JP3791662B2 - Metal detection method and metal detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is in the subject garment such as clothing or, you detect bread, sewing needles mixed into the subject food products such as meat, nail, needle-shaped metal foreign object such as a needle (hereinafter referred to as analyte) those concerning the suitably applied metal detection method and a metal detector in the needle detector for.
[0002]
[Prior art]
As a conventional needle-shaped metallic foreign object detection device for sewing products or foods, there are a conveying means such as a belt conveyor, a single search coil as a detection sensor, and a control unit that amplifies and detects a received signal obtained by the coil. There is a conveyor type needle detector that combines
[0003]
In these conventional needle detectors, when an object mounted on a conveyor such as a belt conveyor passes through a tunnel path type search coil, the induced electromotive force of the search coil due to the AC excitation magnetic field varies depending on the mixed object. There are AC magnetic field type that captures this, or DC magnetic field type that the search coil captures the change caused by the mixed needles of the DC excitation magnetic field as an induced electromotive force, both of which are based on the principle of electromagnetic induction that amplifies and detects the induced electromotive force. is there.
[0004]
The present invention is that you try to solve]
The detection of a test object using a conventional needle detector for sewing or food is extremely extreme, with the specific dimension of the longitudinal direction being several tens of times larger than the diameter of a microscopic cross-section compared to a test object having a general shape. Because of the different needle- shaped specimens, the so-called specimen detection that the change in the linkage flux to the receiving coil varies depending on the attitude of the needle-shaped metal foreign object when passing through the search coil and the detection sensitivity differs greatly. There was a problem of directionality.
[0005]
Changes in the interlinkage magnetic flux of the receiving coil due to the posture of the test object when passing through the search coil of the transmission / reception counter-arranged search coil, whether the excitation magnetic field is an AC magnetic field or a DC magnetic field, and the test object is a ferromagnetic material It varies greatly depending on whether it is a metal or a non-magnetic metal. This is due to the difference between the detection principles of the two. Hereinafter, description will be given mainly using an AC excitation magnetic field.
[0006]
FIG. 8 is a side view for explaining the overall configuration of the needle detector according to the prior art. The outer shape of the needle detector has a substantially rectangular parallelepiped shape, and a rectangular tunnel passage 4 is formed in the center of the needle detector. The belt conveyor of the transfer machine 3 on which the subject 41 is placed passes through the tunnel passage 4. As shown, a transmission / reception opposed arrangement type search coil 20 (same for transmission / reception coaxial arrangement type search coil 30) is provided upright. Then, the signal detected by the search coil 20 (30) in the subject 41 is sent to the control panel 50, where it is subjected to amplification calculation processing.
[0007]
FIGS. 3 and 4 are an explanatory perspective view and a cross-sectional view in the A direction of FIG. The transmitting coil 21 and the receiving coil 22 are opposed to each other across the tunnel path 4, and the pair of receiving coils 22 a and 22 b facing the transmitting coil 21 are excited magnetic fluxes 23 orthogonal to the transport direction P in the tunnel path 4. Change due to the test object is regarded as a change in the interlinkage magnetic flux in both the reception coils 22a and 22b, and the change in the induced electromotive force is detected by the differential connection circuit (not shown) as a differential output signal of the reception coils 22a and 22b. Is output to the control panel 50.
[0008]
5 and 6 are a perspective view for explaining the arrangement of the transmitting coil 31 and the receiving coil 32 of the transmission / reception coaxial arrangement type search coil 30 in which the transmission / reception coils are coaxially arranged, and a sectional view in the B direction of FIG. Three loop-shaped coils are concentrically arranged so as to surround the tunnel passage 4, a transmitting coil 31 is disposed at the center portion, and a pair of receiving coils 32 a and 32 b are disposed at the front and rear portions sandwiching this. ing. The functions of the pair of receiving coils 32a and 32b are the same as those of the receiving coils 22a and 22b described above, and a change in the transmission / reception coaxial arrangement type detection signal is output to the control panel 50 as a differential output signal by the differential connection circuit.
[0009]
FIG. 9 shows the case where the ferromagnetic metal test object 40 in the cross section A of the transmission / reception counter-arranged search coil 20 is in a posture that coincides with the direction of the excitation magnetic flux 23, and the magnetic flux is concentrated and linked to the nearest receiving coil 22b. It is explanatory drawing which shows the flow of the magnetic flux which showed the state which is carrying out.
[0010]
When the test object 40 is a ferromagnetic metal, the magnetic resistance is minimum when passing through the test object 40 when its posture matches the direction of the excitation magnetic flux 23, so that a magnetic flux is generated around the test object 40. As a result, the interlinkage magnetic flux of the nearest receiving coil 22b becomes extremely large at a certain time. That is, the highest sensitivity is obtained when the posture of the test object 40 in the search coil 20 matches the direction of the excitation magnetic flux 23.
[0011]
Similarly, FIG. 10 shows the flow of magnetic flux in the case where the posture of the non-magnetic metal needle-like test object 40 in the cross section A of the search coil 20 coincides with the transport direction P and is perpendicular to the direction of the excitation magnetic flux 23. It is explanatory drawing. In this case, unlike the ferromagnetic metal test object 40, an eddy current flows near the surface of the test object 40 when the excitation magnetic flux 23 is linked to the test object 40, and the back electromotive force magnetic flux is generated by the current. Therefore, the larger the interlinkage surface area, the more the interlinkage magnetic flux decreases and the magnetic flux changes so as to avoid the test object 40. As a result, the flux linkage of the nearest receiving coil 22b becomes extremely sparse at a certain point in time, and the change in induced electromotive force also increases.
[0012]
That is, when the test object 40 is a non-magnetic metal, the phenomenon is opposite to the magnetic flux distribution of FIG. 9, and the change in induced electromotive force is large in this posture, and the highest detection sensitivity is exhibited.
[0013]
In the transmission / reception opposed arrangement type search coil 20 , when the test object is a ferromagnetic metal, the magnetic flux is converged on the test object having a smaller magnetic resistance so that the change in the interlinkage magnetic flux of the reception coil is captured. , the attitude of the transmitting and receiving opposed type search coil 20 specimen during passing, Ri most small magnetic resistance in the case was in the direction the same direction of the magnetic flux of the exciting coil, a change in flux linkage of the receiver coil the largest detection sensitivity is also high. On the contrary, when the posture of the test object is orthogonal to the direction of the magnetic flux, the detection sensitivity is significantly reduced.
[0014]
If the test object is a non-magnetic metal, rather work as counter electromotive force flux due to eddy current generated in the test object cancels the original flux. Since the receiving coil is configured to detect the change in the linkage flux generated in this way , the position of the test object having the largest linkage flux due to the flux from the excitation coil is determined so that the search coil 20 is arranged opposite to the receiving coil. The change in flux linkage during passage is the largest and the sensitivity is high. However, on the contrary, there is an extreme difference in sensitivity depending on the posture of the test object such that when the posture of the minimum flux linkage, that is, the test object and the excitation magnetic field are in the same direction , the sensitivity is significantly reduced .
[0015]
In the case of the transmission / reception coaxial search coil 30 as well, the posture and detection sensitivity of the test object with respect to the direction of the excitation magnetic flux are the same depending on whether the test object is a ferromagnetic metal body or a nonmagnetic metal body . That is, the operating principle relating to the posture of the direction and the test of the excitation magnetic flux does not change essentially in the case of transmitting and receiving opposed type search coil 20, or a test body 41 which passes through the transmitting and receiving coaxial arrangement type search coil 30 If there lamination, since the direction of the excitation magnetic flux is 90 ° difference from each other, ing substantially inverse relationship with respect to the detection sensitivity. There is little difference in the detection sensitivity depending on the posture of the object as described above, more speaking straightforward, if only detects the acicular metal foreign object in a single search coil 20 (30), detects a foreign matter Can or can not .
[0016]
The result of the concrete demonstration test of the needle detector according to the above-described conventional example is shown below.
In the case of the transmission / reception facing arrangement type search coil 20 having the rectangular tunnel passage 4 having a vertically long cross section shown in FIG. 3, the transmission / reception facing which detects the needle-like metal foreign matter arranged in parallel in the X, Y and Z directions described below. The detection voltage of the arrangement type search coil 20 is as follows. Note that the X direction represents the conveyance direction P, the Y direction represents a horizontal direction perpendicular to the conveyance direction P, and the Z direction represents a direction parallel to the vertical direction perpendicular to the conveyance direction P. As the needle-shaped metal foreign matter, an iron applique needle was used for the ferromagnetic material, and a stainless steel equivalent needle was used for the non-magnetic material.
Transmitting / receiving opposed type search coil Detection voltage V
Specimen material / posture Ferromagnetic metal Nonmagnetic metal
Y 12.3 1.3
X 6.8 4.1
Z 1.38
[0017]
As can be seen from the above test results, the detection voltage is extremely small for acicular metal foreign bodies parallel to the Z direction in ferromagnetic metals and in the Y direction in non-magnetic metals. Therefore, these measured values are actually disturbances such as noise. Because of the factors, it cannot be judged as a practically significant measured value. That is, it is impossible to detect the needle-shaped metallic foreign matter arranged in the above direction. As described above, when a needle-like metal foreign object is detected by the conventional search coil 20 (30), there is a case where it cannot be detected due to the posture of the needle-like metal foreign object. The reason why the detection voltage in the X direction shows an intermediate value between the detection voltages in the Y and Z directions is that the shape of the transmission coil 21 is a vertically long rectangular shape, so that the bottom of the excitation magnetic flux 23 opens. It can be inferred that this has occurred.
[0018]
Next, the detection voltage of the transmission / reception coaxially arranged search coil 30 when detecting the needle-shaped metallic foreign object with the transmission / reception coaxially arranged search coil 30 having the rectangular tunnel passage 4 having a vertically long cross section is as follows. The sample needle is the same as above.
Transmission / reception coaxial arrangement type search coil Detection voltage V
Specimen material / posture Ferromagnetic metal Nonmagnetic metal
Y 1.2 10
X 6.8 4.1
Z 1.38
[0019]
As described above, in the case of the transmission / reception coaxial arrangement type search coil 30, it is impossible to detect the needle-like metal foreign object of the ferromagnetic metal arranged in the Y direction and the Z direction.
The present invention has been made to solve such a problem in the prior art, and can detect almost all needle-like metal foreign objects regardless of the direction of the needle-like metal foreign substances mixed in the subject. The object is to provide a method and a metal detector.
[0020]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a transmission / reception opposed-arranged search coil and a transmission / reception coaxial that are arranged with inclination angles opposite to each other along a conveyance path along which a subject is conveyed. The metallic foreign matter mixed in the subject is detected based on the reception signal output from each search coil when passing through the arrangement type search coil.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.
[0022]
FIGS. 1 and 2 are a side view and a front view, respectively, showing a search coil in cross-section for explaining the entire needle detector according to one embodiment of the present invention . The drive pulley 5 is rotatably attached to the front and rear bearing bases 6 fixed to the frame 7 of the airframe via bearings 8. Since it is a known configuration including a drive system such as a prime mover , illustration and description thereof are omitted. In this embodiment, the transmission / reception opposed arrangement type search coil 20 or the transmission / reception coaxial arrangement type search coil 30 is opposed to the conveyance surface at an inclination angle α opposite to the conveyance direction P of the subject on the conveyance device 3. It is arranged in the shape of a Katakana letter C.
The value of the inclination angle α is preferably 45 ° from the viewpoint of sensitivity. However, as the inclination angle decreases , the longitudinal dimension of the search coil 20 (30) increases due to the relationship between the tunnel passage 4 and the transporter 3 . Considering the economical aspect, it is set to 60 °. In addition, although the belt conveyor is used as a conveyance means of the conveying machine 3, you may use another drive means.
[0023]
In addition, each search coil 20 (30) pair includes a tunnel passage 4 entrance / exit surface of each search coil 20 (30) having a Katakana letter C (or reverse letter C ) in the conveyance direction P of the conveyor 3. In this way, the entrance / exit surface and the transport passage surface are configured to face each other while maintaining a specified angle, and are arranged to face each other in the transport direction P of the subject 41 at regular intervals.
[0024]
According to the combination of the search coils 20 (30) having such an arrangement, the conveying surface and the search coil 20 (30) are inclined at a constant angle and in a katakana letter C or an inverted letter C. Therefore, depending on the posture of the needle-like test object 41 in the subject 40 on the transport surface when passing through the search coil 20 (30), one search coil 20 (30) has a change in the flux linkage 24, that is, sensitivity. Even at the minimum, since the relative relationship between the excitation magnetic flux 23 and the posture of the other search coil 20 (30) that subsequently passes is greatly different, the sensitivity is not minimum.
[0025]
This is because, depending on the detection posture in the search coil 20 (30), the dimensions of the needles are extremely small when viewed in terms of the diameter of the cross section. Then, inconvenience due to the inability to detect frequently occurs.
[0026]
In addition, each search coil 20 (30) pair is configured such that the entrance / exit surface of the tunnel passage 4 of each search coil 20 (30) is in the shape of Katakana C or reverse C in the transport direction P of the transporter 3. In addition, the entrance / exit surface and the transport passage surface are configured to face each other while maintaining a specified angle, and are arranged so as to maintain a predetermined interval in the front-rear direction in the transport direction of the subject 41.
[0027]
According to the combination of the search coils 20 (30) having such an arrangement, the search coil 20 and the search coil 20 (30) are inclined at a predetermined angle and in a Katakana letter C. (30) The needle-like test object 40 in the subject 41 on the transport surface when passing through the one search coil 20 (30) has a minimum change in linkage flux, that is, even if the detection voltage of the search coil 20 (30) is minimum. Since the relative angle between the excitation magnetic flux 23 in the other search coil 20 (30) that subsequently passes and the posture of the test object 40 increases, the detection voltage does not become minute.
[0028]
The results of the verification test of the needle detector 10 according to this example are as follows.
1. Transmit / receive opposed arrangement type search coil Detection voltage V: Ferromagnetic metal (non-magnetic metal)
Search coil tilt angle / posture + 60 ° -60 °
Y 12.3 ( 1.3 ) 12.3 ( 1.3 )
X 6.1 (6.2) 6.1 (6.2)
Z 4.1 (7.5) 4.1 (7.5)
Z + 30 ° 1.3 (8) 6.1 (6.2)
2. Transmission / reception coaxial arrangement type search coil Detection voltage V: Ferromagnetic metal (non-magnetic metal)
Search coil tilt angle / posture + 60 ° -60 °
Y 12.3 ( 1.3 ) 1.2 (10)
X 6.1 (6.2) 13.5 (3.6)
Z 4.1 (7.5) 8.5 (5.3)
Z + 30 ° 1.3 (8.3) 13.5 (3.6)
[0029]
According to this, all of the detection voltages indicated by the underline are non-detectable fine voltages , and in the case of the transmission / reception opposed arrangement type search coil 20 , the orientation Z + 30 ° is a + 60 ° search coil and the magnetic metal is as low as 1.3 V. Although it is a value, it is reversed to 6.1 V by a -60 ° search coil . On the other hand , when detecting the test object 40 made of a non-magnetic metal, it is difficult to detect the test object 40 because the voltage is 1.3 V, even if it is detected by both the pair of transmission / reception counter-arranged search coils 20 .
[0030]
Next, in the case of the transmission / reception coaxial arrangement type search coil 30 , even if the value of the attitude of the low voltage with an underline is shown, one of the values of the other pair of search coils 30 indicates a detection voltage close to the maximum value. I understand that. This proves that the katakana letter C combination of the transmission / reception coaxial arrangement type search coil 30 has the least detection blind spot, and as another combination, the transmission / reception counter arrangement type search coil 20 has an inclination angle +60. Even when the transmission / reception coaxial arrangement type search coil 30 is combined with the arrangement at an inclination angle of −60 ° , there is no posture of the test object 40 that can not be detected.
[0031]
In the above demonstration test , in order to simplify the explanation, the results when the posture of the needle-shaped specimen 40 is only in the X, Y, Z, Z + 30 ° directions are shown. The posture is generally in an arbitrary direction . However, even if the needle-shaped test object 40 faces in an arbitrary direction, the direction of the needle-shaped test object 40 can be indicated by the vector sum of the needle-shaped test object 40 indicating the X, Y, and Z directions, respectively. Therefore, the above description can be applied to the needle-like test object 40 oriented in an arbitrary direction .
[0032]
FIG. 7 shows a side view according to a modification of the embodiment of the present invention , and the entire needle detector 10 ′ in which the search coil 20 (30) is formed in a reverse letter C shape of Katakana on the transport device 3. It is a side view for demonstrating .
[0033]
FIG. 11 shows a state in which the posture of the needle-like test object 40 in the search coil 20 (30) is in a special form in a state in which a pair of search coils 20 (30) are arranged in the shape of a Katakana letter C. examples Ru Oh in the description diagram illustrating a.
[0033]
Figure 12 is a sectional view taken along the conveying direction when the above-described transmission and reception opposed type search coil 20, the position of the needle test object 40 are those corresponding to FIG. 11.
[0034]
In FIG. 13, the transmission / reception coils 21 and 22 (31 and 32) disposed in the case 60 of the search coil 20 (30) are arranged in a Katakana letter C shape, and the resin mold 61 is provided in the integral case 60. FIG. 6 is a side view according to a modified example of the embodiment of the present invention in which a structure in which filling and fixing are performed and a transporter 3 is disposed through a common tunnel 64 is shown. In this example, the transmission / reception opposed arrangement type search coil 20 and the coaxial arrangement type search coil 30 are combined. In this case, the size can be further reduced .
[0035]
【The invention's effect】
As described above, according to the present invention, each reception when passing through the transmission / reception opposed arrangement type search coil and the transmission / reception coaxial arrangement type search coil arranged with inclination angles opposite to each other with respect to the transport direction. Since the metallic foreign matter mixed in the subject is detected based on the signal, even if the metallic foreign matter cannot be detected by one search coil, the metallic foreign matter can be detected by the other search coil. Regardless of the direction of the acicular metal foreign matter mixed in the subject, all the acicular metal foreign matters can be detected.
[Brief description of the drawings]
1 is a side view of the needle detector according to an embodiment of the present invention.
FIG. 2 is a front view of the needle detector , similarly .
FIG. 3 is an explanatory perspective view showing a configuration of a transmission / reception opposed arrangement type search coil.
4 is a cross-sectional view in the A direction of FIG .
FIG. 5 is an explanatory perspective view showing the configuration of the arrangement of transmission coils and reception coils of a transmission / reception coaxial arrangement type search coil .
6 is a cross-sectional view in the B direction of FIG .
FIG. 7 is a side view according to a modification of the embodiment of the present invention.
FIG. 8 is a side view for explaining the overall configuration of a needle detector according to the prior art .
FIG. 9 is an explanatory diagram showing the flow of magnetic flux when the ferromagnetic metal test object in the cross section A of the transmission / reception counter-arranged search coil is in a posture that matches the direction of the excitation magnetic flux .
FIG. 10 is an explanatory diagram showing the flow of magnetic flux when the posture of the non-magnetic metal needle-like test object in the cross section A of the search coil coincides with the transport direction P and is perpendicular to the direction of the excitation magnetic flux. .
11 is a explanation diagram illustrating a fourth example of a needle-shaped test object in the state in which the pair of search coils are disposed in the form of a slanted roof Katakana.
FIG. 12 is a cross-sectional view taken along the carrying direction in the case of a transmission / reception opposed arrangement type search coil.
FIG. 13 is a side view according to a modified example of the embodiment of the present invention in which a housing is filled and fixed with a resin mold .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 Conveyor 4,64 Tunnel passage 5 Drive pulley 6 Bearing stand 7 Frame 8 Bearing 10 Needle detector 20 Transmission / reception opposing arrangement type search coil 21 , 31 Transmission coil 22 , 32 Reception coil 23 , 33 Excitation magnetic flux 24 Interlinkage magnetic flux 30 Transmission / reception coaxial Type search coil 40 Needle-like metal foreign object (test object)
41 Subject 50 , 51 Control panel 60 Housing 61 Resin mold

Claims (2)

Transmission / reception facing arrangement type search coil or transmission / reception coaxial arrangement composed of a transmission coil connected to a direct current or alternating current magnetic field type excitation source and a reception coil arranged so that the excitation magnetic flux passes through the transmission coil. The receiving coil detects the disturbance of the excitation magnetic flux caused by the metal foreign matter mixed in the subject that has crossed the excitation magnetic flux generated by the transmission coil or along the excitation magnetic flux in the type search coil. In a metal detection method for detecting a metal foreign object in the subject by calculating a signal, inclination angles opposite to each other with respect to the transport direction of the subject are set along a transport path along which the subject is transported. of outputting the reception coaxial arrangement type search coil and the transceiver opposed type search coils arranged respectively have when the subject has passed respectively Metal detection method is characterized in that to detect the metallic foreign matter mixed in the object based on the received signal. A transmission / reception counter arrangement type search coil or a transmission / reception coaxial arrangement type search coil composed of a transmission coil and a reception coil arranged so as to pass through the excitation coil opposite to the transmission coil, and excitation magnetic flux generated by the transmission coil respectively. A transport means for transporting the subject across or along the excitation magnetic flux, and the excitation magnetic flux generated by the metallic foreign matter mixed in the subject by calculating the received signal detected by the reception coil. In a metal detector having a metal detection means for detecting disturbance and detecting a metal foreign object in the subject, at least a pair of the search coils having different arrangement types along a transport path along which the subject is transported There are arranged with an inclination angle opposite to each other, the metal detector is output from said search coil of each when the subject has passed respectively Metal detector being characterized in that to detect the metallic foreign matter mixed in the object based on the respective received signals.

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