JPH07109433B2 - Inductive conductor detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a detector for detecting molten metal or the like in a non-contact manner, and more particularly to an inductive conductor utilizing electromagnetic inductive coupling between a primary coil and a secondary coil. Regarding the detector.

[Prior Art] Conventionally, as a detector for detecting a substance having conductivity, such as a liquid, in a non-contact manner, a detector as shown in the attached FIGS. 7 and 8 is known. This detector has a primary coil 1
Two secondary coils (detection coils) 2 and 2 are vertically mounted above and below, and are induced by the two secondary coils 2 and 2 connected in series while applying an AC signal to the primary coil 1. It detects a conductor using a signal.

Further, generally, as a molten metal detector, as a coil material for use in a high temperature state, a conductor is housed inside a stainless steel sheath, and an insulating material such as magnesium oxide is filled around the conductor. So-called sheath cables are known.

[Problems to be Solved by the Invention] However, in the non-contact conductor detector according to the above-mentioned prior art, when a molten metal or the like is detected by this, since a sheath cable having high impedance is used for the coil, high frequency Could not be detected using
High sensitivity cannot be obtained with a small number of turns. Further, if a temperature difference occurs between the detection coils vertically mounted on the upper and lower sides, erroneous detection due to the temperature difference may occur, so that accurate detection cannot be performed without contacting the conductors.

Therefore, in the above-mentioned conventional technique, sufficient sensitivity cannot be obtained as a non-contact conductor detector, and for example, there is a problem that the detector has to be housed and immersed in a protective container inside a conductor to be detected. . Furthermore, even if you do so,
There was a problem that the conductor could not be detected accurately without contact.

Therefore, in view of the above-mentioned problems in the prior art, the present invention provides an inductive conductor detector having high sensitivity, capable of accurately detecting a conductor even without contact, and capable of detecting a high temperature conductor. The purpose is to

[Means for Solving the Problem] That is, an object of the present invention is to provide a primary coil and a plurality of secondary coils provided adjacent to the primary coil.
In an inductive conductor detector comprising an AC power supply for applying an AC signal to the primary coil, and a detection circuit for detecting and comparing the current induced in the secondary coil, a sheath cable is provided for the primary coil and the secondary coil. And the secondary coil is wound around the primary coil and the plurality of secondary coils are arranged close to each other.

[Operation] That is, according to the inductive conductor detector, by winding the plurality of secondary coils formed of a sheath cable around the primary coil, a large sensor diameter can be obtained even with a relatively small number of turns. It becomes possible. As a result, the sensitivity can be increased at a relatively low frequency. Further, as compared with the case where the secondary coils are arranged on both sides of the primary coil, the secondary coils can be brought closer to each other, so that the temperature conditions of the secondary coils can be made substantially the same. Therefore, it is possible to provide an inductive conductor detector capable of accurately detecting a conductor at high temperature without contact.

EXAMPLES Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a detection coil section of an inductive conductor detector according to an embodiment of the present invention. The detection coil section 10 comprises one primary coil 11 and a plurality of secondary coils 12, 12 '. It is configured. In particular, FIG. 1 shows that the secondary coils 12, 12 'have two
Two cases are shown.

These primary and secondary coils 11, 12, 12 'are formed by winding a so-called sheath cable 20 as shown in FIG. This sheath cable 20 has a heat-resistant insulating material 22 such as magnesium dioxide around the conductor 21 at the center.
And a sheath 23 made of stainless steel or the like covers the periphery thereof.

The primary coil 11 is wound around a coil bobbin 13 having a magnetic core 14 inserted therein, and a plurality of secondary coils 12 and 12 '.
Are wound around the primary coil 11 so as to have opposite phases to each other.

As the material of the coil bobbin 13, an insulating material such as ceramic is desirable in view of eddy current loss, but a stainless material having a relatively low conductivity may be used. However, in that case, it is desirable to reduce the eddy current loss by providing a slit or the like. The magnetic core 14 may be manufactured integrally with the bobbin 13.

The primary coil 11 and the secondary coils 12, 12 'described above
FIG. 3 shows a circuit diagram of the detection circuit 30 electrically connected to the above. As is clear from this circuit diagram, a relatively low frequency AC signal is supplied from the AC power supply 31 to the primary coil 11. On the other hand, the secondary coils 12, 12 '
Is connected to the input terminal of the differential amplifier 33 of the detection circuit 30 via the respective signal output lines 32, 32, and the differential amplifier 33 outputs a signal from its output terminal. This output signal is input to, for example, a control device for operating the actuator, an indicator or a display device, an alarm device, or the like. Further, in the above embodiment, the output signal is represented as an analog signal, but it can be converted into a digital signal by using an A / D converter or the like. Further, when the polarities of the secondary coils 12 and 12 'are opposite to those shown in the figure, it is obvious that an adder may be used instead of the differential amplifier 33.

Next, FIG. 4 shows an apparatus for non-contact detection of molten metal using the inductive conductor detector. That is,
Above the molten metal 40, the detection coil portion 10 of the inductive conductor detector is arranged at a predetermined distance h. The circumference of the detection coil unit 10 is covered with a metal shield cover 41 whose lower part is opened. Also,
The circuit portion is not shown in this figure to avoid duplication.

To explain this operation, referring to the circuit diagram shown in FIG. 3, the primary coil 11 receives an AC signal of a relatively low frequency as a power source 31.
Is supplied from a magnetic field, which generates a magnetic flux. On the other hand, 2
In the two secondary coils 12 and 12 ', a secondary voltage is induced by interlinking the magnetic flux generated by the primary coil 11, and this induced voltage is generated by the upper secondary coil 12 and the lower secondary coil 12. In the secondary coil 12 ', the induced voltage differs depending on the conductors located below. That is, in FIG. 4 above, when the molten metal 40 approaches below the lower secondary coil 12 'and h decreases, as shown in the output waveform of FIG. A difference occurs in the output voltage (dotted line B) induced and the output voltage (dotted line A) induced in the lower secondary coil 12 '. That is, the lower secondary coil
The output voltage of 12 'decreases with the proximity of the conductor. Therefore, a voltage signal (solid line C) proportional to this difference is generated at the output terminal of the differential amplifier 34. Since the voltage value correlates with the distance h to the conductor that is the substance to be measured,
The voltage value can indicate the process h.

Further, in the above-mentioned inductive conductor detector according to the present invention, by adopting a structure in which the plurality of secondary coils 12 and 12 'are wound around the primary coil 11, the plurality of secondary coils are
12, 12 'can be provided adjacent to each other, and a large temperature difference does not occur between the plurality of secondary coils 12, 12'.
That is, when the detection coil unit 10 is brought close to the surface of the hot molten metal 40, the temperature difference between the two is small. Therefore, it is possible to prevent an error caused by the difference in the coil conductor resistivity and the difference in the eddy current loss generated in the sensor structure material due to the temperature difference between the plurality of secondary coils 12 and 12 '. Further, since the sensor diameter can be made relatively large by the structure in which the secondary coils 12 and 12 'are wound around the primary coil 11, the sensitivity can be increased. That is, in an inductive conductor detector that detects the presence of a conductor using a coil,
The practical measurement range is about 50-80% of the sensor diameter. Furthermore, when a coil is formed using a sheath cable, it is impossible to increase the frequency and increase the sensitivity because the impedance is high.

FIG. 6 shows a detection device for detecting a conductor from the side wall of the container 50 containing the molten metal 40 using the inductive conductor detector. In this embodiment, a plurality of detection coil units 10, 10 ... Is attached to the outer surface of the side wall of the. That is, the detection coil units 10, 10 ... Are arranged at the positions of the conductor to be detected, and fixed point detection is performed. Also in this figure, the circuit portion is omitted in order to avoid duplication, but the configuration is the same as that of the third embodiment.

[Effects of the Invention] As is clear from the above description, according to the present invention, a high temperature conductor such as a molten metal can be accurately detected without causing an error due to a temperature difference, and this detection sensitivity is high. It is possible to provide an inductive conductor detector capable of non-contact detection.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view for explaining the detailed structure of the detection coil section of the inductive conductor detector according to the present invention, and FIG. 2 shows the details of the sheath cable used for forming the coil of the detection coil section. Partial cross-sectional perspective view, FIG. 3 is a circuit diagram showing a circuit configuration of the inductive conductor detector, FIG. 4 is a configuration diagram in the case of detecting a conductor using the inductive conductor detector, and FIG. An output operation waveform diagram for explaining the operation of the inductive conductor detector, FIG. 6 is a configuration diagram when the inductive conductor detector according to the present invention is used for fixed point detection, and FIGS. 7 and 8 are conventional. It is a block diagram and a circuit diagram for explaining a technology. 10 …… Detection coil part, 11 …… Primary coil, 12,12 ′ ……
Secondary coil, 13 ... Bobbin, 14 ... Magnetic core, 20 ... Sheath cable, 21 ... Conductor, 23 ... Sheath, 30 ... Detection circuit, 31 ... Power supply, 31 32 ... Signal take-out line, 33 ... Differential amplifier, 40 ... Molten metal

Claims (1)

[Claims] 1. A primary coil, a plurality of secondary coils provided adjacent to the primary coil, an AC power supply for applying an AC signal to the primary coil, and a current induced in the secondary coil. In the inductive conductor detector including a detection circuit to be compared, the primary coil and the secondary coil are formed of a sheath cable, the secondary coil is wound around the primary coil, and the plurality of secondary coils are wound. An inductive conductor detector characterized in that the following coils are arranged in close proximity.