JPH0584572A - Semiautomatic arc welding machine - Google Patents

Abstract

PURPOSE:To allow even a beginner to perform stable welding in the same way as an expert operator and to obtain a weld zone having high quality and reliability by controlling an arc length constantly in semiautomatic arc welding. CONSTITUTION:The semiautomatic arc welding machine is provided with an arc length arithmetic circuit 13 which calculates the arc length from detected values of a wire feed rate detector 10, a welding current detector 11 and a detector 12 of the voltage between a tip and base metals, an arc length setting device 14, a deviation arithmetic circuit 15, an arc length change arithmetic circuit 16 and a fuzzy controller 17. The deviation of the arc length and the time change of the arc length are inputted to the fuzzy controller 17 and the set welding voltage of a constant voltage welding power source 6 is controlled via a welding current and voltage controller 7 by the output of the fuzzy controller 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-automatic arc welder having a constant arc length control function by fuzzy reasoning.

[0002]

2. Description of the Related Art Conventionally, in automatic arc welding, in which a wire as a consumable electrode is constantly fed to a welding torch, and the operation of moving an arc along a welded joint while maintaining a constant arc length is performed by a machine, wire protrusion If the length or the arc length changes, the welding conditions fluctuate and the welding result is adversely affected. Therefore, as shown in JP-B-63-45915 "Automatic control method for distance between tip and work piece", welding current, The voltage between the tip and the base metal and the wire feed speed are detected, and the wire protrusion length and arc length are calculated from these detected values, and the welding torch position (torch height) is mechanically corrected based on this calculation result. By doing so, the wire protrusion length and the arc length are optimized.

On the other hand, in semi-automatic arc welding in which a welding operator holds a welding torch in his / her hand, there are many cases in which beginners perform welding recently due to lack of manpower, and conventional semi-automatic arc welding machines cannot perform stable welding. In particular, there is a problem that welding conditions fluctuate due to camera shake of a welding operator and adversely affect welding results.

In order to solve this problem, an up-and-down moving device equipped with a welding torch of an automatic arc welding machine for mechanically controlling the distance between the tip and the base metal as shown in the above-mentioned known example. When the welding operator holds in his hand and performs semi-automatic arc welding, the shaking of the operator's hand and the movement of the operator's hand to keep the distance between the tip and the base metal constant and the vertical movement with the welding torch attached Since the movement of the device is not synchronized, the distance between the tip and the base metal is not constant, and a good welding result cannot be obtained.

Further, in a semi-automatic arc welding machine which uses a welding current having a constant voltage characteristic, the welding current increases or decreases in response to a change in the arc length, and the self-control of the power source is performed by the constant voltage characteristic in which the arc length is restored. It is known that there is an effect, but when the wire protrusion length changes, the wire melting rate is affected by the size of the protrusion length even at the same current value, so it is not enough to rely on the self-control action of the power supply. It is also sufficient, and it is also known that the arc length cannot be maintained constant without positive control from the outside.

[0006]

As described above, the welding operator holds the welding torch in which the wire is constantly mechanically fed, and moves the arc along the welded joint while keeping the arc length constant. In arc welding, how to optimize the wire protrusion length and arc length is an issue in order to enable even beginners to perform stable welding as well as skilled workers. Originally, in semi-automatic arc welding, the welding torch is held by the welding operator and the welding is performed, so the distance between the tip and the base metal is artificially determined and mechanical control is impossible, but the tip and base metal It is considered possible for the welding operator himself to correct the distance between the tip and the base metal by detecting this by some means and notifying the welding operator when the distance between the two exceeds an appropriate value. Therefore,
In this case, if the arc length can be controlled to be constant,
The wire protrusion length can be optimized.

Therefore, an object of the present invention is to provide a semi-automatic arc welding machine in which the arc length is controlled to be constant so that even a beginner can perform stable welding as well as a skilled worker and obtain a good quality welding result. To provide.

[0008]

In order to achieve the above object, the present invention provides a welding torch operated by the hand of a welding operator and a wire feed for feeding a wire while contacting the inner surface of the tip of the welding torch. In a semi-automatic arc welding machine equipped with a device and a welding power source of constant voltage characteristic for supplying electric power to a tip and a base metal, each of a welding current detector, a tip, a base material voltage detector and a wire feed speed detector Arc length calculation means for calculating the arc length from the detected value, deviation calculation means for calculating the deviation between the arc length obtained by the above calculation and the arc length set by the arc length setter according to the welding conditions, and the above calculation The arc length change amount calculating means for calculating the time change amount of the arc length obtained in 1., the output of the deviation calculating means and the output of the arc length change amount calculating means are input, and a predetermined control rule is set. It is equipped with a fuzzy controller that infers the manipulated variable for more constant control of the arc length, and controls the welding voltage setting of the welding power source by the output of the above fuzzy controller to control the distance between the tip and the base metal. The arc length is controlled to be constant.

[0009]

[Function] The welding current detector, the tip-base metal voltage detector, and the wire feed speed detector detect the welding current, tip-base metal voltage, and wire feed speed during semi-automatic arc welding. Using the value, the deviation between the arc length calculated by the arc length calculation means and the arc length set by the arc length setting device is calculated by the deviation calculation means, and the temporal change of the arc length calculated by the above calculation is changed. The operation amount required for constant arc length control is deduced according to a predetermined control rule by inputting the deviation and the temporal change amount of arc length by a fuzzy controller, based on this deduction result. Setting of constant voltage welding power source By controlling the welding voltage,
The arc length is controlled to be constant by increasing or decreasing the wire welding speed while keeping the wire feeding speed constant with respect to the change in the distance between the tip and the base material.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The semi-automatic arc welding machine shown in FIG. 1 has a welding torch 1 having a gas discharge nozzle (not shown) for flowing a shielding gas around a tip 2 and an arc 4, a wire feeding motor 8 and a feeding roller. The wire feeding device 9 includes a welding power source 6 having a constant voltage characteristic, and a welding current / voltage controller 7. Welding work is
The motor 8 with the welding torch 1 held by the welding operator.
The wire 5 is continuously fed while being brought into contact with the inner surface of the tip 2 by the feeding roller 9 connected to the tip 2, and the tip 2 and the base metal 3 are supplied with electric power from the welding power source 6 according to the welding conditions set by the welding current / voltage controller 7. Is supplied, an arc 4 is generated between the wire 5 and the base material 3 to melt the wire 5, and the wire 5 is fused to the base material 3.

The names of each part between the chip 2 and the base material 3 shown in FIG. 1 will be described with reference to FIG. In FIG. 3, the length of the wire 5 from the tip of the tip 2 to the arc 4 is the wire protrusion length LE, the length of the arc portion from the tip of the wire 5 to the surface of the base material 3 is the arc length LA, and the wire protrusion. The sum of the length LE and the arc length LA is the distance between the tip and the base metal.

In the semi-automatic arc welding machine having the above-described structure, in order to control the arc length to be constant during semi-automatic arc welding performed by the welding operator holding the welding torch 1 by hand,
It is necessary to know the arc length during welding. The wire protrusion length and the arc length during welding are as described in Guidebook “Sensing and Control in Arc Welding”, Welding Society, Welding Method Research Committee, May, 1990, II-94 to II-99. It can be calculated from the detected values of welding current, tip-base metal voltage, and wire feed speed by the following formula.

(1) Calculation formula of wire protrusion length The wire protrusion length LE is calculated from the average current IA, the effective current IE, and the wire feeding speed v by the following equation.

[0015]

[Equation 1]

Here, k ₁ and k ₂ are constants.

(2) Calculation formula of arc length The arc length LA is calculated by the following formula from the average current IA and the arc voltage VA.

[0018]

[Equation 2]

Here, k ₃ , k ₄ , k ₅ and k ₆ are constants.

However, the arc voltage VA in the equation (2) cannot be measured, and the detected tip-base material voltage V, the resistance R of the wire protrusion length and the wire protrusion length obtained from the average current IA. The arc length LA is obtained by substituting the obtained arc voltage VA in the equation 2 from the voltage drop VE by the following arithmetic expression.

[0021]

[Equation 3]

[0022]

[Equation 4]

[0023]

[Equation 5]

Where α is the difference between the temperature coefficient of specific resistance and the specific heat, β is the temperature coefficient of specific resistance, C ₀ is the specific heat, η ₀ is the specific resistance, J is the work equivalent of heat, ρ is the specific gravity, and d is It is the wire diameter and the constant k ₇ is k ₇ = 16αη ₀ / π ² JρC ₀ d ⁴ .

In FIG. 1, the wire feed speed detector 10 such as a tachometer dynamo connected to the feed roller 9 or the wire feed speed and the counter electromotive voltage of the motor 8 are in a substantially proportional relationship. A wire feeding speed is detected by a back electromotive force detector (not shown) of the motor 8 and a welding current detector 11 is connected between the welding power source 6 and the base metal 3 or between the welding power source 6 and the tip 2. , And the tip-base material voltage detector 12 connected between the tip 2 and the base material 3, respectively, detects the tip-base material voltage, and inputs these detected values into the arc length calculation circuit 13, The length calculation circuit 13 calculates the average current and the effective current from the detected welding current, and also calculates the arc length according to the equations (1) to (5). The deviation calculation circuit 15 takes in the arc length calculated by the arc length calculation circuit 13 and the arc length previously set by the arc length setter 14 according to the welding conditions, and calculates and outputs the deviation between the two. Further, the arc length change calculation circuit 16 is a circuit for calculating the time change of the arc length by using the deviation of the arc length output from the deviation calculation circuit 15 as an input, and a differentiator is used as a simple method. May be. The fuzzy controller 17 receives the deviation of the arc length output from the deviation calculation circuit 15 and the temporal change of the arc length calculated by the arc length change calculation circuit 16 as input, and controls the constant arc length as described in detail below. The operation amount necessary for the above is deduced, and the obtained operation amount is output to the welding current / voltage controller 7. The fuzzy controller 17 comprises a memory device 18 and a fuzzy inference processor 19.

In this embodiment, the fuzzy inference processor 1
As the operation amount from 9, the change amount of the set welding voltage for the constant voltage welding power source 6 is output. The memory device 18 is a memory device for storing control rules and membership functions necessary for fuzzy inference executed by the fuzzy inference processor 19. The control rules and membership functions stored in the memory device 18 are necessary. It is possible to add or change according to.

The fuzzy inference for obtaining the change amount of the set welding voltage which is the operation amount of the constant arc length control is executed based on the following control rule. The control rules adopted in this embodiment consist of the following nine rules. That is, R ₁ ; If the arc length is short (P) and the arc length is decreasing (P), increase the set welding voltage (P).

R ₂ ; If the arc length is proper (Z) and the arc length does not change (Z), leave the set welding voltage as it is (Z).

R ₃ ; If the arc length is long (N) and the arc length is increasing (N), decrease the set welding voltage (N).

.. and so on. The above rule is the control rule of the welding power source which is optimum for the constant arc length control based on the empirical rule obtained by the inventor from a large number of experimental data for the welding expert, and the rule of the arc length deviation and the arc length Table 1 shows the function of the change of the set welding voltage with respect to the time change.

[0031]

[Table 1]

In Table 1, the degree of deviation of the arc length is divided into three levels (P: short, Z: appropriate, N: long) in the vertical direction, and the degree of temporal change of the arc length in the horizontal direction is 3. The position where P is decreasing, Z is not changing, N is increasing, and is shown separately, and the intersecting position of each of the divided arc length deviation and the temporal change of the arc length is shown. In addition, the deviation of the arc length and the degree of change of the optimum set welding voltage according to the degree of change of the arc length with time are classified into three levels (P;
One is divided into (increase, Z; unchanged, N; decrease). That is, the conclusion part of the control rules R ₁ , R ₂ , R ₃ ... Is shown by the squares in Table 1.

Here, the deviation of the arc length, the time variation of the arc length, and the variation of the set welding voltage are defined as follows.

(1) Arc length deviation En = L-Ln where En is the deviation at the current time n, L is the set arc length, Ln is the arc length at the current time n (2) The time change of the arc length ΔE = (En−En−1) = (L−Ln) − (L−Ln−1) = Ln−1−Ln where En−1; deviation at the previous time n−1, Ln−1; previous Arc length at time n-1 (3) Change in set welding voltage ΔU = Un-Un-1 where Un; set welding voltage at current time n, Un-
1; Set welding voltage at previous time n-1 The fuzzy inference processor 19 retrieves the control rule stored in the memory device 18, and changes the set welding voltage for the welding power source 6 by fuzzy inference based on this control rule. The calculated change amount of the set welding voltage is output to the welding current / voltage controller 7 as an operation amount. The welding current / voltage controller 7 adds the change amount of the set welding voltage, which is the operation amount, to the set welding voltage at the previous time n-1,
It has a function of controlling the output voltage of the welding power source 6, that is, the welding voltage.

In the control rules R ₁ , R ₂ , R _3, ..., The degree of deviation of the arc length, the time variation of the arc length, and the variation of the set welding voltage are determined stepwise as shown in Table 1. ,
In order to perform detailed constant arc length control, the degree of conformity is calculated by calculating the deviation of the actual arc length obtained by calculation and how much the temporal change in arc length satisfies the control rule. It is necessary to determine the fixed value of the change in the set welding voltage corresponding to the above as the manipulated variable. Therefore, in the present embodiment, the fitness is calculated by using the membership function of the fuzzy variable for the deviation of the arc length, the temporal change of the arc length and the change of the set welding voltage.

FIG. 2A shows the membership function of the fuzzy variables N, Z and P with respect to the deviation of the arc length, and FIG. 2B shows the fuzzy variables N, Z and P with respect to the temporal change of the arc length. 2C, and FIG. 2C shows fuzzy variables N, Z, P with respect to changes in the set welding voltage.
The membership functions of are respectively shown.

The fuzzy inference processor 19 of FIG. 1 executes fuzzy inference by the following procedure. That is, with respect to the deviation of the arc length and the temporal change of the arc length during the semi-automatic arc welding obtained by the calculation, the above control rules R ₁ , R ₂ ,
MAX-MI called a direct method using R ₃ ... And the membership functions shown in (a), (b), and (c) of FIG.
The degree of conformity to each control rule is obtained by N calculation, the membership function of the corresponding manipulated variable (change in set welding voltage) is determined, and then the manipulated variable obtained by integrating the inference results for each rule ( The estimated value of the manipulated variable (change in set welding voltage) is calculated from the center of gravity of the membership function (change in set welding voltage).

The amount of change in the set welding voltage as the manipulated variable thus obtained is output from the fuzzy controller 17 to the welding current / voltage controller 7 to control the welding voltage of the semi-automatic arc welding machine. This semi-automatic arc welder uses a constant-voltage welding power source, so if the arc length becomes short, increasing the welding voltage will increase the welding current to increase the wire melting speed and increase the arc length. When the welding voltage is lowered, the welding current decreases and the wire melting rate decreases, and the arc length is restored to its original value.

In a semi-automatic arc welding machine using a welding power source having a constant voltage characteristic, there is a method of changing the wire feeding speed in order to control the arc length. However, if the wire feeding speed is changed, the base metal is correspondingly changed. Since the amount of welding on the welding bead changes, unevenness is likely to occur on the welding bead. On the other hand, when the welding voltage is changed while the wire feeding speed is kept constant, the welding amount does not change even if the welding current changes.
The unevenness of the weld bead hardly occurs, which is effective in improving the quality of the welded part.

Further, in recent semi-automatic arc welders, inverter control is adopted for output control of the welding power source,
The control frequency is higher than the thyristor control used for speed control of the wire feed motor by more than two digits, so controlling the output voltage of the welding power source is more controllable than controlling the wire feed speed. good.

Furthermore, by using not only the deviation of the arc length but also the deviation of the arc length and the temporal change of the arc length as the control parameters as in the present embodiment, camera shake during semi-automatic arc welding and the welding target material It is possible to smoothly control the constant arc length without causing hunting, even when the distance between the tip and the base material changes due to a step or the like.

Further, since the control rule is based on the empirical rule of a welding expert, a highly stable constant arc length control is possible, and if necessary, the control rule stored in the memory device 18, By adding or changing the membership function, it is possible to control according to the wishes of each welding operator.

In the above embodiment, the arc length calculating means,
Although an example in which separate arithmetic circuits are used as the deviation arithmetic means and the arc length variation arithmetic means has been described, these functions can be realized by the program processing of a digital computer.

[0044]

As described above, according to the present invention, the constant voltage welding power source is set based on the result of the fuzzy inference using the calculated arc length and the set arc length deviation and the temporal change of the arc length as inputs. Since the arc length is controlled to be constant by controlling the welding voltage, the changed arc length can be adjusted even when the distance between the tip and the base metal fluctuates due to the shaking of the welding operator or the step of the workpiece. It can be quickly returned to the original state to enable welding with a constant arc length, and the penetration depth and weld bead width can be made uniform by the constant speed movement of the welding torch. As a result, even a beginner can perform stable semi-automatic arc welding as well as a skilled worker, a welded portion with high quality and reliability can be obtained, and the efficiency of welding work can be improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a membership function according to an embodiment of the present invention, in which (a) is a fuzzy variable N, with respect to an arc length deviation.
Z and P membership coefficients, (b) the fuzzy variables N, Z and P membership functions with respect to changes in the arc length over time, and (c) fuzzy variables N and Z with respect to changes in the set welding voltage. , P for membership coefficients.

3 is a partially enlarged view of the welding arc portion of FIG.

[Explanation of symbols]

1 ... Welding torch, 2 ... Tip, 3 ... Base metal, 4 ... Arc,
5 ... Wire, 6 ... Constant voltage welding power source, 7 ... Welding current / voltage controller, 8 ... Wire feeding motor, 9 ... Feeding roller, 10
… Wire feeding speed detector, 11… Welding current detector, 12
... Chip / base material voltage detector, 13 ... Arc length calculation circuit, 14 ... Arc length setting device, 15 ... Deviation calculation circuit, 16
… Arc length change calculation circuit, 17… Fuzzy controller, 1
8 ... Memory device for storing control rules, 19 ... Fuzzy inference processor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Kashima 2100 Kamiimazumi, Ebina City, Kanagawa Prefecture Hitachi Seiko Co., Ltd. (72) Inventor Tsuneo Mita 2100, Kamiimazumi, Ebina City, Kanagawa Pref.

Claims (1)

[Claims] 1. A welding torch operated by a welding operator, a wire feeder for feeding a wire while contacting the inner surface of the tip of the welding torch, and a constant voltage characteristic for supplying electric power to the tip and the base metal. In a semi-automatic arc welder equipped with a welding power source, a welding current detector, an arc length calculating means for calculating an arc length from the respective detection values of the tip / base metal voltage detector and the wire feeding speed detector, Deviation calculating means for calculating a deviation between the arc length obtained by the above calculation and the arc length set by the arc length setting device according to welding conditions, and an arc length for calculating a temporal change of the arc length obtained by the above calculation The change amount calculating means, the output of the deviation calculating means, and the output of the arc length changing amount calculating means are used as inputs to infer an operation amount for controlling the arc length constant according to a predetermined control rule. And a fuzzy controller that controls the welding voltage set by the welding power source based on the output of the fuzzy controller to control the arc length to a constant value with respect to changes in the distance between the tip and the base metal. And semi-automatic arc welding machine.