JP6425108B1 - metal detector - Google Patents

Abstract

An object of the present invention is to detect metal foreign objects with high accuracy while dealing with various inspection objects without increasing the size and cost of the apparatus. A transport unit (3A) for transporting an inspection object (50), a detection unit (5A) including a sensor coil (10) and a detection magnetic field forming unit (11) disposed opposite to each other across the transport path, and a detection magnetic field forming unit (11). Control unit 2 that determines the presence or absence of a metal foreign object from the signal of the sensor coil 10 that detects fluctuations in the magnetic field for detection due to the control unit 2 that detects the metal foreign object notifies it or / and excludes the inspection object In the metal detector 1A, the booster magnet 12 is disposed at a position spaced apart from the side surface of the sensor coil 10 along the longitudinal direction of the transport path so that the magnetizing magnetic field partially overlaps the detection magnetic field on the transport path side. The magnetic field for magnetization forms a spot in which the magnetic flux density is partially sparse in the detection magnetic field to change the magnetic gradient, and temporarily magnetizes the metal foreign substance in the inspection object 50. [Selected figure] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a metal detector for detecting metal foreign matter mixed in a product, and in particular, it is inexpensive and expensive for various objects to be inspected including those that generate an eddy current by passing a detection magnetic field. The present invention relates to a metal detector that exhibits a detection function.

  There are known various types of metal detectors for detecting ferromagnetic metal foreign substances mixed in products, and for example, as described in JP-A-10-88469, above the search coil A permanent magnet is disposed to detect a change caused by passing a magnetic field by a product containing metallic foreign matter as an electrical signal, or a metallic foreign substance in a product is irradiated with an electromagnetic wave by energizing the electromagnetic wave radiation coil. It is known that metal foreign matter is detected by detecting a response magnetic field of the generated eddy current with a sensor coil.

  However, if the object to be inspected is a product covered with an electrically conductive package such as an aluminum vapor deposition laminate or an aluminum foil or a product in which a high concentration electrolyte solution is enclosed, the package passes the magnetic field. Also, it is known that an eddy current is generated in the product itself to form an eddy current magnetic field, making it difficult to detect metal foreign substances in the product. Moreover, in the method of arranging a permanent magnet opposite to the sensor coil, it is easy to be stable in a state in which the magnetic field formed between the sensor coil and the sensor coil is arranged, so that the reaction with the small metallic foreign matter becomes dull There is.

  In order to cope with such a problem, Japanese Patent Laid-Open No. 2003-66156 arranges a booster magnet as a magnetizing means for metallic foreign matter at a distant position on the upstream side of the sensor coil and makes the detection magnetic field vor Metal detectors have been proposed which are designed to avoid false detections at levels where current does not occur. In this method, aluminum packaging products and electrolyte encapsulation products themselves are nonmagnetic materials and therefore can not be magnetized by the magnetizing means, but since eddy currents are generated while passing through the magnetic field for magnetization, they are affected by the magnetic fields. The magnetism remaining in the metal foreign object is detected by a sensor coil disposed at a distant position.

  However, in this method, because it is necessary to secure a sufficient distance between the sensor coil and the booster magnet as described above, it is also difficult to detect demagnetized metal foreign particles at the time when they reach the sensing position. In addition, since it is difficult to shorten and reduce the size of the airframe to secure the interval, there is also a problem that it is difficult to secure the removal timing of a long product and a desired tact time.

  On the other hand, in the sensor body 10B, the inventors of the present application arrange the permanent magnet 13 in contact with the core 10c of the sensor coil 10 as shown in FIG. We have proposed a method of detecting the reaction of metallic foreign matter with a relative permeability larger than that of aluminum packaging by applying a weak static magnetic field to such an extent that eddy currents do not occur. As described above, by integrating the permanent magnet 13 with the sensor coil 10, it is possible to realize downsizing of the airframe and shortening of the line length while facilitating control timing.

  However, in the system using a weak magnetic field as described above, a large amplification factor is required to obtain a practical foreign matter output signal, and there is also a problem that it is easily influenced by external noise. On the other hand, although it is also conceivable to surround the entire sensing area with a shield as in the method of Patent Document 1, this results in an increase in the size of the device and a rise in manufacturing costs. Moreover, in the system which arrange | positions a permanent magnet in close contact with the core of a sensor coil, it turns out that a core becomes permanent magnet by aging and the reaction to a minute metallic foreign substance becomes blunt.

Japanese Patent Application Laid-Open No. 10-88469 Japanese Patent Application Laid-Open No. 2003-66156 JP 2004-85439 A

  The present invention is intended to solve the above-mentioned problems, and can detect metal foreign objects with high accuracy while dealing with various inspection objects without increasing the size and cost of the apparatus. To be an issue.

  Therefore, the present invention provides a transport means for transporting an object to be inspected, a metal sensor provided with a sensor coil oppositely disposed across the transport path by the transport means, and a magnetic field forming means for detection, and a magnetic field forming means for detection thereof. And control means for determining the presence or absence of a metal foreign object from the signal of the sensor coil which detects the fluctuation of the detection magnetic field, and the control means for detecting the metal foreign object in the inspection object moving on the conveyance path In the metal detector that informs the user or / or removes the inspection object, the booster magnet for magnetizing foreign metal is used to magnetize the position away from the side surface of the sensor coil along the longitudinal direction of the transport path. The magnetic field is disposed on the transport path side so as to partially overlap with the detection magnetic field, and the magnetization magnetic field causes the detection magnetic field to form spots where the magnetic flux density is partially sparse. Temporarily magnetized metallic particles of the specimen in with a state given spatial variations in the magnetic gradient of the use field, and shall be characterized in that.

  As described above, by arranging the booster magnet at a predetermined position on the side of the sensor coil disposed opposite to the detection magnetic field forming means for forming the detection magnetic field, the metal foreign matter can be removed without increasing the size and cost of the apparatus. A high detection function by magnetization can be realized, and a bias type metal sensor corresponding to various objects to be inspected is configured, and the booster magnet is disposed at a side position where the magnetization magnetic field overlaps the detection magnetic field. Therefore, the spot for which the magnetic flux density is sparse is formed in the detection magnetic field, thereby distortion is applied to the formation of the spatial magnetic field to realize the improvement of the detection sensitivity, and the booster magnet serves as the core. The absence of contact makes it difficult to cause the core to become magnetized due to long-term use, making it easy to maintain high detection functions for many years.

  In addition, in this metal detector, the booster magnet is disposed at a position 10 to 20 mm away from the side surface of the core of the sensor coil, in which the magnetizing magnetic field of the booster magnet is detected. Of the magnetic field gradient, thereby minimizing the influence on detection due to the formation of spots where the magnetic flux density of the detection magnetic field is sparse, thereby minimizing the influence on detection. While realizing the detection accuracy and the detection sensitivity, it is possible to reliably prevent the core from being magnetized.

  In this case, if the booster magnet is disposed on the downstream side of the sensor coil, a more excellent detection function can be easily exhibited.

  Furthermore, in the metal detector described above, a range excluding the front surface which is the opposite surface to the sensor coil of the detection magnetic field forming means and the area to the front intermediate position of the right and left side surfaces perpendicular to the transport direction is covered. A shield plate of permalloy made of magnetic field lines is disposed so as to form a U-shaped shield surface with a vertical cross section at a predetermined distance from the left and right side surfaces and the back surface of the magnetic field forming means for detection. If it is characterized, the influence of external noise can be reduced while minimizing the deterioration of the detection function due to the presence of the shield.

  In this case, if the distance between the inner surface of the shield plate and the magnetic field forming means for detection is the same size as the lateral width of the magnetic field forming means for detection, the shield plate It is possible to minimize the reduction in the arrival level of the magnetic field lines to the sensor coil due to the arrangement at low cost.

  In addition, in the metal detector described above, the transport means is formed by a plurality of rollers arranged in parallel with the axis perpendicular to the transport direction, and the downstream side of the transport surface is lowered. As described above, the apparatus is characterized in that it can be supported in the inclined state with a predetermined accuracy, and the inspection object placed on the upstream side of the metal sensor automatically moves on the transport surface downstream due to its own weight. In this case, the size reduction and the cost reduction of the apparatus can be easily realized because the arrangement of the driving means and the driving power source are not required.

  According to the present invention in which the booster magnet is disposed adjacent to the side of the sensor coil disposed opposite to the magnetic field forming means for detection, accuracy can be achieved while dealing with various products without increasing the size and cost of the apparatus. It can detect metal foreign objects high.

It is a front view of the metal detector which is a 1st embodiment in the present invention. It is the expanded longitudinal cross-sectional view of the detection part in the metal detector of FIG. It is a top view which shows the positional relationship of the sensor coil in a detection part of FIG. 2, and a booster magnet. It is a functional block diagram of the metal detector of FIG. It is a front view of the metal detector which is 2nd Embodiment in this invention. It is a front view which shows the use condition of the metal detector of FIG. It is a simulation image which shows the state of the magnetic force line at the time of removing a booster magnet and a shield board from the detection part of FIG. It is a simulation image which shows the state of the magnetic flux density in the detection part of FIG. It is a simulation image which shows the state of the line of magnetic force at the time of arranging a shield board close to the detection magnetic field formation device in the detection part of FIG. It is a simulation image which shows the state of the magnetic flux density in the detection part of FIG. It is a simulation image which shows the state of the magnetic force line at the time of changing the shield board of FIG. 9 into the shield board of FIG. It is a simulation image which shows the state of the magnetic flux density in the detection part of FIG. It is a simulation image which shows the state of the magnetic force line at the time of closely arranging booster magnet on the side surface of the sensor coil of FIG. It is a simulation image which shows the state of the magnetic flux density in the detection part of FIG. It is a simulation image which shows the state of the magnetic force line at the time of arrange | positioning the booster magnet of FIG. 13 in the position away from the side surface of a sensor coil similarly to FIG. It is a simulation image which shows the state of the magnetic flux density in the detection part of FIG. It is an expanded longitudinal section showing composition of a sensor coil by a conventional example.

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

  FIG. 1 shows a metal detector 1A according to a first embodiment of the present invention. The metal detector 1A includes a transport unit 3A as a transport unit including a conveyor belt 30 operating on an infinite loop track by driving a motor (not shown), and a lower surface of the conveyor belt 30 midway along a transport path by the transport unit 3A. A detection unit 5A comprising a sensor body 10A disposed and a detection magnetic field forming device 11 as a detection magnetic field forming means disposed opposite thereto above the sensor body 10A, and determination of the presence or absence of metal foreign matter The control unit 2 includes the microcomputer 20 as control means for executing various controls including the above, and an electric signal detected when passing the upper side of the sensor body 10A for the inspection object 50 conveyed from the upstream side of the conveyance path The microcomputer 20 determines the presence or absence of metal foreign matter based on the above.

  FIG. 2 shows a longitudinal cross-sectional view of the detection unit 5A of the metal detector 1A described above cut along a surface along the transport direction. In this detection unit 5A, a detection magnetic field forming unit 11 is provided which is a detection magnetic field forming means by a permanent magnet for forming a detection magnetic field on the inside upper part of an arched gate 14 through which a conveyance path by a conveyor belt 30 penetrates. A sensor body 10A consisting of a sensor coil 10 and a booster magnet 12 arranged in parallel to the sensor coil 10 is disposed at the lower inside of the gate 14 located below the conveyor belt 30.

  FIG. 3 shows a detailed configuration of the above-described sensor body 10A in a plan view. The sensor body 10A includes a sensor coil 10 in which a conductive wire 10a is wound around a core 10b of E-shaped cross section formed by laminating thin silicon steel plates in a bar shape, and a direction along the transport direction of the side of the core 10b. A booster magnet 12 is provided which is disposed in parallel at intervals W to form a magnetizing magnetic field on the transport path side and temporarily magnetizes metal foreign matter. The booster magnet 12 is a sensor coil 10. On the other hand, it is characterized in that the longitudinal direction perpendicular to the transport direction is arranged in parallel and adjacent to each other at a position where the sides are not in close contact.

  As described above, the booster magnet 12 is disposed adjacent to the side of the sensor coil 10, so that metal foreign objects can be temporarily removed without increasing the size and cost of the apparatus as in the conventional bias type metal sensor. Although it becomes possible to magnetize and enhance detection accuracy, the booster magnet 12 is disposed at a position separated appropriately from the side surface of the sensor coil 10 in the direction along the transport direction, so that distortion in the detection magnetic field occurs. As a result, the detection sensitivity is improved, and the core 10b of the sensor coil 10 is difficult to magnetize even when used for a long time, so it is easy to maintain high detection capability for many years.

  As the position of the booster magnet 12, it is appropriate for the magnetic gradient of the detection magnetic field to be disposed at an interval W of 10 to 20 mm in the direction along the longitudinal direction of the transport path from the side surface of the core 10b of the sensor coil 10. Experiments have shown that it is preferable from the viewpoint of detecting in the state where the metal foreign matter is sufficiently magnetized while keeping a change.

  By adopting such a configuration, it is possible to realize high detection accuracy and detection sensitivity, and to reliably prevent the core 10b of the sensor coil 10 from being magnetized for use over time. In this case, it is clear from experiments that the detection sensitivity is likely to be higher when the booster magnet 12 is disposed downstream of the sensor coil 10 than when the booster magnet 12 is disposed upstream.

  Further, as shown in FIG. 2, the height of the upper surface of the booster magnet 12 is set on the side of the sensor coil 10 lower than the upper surface as shown in FIG. While suppressing the formation of the void (spot) where the detection magnetic field is sparse due to the interaction of the magnetic field by the magnetic field generator 11 in a proper state, this is lowered to a position lower than the sensing position to ensure detection accuracy and detection sensitivity It is easy to do.

  Referring again to FIG. 2, in the present embodiment, the front side opposite to the sensor coil 10 of the detection magnetic field forming device 11 and the part excluding the front side intermediate position of the right and left sides perpendicular to the transport direction are covered. Thus, the shield plate 111 for blocking magnetic lines of force has a predetermined distance between the inner side surface and the left and right side surfaces and the back surface of the detection magnetic field forming device 11 to form a U-shaped shield surface with a vertical cross section downward. It is arranged as Thereby, the influence of external noise can be sufficiently reduced while avoiding the attenuation of the magnetic lines of force reaching the sensor coil 10.

  In this case, permalloy (relative magnetic permeability of 200,000 to 600,000) is preferable as the material of the shield plate 111 from the viewpoint of the balance between cost and function. The distance between the inner side surface of the shield plate 111 and the left and right side surfaces and the back surface of the detection magnetic field forming device 11 is set to the same size as the left and right width of the detection magnetic field forming device 11 as shown in FIG. It is preferable from the viewpoint of minimizing the attenuation of the magnetic field lines reaching the sensor coil 10 due to the presence of 111.

  FIG. 4 is a functional block diagram for explaining the configuration of the detection unit 5A, which is a metal sensor provided with the above-described sensor body 10A, and the principle thereof. The detection unit 5A detects the influence given to the detection magnetic field when the metallic foreign matter temporarily magnetized by the action of the booster magnet 12 passes under the detection magnetic field forming device 11 as an electric signal by the sensor coil 10 The detected signal is amplified by the amplifier circuit 21 of the control unit 2 and is input to the microcomputer 20 through the filter 22 to determine the presence or absence of metal foreign matter contamination.

  FIG. 5 shows a metal detector 1B according to a second embodiment of the present invention. The metal detector 1B is formed by a plurality of rollers (plastic rollers) 310 instead of the motor-driven conveyor belt 30 in the above-described transport unit 3A of the metal detector 1A as transport means in the transport unit 3B. It is characterized in that the driving method using gravity is realized by the conveyance surface 31 (illustration of the control unit is omitted).

  That is, in the transport unit 3B, the transport surface 31 is formed by a plurality of rollers 310 arranged in parallel in a bead shape of an abacus with the axis perpendicular to the transport direction, as shown in FIG. By supporting the transport unit 3B in a state in which the downstream side of the transport surface 31 is inclined with a predetermined accuracy, the inspection object 50 placed on the transport surface 31 on the upstream side of the metal sensor 10A is automatically transported by its own weight. 31 is to move downstream on the top.

  Therefore, the arrangement of the drive means such as the motor and the drive power source for the arrangement are not required, so it is easy to realize the reduction of the weight and size of the device and the introduction and maintenance cost. In addition, it is easy for the operator to handle and maintain, and there is no need to worry about pinching fingers with the conveyor belt, so it can be said that the device can be handled safely and safely.

  Furthermore, in the present embodiment, the transport unit 3B having the transport surface 31 formed of the plurality of rollers 310 on the upper surface side and the downstream side being pivotally supported on the base side locks the upstream side by the support arm 32. The inclined position of the transport surface 31 is set to 0 while changing the support height on the upstream side of the transport surface 31 by appropriately changing the locking position of the support arm 32. Since the adjustment can be made in the range of -30 degrees, the transport speed of the inspection object 50 can be easily adjusted.

  In addition, in the detection unit 5B, the gate 15 having the detection magnetic field forming device 11 at the upper inside thereof corresponds to the locking position of the screw to the main body of the conveyance unit 3B in the slide grooves 151 and 152 provided thereon. The height position of the gate 15 can be adjusted within a predetermined range, and the heights of the gate 15 and the magnetic field generator 11 for detection can be easily changed according to the thickness of the inspection object 50.

  Hereinafter, functional features and functions of the metal detector 1A according to the first embodiment will be described in detail with reference to FIGS. 7 to 16 which are computer simulation images.

  FIG. 7 shows the state of the magnetic field (direction and distribution of magnetic lines of force) when the booster magnet 12 and the shield plate 111 are removed from the detection unit 5A shown in FIG. 2, and FIG. 8 shows the state of the magnetic flux density in that case. Is shown by shading (height of density = density). In this simulation, it is understood that the space magnetic field at the sensing position is stable in a uniform state due to the absence of the booster magnet.

  FIG. 9 shows the downward U-shaped shield plate so that the left and right side surfaces and the back side of the detection magnetic field generator (permanent magnet) of FIG. 7 are all covered. -The state of the magnetic field at the time of arrange | positioning so that a back surface may be approached is shown, FIG. 10 shows the state of the magnetic flux density in that case. In this simulation, although the diffusion of magnetic lines of force in the lateral direction is suppressed compared to the case of FIG. 7, the magnetic flux density in the vicinity of the sensor coil is slightly reduced, and the lines of magnetic force reaching the sensor coil are attenuated. I understand.

  11 makes the shield plate of FIG. 7 the same as the shield plate 111 of FIG. 2 and the distance between the inner side surface and the left and right side surfaces and the back surface of the magnetic field generator for detection is almost equal to the horizontal width of the magnetic field generator for detection In addition, FIG. 12 shows the state of the magnetic flux density in that case when the configuration is such that the middle position of the left and right side surfaces of the detection magnetic field forming device is covered. In this simulation, it is understood that the diffusion of magnetic lines of force in the lateral direction is suppressed, and the magnetic flux density in the vicinity of the sensor coil 10 is higher than in the case of FIG.

  FIG. 13 shows the state of the magnetic field when the booster magnet is disposed in close contact with the side surface of the sensor coil of FIG. 11, and FIG. 14 shows the state of the magnetic flux density in that case. In this simulation, the spatial magnetic field at the sensing position near the sensor coil 10 is distorted. However, it can be seen that a spot (air gap) with a thin magnetic flux density is generated at a portion indicated by an arrow in FIG. 14 and the position thereof overlaps the sensing position.

  FIG. 15 shows the state of the magnetic field when the booster magnet of FIG. 13 is separated by 15 mm from the side surface of the sensor coil, and FIG. 16 shows the state of the magnetic flux density in that case. In this simulation, the arrangement is the same as that of the sensor body 10A of FIG. 2, and it is the same as generating the appropriate distortion in the spatial magnetic field at the sensing position, but a spot with a thin magnetic flux density indicated by an arrow in FIG. Is smaller than in the case of FIG. 14, and it can be seen that the position is lowered and does not overlap the sensing position.

  As can be seen from the above results, in the sensor body 10A of FIG. 2 having the same arrangement as in the case of FIG. 15, the booster magnet 12 is used for detection by the detection magnetic field former 11 The position where the detection signal is maximized by changing the spatial magnetic field of the above by linking to the magnetic field generated by the sensor body 10A is selected, and the magnetic field is designed to improve detection sensitivity and detection accuracy.

  That is, even if two or more sensor coils are arranged or a large booster magnet is arranged in the conventional example, sufficient sensitivity to a minute metallic foreign matter can not be secured, and downsizing and cost reduction of the apparatus can not be realized. On the other hand, in the present invention, by arranging the booster magnet at the above-mentioned position, a spot where the magnetic flux density of the detection magnetic field becomes partially sparse is formed in a suitable position and state to generate the magnetic gradient of the detection magnetic field. Can temporarily magnetize the metal foreign object in the inspection object 50 while giving spatial change to it, and realize highly sensitive detection of the minute metal foreign object without increasing the size and cost of the device. It is.

  Further, in the present invention, the booster magnet 12 is disposed at an appropriate distance from the side surface of the sensor coil 10, so that the silicon steel plate of the core 10b is also prevented from becoming permanent magnetized due to aging and lowering the sensitivity. I can expect it. Further, the shield plate 111 is configured so as not to cover all the side surfaces while being separated appropriately from the magnetic field forming device 11 for detection, so that the magnetic lines of force reaching the metal sensor 10A while reducing the influence of noise generated suddenly. It makes it possible to avoid excessive attenuation.

  As described above, according to the present invention, it is possible to prevent an increase in the size and cost of the apparatus, even if it is an inspection object that is difficult to detect metal foreign matters such as aluminum packaging products and high concentration electrolyte solution-enclosed products. It became possible to detect metal foreign objects with high accuracy in response to various situations.

  DESCRIPTION OF SYMBOLS 1A, 1B metal detector, 2 control part, 3A, 3B conveyance part, 5A, 5B detection part, 10 sensor coil, 10A sensor body, 10a lead wire, 10b core, 11 detection magnetic field formation device, 12 booster magnet, 20 microcomputer , 30 conveyor belts, 31 conveyance surfaces, 50 inspection objects, 111 shield plates, 310 rollers

Claims (6)

  Variation of the magnetic field for detection by the detection magnetic field forming means, the conveyance means for conveying the object to be inspected, the metal sensor provided with the sensor coil oppositely disposed across the conveyance path by the conveyance means and the magnetic field forming means for detection And / or control means for determining the presence or absence of a metal foreign object from the signal of the sensor coil which has detected a notification that the control means detects a metal foreign object in the inspection object moving on the transport path or And in the metal detector for removing the object to be inspected, the booster magnet for magnetizing the foreign metal is used to magnetize the magnetic field by the position at a predetermined distance from the side surface of the sensor coil along the longitudinal direction of the transport path. It is disposed on the transport path side so as to partially overlap with the detection magnetic field, and the magnetization magnetic field forms spots where the magnetic flux density is partially sparse in the detection magnetic field. Wherein while the state gave spatial variation in the magnetic gradient of the detected magnetic field, metal detectors, characterized in that temporarily magnetized metallic particles of the inspection object in by causing.   The metal detector according to claim 1, wherein the booster magnet is disposed at a distance of 10 to 20 mm from a side surface of the core of the sensor coil.   The metal detector according to claim 2, wherein the booster magnet is disposed downstream of the sensor coil.   A shield for shielding of magnetic lines of force made of permalloy so as to cover a range excluding the front surface which is the opposite surface to the sensor coil of the detection magnetic field forming means and the front side middle position of the right and left sides perpendicular to the transport direction. A plate is disposed at a predetermined distance from the left and right side surfaces and the back surface of the detection magnetic field forming means so as to form a U-shaped shield surface with a vertical cross section downward. The metal detector described in 2 or 3.   The distance between the inner side surface of the shield plate and the left and right side surfaces and the back surface of the magnetic field forming means for detection is equal to the horizontal width of the magnetic field forming means for detection. The metal detector described in. The conveyance means is formed of a plurality of rollers arranged in parallel with the axis at right angles to the conveyance direction, and can be supported with a predetermined accuracy so that the downstream side of the conveyance face is low. The inspection object placed upstream of the metal sensor is automatically moved to the downstream side on the transport surface by its own weight. The metal detector described in 4 or 5.