JP2006329963A - Foreign matter detection method and foreign matter detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foreign matter detector capable of detecting metallic foreign matter contained in an inspection object, independently of the direction thereof. <P>SOLUTION: A sensor unit 11 comprises a plurality of serially connected sensor cells 17. Minute magnetic field is generated from the sensor cells by applying a voltage or supplying a current to the sensor unit 11, a detection magnetic field from the metallic foreign matter in response to the minute magnetic field is detected as a detected voltage or detected current of the sensor unit 11, and a detection signal is outputted. This detection signal is analyzed to detect the metallic foreign matter. The minute magnetic field uses the nonlinear part of magnetic field characteristic of the core constituting the sensor cell 17 in addition to that the voltage applied to the sensor unit 11 or the current supplied thereto is minute. The sensor cells 17 are arranged with an inclination of 45° to the carrying direction of the inspection object to smooth the detecting sensitivity for slender metallic foreign matter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a foreign matter detection method and a foreign matter detection device for detecting foreign matter mixed in an object to be inspected. The present invention relates to a foreign matter detection method and a foreign matter detection device for detecting a metal object mixed in an inspection object wrapped with a paramagnetic material such as aluminum or copper, or a non-metallic packaging material such as glass, plastic or vinyl. More specifically, the present invention relates to a packaging container made of aluminum vapor deposition or aluminum foil, a foreign matter detection method for detecting a metallic foreign matter in a bag, and a foreign matter detection device.

  In the manufacturing process of food, pharmaceuticals, etc., containers, blades, sieves, etc., such as conveyors, washing machines, stirrers, cutting machines, kneaders, steamers, etc. are subjected to metal fatigue, turning, breaking, peeling, scraping, chipping, etc. As a cause, the broken pieces enter the product as foreign matter. It is important to detect and eliminate these foreign substances, which is essential for the production of safe and guaranteed products. An electromagnetic sensor coil or the like is used for the magnetic metal as means for detecting foreign matter mixed in the object to be inspected.

  The metal foreign matter is often austenitic stainless steel that constitutes the above-described various containers, blades, sieves, and the like. Austenitic stainless steel induces martensitic transformation when plastically deformed and changes to a crystalline structure with weak magnetism. For this reason, if a magnet booster is arranged in the vicinity of the sensor coil, it is possible to enhance the reaction of the lines of magnetic force and detect with high sensitivity. When the inspection object passes through the magnet booster, the magnetism is generated by the magnet booster so that the magnetism is directed in a certain direction and the austenitic stainless steel is transformed into martensite, that is, in the inspection object. The metal foreign matter is magnetized.

  The present applicant has proposed a metal object that is detected by a sensor coil (Patent Document 1). When an AC voltage is applied to two pairs of sensor coils having a structure in which a copper wire coil is wound around an E-type iron core, an alternating magnetic field is generated. At this time, two pairs of sensor coils are connected to form a balanced or unbalanced bridge circuit. As long as the alternating magnetic field does not change, the output current of the bridge circuit is constant.

  When an object to be inspected including a magnetic substance or a magnetized metallic foreign object passes between the upper and lower sides of two pairs of sensor coils generating an alternating magnetic field, the form (formation) of the magnetic field lines of the alternating magnetic field is disturbed. At this time, the current flowing through the sensor coil changes, and the output voltage of the balanced or unbalanced bridge circuit changes. Metal foreign matter can be detected by the change in the output signal voltage.

  The magnet booster is for generating a strong magnetic field and magnetizing a magnetic inspection object, and has a structure having a permanent magnet or the like. Place a magnet booster in front of the sensor coil in the middle of the transport path. The conveying means conveys the inspection object to the sensor coil after passing the vicinity of the magnet booster. When the metal foreign matter contained in the inspection object passes near the magnet booster, it is magnetized. Therefore, the detection sensitivity is improved when detected by the sensor coil.

In addition, the present applicant has proposed a foreign object detection device that can detect the position of a metal foreign object contained in an inspection object using two sensor coils (Patent Document 2). The two sensor coils are arranged so as to have a predetermined angle with respect to a direction orthogonal to the transport direction of the transport path that transports the inspection object. The foreign object detection device can specify the position in the direction orthogonal to the transport direction of the transport path from the time when the metal foreign object passes through each of the two sensor coils.
International Publication WO2003 / 027659 Japanese Patent Application No. 2003-427855

  The conventional sensor coil is disposed in a direction orthogonal to the transport direction and has an elongated shape. When a linear elongated foreign substance passes in the vicinity of the sensor coil, the detection sensitivity of the sensor coil changes greatly depending on the direction of the foreign substance, and has a strong directivity. As shown to a of FIG. 18, when the longitudinal axis of a foreign material is orthogonal to the longitudinal axis of a sensor coil, the response of the sensor coil is maximum. As shown in FIG. 18b, when the longitudinal axis of the foreign matter coincides with the longitudinal axis of the sensor coil and the foreign matter and the sensor coil are parallel, the reaction sensitivity of the sensor coil is low.

  In this way, when the sensitivity of the sensor coil varies depending on the orientation of the foreign object, attempts to improve the sensitivity of only this sensor coil will greatly affect the sensitivity adjustment of the entire device, complicating subsequent circuit design and signal processing. There is a drawback of becoming. Thus, when the foreign object and the sensor coil are parallel and the sensitivity of the sensor coil is reduced, the foreign object may not be detected by the sensor coil.

  The conventional foreign object detection device calculates data detected by both of the two sensor coils and specifies whether or not there is a foreign object in the inspection object. However, when an elongated foreign object is parallel to one sensor coil, it may not be detected by the sensor coil, and this foreign object may not be specified. Therefore, a sensor coil having no directivity is desired.

  Further, when the two sensor coils are arranged so as to have a predetermined angle with each other, there is a drawback that the apparatus becomes large with respect to the foreign material conveyance direction. Further, the sensor coil has an elongated shape, and it has been difficult to freely change its length. In many cases, the aluminum packaging product is shipped from the production line and packaged into a plurality of packages, and then foreign matter is detected. The parts where the products are heat-sealed with aluminum wrapping material overlap to form a package.

  This overlapping heat seal portion has an elongated shape, and if it is orthogonal to the sensor coil, it may cause false detection. In Patent Document 2, the two sensor coils are arranged so as to have a predetermined angle with each other, and the magnet booster is arranged on the belt conveyor so as to be orthogonal to the conveying direction. Even if one sensor coil is parallel to the foreign object, the other is not parallel, so there is an advantage that the foreign object can be detected efficiently.

  However, if the two sensor coils are arranged so as to have a predetermined angle, the distance between one end of each sensor coil and the distance from the other end are different. For this reason, the distance between the magnet booster and the sensor coil differs depending on the portion. The metal object in the object to be inspected is magnetized by the magnet booster, and its magnetic force decreases with time. Since this metal object passes through the magnet booster and arrives at the sensor coil, the distance between the magnet booster and the sensor coil is different, so that the magnetic force is different, which causes false detection.

The present invention has been invented with the above technical background, and achieves the following objects.
The objective of this invention is providing the foreign material detection apparatus which lost the directivity of the sensor by the direction of a foreign material.

  Another object of the present invention is to provide a foreign object detection device having a sensor having a compact structure in a direction in which foreign objects are conveyed and having an outer shape that can be freely changed.

  Still another object of the present invention is to provide a foreign object detection device having a structure that does not detect folds, overlaps, and heat seal portions of a metal packaging material that packages an object to be inspected.

In order to achieve the above object, the present invention employs the following means.
In the foreign matter detection method of the present invention, an object to be inspected is conveyed by a conveyance path, and a magnetic foreign substance mixed in the object to be inspected is detected by a sensor that is arranged in the middle of the conveyance path and generates an alternating magnetic field. In the foreign matter detection method, the sensor is a sensor cell in which a conducting wire is wound around a core through which magnetic flux passes, and the magnetic foreign matter is detected by a plurality of the sensor cells in which the conducting wires are electrically connected in series. To do.

  The foreign matter detection method of the present invention 2 is characterized in that, in the present invention 1, the sensor cells are arranged so as to form two rows orthogonal to the flow direction of the inspection object.

  The foreign matter detection method of the present invention 3 is characterized in that, in the present invention 2, the same row of the conducting wires of the sensor cell is connected in series.

  The foreign matter detection method of the present invention 4 is characterized in that, in the present invention 1 or 2, the core is disposed such that a longitudinal direction of the core has 45 degrees with respect to a transport direction of the transport path. .

  The foreign matter detection method according to the fifth aspect of the present invention is the method according to the fourth aspect, wherein the longitudinal direction of the cores of the sensor cells in one of the two rows and the sensor cells in the other of the two rows are 90 degrees from each other. It arrange | positions so that it may comprise.

In the foreign matter detection method according to the sixth aspect of the present invention, the inspection object is conveyed by a conveyance path, and a magnetic substance mixed in the inspection object is detected by a sensor arranged in the middle of the conveyance path and generating an alternating magnetic field. When the foreign matter detection method for reducing the detection directivity in which the detection sensitivity of the sensor varies depending on the arrangement angle of the longitudinal direction of the magnetic substance and the longitudinal direction of the sensor,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction (z axis) of the transport path.

In the foreign matter detection method of the present invention, the object to be inspected is transported by a transport path, and a magnetic object mixed in the object to be inspected is detected by a sensor arranged in the middle of the transport path and generating an alternating magnetic field. In this case, the heat seal portion of the metal packaging material or the overlapping portion of the packaging material in which the inspection object is packaged has an elongated shape, and the longitudinal direction of the sensor and the longitudinal direction of the sensor are orthogonal to each other, and the sensor reacts greatly thereto. A foreign matter detection method for reducing false detection,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction (z axis) of the transport path.

The foreign matter detection apparatus according to the eighth aspect of the invention transports an object to be inspected by a transport path, and detects a magnetic foreign matter mixed in the object to be inspected by a sensor that is arranged in the middle of the transport path and generates an alternating magnetic field. In the foreign object detection device,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wires are electrically connected in series.

  The foreign matter detection apparatus of the present invention 9 is characterized in that, in the present invention 8, the sensor cells are arranged so as to form two rows orthogonal to the flow direction of the inspection object.

  The foreign matter detection device of the present invention 10 is characterized in that, in the present invention 9, the same wires of the sensor cells are connected in series.

  The foreign matter detection device of the present invention 11 is characterized in that, in the present inventions 7 to 9, the longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction of the transport path.

  In the foreign matter detection device of the present invention 12, in the present invention 9 or 10, the longitudinal direction of each of the cores of the sensor cells in one of the two rows and the sensor cell in the other of the two rows is the same. It is arranged to form 90 degrees.

The foreign matter detection apparatus according to the thirteenth aspect of the present invention conveys an object to be inspected by a conveyance path, and detects a magnetic substance mixed in the object to be inspected by a sensor that is arranged in the middle of the conveyance path and generates an alternating magnetic field. A foreign matter detection device for reducing detection directivity in which the detection sensitivity of the sensor varies greatly depending on the arrangement of the longitudinal axis of the magnetic substance and the longitudinal axis of the sensor,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction (z axis) of the transport path.

The foreign matter detection apparatus according to the fourteenth aspect of the present invention detects a magnetic object mixed in the inspection object by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field. When
The heat seal portion of the metal wrapping material or the overlapping portion of the wrapping material in which the object to be inspected is formed in an elongated shape, and the sensor reacts greatly in the longitudinal direction with the longitudinal direction of the sensor to cause an error. A foreign object detection device for reducing detection,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction (z axis) of the transport path.

According to the present invention, the following effects can be obtained.
The foreign matter detection apparatus of the present invention uses a sensor unit having a plurality of sensor cells in two rows and arranges the sensor cells so as to have, for example, 45 degrees with respect to the transport direction of the transport path, thereby detecting the sensitivity due to the direction of the foreign matter. Can be detected regardless of the direction of foreign matter contained in the inspection object.

  Since the foreign object detection device of the present invention uses a set of sensor units having a plurality of sensor cells, the foreign object detection device has a compact structure in the direction in which the inspection object is conveyed.

  Since the sensor unit of the foreign object detection device of the present invention uses a plurality of small sensor cells, it does not use an elongated iron core like a conventional sensor coil, and the iron core has become lighter.

  The foreign object detection device of the present invention is arranged so that the sensor cell has, for example, 45 degrees with respect to the conveyance direction of the conveyance path, so that the folds, overlaps, and heat of the metal packaging material packaging the object to be inspected are obtained. The seal part is no longer detected.

  In the foreign matter detection device of the present invention, a plurality of sensor cells are arranged in series and arranged in two rows, so that the detection signals are intensified perpendicular to the sensor cells arranged so that the magnetic lines of force generated in one sensor cell are adjacent to each other. High sensitivity can be detected with a synergistic effect.

  Since the sensor unit of the foreign matter detection device of the present invention uses a plurality of sensor cells, the sensor cell can be increased or decreased according to the application, and the length of the sensor unit can be freely changed.

  Since the foreign substance detection device of the present invention uses a sensor unit having a plurality of sensor cells, it can be provided at a lower cost than a conventional sensor coil.

  FIG. 1 shows an outline of a foreign object detection device 1 according to an embodiment of the present invention. The foreign object detection device 1 is for detecting or detecting a metal foreign object mixed in food in an aluminum packaging bag, which is a container for wrapping food, particularly in a test object. Before describing the outline of the configuration of the foreign object detection device 1, the outline of the principle of detection of a metal foreign object of the present invention will be described.

(Detection principle)
FIG. 14A shows a detection circuit for detecting a metallic foreign object according to the present invention. Electric energy is supplied from the variable frequency power source to the detection circuit via the matching transformer Tsr. The detection circuit includes a bridge circuit having a sensor coil. Here, the sensor coil means a coil having a structure in which a conducting wire is wound around a core. For example, a cross-sectional structure is a structure in which a conducting wire is wound along a groove portion of an E-shaped iron core. The sensor coil is responsible for one side of the balanced or unbalanced bridge circuit. The sensor coil has a structure in which a coil is wound around an iron core.

  The sensor coil plays the most important role in this detection circuit. The sensor coil radiates an alternating magnetic field directly to the vicinity of the coil detection surface by an alternating current supplied from a variable frequency power supply, and when the inspection object having a minute metal piece disturbs the magnetic field configuration of the alternating magnetic field. It has both the role of detecting an oscillating magnetic field and creating an output as a foreign object detection signal. Finally, the output from the bridge circuit is amplified by an amplifier and output to the next stage circuit.

  Electric energy of frequency ω is supplied from the variable frequency power supply to both ends of the variable volume VR0 of the bridge circuit via the matching transformer Tsr. The bridge circuit is insulated from the variable frequency power supply by the matching transformer Tsr. One end of the sensor coil is connected to one end of the variable volume VR0, and the other end of the sensor coil is grounded.

  This detection circuit can be shown as an equivalent circuit shown in FIG. The capacitor C shown in FIG. 14B is a stray capacitance of the sensor coil and is not shown in FIG. For convenience of circuit adjustment, a capacitor can be externally connected in parallel with the sensor coil. The inductance Lts in FIG. 14B is an inductance obtained by converting the self-inductance and the mutual inductance of the matching transformer Tsr into the secondary side.

  The equivalent circuit of FIG. 14B can be considered equivalent to the constant current drive circuit of FIG. 15A or the constant voltage drive circuit of FIG. 15B depending on the functional configuration of the variable frequency power supply. The constant current drive circuit in FIG. 15A is a variable frequency power supply that supplies electrical energy from the collector output of a transistor (constant current source), and the constant voltage drive circuit in FIG. It is assumed that this circuit is driven by a low output impedance circuit (constant voltage source).

  The values of the inductance L and the capacitor C are constant values determined by the structure and material of the sensor coil. When the value of the variable resistor VR is fixed at an arbitrary value and the frequency ω of the variable frequency power supply is changed, this circuit Resonates at a certain frequency ω0. This can be explained using a performance factor Q value (Quality factor value) that is often used as a measure of the resonance characteristics of the circuit.

(Calculation of characteristics)
The resonance frequency is expressed by Equation 1, and the impedance Z determined by the ratio of L and C is expressed by Equation 2. For example, when VR is 1 kΩ and Z = 1 kΩ, the figure of merit Q value is Q = 1. When the Q value is a relatively small value, the required VR value can be calculated by Equation 3 from Q.

  Graph 1 in FIG. 16A is an example in which VR is changed stepwise so that the resistance value is increased in the order of VR1 to VR6, and plotted with respect to each frequency, and the vertical axis is a logarithmic scale of impedance Z. It is illustrated by In this graph 1, the normalization frequency 4 is assumed to be the resonance frequency. From the graph 1, the resonance characteristics become sharper as the value of the resistance VR is increased.

  A similar phase characteristic is illustrated in graph 2 of FIG. When the Q value increases, that is, when the value of VR increases, the phase change with respect to the frequency increases. As can be seen from the graphs 1 and 2, the present invention utilizes the characteristic that a large phase shift occurs when the Q value of the detection circuit is set large. The inductance L and stray capacitance C are constant values determined from the material and characteristics of the sensor coil. The inductance L includes a secondary conversion inductance and a mutual inductance of the matching transformer Tsr.

  Therefore, it is possible to set a large Q value by changing the frequency of the power supply and the variable resistance value VR. Actually, the Q value is set according to the size of the metal foreign object in the inspection object, the frequency of the power supply, other elements of the circuit, the characteristics of the subsequent circuit, the characteristics of the amplifier and the like. When the bridge circuit of the detection circuit is unbalanced, the detection circuit is always outputting even when there is no metal foreign object in the inspected hardware. This output is removed by inverting the phase of the power supply frequency in the subsequent circuit. This is performed using a differential amplifier or the like.

  In the present invention, the current flowing through the sensor coil is set to be very small. That is, as shown in FIG. 17, this is the region P1 of the BH characteristic of the iron core constituting the sensor coil. This region is non-linear, and both the magnetic field H and the magnetic flux density B are very small. By using this region, it is possible to detect good sensitivity even when the metal foreign matter in the inspection object is small.

(About minute magnetic fields)
Consider a case where an object to be inspected passes through the vicinity of a coil at a constant passing speed at a constant temperature. At this time, the factors that change the current of the sensor coil are typically eddy current, magnetic permeability, dielectric constant of the object to be inspected, and the magnitude of the speed passing through the vicinity of the sensor coil. It is estimated that the magnetic permeability of the metallic foreign object has the most influence. When the metal foreign object in the object to be inspected is made of a material having a high magnetic permeability, when the minute current as described above is supplied to the sensor coil, the magnetic permeability of the metal foreign object is large in the magnetic field change of the sensor coil. This is to influence.

  As shown in the relative magnetic permeability of metal objects in Table 1, the relative magnetic permeability varies greatly depending on the type of metal. The relative magnetic permeability of metals such as iron, stainless steel, nickel, and cobalt is several hundred to several tens of thousands. In addition, if a weak magnetic field that does not generate eddy currents is applied to a metal with low relative permeability such as aluminum, the reaction of the metal with high relative permeability that is wrapped in aluminum or the like will greatly affect the magnetic field generated by the sensor coil. It will be about to give.

  In the present invention, the metal foreign object is detected by using the phase shift of the current flowing through the sensor coil. Instead, the metal foreign object can be detected by measuring the voltage or impedance applied to the sensor coil. It is. Hereinafter, an invention in which a current flowing through a sensor coil is used as a detection signal will be described.

  In the present invention, an audio region in which the frequency supplied from the variable frequency power supply to the detection circuit is several hundred Hz to several tens kHz is used. More specifically, power is supplied at a frequency near 4.5 kHz or 7 kHz. When such a low frequency is used, the eddy current generated in the metal object contained in the object to be inspected becomes minute due to the alternating magnetic field generated from the sensor coil, and this eddy current causes the influence on the original alternating magnetic field. Almost negligible.

(Consideration of phase shift)
Here, the phase shift will be described. When an active circuit is connected to the input / output of a passive analog circuit, it is necessary to grasp the standing wave as a steady phenomenon from the viewpoint of signal transmission and noise generation. Assume that the low output impedance on the driver side is connected to the high input impedance circuit on the receiver side. This is because when high-gain OP amplifiers are connected by long wires, or a passive circuit having a large inductance that is insulated via the matching transformer Tsr is connected as in the bridge circuit of this embodiment. This is the case.

  If a terminating resistor is inserted on the receiver side to eliminate reflection, the signal advances at a constant speed, and the phase is sequentially shifted depending on the measurement point. However, since the circuit elements are usually connected to each other, they are not terminated, and it is not always easy to achieve matching (perfect matching), so that reflection occurs. Since the signal reciprocates many times due to reflection, resonance occurs and a standing wave is generated, and the entire signal vibrates greatly with the amplitude of the standing wave. This is taken as amplitude modulation.

  At this time, the signals of the respective parts move at the same time, and the phases of the signals of the respective parts are equal, and the progression as a wave does not occur. This is a standing wave. The condition for the resonance to occur is that the length of the signal line related to the signal routed through the circuit is a quarter wavelength of the signal, or an odd multiple of the frequency. Speaking of the resonating detector of the present invention, the sensor coil voltage (or current) of several kHz for generating a magnetic field is amplitude-modulated by this standing wave (about 0.2 Hz to 2 Hz).

(Structure of the foreign object detection device 1)
Next, embodiments of the present invention will be described. FIG. 1 shows an outline of a foreign object detection device 1 according to an embodiment of the present invention. The foreign object detection device 1 is for detecting or detecting a metal foreign object mixed in food in an aluminum packaging bag, which is a container for wrapping food, particularly in a test object. The foreign object detection device 1 includes a belt conveyor 2, a driving motor 4, a sensor storage unit 6, a signal processing unit 13, and the like. The belt conveyor 2 is a belt conveyor mounted on a frame with legs, and is for conveying the inspection object 14 at a constant speed.

  The belt conveyor 2 rotationally drives an endless belt 3 by a driving motor 4 provided on one side of the belt conveyor 2, and an object 14 is placed on the belt 3 and conveyed. A sensor storage unit 6 is disposed in the vicinity of the center in the length direction of the belt 3 in the conveyance path through which the inspection object 14 is conveyed. The sensor storage unit 6 incorporates a first sensor 8, a second sensor 9, an optical sensor 10, and the like for detecting a metallic foreign object in the inspection object 14.

  The sensor storage unit 6 is for detecting a metallic foreign object contained in the inspection object 14 and outputting a detection signal. The detection signal output from the sensor storage unit 6 is sent to the signal processing unit 13. The signal processing unit 13 analyzes the signal from the sensor storage unit 6, determines whether or not there is a metal foreign object in the inspection object 14, and notifies that (warning sound, display, etc.). is there.

  The first sensor 8 and the second sensor 9 have the same structure (details will be described later). As shown in FIG. 1, the signal processing unit 13 is installed on a table provided on the belt conveyor 2. The signal processing unit 13 may be installed anywhere as long as it can receive and process the signal from the sensor storage unit 6.

  The optical sensor 10 is installed on the upstream side of the first sensor 8 (injection side of the inspection object 14) in the conveyance direction of the inspection object 14, and the timing when the inspection object 14 is conveyed and enters the first sensor 8. Is detected, and this detection is transmitted to the signal processing unit 13. As long as the optical sensor 10 can detect the timing when the inspection object 14 enters the first sensor 8, any known shape and method can be used.

  The drive motor 4 is driven to rotate the belt 3. At that time, the inspection object 14 is placed on one side of the belt 3 and conveyed toward the other side. Then, the optical sensor 10 detects the inspection object 14 and notifies the signal processing unit 13 of the timing at which the inspection object 14 enters the first sensor 8. The signal processing unit 13 receives the notification from the optical sensor 10, analyzes the signal of each sensor when the inspection object 14 passes through the first sensor 8 and the second sensor 9, and applies a metal foreign object to the inspection object 14. Whether or not is included.

  When a metal foreign object is included in the inspection object 14, the signal processing unit 13 outputs an output signal to that effect. This output signal is sent to another device (not shown) such as an electric arm provided in or connected to the foreign object detection device 1 to perform necessary processing such as removing the inspection object 14 including the metal foreign object. Is done. Further, in order to grasp the speed of the belt 3 being driven, the signal processing unit 13 needs to be able to receive signals such as the number of rotations of the driving motor 4.

  When a metal foreign object is detected by the sensor storage unit 6, the magnet booster 5 is arranged on the upstream side of the sensor storage unit 6 to magnetize the metal foreign object. The magnet booster 5 is an auxiliary magnetizing device for magnetizing the metal foreign matter in the inspection object 14. When the inspection object 14 passes through the magnet booster 5, the magnetization of the magnetic object in the inspection object 14 becomes strong, so that the detection sensitivity in the sensor storage unit 6 is improved.

  The magnet booster 5 is composed of two pairs of magnets 7 and is arranged above and below the belt 3 so that the inspection object 14 can pass between them. The sensor storage unit 6 includes a first sensor 8 and a second sensor 9. The first sensor 8 is composed of a pair of sensor units 11 arranged above and below the belt 3. Similarly, the second sensor 9 is composed of a pair of sensor units 12. Each sensor unit 11, 12 has an elongated box shape as shown in FIG. 2, is basically the same, and is arranged in parallel with the surface of the belt 3 so as to be orthogonal to the conveying direction of the belt 3. It is fixed.

  FIG. 2 illustrates an outline of a method for arranging the sensor units 11 and 12. The first sensor 8 and the second sensor 9 are installed at a distance L along the belt 3. The first sensor 8 and the second sensor 9 are provided so as to be parallel to the conveying direction of the belt 3. The sensor unit 11 of the first sensor 8 and the sensor unit 12 of the second sensor 9 are provided with a certain gap on the belt 3 so that the inspection object 14 flowing on the belt 3 passes through the sensor unit 11. It is installed above and below.

  The optical sensor 10 installed in front of the first sensor 8 is necessary for specifying the timing at which the inspection object 14 is input to the first sensor 8. The timing at which the inspection object 14 is input to the second sensor 9 can be calculated based on the time input to the first sensor 8, the distance L, and the conveyance speed of the belt 3. The conveying speed of the belt 3 can be calculated from the rotational speed of the driving motor 4. Note that this calculation method is not the gist of the present invention and is a well-known technique, so that the description thereof is omitted.

  Each sensor unit 11, 12 is composed of a plurality of sensor cells 17. The sensor cells 17 constituting the sensor units 11 and 12 basically have the same structure. FIG. 3 illustrates the structure of the sensor cell 17. The sensor units 11 and 12 have substantially the same structure. The sensor cell 17 has a configuration in which a coil 15 is wound along a groove portion of an iron core 16 made of a conductive material having an E-shaped cross-sectional structure. The iron core 16 is configured by laminating plate materials such as a silicon steel plate and an amorphous metal material.

  When the sensor units 11 and 12 are configured of the plurality of sensor cells 17 as described above, the shape and size of the sensor units 11 and 12 can be freely changed by changing the number of sensor cells 17. Moreover, it is possible to obtain the sensor units 11 and 12 having a desired frequency characteristic by changing the material and size of the iron core 16 and the coil 15, and changing the number of windings and the winding method of the coil 15.

  When the sensor cells 17 constituting the sensor units 11 and 12 are approximately square (when viewed in a plan view in FIG. 2), 45 squares are arranged in each side of the conveyor direction of the belt conveyor 3. It is preferable to dispose it at an angle. The sensor cells 17 may not be all oriented in the same direction, but may be arranged so that the angle between the adjacent sensor cells 17 forms an angle of 90 °. As shown in FIG. 2, as a result, sensor cells 17 are formed in two rows in the direction orthogonal to the flow direction of the inspection object 14 and at equal intervals (in the width direction of the conveyance path on the belt 3). With this arrangement, the heat seal portion of the inspection object 14 and the longitudinal axis of the wire foreign matter or the like are not orthogonal to the longitudinal axis of the core of the sensor cell 17, thereby preventing erroneous detection.

  If the shape of the sensor cell 17 changes, the arrangement angle may be different, and the optimum value of the arrangement angle may be determined by looking at the experimental results. When the sensor units 11 and 12 are constituted by a plurality of sensor cells 17 as described above, an elongated iron core is not required as in the conventional sensor coil, and the sensor units 11 and 12 are light.

  FIG. 4 is a circuit diagram showing connection of the sensor cell 17. One sensor unit 11 or sensor unit 12 is composed of two rows of sensor cells 17. These sensor cells 17 are electrically connected in series. Specifically, the sensor cells 17 constituting one row are connected in series so that the winding end of the coil 15 of one sensor cell 17 is connected to the winding start of the coil 15 of another sensor cell 17. The winding start of the coil 15 of the first sensor cell 17 and the winding end of the coil 15 of the last sensor cell 17 are connected to the lead wires. The lead wires are connected to a bridge circuit 22 (see FIG. 5), and the sensor units 11 and 12 including the plurality of sensor cells 17 constitute the bridge circuit 22.

  When an AC power supply of several kHz is applied to the sensor units 11 and 12, an alternating magnetic field is generated in each sensor cell 17. When a small piece of stainless steel approaches the sensor units 11 and 12, for example, austenitic stainless steel (SUS304, etc.) undergoes martensite-induced transformation due to plastic deformation such as fracture, crushing, bending, and chipping, and weak magnetism. The portion with the magnet is magnetized by the action of a static magnetic field to generate a magnetic pole. This change in the magnetic pole affects the alternating magnetic field, and this is detected by the detection circuit.

  In particular, since this effect appears greatly in the vicinity of the sensor units 11 and 12, the sensor units 11 and 12 can reliably detect minute debris. The same applies to the ferromagnetic materials such as iron, nickel, cobalt contaminants, alloys thereof, and martensitic stainless steel, and the detection sensitivity is significantly improved as compared with the prior art. When the paired sensor units 11 are arranged on the two sides of the bridge circuit 22, when a constant AC voltage is applied, the current flowing through the bridge circuit 22 does not change, and the output current of the bridge circuit 22 is constant. When the magnetic material passes in the vicinity of the sensor units 11 and 12, the form of the alternating magnetic field is disturbed, and the output current of the bridge circuit 22 changes.

  This output current is signal-processed by subsequent signal processing circuits 23 to 27 (see FIG. 5) and detected as foreign matter in the inspection object 14. The inspection object 14 is conveyed by the belt 3 and passes through the magnet booster 5. Then, it passes through the sensor units 11 and 12. The conveyance speed of the belt 3 can be adjusted within a predetermined range. When the inspection object 14 passes through the magnetic field generated by the magnet booster 5, the metal foreign matter in the inspection object 14 is magnetized.

  FIG. 6 shows an outline of the lines of magnetic force generated from the sensor cell 17. The lines of magnetic force generated from one sensor cell 17 are orthogonal to both sensor cells 17 arranged adjacent to it. That is, the magnetic force lines generated from one sensor cell 17 form a substantially right angle with the first surface including the magnetic force lines flowing in one sensor cell 17 and the second surface including the magnetic force lines flowing in the other sensor cell 17 orthogonal thereto. Since each sensor cell 17 is electrically connected in series, an excitation current flows in each sensor cell 17 in the same phase, and the magnetic force lines of each sensor cell 17 are also generated in the same phase. The magnetic field lines generated in each sensor cell 17 are orthogonal to the magnetic field lines of adjacent sensor cells 17. For this reason, the magnetic lines of force due to the foreign substance signal generated in one sensor cell 17 can be detected with high sensitivity by a synergistic effect that is orthogonal to the sensor cells 17 adjacent to each other one after another.

  As shown in FIG. 2, the plurality of sensor cells 17 are arranged in two rows and have an angle of 45 degrees with respect to the conveyance direction of the belt 3, so that the direction of the foreign matter contained in the inspection object 14 is not affected. Can be detected. When sealing the inspection object 14 with a packaging material, the packaging material is often fused by high heat, thereby forming a heat-sealed portion. This heat seal portion is almost elongated and is often conveyed perpendicularly or parallel to the conveying direction.

  Therefore, by disposing the sensor cell 17 so as to have 45 degrees with respect to the transport direction, this heat seal portion is not detected. In addition, folds and overlapping parts due to folding and overlapping each packaging material of the object to be inspected 14 are often transported at right angles or parallel to the transport direction in the same manner as the heat seal part, and these parts are detected. No longer.

[Configuration of Signal Processing Unit 13]
FIG. 5 is a functional block diagram showing an outline of the signal processing unit 13. The signal processing unit 13 includes an oscillation circuit 21, a bridge circuit 22, an aluminum signal elimination circuit 23, an amplification / phase conversion circuit 24, an amplification / phase inversion circuit 25, a waveform processing unit 26, a digital computer processing unit 27, a signal output unit 28, and the like. It is composed of

  The oscillation circuit 21 is a circuit for supplying AC power to the signal processing unit 13 and the sensor units 11 and 12. The oscillation circuit 21 supplies AC power via a transformer. By using the transformer, there is an advantage that the measurement part including the power supply circuit and the sensor units 11 and 12 and the bridge circuit 22 can be regarded as an independent circuit. The bridge circuit 22 is a circuit that receives signals from the sensor units 11 and 12.

  The signal from the bridge circuit 22 is sent to the aluminum signal erasing circuit 23, and the aluminum signal erasing circuit 23 cancels the signal from the aluminum package, which is a conductive material contained therein. The signal processing at this time is performed as follows using the signal of the amplification / phase inversion circuit 25. The amplification / phase inversion circuit 25 takes out the current from the oscillation circuit 21 and amplifies it to invert the phase.

  The aluminum signal erasing circuit 23 calculates the sum of the signal (detection current) from the bridge circuit 22 and the phase inversion current from the amplification / phase inversion circuit 25 and erases the signal (original current) of the AC power supply. Then, only signals having a certain threshold value or more are extracted and the noise signal is canceled.

  Next, the signal output from the aluminum signal erasure circuit 23 is amplified by the amplification / phase conversion circuit 24, subjected to phase conversion adjustment processing, and output to the waveform processing unit 26. The waveform processing unit 26 shapes the waveform of the input signal, converts it into a digital signal, adjusts the reception sensitivity, and outputs the digital signal to the digital computer processing unit 27. The threshold processing provided in the aluminum signal erasing circuit 23 may be performed in the waveform processing unit 26. At this time, threshold processing is performed on the signal converted into the digital signal.

  The digital computer processing unit 27 includes a memory circuit, an arithmetic circuit, an amplitude comparison / signal extraction circuit, a belt speed timing circuit, and the like. The digital computer processing unit 27 receives information on the rotational speed of the motor from the driving motor 4 and calculates the speed at which the belt 3 flows. Further, the digital computer processing unit 27 receives a signal of the inspection object 14 from the optical sensor 10 and obtains information that the inspection object 14 passes through the sensor units 11 and 12.

  Therefore, the digital computer processing unit 27 receives the digital signal from the waveform processing unit 26, and detects the metallic foreign matter contained in the inspection object 14 together with the belt speed, the passing signal of the inspection object 14, and the like. To do. When the digital computer processing unit 27 determines that a metal foreign object has been detected, the digital computer processing unit 27 outputs a signal of the metal foreign object to the signal output unit 28.

  FIG. 7 is a flowchart when the digital computer processing unit 27 detects a metallic foreign object. In the digital computer processing unit 27, the determination of the metallic foreign object is always performed based on the sensing signal of the optical sensor 10. When the digital computer processing unit 27 waits for a certain period of time (step 1), it checks whether there is a signal from the optical sensor 10 (step 2). When the inspection object 14 passes through the optical sensor 10 (see FIG. 2), a signal indicating that the inspection object 14 is passing is output to the signal processing unit 13. The digital computer processing unit 27 receives this signal.

  When it is determined that the inspection object 14 is passing (step 2, yes), the rotational speed of the drive motor 4 is received (step 3). Using this rotational speed, the conveyance speed of the belt 3 is calculated (step 4). Thereafter, the digital signal of the first sensor 8 from the waveform processing unit 26 is received (step 5) and stored in the memory area (step 6). Similarly, the digital signal of the second sensor 9 is received (step 7) and stored in the memory area (step 8).

  The digital signals of the first sensor 8 and the second sensor 9 stored in the memory area are compared and calculated (step 9), and it is determined whether or not there is a foreign substance in the inspection object 14 (step 10). As a result of the determination, if it is determined that there is no foreign object (No in Step 10), the process waits for a predetermined time (Step 1). If it is determined that there is a foreign object (step 10, yes), a signal to that effect is output (step 11). Therefore, a series of metal foreign matter determinations are made.

(Explanation of detection circuit)
FIG. 8 illustrates the detection circuit 100. The above-described oscillation circuit 21, bridge circuit 22, and sensor units 11 and 12 will be described together as a detection circuit 100. In the detection circuit 100 of FIG. 8, the pair of sensor units 11 are a bridge circuit 101 and a bridge circuit 102. The sensor cells 17 constituting the sensor unit 11 are equivalently indicated by L1 and L2. There is a similar detection circuit 100 for the sensor unit 12. Hereinafter, only the sensor unit 11 will be described as an example.

  The sensor unit 11 bears one side of the bridge circuits 101 and 102. The sensor unit 11 directly radiates an alternating magnetic field to the vicinity of the coil detection surface by the supplied alternating current, and detects the oscillating magnetic field when the inspection object 14 having a minute metal piece disturbs the configuration of the alternating magnetic field. To produce an output as a foreign object detection signal.

  The detection circuit 100 includes bridge circuits 101 and 102, and the sensor unit 11 bears one side (arm) of the unbalanced bridge circuits 101 and 102. The bridge circuits 101 and 102 are supplied with electric energy having a frequency ω from a variable frequency power source 103 via a matching transformer 108. The bridge circuits 101 and 102 including the sensor unit 11 are insulated from the variable frequency power supply 103 by the matching transformer 108.

  As illustrated, the detection circuit 100 includes a plurality of resistors R1 to R6 connected in series or in parallel. One lead wire from the sensor unit 11 is connected to one end of the resistor, and the other lead wire from the sensor unit 11 is grounded. During normal and non-detection, the sensor unit 11 is balanced (see FIG. 9), and no signal is output from the output 104. When the metal foreign matter contained in the inspection object 14 passes between the two sensor units 11, this state is changed and an output signal is output from the output 104.

  Alternatively, when the detection circuit 100 is set, the detection circuit 100 may be set to output from the output 104 even when it is not detected. In this case, the bridge circuits 101 and 102 are unbalanced. FIG. 9 illustrates the frequency characteristics of the bridge circuits 101 and 102 including the sensor unit 11. The horizontal axis is a frequency axis indicating frequency, and the vertical axis is an axis indicating wave intensity. Although the sensor unit 11 is composed of the same inductor, it rarely operates at the exact same frequency due to a manufacturing accuracy error or the like.

  As described in the above principle, the detection circuit 100 is set by supplying a low-frequency power supply of around 7 kHz and changing the frequency of the power supply and the resistance values (R1 to R6) to obtain a high Q value. Set as follows. If the center frequencies of the sensor unit 11 are ω01 and ω02, respectively, they are separated by Δω (= | ω01−ω02 |). FIG. 9 shows the characteristics of the sensor unit 11 with graphs 105 and 106, and the sum is a graph 107. The center frequency of the graph 107 is ω0.

  When the metal foreign object does not pass around the sensor unit 11, the detection circuit 100 is in the state of ω0. When a metal foreign object passes around the sensor unit 11, the metal foreign object affects the magnetic field of the sensor unit 11, the frequencies ω01 and ω02 of the sensor unit 11 change, and the center frequency ω0 of the entire detection circuit 100 also changes. Therefore, a detection signal is output from the output 104 of the detection circuit 100.

  As described above, when the two circuits are used, the center frequency of the center frequency ω0 fluctuates in response to a slight change in the magnetic field of the sensor unit 11, and a metal foreign object can be detected with high sensitivity. Note that the detection circuit 100 may include only one sensor unit 11 and detect a metal foreign object.

  The digital computer processing unit 27 shown in FIG. 5 analyzes the frequency / waveform constituting the digital signal by using a technique such as Fourier transform, identifies the cause of these frequency / waveform, and detects the metallic foreign matter. May be detected. For this purpose, analysis data on the frequency and waveform prepared in advance is necessary.

  In the digital computer processing unit 27, the signal of the AC power source (AC excitation power source) performed by the aluminum signal erasing circuit 23 may be similarly erased. The signal input to the aluminum signal erasing circuit 23 is converted into a digital signal and input to the digital computer processing unit 27. Then, the digital signal is demultiplexed for each frequency, and a signal caused by an AC power source, noise, or the like is deleted. Similarly, the frequency and waveform of the noise signal from the inspection object 14 may be deleted by analysis.

  10 to 13 illustrate the circuit configuration of the signal processing unit 13. The signal of the circuit handled here is processed by an analog circuit. The signal output from the bridge circuit 22 may be digitized, and thereafter all or part of the above-described aluminum signal elimination, phase conversion / waveform shaping, sensitivity adjustment, etc. may be digitally computer processed.

  Only the outline of the important parts of the circuit will be described below. FIG. 10 illustrates an AC power supply 109, a sensor circuit 110, and a phase inversion circuit 111. The AC power supply 109 is the oscillation circuit 21 shown in FIG. Similarly, the sensor circuit 110 is a circuit in which the sensor units 11 and 12 and the bridge circuit 22 are combined, and the phase inversion circuit 111 is an amplification / phase inversion circuit 25 (see FIG. 5).

  FIG. 11 illustrates the differential amplifier circuit 112 and the waveform shaping circuit 113. The differential amplifier circuit 112 is an aluminum signal erasing circuit 23 and an amplification / phase conversion circuit 24, and the waveform shaping circuit 113 is a waveform processing unit 26 (see FIG. 5). The sensor circuit 110 is a sensor circuit that receives a signal from the inspected object 14, and the signal is output to the output “1”, and is input to the differential amplifier circuit 112 from “1” in FIG. 11.

  The phase conversion circuit 111 shown in FIG. 10 extracts a signal from the AC power supply 109, adjusts the phase, and outputs the signal from “2”. This is “2” in FIG. 11 and is input to the differential amplifier circuit 112. The differential amplifier circuit 112 is a circuit for removing a signal from the AC power supply 109 from the received signal, that is, a signal output from the sensor circuit 110. Only the signal from the inspection object 14 is taken out from the differential amplifier circuit 112, and the waveform is shaped by the circuit 113 and output.

  12 and 13 are circuits for analyzing the signal of the object to be inspected 14 and perform analog processing. This part may be digitized and computer processed. FIG. 12 shows a rectifier circuit 114, an amplifier circuit 115, a rectifier circuit 116, an amplifier circuit 117, a DC power supply cut circuit 118, and a waveform processing circuit 119. FIG. 13 illustrates a sensitivity adjustment circuit 120, a waveform threshold circuit 121, and an amplifier circuit 121.

  The rectifier circuits 114 and 116 are circuits for rectifying the signal and adjusting the waveform. The amplifier circuits 115, 117, and 122 are circuits for amplifying signals. The DC power supply cut circuit 118 is a circuit for cutting a DC signal included in the signal. The waveform processing circuit 119 is a circuit for forming the waveform of the signal of the inspection object 14. The sensitivity adjustment circuit 120 is a circuit for adjusting the detection sensitivity of the inspection object 14. The detection sensitivity can be set by changing the resistance value of this circuit. The waveform threshold circuit 121 is a circuit for adjusting the level of the output signal.

  INDUSTRIAL APPLICABILITY The present invention can be used in the field of detecting magnetic metallic foreign matter mixed in an inspection object such as frozen food, food materials such as cereals, industrial materials such as pharmaceuticals and paints. In particular, the present invention can be used in the field of detecting metallic foreign matter of a magnetic substance mixed in an object to be inspected that is wrapped with a conductive packaging material such as aluminum vapor deposition or aluminum foil.

FIG. 1 is a diagram illustrating an outline of a foreign object detection device 1 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration example of the sensor units 11 and 12. 3A and 3B are diagrams illustrating the structure of the sensor cell 17. FIG. 3A is a top view, FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A, and FIG. It is sectional drawing of the BB line of Fig.3 (a). FIG. 4 is a circuit diagram showing connection of the sensor cell 17. FIG. 5 is a functional block diagram showing the configuration of the signal processing unit 13 of the foreign object detection device 1. FIG. 6 is a diagram illustrating an outline of the lines of magnetic force generated from the sensor cell 17. FIG. 7 is a flowchart showing an operation example of the digital computer processing unit 27 of the signal processing unit 13. FIG. 10 illustrates an outline of the detection circuit 100 including the sensor unit 11. FIG. 9 is a diagram illustrating the frequency characteristics of the detection circuit 100. FIG. 10 is a circuit diagram illustrating a circuit example. FIG. 11 is a circuit diagram illustrating a circuit example. FIG. 12 is a circuit diagram illustrating a circuit example. FIG. 13 is a circuit diagram illustrating a circuit example. 14A and 14B show the detection circuit 100, FIG. 14A shows an outline of the detection circuit, and FIG. 14B shows an equivalent circuit thereof. FIGS. 15A and 15B are diagrams showing a simplified circuit of the equivalent circuit of FIG. 14B. FIGS. 16A and 16B are graphs showing the characteristics of the circuit of FIG. FIG. 17 is a diagram illustrating the BH characteristics. FIG. 18 is a conceptual diagram showing the directivity of the detection sensitivity of the sensor coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Foreign object detection apparatus 2 ... Belt conveyor 3 ... Belt 4 ... Motor for drive 5 ... Magnet booster 6 ... Sensor storage part 7 ... Permanent magnet 8 ... 1st sensor 9 ... 2nd sensor 10 ... Optical sensor 11, 12 ... Sensor unit 13 ... Signal processing unit 14 ... Inspected object 17 ... Sensor cell

Claims (14)

In the foreign object detection method of detecting a magnetic foreign object mixed in the inspection object by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
The sensor is a sensor cell in which a conducting wire is wound around a core through which magnetic flux passes, and the magnetic foreign matter is detected by a plurality of the sensor cells in which the conducting wires are electrically connected in series. In the foreign matter detection method of claim 1,
The said sensor cell is arrange | positioned so that two rows orthogonal to the flow direction of the said to-be-inspected object may be formed. The foreign material detection method characterized by the above-mentioned. In the foreign matter detection method of claim 2,
The said conductor of the said sensor cell is connected to the same said row | line | column in series. The foreign material detection method characterized by the above-mentioned. In the foreign matter detection method according to claim 1 or 2,
The foreign matter detection method, wherein the core is disposed such that a longitudinal direction of the core has 45 degrees with respect to a transport direction of the transport path. In the foreign matter detection method of claim 4,
The sensor cells in one row of the two rows and the sensor cells in the other row of the two rows are arranged such that the longitudinal directions of the cores form 90 degrees with each other. Method. When a magnetic object mixed in the inspection object is detected by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
A foreign matter detection method for reducing detection directivity in which detection sensitivity of the sensor varies depending on an arrangement angle between the longitudinal direction of the magnetic substance and the longitudinal direction of the sensor,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The foreign matter detection method, wherein the longitudinal direction of the core is arranged to have 45 degrees with respect to a transport direction (z axis) of the transport path. When a magnetic object mixed in the inspection object is detected by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
The heat seal portion of the metal wrapping material or the overlapping portion of the wrapping material in which the object to be inspected is formed in an elongated shape, the longitudinal direction of which is perpendicular to the longitudinal direction of the sensor, and the sensor reacts greatly to it. A foreign object detection method for reducing false detection,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The foreign matter detection method, wherein the longitudinal direction of the core is arranged to have 45 degrees with respect to a transport direction (z axis) of the transport path. In the foreign object detection device that detects the magnetic foreign object mixed in the inspection object by the sensor that conveys the inspection object by the conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wires are electrically connected in series. In the foreign matter detection device according to claim 8,
The foreign matter detection device, wherein the sensor cells are arranged so as to form two rows orthogonal to the flow direction of the inspection object. In the foreign matter detection device according to claim 9,
The foreign substance detection device, wherein the conducting wires of the sensor cell are connected in series to the same row. 10. The foreign object detection device according to claim 1, wherein the foreign object detection device is selected from claims 7 to 9.
The foreign matter detection device, wherein the longitudinal direction of the core is arranged to have 45 degrees with respect to the transport direction of the transport path. In the foreign matter detection device according to claim 9 or 10,
The sensor cells in one row of the two rows and the sensor cells in the other row of the two rows are arranged so that the longitudinal directions of the cores form 90 degrees with each other. apparatus. When a magnetic object mixed in the inspection object is detected by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
A foreign matter detection device for reducing detection directivity in which the detection sensitivity of the sensor varies greatly depending on the arrangement of the longitudinal axis of the magnetic substance and the longitudinal axis of the sensor,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The foreign matter detection device, wherein the longitudinal direction of the core is arranged to have 45 degrees with respect to a transport direction (z axis) of the transport path. When a magnetic object mixed in the inspection object is detected by a sensor that conveys the inspection object by a conveyance path, is arranged in the middle of the conveyance path, and generates an alternating magnetic field,
The heat seal portion of the metal wrapping material or the overlapping portion of the wrapping material in which the object to be inspected is formed in an elongated shape, and the sensor reacts greatly in the longitudinal direction with the longitudinal direction of the sensor to cause an error. A foreign object detection device for reducing detection,
The sensor is a sensor cell in which a conducting wire is wound around a core, and includes a plurality of the sensor cells in which the conducting wire is electrically connected in series.
The foreign matter detection device, wherein the longitudinal direction of the core is arranged to have 45 degrees with respect to a transport direction (z axis) of the transport path.

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