JPS583044Y2 - Ichikenshiyutsusouchi - Google Patents

Description

[Detailed description of the invention] This invention is equipped with a high-frequency oscillator and an oscillation coil excited by the oscillator, and uses the oscillation coil as a detection section to determine the relative position of the metal to be detected, such as iron or aluminum, and the detection section. This relates to a position detection device that detects the relative position to the metal to be detected by utilizing the fact that the oscillation amplitude changes depending on the relationship.For example, it is used in automatic welding machines for contactless metal distance tracing or edge tracing devices. It is used for.

Conventionally, magnetic and optical methods have been considered as methods for performing non-contact tracing operations on metal workpieces in automatic machines.

However, both the magnetic type and the optical type have the disadvantage that the detection section is large, complicated, and expensive.

Furthermore, when performing distance tracing using an optical method, there is a drawback that if there is color unevenness on the detection surface, it may cause errors.

In addition, a proximity switch was previously considered as a non-contact distance detector, but this outputs an on/off signal that outputs a certain output (relay output) when the detector approaches within a certain distance from the metal surface to be detected. However, it is difficult to perform high-precision tracing (within ±9.5 mm) as it is.

In order to solve the above-mentioned drawbacks of the conventional methods, the following detection devices have been proposed.

This will be explained with reference to the diagram.

Figure 1 explains the principle of this position detection device.
2 is a metal to be detected, and 2 is an oscillation coil provided close to the metal to be detected 1, which is used as a detection section.

Reference numeral 3 is an AC power source that excites the oscillation coil 2, and a soft oscillation type high frequency oscillator is generally used.

Now, a high frequency current of about 500 KHz is passed through the oscillation coil 2, and when the metal to be detected 1 approaches the oscillation coil 2, an eddy current flows in the metal due to electromagnetic induction, and this eddy current changes the magnetic flux produced by the oscillation coil 2. This effectively reduces the impedance of the oscillation coil 2.

In FIG. 1, the magnetic flux B from the coil 2 is applied to the metal 1 to be detected.
, the eddy current flows along the circumference of the metal surface from the center O to the radius r.

The magnetic flux φ penetrating perpendicularly to the surface is φ= yr r 2
B = yr r 2BmSinωt-1------(
1) However, Bm: maximum value of magnetic flux density, ω: angular frequency (=2
πf), f: power supply frequency.

Therefore, the induced voltage due to this magnetic flux is, and since the eddy current generated by this voltage is distributed in the metal body, when integrated with respect to r, the total eddy current ie
where δ is the thickness of the metal conductor, and P. is the volume resistivity of the metal conductor.

This eddy current generates a magnetic flux φe whose magnitude decreases as φ increases, ie, in the direction opposite to φ, which effectively reduces the impedance of the coil 2.

□ ・ ・ “If the effective impedance of the oscillation coil 2 changes in this way, the oscillation amplitude of the soft oscillation type high-frequency oscillator 4 will change.

FIG. 2 shows how the oscillation amplitude changes when the metal to be detected 1 is brought close to the oscillation coil 2□.

If we rectify this signal and take out the difference signal from the reference voltage at a constant level (for example, the voltage corresponding to A in Figure 2), we get A
If the actual distance l' between the detected metal 1 and the oscillation coil 2 corresponds to i'> i, a positive (or negative) analog signal is output; A negative (a certain U is positive) analog signal is output.

FIG. 3 is a block diagram of this position detection device that performs the above-mentioned operation, in which J is the metal to be detected, 2 is an oscillation coil, 4 is a soft oscillation bulk frequency oscillator, 5 is a DC amplifier, 6 is a differential amplifier, and 7
is a constant voltage source that generates a reference voltage.

□゛That is, the configuration shown in Figure 3 is the metal to be detected 1.
The oscillation amplitude of the oscillator 4, which changes depending on the relative position of the oscillation coil 2, is amplified by a DC amplifier 5, and a part of this amplified output and a reference voltage from a constant voltage source 7 is used by a differential amplifier 6. Detect and extract positive and negative analog signals according to the difference.

□Figure 4 shows the difference l'-1=ε between the distance l between the detected metal '1 corresponding to the reference voltage and the oscillation coil 2 and the actual distance l'.
FIG. 2 is a characteristic diagram showing the relationship between ε□ and the output signal.

-□ ゛This is an example in which the detection device shown in Fig. 1 is applied to distance tracing of a metal to be detected.

'□In Fig. 5, 8 is a detector including a differential amplifier, a constant voltage source, etc. The positive or negative output signal of this detector drives the firing circuit 9 and controls the firing of the thyristor 10 or thyristor 11. death.

The DC motor 12 can be rotated forward or reverse.

Using the rotation of this motor 12, the oscillation coil 2 of the detection section
is kept at a constant distance from the metal to be detected 1.

FIG. 6 shows an example in which this detection device is applied to edge tracing.

The motor drive circuit is the same as that used for distance scanning shown in FIG.

The oscillation coil 2 of the detection section is l.

By setting the reference voltage so that the output of the detector 8 is 0 when the detector 8 is at the position, the output of the detector 8 becomes a positive or negative analog signal for the areas 11 and 12.

Using this signal, the detection section 1. The motor is driven to trace the edge.

As mentioned above, this position detection device has a very small and lightweight detection unit (length 60 mm, diameter 39 mm, weight within 100 g).
Therefore, the detection section can be easily supported.

Furthermore, even if there is dirt such as oil or dust on the surface of the metal to be detected, the scanning accuracy will not be affected, and malfunctions will not occur due to arc noise or high frequency noise generated by a welding machine or the like.

Furthermore, since positional deviations can be detected continuously, highly accurate copying is possible.

However, in general, the metal to be detected during welding 1 becomes high in temperature due to heat conduction from the molten pool during welding, or becomes high in temperature due to preheating to prevent cracking after welding. When the detected metal 1 is traced by the above-mentioned "detection device," the detection section is also heated to a high temperature by the radiant heat of the detected metal 1 and the radiant heat from the arc, and the oscillating coil 2
impedance changes somewhat.

As a result, an error occurs in distance tracing.Also, when performing submerged welding, a part of the wire or cut wire may overlap the surface of the metal to be detected 1, and the above-mentioned detection device cannot detect it. This causes an error in distance tracing.

- This invention was made by paying attention to the above-mentioned drawbacks, and a fluid cooler 13 is provided in the oscillation coil 2 as shown in FIG.

This fluid cooler 13 is composed of a cover 133 that covers the periphery of the oscillation coil 2 and a plurality of fluid blowout pipes 13b provided at appropriate parts of the cover 138, and is connected to the cover 13a through the pipe 13b. The oscillation coil is cooled by vigorously blowing out fluid such as air from between the oscillation coil 2 and the oscillation coil 2.

Also, flux15 generated in submerged arc welding
Alternatively, the cut wire or the like is blown away to prevent the flux or the cut wire from adhering to the surface of the metal to be detected 1.

In addition, in the figure, 14 is a spring washer.

As described above, according to this invention, a fluid cooler is installed in the detection device that detects the oscillation amplitude of the oscillator, which changes depending on the relative position of the oscillation coil and the metal to be detected, and extracts the position of the oscillation coil as an analog signal. Even when tracing high-temperature metals to be welded during welding, etc., and even in submerged arc welding, there is no error in distance tracing, and position detection can be performed with high accuracy.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the principle of the position detection device, FIG. 3 is a block diagram showing one embodiment of this detection device, and FIG.
The figure is a characteristic diagram showing the relationship between error and detector output, Figures 5 and 6 are block diagrams showing application examples of this detection device, and Figure 7 is a sectional view showing one embodiment of this invention. . Note that the same reference numerals in the figures indicate the same or corresponding parts. 1 is a metal to be detected, 2 is an oscillation coil, 4 is a high frequency oscillator,
5 is a DC amplifier, 6 is a differential amplifier, 7 is a constant voltage source, 8 is a detector, and 13 is a fluid cooler.

Claims (1)

[Scope of utility model registration request] An oscillation coil provided facing the metal to be detected, a high-frequency oscillator that excites this oscillation coil, and an oscillation amplitude of the oscillator that changes depending on the relative position of the oscillation coil and the metal to be detected is detected and the position of the oscillation coil is converted into an analog signal. In a position detection device equipped with a detector to be taken out, a fluid cooler is provided, and the cooler cools the fluid by passing it around the oscillation coil, and further sprays the fluid onto the surface of the metal to be detected. A position detection device characterized in that the surface is cleaned.