Detection device

Abstract

To improve detection accuracy of a magnetic substance by inducing lines of magnetic force occurring from the magnetic substance to a magnetic sensor when detecting the presence of the magnetic substance on the basis of a signal outputted from the magnetic sensor.SOLUTION: A detection device comprises: a magnetic sensor including a sensing element which includes a soft magnetic substance, has a longitudinal direction and a lateral direction, has uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and senses a magnetic field by a magnetic impedance effect; a first induction member which faces one end in the longitudinal direction of the magnetic sensor, extends in a direction away from the one end, and induces lines of magnetic force to the sensing element of the magnetic sensor; and a second induction member which faces the other end in the longitudinal direction of the magnetic sensor, extends in a direction away from the other end while facing the first induction member via a gap and induces the lines of magnetic force to the sensing element of the magnetic sensor together with the first induction member. One of the first induction member and the second induction member is inserted to a hollow part of a cylindrical object having the hollow part to detect a magnetic substance included in the object.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a detection device. [Background technology]

[0002] As a conventional technique, Patent Document 1 discloses a metallic foreign matter detection device that uses a magnetic sensor to detect magnetic fluctuations in an AC magnetic field resulting from metallic foreign matter present on the surface or inside of a substrate. Furthermore, as a prior art, Patent Document 2 discloses a magnetic sensor that includes a sensing element, a focusing member that focuses magnetic lines of force from external space onto the sensing element, and a dissipating member that dissipates the magnetic lines of force that have passed through the sensing element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-102513 A [Patent Document 2] Patent Publication No. 2022-98575 Summary of the Invention [Problem to be solved by the invention]

[0004] In a detection device that detects the presence of a magnetic body based on a signal output from a magnetic sensor, it is preferable to efficiently guide the magnetic field lines emitted from the magnetic body to the magnetic sensor in order to increase detection accuracy. The present invention aims to improve the detection accuracy of a magnetic body by inducing magnetic field lines emitted from the magnetic body to the magnetic sensor when detecting the presence of a magnetic body based on a signal output from a magnetic sensor. [Means for solving the problem]

[0005] According to the present invention, the following inventions (1) to (3) are provided. (1) A magnetic sensor (magnetic sensor 10) including a soft magnetic material, a longitudinal direction and a transverse direction, a sensing element (sensing element 121) having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and sensing a magnetic field by a magneto-impedance effect; a first induction member (first induction member 20) that faces one end of the magnetic sensor in the longitudinal direction, extends in a direction away from the end, and induces magnetic lines of force to the sensing element of the magnetic sensor; a second induction member (20) that faces the other end of the magnetic sensor in the longitudinal direction, faces the first induction member via a gap (gap S), extends in a direction away from the other end, and induces magnetic lines of force to the sensing element of the magnetic sensor together with the first induction member; A detection device that detects a magnetic body contained in a cylindrical object by inserting one of the first induction member and the second induction member into the hollow portion of the cylindrical object having a hollow portion. (2) The detection device according to (1), wherein the first guide member and the second guide member face each other in a plurality of directions via the gap. (3) The detection device according to (1), further comprising a magnetizing unit (magnetizing unit 2) that magnetizes the magnetic body in the radial direction of the object. Effect of the Invention

[0006] According to the present invention, when detecting the presence of a magnetic body based on a signal output from a magnetic sensor, the magnetic field lines emitted from the magnetic body can be guided to the magnetic sensor, thereby improving the detection accuracy of the magnetic body. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram illustrating a foreign object detection system to which the present embodiment is applied. [Diagram 2] 11 is a diagram showing the magnetic sensor of the foreign object detection device as viewed from the upstream side in the z direction. [Diagram 3] 3(a) and 3(b) are diagrams illustrating the configuration of a magnetic sensor included in the detection unit shown in FIG. 2. [Figure 4]10 is a diagram showing the relationship between a magnetic field applied in the longitudinal direction of a sensing element in a magnetic sensor and the impedance of the magnetic sensor in a detection section. FIG. [Diagram 5] 13(a) and 13(b) are diagrams illustrating an embodiment in which a foreign object in an object is detected by a magnetic sensor without using a first induction member and a second induction member. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of a conventional detection unit. [Figure 7] 1A to 1C are diagrams illustrating the magnitude of the magnetic field strength in the y direction of the first induction member, the second induction member, and the magnetic sensor when a foreign object made of a magnetic material is present in the gap between the first induction member and the second induction member in the detection unit of this embodiment. [Figure 8] 11 is a diagram showing an average value of the magnetic field strength in the magnetic sensor when the distance in the x direction between the magnetic sensor and a foreign object is changed in the detection unit of this embodiment. FIG. [Figure 9] 13(a) and 13(b) are schematic diagrams illustrating the configuration of a detection unit to which the second embodiment is applied. [Figure 10] 1A to 1C are diagrams illustrating the magnitude of the magnetic field strength of the first induction member, the second induction member, and the magnetic sensor when a foreign object made of a magnetic material is present in the gap between the side portion of the first induction member and the second induction member in the detection unit of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. [Embodiment 1] (Configuration of foreign object detection system 1) 1 is a schematic diagram illustrating a foreign object detection system 1 to which this embodiment is applied. The foreign object detection system 1 of this embodiment detects a foreign object 91 made of a magnetic material contained in an object 9. Note that hereinafter, the foreign object 91 made of a magnetic material contained in the object 9 may be simply referred to as a foreign object 91. The foreign object detection system 1 includes a magnetization unit 2 that magnetizes foreign object 91 contained in a target object 9, a detection unit 3 that detects foreign object 91 magnetized by the magnetization unit 2, and a control unit 4 that controls each part of the foreign object detection system 1. In this embodiment, the foreign object detection system 1 or the detection unit 3 is an example of a detection device that detects a magnetic body contained in an object.

[0009] The control unit 4 has, for example, a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) (not shown), a RAM (Random Access Memory) (not shown), etc. The ROM stores a basic program (operation system) executed by the CPU, various settings, etc. The CPU uses the RAM as a working area and executes application programs read from the ROM or a storage unit (not shown) such as a semiconductor memory or a HDD (Hard Disk Drive). The control unit 4 of this embodiment determines whether or not a foreign object 91 is present on the target object 9 based on an electric signal output from a magnetic sensor 10 of the detection unit 3, which will be described later.

[0010] The magnetizing unit 2 magnetizes a foreign matter 91 contained in a target object 9 . The magnetization unit 2 magnetizes a foreign object 91 included in the object 9, which is the object to be magnetized, by using a pair of permanent magnets 2A and 2B arranged on either side of the object 9. Specifically, as shown in FIG. 1, the pair of permanent magnets 2A and 2B are arranged so that their north pole (e.g., the north pole of permanent magnet 2A) and south pole (e.g., the south pole of permanent magnet 2B) face each other. Then, in the magnetization unit 2, magnetic field lines that cross the object 9 are generated between the permanent magnets 2A and 2B. In the magnetization unit 2, the magnetic field lines magnetize the foreign object 91 included in the object 9. In addition, the arrangement of the permanent magnets 2A and 2B in the magnetizing unit 2 is not limited to that shown in Fig. 1 as long as the magnetizing unit 2 generates magnetic lines of force for magnetizing the foreign matter 91 included in the target object 9. Moreover, electromagnets may be used instead of the permanent magnets 2A and 2B. Furthermore, the relationship between the magnetization direction of foreign object 91 by magnetization unit 2 and detection unit 3 in foreign object detection system 1 of this embodiment will be described in detail later.

[0011] (Detection unit 3) The detection unit 3 detects the foreign matter 91 magnetized by the magnetizing unit 2 . Fig. 2 is a schematic diagram for explaining the configuration of the detection unit 3 to which this embodiment is applied. In Fig. 2, magnetic field lines generated from a foreign object 91 included in the target object 9 are indicated by arrows. Figures 3(a) and (b) are diagrams illustrating the configuration of the magnetic sensor 10 included in the detection unit 3 shown in Figure 2. Figure 3(a) is a plan view of the magnetic sensor 10, and Figure 3(b) is a cross-sectional view taken along line IIIB-IIIB in Figure 3(a). In Figures 2 and 3(a), the left-right direction on the paper (direction from left to right) is denoted as the x-direction, the up-down direction on the paper (direction from bottom to top) is denoted as the y-direction, and the depth direction on the paper (direction from front to back) is denoted as the z-direction.

[0012] The detection unit 3 has a magnetic sensor 10 that senses a magnetic field or a change in a magnetic field by the magneto-impedance effect. The detection unit 3 also has a first induction member 20 and a second induction member 30 that induce magnetic lines of force to a sensing element 121 (described later) of the magnetic sensor 10. The detection unit 3 further includes two magnets (a first magnet 61 and a second magnet 62) that apply a predetermined bias magnetic field Hb to the sensing element 121.

[0013] In the detection unit 3 of this embodiment, the first induction member 20 is provided on the upstream side in the y direction (lower side of the paper) of the magnetic sensor 10, and the second induction member 30 is provided on the downstream side in the y direction (upper side of the paper). The first induction member 20 and the second induction member 30 each have a rectangular planar shape with the x direction as the longitudinal direction. The first induction member 20 and the second induction member 30 face each other in the y direction with a gap S extending in the x direction therebetween.

[0014] The detection unit 3 of this embodiment detects a foreign object 91 on a cylindrical object 9 having a cylindrical hollow portion P therein. Specifically, in the detection unit 3 of this embodiment, one of the first guide member 20 and the second guide member 30 is inserted into the hollow portion P of the object 9. Then, the detection unit 3 detects a foreign object 91 contained in the object 9 that exists in the gap S between the first guide member 20 and the second guide member 30. In other words, the detection unit 3 detects a foreign object 91 contained in a portion of the cylindrical object 9 that is sandwiched between the first guide member 20 and the second guide member 30. In the example shown in FIG. 2, the second guide member 30 of the first guide member 20 and the second guide member 30 is inserted into the hollow portion P of the object 9. In addition, in the example shown in FIG. 2, a cylindrical object 9 with a bottom is shown as the cylindrical object 9, but the object 9 does not need to have a bottom as long as it has a hollow portion P inside. In addition, the cylindrical shape is not limited to a cylindrical shape, and may be a square tube shape. The size of the foreign object 91 that can be detected by the detection unit 3 of this embodiment varies depending on the distance between the first induction member 20 and the second induction member 30, the configuration of the magnetic sensor 10, the material of the foreign object 91, etc., but is in the range of 10 μm or more.

[0015] (Magnetic Sensor 10) As shown in FIG. 3(a), the magnetic sensor 10 has a rectangular planar shape. The length of one side of the magnetic sensor 10 can be, for example, in the range of 1 mm to 10 mm. In this example, the planar shape of the magnetic sensor 10 is a square with a side length of 3.6 mm. The size of the planar shape of the magnetic sensor 10 may be other values. The planar shape of the magnetic sensor 10 may also be other than rectangular.

[0016] 3(b), the magnetic sensor 10 has a structure in which a sensing part 12 made of a soft magnetic material (soft magnetic material layer) is laminated on a non-magnetic substrate 11. In the magnetic sensor 10 of this embodiment, the substrate 11 and the sensing part 12 are laminated in the z direction. In addition, the z direction is the thickness direction of the magnetic sensor 10. Examples of the substrate 11 include an oxide substrate such as glass or sapphire, a semiconductor substrate such as silicon, or a metal substrate such as aluminum, stainless steel, or a metal plated with nickel-phosphorus. In addition, for example, when a material having a lower electrical resistance than the sensing part 12, such as a metal substrate, is used as the substrate 11, it is preferable to provide an insulating layer that insulates the substrate 11 from the sensing part 12 on the surface of the substrate 11 on which the sensing part 12 is provided.

[0017] The sensing unit 12 includes a plurality of sensing elements 121, a connection portion 122 that connects adjacent sensing elements 121 in a zigzag manner in series, and terminal portions 123A and 123B provided at one end and the other end of the series-connected sensing elements 121.

[0018] The planar shape of the sensor element 121 is a rectangle having a long side direction and a short side direction. As shown in Fig. 3(a), the sensor element 121 has a long side direction in the y direction and a short side direction in the x direction. In this example, six sensor elements 121 are arranged in parallel in the x direction. Each sensor element 121 has a length in the longitudinal direction of 1 mm to 2 mm and a width in the lateral direction of 50 μm to 150 μm. The distance between adjacent sensor elements 121 is 50 μm to 150 μm. The above-mentioned values ​​of the length and width of the sensing element 121, the number of elements arranged in parallel, etc. are merely examples, and may be changed depending on the value of the magnetic field to be sensed, the soft magnetic material used, etc.

[0019] Each sensing element 121 is provided with uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, for example, in a short-side direction perpendicular to the longitudinal direction. The direction intersecting the longitudinal direction may have an angle of more than 45° with respect to the longitudinal direction. This allows the sensing element 121 to exhibit a magneto-impedance effect. In other words, the sensing element 121 is a magneto-impedance effect element. Further, a bias magnetic field Hb of a predetermined magnitude is applied to each sensing element 121 by a first magnet 61 and a second magnet 62, which will be described later.

[0020] The connection parts 122 are provided between the ends of adjacent sensory elements 121, and connect the adjacent sensory elements 121 in series in a zigzag manner. In the sensory unit 12 shown in FIG. 3(a), six sensory elements 121 are arranged in parallel, and therefore there are five connection parts 122. The number of connection parts 122 varies depending on the number of sensory elements 121. For example, if there are three sensory elements 121, there are two connection parts 122.

[0021] The terminal parts 123A and 123B are provided at the ends of the sensing elements 121 that are not connected by the connection parts 122. The terminal parts 123A and 123B may be of any size as long as they can be connected to electric wires or the like. In the sensing part 12 of this embodiment, since there are six sensing elements 121, the two terminal parts 123A and 123B are both provided on the upper side in FIG. 3(a). When the number of sensing elements 121 is an odd number, the two terminal parts 123A and 123B may be provided separately, one above the other.

[0022] The sensing element 121, the connection part 122 and the terminal parts 123A and 123B of the sensing part 12 are made of a soft magnetic material. A soft magnetic material is a material that is easily magnetized by a magnetic field, but quickly returns to a state where there is no magnetization or where the magnetization is small when the magnetic field is removed, and has a so-called small coercive force. As the soft magnetic material constituting the sensing element 121, the connection part 122 and the terminal parts 123A and 123B of the sensing part 12, it is preferable to use an amorphous alloy (hereinafter referred to as the Co alloy constituting the sensing part 12) in which high melting point metals such as Nb, Ta and W are added to an alloy mainly composed of Co. Examples of the Co alloy constituting the sensing part 12 include CoNbZr, CoFeTa and CoWZr. Such a Co alloy constituting the sensing part 12 can be formed by, for example, a sputtering method.

[0023] The sensing element 121, the connection part 122 and the terminal parts 123A, 123B of the sensing part 12 are integrally formed from a single layer of soft magnetic material. Since the soft magnetic material is conductive, it is possible to pass a current from one of the terminal parts 123A, 123B to the other of the terminal parts 123A, 123B. One or both of the connection portion 122 and the terminal portions 123A and 123B may be made of a conductor. Examples of the conductor that constitutes the connection portion 122 and the terminal portions 123A and 123B include Ag, Cu, Au, and Al. Also, the connection portion 122 and the terminal portions 123A and 123B may be made of different conductors.

[0024] (First guide member 20, second guide member 30) The first guide member 20 has a rectangular planar shape having a longitudinal direction and a lateral direction. The first guide member 20 has a longitudinal direction in the x direction and a lateral direction in the y direction. The first guide member 20 has a constant thickness in the z direction that is determined in advance. The thickness of the first guide member 20 in the z direction can be in the range of 1 mm to 5 mm. Furthermore, the length of the first induction member 20 in the x direction is longer than the length of the magnetic sensor 10 in the x direction. The length of the first induction member 20 in the x direction is preferably equal to or longer than the length of the hollow portion P in the object 9 in the x direction. The length of the first induction member 20 in the x direction varies depending on the size of the object 9, etc., but can be in the range of 2 to 50 times the length of the magnetic sensor 10 in the x direction. In this example, the length of the first induction member 20 in the x direction is 19 mm. Furthermore, the width of the first guide member 20 in the y direction is, for example, 1 mm. These values ​​of the first guide member 20 are merely examples, and other values ​​may be used.

[0025] As described above, the first induction member 20 is provided on the upstream side of the magnetic sensor 10 in the y direction. Specifically, the first induction member 20 is disposed so as to face the upstream side of the magnetic sensor 10 in the y direction, and extend from the portion facing the magnetic sensor 10 toward the downstream side in the x direction. In addition, the upstream end of the first induction member 20 in the x direction faces the upstream end of the sensing element 121 provided in the magnetic sensor 10 in the y direction. In this example, the upstream end of the first induction member 20 in the x direction faces the magnetic sensor 10 with a gap of 0.2 mm therebetween. The upstream end of the first induction member 20 in the x direction and the magnetic sensor 10 may be in contact with each other.

[0026] The second guide member 30 has a planar shape similar to that of the first guide member 20. That is, the planar shape of the second guide member 30 is a rectangle having a longitudinal direction and a lateral direction. The second guide member 30 has a longitudinal direction in the x direction and a lateral direction in the y direction. The second guide member 30 has a constant thickness in the z direction that is determined in advance. The thickness of the second guide member 30 in the z direction can be in the range of 1 mm to 5 mm. Similarly to the first induction member 20, the length in the x direction of the second induction member 30 is longer than the length in the x direction of the magnetic sensor 10. The length in the x direction of the second induction member 30 is preferably equal to or greater than the length in the x direction of the hollow portion P in the target object 9. The length in the x direction of the second induction member 30 can be in the range of 2 to 50 times the length in the x direction of the magnetic sensor 10. The length in the x direction of the second induction member 30 is, for example, 19 mm. Furthermore, the width of the second guide member 30 in the y direction is, for example, 1 mm. These values ​​of the second guide member 30 are merely examples, and other values ​​may be used.

[0027] The second induction member 30 is provided downstream in the y direction with respect to the magnetic sensor 10. Specifically, the second induction member 30 is disposed so as to face an end portion of the magnetic sensor 10 on the downstream side in the y direction and extend from a portion facing the magnetic sensor 10 toward the downstream side in the x direction. In addition, the upstream end of the second induction member 30 in the x direction faces the downstream end of the sensing element 121 provided in the magnetic sensor 10 in the y direction. In this example, the upstream end of the second induction member 30 in the x direction faces the magnetic sensor 10 with a gap of 0.2 mm therebetween. The upstream end of the second induction member 30 in the x direction and the magnetic sensor 10 may be in contact with each other.

[0028] The first and second guide members 20 and 30 face each other in the y direction, with their downstream portions in the x direction not facing the magnetic sensor 10 sandwiching a gap S extending in the x direction therebetween. In the detection unit 3 of this embodiment, the second guide member 30 is inserted into a hollow portion P of an object 9 that is a detection target for a foreign object 91, so that the object 9 is placed in the gap S formed between the first guide member 20 and the second guide member 30. In a state in which the second guide member 30 is inserted into the hollow portion P of the object 9, the first guide member 20 faces the object 9 placed in the gap S from the upstream side in the y direction, and the second guide member 30 faces the object 9 placed in the gap S from the downstream side in the y direction. The distance between the first guide member 20 and the second guide member 30 along the y direction (i.e., the length of the gap S in the y direction) is, for example, 4 mm. Although details will be described later, the distance between the first guide member 20 and the second guide member 30 is determined according to the thickness of the object 9 and the like so that the distance between the first guide member 20 and the second guide member 30 and the object 9 falls within a predetermined range.

[0029] The first induction member 20 and the second induction member 30 are made of a soft magnetic material. Here, the first induction member 20 and the second induction member 30 are made of ferrite, for example. An example of such ferrite is MnZn, with an initial permeability of 2500±25 and a saturation magnetic flux density Bs of 420 mT.

[0030] The first induction member 20 and the second induction member 30 induce magnetic field lines toward the sensing element 121 of the magnetic sensor 10. Specifically, in this embodiment, when a foreign object 91 is present in the target object 9 placed in the gap S, the first induction member 20 induces magnetic field lines from the foreign object 91 toward the sensing element 121 of the magnetic sensor 10. In addition, the second induction member 30 induces magnetic field lines that have passed through the sensing element 121 of the magnetic sensor 10 toward the foreign object 91. In this embodiment, the first induction member 20 and the second induction member 30 are an example of an induction member that induces magnetic lines of force to the magnetic sensor 10 or the sensing element 121. Note that the induction of magnetic lines of force by the first induction member 20 and the second induction member 30 will be described in more detail later.

[0031] (First magnet 61, second magnet 62) The first magnet 61 and the second magnet 62 apply a predetermined bias magnetic field Hb to the sensing element 121 of the magnetic sensor . The first magnet 61 and the second magnet 62 are made of permanent magnets such as neodymium magnets, ferrite magnets, etc. Here, a permanent magnet is a material that generates magnetization without receiving a magnetic field or current from an external source. The magnetic flux density of the permanent magnets constituting the first magnet 61 and the second magnet 62 varies depending on the magnitude of the bias magnetic field Hb applied to the sensing element 121, and can be, for example, about 20 mT to 500 mT.

[0032] The first magnet 61 is disposed at an end portion on the upstream side in the x direction of the first induction member 20 so as to contact a surface on the opposite side to the side facing the magnetic sensor 10. In other words, the first magnet 61 is disposed at an end portion on the upstream side in the x direction of the first induction member 20 so as to contact a surface on the upstream side in the y direction. Moreover, the first magnet 61 is disposed so that the N pole is in contact with the first induction member 20. In addition, the N pole of the first magnet 61 faces the magnetic sensor 10 with the first induction member 20 interposed therebetween.

[0033] The second magnet 62 is disposed at an end portion on the upstream side in the x direction of the second induction member 30 so as to contact a surface on the opposite side to the side facing the magnetic sensor 10. In other words, the second magnet 62 is disposed at an end portion on the upstream side in the x direction of the second induction member 30 so as to contact a surface on the downstream side in the y direction. The second magnet 62 faces the magnetic sensor 10 in the y direction, with the second induction member 30 in between. Moreover, the second magnet 62 is disposed so that its S pole is in contact with the second induction member 30. In addition, the second magnet 62 has its S pole facing the magnetic sensor 10 with the second induction member 30 interposed therebetween.

[0034] As described above, in the detection unit 3 of this embodiment, the N pole of the first magnet 61 and the S pole of the second magnet 62 face each other in the y direction via the first induction member 20, the magnetic sensor 10, and the second induction member 30. In the detection unit 3, magnetic field lines are generated that run from the north pole to the south pole of the first magnet 61 and the second magnet 62. This causes a predetermined bias magnetic field Hb to be applied to the sensing element 121 of the magnetic sensor 10. In addition, in the detection unit 3, a bias magnetic field Hb that runs toward the downstream side in the y direction (i.e., the longitudinal direction of the sensing element 121) is applied to the sensing element 121 of the magnetic sensor 10.

[0035] (Function of detection unit 3) Next, the operation of the detection unit 3 will be described. 4 is a diagram showing the relationship between the magnetic field applied in the longitudinal direction (y direction) of the sensing element 121 of the magnetic sensor 10 in the detection unit 3 and the impedance Z of the magnetic sensor 10. In Fig. 4, the horizontal axis represents the magnetic field H, and the vertical axis represents the impedance Z. The impedance Z of the magnetic sensor 10 is measured by passing a high-frequency current between the two terminals 123A, 123B of the sensing unit 12.

[0036] 4, the impedance Z of the magnetic sensor 10 increases and decreases as the magnetic field H applied in the longitudinal direction of the sensing element 121 increases. Also, the amount of change in the impedance Z with respect to the change in the magnetic field H (i.e., the slope of the graph) differs depending on the magnitude of the magnetic field H. Therefore, by using the portion where the change ΔZ in impedance Z is steep relative to the change ΔH in the applied magnetic field H (i.e., the portion where ΔZ / ΔH is large), it is possible to extract a weak change in the magnetic field H as the change ΔZ in impedance Z. In Fig. 4, the magnetic field H where the change ΔZ in impedance (ΔZ / ΔH) relative to the change ΔH in the magnetic field H is the largest in the region where the magnetic field H is positive is shown as magnetic field Hb.

[0037] In this way, the detection unit 3 of this embodiment can measure the amount of change ΔH of the magnetic field H in the vicinity of the magnetic field Hb with high accuracy. Therefore, in the detection unit 3 of this embodiment, as described above, the first magnet 61 and the second magnet 62 are used to apply a magnetic field Hb (sometimes referred to as a bias magnetic field Hb) as a bias magnetic field to the sensing element 121 of the magnetic sensor 10.

[0038] (Magnetization direction by magnetizing part 2) As described above, in the foreign object detection system 1 of this embodiment, the detection unit 3 detects the foreign object 91 contained in the target object 9 present in the gap S between the first guide member 20 and the second guide member 30. The magnetization unit 2 magnetizes the foreign object 91 contained in the object 9 in a direction in which the first induction member 20 and the second induction member 30 face each other when one of the first induction member 20 and the second induction member 30 is inserted into the hollow portion P of the object 9 (i.e., the y direction). In this example, the magnetization unit 2 magnetizes the foreign object 91 contained in the object 9 in the radial direction of the object 9. In addition, the magnetization unit 2 magnetizes the foreign object 91 contained in the object 9 by positioning the object 9 such that magnetic field lines generated between the permanent magnet 2A (see FIG. 1) and the permanent magnet 2B (see FIG. 1) cross the object 9 in the radial direction.

[0039] (Detection of foreign matter 91 by detection unit 3) Next, the operation of the detection unit 3 when detecting the foreign matter 91 contained in the target object 9 will be described with reference to FIG. When a foreign object 91 is present in the target object 9, magnetic field lines are generated from the foreign object 91 magnetized by the magnetization unit 2. As described above, in this embodiment, the foreign object 91 is magnetized in the y direction in which the first induction member 20 and the second induction member 30 face each other. Therefore, magnetic field lines are generated from the foreign object 91 toward the y direction (the upstream side of the y direction in this example).

[0040] The magnetic field lines emerging from the foreign object 91 toward the upstream side in the y direction enter the first induction member 20 and proceed along the first induction member 20 toward the upstream side in the x direction. The magnetic field lines that reach the opposing portion between the first induction member 20 and the magnetic sensor 10 pass through the magnetic sensor 10. The magnetic field lines that have passed through the magnetic sensor 10 enter the second induction member 30 and proceed along the second induction member 30 toward the downstream side in the x direction, returning to the foreign object 91. In this manner, in the detection unit 3 of this embodiment, the first induction member 20 and the second induction member 30 form a path of magnetic field lines that exits from the foreign object 91, passes through the first induction member 20, the magnetic sensor 10, and the second induction member 30, and returns to the foreign object 91. In other words, in the detection unit 3 of this embodiment, the magnetic field lines that exit from the foreign object 91 are induced toward the magnetic sensor 10 by the first induction member 20 and the second induction member 30.

[0041] In the detection unit 3, the magnetic field H applied to the sensing element 121 (see Figure 3(a)) of the magnetic sensor 10 changes due to the magnetic field lines from the foreign object 91 induced by the first induction member 20 and the second induction member 30, and the impedance Z of the sensing unit 12 (see Figure 3(a)) changes. In the foreign object detection system 1 of this embodiment, the presence of a foreign object 91 contained in the target 9 can be detected based on a change in impedance Z of the sensitive portion 12 in the magnetic sensor 10 of the detection unit 3.

[0042] Incidentally, when detecting a foreign object 91 on an object 9 using the magnetic sensor 10, there are cases in which the object 9 is directly opposed to the magnetic sensor 10 without using the first induction member 20 and the second induction member 30 in the detection unit 3 of this embodiment. 5(a)-(b) are diagrams for explaining a mode in which a foreign object 91 of a target object 9 is detected by a magnetic sensor 10 without using a first guiding member 20 and a second guiding member 30. The magnetic sensor 10 shown in FIG. 5(a)-(b) has a configuration similar to that of the magnetic sensor 10 of the present embodiment shown in FIG. 2 and FIG. 3(a)-(b). Similarly to the magnetic sensor 10 in the detection unit 3 of the present embodiment, the magnetic sensor 10 shown in FIG. 5(a)-(b) is arranged such that the longitudinal direction of a sensing element 121 (see FIG. 3(a)) is the y direction and the x direction is the lateral direction. In addition, in the magnetic sensor 10, a predetermined bias magnetic field Hb is applied to the sensing element 121 (see FIG. 3(a)) by a permanent magnet (not shown) or the like. Furthermore, in the example shown in FIGS. 5(a) and 5(b), it is assumed that foreign matter 91 contained in the target object 9 is magnetized in the y direction.

[0043] In the example shown in FIG. 5(a), the target object 9 is placed downstream of the magnetic sensor 10 in the x direction. In the example shown in FIG. 5(b), the target object 9 is placed upstream of the magnetic sensor 10 in the y direction. 5(a)-(b), magnetic field lines generated from foreign object 91 toward the y direction (upstream in the y direction in this example) pass through magnetic sensor 10 and then return to foreign object 91. Then, the magnetic field H applied to sensing element 121 of magnetic sensor 10 changes due to the magnetic field lines from foreign object 91, and the impedance Z of sensing part 12 (see FIG. 3(a)) changes. In magnetic sensor 10 of FIGS. 5(a)-(b), too, the presence of foreign object 91 included in target object 9 can be detected by the change in impedance Z of sensing part 12.

[0044] Here, the density of the magnetic field lines emanating from the foreign object 91 is higher the closer to the foreign object 91, and is lower the farther away from the foreign object 91. As shown in Figures 5(a) and (b), when the object 9 is faced to the magnetic sensor 10 to detect the foreign object 91 contained in the object 9, if the distance between the magnetic sensor 10 and the foreign object 91 is small, the magnetic field lines emanating from the foreign object 91 are easily induced to the magnetic sensor 10, and the detection accuracy of the foreign object 91 is unlikely to decrease. On the other hand, if the distance between the magnetic sensor 10 and the foreign object 91 is large, the magnetic field lines emanating from the foreign object 91 are unlikely to be induced to the magnetic sensor 10, and the detection accuracy of the foreign object 91 is likely to decrease.

[0045] Furthermore, when the object 9 has a long shape such as a cylinder, if a magnetic sensor 10 that does not have the first guiding member 20 and the second guiding member 30 (see FIG. 2 ) is used, it is difficult to detect a foreign object 91 contained in the object 9 in a short time using one magnetic sensor 10. That is, in order to detect a foreign object 91 in an object 9 that has a long shape such as a cylinder, it is necessary, for example, to move the magnetic sensor 10 along the length direction (x direction) of the object 9 or to arrange a plurality of magnetic sensors 10 side by side in the length direction (x direction) of the object 9.

[0046] Furthermore, when detecting a foreign object 91 contained in an object 9 using a magnetic sensor 10, a detection unit (hereinafter referred to as detection unit 300) may be used that includes a focusing member 41 that focuses magnetic lines of force from external space on the magnetic sensor 10 and a dissipation member 42 that dissipates magnetic lines of force that have passed through the magnetic sensor 10 into external space, instead of the first guiding member 20 and the second guiding member 30 in the detection unit 3 of this embodiment. Fig. 6 is a diagram for explaining an example of the configuration of a conventional detection unit 300. In Fig. 6, similarly to Fig. 2, the left-right direction (direction going from left to right) of the paper surface is represented as the x-direction, the up-down direction (direction going from bottom to top) of the paper surface is represented as the y-direction, and the depth direction (direction going from front to back) of the paper surface is represented as the z-direction. Also, in Fig. 6, magnetic field lines generated from a foreign object 91 included in the target object 9 are indicated by arrows. Note that in Fig. 6, the same reference numerals are used for the same configuration as the detection unit 3 shown in Fig. 2, and detailed description thereof will be omitted here.

[0047] 6 includes a magnetic sensor 10, a focusing member 41, and a diverging member 42. In the detection unit 300, the focusing member 41, the magnetic sensor 10, and the diverging member 42 are arranged in this order in the y direction. The magnetic sensor 10 has a configuration similar to that shown in FIG. 3(a), and in the detection section 300 as well, the sensing element 121 is arranged so that the longitudinal direction is the y direction and the lateral direction is the x direction.

[0048] The focusing member 41 has a facing portion 411 facing the sensing element 50, and a wide portion 412 that is wider in the x direction than the facing portion 411. That is, the focusing member 41 has a T-shape in plan view with the facing portion 411 as a vertical bar and the wide portion 412 as a horizontal bar. The diverging member 42 has a facing portion 421 facing the sensing element 50, and a wide portion 422 that is wider in the x direction than the facing portion 421. That is, the diverging member 42 has a T-shaped planar shape, similar to the focusing member 41. In detection unit 300, wide portion 412, opposing portion 411, magnetic sensor 10, opposing portion 421, and wide portion 422 of focusing member 41 are arranged in this order in the y direction. Focusing member 41 and diverging member 42 have the same T-shape in plan view and are arranged symmetrically in the y direction with magnetic sensor 10 in between.

[0049] Similarly to the first guide member 20 and the second guide member 30, the focusing member 41 and the diverging member 42 are made of a soft magnetic material. 6, are focused as they proceed from the wide portion 412 to the facing portion 411, and then exit from the facing portion 411. The magnetic field lines that have passed through the magnetic sensor 10 then enter the facing portion 421 of the diverging member 42. The magnetic field lines then diverge as they proceed from the facing portion 421 to the wide portion 422, and then exit from the wide portion 422 to the external space.

[0050] In the detection unit 300, similarly to the detection unit 3, a predetermined bias magnetic field Hb is applied to the sensing element 121 (see FIG. 3(a)) of the magnetic sensor 10 by a permanent magnet or the like (not shown).

[0051] 6, a case will be considered in which the detection unit 300 detects a foreign object 91 of the target 9 arranged upstream in the y direction with respect to the wide portion 412 of the focusing member 41. Note that in this example as well, the foreign object 91 of the target 9 is assumed to be magnetized in the y direction. As shown in FIG. 6, the magnetic field lines generated from the foreign object 91 enter the wide portion 412 of the focusing member 41, pass from the wide portion 412 to the facing portion 411, and then pass through the magnetic sensor 10. The magnetic field lines that have passed through the magnetic sensor 10 enter the facing portion 421 of the diverting member 42 and exit from the wide portion 422 to the external space. The magnetic field lines that exit from the wide portion 422 to the external space proceed upstream in the y direction through the external space and return to the foreign object 91. In this way, in the detection unit 300, the path of the magnetic field lines that leave the foreign object 91, pass through the magnetic sensor 10, and return to the foreign object 91 passes through the external space. For this reason, in the detection unit 300, the magnetic resistance is likely to be large when detecting the foreign object 91. In addition, in the detection unit 300, as shown in FIG. 6, some of the magnetic field lines generated from the foreign object 91 may enter the wide portion 412 of the focusing member 41 and then return directly to the foreign object 91 without passing through the magnetic sensor 10.

[0052] As a result, when attempting to detect a minute foreign object 91 using the detection unit 300, the number of magnetic field lines emanating from the foreign object 91 and induced to the magnetic sensor 10 is likely to be reduced. In this case, there is a risk that the detection accuracy of the detection unit 300 for the foreign object 91 will decrease.

[0053] 6, it is difficult to detect a foreign object 91 contained in the object 9 in a short time using one detection unit 300, as in the example shown in FIGS. 5(a)-(b). That is, in order to detect a foreign object 91 in an object 9 having a long shape such as a cylinder, it is necessary to move the detection unit 300 along the length of the object 9 or to arrange a plurality of detection units 300 side by side along the length of the object 9, for example.

[0054] (Effects of the first guide member 20 and the second guide member 30) In contrast, in the detection unit 3 of this embodiment, as described above, one of the first induction member 20 and the second induction member 30 is inserted into the hollow portion P of the object 9, and the object 9 to be detected for the foreign object 91 is placed in the gap S between the first induction member 20 and the second induction member 30, making it easier to induce the magnetic field lines emitted from the foreign object 91 to the magnetic sensor 10, thereby improving the detection accuracy of the foreign object 91. The effects of the first guide member 20 and the second guide member 30 of the detection unit 3 will be described in more detail below.

[0055] 7 is a diagram illustrating the magnitude of the magnetic field strength of the first induction member 20, the second induction member 30, and the magnetic sensor 10 when a foreign object 91 made of a magnetic material is present in the gap S between the first induction member 20 and the second induction member 30 in the detection unit 3 of this embodiment. In FIG. 7, the magnetic field strength of the first induction member 20, the second induction member 30, and the magnetic sensor 10 is 35×10 -6 The range above T is indicated by hatching. FIG. 7 was obtained by computer simulation.

[0056] In the simulation shown in Fig. 7, in the detection unit 3 of this embodiment having the shape shown in Fig. 2, the shape of the magnetic sensor 10 was a square of 3.6 mm x 3.6 mm, and the thickness in the z direction was 2 mm. The first induction member 20 and the second induction member 30 had a length in the x direction of 19 mm, a length in the y direction of 1 mm, and a thickness in the z direction of 3 mm. Furthermore, the distance between the first induction member 20 and the second induction member 30 in the y direction was 4 mm. Furthermore, the magnetic permeability of the magnetic sensor 10, the first induction member 20 and the second induction member 30 was set to 2200.

[0057] Moreover, the foreign object 91 present in the gap S has a spherical shape with a diameter of 100 μm and a magnetic field of 1 T directed in the y direction. Moreover, in the gap S, the distance in the x direction between the magnetic sensor 10 and the foreign object 91 is 11 mm, and the distance in the y direction between the first induction member 20 and the foreign object 91, and the distance in the y direction between the second induction member 30 and the foreign object 91 are 2 mm. In the description of this embodiment, the distance from the foreign object 91 means the distance between the surface of each member constituting the detection unit 3 and the center of the spherical foreign object 91.

[0058] As shown in FIG. 7, it was confirmed that in the detection unit 3, when a foreign object 91 made of a magnetic material is present in the gap S between the first induction member 20 and the second induction member 30, the magnetic field of the magnetized foreign object 91 increases the magnetic field strength of the magnetic sensor 10. In the example shown in FIG. 7, the average value of the magnetic field strength in the y direction in the magnetic sensor 10 was 18.4 nT.

[0059] 7 was also performed on the magnetic sensor 10 shown in FIGS. 5(a)-(b). The shape and magnetic permeability of the magnetic sensor 10, the shape of the foreign object 91, and the strength of the magnetic field of the foreign object 91 were the same as those in the simulation of FIG. In addition, in FIG. 5(a), the distance in the x direction between the magnetic sensor 10 and the foreign object 91 was set to 2 mm, and in FIG. 5(b), the distance in the y direction between the magnetic sensor 10 and the foreign object 91 was set to 2 mm. As a result of the simulation, the average value of the magnetic field strength in the y direction of the magnetic sensor 10 shown in Fig. 5(a) was 10.7 nT, and the average value of the magnetic field strength in the y direction of the magnetic sensor 10 shown in Fig. 5(b) was 15.8 nT.

[0060] 7 was also performed on the detection unit 300 shown in Fig. 6. The shape and magnetic permeability of the magnetic sensor 10 in the detection unit 300, the shape of the foreign object 91, and the strength of the magnetic field of the foreign object 91 were the same as those in the simulation of Fig. 7. 6, the width in the x direction of facing portion 411 of focusing member 41 and the length in the y direction of facing portion 421 of diverging member 42 are 3.7 mm and 4.5 mm, respectively. The length in the x direction of wide portion 412 of focusing member 41 and wide portion 422 of diverging member 42 are 13 mm and 2 mm, respectively. The distance in the y direction between wide portion 412 of focusing member 41 and foreign object 91 is 2 mm. As a result of the simulation, in the detection section 300 shown in FIG. 6, the average value of the magnetic field strength in the y direction in the magnetic sensor 10 was 4.4 nT.

[0061] In this way, it was confirmed that in the detection unit 3 of this embodiment, the magnetic field strength in the magnetic sensor 10 is higher than when the foreign object 91 is detected by the magnetic sensor 10 that does not have the first guide member 20 and the second guide member 30 as shown in Figures 5(a)-(b). In addition, it was confirmed that in the detection unit 3 of this embodiment, the magnetic field strength in the magnetic sensor 10 is higher even when the distance between the magnetic sensor 10 and the foreign object 91 is larger than in the example shown in Figures 5(a)-(b). Furthermore, in the detection unit 3 of this embodiment, it was confirmed that the magnetic field strength in the magnetic sensor 10 is higher than when foreign object 91 is detected using the detection unit 300 of Figure 6, which has a focusing member 41 and a diverging member 42 having different shapes from the first induction member 20 and the second induction member 30 instead of the first induction member 20 and the second induction member 30.

[0062] (Regarding the distance in the x direction between the magnetic sensor 10 and the foreign object 91) Next, the relationship between the distance in the x direction between the magnetic sensor 10 in the detection unit 3 and the foreign object 91 and the detection accuracy of the foreign object by the detection unit 3 will be described. Fig. 8 is a diagram showing the average value of the magnetic field strength in the y direction in the magnetic sensor 10 when the distance in the x direction between the magnetic sensor 10 and a foreign object 91 is changed in the detection unit 3 of this embodiment. The average value of the magnetic field strength of the magnetic sensor 10 shown in Fig. 8 was obtained by a simulation similar to that shown in Fig. 7. In addition, the conditions of the detection unit 3 and the foreign object 91, except for the conditions described below, were the same as those in the simulation shown in Fig. 7.

[0063] 8, the foreign object 91 was placed at the center in the y direction in the gap S. In this case, the distance in the y direction between the first guide member 20 and the foreign object 91 and the distance in the y direction between the second guide member 30 and the foreign object 91 were 2 mm. 8, the position of the foreign object 91 in the gap S was shifted in the x direction to change the distance in the x direction between the magnetic sensor 10 and the foreign object 91. Here, the distance in the x direction between the magnetic sensor 10 and the foreign object 91 means the distance along the x direction from the end of the magnetic sensor 10 on the downstream side in the x direction to the center of the foreign object 91. In addition, in FIG. 8, the partial positions indicated by dashed lines correspond to the downstream ends of the first guide member 20 and the second guide member 30 in the x direction.

[0064] As shown in FIG. 8, in the detection unit 3 of this embodiment, it has been confirmed that when a foreign object 91 is present in the gap S between the first induction member 20 and the second induction member 30, the magnetic field strength of the magnetic sensor 10 required to detect the foreign object 91 can be obtained even if the distance between the magnetic sensor 10 and the foreign object 91 changes. In addition, it has been confirmed that in the detection unit 3 of this embodiment, the first guide member 20 and the second guide member 30 make it possible to increase the length in the x-direction of the detection range in which foreign objects 91 present in the target object 9 can be detected.

[0065] 8, it was confirmed that in the detection unit 3, the magnetic field strength in the magnetic sensor 10 is substantially the same when the distance between the magnetic sensor 10 and the foreign object 91 is in the range of 2.5 mm to 14 mm. In other words, it was confirmed that the detection unit 3 can detect the foreign object 91 contained in the target 9 with substantially the same detection accuracy when the distance between the magnetic sensor 10 and the foreign object 91 is in the range of 2.5 mm to 14 mm.

[0066] As described above, when the object 9 has a long shape such as a cylinder, to detect a foreign object 91 using a magnetic sensor 10 as shown in Figure 5(b), it is necessary to move the magnetic sensor 10 along the length of the object 9 or to arrange multiple magnetic sensors 10 in a line along the length of the object 9. In contrast, in this embodiment, even if the object 9 has a long shape such as a cylindrical shape, the detection unit 3 using one magnetic sensor 10 can detect foreign objects 91 over the entire length of the object 9.

[0067] [Embodiment 2] Next, a description will be given of embodiment 2 of the present invention. Note that the same components as those in embodiment 1 are designated by the same reference numerals, and detailed description thereof will be omitted here. 9(a)-(b) are schematic diagrams illustrating the configuration of the detection unit 3 to which the second embodiment is applied. Fig. 9(a) is a cross-sectional view of the detection unit 3 of the second embodiment cut in the xy plane, and Fig. 9(b) is a cross-sectional view of the detection unit 3 at part IXB-IXB shown in Fig. 9(a). In Fig. 9(a), the short side direction of the sensing element 121 (see Fig. 3(a)) in the magnetic sensor 10 is the x direction, and the long side direction is the y direction. In the detection unit 3 of the above-mentioned embodiment 1, the first induction member 20 and the second induction member 30 have a constant thickness in the z direction, and the magnetic sensor 10, the first induction member 20, and the second induction member 30 are arranged on the same plane. In contrast, the detection unit 3 of the present embodiment differs from the detection unit 3 of embodiment 1 in that the first induction member 20 and the second induction member 30 have a three-dimensional shape.

[0068] More specifically, the first induction member 20 of the present embodiment faces the magnetic sensor 10 from the upstream side in the y direction, and has a disk-shaped bottom portion 27 and a cylindrical side portion 28 extending downstream in the y direction from the periphery of the bottom portion 27. The first induction member 20 as a whole has a cylindrical shape with a bottom. The second induction member 20 faces the magnetic sensor 10 from the downstream side in the y direction, and has a cylindrical shape extending toward the downstream side in the y direction.

[0069] In the detection unit 3 of this embodiment, the inner peripheral surface of the side portion 28 of the first guide member 20 and the outer peripheral surface of the second guide member 30 face each other via a gap S. More specifically, the inner peripheral surface of the side portion 28 of the first guide member 20 and the outer peripheral surface of the second guide member 30 face each other in the circumferential direction with the y direction as the axis via the gap S. In other words, the inner peripheral surface of the side portion 28 of the first guide member 20 and the outer peripheral surface of the second guide member 30 face each other in a plurality of directions perpendicular to the y direction via the gap S. In addition, in the detection unit 3 of this embodiment, the gap S is cylindrical with the y direction as the axis. In the detection unit 3 of this embodiment, the second guide member 30 is inserted into the hollow portion P of the target object 9. Then, the detection unit 3 detects a foreign object 91 contained in the target object 9 and present in the gap S between the side portion 28 of the first guide member 20 and the second guide member 30.

[0070] Furthermore, when the detection unit 3 of this embodiment is used, the magnetization unit 2 magnetizes the object 9 in a direction perpendicular to the y direction (e.g., the x direction), which is the direction in which the first induction member 20 and the second induction member 30 face each other when the second induction member 30 is inserted into the hollow portion P of the object 9.

[0071] As a result, in the detection unit 3 of this embodiment, the magnetic field lines emerging from the foreign object 91 toward the downstream side in the x-direction enter the side portion 28 of the first induction member 20, proceed along the side portion 28 and the bottom portion 27, and then pass through the magnetic sensor 10. The magnetic field lines that have passed through the magnetic sensor 10 enter the second induction member 30 and return to the foreign object 91. In this way, in the detection unit 3 of this embodiment, the first induction member 20 and the second induction member 30 form a path for magnetic lines of force that exit from the foreign object 91, pass through the first induction member 20, the magnetic sensor 10 and the second induction member 30, and return to the foreign object 91.

[0072] In the detection unit 3 of this embodiment, as in embodiment 1, the magnetic field H applied to the sensing element 121 (see Figure 3(a)) of the magnetic sensor 10 changes due to the magnetic field lines from the foreign object 91 induced by the first induction member 20 and the second induction member 30, and the impedance Z of the sensing unit 12 (see Figure 3(a)) changes. The foreign object detection system 1 (see FIG. 1) can detect the presence of a foreign object 91 contained in the target object 9 based on a change in impedance Z of the sensing part 12 in the magnetic sensor 10 of the detection unit 3.

[0073] 10 is a diagram illustrating the magnitude of the magnetic field strength of the first induction member 20, the second induction member 30, and the magnetic sensor 10 when a foreign object 91 made of a magnetic material is present in the gap S between the side portion 28 of the first induction member 20 and the second induction member 30 in the detection unit 3 of this embodiment. In FIG. 10, the magnetic field strength of the first induction member 20, the second induction member 30, and the magnetic sensor 10 is 25×10 -6 The range above T is indicated by hatching. Fig. 10 was obtained by a simulation similar to that of Fig. 7. In addition, in the simulation of Fig. 10, the conditions of the detection unit 3 and the foreign object 91, except for the conditions described below, were the same as those in the simulation described in Fig. 7.

[0074] In the detection unit 3 used in the simulation of Fig. 10, the diameter of the bottom portion 27 of the first guide member 20 was 16 mm, and the thickness in the y direction was 2 mm. The length in the y direction of the side portion 28 of the first guide member 20 was 19 mm, and the thickness was 2 mm. Furthermore, the diameter of the cylindrical second guide member 30 was 4 mm. In this case, the distance between the inner peripheral surface of the side portion 28 of the first guide member 20 and the outer peripheral surface of the second guide member 30 was 4 mm. Moreover, the foreign object 91 present in the gap S was a sphere having a diameter of 100 μm and having a magnetic field of 1 T facing in the x direction. Moreover, in the gap S, the distance in the y direction between the magnetic sensor 10 and the foreign object 91 was 11 mm, and the distance in the x direction between the first induction member 20 and the foreign object 91, and the distance in the x direction between the second induction member 30 and the foreign object 91 were both 2 mm.

[0075] As shown in FIG. 10, in the detection unit 3, when a foreign object 91 made of a magnetic material is present in the gap S between the side portion 28 of the first induction member 20 and the second induction member 30, it was confirmed that the magnetic field strength of the magnetic sensor 10 increases due to the magnetic field of the magnetized foreign object 91. In the example shown in FIG. 10, the average value of the magnetic field strength in the y direction in the magnetic sensor 10 was 12.3 nT.

[0076] Although the embodiment and examples of the present invention have been described above, the present invention is not limited to the embodiment. Various modifications and combinations may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0077] Reference Signs List 1...foreign object detection system, 2...magnetized portion, 3...detection portion, 9...target object, 10...magnetic sensor, 20...first induction member, 30...second induction member, 61...first magnet, 62...second magnet, 91...foreign object, S...gap, 121...sensing element

Claims

1. a magnetic sensor including a sensing element that includes a soft magnetic material, has a longitudinal direction and a lateral direction, has uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and senses a magnetic field by a magneto-impedance effect; a first induction member that faces one end of the magnetic sensor in the longitudinal direction, extends in a direction away from the one end, and induces magnetic lines of force in the sensing element of the magnetic sensor; a second induction member that faces the other end of the magnetic sensor in the longitudinal direction, extends in a direction away from the other end while facing the first induction member with a gap therebetween, and induces magnetic lines of force to the sensing element of the magnetic sensor together with the first induction member; Equipped with A detection device that detects a magnetic body contained in a cylindrical object by inserting one of the first induction member and the second induction member into the hollow portion of the cylindrical object having a hollow portion.

2. The detection device according to claim 1 , wherein the first guide member and the second guide member face each other in a plurality of directions with the gap therebetween.

3. The detection device according to claim 1 , further comprising a magnetizing unit that magnetizes the magnetic body in a radial direction of the object.

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