JPH0671438A - Arc welding machine - Google Patents

Abstract

PURPOSE:To provide an excellent welding part even by a beginner by composing so as to store a functional expression by making a reference value of an arc length, an average welding current, a wire feeding velocity, and an average welding voltage between a chip and a base material as variables. CONSTITUTION:An average welding current is obtained from the output of a shunt 7 with an average welding current detecting circuit 12 and inputted to an arithmetic circuit 15. A counter electromotive force of a wire feeding motor 10 is made as a wire feeding velocity with a wire feeding velocity detecting circuit 13 and inputted to the arithmetic circuit 15. An average welding voltage between a chip 3 and a base material 6 is inputted to the arithmetic circuit 15 with a voltage between chip and base material detecting circuit 14. In every definite period, the arc length and a wire projecting length are computed with the arithmetic circuit 15, and the difference between a standard value is obtained. The result is reported to an operator with an annunciator 19. The operator changes the torch length following to the display of the annunciator 19, and the arc length or the wire projecting length can be kept right.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welder having a constant arc length control function.

[0002]

2. Description of the Related Art In arc welding using a consumable electrode (hereinafter referred to as a wire), the wire length from the tip of the tip to the tip of the wire (hereinafter referred to as the wire protrusion length) or the arc length from the surface of the base metal to the tip of the wire is constant. A good weld can be obtained by keeping the temperature at. "Sensing and Control in Arc Welding" (Welding Method Guidebook 2, May 1990)
Published on May 15th, Welding Society, pp. 2-94 to 2-99), the wire protrusion length L _E was calculated by the following formula 1, and the arc length L _A was calculated by the following formula 2. Mechanically correct the position of the welding torch based on the wire protrusion length L
_A technique for keeping _E or arc length L _A constant is disclosed.
However, since the arc voltage V _A in the equation 2 cannot be measured, the voltage drop V _E of the wire protrusion length L _E portion is first obtained by the equations 3 to 5, and the arc voltage V _A is obtained from the equation 6.

[0003]

[Equation 1]

[0004] Here, v: wire feed rate I _E: the effective current I _A: Average Current V _A: the arc voltage V: tip-base voltage V _E: voltage drop of the wire protruding length L _E moiety R: wire Resistance of protrusion length L _E part α: Difference between specific resistance and temperature coefficient of specific heat β: Temperature coefficient of specific resistance C _O : Specific heat J: Work equivalent of heat η _O : Specific resistance ρ: Specific gravity d: Wire diameter Also, K ₁ , K ₂ , K ₃ , K ₄ , K ₅ , and K ₆ are constants. Then, the constants K ₁ and K ₂ used in the above equation 1 are experimentally determined with respect to the protrusion length of the wire that is often used.

[0005]

Generally, in arc welding of a constant speed wire feeding system using a welding power source having a constant voltage characteristic, the welding current value changes when the torch height changes. Further, the constants K ₁ and K ₂ in the above-mentioned prior art Equation 1 change depending on the value of the welding current, as described in the article "Simultaneous control of penetration depth and bead height by multivariable welding parameter control"("Welding Society of Japan"). Proceedings "Vol. 7, No. 1, February 5, 1989
Published by Japan, Welding Society, pp. 21-26).
Furthermore, the physical constants used for the calculation also use values determined under certain assumptions. As a result, the calculated wire protrusion length did not match the actually measured value, and a good welding result could not be obtained in some cases. As for the arc length, since the results of Equation 1 are used in Equations 3 and 5, the calculated value and the actually measured value do not match, as in the case of the wire protrusion length. In the case of semi-automatic arc welding, it is difficult for beginners to select the wire protrusion length or the arc length, or to keep these values constant, and it is often impossible to obtain good welding results. The object of the present invention is to solve the above-mentioned problems and to obtain a uniform welding result in any of semi-automatic arc welding and automatic arc welding, and particularly in the case of semi-automatic arc welding, an appropriate arc length or wire protrusion length is obtained. It is an object of the present invention to provide an arc welder capable of obtaining a good weld with a uniform penetration depth and weld bead width even if it is difficult for a beginner who has difficulty in selecting or keeping these values constant. .

[0006]

Means for Solving the Problems The above-mentioned problems are solved by a condition setting device, a storage device connected to the condition setting device, an arithmetic device connected to the storage device, and a constant voltage characteristic connected to the arithmetic device. It consists of a welding power source, and the storage device stores the function of which the reference value of the arc length input to the condition setting device, the average welding current, the wire feeding speed, and the average welding voltage between the tip and the base metal are variables. The arithmetic unit calculates the arc length at regular intervals from the measured values of the average welding current, wire feed speed, and average welding voltage between the tip and the base metal, and calculates the difference between the calculation result and the reference value by the welding power source. It is solved by adding to the set value of the output current or the set value of the output voltage to control the output of the welding power source so that the arc length becomes constant.

[0007]

During welding, the calculated value of the arc length and the actual value are almost the same. Then, the output of the welding power source is controlled according to the calculation result and the arc length is returned to a preset value, so that the arc length is kept constant.

[0008]

1 is a block diagram of an arc welding machine showing a first embodiment of the present invention. Reference numeral 1 denotes a constant voltage welding power source, and a welding current flows from an output side terminal 2 to an output side terminal 8 through a welding torch tip 3, a wire 4, an arc 5, a base metal 6, and a shunt 7 which are not shown. 9 is a wire feeding control circuit,
Wire feeding roller 11 connected to wire feeding motor 10
To supply the wire 4 to the chip 3. Reference numeral 12 denotes an average welding current detection circuit, which calculates the average welding current from the output of the shunt 7 and inputs it to the arithmetic circuit 15. Reference numeral 13 is a wire feeding speed detection circuit, which utilizes the fact that the wire feeding speed and the counter electromotive voltage of the wire feeding motor 10 are in a substantially proportional relationship, and the counter electromotive voltage of the wire feeding motor 10 is supplied to the arithmetic circuit 15. input. 1
4 is a chip-base material voltage detection circuit, which is a chip 3 and a base material 6
The average welding voltage between and is input to the arithmetic circuit 15. 15
Is an arithmetic circuit, which performs arithmetic operations described later. Reference numeral 16 denotes a keyboard for presetting a reference arc length, a reference wire protrusion length, and their allowable deviation in accordance with welding conditions. Reference numeral 17 denotes a memory, which stores the setting constant input from the keyboard 16 and the calculation result of the calculation circuit 15. Then, the arithmetic circuit 15 has a voltage corresponding to the average welding current detected by the current detection circuit 12 at predetermined constant intervals,
From the voltage corresponding to the wire feeding speed detected by the wire feeding speed detecting circuit 13 and the average welding voltage detected by the tip-base metal voltage detecting circuit 14, the arc length and the wire protrusion are stored by a pre-stored functional expression. Calculate the length. Further, the deviation obtained by calculating the arc length deviation, which is the difference between the reference arc length and the calculated arc length, is output to the adder 18, while the reference wire protrusion length and the calculated wire protrusion are output. When the deviation value obtained by calculating the wire protrusion length deviation, which is the difference from the length, exceeds the allowable deviation, a signal is output to the alarm device 19. Note that the alarm device 19 is a sound notification circuit that has three levels of high tone, no sound, and low tone, depending on whether the deviation of the wire protrusion length is large, appropriate, or small, or the deviation of the wire protrusion length is large. A voice notification circuit that emits different sounds depending on the case and a small case, a lamp notification circuit that lights a lamp of a different color, or a liquid crystal notification circuit that distinguishes by three symbols of +, −, and 0. Further, 20 is a current voltage setting device for presetting the output of the constant voltage welding power source 1.

Here, before describing the operation, an arithmetic expression of the arc length and the wire protrusion length will be described. As described above, in the arc welding of the constant speed wire feeding method using the constant voltage welding power source, the welding current and the tip-base metal voltage also change when the torch height changes. Therefore, the arc length l _a
And the wire protrusion length l _e are set as a linear function having the average welding current I, the wire feeding speed v, and the average welding voltage V between the tip and the base metal as variables, as shown in Equations 7 and 8. Arc length: l _a = A + B · I + C · V + D · v Formula 7 Wire protrusion length: l _e = E + F · I + G · V + H · v Formula 8 where A, B, C, D, E, F, G and H are It is a constant. Then, the constants A to H were determined as follows. That is, arc welding is performed by changing the welding current and torch height, and the data of the arc length or wire protrusion length from the base metal surface to the wire tip obtained by actual measurement with a CCD camera is used as the target variable, and the wire feeding is performed. The constants A to H were determined from the regression equation obtained by multiple regression analysis using the speed, the welding current, and the tip-base metal voltage as explanatory variables. For example, as the welding conditions, the welding current is changed to 80 to 350 A, and the torch height is changed to 10 to 35 mm.
When carbon dioxide arc welding is performed using φ mild steel wire, the constants A, B, C and D are A = 2.85 and B = −, respectively.
0.0278, C = 0.14, D = 0.04, E = 25.
44, F = −0.20, G = 0.12, H = 0.20. Then, carbon dioxide arc welding was performed again, and the arc length and the wire protrusion length at this time were measured by a CCD camera. As a result, it was confirmed that they were in good agreement with those actually measured as shown in FIGS. 3 and 4.

The operation will be described below. Prior to welding, the welding condition, that is, the welding voltage value and the welding current value are set by the current / voltage setter 20 according to the designated work standard. Then, the standard arc length, the standard wire protrusion length, and the permissible deviation thereof according to the welding conditions are input by the keyboard 16. During the welding operation, the arithmetic circuit 15 outputs signals from the average welding current detection circuit 12, the wire feeding speed detection circuit 13 and the tip-base metal voltage detection circuit 14 every predetermined period, for example, 0.1 to 1 second. Is used to calculate the arc length and the wire protrusion length by a pre-stored function formula. Further, the arc length deviation, which is the difference between the reference arc length and the arc length obtained by the calculation, is calculated. For example, when the arc length becomes long due to the hand shake of the operator, the negative arc length deviation is added to the preset welding voltage to lower the welding voltage, and the arc length returns to the preset value. On the other hand, the wire protrusion length deviation, which is the difference between the reference wire protrusion length and the calculated wire protrusion length, is calculated, and when the calculated deviation value exceeds the allowable deviation, a signal is output to the alarm device 19 to notify. The device 19 is operated. Therefore, if the operator changes the torch height in accordance with the information displayed on the alarm 19 and returns the wire protrusion length to a preset value, it is possible to prevent the wire protrusion length from becoming excessive and the shield from being deteriorated. Although the arc length deviation is added to the welding voltage in this embodiment,
It may be added to the welding current. When adding to the welding current, the welding current is increased by increasing the wire feed rate when the arc length becomes long.
Further, the wire protrusion length deviation may be used instead of the arc length deviation. Further, the allowable deviation of the arc length deviation may be set, and the alarm 19 may be operated when any deviation exceeds the allowable deviation.

FIG. 2 is a block diagram of an arc welding machine showing a second embodiment of the present invention. The second embodiment is different from the first embodiment in the following (a) to (d). (A) Instead of the wire feed speed detection circuit 9, the set current value of the current / voltage setter 20 is used as the wire feed speed to the arithmetic circuit 1.
5, and used for various calculations already described in the first embodiment. The wire feeding speed is calculated by the equation 9. v = 0.633I-29.3 Formula 9 Here, v is a wire feeding speed (mm / s), and I is a set current (A). (B) From the keyboard 16, in addition to the standard arc length, the standard wire protrusion length, and the permissible deviation thereof, the permissible deviation of the arc length and the permissible value of the time variation of each permissible deviation can be set in advance. It has become. (C) The arithmetic circuit 15 determines, in addition to the arc length, the wire protrusion length, and the respective deviations, a temporal change in each deviation, that is, the calculated arc length deviation or wire protrusion length deviation and the immediately preceding cycle. An arc length deviation difference value or a wire protrusion length deviation difference value, which means a difference value with each calculated deviation, is also calculated. (D) The control device 2 is provided between the arithmetic circuit 15 and the adder 18.
1 is placed. The operation will be described below. The description of the same points as those in the first embodiment will be omitted. The controller 21 takes in at least one of the arc length deviation, the wire protrusion length deviation, the arc length deviation difference value or the wire protrusion length deviation difference value output from the arithmetic circuit 15, and outputs the output described below to the adder 18. Output. That is, the increase or decrease of the arc length deviation or the wire protrusion length deviation should be prevented from increasing or decreasing, and the increase or decrease of the arc length deviation difference value or the wire protrusion length deviation difference value should cause a temporal change in the output. Is output to the adder 18. If the deviation is added to the set value as it is, for example, the arc length always fluctuates. Therefore, when the deviation is within the allowable deviation, the output may be set to 0 or a small value.
On the other hand, the arithmetic circuit 15 changes the output signal to the alarm 19 when the time variation of the arc length and its allowable deviation and the wire protrusion length and its allowable deviation exceeds a preset allowable value. In the case of the sound notification circuit, the high pitch generated is shortened. As a result, when there is a step in the base material, it can be changed quickly, and in other cases, it can be changed gently, and a welded part having a uniform appearance can be obtained. In the above two embodiments, the wire feeding speed may be measured by the number of rotations of the wire feeding roller 5, or the voltage between the output terminals of the constant voltage welding power source 1 may be used instead of the voltage between the tip and the base metal. May be input. In addition, the current detection circuit 1
It is also possible to directly input the respective voltages to the arithmetic circuit 15 without providing the wire feeding speed detection circuit 13 and the chip-base material voltage detection circuit 14. Furthermore, l _a , l _e
May be a function other than a linear function of I, V, and v.

[0012]

As described above, according to the present invention, the wire protrusion length and the arc length are obtained from the measurable welding current, the wire feeding speed, and the tip-base metal voltage, and the calculated values are obtained. When the reference value input in advance is changed, the output of the constant voltage welding power source 1 is controlled so as to return to the reference value. Therefore, it is possible to obtain uniform welding results in both semi-automatic arc welding and automatic arc welding. Especially in the case of semi-automatic arc welding, select an appropriate arc length or wire protrusion length, or keep these values constant. Even if it is difficult for a beginner who has difficulty in keeping the same, it is possible to obtain a good weld with a uniform penetration depth and weld bead width.

[Brief description of drawings]

FIG. 1 is a block diagram of an arc welder showing a first embodiment of the present invention.

FIG. 2 is a block diagram of an arc welding machine showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a measured value of an arc length and a calculated value.

FIG. 4 is a diagram showing a relationship between a measured value of a wire protrusion length and a calculated value.

[Explanation of symbols]

 1 constant voltage welding power source 3 chip 4 wire 5 arc 7 shunt 10 wire feeding motor 12 current detection circuit 13 wire feeding speed detection circuit 14 chip-base material voltage detection circuit 15 arithmetic circuit 16 keyboard 17 memory 18 adder 19 Alarm device 20 Current / voltage setting device 21 Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiroku Fujiwara, Ibaraki Prefecture, 502 Kandachi-cho, Tsuchiura-shi, Ibaraki Machinery Research Institute Co., Ltd. Machinery Research Laboratory

Claims (6)

[Claims] 1. A condition setting device, a storage device connected to the condition setting device, an arithmetic device connected to the storage device, and a welding power source of a constant voltage characteristic connected to the arithmetic device,
The memory device is configured to store a function formula having the reference value of the arc length and the average welding current, the wire feeding speed, and the average welding voltage between the tip and the base metal as variables, which are input to the condition setting device. The arc length is calculated from the measured values of the average welding current, wire feed speed, and average welding voltage between the tip and the base metal at regular intervals, and the difference between the calculation result and the reference value is set to the output current of the welding power source. Alternatively, a welding device for consumable electrode type arc welding using a constant-voltage welding power source characterized by being configured to control the output of the welding power source so that the arc length becomes constant by adding to the set value of the output voltage . 2. In addition to the reference value of the arc length, the reference value of the wire protrusion length is stored in a storage device in advance, and at least one of the difference between the calculation results of the arc length and the wire protrusion length and the respective reference values is used as a welding power source. The welding apparatus according to claim 1, wherein the welding current is added to the set value of the output current or the set value of the output voltage. 3. In addition to the reference values of the arc length and the wire protrusion length, respective allowable deviations are stored in advance in a storage device, and an alarm device is connected to the arithmetic unit to calculate the arc length and the wire protrusion length and the respective calculation results. At least one of the differences from the reference value is added to the setting value of the output current or the setting value of the output voltage of the welding power source, and the alarm device is operated when at least one of the respective differences exceeds the corresponding allowable deviation. 2. The structure according to claim 1, wherein
Alternatively, the welding device according to claim 2. 4. A storage device for storing the reference values of the arc length and the wire protrusion length, and the allowable deviations of the arc length and the wire protrusion length, as well as the temporal allowable values of the respective allowable deviations and the calculation results of the calculation device. 4. The welding apparatus according to claim 3, wherein the notification operation of the notification device is changed when the temporal change of the deviation exceeds a preset allowable value. 5. A controller is connected between the arithmetic unit and the welding power source, and the controller outputs the arc length deviation, the wire protrusion length deviation, the arc length deviation difference value or the wire protrusion length deviation difference value output from the arithmetic unit. Take in at least one of the
The deviation does not increase or decrease as the arc length deviation or wire protrusion length deviation increases or decreases, and the temporal change in output is small when the arc length deviation difference value or the wire protrusion length deviation difference value increases or decreases. The output of the welding power source is controlled so that the arc length or the wire protrusion length becomes constant by adding this output to the setting value of the output current or the setting value of the output voltage of the welding power source. The welding apparatus according to any one of claims 1 to 4, which is configured. 6. The welding apparatus according to claim 1, wherein the wire feeding speed is obtained from a set value of welding current.