function Er (i) indicated by a broken line. In the figure, the horizontal axis represents the welding current i, and the vertical axis represents the output voltage set value Er. The external characteristic function of this broken line can be expressed by the following equation.
i ≦ It1 Er = a11 · i + b11 (4) Formula It1 <i Er = a12 · i + b12 (5) where a11, b11, a12 and b12 are constants. The inclination a11 <0 and the inclination a12> 0. Therefore, equation (4) represents the drooping characteristic and equation (5) represents the ascending characteristic. Hereinafter, the output control method of the present invention based on the equations (3) to (5) will be described.

As shown in the figure, when the welding current at an arbitrary time point during welding is i = i1, since It1 ≦ i1, the output voltage set value Er is calculated as follows by the above equation (5). .
Er = a12 · i1 + b12
This value is substituted into the above equation (3) and integrated every moment to calculate the welding current control set value Irc. Then, the output of the welding power source is controlled so that the welding current i becomes substantially equal to the welding current control set value Irc.

  FIG. 2 is a block diagram of a welding power source for carrying out the output control method 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 such as a three-phase 200 V input, performs output control such as inverter control according to an error amplification signal Ei described later, and outputs an output voltage E and a welding current i. This power supply main circuit PM includes a primary rectifier for rectifying commercial power, a smoothing capacitor for smoothing the rectified direct current, an inverter circuit for converting the smoothed direct current to high frequency alternating current, and stepping down the high frequency alternating current to a voltage value suitable for welding. High-frequency transformer, secondary rectifier that rectifies the stepped-down high-frequency alternating current to direct current, modulation circuit that performs pulse width modulation control using error amplification signal Ei as input, and switching element of inverter circuit that receives pulse width modulation control signal as input Drive circuit. In the energization path of the welding current i, there are a resistance value Rio and an inductance value Lio due to the reactor DCL. The resistance value Rio is a resistance value due to wiring inside and outside the welding power source. The inductance value Lio is an inductance value obtained by adding up the reactor provided inside the welding power source and the reactor due to the routing of the welding cable. Usually, the resistance value Rio is about 0.01 to 0.05Ω, and the inductance value Lio is about 20 to 50 μH.

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

  The current detection circuit ID detects the welding current i and outputs a current detection signal id. The voltage detection circuit VD detects the welding voltage v and outputs a voltage detection signal vd. The external characteristic function circuit ERF includes an external characteristic function (for example, the above-described equations (4) to (5)), and outputs the output voltage setting signal Er with the current detection signal id as an input.

  The inductance setting circuit LR outputs a predetermined inductance setting signal Lr. The current setting change amount calculation circuit DIR receives the output voltage setting signal Er, the inductance setting signal Lr, and the voltage detection signal vd as inputs, and calculates a current setting change amount signal ΔIr = (Er−v) / Lr. To do. The current setting integration circuit IIR integrates the current setting change amount signal ΔIr and outputs a welding current control setting signal Irc. The above equation (3) is calculated by the current setting change amount calculation circuit DIR and the current setting integration circuit IIR.

  The current error amplification circuit EI amplifies an error between the welding current control setting signal Irc and the current detection signal id and outputs an error amplification signal Ei.

  With the above configuration, the external characteristics shown in FIG. 1 can be formed. At this time, even if the length of the welding cable is changed and the resistance value Rio is changed, the formed external characteristics are not affected. At the same time, with the above configuration, the inductance value set by the inductance setting signal Lr can be set. At this time, even if the routing of the welding cable changes and the inductance value Lio changes, the inductance value of the energization path that is set is controlled to be equal to the set value Lr.

  According to the first embodiment described above, it is possible to form a desired external characteristic of a broken line and to form a desired inductance value. For this reason, an external characteristic and an inductance value can be optimized according to welding conditions, and the stability of a welding state can be improved. The external characteristics that can be formed are a constant voltage characteristic, a rising characteristic, a drooping characteristic, and a combination of these characteristics.

[Embodiment 2]
FIG. 3 is a diagram showing an external characteristic function according to the second embodiment of the present invention. In the figure, the horizontal axis indicates the welding current i, and the vertical axis indicates the output voltage set value Er. This figure corresponds to FIG. 1 described above, and the external characteristic L1 is the same. Hereinafter, a description will be given with reference to FIG.

The figure is composed of three external characteristics L1 to L3. The function of the external characteristic L1 is the above-described equations (4) and (5). The external characteristic L2 is the following function.
i ≦ It1 Er = a21 · i + b21
It1 <i ≦ It2 Er = a22 · i + b22
It2 <i Er = a23 · i + b23
The external characteristic L3 can be expressed by the following equation.
i ≦ It1 Er = a31 · i + b31
It1 <i Er = a32 · i + b32

  The external characteristic L1 is selected when the welding state is an arc generation state and the wire feed speed is equal to or less than a reference value. The external characteristic L2 is selected when the welding state is a short circuit state. The external characteristic L3 is selected when the welding state is an arc generation state and the wire feed speed exceeds the reference value. Thus, welding quality can be further improved by forming a plurality of external characteristics according to the welding state and welding conditions. As welding states other than those described above, there are an elapsed time in a short circuit state, an elapsed time in an arc generation state, an occurrence of welding abnormality, and the like. Further, welding conditions other than the above include a welding method, a base material, a type of welding wire, and the like. A plurality of external characteristics are optimized according to these welding states and welding conditions, and a plurality of external characteristics are stored, and the optimum external characteristics are selected from these.

  The block diagram of the welding power source for carrying out the present embodiment is obtained by changing the external characteristic function circuit ERF in FIG. 2 described above as follows. The external characteristic function circuit ERF in the present embodiment incorporates a plurality of external characteristic functions as shown in FIG. 3, and is selected from the external characteristics L1 to L3 by a short circuit / arc discrimination signal and a wire feed speed signal. One is selected. The operation of other blocks is the same as in FIG.

  According to the second embodiment described above, it is possible to form optimum external characteristics that are different between the short circuit state and the arc generation state. Further, different external characteristics can be formed according to the wire feed speed. At this time, a desired inductance value can be formed at the same time. For this reason, since external characteristics and an inductance value can be optimized according to various welding conditions, welding quality can be further improved.

  The present invention can be applied to carbon dioxide arc welding, MIG welding, mag welding, AC consumable electrode arc welding, and the like.

It is a figure which shows the external characteristic which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for enforcing the output control method concerning Embodiment 1 of the present invention. It is a figure which shows the external characteristic which concerns on Embodiment 2 of this invention. It is a block diagram of a general consumable electrode arc welding apparatus. It is a figure which shows the external characteristic in a prior art. It is a voltage and current waveform diagram of consumable electrode arc welding. It is an equivalent circuit diagram for demonstrating the output control method of the welding power supply in a prior art. It is an external characteristic figure for demonstrating a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 4a Feed tip 5 Feed roll CC Constant current source DCL Reactor DIR Current setting change amount calculation circuit E Output voltage EI Current error amplification circuit Ei Error amplification signal Er Output voltage setting (value / signal)
ERF external characteristic function circuit i welding current ID current detection circuit id current detection signal IIR current setting integration circuit Irc welding current control setting (value / signal)
L1 to L3 External characteristic Lio Inductance value Lm Proper inductance value LR Inductance setting circuit Lr Inductance setting (value / signal)
PM power supply main circuit PS welding power supply Rio resistance value Rr external characteristic inclination setting value Ta arc period Ts short circuit period v welding voltage VD voltage detection circuit vd voltage detection signal WM wire feed motor ΔIr current setting change amount (signal)

Claims (3)

An external characteristic function that outputs the welding power supply output voltage setting value Er with the welding current detection value id as an input is set in advance, and an inductance setting value Lr that sets an appropriate inductance value for the welding power supply is set in advance.
The welding current and welding voltage during welding are detected, the welding current detection value id is input, the output voltage setting value Er is calculated by the external characteristic function, the output voltage setting value Er, the welding voltage detection value vd, and The inductance setting value Lr is used as an input to calculate a current setting change amount ΔIr = (Er−vd) / Lr. The current setting change amount ΔIr is integrated to calculate a welding current control setting value, and the welding current detection value id is calculated. To control the output so that is substantially equal to the welding current control set value,
An output control method for a welding power source. The external characteristic function is set as a different function between when the welding state is a short circuit state and when the arc is generated.
The output control method for a welding power source according to claim 1. The external characteristic function is set as a function that varies depending on the wire feed speed.
The output control method for a welding power source according to claim 1 or 2.

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