JPH05131271A - Contactless type instrument for measuring feed speed of welding wire - Google Patents

Abstract

PURPOSE:To exactly measure the moving speed of a consumable electrode for welding and a welding wire stably with lapse of time without contact. CONSTITUTION:Magnets 6a, 6b are disposed to face each other in the form of holding the welding wire 7 in its cross sectional direction. Magneto-resistance elements 1a, 1b which change the electric resistance values according to a change in magnetism are installed between these magnets 6a, 6b and the welding wire 7. The electric resistance of the magneto-resistance elements 1a, 1b is converted to an electric signal by a measuring circuit 2 and this electric signal is converted by a conversion circuit 3 to a speed signal which is displayed with a display circuit 4. A constant correcting circuit 5 applies the correction signal corresponding to the kind of the welding wire 7 and ambient temp. to the circuits 2, 3 which in turn correct the conversion constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed rate measuring device for a consumable electrode or a welding wire.

[0002]

2. Description of the Related Art Generally, in automatic arc welding, a consumable electrode is continuously fed, and an arc is ignited by a voltage supplied from a welding power source at the fed consumable electrode tip for welding. Carry out. Here, when the output characteristic of the welding power source is a constant voltage characteristic, the welding current is fed so that a constant arc length is maintained with the consumable electrode being fed at a constant speed and the consumable electrode melting amount melted by the arc. An electric current proportional to the speed flows. Therefore, it is well known that the feed rate of the consumable electrode is directly related to the welding conditions and is an important factor in determining the welding quality. Also TI
In non-consumable electrode welding such as G welding or plasma welding, welding is performed while forming a weld metal by continuously or intermittently supplying a welding wire as a filler material into an arc.

Therefore, it goes without saying that the feed amount of the welding wire is an important factor in forming the welding joint.
Since the excess or deficiency of the supply amount of the consumable electrode or the welding wire causes the occurrence of welding defects such as undercut and overlap, it is important to maintain an appropriate supply amount in order to form a sound welding joint. It is a factor. Generally, the consumable electrode or the welding wire is fixed by sandwiching the consumable electrode or the welding wire with two or a plurality of pressure rollers, and rotating one of the rollers by an electric motor. It is usually sent by speed. For this constant speed feeding, it is necessary to measure the moving speed of the consumable electrode or the welding wire.

As a method of measuring the moving speed of the consumable electrode or the welding wire, a consumable electrode or a welding wire being fed is contacted with a rotatable roller, and the feeding speed of the consumable electrode is determined from the number of revolutions of the roller. Or the applied voltage or armature voltage of the feed motor is measured, converted to the motor rotation speed, and further converted to the rotation speed of the roller that feeds the consumable electrode or welding wire. A method for calculating the feed rate of an electrode or a welding wire is already known.

[0005]

However, in these conventional methods, a speed smaller than the actual moving speed is detected by the slip due to the deviation of the contact angle of the roller with respect to the feeding direction or the decrease of the contact pressure, and the negative measurement is performed. It causes an error. Further, since it is a contact type, a speed higher than the actual moving speed is detected due to the wear and deformation of the speed measuring roller over time, which causes a positive measurement error. Alternatively, in the above-described calculation of the moving speed based on the feed motor applied voltage or the armature voltage, particularly when the welding wire diameter is small, the radius of curvature of the wire itself is small, and thus the contact area with the pressure roller is small. If the roller pressure is increased more than necessary, the consumable electrode or the welding wire may buckle during feeding. When the feeding speed is high, slipping is likely to occur at the pressure feeding roller, and a speed higher than the actual moving speed is detected, which causes a positive measurement error. As described above, these conventional methods for measuring the feed rate of the contact welding wire have a problem that the feed rate cannot be accurately measured.

A speed measuring method for obtaining a speed by using a laser beam to measure the time difference caused by the Doppler effect of the reflected light reflected by the object to be measured is already known, but this method oscillates the laser light. However, the welding wire must be radiated toward the most prominent part of the circular surface, that is, toward the center axis of the wire. There is also a problem that it is extremely difficult to always maintain the irradiation optical axis on the straight line that passes through the center of.

The present invention controls the heat input during welding and the accurate control of the amount of deposited metal to improve the welding quality simply and inexpensively. Therefore, the moving speed of the consumable electrode for welding and the welding wire can be accurately measured without contact. The purpose is to measure.

[0008]

DISCLOSURE OF THE INVENTION The present invention is an apparatus for measuring the moving speed of a consumable electrode or a welding wire in a non-contact manner using an eddy current, and narrowing the consumable electrode or the welding wire in the cross-sectional direction. Measuring circuit for converting the electric resistance of the magnetoresistive element into an electric signal level by disposing the magnetoresistive element between at least one of the magnets and the consumable electrode or the welding wire in such a manner that the magnets face each other. It is characterized by comprising a conversion circuit for converting a level into a moving speed, a display circuit for displaying the moving speed, and a correction circuit for correcting a conversion constant from the electric resistance to the moving speed.

[0009]

Since the magnets are arranged so as to face each other in the transverse direction of the consumable electrode or the welding wire so as to narrow it, the consumable electrode or the welding wire moves in the direction orthogonal to the magnetic flux generated by those magnets. Due to this movement, an eddy current is generated in the consumable electrode or the welding wire in proportion to its moving speed, and this eddy current generates a magnetic flux. A combined magnetic flux of the magnetic flux generated by the magnet and the magnetic flux generated by the eddy current is added to the magnetoresistive element, and the intensity of the combined magnetic flux corresponds to the moving speed of the consumable electrode or the welding wire. By the way, since the resistance value of the magnetoresistive element corresponds to the magnetic flux density as shown in FIG. 3, for example, the resistance value of the magnetoresistive element corresponds to the moving speed of the consumable electrode or the welding wire.

The measuring circuit converts the electric resistance of the magnetoresistive element into an electric signal level, the converting circuit converts the electric signal level into a moving speed, and the display circuit displays the moving speed.
Depending on the size, material, temperature, etc. of the consumable electrode or welding wire, the correlation between the moving speed of the consumable electrode or welding wire and the electric signal level generated by the measurement circuit differs, but the correction circuit determines the conversion constant corresponding to each correlation. Therefore, it is suitable for applications in which the size, material, temperature, etc. of the consumable electrode or welding wire are selected or changed.

As described above, since the moving speed of the consumable electrode or the welding wire is detected without making contact with the consumable electrode or the welding wire, a measurement error due to a slip or the like does not occur. In addition, the moving speed of the consumable electrode or the welding wire can be accurately and stably obtained without increasing the error with time due to mechanical wear or deformation. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0012]

1A shows an embodiment of the present invention, and FIG. 1B shows an enlarged perspective view around the speed detection sensor shown in FIG. The non-contact welding wire feeding speed measuring device shown in FIGS. 1 (a, b) is composed of magnetoresistive elements 1a, 1c, 1
b, 1d, a measurement circuit 2 for measuring the electric resistance of the magnetoresistive elements 1a to 1d, a speed signal conversion circuit 3, a speed display circuit 4,
It is composed of a constant correction circuit 5 and exciting magnets 6a and 6b. The magnets 6a and 6b for excitation are the consumable electrodes 7
(Or welding wire, the same applies to the following), the magnetoresistive element 1 is opposed to each other in a direction orthogonal to the moving centerline.
a and 1c are arranged between the moving center line of the consumable electrode 7 and the magnet 6a, and the magnetoresistive elements 1b and 1d are arranged between the moving center line of the consumable electrode 7 and the magnet 6b.

The magnetoresistive elements 1a to 1d exhibit an electric resistance corresponding to the moving speed of the consumable electrode 7 according to the principle described below. That is, as is already known, an induced current, that is, an eddy current i (FIG. 1) that flows through the conductor (consumable electrode 7) in a direction orthogonal to the moving direction of the conductor and the magnetic field due to the relative movement across the magnetic field. 1 b) occurs. The magnitude of this eddy current i depends on the fact that the following electromotive force e is generated in the conductor when the conductor traverses the magnetic field of the magnetic flux density B (Wb / m ² ) at the velocity of V (m / s) or frequency f. .. e = α · B · V or e = β · B · f (α and β are proportional constants).

If the electric resistance of the conductor is r, the eddy current i
Can be expressed as i = α · B · V / r or i = β · B · f / r. That is, the eddy current i is proportional to the speed V.

Due to the eddy current i proportional to the speed V,
A magnetic flux is generated in a direction orthogonal to the center line of the consumable electrode 7, and the direction is opposite to the magnetic flux generated by the magnets 6a and 6b on the upstream side in the moving direction of the consumable electrode 7 (b in FIG. 1) and is on the downstream side. The direction is the same on the side. A magnetic field (composite magnetic field) based on a combined magnetic flux of the magnetic flux generated by the magnets 6a and 6b and the magnetic flux generated by the eddy current i is applied to the magnetoresistive elements 1a to 1d. The strength of this composite magnetic field corresponds to the eddy current i. That is, it corresponds to the speed V. The electric resistance of the magnetoresistive elements 1a to 1d is shown in FIG.
It corresponds to the magnetic flux density applied to them as shown in. That is, the electric resistances of the magnetoresistive elements 1a to 1d correspond to the speed V, and if V in the eddy current i = α · B · V / r in the above equation becomes large, the eddy current i becomes large. Therefore, the magnetic field around the magnetoresistive elements 1a and 1b is small,
As the magnetic field around 1d increases and the velocity V increases, the electric resistance of the magnetoresistive elements 1a and 1b decreases and the electric resistance of the magnetoresistive elements 1c and 1d increases. Therefore, by measuring the electrical resistance of at least one of the magnetoresistive elements 1a to 1d, the consumable electrode 7 and the magnetoresistive element 1a can be measured.
It is possible to measure the relative speed V between 1d, that is, the moving speed of the consumable electrode 7 without contact.

In FIG. 2A, magnetoresistive elements 1a to 1d are provided.
The structure of the measurement circuit 2 to which is connected is shown. In this example, a bridge having the magnetoresistive elements 1a to 1d as each side is configured. For example, assuming that the magnetoresistive elements 1a to 1d have the same resistance value when the magnetic field is zero and also show the same resistance value at the same magnetic field strength, when the moving speed of the consumable electrode 7 is zero, Since the resistance values of the respective sides of the bridge are the same, the potential at the point a and the potential at the point b are the same, and the amplifier 2a
The output level of is a base value (for example, zero). Consumable electrode 7
1 moves at the speed V in the direction indicated by the arrow in FIG. 1B, an eddy current i having a magnitude corresponding to the speed V flows through the consumable electrode 7, and the resistance value of the magnetoresistive elements 1a and 1b becomes the speed V. The resistance value of the magnetoresistive elements 1c and 1d rises to a value corresponding to the speed V. This allows point a (Fig. 2
Of the amplifier 2a.
Output level rises to a level corresponding to the speed V.

When the speed V of the consumable electrode 7 increases, the resistance values of the magnetoresistive elements 1a and 1b further decrease, the potential at the point a further decreases, and the resistance values of the magnetoresistive elements 1c and 1d further increase and b The potential at the point further rises, and the output level of the amplifier 2a further rises. In this way, the amplifier 2a outputs a voltage that directly corresponds to the speed V of the consumable electrode 7.

The amplifier 2a of the resistance measuring circuit 2 for the magnetoresistive element has a variable amplification factor, and the constant correction circuit 5 corresponds to the kind (material: resistance value) of the consumable electrode 7 and the ambient temperature.
In order to correct the error due to these differences, a signal indicating the amplification factor is given to the amplifier 2a. This allows the amplifier 2
The a outputs a signal that does not substantially include an error due to the type (material) of the consumable electrode 7 and the change in ambient temperature.

This signal is given to the speed conversion circuit 3.
The level of the signal output by the amplifier 2a is the magnetoresistive element 1
The magnetic resistance element 1c, which is substantially inversely proportional to the resistance values of a and 1b,
Although it is substantially directly proportional to the resistance value of 1d, since it is a non-linear function with respect to the moving speed V of the consumable electrode 7, the speed conversion circuit 3
Converts the signal output from the amplifier 2a into a speed signal whose level (data in the case of digital processing) is proportional to the speed. The speed conversion circuit 3 is, for example, an A / D converter for converting the output signal of the amplifier 2a into a digital signal and its digital data.
A memory having an input / output conversion function for converting the data into speed data for each type (size: diameter) of the consumable electrode 7, and
It includes a D / A converter for converting speed data into an analog signal. The constant correction circuit 5 responds to the type (size: diameter) of the consumable electrode 7 and, in order to correct the error due to the difference, outputs a signal designating the type (size: diameter) of the consumable electrode 7 to the speed conversion circuit 3. Give to. As a result, the speed conversion circuit 3
Selects an input / output conversion function corresponding to the type (size: diameter) of the consumable electrode 7 and converts the signal output from the amplifier 2a into a speed signal.

The speed conversion circuit 3 outputs a speed signal to the display circuit 4, and the display circuit 4 displays the speed V indicated by the speed signal. The speed display circuit 4 is a circuit for displaying the speed of the welding wire by, for example, an analog display using a voltmeter, or a digital display for directly displaying a numerical value, and is constituted by circuits such as an amplifier and an AD converter as necessary. The speed is displayed.

In FIG. 1, the magnets 6a and 6b for excitation are simply magnets, but for example, electromagnets are used, and the magnetic fluxes pass through the magnetoresistive elements 6a and 6b and the consumable electrode 7 with a core having a good magnetic permeability. A magnetic circuit may be used.

Further, although four magnetoresistive elements 1a to 1d are used and the measuring circuit 2 uses the magnetoresistive elements 1a to 1d as the respective sides of the bridge circuit as shown in FIG. As shown in FIG. 2B, for example, only two elements (for example, 1a and 1b) are used as the measuring circuit 2 and two resistors are used as two sides of the bridge circuit, and the other two sides have a fixed resistance value R.
It may be a or Rb. Further, only one magnetoresistive element (for example, 1c) may be provided, and the measurement circuit 2 may be a circuit for detecting the voltage of one magnetoresistive element 1c, for example, as shown in (c) of FIG. In short, if the magnetoresistive element can detect the magnetic field due to the eddy current generated by the relative movement between the consumable electrode 7 (or the welding wire) and the magnetic field intersecting, even one magnetoresistive element need not be combined in a bridge shape. I don't care.

-Experimental Example- The apparatus shown in FIG. 1 (and FIG. 2b) was attached to a consumable electrode type gas shield welding apparatus, and the moving speed of the welding wire (7 counterpart) was measured. The magnetoresistive elements 1a and 1b are elements having 100Ω in the absence of a magnetic field, and the resistors 2a and 2b in FIG. 2B used known resistors of 100Ω. A DC voltage of 5 V was applied to the bridge circuit shown in FIG. 2B as an applied voltage and measurement was performed. The welding wire is JIS Z 3312 Y with a wire diameter of 1.2 mm.
A GW12 equivalent product was used.

As a comparative example, the speed of the welding wire was measured by a method of pressing a welding wire feed rate measuring device using a hand-held rotary encoder against the feed wire. The result was 1.0 m / at the exit of the welding wire feeder.
min, 15.0 m / min, and 30.0 m / min
Was a speed indicating. In these wire feeds, according to the device of the present invention (FIG. 1), the same value was shown when the welding wire feed speed was 1.0 m / min, but 15.0.
In the case of m / min and 30.0 m / min, it was displayed as 15.55 m / min and 31.08 m / min, respectively.

Therefore, the inventors of the present invention measured the same method as above and fed the welding wire for 15 seconds, and measured the fed welding wire with a tape measure of 50 m. 1.0m /
In the case of min, the measured length is 0.25 m and 15.0 m /
In the case of min, it is 3.89 m and 30.0 m / mi
In the case of n, it was 7.77 m. Therefore, when converted per minute, 1.0 m / min and 15.56, respectively.
It was found that the error was larger in the comparative example as the feeding speed became higher, with m / min and 31.08 m / min.

Next, using the device of the present invention (b in FIGS. 1 and 2), the speed signal is given as a feedback signal to the wire feeding control device of the welding device to perform constant speed wire feeding. Welding was performed. JIS Z as a consumable electrode
3312 YGW12 equivalent, wire diameter 1.6 mmφ,
Carbon dioxide gas is used as a shield gas, and the plate thickness is 4.5 mm,
One groove, groove gap 2 mm, welding length 1 m, downward butt welding was performed at a welding speed of 80 cm / min. At this time, the consumable electrode feed rate was 9.0 m / min, the welding current was 280 A, and the voltage was 29 V, which was stable. After the completion of welding, no welding defects that could be confirmed by visual observation were observed on the surface of the weld joint, and the surplus height was 1.2 mm on average and stable. An X-ray transmission test was carried out as a non-destructive test, and no internal defects were observed over the entire weld length line, confirming that the weld joint was sound.

As described above, in the comparative example, 0.56 m / mi when the welding wire feeding speed is about 15 m / sec.
There is an error of n, and when converted into a welding current by an error of the feeding speed, the welding wire described in the above embodiment has about 15 A.
It became clear that there was a difference in the current value. Therefore, it is understood that there is a big difference in managing the heat input of welding or the amount of deposited metal. That is, in the conventional example, the welding current is large and the heat input is high as the true welding wire feeding speed is high.
Therefore, there is a possibility that mechanical properties such as impact resistance may be deteriorated, especially in high-strength steel having heat input restriction. Alternatively, as the feeding speed of the welding wire is higher, the amount of deposited metal is larger and the surplus height is higher, which makes it difficult to keep the welding quality uniform. Therefore, if welding is performed using the welding wire feed rate measuring device according to the present invention, a sound welding joint can be produced easily and inexpensively, and the welding quality can be improved and evenly changed.

Further, the present invention is applied to the speed conversion circuit 3 in FIG.
If the configuration is such that the average value of a certain period of time can be obtained using the signal from, even in the case of intermittent feeding as one of the feeding methods of the additive wire used when performing non-consumable electrode welding, for example. It is possible to easily know the average feed amount of the welding wire per time or per welding length.

As described above, the present invention provides a wire feeding speed measuring device for welding which has an extremely high industrial value.

[0030]

As described above, according to the present invention, since the moving speed of the consumable electrode or the welding wire is detected without making contact with the consumable electrode or the welding wire, a measurement error due to slip or the like does not occur. In addition, the moving speed of the consumable electrode or the welding wire can be accurately and stably obtained without increasing the error with time due to mechanical wear or deformation.

[Brief description of drawings]

FIG. 1A is a block diagram showing an embodiment of the present invention, and FIG. 1B is an enlarged perspective view around a speed detection sensor shown in FIG.

2A is a block diagram showing the configuration of the measurement circuit 2 shown in FIG. 1A, FIG. 2B is a block diagram showing another configuration of the measurement circuit 2, and FIG. It is a block diagram which shows one structure.

FIG. 3 is a graph showing the resistance value of the magnetoresistive element shown in FIG. 1 with respect to the magnetic flux density.

[Explanation of symbols]

1a, 1b, 1c, 1d: Magnetoresistive element 2: Resistance value measuring circuit for magnetoresistive element 2a, 2b: Amplifier of variable amplification factor 3: Speed signal conversion circuit 4: Speed display circuit 5: Constant correction circuit 6a, 6b: Magnet 7: Consumable electrode or welding wire Ra, Rb: Resistor with fixed resistance

Claims (1)

[Claims] 1. A device for measuring the moving speed of a consumable electrode or a welding wire in a non-contact manner by using an eddy current, wherein magnets are arranged so as to face each other in a cross-sectional direction of the consumable electrode or the welding wire. A measuring circuit that installs a magnetoresistive element between at least one magnet and a consumable electrode or welding wire to convert the electric resistance of the magnetoresistive element into an electric signal level, and a conversion circuit that converts the electric signal level into a moving speed. circuit,
A non-contact type wire feeding speed measuring device comprising a display circuit for displaying the moving speed and a correction circuit for correcting a conversion constant from the electric resistance to the moving speed.