Foreign matter detection apparatus, foreign matter detection system, and foreign matter detection method

Abstract

Disclosed is a technology of detecting foreign matter from an inspection object in which a magnetic metal, a non-magnetic metal, or a conductive material may be included as foreign matter, without being restricted by the size of the inspection object. A system (10) comprises: a conveyance unit (100) for conveying an inspection object (110); two adjacent sensors (142a, 142b) that are provided on the rear surface of the conveyance unit and that are for detecting conductive foreign matter from the inspection object; calculation circuits (153a, 153b, 153c) for calculating, on the basis of signals outputted from the two sensors, the difference between the signals; and determination circuits (154a, 154b, 154c) for determining, on the basis of the calculated difference and a threshold value (500) predetermined as a determination reference, whether or not the conductive foreign matter is present in the inspection object (110).

Description

Foreign object detection device, foreign object detection system, and foreign object detection method

[0001] The present disclosure relates to a technique for detecting foreign objects, and more particularly to a technique for detecting conductive foreign objects (typically, metals).

[0002] Regarding technology for detecting metal contaminants, for example, Japanese Patent Application Laid-Open No. 2014-92365 (Patent Document 1) discloses a metal detection device that "enhances the foreign object signal to reduce the influence of external noise, thereby enabling stable and highly sensitive detection of minute metal foreign objects in an object under inspection, and also enabling the position of the foreign object in the width direction to be identified" (see [Abstract]).

[0003] The metal detection device comprises "a magnetizing section 30 that magnetizes metallic foreign matter m in a predetermined magnetization direction in the inspection object W; a detection head 40 that has a plurality of magnetic sensor pairs, each consisting of upper magnetic sensors 41a to 41e and lower magnetic sensors 42a to 42e, which have acute directivity in the magnetization direction of the magnetizing section 30, in an orthogonal direction perpendicular to the transport direction of the inspection object W, and that detects residual magnetic components of the metallic foreign matter m; difference calculation means 80 that calculates the difference in detection signals from the upper magnetic sensors 41a to 41e and the lower magnetic sensors 42a to 42e for each magnetic sensor pair; and determination means 53 that determines the presence or absence of metal in the inspection object W and its position in the orthogonal direction based on the output signal from the difference calculation means 80" (see [Solution]).

[0004] JP 2014-92365 A

[0005] According to the technology disclosed in Patent Document 1, depending on the height or thickness of the object to be inspected, the object may come into contact with the upper magnetic sensor. If the object to be inspected comes into contact with the upper magnetic sensor, the accuracy of detecting foreign objects may decrease, and there is also a risk of damaging the object to be inspected or the magnetic sensor. To avoid such contact, it is necessary to limit the height or thickness of the object to be inspected, which restricts the size of objects that can be inspected. Therefore, there is a need for a technology that does not restrict the size of objects that can be inspected.

[0006] The present disclosure has been made in consideration of the above-described background, and aims to provide a technology for detecting conductive foreign matter from an object to be inspected without restricting the size of the object to be inspected.

[0007] According to one embodiment, there is provided a foreign object detection device comprising: an input unit that receives signals output from two adjacent sensors that detect conductive foreign objects in an object under test, a calculation circuit that calculates a difference between the input signals, and a determination circuit that determines whether or not a conductive foreign object is present in the object under test based on a predetermined threshold value as a determination criterion and the calculated difference.

[0008] According to another embodiment, there is provided a foreign object detection system comprising: a conveying means for conveying an object to be inspected; two adjacent sensors provided on the rear surface of the conveying means for detecting conductive foreign objects in the object to be inspected; a calculation circuit for calculating a difference between signals output from the two sensors based on the signals; and a determination circuit for determining whether a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

[0009] According to yet another embodiment, there is provided a foreign object detection method, which includes the steps of receiving input of signals output from two adjacent sensors for detecting conductive foreign objects in an object to be inspected, calculating a difference between the input signals, and determining whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

[0010] According to an embodiment, conductive foreign matter can be detected without being restricted by the size (height) of the object to be inspected.

[0011] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.

[0012] 1 is a diagram showing a schematic configuration of a system 10 according to an embodiment. It is a diagram showing a top view of a transport unit 100. It is a diagram showing a state in which detection signals output from two adjacent magnetic sensors 142a and 142b among a plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are input to a foreign object detection device 150. It is a conceptual diagram showing a state in which a cross section Y-Y' of the transport unit 100 is viewed in the direction of arrow 20. It is a conceptual diagram showing a series of processes in which detection signals output from a detection head 142 are processed by AD converters 152a, 152b, 152c, 152d, 152e, and 152f, difference calculation circuits 153a, 153b, and 153c, and determination circuits 154a, 154b, and 154c. It is a block diagram showing the hardware configuration of a computer 600 functioning as the foreign object detection device 150. 1 is a flowchart showing a part of a process executed by system 10 according to an embodiment. FIG. 2 is a diagram showing a state in which each of a plurality of magnetic sensors of transport unit 800 included in the system according to the embodiment is arranged offset to every other one, as viewed from above. FIG. 3 is a diagram showing a state in which each of a plurality of magnetic sensors of transport unit 900 included in the system according to the embodiment is arranged offset in a stepped manner, as viewed from above. FIG. 4 is a diagram conceptually showing a series of processes in which detection signals output from detection heads 842 and 942 are processed by AD converters 152a, 152b, 152c, 152d, 152e, and 152f, difference calculation circuits 153a, 153b, and 153c, and determination circuits 154a, 154b, and 154c.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0014] Embodiment 1. The configuration of a system 10 capable of detecting conductive foreign matter (e.g., metal) that has been mixed in as a foreign body will be described with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration of system 10 according to an embodiment. System 10 includes a conveying unit 100 and a foreign body detection device 150. Conveying unit 100 and foreign body detection device 150 are electrically connected by a signal line 151.

[0015] <Configuration of System 10> The system 10 inspects whether or not an inspection object 110 carried into the conveying unit 100 contains a conductive foreign object 111. The inspection object 110 is carried from a previous process of the system 10 (for example, a processing line, an assembly line, or a parts manufacturer) and placed on the end of the belt 121. If the inspection object 110 is manufactured normally, it does not contain any foreign object (for example, metal pieces), but foreign object may be mixed in during the previous process. Therefore, in this embodiment, a case will be described in which the inspection object 110 containing the conductive foreign object 111 is carried from the previous process to the system 10 and placed on the belt 121.

[0016] The transport unit 100 includes a conveyor 120 , a belt 121 , transport rollers 122 a , 122 b , 123 a , and 123 b , a magnetizing unit 130 , a detection head 142 , and a motor 190 .

[0017] The belt 121 transports the inspection target 110. More specifically, the motor 190 drives the transport roller 122b. When the transport roller 122b is driven, the belt 121 rotates along the transport rollers 123b, 123a, and 122a. The inspection target 110 moves on the transport surface of the belt 121 from the magnetized portion 130 toward the detection head 142. Note that the motor 190 can be a source of disturbance (noise) that invades the detection area 145 above the detection head 142.

[0018] The magnetizing unit 130 is provided upstream of the detection head 142 on the back surface of the belt 121, i.e., the surface on which the inspection object 110 is not placed. The magnetizing unit 130 is arranged so as to apply a DC magnetic field toward the conveying surface of the belt 121, i.e., the surface on which the inspection object 110 is placed. Therefore, if the inspection object 110 contains a metallic foreign object 111, a DC magnetic field is applied to the inspection object 110 when the inspection object 110 passes over the magnetizing unit 130. At this time, the foreign object 111 is magnetized by the magnetic field of the permanent magnet or electromagnet that constitutes the magnetizing unit 130.

[0019] When the test object 110 is placed on the belt 121 and the belt 121 starts to rotate in the direction of the arrow 20 , the test object 110 also moves in the direction of the arrow 20 .

[0020] The detection head 142 includes a plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f. The plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are each arranged along a direction perpendicular to the direction in which the inspection target 110 is transported by the belt 121. Therefore, the area in which each of the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f can detect a magnetic field collectively constitutes a magnetic field detection area 145. The number of magnetic sensors arranged is not particularly limited and may be more or less than the number of magnetic sensors shown in the figure. The interval between two adjacent magnetic sensors may or may not be equal.

[0021] More specifically, the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f have acute directivity in the same direction as the direction in which the magnetizing unit 130 magnetizes the inspection target 110, i.e., in a direction (vertical direction) perpendicular to the direction of the arrow 20 in which the belt 121 is conveyed. Therefore, the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f can detect only the component of the magnetic flux of the foreign substance 111 of the inspection target 110 in the acute directivity direction indicated by the up-down arrow 40. Furthermore, the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f can also detect only the component in the acute directivity direction of noise from the motor 190 arriving from downstream in the conveyance direction (arrow 20).

[0022] In one aspect, the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are configured by magnetic sensors with sharp directivity, such as coils, magnetic impedance sensors, Hall elements, magnetic resistance elements, and fluxgate sensors.

[0023] When the object under inspection 110 magnetized by the magnetizing unit 130 is present in the magnetic field detection area 145, each of the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f detects the residual magnetic component of the foreign matter 111 from the object under inspection 110.

[0024] The width of the magnetizing section 130 and the detection head 142 is configured to be at least the same as the width of the conveyor 120 or the belt 121, or wider than these widths, so that the object to be inspected 110 transported by the belt 121 can be reliably magnetized and residual magnetic components can be detected.

[0025] 2, the arrangement of the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f in the detection head 142 will be described. Fig. 2 is a view of the transport section 100 as seen from above. The multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are arranged in a row in a direction perpendicular to the transport direction indicated by arrow 20.

[0026] 1 , foreign object detection device 150 includes analog-to-digital (AD) converters 152 a, 152 b, 152 c, 152 d, 152 e, and 152 f, difference calculation circuits 153 a, 153 b, and 153 c, ​​determination circuits 154 a, 154 b, and 154 c, and display device 170. In one aspect, foreign object detection device 150 is implemented by a computer having a well-known configuration. In another aspect, foreign object detection device 150 may also be implemented as a combination of circuit elements configured to implement various processes executed internally.

[0027] The AD converters 152a and 152b receive analog signals output from two adjacent magnetic sensors 142a and 142b, convert them into digital signals, and output the digital signals to the difference calculation circuit 153a. The AD converters 152c and 152d receive analog signals output from two adjacent magnetic sensors 142c and 142d, convert them into digital signals, and output the digital signals to the difference calculation circuit 153b. The AD converters 152e and 152f receive analog signals output from two adjacent magnetic sensors 142e and 142f, convert them into digital signals, and output the digital signals to the difference calculation circuit 153c.

[0028] The difference calculation circuits 153a, 153b, and 153c each calculate the difference between two input digital signals. In the example shown, the difference calculation circuit 153a calculates the difference between a digital signal converted from an analog signal output from the magnetic sensor 142a and a digital signal converted from an analog signal output from the magnetic sensor 142b. The difference calculation circuit 153b calculates the difference between a digital signal converted from an analog signal output from the magnetic sensor 142c and a digital signal converted from an analog signal output from the magnetic sensor 142d. The difference calculation circuit 153c calculates the difference between a digital signal converted from an analog signal output from the magnetic sensor 142e and a digital signal converted from an analog signal output from the magnetic sensor 142f.

[0029] The determination circuits 154a, 154b, and 154c determine whether or not the foreign matter 111 is present in the inspection object 110 based on a comparison result between the difference and a threshold value that is predetermined as a condition for determining whether or not the foreign matter 111 is present in the inspection object 110. In one aspect, the determination circuits 154a, 154b, and 154c determine the presence or absence of the foreign matter 111 in the inspection object 110. In another aspect, the determination circuits 154a, 154b, and 154c can estimate where in the inspection object 110 the foreign matter 111 is present. For example, the determination circuits 154a, 154b, and 154c estimate the position of the foreign matter 111 in the inspection object 110 with respect to the direction 30 based on which of the difference calculation circuits 153a, 153b, and 153c outputs a difference that exceeds the threshold value. The determination circuits 154 a , 154 b , and 154 c output the determination results to the display device 170 .

[0030] The display device 170 is realized as a liquid crystal monitor, an organic EL monitor, an LED (Light Emitting Diode), or other indicators, etc. The display device 170 displays the determination result, text, graphs, information indicating the location of the foreign matter 111, a red indicator, and other information.

[0031] Next, detection of the presence or absence of foreign object 111 using two adjacent magnetic sensors will be described with reference to Fig. 3. Fig. 3 is a diagram showing a state in which detection signals output from two adjacent magnetic sensors 142a and 142b out of multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are input to foreign object detection device 150.

[0032] The detection signal output from the magnetic sensor 142a is input to an AD converter 152a via a signal line 151a, and the analog detection signal output from the magnetic sensor 142b is input to an AD converter 152b via a signal line 151b.

[0033] The AD converter 152a converts the analog detection signal into a digital signal and inputs the digital signal to the difference calculation circuit 153a. The AD converter 152b converts the analog detection signal into a digital signal and inputs the digital signal to the difference calculation circuit 153a.

[0034] The difference calculation circuit 153a calculates the difference between the digital signals to remove noise. The calculated difference signal is input to the determination circuit 154a. The determination circuit 154a compares the difference value with a predetermined threshold value as a condition for determining the presence of a foreign substance, determines whether the inspection target 110 contains a foreign substance 111, and outputs the determination result to the display device 170.

[0035] The detection of magnetism by the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f will be described with reference to Fig. 4. Fig. 4 is a conceptual diagram showing the cross section YY' of the transport section 100 as viewed in the direction of arrow 20.

[0036] When the inspection target 110 is magnetized by the magnetizing unit 130, it is magnetized as shown by magnetic field lines 400 in Fig. 4. Here, each of the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f detects only the component of the magnetic flux of the foreign object 111 of the inspection target 110 in the acute directivity direction indicated by arrow 40.

[0037] 1 again, in yet another aspect, when the determination circuits 154a, 154b, and 154c detect that a foreign object 111 is present in the inspection target object 110, they can estimate which of the two adjacent magnetic sensors that detected the foreign object 111 the foreign object 111 is located closer to. In other words, the strength of the detection signal output from the magnetic sensor that is closer to the foreign object 111 is greater than the strength of the detection signal output from the magnetic sensor that is farther from the foreign object 111. Therefore, the determination circuits 154a, 154b, and 154c can estimate the location of the foreign object 111 using the strength of each detection signal and the distance between the two magnetic sensors.

[0038] As an example, consider a case where the distance between the two magnetic sensors 142a and 142b is L (mm) and the intensity of the detection signal from the magnetic sensor 142a is a times the intensity of the detection signal from the magnetic sensor 142b. Here, the distance refers to the distance between the projection points of the magnetic sensors 142a and 142b and the foreign object 111 on the same plane. Considering the acute directivity of the magnetic sensors, the intensity of the detection signal output from the magnetic sensors is considered to be approximately inversely proportional to the distance between the magnetic sensors and the foreign object 111. Furthermore, the distance L is the sum of the distance La from the magnetic sensor 142a to the foreign object 111 and the distance Lb from the magnetic sensor 142b to the foreign object 111. Therefore, the determination circuit 154a estimates the location of the foreign object 111 as follows: La = 1 / (1 + a) × L Lb = a / (1 + a) × L Display device 170 displays the results output from determination circuits 154a, 154b, and 154c. In one aspect, display device 170 displays a screen notifying that metallic foreign matter 111 has been detected in inspection object 110. In another aspect, display device 170 displays a screen indicating where foreign matter 111 is present in inspection object 110. In yet another aspect, display device 170 displays information indicating the location of foreign matter 111, for example, information indicating the distance from the magnetic sensor.

[0039] In one aspect, the foreign object detection device 150 may further include a control device for controlling the operation of the motor 190. When the control device detects the presence of the foreign object 111 based on the output from the determination circuits 154a, 154b, and 154c, it can stop the operation of the motor 190. This stops the transport of the inspection object 110 that is suspected to contain the foreign object 111, so that the inspection object 110 can be reliably removed as a defective product.

[0040] <Determination Process> A process for determining the presence or absence of foreign matter 111 using detection signals acquired by detection head 142 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram conceptually illustrating a series of processes in which detection signals output from detection head 142 are processed by AD converters 152a, 152b, 152c, 152d, 152e, and 152f, difference calculation circuits 153a, 153b, and 153c, and determination circuits 154a, 154b, and 154c.

[0041] The detection signals output from the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f included in the detection head 142 are input to corresponding AD converters 152a, 152b, 152c, 152d, 152e, and 152f, respectively, and converted from analog signals to digital signals.

[0042] The digital signals output from the AD converters 152a and 152b are input to a difference calculation circuit 153a. The digital signals output from the AD converters 152c and 152d are input to a difference calculation circuit 153b. The digital signals output from the AD converters 152e and 152f are input to a difference calculation circuit 153c.

[0043] In one aspect, if the signals detected by magnetic sensors 142a and 142b contain noise due to motor 190 or other external devices, AD converter 152a outputs signal 510a containing noise, and AD converter 152b outputs signal 510b containing noise. If the signal detected by magnetic sensor 142c contains signal 520 indicating the detection of foreign object 111 in addition to noise due to motor 190 or other external devices, AD converter 152c outputs signal 510c containing signal 520, and AD converter 152d outputs signal 510d containing noise. If the signals detected by magnetic sensors 142e and 142f contain noise due to motor 190 or other external devices, AD converter 152e outputs signal 510e containing noise, and AD converter 152f outputs signal 510f containing noise.

[0044] The difference calculation circuit 153a calculates the difference between signals 510a and 510b. In this case, noise is canceled, and a noise-canceled signal 531 is input to the determination circuit 154a. The difference calculation circuit 153b calculates the difference between signals 510c and 510d. In this case, noise is canceled, and a noise-canceled signal 532 is input to the determination circuit 154b. The difference calculation circuit 153c calculates the difference between signals 510e and 510f. In this case, noise is canceled, and a noise-canceled signal 533 is input to the determination circuit 154c.

[0045] The determination circuit 154a compares the output value of the signal 531 with a threshold value 500, which is predetermined as a criterion for determining whether or not a foreign substance is present, to determine whether or not the inspection target 110 contains a foreign substance 111. In this case, since the output level of the signal 531 is smaller than the threshold value 500, the determination circuit 154a determines that no foreign substance is detected from this signal.

[0046] The determination circuit 154b compares the predetermined threshold value 500 with the output value of the signal 532 to determine whether or not the inspection target 110 contains a foreign substance 111. In the illustrated example, as is clear from the signal 530, a signal indicating the presence of the foreign substance 111 is shown. Therefore, the determination circuit 154b determines that the inspection target 110 contains a foreign substance.

[0047] The determination circuit 154c compares the output value of the signal 533 with the predetermined threshold value 500 to determine whether or not the inspection target 110 contains a foreign substance 111. In this case, since the output level of the signal 533 is smaller than the threshold value 500, the determination circuit 154c determines that no foreign substance is detected from this signal.

[0048] <Hardware Configuration of Foreign Object Detection Apparatus 150> Here, an example of a specific configuration of foreign object detection apparatus 150 will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the hardware configuration of a computer 600 that functions as foreign object detection apparatus 150.

[0049] The computer 600 includes, as its main components, a CPU 1 that executes a program, a mouse 2 and keyboard 3 that receive instructions input by the user of the computer 600, a RAM 4 that volatilely stores data generated by the CPU 1 executing the program or data input via the mouse 2 or keyboard 3, a hard disk 5 that nonvolatilely stores data, an optical disk drive 6, a communication interface (I / F) 7, and a monitor 8. The components are interconnected by a data bus. A CD-ROM 9 or other optical disk is loaded into the optical disk drive 6.

[0050] The processing in the computer 600 is realized by the various pieces of hardware and software executed by the CPU 1. Such software may be pre-stored on the hard disk 5. Alternatively, the software may be stored on a CD-ROM 9 or other recording medium and distributed as a computer program. Alternatively, the software may be provided as a downloadable application program by an information provider connected to the Internet. Such software is read from the recording medium by the optical disk drive 6 or other reading device, or downloaded via the communication interface 7, and then temporarily stored on the hard disk 5. The software is read from the hard disk 5 by the CPU 1 and stored in the RAM 4 in the form of an executable program. The CPU 1 executes the program.

[0051] Each component constituting the computer 600 shown in Figure 6 is a general component. Therefore, one essential part of the technical idea of ​​the present disclosure can be said to be software stored in the RAM 4, hard disk 5, CD-ROM 9, or other recording medium, or software that can be downloaded via a network. The recording medium may include a non-transitory computer-readable data recording medium. Note that the operation of each piece of hardware in the computer 600 is well known, so detailed description will not be repeated.

[0052] The recording medium is not limited to a CD-ROM, a FD (Flexible Disk), or a hard disk, but may also be a medium that carries a program in a fixed manner, such as a magnetic tape, a cassette tape, an optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), an IC (Integrated Circuit) card (including a memory card), an optical card, a mask ROM, an EPROM (Electronically Programmable Read-Only Memory), an EEPROM (Electronically Erasable Programmable Read-Only Memory), a semiconductor memory such as a flash ROM, or the like.

[0053] The program referred to here includes not only a program that can be directly executed by a CPU, but also a source program, a compressed program, an encrypted program, and the like.

[0054] <Control Structure> The control structure of system 10 will be described with reference to Fig. 7. Fig. 7 is a flowchart showing a part of the process executed by system 10 according to an embodiment.

[0055] In step S710, the system 10 receives the inspection target 110 carried from the previous process onto the front surface of the belt 121. The inspection target 110 may be carried by a robot or other automated device, or by a worker.

[0056] In step S720, the magnetized portion 130 on the back surface of the belt 121 magnetizes the inspection object 110.

[0057] In step S730, each of the magnetic sensors detects a residual magnetic component from the inspection target 110 and outputs the detection result. The detection result is input to the foreign object detection device 150. Each analog detection signal is converted into a digital signal by an AD converter 152a, 152b, 152c, 152d, 152e, and 152f.

[0058] In step S740, the difference calculation circuits 153a, 153b, and 153c each use the detection results to calculate the difference between the outputs from two adjacent magnetic sensors.

[0059] In step S750, the determination circuit compares the difference with a predetermined threshold value, determines whether or not metallic foreign matter 111 is present, and outputs the determination result.

[0060] In step S760, the display device 170 outputs the determination result. The operator of the system 10 can use the determination result shown on the display device 170 to determine whether the inspection target 110 contains metallic foreign matter 111.

[0061] As described above, the system 10 according to this embodiment magnetizes the object 110 from the rear surface of the belt 121 that transports the object 110, and can detect the residual magnetic component from the rear surface. There are no particular restrictions on the width and height of the conveyor 120 having the belt 121. This prevents contact between the object 110 and the magnetized unit 130, or between the object 110 and the detection head 142. Furthermore, restrictions on the size of the object 110 are also alleviated compared to when there are restrictions on the top and bottom.

[0062] Furthermore, the difference calculation circuits 153a, 153b, and 153c calculate the difference between the detection signals from two adjacent magnetic sensors among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f, thereby canceling out noise caused by, for example, the operation of the motor 190. This makes it possible to stably and accurately determine the presence or absence of metallic foreign matter 111 without erroneous determination due to noise.

[0063] Furthermore, the system 10 has a plurality of magnetic sensor pairs, each consisting of two adjacent magnetic sensors from among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f, in an orthogonal direction perpendicular to the transport direction of the inspection object 110, so that the judgment circuits 154a, 154b, and 154c can determine the presence or absence of metallic foreign matter 111 on the inspection object 110 for each magnetic sensor pair and can identify the position of the metallic foreign matter 111 in the orthogonal direction.

[0064] Second Embodiment Next, a second embodiment will be described. The system according to this embodiment differs from system 10 according to the first embodiment in that it includes a conveying unit 800 ( FIG. 8 ) or a conveying unit 900 ( FIG. 9 ) that uses a detection head 842 ( FIG. 8 ) or a detection head 942 ( FIG. 9 ) that has an offset-positioned magnetic sensor. That is, system 80 according to this embodiment includes a conveying unit 800 and a foreign object detection device 150 ( FIG. 1 ), and system 90 includes a conveying unit 800 and a foreign object detection device 150 ( FIG. 1 ). Of the elements that make up systems 80 and 90, elements that have the same configuration as the elements that make up system 10 will not be described again.

[0065] 8 and 9, the configuration of transport units 800 and 900 using detection heads 842 and 942 according to the present embodiment will be described. Fig. 8 is a top view showing a state in which each of the multiple magnetic sensors of transport unit 800 according to the present embodiment is arranged with an offset from every other magnetic sensor. In detection head 842, two adjacent magnetic sensors among the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are arranged with an offset of a distance ΔL.

[0066] 9 is a top view of a state in which a plurality of magnetic sensors of a transport unit 900 according to this embodiment are arranged in a stepped offset manner. In a detection head 942, two adjacent magnetic sensors among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are arranged with an offset of a distance ΔL.

[0067] According to this embodiment, two adjacent magnetic sensors among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f are arranged offset from each other in a direction perpendicular to the conveyance direction (arrow 20) of the inspection target 110. As a result, when the difference between the outputs from the two magnetic sensors is calculated, noise is removed but the detection signal is not removed, and therefore can be used for judgment.

[0068] 10, a process for determining the presence or absence of foreign matter 111 using the detection signal acquired by detection head 842 or 942 according to this embodiment will be described. Fig. 10 is a diagram conceptually showing a series of processes in which the detection signal output from detection head 842 or 942 is processed by AD converters 152a, 152b, 152c, 152d, 152e, and 152f, difference calculation circuits 153a, 153b, and 153c, and determination circuits 154a, 154b, and 154c.

[0069] Each detection signal output from the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f included in the detection head 842 or 942 is input to the corresponding AD converters 152a, 152b, 152c, 152d, 152e, and 152f, respectively, and converted from an analog signal to a digital signal.

[0070] The digital signals output from the AD converters 152a and 152b are input to a difference calculation circuit 153a. The digital signals output from the AD converters 152c and 152d are input to a difference calculation circuit 153b. The digital signals output from the AD converters 152e and 152f are input to a difference calculation circuit 153c.

[0071] In one aspect, when the signals detected by the magnetic sensors 142a and 142b contain noise due to the motor 190 or other external devices, the AD converter 152a outputs a signal 1010a containing noise, and the AD converter 152b outputs a signal 1010b containing noise. When the signals detected by the magnetic sensors 142c and 142d contain signals 1020 and 1021 indicating the detection of the foreign object 111 in addition to noise due to the motor 190 or other external devices, the AD converter 152c outputs a signal 1010c containing signal 1020, and the AD converter 152d outputs a signal 1010d containing signal 1021. When the signals detected by the magnetic sensors 142e and 142f contain noise due to the motor 190 or other external devices, the AD converter 152e outputs a signal 1010e containing noise, and the AD converter 152f outputs a signal 1010f containing noise.

[0072] The difference calculation circuit 153a calculates the difference between the signals 1010a and 1010b. In this case, noise is canceled, and the noise-canceled signal 1031 is input to the determination circuit 154a. The difference calculation circuit 153b calculates the difference between the signals 1010c and 1010d. In this case, noise is canceled, and the noise-canceled signal 1032 is input to the determination circuit 154b. The difference calculation circuit 153c calculates the difference between the signals 1010e and 1010f. In this case, noise is canceled, and the noise-canceled signal 1033 is input to the determination circuit 154c.

[0073] The determination circuit 154a compares the output value of the signal 1031 with a threshold value 500, which is predetermined as a criterion for determining whether or not a foreign substance is present, to determine whether or not the inspection target 110 contains a foreign substance 111. In this case, since the output level of the signal 1031 is smaller than the threshold value 500, the determination circuit 154a determines that no foreign substance is detected from this signal.

[0074] The determination circuit 154b compares the output value of the signal 1032 with the predetermined threshold value 500 to determine whether the inspection target 110 contains a foreign substance 111. The illustrated example shows a signal indicating the presence of the foreign substance 111, as is clear from the signals 1020 and 1021. In this case, when the difference between the signals 1010c and 1010d is calculated to remove noise, the signal 1032 will have a convex portion 1051 and a concave portion 1052. Therefore, when the determination circuit 154b detects that a negative value corresponding to the concave portion 1052 has been calculated, it derives the absolute value of the negative value and compares the absolute value with the threshold value 500 to detect the presence or absence of the foreign substance 111. Therefore, when the absolute values ​​of the output values ​​of the convex portion 1051 and the concave portion 1052 are at the same level, the determination circuit 154b can detect the presence of the foreign substance 111 even using the output value of the concave portion 1052.

[0075] The determination circuit 154c compares the output value of the signal 1033 with the predetermined threshold value 500 to determine whether or not the inspection target 110 contains a foreign substance 111. In this case, since the output level of the signal 1033 is smaller than the threshold value 500, the determination circuit 154c determines that no foreign substance is detected from this signal.

[0076] As described above, in a system equipped with the conveying unit 800 (FIG. 8) or the conveying unit 900 (FIG. 9) according to this embodiment, the detection head 842 or 942 can output a signal to the foreign object detection device 150 to detect the presence or absence of metallic foreign objects 111 from the magnetized inspection object 110 without coming into contact with the inspection object 110.

[0077] Furthermore, the difference calculation circuits 153a, 153b, and 153c cancel out noise disturbances by calculating the difference between detection signals from two adjacent magnetic sensors among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f. This prevents the determination circuits 154a, 154b, and 154c from erroneously determining the presence or absence of the foreign object 111 due to the noise, thereby enabling the presence or absence of the metallic foreign object 111 to be detected with higher accuracy.

[0078] Furthermore, the transport units 100, 800, and 900 of the system have a plurality of magnetic sensor pairs, each consisting of two adjacent magnetic sensors from among the plurality of magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f, in a direction perpendicular to the transport direction of the inspection object 110. This allows the determination circuits 154a, 154b, and 154c to determine the presence or absence of metallic foreign matter 111 that may be contained in the inspection object 110 for each magnetic sensor pair, and also to identify the position of the foreign matter 111 in the perpendicular direction, so that this position information can be information for identifying the cause of the contamination of the foreign matter 111.

[0079] Furthermore, one of two adjacent magnetic sensors among the multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f is positioned offset in the conveying direction. Even if metal foreign object 111 is located midway between the two magnetic sensors in the width direction of belt 121 serving as conveying means, the detection signal of metal foreign object 111 does not completely cancel out due to the difference in detection signals from the two magnetic sensors, and some remains, canceling out only the noise. This allows a system including conveying unit 800 or conveying unit 900 to detect metal foreign object 111 located midway with high accuracy.

[0080] In another aspect, a configuration without magnetizing unit 130 and multiple magnetic sensors 142a, 142b, 142c, 142d, 142e, and 142f may be employed. In this case, the system according to this aspect includes a metal detection sensor incorporating an AC magnetic field source and a magnetic sensor, instead of magnetizing unit 130 and each magnetic sensor. The AC magnetic field source is, for example, a transmission coil to which an AC current is applied. Such a metal detection sensor can detect not only magnetic metals such as iron, but also non-magnetic metals such as aluminum and conductive materials such as carbon fiber reinforced plastics (CFRP).

[0081] Some of the technical features disclosed above can be summarized as follows: [Configuration Example 1] A foreign object detection device according to an embodiment includes an input unit that receives input of signals output from two adjacent sensors that detect conductive foreign objects in an object to be inspected, a calculation circuit that calculates the difference between the input signals, and a determination circuit that determines whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

[0082] [Configuration Example 2] In a foreign object detection device according to a certain aspect, in addition to configuration example 1, the two adjacent sensors are arranged so that they are adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected, and the determination circuit further estimates the location of the foreign object in the perpendicular direction of the object to be inspected based on the intensity of each of the signals.

[0083] [Configuration Example 3] In a foreign object detection device according to a certain aspect, in addition to configuration example 2, the determination circuit further estimates the location of the foreign object in the orthogonal direction of the object being inspected based on the signals output from the two adjacent sensors.

[0084] [Configuration Example 4] In a foreign object detection device according to a certain aspect, in addition to any of the configuration examples described above, the two adjacent sensors are arranged offset from each other in the conveyance direction of the inspection object.

[0085] Configuration Example 5 In addition to any of the configuration examples described above, a foreign object detection device according to a certain aspect has the following configuration: the inspection object is magnetized during transportation, and the two adjacent sensors include magnetic sensors.

[0086] [Configuration Example 6] According to another embodiment, a foreign object detection system is provided, which includes a conveying means for conveying an object to be inspected, two adjacent sensors provided on the rear surface of the conveying means for detecting conductive foreign objects in the object to be inspected, a calculation circuit for calculating a difference between signals output from the two sensors based on the signals, and a determination circuit for determining whether a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

[0087] [Configuration Example 7] In a foreign object detection system according to a certain aspect, in addition to configuration example 6, the two adjacent sensors are arranged adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected, and the judgment circuit further estimates the location of the foreign object in the perpendicular direction of the object to be inspected based on the intensity of each signal.

[0088] [Configuration Example 8] In a foreign object detection system according to a certain aspect, in addition to configuration example 7, the judgment circuit further estimates the location of the foreign object in the orthogonal direction of the object to be inspected based on each signal output from the two adjacent sensors.

[0089] [Configuration Example 9] In a foreign object detection system according to a certain aspect, in addition to any of the configuration examples described above, the two adjacent sensors are arranged offset from each other in the conveyance direction of the inspection object.

[0090] [Configuration Example 10] In addition to any of the configuration examples described above, a foreign object detection system according to a certain aspect further includes the following: the inspection object is magnetized during transportation; and the two adjacent sensors include magnetic sensors.

[0091] [Configuration Example 11] According to yet another embodiment, there is provided a foreign object detection method, which includes the steps of receiving input of signals output from two adjacent sensors for detecting conductive foreign objects in an object to be inspected, calculating a difference between the input signals, and determining whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

[0092] [Configuration Example 12] In addition to the foreign object detection method described in Configuration Example 11, a foreign object detection method according to a certain aspect further includes the following: the two adjacent sensors are arranged adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected; and the determining step further includes the step of estimating the location of the foreign object in the perpendicular direction of the object to be inspected based on the intensity of each of the signals.

[0093] [Configuration Example 13] In a foreign object detection method according to a certain aspect, in addition to the foreign object detection method described in Configuration Example 12, the determining step further includes a step of estimating the location of the foreign object in the orthogonal direction of the object to be inspected based on the signals output from the two adjacent sensors, respectively.

[0094] Configuration Example 14 In a foreign object detection method according to a certain aspect, in addition to any of the configuration examples described above, the two adjacent sensors are arranged offset from each other in the conveyance direction of the inspection object.

[0095] Configuration Example 15 In a foreign object detection method according to a certain aspect, in addition to any of the configuration examples described above, the inspection object is magnetized during transportation, and the two adjacent sensors include magnetic sensors.

[0096] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0097] The disclosed technical features are applicable to devices for detecting foreign matter from an object to be inspected, which may contain magnetic metals, non-magnetic metals, or conductive materials as foreign matter.

[0098] 1 CPU, 2 Mouse, 3 Keyboard, 4 RAM, 5 Hard disk, 6 Optical disk drive, 7 Communication interface, 8 Monitor, 9 CD-ROM, 10, 80, 90 System, 20, 30, 40 Arrow, 130 Magnetized part, 142, 842, 942 Detection head, 100, 800, 900 Transport part, 110 Inspection object, 111 Foreign matter, 120 Conveyor, 121 Belt, 122a, 122b, 123a, 123b Transport roller, 142a, 142b, 142c, 142d, 142e, 142f Magnetic sensor, 145 Magnetic field detection area, 150 Foreign matter detection device, 151, 151a, 151b Signal lines, 152a, 152b, 152c, 152d, 152e, 152f AD converters, 153a, 153b, 153c Difference calculation circuits, 154a, 154b, 154c Determination circuits, 170 Display device, 190 Motor, 400 Magnetic field lines, 500 Threshold values, 510a, 510b, 510c, 510d, 510e, 510f, 520, 530, 531, 532, 533, 1010a, 1010b, 1010c, 1010d, 1010e, 1010f, 1020, 1021, 1031, 1032, 1033 Signal, 600 Computer, steps S710, S720, S730, S740, S750, S760, 1051 convex portion, 1052 concave portion.

Claims

1. A foreign object detection device comprising: an input section that receives input of each signal output from two adjacent sensors for detecting conductive foreign objects in an object to be inspected; a calculation circuit that calculates the difference between the input signals; and a judgment circuit that judges whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a judgment criterion and the calculated difference.

2. The foreign object detection device according to claim 1, wherein the two adjacent sensors are arranged adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected, and the judgment circuit further estimates the location of the foreign object in the perpendicular direction of the object to be inspected based on the intensities of the output signals of the plurality of calculation circuits.

3. The foreign object detection device according to claim 2, wherein the determination circuit further estimates the location of the foreign object in the orthogonal direction of the object to be inspected based on the signals output from the two adjacent sensors.

4. A foreign matter detection device according to any one of claims 1 to 3, wherein the two adjacent sensors are arranged offset from each other in the transport direction of the object to be inspected.

5. A foreign object detection device according to any one of claims 1 to 4, wherein the inspection object is magnetized during transportation, and the two adjacent sensors include magnetic sensors.

6. A foreign object detection system comprising: a transport means for transporting an object to be inspected; two adjacent sensors provided on the rear surface of the transport means for detecting conductive foreign objects in the object to be inspected; a calculation circuit for calculating the difference between the signals output from the two sensors based on the signals; and a judgment circuit for judging whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a judgment criterion and the calculated difference.

7. A foreign object detection system as described in claim 6, wherein the two adjacent sensors are arranged adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected, and the judgment circuit further estimates the location of the foreign object in the perpendicular direction of the object to be inspected based on output signals from a plurality of the calculation circuits.

8. A foreign object detection system according to claim 7, wherein the determination circuit further estimates the location of the foreign object in the orthogonal direction of the inspection object based on the signals output from the two adjacent sensors.

9. A foreign object detection system according to any one of claims 6 to 8, wherein the two adjacent sensors are arranged offset from each other in the transport direction of the object to be inspected.

10. A foreign object detection system according to any one of claims 6 to 9, wherein the inspection object is magnetized during transportation, and the two adjacent sensors include magnetic sensors.

11. A foreign object detection method comprising the steps of: receiving input of signals output from two adjacent sensors for detecting conductive foreign objects in an object to be inspected; calculating the difference between the input signals; and determining whether or not a conductive foreign object is present in the object to be inspected based on a predetermined threshold value as a determination criterion and the calculated difference.

12. A foreign object detection method as described in claim 11, wherein the two adjacent sensors are arranged adjacent to each other in a direction perpendicular to the transport direction of the object to be inspected, and the determining step further includes a step of estimating the location of the foreign object in the perpendicular direction of the object to be inspected based on the intensity of each of the signals.

13. A foreign object detection method as described in claim 12, wherein the determining step further includes a step of estimating the location of the foreign object in the orthogonal direction of the object to be inspected based on the signals output from the two adjacent sensors.

14. A foreign matter detection method according to any one of claims 11 to 13, wherein the two adjacent sensors are arranged offset from each other in the transport direction of the inspection object.

15. A foreign matter detection method according to any one of claims 11 to 14, wherein the inspection object is magnetized during transportation, and the two adjacent sensors include magnetic sensors.