JP4156577B2 - Metal detector - Google Patents

Description

  The present invention relates to a metal detection apparatus that performs an inspection (hereinafter referred to as a metal foreign matter contamination inspection) for detecting a metal foreign matter mixed in an article by conveying the article in a DC magnetic field.

  A metal detection device is used to perform a metal foreign matter mixing inspection for detecting a metal foreign matter mixed in an article such as a food product, a pharmaceutical product, or clothing. Conventionally, as a metal detection device, an object to be inspected for contamination of metal (hereinafter referred to as an object to be inspected) is conveyed to a DC magnetic field by a conveyor, and the presence or absence of the metal contamination is detected. What sorts an object to be inspected is known. There are two types of metal detectors using a DC magnetic field, which will be described below.

  First, as shown in FIG. 6, the first type metal detection apparatus conveys the object to be inspected 1 through the DC magnetic field generated by the exciting coil 602 of the magnetizing apparatus 601, and ignores the influence of the applied magnetic field. The inspection object 1 is transported to the extent possible, the detection device 603 having the detection coils 604a and 604b measures the magnetization of the inspection object 1, and the determination device 605 determines the presence or absence of a metallic foreign object. This is because the metal foreign object is magnetized by transporting the test object mixed with the magnetic metal foreign object into the DC magnetic field, and the presence or absence of the metal foreign object is determined by measuring the magnetization amount of the magnetized metal foreign object. (For example, refer to Patent Document 1).

This type of metal detection apparatus is configured such that the position where the DC magnetic field is applied is separated from the position where the amount of magnetization is measured. Further, in this type of metal detection apparatus, the object to be inspected passes through a gap formed by both poles of a magnet that generates a DC magnetic field to be applied, and usually includes a pair of coils for measuring the amount of magnetization formed of a pair of coils. As shown in FIG. 7, the second type metal detection device configured to pass through the gap conveys the inspected object 1 to the magnetization device 710 and magnetizes it, and in the magnetic head 720, the transmission coil 721. The receiving coils 722 and 723 detect a magnetic field change when passing through a DC magnetic field generated by the control circuit 730, and the control circuit 730 determines the presence or absence of a metallic foreign object. This utilizes the fact that when a metal foreign object having magnetism is mixed in an object to be inspected, the induced voltage varies depending on the amount of magnetism mixed (see, for example, Patent Document 2).

This type of metal detection apparatus is configured such that the position where the DC magnetic field is applied and the position where the amount of magnetization is measured are close to each other. In addition, this type of metal detection device has a configuration in which a magnet such as a bar magnet that generates a DC magnetic field to be applied and a differentially connected coil that detects the amount of change in magnetic field distribution are opposed to each other. Have.
JP 2003-66156 A JP 59-160787 A

  However, in such a conventional first type metal detection apparatus, the magnetic field near the center of the gap formed by both poles of the DC magnetic field application magnet is weaker than the magnetic field near both poles, and the amount of magnetization is measured. Because the magnetic detection sensitivity in the vicinity of the center of the gap formed by both coils is lower than the detection sensitivity in the vicinity of both coils, the detection sensitivity of metallic foreign matter passing through the vicinity of the center of each gap is reduced. There was a problem.

  Further, in the conventional second type metal detection apparatus, there is a problem that the detection sensitivity with respect to the metal foreign matter is lowered when the package of the object to be inspected is an aluminum foil.

  The present invention has been made to solve such a problem, and provides a metal detection device capable of improving the detection sensitivity near the center of the gap and the detection sensitivity of a magnetic metal present in an aluminum foil package. It is.

A detection unit (110) that detects metal mixed in an object to be inspected conveyed on the conveyance path, and a control unit (120) that determines presence / absence of metal based on a detection signal output from the detection unit. In the metal detection device (100) provided, the detection unit is disposed so as to sandwich the conveyance path, and a pair of DC magnetic field application magnets for applying a DC magnetic field to the object to be inspected; When the object to be inspected passes through the gap between the magnetic poles of the pair of DC magnetic field application magnets, arranged in parallel with the conveying direction so as to sandwich any one of the DC magnetic field application magnets And a pair of differentially connected magnetic field distribution change detection coils for detecting a change in the magnetic field distribution occurring between the magnetic field distribution and the conveyance path, and a magnetic field by the pair of DC magnetic field applying magnets does not reach. The pair of DC magnetic fields to the extent Poles of both the pair of DC magnetic field applying magnet so that the detection sensitivity for magnetic magnetized in the direction connecting the both poles of the pair of DC magnetic field applying magnet at a position away from the pressurized magnet becomes high And a pair of magnetic detection coils that detect residual magnetism in the object to be inspected.

With this configuration, a pair of magnetic field distribution change detection coils for detecting a change in the magnetic field distribution that occurs when the object to be inspected passes through the gap between the magnetic poles of the pair of DC magnetic field applying magnets, Since a pair of magnetic detection coils that detect residual magnetism are provided, detection sensitivity can be increased by using the detection signal of the magnetic field distribution change detection coil for those in which the influence of contaminants tends to appear in the change of the magnetic field distribution. For metal foreign matter having magnetism, the detection sensitivity of the magnetic detection coil can be used to increase the detection sensitivity, so that the detection sensitivity near the center of the gap and the magnetic metal present in the aluminum foil package It is possible to realize a metal detection device capable of improving the detection sensitivity.
In addition, the pair of magnetic field distribution change detection coils are arranged so as to sandwich either one of the pair of DC magnetic field application magnets, so that a magnetic field change in the vicinity of the DC magnetic field application magnet can be detected. Further, it is possible to realize a metal detection device that can further improve detection sensitivity. Further, the opening is maximized in the direction connecting both magnetic poles of the pair of DC magnetic field applying magnets so that the detection sensitivity to the magnetized magnetism in the direction connecting both magnetic poles of the pair of DC magnetic field applying magnets is increased. Therefore, it is possible to realize a metal detector capable of further improving detection sensitivity. Further , since the pair of magnetic field distribution change detection coils are differentially connected, it is possible to realize a metal detection device that can manipulate the influence of noise and can further improve detection sensitivity.

The invention according to claim 2, Oite to claim 1, wherein the pair DC magnetic field applying magnet and the pair of magnetic detection coil may have a configuration that is disposed above and below each of the conveying path is doing.

With this configuration, in addition to the effect of claim 1, the pair of DC magnetic field applying magnets and the pair of magnetic detection coils are arranged above and below the conveyance path, respectively, so that the front side of the metal detection device can be opened, Therefore, a metal detection device capable of improving workability can be realized.

  The present invention provides a pair of magnetic field distribution change detection coils for detecting a change in magnetic field distribution when passing through a gap between both magnetic poles of a pair of DC magnetic field applying magnets and before and after passing, and a magnetism in an object to be inspected. Since a pair of magnetic detection coils for detecting the magnetic field distribution is provided, the detection sensitivity of the magnetic field distribution change detection coil can be increased for those that are likely to be affected by contaminants in the magnetic field distribution change. The detection sensitivity can be increased by using the detection signal of the magnetic detection coil, and the detection sensitivity near the center of the gap and the detection of the magnetic metal present in the aluminum foil package. It is possible to provide a metal detection device having an effect that sensitivity can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is an explanatory diagram conceptually showing a block configuration of a metal detection apparatus according to an embodiment of the present invention. The metal detection device 100 according to the embodiment of the present invention includes a transport conveyor 2 (see FIG. 2), a detection unit 110 that detects metal foreign matter mixed in the inspection object 1 transported on the transport path, A control unit 120 that determines the presence / absence of a metal foreign object based on a detection signal output from the detection unit 110, and an operation display unit 130 that performs a predetermined operation input for operating the metal detection device 100 and displays information. With.

  Here, the above “inspected object” means “article subject to metal foreign matter contamination inspection”, and “inspection for detecting metallic foreign matter mixed in the article” is referred to as “metal foreign matter contamination inspection”. .

  The detection unit 110 is arranged so as to sandwich the conveyance path, and supplies power to the pair of DC magnetic field application magnets 21 for applying a DC magnetic field to the object 1 and the pair of DC magnetic field application magnets 21. Thus, the gap between the magnetic poles of the pair of DC magnetic field applying magnets 21 (hereinafter simply referred to as the gap between the magnetic poles) disposed near the power source 111 that generates the magnetic field and the pair of DC magnetic field applying magnets 21. A pair of magnetic field distribution change detection coils 22a and 22b for detecting a change in the magnetic field distribution that occurs when the object to be inspected passes, and a pair of magnetic detection coils 23a and 23b for detecting the residual magnetism in the object 1 to be inspected. And have. Hereinafter, a portion constituted by a pair of DC magnetic field application magnets 21, magnetic field distribution change detection coils 22a and 22b, and magnetic detection coils 23a and 23b is referred to as a magnetic field generation detection unit 112.

  The detection unit 110 further includes a differential amplification unit 113 that differentially amplifies signals output from the magnetic field distribution change detection coils 22a and 22b, and a low-frequency component of the signal that is differentially amplified by the differential amplification unit 113. 1 low-pass filter (shown as LPF in FIG. 1) 114 and first analog-to-digital converter (A in FIG. 1) that converts the signal output from the first low-pass filter 114 into a digital signal. 115, first amplification means 116a for amplifying the signal output from the magnetic detection coil 23a, second amplification means 116b for amplifying the signal output from the magnetic detection coil 23b, The second low-pass filter 117a and the third low-pass filter that pass the low-frequency components of the signals output from the first amplifying unit 116a and the second amplifying unit 116b, respectively. And motor 117b, each signal the second low-pass filter 117a and the third low-pass filter 117b outputs, respectively, and a second analog-to-digital conversion means 118 for converting into a digital signal.

  FIG. 2 is a schematic diagram for explaining the positional relationship between a pair of DC magnetic field application magnets 21, magnetic field distribution change detection coils 22a and 22b, and magnetic detection coils 23a and 23b. In FIG. 2, the pair of DC magnetic field applying magnets 21 shown in FIG. 1 is described as two magnets 21a and 21b, but this is symbolically showing the magnetic poles of the pair of DC magnetic field applying magnets 21. The pair of DC magnetic field applying magnets 21 is a magnet having a gap between magnetic poles at a position sandwiching the conveyance path, and the device under test 1 passes through the gap between the magnetic poles.

As shown in FIG. 2, a pair of DC magnetic field application magnets 21 (magnets 21a, 21b) are arranged so as to sandwich the conveyance path, and the magnetic field distribution change detection coils 22a, 22b are a pair of DC magnetic field application magnets 21. In the vicinity of (magnets 21a, 21b), a magnet 21b which is one of a pair of DC magnetic field applying magnets 21 (magnets 21a, 21b) is sandwiched. In contrast, the magnetic detection coil 23a, 23b is arranged so as to sandwich the conveying path, are arranged at a distance from a pair DC magnetic field applying magnet 21 (magnet 21a, 21b).

  Here, the magnetic field generated by the pair of DC magnetic field applying magnets 21 (magnets 21a, 21b) generally changes, but the magnetic detection coils 23a, 23b are a pair of DC magnetic field applying magnets 21 (magnets 21a, 21b). Are arranged at positions separated from the pair of DC magnetic field applying magnets 21 (magnets 21a and 21b) to such an extent that the influence of the change in the magnetic field generated by the

  The magnetic field distribution change detection coils 22a and 22b are arranged along the conveying direction of the device under test 1 at positions where the applied magnetic field is received in an equal amount. The magnetic field distribution change detection coils 22a and 22b are differentially connected to each other so that the signal becomes zero at a position where the applied magnetic field is received in an equal amount. The respective output signals from the magnetic field distribution change detection coils 22a and 22b are input to the differential amplification means 113 with different polarities, and the differential amplification means 113 makes a difference between the output signals from the magnetic field distribution change detection coils 22a and 22b. Is amplified and output.

  The magnetism detection coils 23a and 23b are provided so as to sandwich the conveyance path, and detect a voltage corresponding to the magnetism when the inspected object 1 mixed with a magnetic foreign metal enters. The magnetic detection coils 23a and 23b are preferably arranged so that the detection sensitivity to the magnetized magnetism in the direction connecting both magnetic poles of the pair of DC magnetic field applying magnets 21 (magnets 21a and 21b) is high. . That is, the magnetic detection coils 23a and 23b are arranged so that the opening is maximized in the direction connecting both magnetic poles of the pair of DC magnetic field applying magnets 21 (magnets 21a and 21b).

  The structure shown in FIG. 1 and FIG. 2 may be configured such that an approach sensor for detecting that the device under test 1 has entered the detection region near the magnetic field distribution change detection coils 22a and 22b or the magnetic detection coils 23a and 23b may be added. . The signal processing of the detection signal for a metal foreign material mixing test may be started after the ingress sensor detects that the device under test 1 has entered the detection area. As an approach sensor, for example, it has a light source that emits a light beam and a light receiver that receives the light beam emitted from the light source, and the light receiver cannot receive the light beam while the light source emits the light beam. It may be configured by a so-called projector / receiver or the like that detects the entry of the article and detects the entry of the article.

  In FIG. 2, the gap between the magnetic poles and the gap formed by the pair of magnetic detection coils 23a and 23b (hereinafter simply referred to as the inter-coil gap) are equally represented. It is not necessarily the same. Further, the present invention does not exclude a configuration in which the magnetic detection coils 23a and 23b are arranged at positions shifted in the conveyance path direction.

  Hereinafter, the operation of the detection unit 110 according to the embodiment of the present invention will be described. When the device under test 1 enters the detection region of the magnetic field distribution change detection coils 22a and 22b, the magnetic field distribution change detection coils 22a and 22b detect changes in the magnetic field distribution due to the inspection object 1 being conveyed through the detection region. Are output to the differential amplifying means 113 as analog electric signals (hereinafter referred to as analog detection signals).

  The analog detection signal input to the differential amplifying unit 113 is differentially amplified by the differential amplifying unit 113, so that a signal of a component mainly caused by a change in the magnetic field distribution (hereinafter referred to as a magnetic field distribution change component) is obtained. Is amplified and output to the first low-pass filter 114. The analog electric signal input to the first low-pass filter 114 has its noise removed by extracting a signal component in a low frequency band including the frequency band of the magnetic field distribution change component, and the first analog-to-digital conversion means 115 is output.

  The “low-frequency signal component including the frequency band of the magnetic field distribution change component” input to the first analog-digital conversion unit 115 is converted from an analog signal to a digital signal and output to the control unit 120. Hereinafter, the digital signal output from the first analog-digital conversion unit 115 to the control unit 120 is referred to as a magnetic field distribution change digital signal.

  Next, when the inspection object 1 enters the detection area of the magnetic detection coils 23a and 23b, the inspection object 1 is transported in the detection area when a foreign object having magnetism is mixed in the inspection object 1. Thus, a voltage corresponding to the magnetism of the mixed foreign matter is induced in the magnetic detection coils 23a and 23b. The signal induced in the magnetic detection coil 23a is output to the first amplifying unit 116a as a first magnetic detection signal. Similarly, the signal induced in the magnetic detection coil 23b is output to the second amplifying unit 116b as a second magnetic detection signal.

  The first magnetic detection signal input to the first amplification means 116a is amplified and output to the second low-pass filter 117a, and is induced in the magnetic detection coil 23a by the second low-pass filter 117a. The noise is removed by extracting the signal component in the low frequency band including the frequency band of the signal component, and is output to the second analog-digital conversion means 118.

  Similarly, the second magnetic detection signal input to the third low-pass filter 117b is amplified and output to the third low-pass filter 117b, and is detected by the third low-pass filter 117b. The noise is removed by extracting the signal component in the low frequency band including the frequency band of the signal component induced in the coil 23 b, and output to the second analog-to-digital conversion means 118.

  Each signal input from the second low-pass filter 117a and the third low-pass filter 117b to the first analog-to-digital converter 115 is converted from an analog signal to a digital signal by the second analog-to-digital converter 118, respectively. It is converted and output to the control unit 120. The digital signal output from the second analog-digital conversion means 118 may be output serially or in parallel. Hereinafter, the digital signal output from the second analog-digital converting unit 118 to the control unit 120 is referred to as a magnetic digital signal.

  FIG. 3 is a diagram showing a block configuration of the control unit 120 configuring the metal detection device 100 according to the embodiment of the present invention. The control unit 120 starts up the input interface 121 to which a predetermined signal is input, a CPU (Central Processing Unit) 122 that performs predetermined information processing and control for realizing the function of the metal detection device 100, and the CPU 122. OS (Operating System), ROM (Read Only Memory) 123 for storing other programs, control parameters, etc., and RAM (Random Access Memory) for storing OS, application execution codes, data, etc. used by the CPU 122 ) 124 and EEPROM (Electrically Erasable Programmable ROM) that stores application software and predetermined data in a nonvolatile and rewritable manner 125, and is configured to include an output interface 126 for outputting a predetermined signal.

  Here, the input interface 121 includes a signal for specifying an operation input via the operation display unit 130 (hereinafter referred to as an operation signal), the first analog-to-digital conversion unit 115 of the control unit 120, and the second analog. The digital signal output from the digital conversion means 118 and other signals are input. Other signals include, for example, a mode designation signal for designating the operation mode of the metal detection device 100, a signal received by communication when performing predetermined control, and an entry sensor in the case of a configuration provided with an entry sensor. The signal etc. which are output from may be included. The signal input to the input interface 121 is not limited to a digital signal, and includes an analog signal as necessary. In this case, the input interface 121 may include a configuration unit that converts an analog signal into a digital signal.

  Under the control of the CPU 122, the output interface 126 outputs a determination signal indicating the determination result of the presence or absence of foreign matter to an external device (not shown) such as a sorter, and a pair of power sources 111 constituting the detection unit 110. A power control signal for controlling the power supplied to the DC magnetic field applying magnet 21 and other signals are output. As other signals, for example, predetermined signals such as a predetermined control signal and a signal transmitted by communication when performing control are output. In addition, the signal output from the output interface 126 is not limited to a digital signal, and includes an analog signal as necessary. In this case, it is assumed that the output interface 126 includes a configuration unit that converts a digital signal into an analog signal.

  Based on the magnetic field distribution change digital signal input to the input interface 121 from the first analog-to-digital conversion unit 115 and the magnetic digital signal input to the input interface 121 from the second analog-to-digital conversion unit 118, the CPU 122 It is determined whether or not foreign matter is mixed in the inspection object 1.

  Here, it is assumed that the control unit 120 stores in advance in the EEPROM 125 a magnetic field distribution change digital signal obtained by measuring the inspected object 1 that does not include a foreign object. In the above description, the EEPROM is used as a means for storing information in a nonvolatile manner. However, the present invention is not necessarily limited to the EEPROM, and may have another nonvolatile storage function such as a hard disk. Further, it is possible to store a magnetic field distribution change digital signal obtained by measuring a plurality of times or to store a part of each signal.

  The determination of the presence or absence of foreign matter based on the magnetic field distribution change digital signal is specifically performed as follows. The CPU 122 calculates a difference between the magnetic field distribution change digital signal input via the input interface 121 and the magnetic field distribution change digital signal stored in the EEPROM 125 (hereinafter referred to as a magnetic field distribution change difference signal), and the difference is a predetermined value. It is determined whether or not a threshold value (hereinafter referred to as a distribution threshold value) is exceeded. If it is determined that it has exceeded, it is determined that foreign matter is mixed in the inspection object 1.

  The magnetic field distribution change difference signal is generally composed of a plurality of signals whose contents are information detected at a predetermined conveyance interval or a predetermined time interval (hereinafter, each signal is referred to as an element signal). As the distribution threshold, a first distribution threshold to be compared with an average of each element signal, a second distribution threshold to be compared with the highest peak when a peak is present in the magnetic field distribution change difference signal, and each element A third distribution threshold value that is different for each signal, and other distribution threshold values corresponding to the inspected object 1 and contaminants can be used. When the third distribution threshold is used, for example, when any element signal exceeds the third distribution threshold, a determination method for determining that a foreign object is mixed in the inspected object 1, a predetermined number There are a determination method for determining that a foreign object is mixed in the inspection object 1 when the above element signal exceeds the third distribution threshold, and other determination methods.

  Specifically, the determination of the presence or absence of foreign matter based on the magnetic digital signal is performed as follows. The CPU 122 determines whether or not the magnetic digital signal input via the input interface 121 exceeds a predetermined threshold value. If it is determined that the magnetic digital signal is equal to or lower than the threshold value, the foreign object is inspected in the determination based on the magnetic digital signal. If it is determined that it is not mixed in the body 1 and it is determined that it has exceeded, it is determined that a foreign object is mixed in the inspection object 1.

  Here, the magnetic digital signal also includes a plurality of element signals in the same manner as the magnetic field distribution change difference signal. The above determination is made by comparing the peak height of the highest peak among the element signals with a threshold value. However, the determination may be made by comparing a plurality of element signals with threshold values, by comparing with other threshold values, or by other methods. Further, it is assumed that the information such as each distribution threshold value and threshold value is stored in the EEPROM 125 in advance.

  When the CPU 122 determines that no foreign matter is mixed in both the determination based on the magnetic field distribution change digital signal and the determination based on the magnetic digital signal, it is determined that the foreign matter is not finally mixed. judge. If any of the determination based on the magnetic field distribution change digital signal and the determination based on the magnetic digital signal determines that a foreign object is mixed, a determination result indicating that the foreign object is mixed is displayed. A determination signal as content is output to the outside. However, the determination signal may be a predetermined signal indicating that no foreign matter is mixed even when it is determined that no foreign matter is mixed.

  If the CPU 122 determines that a foreign substance is mixed, the size of the foreign substance mixed using a signal that can most clearly determine the mixing of the foreign substance among the magnetic field distribution change digital signal and the magnetic digital signal. Information on the information may be output and displayed on the operation display unit 130. In this case, it is assumed that information indicating the correspondence between the size of the foreign matter and the signal height is stored in the EEPROM 125 in advance as a table, for example.

  In FIG. 1, the operation display unit 130 includes, for example, a touch panel on which predetermined keys are arranged, and is used for parameters such as dimensions of the object 1 to be inspected, an operation mode of the metal detection device 100, and other metal foreign object contamination inspection. It is possible to input necessary information, an operation start instruction, an instruction to display predetermined data, and the like.

  Further, the operation display unit 130 displays operation information, information indicating the operation status, information indicating the result of the metal foreign object contamination inspection, and other information regarding the metal foreign object contamination inspection on the display part such as the touch panel. It may be. Moreover, a predetermined sound may be output. Further, the operation display unit 130 may have a predetermined pointing device and may be input via the pointing device.

  In the above description, the magnetic field distribution change detection coils 22a and 22b have been described with respect to the magnetic field generation detection unit 112 having a configuration in which a part of the pair of DC magnetic field application magnets 21 is sandwiched. The configuration is not limited to the configuration using the magnetic field generation detection unit 112. Instead of the magnetic field generation detection unit 112, as shown in FIG. Even when the magnetic field generation detecting unit 412 having a configuration arranged in the vicinity of the applying magnet 21 is used, as shown in FIG. 5, a magnetic field distribution change detecting coil 22a in the gap between the magnetic poles of the pair of DC magnetic field applying magnets 21 is used. , 22b may be used as a magnetic field generation detection unit 512 having a configuration in which a part or all of 22b is arranged.

  As described above, the metal detection device according to the embodiment of the present invention detects a change in magnetic field distribution that occurs when the object to be inspected passes through the gap between the magnetic poles of a pair of DC magnetic field application magnets. Since a pair of magnetic field distribution change detection coils and a pair of magnetic detection coils for detecting residual magnetism in the object to be inspected are provided, the magnetic field distribution change is likely to occur when the influence of contaminants appears on the change in the magnetic field distribution. The detection sensitivity can be increased by using the detection signal of the detection coil, and the detection sensitivity can be increased by using the detection signal of the magnetic detection coil for a metallic foreign object having magnetism. The detection sensitivity and the detection sensitivity of the magnetic metal present in the aluminum foil package can be improved.

  In addition, since the pair of magnetic field distribution change detection coils are differentially connected, the influence of noise can be manipulated and the detection sensitivity can be further improved.

  In addition, the pair of magnetic detection coils are arranged so that the detection sensitivity to the magnetized magnetism in the direction connecting both magnetic poles of the pair of magnets for applying a DC magnetic field is increased. Can be improved.

  In addition, since the pair of DC magnetic field applying magnets and the pair of magnetic detection coils are respectively disposed above and below the transport path, the front side of the metal detection device can be opened, thereby improving workability.

  In addition, the pair of magnetic field distribution change detection coils are arranged so as to sandwich either one of the pair of DC magnetic field application magnets, so that a magnetic field change in the vicinity of the DC magnetic field application magnet can be detected. Further, the detection sensitivity can be improved.

  Metal detection device according to the present invention is useful for metal detection devices and the like that have the effect of improving the detection sensitivity near the center of the gap and the detection sensitivity of magnetic foreign matter present in a magnetic package. It can also be applied to.

Explanatory drawing which shows notionally the block structure of the metal detection apparatus which concerns on embodiment of this invention Schematic diagram for explaining the positional relationship of a pair of DC magnetic field application magnets 21, magnetic field distribution change detection coils 22a and 22b, and magnetic detection coils 23a and 23b. The figure which shows the block structure of the control part 120 which comprises the metal detection apparatus 100 which concerns on embodiment of this invention. FIG. 2 is a schematic diagram for explaining a configuration having an arrangement different from the arrangement of the pair of DC magnetic field application magnets 21, magnetic field distribution change detection coils 22a and 22b, and magnetic detection coils 23a and 23b. FIG. 2 and FIG. 4 are schematic diagrams for explaining a configuration having an arrangement different from the arrangement of the pair of DC magnetic field applying magnets 21, magnetic field distribution change detection coils 22a and 22b, and magnetic detection coils 23a and 23b. Explanatory drawing which shows notionally the block structure of the conventional metal detection apparatus (metal detection apparatus of a 1st system). Explanatory drawing which shows notionally the block structure of the conventional metal detection apparatus (metal detection apparatus of a 2nd system).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test object 2 Conveyor 21,21a, 21b Magnet for direct current magnetic field application 22a, 22b Magnetic field distribution change detection coil 23a, 23b Magnetic detection coil 100, 600, 700 Metal detection apparatus 110 Detection part 111 Power supply 112, 412, 512 Magnetic field Generation detection unit 113 Differential amplification unit 114, 117a, 117b Low-pass filter 115, 118 Analog-digital conversion unit 116a, 116b Amplification unit 120 Control unit 121 Input interface 122 CPU
123 ROM
124 RAM
125 EEPROM
126 output interface 130 operation display unit 601 magnetizing device 602 exciting coil 603 detecting device 604a, 604b detecting coil 605 discriminating device 710 magnetizing device 720 magnetic head 721 transmitting coil 722 receiving coil 723 receiving coil 730 control circuit

Claims (2)

A detection unit (110) for detecting metal mixed in an object to be inspected conveyed on the conveyance path;
In the metal detection device (100) comprising a control unit (120) for determining the presence or absence of metal based on the detection signal output from the detection unit,
The detection unit is arranged so as to sandwich the conveyance path, and a pair of DC magnetic field application magnets for applying a DC magnetic field to the inspection object;
The one of the pair of DC magnetic field application magnets is arranged in parallel with the conveyance direction so as to sandwich the magnet, and the object to be inspected has a gap between both magnetic poles of the pair of DC magnetic field application magnets. A pair of differentially connected magnetic field distribution change detection coils that detect changes in the magnetic field distribution that occur when passing through;
The pair of DC magnetic field applying magnets are arranged so as to sandwich the conveyance path and are separated from the pair of DC magnetic field applying magnets so that a magnetic field by the pair of DC magnetic field applying magnets does not reach . The arrangement is such that the opening is maximized in the direction connecting both the magnetic poles of the pair of DC magnetic field applying magnets so that the detection sensitivity to the magnetized magnet in the direction connecting both the magnetic poles of the magnet is increased. A metal detection apparatus comprising a pair of magnetic detection coils for detecting residual magnetism in an inspection object. The metal detection apparatus according to claim 1, wherein the pair of DC magnetic field applying magnets and the pair of magnetic detection coils are respectively disposed above and below the transport path.

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