JP2012083137A - Metal detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately identify a detection sensitivity of metal detection, regardless of the size of an object to be checked, while reducing influences of noise or the like in relatively simplified configuration.SOLUTION: A metal detection method of claim 1 is used while employing a magnetic sensor coil of claims 2 to 5, so that influences of noise or the like can be reduced by simple components and further a detection sensitivity of metal detection can be improved regardless of the size and the weight of an object to be checked. Moreover, in the case where two detection units are provided between magnetic field generation means and the check object, influences of a package of aluminum foil or the like upon the magnetic field generation means can be cut. Furthermore, according to claims 4 and 5, a detection area is reduced as further as possible, thereby reducing influences of noise or the like and a need to connect any special circuit in a complicated manner is eliminated.

Description

The present invention relates to a metal detector using a plurality of magnetic sensor coils that detect metal foreign matter mixed in foods, pharmaceuticals, cosmetics, chemicals, and the like.

This type of metal detector and its detection method is such that a current is passed through a coil or the like to generate a magnetic field, and a magnetic sensor such as a coil is disposed at a position to receive the magnetic flux of this magnetic field, and the object to be moved moves in this magnetic field. Is detected by a signal from a magnetic sensor, and the presence or absence of metal in the object to be inspected is determined based on this detection signal. For example, many common foods often contain moisture and salt, and their conductivity shows the same properties (conductivity signal, nonmagnetic signal) as the conductor metal, which hinders detection sensitivity. Others that generate non-magnetic signals include aluminum foil and aluminum deposited as product packaging. In addition, there is a mixture of magnetic powder (micro diameter iron powder, SUS powder, etc.) in a dry product such as a chemical product, and a magnetic signal is generated depending on the total amount. Further, there is a signal (mechanical vibration signal) generated when mechanical vibration is applied. Many techniques for reducing this noise have been proposed. Some of these are:
The technique disclosed in Japanese Patent Application Laid-Open No. 60-78378 is based on the fact that when the object to be inspected contains moisture or salt, it is detected from the oscillator supplied from the detector according to the material of the object to be inspected. This is a metal detector that automatically switches the phase of the sync signal to reduce the effects of noise. In addition, the technique disclosed in Japanese Patent Laid-Open No. 3-279888 is determined to be a detection output signal generated by vibration in order to prevent erroneous detection of metal pieces based on vibration of a belt conveyor that conveys an object to be inspected. In this case, the metal inspection apparatus can stop the output of the detection signal. Furthermore, the technique disclosed in Japanese Patent Laid-Open No. 5-87942 is a magnetic field output from the transmission coil in accordance with the product type so that the metal piece can be detected stably regardless of the product type of the inspection object. It is a metal inspection device that can change the strength of the metal.

JP-A-5-87492

In the conventional metal detector described above, in order to reduce the influence of mechanical vibration due to the weight of the inspection object or noise generated from peripheral equipment, it is necessary to use individual processing circuits, and the circuit configuration is complicated. There is a problem. Further, when the noise becomes a certain level, it is difficult to increase the detection sensitivity even if the above processing circuit is used. The present invention has been proposed in order to solve the above-mentioned problems, and its purpose is not only to reduce the influence of the above-mentioned noise and the like with a simple configuration, but also to a metal regardless of the size and weight. It is an object of the present invention to provide a metal detector capable of increasing the detection sensitivity of foreign matter.

The basic concept of the present invention will be described.
The magnitude of the noise signal generated by mechanical vibration or peripheral equipment is proportional to the magnetic passage area and volume of the inspection object moving in the inspection magnetic field. Therefore, the smaller the passage area of the inspection magnetic field, the smaller the noise signal. The size becomes smaller. However, since the magnitude of the detection signal for the metal to be detected is determined by the size of the target metal, there is a property that it does not relate to the size of the passage area described above. The present invention makes use of this property to divide the passage area of the magnetic field for inspecting the inspection object into a plurality of areas so that one inspection magnetic field is reduced to reduce the influence of noise, so that the movement line of the inspection object is reduced. The inspection object is divided and detected in a predetermined direction, and the detection signals of the divided inspection objects are combined to determine the presence or absence of metal contamination.
Based on the basic idea described above, in order to achieve the above object, the metal detection method according to claim 1 moves an inspection object into a magnetic field generated by a magnetic field generating means and receives the magnetic field by a magnetic coil sensor. In the metal detection method for detecting the presence or absence of metal mixed in the inspection object by detecting the magnetic flux change of the magnetic field, the magnetic flux entering the magnetic coil sensor is changed to a predetermined direction of the movement line of the inspection object. Are divided into a plurality of magnetic sensor coils 1a, 1b, 2a, 2b, which are provided at least above and below the magnetic sensor coils 1a, 1b, 2a, 2b and the detected object. Then, the magnetic flux change is individually detected by receiving the magnetic flux, and the presence or absence of metal mixed in the corresponding portion of the detected object is detected by dividing each. Further, the object to be inspected is moved into the magnetic field generated by the magnetic field generating means according to claim 2 capable of performing the above-described metal detecting method, the magnetic coil sensor receives the magnetic field, and the magnetic flux change of the magnetic field is detected by the detecting means. It is used for a metal detector configured to detect and detect the presence or absence of metal mixed in an object to be inspected. In the magnetic detection unit, a magnetic detection unit that divides the magnetic flux entering the magnetic coil sensor into a plurality of pieces in a predetermined direction of the movement line of the inspection object is provided at least between the inspection object and receives the divided magnetic flux. The magnetic flux change is detected individually, and the presence or absence of metal mixed in a corresponding portion of the inspection object detected by dividing each is detected. According to another magnetic field generation method of claim 3, there are two transmission / reception type magnetic sensor coils that supply a DC voltage and generate a magnetic field from the magnetic sensor coils 1a, 1b, 2a, 2b and the magnet 3, which are arranged vertically. A magnetic detection unit comprising a pair of sensor coils, which is a facing type, and that arranges a transmission / reception type magnetic sensor coil to a location where a detected object can pass through the magnetic flux generated from the sensor coil and the magnet 3 in a predetermined direction. A plurality of magnetic fluxes that are provided between the inspection objects and pass through the first detection part 1 in the predetermined direction of the moving line of the inspection object. In the magnetic sensor coil, and a second magnetic detection unit 2 having a second magnetic detection unit 2 disposed at a position corresponding to a blank portion of the first magnetic detection unit 1. Each divided Presence of the metal is detected to be mixed into corresponding parts.

As described above, when the metal detector of claims 1 to 5 is used, the magnetic sensor coil divides the object to be inspected and contains moisture and salt, or the same property as the conductive metal (conductivity signal, Non-magnetic signal), other products that generate non-magnetic signals, aluminum foil as a product packaging, aluminum-deposited products, and dry powder such as chemical products (fine iron powder) , SUS powder, etc.), a magnetic signal is generated depending on the total amount, and the influence of noise and the like that interferes with detection sensitivity such as noise (mechanical vibration signal) generated when mechanical vibration is applied is divided. You can make it smaller. As a result, the detection sensitivity of metal detection can be increased. Moreover, when dividing | segmenting by Claim 4, 5, there exists an effect that a detection area can be made small, the influence of noise etc. can be made small, and also an apparatus can be simplified.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking as an example a case where the present invention is applied to a device. A form corresponding to claim 3 which is the concept of claim 2 An embodiment of FIG. 1 will be described. FIG. 1 is a schematic configuration perspective view of a magnetic coil sensor according to the first embodiment. Two magnetic sensor coils 1a, b of a first magnetic detection unit 1 and 2a, b of a second magnetic detection unit 2 Consists of. The magnetic sensor coil is a conventional electromagnetic induction sensor coil type, which is a magnetic field generating means for generating a magnetic field by supplying a voltage to the magnetic sensor coil, and is a facing type in which the magnetic sensor coils 1a and 1b are disposed facing each other. .
The inspection object X is composed of a transmission / reception type magnetic sensor coil, a pair of magnetic sensor coils 1a and 1b arranged vertically, and a pair of sensor coils. When an object to be detected passes in the predetermined direction of the moving line in the figure, the magnetic sensor coil that generates the magnetic field and the magnetic flux generated from the magnet 3 receive the magnetic flux divided in the predetermined direction and change the magnetic flux individually. , And the presence or absence of metal mixed in a substantial part of the inspected object detected by being divided is detected. The height H of the detection unit indicates the height of the entrance of the detection unit. Further, the lateral width of the entrance is indicated by the width direction W of the moving line of the inspection object X shown in FIG. If the inspection object X has a height of 10 mm, for example, the entrance of the detection unit has a height of 10 mm.
The detection unit is provided between the magnetic sensor coil 1a and 2b arranged vertically and between the magnetic sensor coil and the inspection object X, and as shown in FIG. In order to maintain the balance of the magnetic sensor coils 1a, 1b, 2a, and 2b in the magnetic passing portion in an arrangement composed of combinations, it is necessary to make the areas of both magnetic sensor coils equal, and the shape of the magnetic sensor coils is the same rectangular shape. It is. (Hereafter, the same applies to other embodiments as long as the magnetic sensor coils are added.) For this reason, the first detectors and the second detectors are provided alternately. By displacing the second detection unit, it is possible to minimize the mutual influence due to the magnetic flux that passes through each of the second detection units. Further, the vertical length of the magnetic sensor coil is a length that is slightly longer than ½ of the width direction W of the inspection magnetic field region so that the inspection does not leak. In addition, in each drawing such as FIG. 1, in order to make it easy to understand, it is displayed with a divided length in the width direction W (the same applies hereinafter). By arranging the magnetic sensor coil and the magnet 3, the magnetic flux is combined and the magnetic flux density is increased. The magnetic sensor coil should be as small as possible and is appropriately determined depending on the number of turns of the sensor coil, the winding diameter, the wire diameter, etc. . This is because the inspection object X continuously moves in the magnetism in a predetermined direction of the moving line, so that it is only necessary to secure a minimum area through which the magnetic flux necessary for detection can pass.
FIG. 3 is a diagram illustrating a mechanism configuration of a main part of the metal detector according to the embodiment. Stainless steel 15 having a thickness of about 3 mm to 5 mm is used to contact the magnetic sensor coil so that mechanical vibration (mechanical vibration signal) of each divided portion is not generated. About the function and movement form regarding another metal detector, it is the same as the said item, and abbreviate | omits description.
As shown in FIG. 2, the magnetic sensor coil and the magnet 3 are arranged so that the magnetic fluxes are combined and the detection unit 14 in which the magnetic flux density increases is divided into four magnetic sensor coils. Here, in the magnetic sensor coil at the moment when the inspection object X enters the inspection magnetic field, the magnitude of the noise of the magnetic flux entering the half length portion in the width direction W is a quarter of the conventional size. . At the same time, if there is a mixed metal, a metal detection signal having the same size as the conventional one is generated if the metal is contained even in half the area. Therefore, the influence of noise on the metal detection signal is significantly reduced.
The material used for the magnetic sensor coil may be a ferromagnetic material that exhibits a magnetic shielding function, and examples thereof include iron, nickel, cobalt, silicon steel, and permalloy. In addition, there are ferrimagnetic materials such as aluminum, copper and ferrite, and those mixed with noble earth elements (samarium cobalt etc.). Further, the shape and number are limited to the above rectangle, but the number of installations is not limited, and a number other than four can be adopted.
The above-described magnetic sensor coil is a transmission / reception magnetic sensor coil that generates a magnetic field when supplied with a DC voltage, and the magnetic sensor coil includes a pair of transmission / reception magnetic sensor coils. Other components are those that have been widely used. Further, the detection processing unit 7 in FIG. 5 mainly includes an amplifier 8, detection comparators 9 and 11, and a discriminator 13. The processing circuit for adjusting the phase disclosed in the above-described prior art can also be provided although not shown.
Next, the operation of the above-described embodiment will be described. This operation is a concept showing the characteristic process of the metal detection method corresponding to claim 1. That is, in the detection method, the inspection object X is moved into the magnetic field generated by the magnetic sensor coil as the magnetic field generation means, the magnetic field is received by the same magnetic sensor coil for transmission and reception, and the magnetic flux change of the magnetic field is detected by the detection means. The presence or absence of metal mixed in the test object X is detected by a detection processing unit 7. As the generated magnetic field, a unidirectional magnetic field generated by a DC power source or a pulsating magnetic field in which the magnetic flux density is increased by the magnet 3, the loop filter 10, and the low pass filter 12 is used.
In the operation of the embodiment, first, the magnetic flux entering the magnetic sensor coils 1a, 1b, 2a, 2b of the first magnetic detection unit 1 and the second magnetic detection unit 2 is divided into a plurality in the predetermined direction of the moving line of the inspection object X. . The magnetic sensor coil receives the divided magnetic flux and individually detects the change in the magnetic flux. Here, the other magnetic sensor coil in which the inspection object X is not in the inspection magnetic field does not receive the magnetic flux. If there is a mixed metal, if the metal is contained even in half the area, a metal detection signal having the same size as the conventional one is generated, and the remaining magnetic sensor coil does not generate a metal detection signal. Therefore, the influence of noise on the metal detection signal is remarkably reduced, and there is no problem even if the detection sensitivity is increased. Then, the detection signal from the amplifier 8 in FIG. 5 is detected by the detection comparators 9 and 11, and the presence or absence of metal contamination is determined by the determination unit 13. A substantial part of the inspection object X detected by each divided magnetic sensor coil is determined for the presence or absence of mixed metal. In conventional metal inspection equipment, in the case of aluminum foil or aluminum vapor-deposited packaging containers, the signal to the sensor coil is destroyed due to the influence of this packaging container. Will be output. However, the influence of this packaging container can be cut with the magnetic sensor coil of claims 1-5.
Next, an embodiment corresponding to claim 4 which is the concept of claims 2 and 3 will be described. As shown in FIG. 4, the embodiment has a configuration in which the number of sets of magnetic sensor coils is two and includes first and second magnetic detectors (1, 2). The arrangement in the front-rear direction is not limited to two rows, but may be one or three rows, and can be appropriately increased or decreased when the number of sets increases. In the first and second magnetic detectors, the magnetic sensor coils are arranged one above the other, and twelve rectangular magnets 3 are provided in total. For this reason, the inspection area of the inspection object X is also divided into a plurality of parts in a predetermined direction, and each divided portion is individually detected as the inspection object X moves. Therefore, in the operation of the embodiment, since the inspection object X is detected in the four-divided state, the influence of noise is reduced to a quarter in each divided portion. Since other configurations and operations are the same as those in the above embodiment, detailed description thereof is omitted. Also, there are three detection signal amplifying units 4 in FIG. 4 according to the number of sets of magnetic sensor coils. If one of the three is discriminated as a metal, the overall control has a control function such as discriminating the presence of metal as a whole. Parts are provided. The metal detection / determination unit in FIG. 4 has a conventional general circuit configuration and can be easily increased. In addition, the control function of FIG. 5 can also be included in the control part (illustration omitted) of a metal detector main body, without providing a comprehensive control part.
When the above-described embodiment is generalized, by arranging the magnets 3 for each magnetic sensor coil, the magnetic fluxes are combined to increase the magnetic flux density, so that 4n sets of magnetic sensor coils and magnets are used. The number of magnetic detection units consisting of 3 is 4n. For this reason, metals are detected individually according to the movement of the inspection object X. Therefore, in the operation of the embodiment, the inspection object X is inspected in a four-divided state, and the influence of noise can be reduced to 1 / 4n, and the inspection sensitivity can be increased accordingly. In addition, since the adjacent magnetic passage portions are shifted back and forth (FIG. 2) so as not to be affected by the passing magnetic fluxes, the influence of noise is further reduced.
Although it is other embodiment corresponding to Claim 2, illustration is abbreviate | omitted, the 2nd magnetic detection part of the embodiment mentioned above is omitted, and only the 1st magnetic detection part 1 installed between test bodies X is shown. The configuration is as follows. With this configuration, the same operation as the basic operation can be performed and the number of parts can be reduced. The magnetic field generating means of claim 2 can include not only the magnetic field generated by the voltage supply of the above embodiment but also the unidirectional magnetic field generated by the permanent magnet.
An embodiment corresponding to claim 5 will be described. As shown in FIG. 1, the embodiment is a coaxial type magnetic detection unit in which the magnetic sensor coils 1 a and 1 b are coaxially arranged with a magnetic sensor coil sandwiched therebetween. This magnetic sensor coil coincides with the moving line of the test object X. In this case, the position where the magnetic sensor coil and the magnet 3 are arranged is determined by the width direction W centering on the moving line. The same width direction W as the opposed type is used. Inspection object X
The two magnetic detectors that are divided into two in the predetermined direction and the width direction W of the moving line are magnetic sensor coils 1a, 1b and magnetic sensor coils 2a, 2b constituting the second detecting unit in the predetermined direction of the moving line, respectively. It is provided as a passage for the inspection object at a symmetrical position on the upper and lower surfaces so as to be shifted forward and backward and not to overlap with the movement line as the center. As described above, the magnetic field effects are suppressed to the minimum because they are provided at symmetrical positions on the upper and lower surfaces. For this reason, in the state where the inspection object X is divided into two and the influence of noise is halved, the presence or absence of metal mixed in the divided corresponding parts is detected. Other configurations and operations of the detection processing unit and the like are the same as those in the above embodiment, and a detailed description thereof is omitted.
The length of the time sensor coil in a predetermined direction of the inspection object is a length including the magnetic sensor coils 1a, 1b, 2a, and 2b in the width direction W with the moving line as the center. This width is selected without limitation.
Moreover, as shown in FIG. 2, the structure which provided the magnetic sensor coil two front and back is employable.
When the above-described embodiment is generalized, each set of magnetic sensor coils has one magnet part. Therefore, if there are n sets of magnetic sensor coils, the number of magnets 3 as magnetic detection parts is 2n. Become. For this reason, the inspection object X is divided into several parts in a predetermined direction and inspected, and the influence of noise can be reduced to a maximum of 1 / 2n, and the inspection sensitivity can be increased accordingly.
The embodiment corresponding to claim 2 is a configuration in which the magnetic sensor coil is a facing type or a coaxial type, and is used for a planar type also serving as a magnetic sensor coil. As shown in FIG. 3, the embodiment has a configuration in which two detection locations that are magnetic detection units are provided on a plane that also serves as a transmission / reception magnetic sensor coil. In this flat type, a DC voltage is supplied to the magnetic sensor coil to generate a magnetic field. When the inspection object X passes through a pair of magnets, the magnetic flux density changes, and the detection signal from the amplifier in FIG. Detection is performed, and the discriminator 13 discriminates the presence or absence of metal contamination. A substantial part of the inspection object X detected by each divided magnetic sensor coil is determined for the presence or absence of mixed metal. In conventional metal inspection equipment, in the case of aluminum foil or aluminum vapor-deposited packaging containers, the signal to the sensor coil is destroyed due to the influence of this packaging container. Will be output. However, the influence of this packaging container can be cut with the magnetic sensor coil of claims 1-5.
In the case of this inspection object X, if iron metal is mixed in a predetermined direction, the magnetic flux density of the magnetic sensor coils 1a, 1b, 2a, 2b decreases, so that the output waveform passes through the amplifying unit 8 and the detection comparator 9 11, and the output passes through the first magnetic detection unit 1 and the second magnetic detection unit 2 as shown in FIG. The presence or absence of metal contamination is detected from the magnetic detection part metal detection waveform 17 when a metal output is generated in the first magnetic detection part metal detection area 16a and the second magnetic detection part metal detection area 17a. Moreover, by outputting to the noise determination area | region 18, it can be judged that the unnecessary signal is output and it can cut as noise with a program.
Although the magnetic sensor coil is an induction sensor coil type as described above, a semiconductor sensor made of a Hall element can be used instead of the magnetic sensor coil.

It is a figure which shows schematic structure of the magnetic sensor coil of embodiment concerning this invention. It is a figure which shows the plane on the lower surface side same as the above. It is a mechanism part block diagram which shows a metal detector same as the above. It is a block diagram which shows the component concerning one Example. It is a block diagram which shows the component in connection with one Example. It is a figure which shows the detection output signal concerning one Example.

DESCRIPTION OF SYMBOLS 1 1st magnetic detection part 2 2nd magnetic detection part 1a, 1b, 2a, 2b Magnetic sensor coil 3 Magnet 4 Detection signal amplification part 5 Passing time measurement part 6 Metal detection determination part 7 Detection processing part 8 Amplifier 9, 11 Comparison comparison Device 10 loop filter 12 low pass filter 13 discriminator 14 detector 15 stainless steel 16 first magnetic detector metal detection waveform 16a first magnetic detector metal detection region 17 second magnetic detector metal detection waveform 17a second magnetic Detection unit metal detection area 18 Noise judgment area

Claims (5)

A plurality of magnetic sensor coils 1a, 1b, 2a, 2b are arranged up and down, a magnetic field is generated, and a detected object in the magnetic field is detected by a magnetic coil sensor by a magnetic flux change due to the movement of the detected object. In the metal detection method for detecting the presence or absence of metal mixed in the magnetic sensor, the magnetic sensor coil in which a plurality of magnetic fluxes entering the magnetic sensor coil are arranged in a predetermined direction of the detection object is divided by providing the magnetic detection part of the detection object. The magnetic sensor coils 1a, 1b, 2a, and 2b arranged in this manner detect the change in magnetic flux by at least one magnetic sensor coil, and detect the presence or absence of metal mixed in the detected objects separately divided. This is a metal detector. A plurality of magnetic sensor coils 1a, 1b, 2a, 2b are arranged vertically, a magnetic field is generated, a detected object in the magnetic field is moved, the magnetic sensor coil receives the magnetic field, and a magnetic flux change of the magnetic field is detected by a metal detection method. The magnetic flux entering the magnetic sensor coils 1a, 1b, 2a and 2b used in the metal detector configured to detect the presence or absence of metal mixed in the detected object is detected in a predetermined direction of the moving line of the detected object A plurality of magnetic sensor coil portions are provided at least above and below the magnetic sensor coils 1a, 1b, 2a, 2b and the detected object, and receive magnetic fluxes at the plurality of magnetic sensor coils individually. A metal detector characterized by detecting the magnetic flux change and detecting the presence or absence of metal mixed in a substantial part of the detected objects detected by dividing each of them. Transmission / reception type magnetic sensor coils 1a, 1b, 2a, 2b that supply a DC voltage and generate magnetic fields from the magnetic sensor coils 1a, 1b, 2a, 2b and the magnet 3 by the above magnetic field generation method, Magnetic sensing, in which a pair of sensor coils are opposed to each other, and a transmission / reception type magnetic sensor coil is arranged at a location where a detected object can pass through the magnetic flux generated from the sensor coil and the magnet 3 in a predetermined direction. The first magnetic detection unit 1 and the second magnetic detection unit 2 are provided between the inspection objects in a predetermined direction of the moving line of the inspection object, and pass through the first magnetic detection unit 1 Second magnetic detectors 2, 2 a, and 2, which have magnetic sensor coils 1, 1 a, 1 b arranged at positions corresponding to the blank portions of the first magnetic detector so that a plurality of magnetic fluxes can be put into the magnetic sensor coil. Is composed is b, the metal detectors described in claim 1 or claim 2 existence of metal to be mixed with each divided substantial portion of the inspection object is to be detected, characterized. 4. The metal detector according to claim 1, wherein the magnetic sensor coils 1a, 1b, 2a, 2b for detecting metal are of a transmission / reception integrated type. The magnetic sensor coil is a transmission / reception magnetic sensor coil that is supplied with a DC voltage to generate a magnetic field, and the magnetic sensor coil is composed of a pair of transmission / reception magnetic sensor coils sandwiching the magnetic sensor coil on the lower surface. The magnetic sensor coils are arranged on the upper and lower surfaces of the opposed type, and at least one pair of the transmission / reception magnetic sensor coils is disposed and arranged so as not to overlap with each other with the transmission / reception magnetic coil axes as the center. In the predetermined direction of the movement line, the presence or absence of metal mixed in the corresponding divided parts is detected. The claim 1 or claim 2 or claim 3 or claim 4 Metal detector.

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