JPH04122883A - Metal detection method and apparatus - Google Patents

Abstract

PURPOSE:To achieve higher operability by comparing an output signal from a balance adjusting circuit with an output signal from a detection coil as obtained when the detection coil is brought closer to an object to be detected relatively to detect not only the presence of metal but also a quantity and the number thereof. CONSTITUTION:A setting is made beforehand that an input voltage to a compara tor circuit 15 is down to OV when an instant cup noodle 8a housing a seasoning sealed container 11 approaches a detection coil 6 (imaginary point 0). When a defective instant cup noodle 8b having no seasoning sealed container 11 is conveyed for some reasons, a quantity of metal to be detected decreases. Thus, an impedance of the detection coil 6 changes to generate a voltage at the imagi nary point 0 and a signal notifying that no seasoning sealed container 11 is in the instant cup noodle 8b is outputted via the comparator circuit 15 and an output judging circuit 16.

Description

Detailed Description of the Invention (a) Field of Industrial Application The present invention relates to a method and apparatus for detecting the presence or absence of metal in an object to be detected and the amount thereof, and particularly relates to a method and a device for detecting the presence or absence of metal in an object to be detected. This is suitable for detecting the presence or absence of small metals in the presence of metals.

(B) Prior art A conventional metal detection device generally includes a bridge circuit having a detection coil and a reference coil, an oscillator that excites the bridge circuit, and an amplifier that amplifies the difference between the outputs of the two coils. and a rectifier circuit that rectifies the signal amplified by the amplifier circuit and outputs it as a detection signal.

When an object to be detected approaches the magnetic field generated by the detection coil, an eddy current is generated in the metal in the object.
The impedance of the detection coil changes due to the reverse magnetic flux generated by the eddy current.

Then, the bridge circuit becomes unbalanced, and a detection signal is output via the amplifier circuit and the rectifier circuit.

By the way, in the above-mentioned device, for example, it was not possible to detect the presence or absence of a seasoning enclosing container in a cup of noodles. The seasoning container is made of a laminate of aluminum and vinyl, so it can be detected by a metal detection device, but the opening of the cup ramen is shielded by a lid made of a laminate of aluminum and vinyl. Therefore, the metal detection device was sensitive to the large lid, making it impossible to detect the presence or absence of the seasoning enclosure.

Therefore, an inspection of the presence or absence of a seasoning enclosure in a cup of ramen had to be carried out before it was shielded with a lid, but it is desirable to carry out such an inspection in the final step.

Therefore, in addition to bringing a reference metal (for example, a cup of noodles with a built-in seasoning container) close to the magnetic field generated by the reference coil, the object to be detected (a cup with a built-in seasoning container or not) is Method and device for determining whether or not metal (seasoning container) is present in a detected object (cup ramen) by bringing a ramen noodle close to each other and measuring the difference in impedance between a reference coil and a detection coil has been proposed (see "Missing Item Inspection Device" manufactured by Kaisei Engineer Co., Ltd.).

(c) Problems to be Solved by the Invention As mentioned above, in the conventional technology, it is necessary to bring the reference metal close to the magnetic field generated from the reference coil as well as the object to be detected, which only complicates the structure. However, each part must be adjusted every time the object to be detected is changed, resulting in poor operability.

(d) Means for Solving the Problems The main invention of Ill is a method for detecting metal in an object by relatively moving the object to be detected and a detection coil to which an alternating current is applied. , a balance adjustment circuit that outputs a signal that cancels the output signal from the detection coil is provided, and the output signal from the balance adjustment circuit and the detection coil when the detected object and the detection coil are brought relatively close to each other. The present invention is characterized in that it compares the output signals from the two signals, detects the difference between the two signals, and detects the amount of metal based on the difference.

The second main invention is an object movement that moves the detected object in a device that detects metal in the detected object by relatively moving the detected object and a detection coil to which alternating current is applied. means, a detection coil provided near the moving path of the detected object, an AC applying means for applying an AC voltage to the detection coil, and a balance for outputting a signal that cancels an output signal from the detection coil. an adjustment circuit;
It is characterized by comprising a comparison circuit that compares the output signal from the balance adjustment circuit and the output signal from the detection coil to detect a difference between the two signals, and an output determination circuit that outputs the comparison result. It is something.

(e) Operation In the first major invention, the signal output from the balance adjustment circuit is compared with the output signal from the detection coil when the object to be detected and the detection coil are brought close to each other in relative directions. Since the amount of metal is detected based on the difference, the output signal of the balance adjustment circuit is adjusted so that the difference between the two signals is O when a certain amount of metal is present in the object to be detected. If this is set, the 0 point becomes non-equilibrium when an object to be detected in which the amount of metal present is less than a certain amount approaches.

Therefore, for example, if a seasoning enclosing container is not present in a cup of noodles, this state will be detected.

The operation of the second invention is not substantially different from the operation of the first invention.

(f) Embodiment The drawings all show an embodiment for realizing the method and apparatus of the present invention, and FIG. 1 is a control block diagram, FIG. 2 is a schematic configuration diagram, and FIG. 3 is a main part control circuit diagram. .

In FIG. 2, 1 is a belt conveyor as an object moving means, and an endless belt 3 made of a non-metallic material such as rubber or plastic is stretched between a pair of parallel rollers 2.2. A straight support body 4 is provided within the endless belt 3, and a detection coil 6 of a metal detection device 5 is installed in the support body 4. Note that a portion of the support body 4 corresponding to the detection coil 6 is opened lower, and the detection coil 6 is disposed close to the back surface of the endless belt 3.

Cup noodles 8a and 8b as objects to be detected are sequentially placed on the endless belt 3 and conveyed to the left in the figure. The cup noodles 8a and 8b have a maximum diameter of 1
Dried noodles 10 and a seasoning enclosing container 1 are placed in a bowl-shaped styrofoam container 9 with a diameter of 50 mm and a height of 65 mm.
1 is stored and the opening is shielded by a lid 12.

The seasoning enclosure container 11 is made by laminating vinyl and aluminum foil, and the thickness of the aluminum foil is 1.
Approximately 5μ, the total thickness is 5μ when the seasoning is encapsulated.
It is approximately 80 mm long and 65 mm wide. The lid 12 has the same thickness as the material of the seasoning container 11, and is thermocompression bonded to the opening edge of the container 9 in a peelable manner.

Further, above the endless belt 3, a detection coil 6 (described later)
A reflection-type 7-pot sensor 25 is provided at a location facing the ramen 8a8b for detecting the arrival of the cup ramen 8a8b and outputting a timing signal.

As shown in FIG. 1, the metal detection device 5 includes a detection coil 6.
, an AC applying means 13 that applies an AC voltage to the detection coil 6 , a balance adjustment circuit 14 that outputs a signal whose phase and amplitude are adjusted so as to cancel the output signal from the detection coil 6 , and the balance adjustment circuit 14 . It is comprised of a comparison circuit 15 that compares the output signal from the circuit 14 and the output signal from the detection coil 6 to detect a difference between the two signals, and an output determination circuit 16 that outputs the comparison result.

Further, the output determination circuit is connected to the seven otosensors 25, and the metal detection device 5 is connected to the cup ramen 8a,
The sensor 8b is configured to operate at the timing when the sensor 8b reaches a predetermined position, that is, a location facing the detection coil 6.

Note that the balance adjustment circuit 14 is configured so that its output signal can be made variable, that is, the phase and amplitude can be changed, so that it can be applied to various types of objects to be detected.

In this embodiment, the input voltage to the comparison circuit 15 is set to OV (virtual 0 point) when the cup ramen 8a containing the seasoning enclosure 11 approaches the detection coil 6 ). That is, while the detection coil 6 is detecting both metals of the lid 12 of the cup ramen 8a and the seasoning enclosure container 11, the input voltage to the comparator circuit 15 is Ov.
is set to be.

Therefore, when a good quality cup noodle 8a containing a seasoning enclosure 11 is transported by the endless belt 3, the metal detection device 5 does not output a signal.

However, if for some reason a defective cup noodle 8b in which the seasoning enclosure container 11 is not stored is delivered, the amount of metal detected decreases, and the impedance of the detection coil 6 changes. , a voltage is generated at the virtual zero point, and the comparison circuit 15 and the output determination circuit 1
6, a determination signal indicating that the seasoning enclosing container 11 is not stored in the cup ramen 8b is output. Therefore, the belt conveyor 1 is provided with means (not shown) for eliminating the defective cup noodles 8b, and when the eliminating means is operated based on the determination signal, the defective cup noodles 8b are eliminated. That will happen.

That is, instead of detecting the presence or absence of metal using a proximity sensor, the output signal of the balance adjustment circuit 14 and the detection coil 6
The feature is that metals are detected by comparing the output signals of the two signals and detecting the difference between the two signals.

In FIG. 3, the O of the two-phase oscillator 13 (AC generating means)
The output end on the ° side is connected to one end of the detection coil 6, and is connected in parallel to the input ends of the 0° phase detector 17 and the 90° signal multiplier 22, respectively. Further, the 90° side output end of the two-phase oscillator 13 (AC power source) is connected in parallel to the 90' phase detector 18 and the O° signal multiplier 21 input end, respectively.

The other end of the detection coil 6 is connected to the negative input end of an operational amplifier 24 , and the output end of the operational amplifier 24 is connected to the O° phase detector 17 .

The output end of the 0° phase detector 17 is connected to the input end of an integrator 19, and the output end of the integrator 19 is connected to the input end of the O° signal multiplier 21. In addition, the above 9
The output end of the 0'' phase detector 18 is connected to the integrating !200 Å power end, and the output end of the integrator 20 is connected to the input end of the 90° signal multiplier 22.

The output ends of the O° signal multiplier 21 and the 90° signal multiplier 22 are connected to each other and to the input end of a combiner 23. The output terminal of the synthesizer 23 is connected to the negative input terminal of the operational amplifier 24, and the connected portion is configured to be a virtual zero point.

Thus, the output of the 0° phase detector 17 is taken out as a 0° output signal, and the output of the 90° phase detector 18 is taken out as a 90'' output signal.

Although this embodiment detects the presence or absence of a seasoning container in a cup of ramen, it goes without saying that the present invention can be applied to any other type of metal detection.

(g) Effects of the Invention According to the present invention, a balance adjustment circuit that outputs a signal that cancels the output signal from the detection coil is provided, and the output signal from the balance adjustment circuit, the object to be detected, and the detection coil are It compares the output signal from the detection coil when brought relatively close to each other, detects the difference between both signals, and detects the amount of metal based on the difference, so it not only detects the presence or absence of metal, but also
Even the amount and number can be easily detected.

In addition, there is no need to bring the reference metal close to the magnetic field generated by the reference coil, and the output signal from the balance adjustment circuit can be changed depending on the object to be detected, which simplifies the structure and reduces costs. Not only is this possible, but it also has the effect of improving operability.

[Brief explanation of drawings]

The drawings all show embodiments for realizing the method and apparatus of the present invention, and FIG. 1 is a control block diagram, FIG. 2 is a schematic configuration diagram, and FIG. 3 is a main part control circuit diagram. DESCRIPTION OF SYMBOLS 1... Belt conveyor (object moving means), 2... Roller, 3... Endless belt, 4... Support body, 5...
Metal detection device, 6... detection coil, 7... opening, 8
a... Good cup ramen (object to be detected), 8b.
...Defective cup ramen (object to be detected), 9...
Container, 10... Dried noodles, 11... Container containing seasoning (
metal), 12... Lid body (metal), 13... AC applying means, 14... Balance adjustment circuit, 15... Comparison circuit, 16... Output determination circuit, 17... 0° Phase detector, 18... 90° phase detector, 19.20... Integrator, 21... 0° signal multiplier, 22... 90° signal multiplier, 23... Combiner, 24... operational amplifier,
25...7 Oto sensor. Patent applicant Nikka Densoku Co., Ltd.

Claims (1)

[Claims] 1. In a method for detecting metal in an object to be detected by relatively moving an object to be detected and a detection coil to which alternating current is applied, the output signal from the detection coil is driven. A balance adjustment circuit is provided that outputs a signal that erases the signal, and the output signal from the balance adjustment circuit is compared with the output signal from the detection coil when the detected object and the detection coil are brought relatively close to each other. , a metal detection method characterized by detecting a difference between both signals and detecting the amount of metal based on the difference. 2. An apparatus for detecting metal in a detected object by relatively moving the detected object and a detection coil to which alternating current is applied, comprising: an object moving means for moving the detected object; and an object moving means for moving the detected object; A detection coil provided near the movement path of the object, an AC applying means for applying an AC voltage to the detection coil, a balance adjustment circuit for outputting a signal that cancels an output signal from the detection coil, and the balance. A metal detection device comprising a comparison circuit that compares an output signal from an adjustment circuit and an output signal from a detection coil to detect a difference between the two signals, and an output determination circuit that outputs a comparison result. Device. 3. Claim 2, further comprising a detection means for detecting that the object to be detected has arrived at a predetermined position, and configured to operate based on a timing signal when the object to be detected is detected by the detection means. The metal detection device described. 4. Claim 2 or 4, wherein when the difference between the reference signal and the output signal from the detection coil is equal to or greater than a certain value, a signal indicating that metal that should be present in the detected object is not present is output. The metal detection device according to claim 3. 5. The metal detection device according to any one of claims 2 to 4, wherein a large metal and a small metal are present in the object to be detected, and the metal detection device is configured to detect the presence or absence of the small metal. .