JPS6249147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an arc welding device, and particularly to an automatic groove tracing arc welding device that utilizes arc characteristics for multilayer welding without weaving.

[Conventional technology]

In arc welding methods such as MIG, CO ₂ or SAW, when welding a groove in a thick base material in multiple layers without weaving, a detection block such as a tracing roller is placed in front of the welding electrode to follow the groove. Similarly, placing a groove detection block using electromagnetic induction in front of the welding electrode complicates the configuration around the welding electrode of the welding machine, and also makes it difficult to connect the groove detection point and the welding electrode to be controlled. This involves various problems, such as a delay in control based on the interval distance, which requires countermeasures to correct it. Regarding this point, JP-A-57-14471 and JP-A-Sho
The method described in Figure 7 of No. 52-15457 shows one of the countermeasures, but the arc welding method described in the former publication detects the welding current flowing through each of the left and right parallel welding wires. The sum of these currents (I _L +I _R ) is equal to 2 of the initial arc current.
In this method, the welding torch is controlled in the height direction so that the distance is always equal to 2.times., and the welding torch is controlled in the groove width direction in a direction to cancel the deviation between I _L and I _R. Further, the arc welding method described in the latter publication is also based on substantially the same idea as above.

However, none of the above methods specifically describes means for detecting the welding current flowing through each welding wire. In particular, depending on the detection means used, there are problems such as widening noise and inaccurate control.

[Problem that the invention seeks to solve]

Therefore, the present invention relates to a method in which the welding arc itself is used as a groove detection sensor in arc welding in which multiple layers of welding grooves are welded without weaving, and which accurately performs groove tracing control under constant arc length control. The purpose of the present invention is to provide an arc welding device that can perform the following steps.

[Means for solving problems]

The arc welding device according to the present invention simultaneously energizes a pair of parallel welding wires that are fed to a welding groove in parallel in the width direction of the groove at the same speed, and an electrode tip of the parallel welding wire. The welding device is equipped with the same welding power source that performs the welding process, and a moving device that has a vertical and groove width movement mechanism that moves the parallel welding wire along the welding groove. a common housing that is inserted through the housing in a contact state; and a current-carrying chip plate that is made of the same material and length and is elastically pressed against each parallel welding wire within the housing under equal contact pressure; A wire passage hole consisting of a V-shaped contact groove for each welding wire formed in each current-carrying chip plate and the common housing, and means for detecting a voltage drop at both ends of a mutually equal wire length section in the current-carrying chip plate. It is equipped with the following.

[Effect]

In the present invention, when performing multi-layer welding while feeding a pair of welding wires in parallel to a welding groove, the arc characteristics are utilized for groove tracing, and the pair of welding wires are fed in parallel in the width direction of the welding groove. At the same time, the parallel welding wires are fed in parallel at the same speed, and the same welding power source simultaneously energizes each of the current-carrying chip plates that make up the electrode chip for this parallel welding wire, and an arc is generated from each of the parallel welding wires against the base metal. In this case, the electrode tip is moved up and down so that the welding current or welding wire feeding speed is maintained at a predetermined value. At the same time, each of the parallel welding wires is made of the same material and has the same length and is brought into even pressure contact with a common housing. are brought into sliding contact while maintaining an electrical contact state in a wire length section that is equal to each other, and the voltage drop at both ends of the wire length section of each current-carrying chip board is detected, thereby obtaining both voltage drop detection values. Based on this, the parallel welding wires are integrally shifted in the groove width direction to perform groove tracing control so that the current flowing through each parallel welding wire is always equal within a predetermined offset range. . Since the electrical contact state of the parallel welding wires is made through a common housing and a wire passage hole consisting of a V-shaped contact groove formed in each current-carrying chip plate, contact resistance can be maintained evenly. It is. Furthermore, since the welding current flowing through each welding wire is detected by detecting the voltage drop at both ends of the same wire length section of each current-carrying chip plate, accurate detection and control are possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 2 is an enlarged vertical sectional view of an electrode chip portion, Fig. 3 is a plan view thereof, and Fig. 4 is a control block diagram, and the same reference numerals are the same. or a considerable portion thereof.

In FIG. 1, 1 is a welding base material, and a pair of welding wires 2L, 2R are inserted into the welding groove (V groove) in parallel in the width direction of the groove via wire guide nozzles 3L, 3R. The feed motor 4 feeds them simultaneously and in parallel at the same speed. These wires 2
L and 2R are simultaneously energized from a common welding power source 6 via an electrode tip 5 attached to the lower part of the wire guide nozzles 3L and 3R, thereby creating a base metal bevel at the tips of the wires 2L and 2R. An arc is generated between each of them. 7
are the electrode tip 5 and wire guide nozzles 3L and 3R.
This is an electrode support block that supports the feed motor 4 and the like, and is attached to the welding cart 10 via an electrode tip lifting mechanism 8 and a tracing drive mechanism 9.

That is, the trolley 10 moves along the welding groove,
The copying drive mechanism 9 uses its drive motor 11 and feed screw mechanism 12 to shift the block 7 in the groove width direction, and the elevating mechanism 8 uses its elevating drive motor 13 and feed screw mechanism 14 to shift the block 7. It moves up and down.

A specific example of the structure of the electrode chip 5 is shown in FIGS. 2 and 3. That is, the electrode chip 5
A pair of current-carrying chip plates 15L, 15R, a common housing 16 that holds them, and an elastic means 17 that presses and biases both chip plates 15L, 15R toward welding wires 2L, 2R within the housing 16.
It will be equipped with. As shown in FIG. 3, wire passage holes 18L and 18R consisting of V-shaped contact grooves facing each other are formed in the inner surface of the housing 16 and each of the current-carrying chip plates 15L and 15R, and welding wires 2L and 2R are formed in the inner surface of the housing 16 and in each of the current-carrying chip plates 15L and 15R. is fed through the passage holes 18L, 18R while sliding on the current-carrying chip plates 15L, 15R. Both energizing chip plates 15L and 15R are made of the same material and have the same height dimension l, and are pressed with a substantially uniform force over the entire surface by a spring-based resilient means 17.
As a result, the welding wires 2L and 2R are pressed and held in the passage holes 18L and 18R between the inner surface of the housing 16 and both chip plates 15 are held by sliding of the wires.
By keeping the electrical contact between L and 15R and welding wires 2L and 2R unchanged, that is, by keeping the contact resistance equal, electrical contact is maintained on a line or surface in a section of length l even during wire feeding. It is designed to be maintained at all times.

Now, the current-carrying chip plates 15L and 15R are both in contact with the wire at a length l, and the welding current I from the power source 6 is applied.
It has the function of dividing the current into both wire currents IL and IR. To explain the action of the two current-carrying chip plates 15L and 15R, for example, only the one on the right side, the current density distribution 19 is such that the wire tip side is higher in the length section l, as shown in the attached image in FIG.
It will have . Therefore, a slight voltage drop V _R proportional to I _R ·r occurs in the current-carrying chip 15R due to its specific resistance r between both ends of the length section l, and of course this also applies to the left-side current-carrying chip 15L. V _L
It appears as a voltage drop of (∝I _L・r).

In this device, these voltage drops V _R (∝I _R・r),
The wire currents I _R and I L are measured by detecting V _L (∝I _L・r), respectively, and the wire currents I R and I _L are measured so that these V _R and V _L are kept equal under constant arc length control. The drive mechanism 9 moves the block 7, that is, the parallel welding wires 2L, 2R, in the width direction of the groove, thereby achieving groove tracing.

This will be explained in detail using the control block shown in FIG. 4 as follows.

Now, let's take as an example the case where the welding power source 6 is of DC constant voltage characteristics and feeds the welding wires 2L and 2R at a constant speed at the same time, for example, normal MIG or CO ₂ gas shield welding, as shown in Fig. 4. The constant arc length control circuit 20 includes a detector 21 that detects the welding current I, a long-period low-pass filter 22 whose cut-off frequency is several Hz or less, and an amplifier 23.
A differential amplifier 25 that suppresses the responsiveness to minute and steep changes via a differential amplifier 25 that compares the detected welding current value with a reference value from the setting device 24 and outputs the deviation thereof.
and a driver 26 that drives the lifting drive motor 13 according to this deviation, and controls the electrode tip 5 to move up and down by the motor 13 so that the deviation from the reference value becomes zero in response to changes in the welding current I. The wire protrusion length is adjusted so that the arc length is always kept constant despite the vertical height fluctuations of the groove.

If the welding power source 6 has DC constant current (dripping) characteristics or AC drooping characteristics, the wire feed is controlled at variable speed to keep the arc voltage constant, and the detector 21 uses the welding current I instead of the welding current I. What is necessary is to detect this wire feeding speed _Vf .

On the other hand, the copying control circuit 30 for copying in the groove width direction is configured to control each energized chip plate 15 as described above.
Micro voltage detectors 31L and 31R detect voltage drops V _L and V _R at both ends of L and 15R, respectively, and a low pass filter 32 with a cutoff frequency of several Hz, for example, for removing noise from the outputs of both detectors 31L and 31R.
A differential amplifier 34 receives signals via L, 32R and amplifiers 33L, 33R, and outputs the deviation between the two.
and a first offset setter 3 for correcting a deviation output from the differential amplifier 34 to zero when the electrode tip 5 is at the groove center position.
5 and a differential amplifier 36, and a second one that provides a desired offset amount to the output of the differential amplifier 36 for the purpose of shifting the scanning center for distributing each layer bead to the left or right in multilayer welding. It comprises a combination of an offset setter 37 and a differential amplifier 38, and a driver 39 for driving the copying drive motor 11 in forward or reverse rotation according to the output of the differential amplifier 38.

Tracing control by such a control system is performed as follows. Now, if both wires 2L and 2R are fed at the same speed and both are under constant arc length control, when the center between both wires and the groove center match, both wires 2L and 2R The deviation of the currents I _L and I _R , that is, the output of the differential amplifier 34 becomes zero. However, in reality, a slight deviation output may occur from the differential amplifier 34, and the combination of the first offset setter 35 and the differential amplifier 36 corrects this.

In this way, adjustment is made in advance so that the output of the differential amplifier 36 becomes zero when it is at the center position, and the center position of the control system is achieved.
Next, if the center between both wires 2L and 2R shifts, for example, to the right of the groove center (to the right in FIG. 1), the current balance of both wires will be disrupted, and I _R > I _L.
A deviation signal corresponding to the difference ΔI=I _R -I _L appears at the output of the differential amplifier 36. This deviation signal is differenced from the offset value corresponding to the layer distribution amount by the second offset setter 37 in the next stage amplifier 38, and is input to the driver 39 as the deviation amount from the center position according to the layer distribution amount. Ru. The driver 39 drives the copying drive motor 11 according to this input,
The electrode tip 5 is returned to the left (to the left in FIG. 1) so that the difference between the currents I _L and I _R of both wires is canceled by an amount corresponding to the amount of deviation. The situation is almost the same even when the center between the two wires is shifted to the left with respect to the groove center, except that the polarity of ΔI is reversed, so that the drive motor 11 is rotated in the opposite direction.

〔Effect of the invention〕

As described above, according to the present invention, when performing groove position tracing control under constant arc length control using parallel welding wires, the welding current flowing through each welding wire is Since the voltage drop is detected as a voltage drop at both ends of the same wire length section of the chip board, there is very little noise included in the detected value and accurate control can be performed. Furthermore, the structure around the welding electrode can be made extremely compact.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is an enlarged vertical sectional view of an electrode chip, FIG. 3 is a plan view of the electrode chip, and FIG. 4 is a control block diagram. 1... Welding base material, 2L, 2R... Welding wire, 4...
Wire feeding motor, 5... Electrode tip, 6... Welding power source, 7... Electrode support block, 8... Electrode tip lifting mechanism, 9... Copying drive mechanism, 10... Welding cart, 11
...Copying drive motor, 13...Elevating drive motor, 16
...Housing, 15L, 15R...Electricity chip board,
17... Explosive means, 18L, 18R... Wire passing hole, 20... Constant arc length control circuit, 21... Detector,
22... Long period low pass filter, 24... Reference value setter, 25... Differential amplifier, 26... Driver, 30
...Copying control circuit, 31L, 31R...Minute voltage detector, 32L, 32R...Low pass filter, 34,
36, 38... Differential amplifier, 35... First offset setter, 37... Second offset setter.

Claims (1)

[Claims] 1. A pair of parallel welding wires that are simultaneously fed to the welding groove in parallel in the groove width direction at the same speed, and the same welding power source that simultaneously energizes the electrode tips of the parallel welding wires; a moving device having a movement mechanism in the vertical and groove width directions for moving the parallel welding wire along the welding groove, a common housing through which the parallel welding wire passes through the electrode tip in sliding contact; , a current-carrying chip plate that is made of the same material and the same length and is elastically pressed against each parallel welding wire with equal contact pressure within the housing, and each current-carrying chip plate and the common It is characterized by comprising a wire passage hole consisting of a V-shaped contact groove for each welding wire formed in the housing, and means for detecting a voltage drop at both ends of a mutually equal wire length section in the current carrying chip plate. arc welding equipment.