JP3215567B2 - Power control method and apparatus for consumable electrode type gas shielded arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the output of gas-shielded arc welding using consumable electrodes.

[0002]

_2. Description of the Related Art CO ₂ or Ar is used as a shielding gas.
In consumable electrode type gas shielded arc welding using a mixed gas of Ar and CO ₂ (a so-called mag gas) whose main component is a welding current value is selected according to the working conditions and the shape of the work. Incidentally, in order to obtain a good welding result, it is necessary to set the output voltage of the welding machine so as to obtain an appropriate arc voltage according to the welding current value. However, an appropriate arc voltage depends not only on the welding current value but also on the working environment and form. Therefore, for the selected welding current value,
Setting the output voltage of the welding machine so as to obtain an appropriate arc voltage requires considerable skill and skill improvement, and is not something that a beginner can easily learn. Therefore,
In order that even a beginner can obtain a welding result equivalent to that of a skilled person, Japanese Patent Application Laid-Open No. 56-158281
(Hereinafter referred to as the prior art) discloses a technique in which a relation between a welding current and an appropriate output voltage is stored in a database in advance, and when a welding current is selected, an output voltage of a welding machine is unitarily set. ing. Also, Japanese Patent Application Laid-Open No. Sho 60-1283
Japanese Patent Publication No. 40 (hereinafter referred to as a second prior art) and Japanese Patent Application Laid-Open No. Sho 60-162577 (hereinafter referred to as a third prior art) disclose observation results of current and voltage waveforms during welding by a predetermined function. There is disclosed a technique of calculating and setting an output voltage so that the calculated value is minimized. ◆ By the way, when welding large structures, for example, the welding cable is often extended. In this case, in order to obtain an appropriate arc voltage, it is necessary to increase the output voltage of the welding machine and correct the effect of the voltage drop generated in the extended welding cable. However, in the case of the first prior art, the output voltage automatically set as an appropriate arc voltage is selected as data under a predetermined reference condition and a standard work environment, and therefore, the output voltage is determined based on the standard work environment. If not, the value will not be correct. An appropriate value can be obtained by arranging a detection line for detecting the arc voltage to the welded portion, but the operability is reduced when the number of wires increases. Further, the data selected as data is selected by a specific skilled welding worker, and is not necessarily an unbiased appropriate value. Further, in the case of the second and third prior arts, it is possible to correct the voltage drop when using the extension cable, but in order to minimize the value calculated by the predetermined function, the output voltage must be manipulated. Therefore, it is necessary to obtain at least three calculated values, and it takes time to obtain an appropriate arc voltage. In order to solve the above-mentioned problem, the applicant of the present application disclosed in Japanese Patent Application No. 4-128570 (hereinafter, referred to as a fourth prior art) a small current region and an intermediate current region having relatively small currents. The values of the standard deviations sTs and sTa of the short circuit period and the arc period measured during
Further, the output voltage operation amount is taken as a consequent part, and the output control method of the consumable electrode type gas shielded arc welding is configured to determine the increase or decrease operation amount of the output voltage setting by executing fuzzy inference according to a predetermined control rule. Suggested. In a large current region, Japanese Patent Application No. 5-179673 (hereinafter referred to as a fifth prior art) describes a standard deviation sTa of an arc period measured during welding and a value of an average value mTa thereof in an antecedent part. By performing the fuzzy inference, the output control method of the consumable electrode type gas shielded arc welding that determines the amount of increase / decrease of the output voltage setting was proposed.

[0003]

The above-mentioned fourth and fifth prior arts are effective when CO ₂ is used as a shielding gas. Since the transfer form of the molten metal (hereinafter, referred to as a droplet) to the base material slightly changes, the fourth and fifth prior arts cannot be directly applied. FIG. 12 is an example showing a change in the standard deviation sTa of the arc period with respect to the arc voltage in welding using CO ₂ as a shielding gas.
The change amount of Ta is relatively large. However, Ar + 20% C
In the welding using O ₂ as a shielding gas, as shown in FIG. 13, since the variation of sTa is smaller than that in the case of FIG. 12, the fuzzy inference using the standard deviation sTa of the arc period in the antecedent is good. Results cannot be obtained. The object of the present invention is to solve the above-mentioned problems and to solve the problem of A containing Ar as a main component.
An object of the present invention is to provide a consumable gas shielded arc welding control method capable of automatically setting an appropriate arc voltage in welding using an r + CO ₂ mixed gas as a shielding gas (hereinafter referred to as “mag welding”) and improving workability. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power control method for consumable gas shielded arc welding in which a wire is fed at a substantially constant speed in mag welding and welding is performed while repeating a short circuit and an arc. The standard deviation sTs of the short-circuit period and the average value mTa of the arc period measured as the antecedent part, and the manipulated variable of the output voltage as the consequent part, execute fuzzy inference according to a predetermined control rule, and set the output voltage. The problem is solved by determining the increase / decrease operation amount.

[0005]

In a welding apparatus whose external characteristics are constant voltage characteristics, a welding power source is used while maintaining a wire feed speed, that is, a welding current at a constant value, by using a mixed gas of Ar + CO ₂ containing Ar as a main component as a shielding gas. 2 and 3, the standard deviation sTs of the short-circuit period with respect to the arc voltage and the average value mTa of the arc period greatly change as shown in FIGS. Therefore,
The short circuit period and the arc period were measured, and the standard deviation sTs of the short circuit period calculated from the results and the average value of the arc period
If the value of mTa is processed based on a predetermined membership function and a fuzzy inference rule, and an operation amount for obtaining an appropriate arc voltage is calculated to increase or decrease the output voltage, an appropriate output voltage can always be maintained.

[0006]

FIG. 1 is a structural example of a welding apparatus for carrying out the present invention. In the figure, reference numeral 1 denotes an input-side rectifier for converting commercial AC to DC, and 2 denotes a power semiconductor element, which is an inverter circuit configured to convert the DC to a high-frequency AC. Reference numeral 3 denotes a welding transformer whose input side is connected to the inverter circuit 2. Reference numeral 4 denotes an output-side rectifier connected to the output side of the welding transformer 3, which converts the high-frequency AC generated by the inverter circuit 2 into DC again. A DC reactor 5 smoothes the DC output rectified by the output rectifier 4. Reference numeral 6 denotes a wire, which is supplied to a welding portion by a wire feeding device 7. 8 is the base material. 9 is a welding current setting device,
This is for setting the feeding speed of the wire 6. Note that the inverter circuit 2 is controlled so that the external characteristics become constant voltage characteristics. ◆ 10 is an output voltage setter is used for setting the output voltage V _0. Reference numeral 11 denotes an addition / subtraction circuit, which includes an output voltage V ₀ set by the output voltage setting device 10,
An operation amount ΔV of an output voltage output from a fuzzy controller 22 described later is synthesized, and the result is combined with a new output voltage V _0.
And outputs it to the pulse width control circuit 12. The pulse width control circuit 12 controls the output of the inverter circuit 2 via the drive circuit 13 based on the signal from the addition / subtraction circuit 11. ◆ 14 is a voltage detector. 15 is a voltage detector 1
4. Sampling condition setting device. 16 is a judgment voltage setting device.
Reference numeral 17 denotes a judgment unit for judging whether a short circuit or an arc occurs. According to the sampling interval and sampling time set by the sampling condition setting unit 15, the welding voltage 計 測 measured by the voltage detector 14 and the judgment voltage setting unit 16 are set. The magnitude of the judgment voltage Vj is compared. Then, the determiner 17 determines that υ ≦
When Vj, a short-circuit period determination signal is output to the Ts measuring device 18, and when υ> Vj, an arc period determining signal is output to the Ta measuring device 19, respectively.
The Ts measuring device 18 and the Ta measuring device 19 calculate the standard deviation sTs of the short-circuit period at each short-circuit cycle in which the short circuit and the arc are alternately repeated. 20 and the average value mTa of the arc period are input to a calculator 21. The computing unit 20 uses the output of the Ts measuring unit 18 to calculate the total sum of TsΣTs and the sum of squaresΣTs
The calculation of s ² and the counting of the number N of Ts are performed, the value of the standard deviation sTs is calculated by the following equation 1, and the value is output to the fuzzy controller 22. The arithmetic unit 21 calculates the total sum of Ta, Ta, and counts the number N of Ta using the output of the Ta measuring device 19, calculates the value of the average value mTa from the following equation 2, and calculates the value of the average value mTa by fuzzy. Controller 2
Output to 2. ◆

[0007]

(Equation 1)

The setter 23 has a membership function of a standard deviation sTs and an average value mTa, which are factors constituting the antecedent part of fuzzy inference, and a factor △ V (output voltage manipulated variable) which constitutes a consequent part, and their membership functions. This is for inputting fuzzy inference rules for factors. Then, based on the membership function and the inference rule set by the setting unit 23, the fuzzy controller 22 obtains the degree of conformity of the input standard deviation sTs and the average value mTa to the inference rule, and matches the degree of conformity. The inference result is calculated for each rule. Then, the inference results obtained for each of the inference rules are integrated by the centroid method, the inference result ΔV as a whole is obtained, and output to the addition / subtraction circuit 11.

Hereinafter, the inference method in the fuzzy controller 22 will be described in more detail. ◆ (1) When the transfer form of the droplet to the base material is short-circuit transfer. ◆ When the transfer form of the droplet is short-circuit transfer, the wire feeding speed is relatively slow and the welding current is small. Then, the standard deviation sTs and the average value mTa at this time change as shown in FIGS. 2 and 3, respectively, according to the arc voltage. Therefore, the membership functions of the standard deviation sTs, the average value mTa, and the manipulated variable ΔV of the output voltage are determined as shown in FIGS. 4 to 6, respectively, and a total of 15 inference rules shown in Table 1 are set. ◆

[0010]

[Table 1]

Next, among the inference rules in Table 1, R
1, R2 and R3 will be described below as typical examples. The symbols in parentheses are shown in Table 1. ◆ R1: If sTs is small (S) and mTa is slightly small (SM), the output voltage is not changed (ΔV = Z
0) ◆ R2; If sTs is small (S) and mTa is extremely large (BB), the output voltage is greatly reduced (△ V
= NB) ◆ R3; If sTs is large (B) and mTa is slightly large (MB), the output voltage is greatly increased (△ V =
PB) ◆ That is, the output voltage V ₀ set by the output voltage setting device 10
2 and 3 are too low for the proper voltage.
As shown in the above, since the value of sTs is large and the value of mTa is slightly large, the inference result that the above inference rule R3 is applied to greatly increase the output voltage (ΔV = PB)
Get. If the output voltage V ₀ set by the output voltage setting device 10 is appropriate, the value of sTs is small and mT
Since the value of a is slightly smaller, the above inference rule R1 is applied, and the inference result (△ V
= Z0). ◆ Further, when the output voltage V ₀ set by the output voltage setting device 10 is too high with respect to the appropriate voltage, s
Since the value of Ts is small and the value of mTa is extremely large, the above-mentioned inference rule R2 is applied, and an inference result (ΔV = NB) that the output voltage is greatly reduced is obtained. In the other cases, similarly to the cases of R1, R2, and R3, when the set value of the output voltage is lower than the appropriate voltage, the amount of increase in the output voltage according to the deviation from the appropriate voltage is reduced. When the set value of the output voltage is higher than the proper voltage, the amount of decrease of the output voltage according to the degree is given as the fuzzy inference result ΔV. That is, no matter what value the initial output voltage setting is, test welding is performed for a predetermined time under the set value, and sTs and mTa at that time are used.
If the above-described fuzzy inference is performed using the value of, the output voltage can always be set to an appropriate value.

(2) When the transfer form of the droplet to the base material is globule transfer. ◆ When the droplet transfer mode is globule transfer, the wire feeding speed is relatively high, and the welding current is moderate to relatively large. The standard deviation sTs and standard deviation mTa at this time are
Changes according to the arc voltage as shown in FIGS. 7 and 8, respectively. Therefore, the membership functions of the standard deviation sTs and the standard deviation mTa and the manipulated variable ΔV of the output voltage are determined as shown in FIGS.
The inference rules shown in are set. Then, as in the case of the short circuit transition in the above (1), regardless of the initial output voltage setting, test welding is performed for a predetermined time under the set value, and sTs and If the above fuzzy inference is performed using the value of mTa, the output voltage can always be set to an appropriate value. ◆

[0013]

[Table 1]

FIGS. 4A and 4B and FIGS. 4A and 4B show examples of membership functions with good results.
11 is shown. Note that this example is a case where MAG welding is performed using a solid wire having a diameter of 1.2 mm and a material of mild steel using Ar + 20% CO ₂ mixed gas as a shielding gas. ◆ (A) When the transfer form of the droplet to the base material is a short-circuit transfer. ◆ The wire feeding speed is 3 m / min. ◆ In FIG. 4, ◆ a ₁ = 1.2 ms, a ₂ = 1.5 ms, a ₃ = 2.0 ms, a
₄ = 2.4 ms, ◆ a ₅ = 2.7 ms, a ₆ = 3.2 ms, a
₇ = 3.5 ms, に お い て In FIG. 5, ◆ b ₁ = 0.0 ms, b ₂ = 0.5 ms, b
₃ = 3.0 ms, b ₄ = 3.8 ms, ◆ b ₅ = 4.7 ms, b
₆ = 7.2 ms, b ₇ = b ₈ = 8.0 ms, b ₉ = 11.3 m
s, b ₁₀ = 13.0 ms, b ₁₁ = 15.5 ms, b ₁₂ = 1
8.0 ms, {b ₁₃ = 19.7 ms} In FIG. 6, ◆ c ₁ = c ₂ = -6.5 V, c ₃ = c ₄ = c ₅ = -4.3 V, ◆
c ₆ = c ₇ = c ₈ = −2.2 V, Δc ₉ = c ₁₀ = c ₁₁ = 0
V, c ₁₂ = c ₁₃ = c ₁₄ = 2.2 V, Δc ₁₅ = c ₁₆ = c ₁₇
= 4.3 V, c ₁₈ = c ₁₉ = 6.5 V ◆ (B) When the transfer form of the droplet to the base material is globule transfer. ◆ The wire feeding speed is 7.5 m / min. ◆ In FIG. 9, ◆ a ′ ₁ = a ′ ₂ = 1.4 ms, a ′ ₃ = a ′ ₄ = a ′ ₅ = 1.
₆ ms, {a ′ ₆ = a ′ ₇ = 1.9 ms} In FIG. 10 ◆ b ′ ₁ = 6 ms, b ′ ₂ = 7 ms, b ′ ₃ = 10 ms, b ′ ₄ =
12 ms, ◆ b ′ ₅ = 13 ms, b ′ ₆ = ₁₇ ms, b ′ ₇ =
_{18ms, b'8 = 20ms, ◆} b'9 = 23ms, b'10
_{= 24ms, b'11 = 25ms,} b'12 = 28ms, b'
₁₃ = 29 ms ◆ In FIG. 11, c ′ ₁ = c ′ ₂ = −6.5 V, c ′ ₃ = c ′ ₄ = c ′ ₅ = −
4.3 V, Δc ′ ₆ = c ′ ₇ = c ′ ₈ = −2.2 V, c ′ ₉ =
c ′ ₁₀ = c ′ ₁₁ = 0 V, ◆ c ′ ₁₂ = c ′ ₁₃ = c ′ ₁₄ =
2.2V, which is _{c'15 = c'16 = c'17} = 4.3V ◆ c'18 = c'19 = 6.5V.

Table 3 shows the standard deviation between the short-circuit period and the arc period.
A case where fuzzy inference is performed with sTs and sTa as antecedents, that is, a case where welding is performed by the above-mentioned fifth conventional technique,
It is a comparison with the case of welding according to the present invention. As is clear from the table, in the case where the automatic arc voltage can be automatically set in the range of the appropriate arc voltage ± 0.5 V, the ratio is improved to 85% in the present invention, while it is 50% in the fifth prior art. Further, even in the range of the appropriate arc voltage of ± 0.7 V or ± 1.0 V, the present invention was able to obtain better results than the fifth prior art. ◆

[0016]

[Table 1]

[0017]

As described in detail above, according to the present invention,
In the case of MAG welding in which the shielding gas is a mixed gas of Ar + CO ₂ containing Ar as a main component, the output voltage can be automatically changed to an appropriate value regardless of the initial output voltage setting. it can. Therefore, even if the addition of an extension cable, a power supply voltage, a change in the wire protrusion length, and the like occur, it is not necessary to make fine adjustments to the output voltage, which is conventionally required for the skilled person. There is an effect that a good welding result can always be obtained.

[Brief description of the drawings]

FIG. 1 is a structural example diagram of a welding device for carrying out the present invention.

FIG. 2 is a diagram showing a relationship between a standard deviation sTs of a short circuit period and an arc voltage in a short circuit transition region of MAG welding.

FIG. 3 is a diagram showing a relationship between a standard deviation mTa of an arc period and an arc voltage in a short-circuit transition region of MAG welding.

FIG. 4 is an example of a membership function of sTs for a short-circuit transition region.

FIG. 5 is an example of a membership function of mTa for a short-circuit transition region.

FIG. 6 shows an example of a membership function of ΔV for a short-circuit transition region.

FIG. 7 is a diagram showing a relationship between sTs and an arc voltage in a globule transition region.

FIG. 8 is a diagram showing a relationship between mTa and an arc voltage in a globule transition region.

FIG. 9 is an example of a membership function of sTs for a globule transition area.

FIG. 10 shows an example of a membership function of mTa for a globule transition region.

FIG. 11 is an example of a membership function of △ V for a globule transition area.

FIG. 12 is a diagram showing a relationship between a standard deviation sTa of an arc period and an arc voltage in a short-circuit transition region in CO ₂ welding.

FIG. 13 is a diagram showing a relationship between arc voltage and standard deviation sTa of an arc period in a short-circuit transition region in MAG welding.

[Explanation of symbols]

2 Inverter circuit 6 Wire 10 Output voltage setting device 11 Addition / subtraction circuit 12 Pulse width control circuit 14 Voltage detector 16 Judgment voltage setting device 17 Judging device 18 Ts measuring device 19 Ta measuring device 20, 21 Computing device 23 Setting device 15 Sampling condition setting Vessel 22 Fuzzy controller

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-322882 (JP, A) JP-A-5-42367 (JP, A) JP-A-51-45643 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B23K 9/037 B23K 9/095 B23K 9/12 B23K 9/16

Claims (2)

(57) [Claims] 1. A shielding gas containing Ar as a main component.
In a power control method of a consumable electrode type gas shielded arc welding in which a wire is fed at a substantially constant speed to perform welding by using a mixed gas of r and CO ₂ , a standard deviation of a short-circuit period and an arc measured during welding are measured. A consumable electrode characterized in that the average value of the period is the antecedent part, and the manipulated variable of the output voltage is the consequent part, and fuzzy inference is executed according to a predetermined control rule to determine the amount of increase or decrease in the output voltage setting. Output control method of gas shielded arc welding. 2. A gas containing Ar as a main component as a shielding gas.
The standard deviation of the short-circuit period and the arc period measured during welding in a consumable electrode type gas shielded arc welding welding device that uses a mixed gas of r and CO ₂ to feed a wire at a substantially constant speed for welding. A fuzzy controller for inferring an operation amount of an output voltage for obtaining a predetermined arc state in accordance with a predetermined control rule with a calculation result of the calculation means as an input, and an output of the fuzzy controller Means for increasing and decreasing the output voltage set value of the welding power source in accordance with the welding power supply.