metal detector

Abstract

To provide a metal detector that can maintain the receiving coil in an equilibrium state when no metal is detected, even if the receiving coil or transmitting coil overheats. [Solution] The system comprises a transmitting coil 2, receiving coils 3 and 4, a coil support 5 that supports these coils 2, 3 and 4 on its outer surface 5a, an outer housing 6 that houses the coil support 5 in a predetermined position with a gap between it and the inner wall 6a, and a fixing member 7 that fixes the coils 2, 3 and 4 to the coil support 5. The coils 2, 3 and 4 are formed in a plate shape with both sides having wide flat surfaces 2a, 3a and 4a. The transmitting coil 2 and the receiving coils 3 and 4 are arranged at a predetermined distance apart in the direction of transport of the object to be inspected and are wound around the coil support 5. The fixing member 7 is partially provided around the outer circumference of the coil support 5.

Description

Technical Field

[0001] The present invention relates to a metal detector.

Background Art

[0002] In Patent Document 1, in a metal detector in which a detection head of a coaxial type in which a pair of receiving coils and a transmitting coil are wound around the outer periphery of a coil frame is housed in a metal housing, between the inner wall of the metal housing and the receiving coil and the transmitting coil, A metal detector is disclosed in which a non-metallic filler is inserted in a state with a gap, and a filler is filled in the gap to fix the receiving coil and the transmitting coil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the metal detector described in Patent Document 1, when the receiving coil or the transmitting coil generates heat, for example, due to the difference in the coefficient of thermal expansion between the surrounding components such as the coil frame and the filler, mechanical distortion may occur. When such mechanical distortion occurs, it may not be possible to maintain a state where the difference in the induced voltages of the two receiving coils induced by the transmitting coil becomes zero (hereinafter referred to as the "equilibrium state") during non-detection, and there is a possibility that metal detection cannot be accurately performed.

[0005] In addition, depending on the thermal conductivity of the filler, sufficient heat dissipation may not be expected. In that case, heat may locally concentrate, which may further lead to mechanical distortion.

[0006] This invention has been made in view of the circumstances described above, and aims to provide a metal detector that can maintain the receiving coil in an equilibrium state when no detection is occurring, even when the receiving coil or transmitting coil generates heat. [Means for solving the problem]

[0007] The metal detector according to the present invention comprises a transmitting coil (2) that generates an alternating magnetic field in an inspection area (R) through which an object to be inspected (W) passes, and receiving coils (3, 4) that detect fluctuations in the alternating magnetic field when the object to be inspected passes through the inspection area, and detects metal in the object to be inspected based on the fluctuations in the alternating magnetic field detected by the receiving coil, wherein the inspection area is formed inside a cylindrical coil support (5) that supports the transmitting coil and the receiving coil on its outer surface (5a), and the coil support has an inner wall ( The device comprises an outer housing (6) that houses the device in a predetermined position with a gap between it and 6a), and a fixing member (7) that fixes the transmitting coil and the receiving coil to the coil support, wherein the transmitting coil and the receiving coil are formed in a plate shape with both sides having wide flat surfaces (2a, 3a, 4a), the transmitting coil and the receiving coil are arranged at a predetermined distance apart in the direction of movement of the object to be inspected and are wound around the coil support, and the fixing member is partially provided around the outer circumference of the coil support.

[0008] With this configuration, the metal detector according to the present invention has a transmitting coil and a receiving coil, both formed in a plate shape with wide, flat surfaces on both sides, arranged at a predetermined distance apart in the direction of movement of the object to be inspected and wound around a coil support. Since a fixing member supports the transmitting coil and the receiving coil, both coils can be firmly fixed to the coil support without filling the entire space between the coil support and the outer casing with filler material. As a result, since it is not necessary to fill the entire space between the coil support and the outer casing with filler material, it is possible to suppress the occurrence of mechanical distortion caused by differences in thermal expansion coefficients between surrounding parts such as the coil support and the filler material when the receiving coil or transmitting coil generates heat.

[0009] Furthermore, since the coil support is housed in a predetermined position within the outer casing with a gap between it and the inner wall of the outer casing, and the fixing members are partially provided around the outer circumference of the coil support, more space can be created within the outer casing. This promotes heat convection, improves heat dissipation, and prevents localized heat concentration.

[0010] Therefore, the metal detector according to the present invention can maintain the receiving coil in an equilibrium state when no detection occurs, even if the receiving coil or transmitting coil generates heat.

[0011] Furthermore, in the metal detector according to the present invention, the transmitting coil and the receiving coil are wound around the coil support such that their flat surfaces intersect in the direction of movement of the object to be inspected.

[0012] With this configuration, the metal detector according to the present invention can expose both flat surfaces of the plate-shaped transmitting coil and receiving coil to the space inside the outer casing, thereby improving heat dissipation.

[0013] Furthermore, in the metal detector according to the present invention, the transmitting coil and the receiving coil are configured to be wound around the coil support such that the flat surface is aligned with the direction of movement of the object to be inspected.

[0014] This configuration allows the metal detector according to the present invention to firmly fix both the transmitting coil and the receiving coil to the coil support while increasing the contact area between the transmitting coil and the space inside the outer casing.

[0015] The metal detector according to the present invention comprises a transmitting coil (102) that generates an alternating magnetic field in an inspection area (R) through which an object to be inspected (W) passes, and receiving coils (103, 104) that detect fluctuations in the alternating magnetic field when the object to be inspected passes through the inspection area, and detects metal in the object to be inspected based on the fluctuations in the alternating magnetic field detected by the receiving coil, and comprises a coil support (105) formed in the shape of a plate, which supports the transmitting coil and the receiving coil on one side (105a) and has the inspection area provided on the side of the one side, and an outer housing (106) that houses the coil support in a predetermined position with a gap between it and its inner wall (106a), wherein the transmitting coil and the receiving coil are formed in the shape of a plate with both sides having wide flat surfaces (102a, 103a, 104a), and the transmitting coil and the receiving coil are supported by the coil support with their flat surfaces aligned with the direction of movement of the object to be inspected.

[0016] With this configuration, the metal detector according to the present invention has a transmitting coil and a receiving coil, both formed in a plate shape with wide, flat surfaces on both sides, and these flat surfaces are supported on a coil support with their orientation aligned with the direction of movement of the object being inspected. As a result, both coils can be firmly fixed to the coil support without filling the entire space between the coil support and the outer casing with filler material. This eliminates the need to fill the entire space between the coil support and the outer casing with filler material, thus suppressing the occurrence of mechanical distortion caused by differences in thermal expansion coefficients between surrounding components such as the coil support and the filler material when the receiving coil or transmitting coil generates heat.

[0017] Furthermore, since the coil support is housed in a predetermined position within the outer casing with a gap between it and the inner wall of the outer casing, more space can be created within the outer casing. This promotes heat convection, improves heat dissipation, and prevents heat from concentrating in specific areas.

[0018] Therefore, the metal detector according to the present invention can maintain the receiving coil in an equilibrium state when no detection occurs, even if the receiving coil or transmitting coil generates heat.

[0019] Also, in the metal detector according to the present invention, the transmitting coil and the receiving coil are formed of flat wires and are wound edgewise around the coil support.

[0020] With this configuration, in the metal detector according to the present invention, since the transmitting coil and the receiving coil are formed of flat wires and are wound edgewise around the coil support, the surface area of both coils can be increased compared to a round wire coil, and the heat dissipation performance can be enhanced.

[0021] Also, in the metal detector according to the present invention, the transmitting coil and the receiving coil are composed of a coil formed of a copper foil on a coil substrate formed on a substrate.

[0022] With this configuration, in the metal detector according to the present invention, since the transmitting coil and the receiving coil are composed of a coil substrate, the process of winding the coil around the coil support becomes unnecessary, the manufacturing cost can be suppressed, and the quality can be stabilized.

Effects of the Invention

[0023] According to the present invention, it is possible to provide a metal detector that can maintain the receiving coil in an equilibrium state during non-detection even when the receiving coil or the transmitting coil generates heat.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a schematic configuration diagram showing the configuration of a metal detector according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the holding structure of each coil of the metal detector according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view seen from the direction of arrow III of a cross-section cut along a virtual plane S1 in FIG. 2. [Figure 4] FIG. 4 is a schematic diagram showing the holding structure of each coil of a metal detector according to a comparative example. [Figure 5] Figure 5 is a schematic cross-sectional view of the cross-section cut by the virtual plane S2 in Figure 4, viewed from the direction of arrow V. [Figure 6] Figure 6 is a schematic diagram showing a modified example of a metal detector according to the first embodiment of the present invention. [Figure 7] Figure 7 is a schematic diagram showing the configuration of a metal detector according to a second embodiment of the present invention. [Figure 8] Figure 8 is a schematic cross-sectional view of the cross-section cut by the virtual plane S3 in Figure 7, viewed from the direction of arrow VIII. [Figure 9] Figure 9 is a schematic cross-sectional view showing a modified example of a metal detector according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0025] (First embodiment) A metal detector according to the first embodiment of the present invention will be described below with reference to Figures 1 to 5.

[0026] [Metal detector configuration] As shown in Figure 1, the metal detector 1 according to this embodiment is a coaxial type metal detector comprising a transmitting coil 2 and a pair of receiving coils 3 and 4.

[0027] The transmitting coil 2 is connected to the magnetic field output unit 21 and is excited by a sinusoidal signal output from the magnetic field output unit 21, thereby generating an alternating magnetic field in the inspection area R through which the object W under inspection passes.

[0028] The pair of receiving coils 3 and 4 are positioned spaced apart from each other, with the transmitting coil 2 in the direction of movement, which is the transport direction of the object W under inspection. Receiving coil 3 is positioned upstream of transmitting coil 2 in the transport direction, and receiving coil 4 is positioned downstream of transmitting coil 2 in the transport direction. Furthermore, receiving coils 3 and 4 are positioned at equal distances from transmitting coil 2.

[0029] The aforementioned inspection area R is a space that is continuous in the transport direction inside the transmitting coil 2 and the receiving coils 3 and 4.

[0030] The object to be inspected W is transported through the inspection area R by a transport means such as a conveyor (not shown). This transport means is provided to penetrate the inspection area R inside the transmitting coil 2 and the receiving coils 3 and 4.

[0031] The pair of receiving coils 3 and 4 equally receive the magnetic flux of the alternating magnetic field generated by the transmitting coil 2, and are configured to detect fluctuations in the alternating magnetic field when the object under inspection W passes through the inspection area R.

[0032] A pair of receiving coils 3 and 4 are connected to a magnetic field receiving unit 31. The magnetic field receiving unit 31 outputs a received signal, which is the difference in the induced voltages of the receiving coils 3 and 4. The received signal output from the magnetic field receiving unit 31 is processed by a signal processing unit 32 and then output as a detection signal.

[0033] Thus, the metal detector 1 of this embodiment detects the difference in induced voltages between receiving coils 3 and 4 as a fluctuation in the alternating magnetic field, and detects metal in the object W under inspection based on this fluctuation in the alternating magnetic field.

[0034] [Holding structure for each coil] As shown in Figures 2 and 3, the metal detector 1 of this embodiment is configured to include, in addition to the above-described components, a coil support 5, an outer casing 6, and a fixing member 7.

[0035] The coil support 5 is a cylindrical, specifically rectangular, resin frame with openings on the upstream and downstream sides in the transport direction of the object W to be inspected (see Figure 1). The inspection area R described above is formed inside the coil support 5.

[0036] The coil support 5 has an outer circumferential surface 5a, and the transmitting coil 2 and the receiving coils 3 and 4 are supported on this outer circumferential surface 5a.

[0037] The outer casing 6 is configured as a housing that surrounds the frame-shaped coil support 5 while securing space for the inspection area R. In other words, the outer casing 6 has a square shape so that a transport means (not shown) passes through the inspection area R, and has a space inside that can accommodate the frame-shaped coil support 5.

[0038] The outer casing 6 is made of a metal such as aluminum alloy or stainless steel, which acts as a magnetic shield.

[0039] The outer casing 6 has an inner wall 6a, and is designed to house the coil support 5 in a predetermined position with a gap between it and the inner wall 6a. For example, the outer casing 6 houses the coil support 5 in a predetermined position by erecting a plurality of columnar positioning pieces 61 (see Figure 3) between it and the coil support 5, and fixing these positioning pieces 61 to the coil support 5 and the outer casing 6.

[0040] In this embodiment, it is desirable to use the minimum number of positioning pieces 61 necessary to maintain the coil support 5 in a predetermined position, and to make the internal space of the outer housing 6 as free space as possible.

[0041] Furthermore, the method of supporting the coil support 5 on the outer casing 6 is not limited to the example using the positioning piece 61 described above. For example, the coil support 5 may be positioned in a predetermined location by filling only a specific location within the internal space of the outer casing 6 with an epoxy-based (or unsaturated polyester-based) filler material so as to connect the outer circumferential surface 5a of the coil support 5 with the inner wall 6a of the outer casing 6. In this case, the filler material is filled using a mold or the like to prevent it from spreading to locations other than the desired location. This ensures that the filler material is filled only in the specific location within the internal space of the outer casing 6. When using a filler material, similar to the positioning piece 61, it is desirable to limit the placement of the filler material to the minimum number of locations necessary to maintain the coil support 5 in a predetermined position, thereby leaving as much free space as possible within the internal space of the outer casing 6. It is also preferable to provide gaps that allow the internal space of the outer casing 6 to communicate in the circumferential direction.

[0042] In this embodiment, the transmitting coil 2 and receiving coils 3 and 4 consist of wide flat surfaces 2a, 3a, and 4a on both sides, and the thickness surface connecting these two sides is formed in a narrow plate shape. Specifically, the transmitting coil 2 and receiving coils 3 and 4 are made of flat wires, the cross-sectional shape perpendicular to the coil extension direction is formed in a rectangular shape by the longer side of the flat surface and the shorter side of the thickness surface.

[0043] The transmitting coil 2 and the receiving coils 3 and 4 are wound around the outer surface 5a of the coil support 5 with the wide, flat surfaces 2a, 3a, and 4a of the flat wire perpendicular to the transport direction of the object W under inspection (see Figure 1). In other words, the transmitting coil 2 and the receiving coils 3 and 4 are edge-wound around the outer surface 5a of the coil support 5.

[0044] The transmitting coil 2 and the receiving coils 3 and 4 are arranged at predetermined intervals in the direction of transport of the object W to be inspected (see Figure 1) by a fixing member 7.

[0045] The fixing member 7 is a resin member that fixes the transmitting coil 2 and the receiving coils 3 and 4 to the coil support 5. The fixing member 7 may be integrally formed with the coil support 5, or it may be a separate component and attached to the coil support 5 by fastening members (not shown) or adhesives.

[0046] The fixing member 7 is formed in a rectangular parallelepiped shape to support the flat surfaces 2a, 3a, and 4a of the transmitting coil 2 and the receiving coils 3 and 4, respectively. The shape of the fixing member 7 is not limited to a rectangular parallelepiped; it may be any shape that can support the flat surfaces of each coil, such as a cube.

[0047] In this embodiment, multiple fixing members 7 are provided partially, or intermittently, around the outer circumference of the coil support 5 between the transmitting coil 2 and the receiving coil 3, and between the transmitting coil 2 and the receiving coil 4. As a result, a space is formed between adjacent fixing members 7 in the circumferential direction. Therefore, in areas where there are no fixing members 7, the flat surfaces 2a, 3a, and 4a of the transmitting coil 2 and the receiving coils 3 and 4 are exposed to the internal space of the outer housing 6.

[0048] In this embodiment, it is desirable to use the minimum number and size of fixing members 7 that can support the transmitting coil 2 and the receiving coils 3 and 4 while maintaining their relative positions, and to make the space between adjacent fixing members 7 in the circumferential direction as large as possible.

[0049] [Metal detectors related to comparative examples] Figures 4 and 5 show a metal detector 11 in which the space between the coil support 15 and the outer casing 6, i.e., the internal space of the outer casing 6, is filled with a filler material. In Figures 4 and 5, components similar to those in the metal detector 1 of this embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0050] As shown in Figures 4 and 5, in the comparative example metal detector 11, grooves 15b are formed on the outer circumferential surface 15a of the coil support 15 so as to extend in the circumferential direction. Three of these grooves 15b are provided at predetermined intervals in the direction in which the object to be inspected W is transported (see Figure 1).

[0051] Each groove 15b houses a transmitting coil 12 and receiving coils 13 and 14, both made of round wire coils. The transmitting coil 12 and receiving coils 13 and 14 are sealed within the grooves 15b by fixing members 17 while housed in the grooves 15b. The fixing members 17 are provided along the entire circumference. Note that the fixing members 17 are optional, or fasteners such as screws may be used instead of the fixing members 17 for fastening.

[0052] The space between the coil support 15 and the outer casing 6, that is, the internal space of the outer casing 6, is completely filled with filler material 18. As a result, the transmitting coil 12 and the receiving coils 13 and 14 are firmly fixed to the coil support 15.

[0053] In a metal detector 11 with this configuration, when the transmitting coil 12 or receiving coils 13 and 14 generate heat, mechanical distortion may occur due to the difference in thermal expansion coefficients between surrounding components such as the coil support 15 and the filler material 18.

[0054] Furthermore, if the transmitting coil 12 and the receiving coils 13 and 14 generate heat, heat may concentrate locally near each coil, mainly within the groove 15b where the transmitting coil 12 and the receiving coils 13 and 14 are sealed by the fixing material 17 and the filler material 18, which could lead to further mechanical distortion.

[0055] In contrast, in the metal detector 1 of this embodiment, the transmitting coil 2 and the receiving coils 3 and 4 are made of flat rectangular wire, are edge-wound around the outer surface 5a of the coil support 5, and are firmly fixed to the coil support 5 by a fixing member 7. Therefore, the transmitting coil 2 and the receiving coils 3 and 4 can be firmly fixed to the coil support 5 without filling the space between the coil support 5 and the outer housing 6, i.e., the internal space of the outer housing 6, with filler material. Furthermore, the exposed area of ​​the transmitting coil 2 and the receiving coils 3 and 4 to the internal space of the outer housing 6 is increased, improving heat dissipation. In addition, sufficient free space is secured within the internal space of the outer housing 6, so heat convection is easily generated within the internal space of the outer housing 6, and sufficient heat dissipation is achieved.

[0056] [Effects and Effects] As described above, in the metal detector according to this embodiment, the transmitting coil 2 and receiving coils 3 and 4, which are formed in a plate shape with both sides having wide, flat surfaces, are arranged at a predetermined distance apart in the transport direction of the object to be inspected W, and the flat surfaces 2a, 3a, and 4a are wound around the coil support 5 in a state perpendicular to the transport direction of the object to be inspected W, and the fixing member 7 supports the flat surfaces 2a, 3a, and 4a of the transmitting coil 2 and the receiving coils 3 and 4, so that the transmitting coil 2 and the receiving coils 3 and 4 can be firmly fixed to the coil support 5 without filling the entire space between the coil support 5 and the outer housing 6 with filler material.

[0057] As a result, it is not necessary to fill the entire space between the coil support 5 and the outer casing 6 with filler material, thus suppressing the occurrence of mechanical distortion caused by differences in thermal expansion coefficients between surrounding components such as the coil support 5 and the filler material when the receiving coils 3 and 4 or the transmitting coil 2 generate heat.

[0058] Furthermore, since the coil support 5 is housed in a predetermined position within the outer casing 6 with a gap between it and the inner wall 6a of the outer casing 6, and multiple fixing members 7 are intermittently provided around the outer circumference of the coil support 5, more space can be created within the outer casing 6. This promotes heat convection, improves heat dissipation, and prevents localized heat concentration.

[0059] Therefore, in this embodiment, even if the receiving coils 3 and 4 or the transmitting coil 2 generate heat, the metal detector can maintain the receiving coils 3 and 4 in an equilibrium state when no detection occurs.

[0060] Furthermore, in this embodiment, the metal detector has a transmitting coil 2 and receiving coils 3 and 4 made of flat rectangular wire, which are edge-wound around the coil support 5. Compared to round wire coils, this increases the surface area of ​​the transmitting coil 2 and receiving coils 3 and 4, thereby improving heat dissipation.

[0061] [Differentiation] In this embodiment, an example using flat rectangular wire as the transmitting coil 2 and receiving coils 3 and 4 has been described. However, the invention is not limited to this, and for example, a coil substrate in which coils made of copper foil are formed on a substrate may be used as the transmitting coil 2 and receiving coils 3 and 4.

[0062] In this case, each coil substrate is erected on the outer surface 5a of the coil support 5 with both sides of the substrate perpendicular to the transport direction of the object W under inspection. As a result, the copper foil coil formed on each coil substrate is effectively wound around the coil support 5.

[0063] Thus, even when a coil substrate is used as the transmitting coil 2 and the receiving coils 3 and 4, the same effects as in this embodiment can be obtained. Furthermore, since the transmitting coil 2 and the receiving coils 3 and 4 are made of a coil substrate, the process of winding the coils onto the coil support 5 is unnecessary, which reduces manufacturing costs and ensures stable quality.

[0064] Furthermore, in this embodiment, an example was described in which the transmitting coil 2 and receiving coils 3 and 4 are wound around the coil support 5 with their flat surfaces 2a, 3a, and 4a perpendicular to the transport direction of the object W under inspection. However, the embodiment is not limited to this, and the transmitting coil 2 and receiving coils 3 and 4 may be wound around the coil support 5 with their flat surfaces 2a, 3a, and 4a intersecting the transport direction at various angles other than perpendicular to the transport direction.

[0065] Furthermore, as shown in Figure 6, the transmitting coil 2 and the receiving coils 3 and 4 may be wound around the coil support 5 such that their flat surfaces 2a, 3a, and 4a are aligned with the direction of transport of the object W to be inspected, for example, parallel to the outer surface 5a of the coil support 5. The state aligned with the direction of transport of the object W to be inspected includes not only the parallel state but also the approximately parallel state, that is, the state inclined by ± a small angle from the parallel state.

[0066] In the configuration shown in Figure 6, for example, it is preferable to use a common fixing member 27 for the transmitting coil 2 and the receiving coils 3 and 4 instead of the fixing member 7. The fixing member 27 is made of resin, is configured separately from the coil support 5, and is attached to the coil support 5 by fastening members or adhesives (not shown). The fixing member 27 may not be common, but may be provided individually for each of the transmitting coil 2 and the receiving coils 3 and 4.

[0067] As shown in Figure 6, the transmitting coil 2 and the receiving coils 3 and 4 are supported by being sandwiched between the fixing member 27 and the outer circumferential surface 5a of the coil support 5.

[0068] Furthermore, in this embodiment, an air circulation device such as a fan may be provided in the internal space of the outer casing 6. This can promote air circulation within the internal space of the outer casing 6, further promoting heat convection.

[0069] (Second embodiment) A metal detector according to a second embodiment of the present invention will be described below with reference to Figures 7 and 8.

[0070] As shown in Figures 7 and 8, the metal detector 101 according to this embodiment is a single-sided metal detector in which a transmitting coil 102 and a pair of receiving coils 103 and 104 are provided on one side of the inspection area R, for example, on the lower side.

[0071] The metal detector 101 is installed, for example, below a conveying means such as a conveying belt that transports the object to be inspected W.

[0072] The transmitting coil 102 and the receiving coils 103 and 104 are made of a coil substrate in which coils, for example, made of copper foil, are formed on a substrate. In other words, the transmitting coil 102 and the receiving coils 103 and 104 are formed in a plate shape with both sides having wide flat surfaces 102a, 103a, and 104a.

[0073] In this embodiment, the receiving coils 103 and 104 share a common substrate, and the aforementioned flat surfaces 103a and 104a are formed on both sides of this common substrate.

[0074] The transmitting coil 102 is formed to surround the receiving coils 103 and 104 in the same plane as the receiving coils 103 and 104.

[0075] The receiving coils 103 and 104 are arranged in the area enclosed by the transmitting coil 102, with the receiving coil 103 and the receiving coil 104 positioned side by side in the direction of transport of the object W under inspection. Specifically, the receiving coil 103 is positioned on the upstream side in the transport direction, and the receiving coil 104 is positioned on the downstream side in the transport direction.

[0076] In this embodiment, the transmitting coil 102 and the receiving coils 103 and 104 are formed in a total of two layers, one layer on each side of the substrate. The transmitting coil 102 and the receiving coils 103 and 104 may be formed in double layers on the same plane on one side of the substrate, or they may be single layers formed on only one side of the substrate. The number of turns for the transmitting coil 102 and the receiving coils 103 and 104 is not limited to the number of turns described above.

[0077] The functions of the transmitting coil 102 and the receiving coils 103 and 104 are the same as those of the transmitting coil 2 and receiving coils 3 and 4 in the first embodiment.

[0078] The metal detector 101 of this embodiment is configured to include a coil support 105 and an outer casing 106.

[0079] The coil support 105 is formed in a plate shape and supports the transmitting coil 102 and the receiving coils 103 and 104 on one surface (the upper surface in this embodiment) 105a. An inspection area R is provided on the upper side of one surface 105a of the coil support 105.

[0080] Multiple boss portions 107 are erected on one surface 105a of the coil support 105. The transmitting coil 102 and the receiving coils 103 and 104 are supported by the coil support 105 via the aforementioned boss portions 107, with their flat surfaces 102a, 103a, and 104a parallel to the transport direction of the object to be inspected W. The transmitting coil 102 and the receiving coils 103 and 104 are attached to the tips (upper ends in this embodiment) of the boss portions 107 by fastening members such as screws (not shown).

[0081] The outer casing 106 is formed in a hollow, box-like shape and has a space inside capable of housing the coil support 105. The outer casing 106 is made of a metal such as aluminum alloy or stainless steel, which acts as a magnetic shield.

[0082] The outer casing 106 has an inner wall 106a, and is designed to house the coil support 105 in a predetermined position with a gap between it and the inner wall 106a. For example, the outer casing 106 houses the coil support 105 in a predetermined position by erecting a plurality of columnar positioning pieces 161 (see Figure 8) between it and the lower surface of the coil support 105, and fixing these positioning pieces 161 to the coil support 105 and the outer casing 106.

[0083] In this embodiment, it is desirable to use the minimum number of positioning pieces 161 necessary to maintain the coil support 105 in a predetermined position, and to make the internal space of the outer housing 106 as free space as possible.

[0084] In addition, as with the first embodiment, the coil support 105 may be positioned in a predetermined location using a filler material as a method of supporting it on the outer housing 106. Even in this case, it is desirable to limit the number of filler material placement locations to the minimum number necessary to maintain the coil support 105 in its predetermined position, and to leave as much free space as possible within the outer housing 106. Furthermore, it is preferable to provide a gap that connects one side of the filler material to the other side so that no closed space is created within the inner space of the outer housing 106.

[0085] [Effects and Effects] As described above, in the metal detector according to this embodiment, the transmitting coil 102 and receiving coils 103 and 104, which are formed in a plate shape with both sides having wide flat surfaces 102a, 103a and 104a, are supported on the coil support 105 with their flat surfaces 102a, 103a and 104a parallel to the transport direction of the object to be inspected W. Therefore, both coils can be firmly fixed to the coil support 105 without filling the entire space between the coil support 105 and the outer casing 106 with filler material. As a result, since it is not necessary to fill the entire space between the coil support 105 and the outer casing 106 with filler material, it is possible to suppress the occurrence of mechanical distortion caused by the difference in thermal expansion coefficients between surrounding parts such as the coil support 105 and the filler material when the receiving coils 103 and 104 or the transmitting coil 102 generate heat.

[0086] Furthermore, since the coil support 105 is housed in a predetermined position within the outer casing 106 with a gap between it and the inner wall 106a of the outer casing 106, more space can be created within the outer casing 106. This promotes heat convection, improves heat dissipation, and prevents localized heat concentration.

[0087] Therefore, in this embodiment, even if the receiving coils 103 and 104 or the transmitting coil 102 generate heat, the metal detector can maintain the receiving coils 103 and 104 in an equilibrium state when no detection occurs.

[0088] Furthermore, in this embodiment, since the transmitting coil 102 and receiving coils 103 and 104 are made of coil substrates, the process of winding the coils onto the coil support 105 is unnecessary, which reduces manufacturing costs and ensures stable quality.

[0089] [Differentiation] In this embodiment, an example using a coil substrate as the transmitting coil 102 and receiving coils 103 and 104 has been described. However, the invention is not limited to this, and for example, flat wire may be used as the transmitting coil 102 and receiving coils 103 and 104. In this case, the transmitting coil 102 and receiving coils 103 and 104, which are made of flat wire, are supported on one side (the top surface in this embodiment) 105a of the coil support 105, with their flat surfaces 102a, 103a, and 104a parallel to the transport direction of the object under inspection W. In other words, the transmitting coil 102 and receiving coils 103 and 104 are edge-wound with respect to the coil support 105 with their flat surfaces 102a, 103a, and 104a parallel to the transport direction of the object under inspection W. This increases the surface area of ​​the transmitting coil 102 and receiving coils 103 and 104 compared to round wire coils, thereby improving heat dissipation.

[0090] Furthermore, if the transmitting coil 102 and the receiving coils 103 and 104 are made of flat rectangular wire, and if the coil substrate has coils formed only on its upper surface, the transmitting coil 102 and the receiving coils 103 and 104 may be directly fixed to the coil support 105 without using the boss portion 107.

[0091] In this case, as shown in Figure 9, it is desirable that a plurality of grooves 108 are formed on one surface (the top surface in this embodiment) 105a of the coil support 105. Figure 9 shows an example in which the transmitting coil 102 and the receiving coils 103 and 104 are coil substrates in which coils are formed only on the top surface.

[0092] The arrangement of the multiple grooves 108 may be, for example, multiple grooves extending in one direction of the coil support 105 arranged in parallel in a direction perpendicular to that direction, or the multiple grooves may be arranged in a grid pattern.

[0093] As a result, air circulates through the multiple grooves 108, improving heat dissipation and preventing heat from concentrating locally near the transmitting coil 102 and the receiving coils 103 and 104.

[0094] Furthermore, although this embodiment describes an example of application to a single-sided metal detector, it is not limited to this, and can also be applied to a counter-type metal detector in which a transmitting coil 102 and a pair of receiving coils 103 and 104, arranged on the same surface, face each other across an inspection area R. In this case, for example, a configuration in which the transmitting coil 102 side and the receiving coils 103 and 104 sides are each held in separate housings, or a configuration in which they are each held within the same U-shaped housing, is conceivable, but in either configuration, the configuration of this embodiment can be applied to the transmitting coil 102 side and the receiving coils 103 and 104 sides, respectively.

[0095] Furthermore, in this embodiment, an air circulation device such as a fan may be provided in the internal space of the outer casing 106. This can promote air circulation within the internal space of the outer casing 106, further promoting heat convection.

[0096] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of symbols]

[0097] 1.101 Metal Detector 2, 102 Transmitting Coil 3, 4, 103, 104 Receiving coils 2a, 3a, 4a, 102a, 103a, 104a flat surface 5, 105 Coil support 5a Outer surface 6, 106 Outer casing 6a, 106a inner wall 7 Fixing members 21 Magnetic field output section 31 Magnetic field receiving section 32 Signal Processing Unit 61 Positioning piece 105a One side 107 Boss Section 108 Groove 161 Positioning piece W: Object under inspection R testing area

Claims

1. A transmitting coil (2) generates an alternating magnetic field in the inspection area (R) through which the object to be inspected (W) passes, The system includes receiving coils (3, 4) that detect fluctuations in the alternating magnetic field when the object to be inspected passes through the inspection area, A metal detector that detects metal in an object under inspection based on fluctuations in the alternating magnetic field detected by the receiving coil, The inspection area is formed inside a cylindrical coil support (5) that supports the transmitting coil and the receiving coil on its outer surface (5a), An outer housing (6) that houses the coil support in a predetermined position with a gap between it and its inner wall (6a), A fixing member (7) for fixing the transmitting coil and the receiving coil to the coil support, Equipped with, The transmitting coil and the receiving coil are formed in a plate shape with both sides having wide, flat surfaces (2a, 3a, 4a). The transmitting coil and the receiving coil are arranged at a predetermined distance apart in the direction of movement of the object under inspection and are wound around the coil support. The fixing member is partially provided around the outer circumference of the coil support, in a metal detector.

2. The metal detector according to claim 1, wherein the transmitting coil and the receiving coil are wound around the coil support such that their flat surfaces intersect in the direction of movement of the object to be inspected.

3. The metal detector according to claim 1, wherein the transmitting coil and the receiving coil are wound around the coil support such that the flat surface is aligned with the direction of movement of the object to be inspected.

4. A transmitting coil (102) generates an alternating magnetic field in the inspection area (R) through which the object to be inspected (W) passes, The system includes receiving coils (103, 104) that detect fluctuations in the alternating magnetic field when the object to be inspected passes through the inspection area, A metal detector that detects metal in an object under inspection based on fluctuations in the alternating magnetic field detected by the receiving coil, A coil support (105) formed in a plate shape, supporting the transmitting coil and the receiving coil on one side (105a), and having the inspection area provided on the side of the one side, An outer housing (106) that houses the coil support in a predetermined position with a gap between it and its inner wall (106a), Equipped with, The transmitting coil and the receiving coil are formed in a plate shape with both sides having wide, flat surfaces (102a, 103a, 104a), A metal detector in which the transmitting coil and the receiving coil are supported by the coil support such that the flat surface is aligned with the direction of movement of the object to be inspected.

5. The metal detector according to any one of claims 1 to 4, wherein the transmitting coil and the receiving coil are made of flat rectangular wire and are edge-wound with respect to the coil support.

6. The metal detector according to any one of claims 1 to 4, wherein the transmitting coil and the receiving coil consist of a coil substrate in which coils made of copper foil are formed on a substrate.

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