Detection device and magnetic sensor

Abstract

To increase output signal strength when detecting foreign matter on the basis of a signal output from a sensing element configured to sense a magnetic field through the magnetic impedance effect.SOLUTION: A detection device is provided, comprising a sensing element containing a soft magnetic material, having a longitudinal direction and lateral direction, exhibiting uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, the sensing element being configured to sense a magnetic field through the magnetic impedance effect; first and second guiding members provided to face each other in the longitudinal direction with the sensing element in between to guide magnetic field lines to the sensing element; and an application member for applying a bias magnetic field to the sensing element. The detection device detects foreign matter present on a side opposite the sensing element with respect to the first guiding member, and the printing member is provided on a side opposite the sensing element with respect to the first guiding member.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a detection device and a magnetic sensor. [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 foreign objects based on a signal output from a sensing element that senses a magnetic field due to the magneto-impedance effect, it is preferable to increase the signal strength of the output signal in order to improve the accuracy of foreign object detection. An object of the present invention is to increase the strength of a signal output from a sensing element that senses a magnetic field due to the magneto-impedance effect when detecting a foreign object based on the signal output from the sensing element. [Means for solving the problem]

[0005] According to the present invention, the following inventions (1) to (5) are provided. (1) a sensing element (sensing element 50) including a soft magnetic material, having a longitudinal direction and a lateral direction, 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 41) and a second induction member (second induction member 42) that face each other in the longitudinal direction with the sensing element in between and induce magnetic lines of force in the sensing element; An application member (bias magnet 60) that applies a bias magnetic field to the sensing element, Detecting a foreign object present on an opposite side of the first induction member from the sensing element, The application member is provided on the opposite side of the sensing element with respect to the first induction member. Detection device. (2) detecting a foreign object made of a magnetic body magnetized in a predetermined magnetization direction; A detection device according to (1), wherein the direction in which the magnetic field lines generated by the bias magnetic field pass through the sensing element is the same as the magnetization direction. (3) The first guide member includes a facing portion (facing portion 411) facing the sensor element in the longitudinal direction, and a wide portion (wide portion 412) located on the opposite side of the sensor element from the facing portion and extending in the short direction, The detection device according to (1) or (2), wherein the application member is provided on the opposite side of the wide portion of the first induction member from the sensing element. (4) The first guide member faces one end of the sensing element in the longitudinal direction, The second guide member includes a facing portion (facing portion 423) facing the other end of the sensory element in the longitudinal direction, a wide portion (wide portion 424) located on the opposite side of the sensory element with respect to the facing portion and extending in the short direction, and an extension portion (extending portions 425, 426) extending from the end of the wide portion in the short direction in a direction from the other end in the longitudinal direction toward the one end, and another bias magnet (60G, 60H) attached to the other end of the extension of the second induction member and configured to apply a bias magnetic field to the sensing element together with the bias magnet (60F). A detection device according to (1) or (2). (5) a sensing element (sensing element 50) including a soft magnetic material, having a longitudinal direction and a transverse direction, 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 41) and a second induction member (second induction member 42) that face each other in the longitudinal direction with the sensing element in between and induce magnetic lines of force in the sensing element; an application member (bias magnet 60) that is provided on the opposite side of the sensing element with respect to the first induction member and applies a bias magnetic field to the sensing element; A magnetic sensor comprising: Effect of the Invention

[0006] According to the present invention, in a detection device that detects foreign matter based on a signal output from a sensing element that senses a magnetic field due to the magneto-impedance effect, the strength of the output signal can be increased. [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] 2 is an enlarged view of a magnetic sensor in the detection unit shown in FIG. 1. [Diagram 3] 3 is a view of the magnetic sensor shown in FIG. 2 as viewed from a direction III. [Figure 4] 1(a) and 1(b) are diagrams illustrating an example of a sensing element to which the present embodiment is applied. [Diagram 5] 1 is a diagram showing the relationship between a magnetic field applied in the longitudinal direction of a sensing part 51 in a sensing element of a magnetic sensor and the impedance of the sensing element. [Figure 6] 1A and 1B are diagrams illustrating a state in which a foreign object is detected by a magnetic sensor. [Figure 7] FIG. 1 is a diagram for explaining a conventional magnetic sensor, in which the conventional magnetic sensor is viewed from the upstream side in the z direction. [Figure 8]10 is a diagram showing the relationship between the diameter of a foreign particle and the signal-to-noise ratio (SN ratio) of an output signal for the magnetic sensor of this embodiment and a conventional magnetic sensor. [Figure 9] 5(a) and 5(b) are diagrams illustrating the relationship between the magnetization direction of a foreign object and an output signal from a magnetic sensor. [Figure 10] FIG. 11 is a diagram for explaining the configuration of a magnetic sensor to which a second embodiment is applied, showing the magnetic sensor of the second embodiment as viewed from the upstream side in the z direction. 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] 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 contained in an object 9. In the following, a case in which the foreign object 91 is made of a magnetic material will be described as an example, but as will be described later, the foreign object detection system 1 of this embodiment can also detect foreign object 91 made of a non-magnetic metal. The foreign object detection system 1 includes a moving mechanism 10 that moves an object 9 along a predetermined moving direction, a magnetizing unit 20 that magnetizes a foreign object 91 included in the object 9, and a detection unit 30 that detects the foreign object 91 magnetized by the magnetizing unit 20. In the foreign object detection system 1 of this embodiment, the magnetizing unit 20 and the detection unit 30 are arranged side by side in the direction in which the object 9 is moved by the moving mechanism 10. In this embodiment, the foreign object detection system 1 or the detection unit 30 is an example of a detection device that detects a foreign object contained in an object.

[0009] The moving mechanism 10 is configured by a so-called belt conveyor. The moving mechanism 10 includes a pair of rollers 11, 12, and a belt 15 wound around the rollers 11, 12. In the moving mechanism 10, one of the rollers 11 is driven to rotate at a predetermined rotation speed by a driving means (not shown). This causes the belt 15 to circulate in the direction of the arrow A shown in FIG. 1. The moving mechanism 10 moves the object 9 placed on the belt 15 from the left side to the right side in Fig. 1 at a predetermined moving speed by the belt 15 which moves in a circular manner. As a result, the object 9 is guided to the magnetizing unit 20 and the detection unit 30 in this order.

[0010] The moving speed of the object 9 by the moving mechanism 10 (i.e., the moving speed of the foreign object 91 contained in the object 9) varies depending on the configuration of the magnetic sensor unit 31 of the detection unit 30 described later, but can be, for example, in the range of 30 mm / sec or more and 500 mm / sec or less.

[0011] The magnetizing unit 20 magnetizes the foreign matter 91 contained in the target object 9 moved by the moving mechanism 10 . The magnetization unit 20 includes a pair of permanent magnets 21, 22 arranged opposite to each other across the belt 15 of the movement mechanism 10. When the object 9 moved by the movement mechanism 10 passes between the pair of permanent magnets 21, 22, the magnetization unit 20 magnetizes a foreign matter 91 included in the object 9. 1, a pair of permanent magnets 21, 22 are arranged such that the N pole (e.g., the N pole of permanent magnet 21) and the S pole (e.g., the S pole of permanent magnet 22) face each other across the belt 15 of the movement mechanism 10. Then, in the magnetization unit 20, magnetic field lines that cross the belt 15 in the thickness direction are generated between the permanent magnets 21 and 22. As a result, in the magnetization unit 20, the magnetic field lines pass through a foreign object 91 included in the target object 9 that is placed on the belt 15 and moved, and the foreign object 91 is magnetized. In addition, the arrangement of the permanent magnets 21 and 22 in the magnetizing unit 20 is not limited to that shown in Fig. 1 as long as the magnetizing unit 20 generates magnetic lines of force for magnetizing the foreign matter 91 included in the target object 9. In addition, electromagnets may be used instead of the permanent magnets 21 and 22.

[0012] The detection unit 30 detects a foreign object 91 contained in the target object 9 moved by the moving mechanism 10 and magnetized by the magnetizing unit 20 . The size of the foreign object 91 that can be detected by the detection unit 30 of this embodiment varies depending on the configuration of the magnetic sensor unit 31 (described later) and the material of the foreign object 91, but is in the range of 10 μm or more.

[0013] The detection unit 30 of this embodiment includes a magnetic sensor 40 that outputs an electric signal corresponding to a foreign object 91 included in the target object 9. The detection unit 30 also includes a shielding unit 33 that covers the magnetic sensor 40 and a portion of the belt 15 that faces the magnetic sensor 40 to shield from an external magnetic field. The detection unit 30 also includes a control unit 35 that controls the magnetic sensor 40.

[0014] The shielding portion 33 has a box-like shape and houses therein the magnetic sensor 40 and a part of the belt 15. In addition, the shielding portion 33 is provided with openings 331, 332 on the upstream side and downstream side in the moving direction of the belt 15 facing the magnetic sensor 40, through which the belt 15 and the object 9 placed on the belt 15 pass. The shielding portion 33 is made of a magnetic shielding material such as iron, stainless steel, etc. The shielding portion 33 shields the internal space of the shielding portion 33 and the magnetic sensor 40 and the like housed in the shielding portion 33 from an external magnetic field.

[0015] The control unit 35 determines whether or not a foreign object 91 is present on the target object 9 based on the electrical signal output from the magnetic sensor 40. The control unit 35 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).

[0016] (Configuration of magnetic sensor 40) Next, the configuration of the magnetic sensor 40 included in the detection unit 30 will be described. Fig. 2 is an enlarged view of the magnetic sensor 40 in the detection unit 30 shown in Fig. 1. In Fig. 2, the depth direction of the paper (direction from the front to the back) is indicated as the x-direction, the up-down direction of the paper (direction from bottom to top) is indicated as the y-direction, and the lateral direction of the paper (direction from left to right) is indicated as the z-direction. Fig. 3 is a view of the magnetic sensor 40 shown in Fig. 2 as seen from the direction III. In addition, Fig. 3 corresponds to a view of the magnetic sensor 40 as seen from the upstream side in the direction of movement of the target object 9 by the movement mechanism 10. Note that Fig. 3 illustrates the magnetic sensor 40 such that the up-down direction (from bottom to top) of the paper is the x-direction, the lateral direction (from left to right) of the paper is the y-direction, and the depth direction (from front to back) of the paper is the z-direction. Also, Fig. 3 shows magnetic field lines generated by a bias magnet 60, which will be described later, with arrows.

[0017] Here, in this embodiment, the case where the detection unit 30 has one magnetic sensor 40 will be described, but the detection unit 30 may have multiple magnetic sensors 40. Although not shown, for example, when the object 9 moved by the moving mechanism 10 has a shape elongated in the x direction, or when multiple objects 9 are lined up in the x direction, the multiple magnetic sensors 40 may be arranged side by side in the x direction. By adopting such a configuration, the detection unit 30 can detect a foreign object 91 included in the object 9 having a shape elongated in the x direction or a foreign object 91 included in multiple objects 9 lined up in the x direction by the multiple magnetic sensors 40.

[0018] The magnetic sensor 40 includes a sensing element 50 that senses a magnetic field by the magnetic impedance effect. The magnetic sensor 40 also includes a first induction member 41 and a second induction member 42 that induce magnetic field lines to the sensing element 50. The magnetic sensor 40 also includes a bias magnet 60 that is attached to the first induction member 41 and applies a predetermined bias magnetic field to the sensing element 50. In the magnetic sensor 40 of this embodiment, the bias magnet 60, the first induction member 41, the sensing element 50, and the second induction member 42 are arranged in this order in the y direction. The magnetic sensor 40 is disposed so that the bias magnet 60 faces the object 9 moved by the movement mechanism 10. Here, the magnetic sensor 40 refers to the area surrounded by the dashed line shown in FIG. 3, and the other area may be referred to as the external space or the outside.

[0019] (First guide member 41, second guide member 42) The first guide member 41 has a facing portion 411 facing the sensing element 50 from the upstream side in the y direction, and a wide portion 412 that is wider in the x direction than the facing portion 411. That is, the first guide 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 first guide member 41 has a predetermined constant thickness in the z direction. The thickness of the first guide member 41 in the z direction can be in the range of 1 mm to 5 mm.

[0020] In the first induction member 41, the width in the x direction of the portion of the facing portion 411 facing the sensing element 50 can be approximately the same as the width in the x direction of the sensing element 50, for example, 4.2 mm. In addition, in the first induction member 41, the length in the y direction of the facing portion 411 is, for example, 4.5 mm. Furthermore, in the first guide member 41, the width of the wide portion 412 in the x direction is, for example, 13 mm, and the length in the y direction is, for example, 2 mm. Note that these values ​​are merely examples and other values ​​may be used.

[0021] The second guide member 42 has a facing portion 421 facing the sensing element 50 from the downstream side in the y direction, and a wide portion 422 that is wider in the x direction than the facing portion 421. That is, the second guide member 42 has a T-shape in plan view with the facing portion 421 as a vertical bar and the wide portion 422 as a horizontal bar. The second guide member 42 has a predetermined constant thickness in the z direction. The thickness of the second guide member 42 in the z direction can be in the range of 1 mm or more and 5 mm or less.

[0022] In the second induction member 42, the width in the x direction of the portion of the facing portion 421 facing the sensor element 50 can be approximately the same as the width in the x direction of the sensor element 50, for example, 4.2 mm. In addition, in the second induction member 42, the length in the y direction of the facing portion 421 is, for example, 4.5 mm. Furthermore, in the second guide member 42, the width of the wide portion 422 in the x direction is, for example, 13 mm, and the length in the y direction is, for example, 2 mm. Note that these values ​​are merely examples and other values ​​may be used.

[0023] In addition, in the magnetic sensor 40, the wide portion 412, the facing portion 411, the sensing element 50, the facing portion 421, and the wide portion 422 of the first induction member 41 are arranged in this order in the y direction. The first induction member 41 and the second induction member 42 have the same T-shape in plan view and are arranged symmetrically in the y direction with the sensing element 50 in between.

[0024] 3, the facing portion 411 is provided in the center of the wide portion 412 in the x direction. However, the facing portion 411 does not have to be provided in the center of the wide portion 412, and may be provided at one end or the other end of the wide portion 412 in the x direction. That is, the first guide member 41 may have an L-shaped planar shape. The same applies to the second guide member 42. Moreover, the first guide member 41 and the second guide member 42 do not necessarily have to be symmetrical in the y direction.

[0025] The first induction member 41 and the second induction member 42 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. Here, the first induction member 41 and the second induction member 42 are made of ferrite, as an example. An example of such ferrite is MnZn, with an initial magnetic permeability of 2500±25% and a saturation magnetic flux density Bs of 420 mT. Moreover, the facing portion 411 and the wide portion 412 of the first guide member 41 are integrally formed, and the facing portion 421 and the wide portion 422 of the second guide member 42 are integrally formed.

[0026] (Sensing element 50) Next, the sensing element 50 provided in the magnetic sensor 40 will be described. Figures 4(a)-(b) are diagrams illustrating an example of the sensing element 50 to which this embodiment is applied. Figure 4(a) is a plan view of the sensing element 50, and Figure 4(b) is a cross-sectional view taken along line IVB-IVB in Figure 4(a). In Figure 4(a), the vertical direction (from bottom to top) of the paper is the x-direction, the horizontal direction (from left to right) of the paper is the y-direction, and the depth direction of the paper (from front to back) is the z-direction.

[0027] 4(b), the sensor element 50 has a structure in which a sensor circuit 500 made of a soft magnetic material (soft magnetic layer) is laminated on a non-magnetic substrate 505. In the sensor element 50 of this embodiment, the substrate 505 and the sensor circuit 500 are laminated in the z direction. In addition, the z direction is the thickness direction of the sensor element 50. The substrate 505 may be, for example, 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 sensory circuit 500, such as a metal substrate, is used as the substrate 505, it is preferable to provide an insulating layer on the surface of the substrate 505 on which the sensory circuit 500 is provided, to insulate the substrate 505 from the sensory circuit 500.

[0028] The sensing circuit 500 includes a plurality of sensing parts 51, a connection part 52 that connects adjacent sensing parts 51 in a zigzag manner in series, and terminal parts 53 provided at one end and the other end of the series-connected sensing parts 51.

[0029] The sensing part 51 has a rectangular planar shape having a long side direction and a short side direction. As shown in Fig. 4(a), the sensing part 51 has a long side direction in the y direction and a short side direction in the x direction. In this example, six sensing parts 51 are arranged in parallel in the x direction. Each of the sensitive parts 51 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 interval between adjacent sensitive parts 51 is 50 μm to 150 μm. The above-mentioned values ​​of the length and width of the sensing portion 51, the number of sensing portions 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 to be used, etc.

[0030] Each sensing part 51 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 part 51 to exhibit a magneto-impedance effect. In other words, the sensing part 51 is a magneto-impedance effect element. Further, a bias magnetic field Hb of a predetermined magnitude is applied to each of the sensing parts 51 by a bias magnet 60, the details of which will be described later.

[0031] The connection parts 52 are provided between the ends of adjacent sensing parts 51, and connect the adjacent sensing parts 51 in series in a zigzag manner. In the sensing circuit 500 shown in FIG. 4(a), six sensing parts 51 are arranged in parallel, so there are five connection parts 52. The number of connection parts 52 varies depending on the number of sensing parts 51. For example, if there are three sensing parts 51, there are two connection parts 52.

[0032] The terminal portion 53 is provided at each end of the sensing portion 51 that is not connected by the connection portion 52. The terminal portion 53 may be of any size as long as it is large enough to connect an electric wire or the like. Since the sensing circuit 500 of this embodiment has six sensing portions 51, the two terminal portions 53 are both provided on the left side in FIG. 4(a). If the number of sensing portions 51 is odd, the two terminal portions 53 may be provided separately on the left and right.

[0033] As the soft magnetic material constituting the sensing part 51, the connection part 52 and the terminal part 53 of the sensing circuit 500, it is preferable to use an amorphous alloy (hereinafter, referred to as the Co alloy constituting the sensing circuit 500) 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 circuit 500 include CoNbZr, CoFeTa and CoWZr. The Co alloy constituting such a sensing circuit 500 can be formed by, for example, a sputtering method.

[0034] The sensing part 51, the connection part 52 and the terminal part 53 of the sensing circuit 500 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 terminal part 53 to the other terminal part 53. One or both of the connection portion 52 and the terminal portion 53 may be made of a conductor. Examples of the conductor that constitutes the connection portion 52 and the terminal portion 53 include Ag, Cu, Au, and Al. Also, the connection portion 52 and the terminal portion 53 may be made of different conductors.

[0035] (Bias magnet 60) Returning to FIG. 3, the bias magnet 60 provided in the magnetic sensor 40 will be described. In the magnetic sensor 40 of this embodiment, the bias magnet 60 is provided in contact with a surface of the wide portion 412 of the first induction member 41 on the opposite side to the sensing element 50. Specifically, the bias magnet 60 is provided on the outer side of the magnetic sensor 40 than the first induction member 41 when viewed from the sensing element 50. Specifically, the bias magnet 60 is provided so as to face the outside of the magnetic sensor 40. As a result, in the detection unit 30, the bias magnet 60 faces the object 9 moved by the movement mechanism 10.

[0036] 3, five bias magnets 60A, 60B, 60C, 60D, and 60E are arranged side by side in the x direction on the surface of the wide portion 412 of the first induction member 41 opposite the sensing element 50. In this example, the five bias magnets 60A, 60B, 60C, 60D, and 60E are arranged together in the center in the x direction on the surface of the wide portion 412 opposite the sensing element 50. In this embodiment, the five bias magnets 60A, 60B, 60C, 60D, and 60E are an example of an application member that applies a bias magnetic field to the sensing element 50. In the description of this embodiment, the five bias magnets 60A, 60B, 60C, 60D, and 60E will be simply referred to as bias magnets 60 when there is no need to distinguish between them. Each bias magnet 60 is disposed so that its south pole comes into contact with the surface of the wide portion 412 of the first induction member 41 opposite to the sensing element 50 .

[0037] The bias magnet 60 is made of a permanent magnet such as a neodymium magnet or a ferrite magnet. Here, a permanent magnet is a material that generates magnetization without receiving a magnetic field or current from an outside source. The magnetic flux density of the permanent magnets that make up the bias magnet 60 varies depending on factors such as the magnitude of the bias magnetic field Hb applied to the sensing element 50, but can be in the range of 0.01 mT to 1 mT for the entire bias magnet 60 (i.e., the total of the five bias magnets 60A to 60E).

[0038] In the magnetic sensor 40, magnetic field lines are generated from the N pole to the S pole of the bias magnet 60. In the magnetic sensor 40, the magnetic field lines generated from the bias magnet 60 are induced by the first induction member 41 and the second induction member 42. As a result, a predetermined bias magnetic field Hb is applied to each sensing portion 51 of the sensing element 50. 3, the magnetic field lines generated from the bias magnet 60 exit the magnetic sensor 40 from the N pole of the bias magnet 60 toward the upstream side in the y direction. The magnetic field lines that exit the magnetic sensor 40 then travel in the x and y directions around the magnetic sensor 40, pass through the wide portion 422 and the facing portion 421 of the second induction member 42, and penetrate the sensing element 50. The magnetic field lines that have penetrated the sensing element 50 reach the S pole of the bias magnet 60 via the facing portion 411 and the wide portion 412 of the first induction member 41.

[0039] As a result, in the magnetic sensor 40, the magnetic field lines from the bias magnet 60 pass through the sensing element 50 via the first induction member 41 and the second induction member 42. More specifically, in the magnetic sensor 40, the magnetic field lines directed toward the upstream side in the y direction pass through each sensing portion 51 of the sensing element 50. As a result, in the magnetic sensor 40, a bias magnetic field Hb of a predetermined magnitude is applied to each sensing portion 51 of the sensing element 50.

[0040] Here, in the magnetic sensor 40 of this embodiment, the magnetic field lines generated from the bias magnet 60 pass through the external space of the magnetic sensor 40, more specifically, the external space of the magnetic sensor 40 located upstream in the y direction relative to the first induction member 41.

[0041] (Function of the magnetic sensor 40) Next, the operation of the magnetic sensor 40 will be described. 5 is a diagram showing the relationship between the magnetic field applied in the longitudinal direction (y direction) of the sensing part 51 of the sensing element 50 of the magnetic sensor 40 and the impedance Z of the sensing element 50. In Fig. 5, the horizontal axis represents the magnetic field H, and the vertical axis represents the impedance Z. The impedance Z of the sensing element 50 is measured by passing a high-frequency current between the two terminal parts 53.

[0042] 5, the impedance Z of the sensing element 50 increases or decreases as the absolute value of the magnetic field H increases in the positive or negative direction, with the magnetic field being zero (H=0) as the boundary. Also, the amount of change in 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. 5, the magnetic field H where the change ΔZ (ΔZ / ΔH) in impedance Z 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.

[0043] In this way, the magnetic sensor 40 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 magnetic sensor 40 of the present embodiment, the bias magnet 60 is used to apply a magnetic field Hb (sometimes referred to as a bias magnetic field Hb) to the sensing part 51 of the sensing element 50 as a bias magnetic field. When the magnetic field H sensed by the magnetic sensor 40 changes, the magnetic sensor 40 outputs an electric signal according to the amount of change ΔZ in the impedance Z accompanying the change in the magnetic field H. Hereinafter, the electric signal output from the magnetic sensor 40 may be referred to as an output signal of the magnetic sensor 40.

[0044] (Detection of foreign matter 91 by detection unit 30) Next, an operation of detecting a foreign object 91 contained in the target object 9 (see FIG. 1) by the magnetic sensor 40 of the detection unit 30 will be described. Fig. 6 is a diagram showing a state when a foreign object 91 is detected by the magnetic sensor 40. Fig. 6 corresponds to a view of the magnetic sensor 40 as seen from the upstream side in the z direction. In Fig. 6, some of the magnetic field lines generated by the bias magnet 60 shown in Fig. 3 are indicated by arrows. As described above, in the detection unit 30 of this embodiment, the bias magnet 60 of the magnetic sensor 40 is provided to face the object 9 moved by the moving mechanism 10 (see FIG. 1). As a result, when the object 9 includes a foreign object 91, as shown in FIG. 6, the magnetic field lines extending from the bias magnet 60 to the outside of the magnetic sensor 40 pass through the foreign object 91 magnetized by the magnetizing unit 20 (see FIG. 1). Then, the magnetic field lines that have passed through the foreign object 91 are induced by the first induction member 41 and the second induction member 42, pass through the sensing element 50, and then reach the bias magnet 60.

[0045] In this embodiment, the foreign object 91 is made of a magnetic material. As a result, the foreign object 91 magnetized by the magnetizing unit 20 acts on the magnetic field lines, and the magnetic field H applied to the sensing element 50 by the magnetic field lines generated by the bias magnet 60 changes from the bias magnetic field Hb applied when the foreign object 91 is not present. Then, the change in the magnetic field H applied to the sensing element 50 changes the impedance Z of the sensing element 50. In the detection unit 30 of this embodiment, the presence of a foreign object 91 contained in the target 9 can be detected based on a change in the impedance Z of the sensing element 50 in the magnetic sensor 40.

[0046] Next, the effects of the detection unit 30 of this embodiment will be described while comparing it with a conventional magnetic sensor in which the configuration of the bias magnet 60 in the magnetic sensor 40 is different from that of the magnetic sensor 40 of this embodiment. FIG. 7 is a diagram for explaining a conventional magnetic sensor 40A, and is a diagram showing the conventional magnetic sensor 40A as viewed from the upstream side in the z direction. Except for the configuration of the bias magnet, the conventional magnetic sensor 40A has a similar structure to the magnetic sensor 40 of the present embodiment shown in Fig. 3 etc. In the conventional magnetic sensor 40A, the same components as those in the magnetic sensor 40 of the present embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted here.

[0047] The conventional magnetic sensor 40A has a first magnet 61, a second magnet 62, a third magnet 63 and a fourth magnet 64 as bias magnets for applying a bias magnetic field Hb to the sensing element 50. The first magnet 61 to the fourth magnet 64 are provided at both ends in the x direction of the wide portion 412 of the first induction member 41 and at both ends in the x direction of the wide portion 422 of the second induction member .

[0048] Specifically, the first magnet 61 is provided at the downstream end in the x-direction of the wide portion 412 of the first induction member 41 so as to be in contact with the sensing element 50. The first magnet 61 is also arranged so that its N pole is in contact with the wide portion 412 of the first induction member 41. The second magnet 62 is provided at an end portion on the upstream side in the x-direction of the wide portion 412 of the first induction member 41 so as to be in contact with the sensing element 50. In addition, the second magnet 62 is disposed so that its N pole is in contact with the wide portion 412 of the first induction member 41.

[0049] The third magnet 63 is provided at the downstream end in the x-direction of the wide portion 422 of the second induction member 42 in contact with the sensing element 50. The third magnet 63 is also arranged such that its S pole is in contact with the wide portion 422 of the second induction member 42. The fourth magnet 64 is provided at the upstream end in the x-direction of the wide portion 422 of the second induction member 42 in contact with the sensing element 50. The fourth magnet 64 is also arranged such that its S pole is in contact with the wide portion 422 of the second induction member 42.

[0050] In addition, unlike the magnetic sensor 40 in which the bias magnet 60 is provided outside the magnetic sensor 40 relative to the first induction member 41 when viewed from the sensing element 50, the conventional magnetic sensor 40A has a first magnet 61 to a fourth magnet 64 provided between the first induction member 41 and the second induction member 42. In the conventional magnetic sensor 40A, the south pole of the first magnet 61 and the north pole of the third magnet 63 face each other in the y direction through a gap between the wide portion 412 of the first induction member 41 and the wide portion 422 of the second induction member 42. Similarly, in the conventional magnetic sensor 40A, the south pole of the second magnet 62 and the north pole of the fourth magnet 64 face each other in the y direction through a gap between the wide portion 412 of the first induction member 41 and the wide portion 422 of the second induction member 42.

[0051] In the conventional magnetic sensor 40A, magnetic field lines emanating from the N pole of the first magnet 61 pass through the wide portion 412 and the opposing portion 411 of the first induction member 41, and penetrate the sensing element 50. Similarly, magnetic field lines emanating from the N pole of the second magnet 62 pass through the wide portion 412 and the opposing portion 411 of the first induction member 41, and penetrate the sensing element 50. Then, the magnetic field lines that have passed through the sensing element 50 pass from the facing portion 421 of the second induction member 42 through the wide portion 422 and reach the south poles of the third magnet 63 and the fourth magnet 64. Moreover, magnetic field lines emanating from the N pole of the third magnet 63 reach the S pole of the first magnet 61 through the gap between the wide portion 422 of the second induction member 42 and the wide portion 412 of the first induction member 41. Similarly, magnetic field lines emanating from the N pole of the fourth magnet 64 reach the S pole of the second magnet 62 through the gap between the wide portion 422 of the second induction member 42 and the wide portion 412 of the first induction member 41. Magnetic field lines are generated that run from the N poles to the S poles of the first magnet 61 to the fourth magnet 64.

[0052] As a result, a predetermined bias magnetic field Hb is applied to the sensing element 50 in the conventional magnetic sensor 40A. In the conventional magnetic sensor 40A, unlike the magnetic sensor 40, the magnetic field lines generated from the first magnet 61 to the fourth magnet 64 hardly pass through the external space of the magnetic sensor 40A.

[0053] In the conventional magnetic sensor 40A, when a foreign object 91 is present in the target 9, the magnetic field H sensed by the sensing element 50 changes due to the magnetic field lines from the foreign object 91 magnetized by the magnetizing unit 20, and the impedance Z of the sensing element 50 changes. This allows the conventional magnetic sensor 40A to detect the presence of the foreign object 91 included in the target 9.

[0054] Fig. 8 is a diagram showing the relationship between the diameter of the foreign matter 91 and the signal-to-noise ratio (SN ratio) of the output signal for the magnetic sensor 40 of this embodiment and the conventional magnetic sensor 40A. In Fig. 8, the horizontal axis represents the diameter (μm) of the foreign matter 91, and the vertical axis represents the SN ratio. In Fig. 8, the graph represented by "Example" corresponds to the magnetic sensor 40 of this embodiment, and the graph represented by "Comparative Example" corresponds to the conventional magnetic sensor 40A. The SN ratio is the ratio of the peak signal value (Signal) to the noise (Noise) in the output signal.

[0055] In the magnetic sensor 40 and the conventional magnetic sensor 40A, the sensing element 50 had 24 sensing portions 51, the length of the sensing portion 51 in the y direction was 4.3 mm, the width of the sensing portion 51 in the short direction was 0.1 mm, and the distance between adjacent sensing portions 51 in the x direction was 0.05 mm. In addition, in magnetic sensor 40 and conventional magnetic sensor 40A, first induction member 41 has opposing portion 411 with a width in the x direction of 4.2 mm and a length in the y direction of 4.5 mm, and wide portion 412 with a width in the x direction of 13 mm and a length in the y direction of 2 mm. Similarly, in the magnetic sensor 40 and the conventional magnetic sensor 40A, the second induction member 42 had a width of 4.2 mm in the x direction and a length of 4.5 mm in the y direction of the opposing portion 421, and a width of 13 mm in the x direction and a length of 2 mm in the y direction of the wide portion 422.

[0056] In the magnetic sensor 40, five ferrite magnets each having a disk shape with a diameter of 1 mm and a surface magnetic flux density of 45 mT were used as the bias magnet 60. In addition, in the magnetic sensor 40 (shown in Example 1), the five ferrite magnets serving as the bias magnet 60 were arranged side by side on the surface of the wide portion 412 opposite to the sensing element 50. Furthermore, in conventional magnetic sensor 40A, first magnet 61 to fourth magnet 64 are each a disk-shaped ferrite magnet with a diameter of 1 mm and a magnetic flux density of 45 mT.

[0057] Furthermore, foreign matter 91 is made of spherical iron particles with particle sizes of 20 μm to 90 μm, and is magnetized using an NdFe magnet with a surface magnetic flux density of 0.45 T so as to have a magnetic field from the downstream side to the upstream side in the y direction. The detection of foreign object 91 by magnetic sensor 40 and conventional magnetic sensor 40A was performed such that the distance in the y direction between the surface of wide portion 412 of first induction member 41 opposite sensing element 50 and the center of foreign object 91 was 2 mm.

[0058] In the magnetic sensor 40 or the conventional magnetic sensor 40A, for example, when the S / N ratio in FIG. 8 is 10 or more, the foreign object 91 can be detected with high accuracy. 8, the magnetic sensor 40 of this embodiment can detect foreign matter 91 with a smaller particle size with higher accuracy than the conventional magnetic sensor 40A. For example, the conventional magnetic sensor 40A shown in the comparative example has a low signal-to-noise ratio of the output signal for foreign matter 91 with a particle size of about 75 μm or less, and the detection accuracy is likely to be low. On the other hand, the magnetic sensor 40 of this embodiment can detect foreign matter 91 with a particle size of about 40 μm or more with high accuracy.

[0059] In the conventional magnetic sensor 40A, when a foreign object 91 is present in the target object 9, magnetic field lines generated from the magnetized foreign object 91 are induced to the sensing element 50 via the first induction member 41 and the second induction member 42. The magnitude of the magnetic field H applied to the sensing element 50 changes due to the magnetic field lines from the foreign object 91 induced via the first induction member 41 and the second induction member 42. In the conventional magnetic sensor 40A, the sensing element 50 outputs an output signal corresponding to a change in impedance Z caused by a change in the applied magnetic field H.

[0060] In contrast, in the magnetic sensor 40 of this embodiment, when a foreign object 91 is present in the target object 9, as described above, the magnetic field lines generated by the bias magnet 60 pass through the foreign object 91. Then, due to the action of the foreign object 91, the magnetic field H applied to the sensing element 50 by the magnetic field lines generated by the bias magnet 60 changes from the bias magnetic field Hb. In this manner, in the magnetic sensor 40 of this embodiment, the foreign object 91 directly acts on the magnetic field lines generated by the bias magnet 60, and it is therefore presumed that the detection accuracy of the foreign object 91 is improved compared to the conventional magnetic sensor 40A, which senses the magnetic field lines from the foreign object 91 via the first induction member 41 and the second induction member 42.

[0061] (Magnetization direction of foreign matter 91 by magnetizing portion 20) Next, the magnetizing direction of the foreign matter 91 by the magnetizing unit 20 will be described. In the foreign object detection system 1, the foreign object 91 is magnetized by the magnetizing unit 20. In this embodiment, it is preferable that the direction of the magnetic field lines generated from the magnetized foreign object 91 is the same as the direction of the magnetic field lines generated from the bias magnet 60 and passing through the sensing element 50.

[0062] As described above, in the magnetization unit 20, the magnetic field lines generated between the permanent magnets 21 and 22 pass through the foreign object 91 included in the target object 9, thereby magnetizing the foreign object 91. In addition, in the magnetization unit 20, the foreign object 91 is magnetized in the direction of the magnetic field lines passing through the foreign object 91. Hereinafter, the direction of the magnetic field lines passing through the foreign object 91 in the magnetization unit 20 will be referred to as the magnetization direction of the foreign object 91 by the magnetization unit 20. Magnetic field lines pointing in the magnetization direction are generated from the foreign object 91 magnetized by the magnetization unit 20.

[0063] Therefore, in this embodiment, the foreign object 91 may be magnetized by the magnetizing section 20 so that the magnetizing direction of the foreign object 91 by the magnetizing section 20 coincides with the direction of the magnetic lines of force penetrating the sensing element 50 . 3, in the magnetic sensor 40 of this embodiment, the magnetic field lines generated by the bias magnet 60 pass through the sensing element 50 from the downstream side to the upstream side in the y direction. Therefore, the magnetizing unit 20 only needs to magnetize the foreign object 91 so that the magnetization direction of the foreign object 91 faces from the downstream side to the upstream side in the y direction. In addition, the magnetizing unit 20 only needs to magnetize the foreign object 91 included in the object 9 so that the magnetic field lines between the permanent magnets 21 and 22 cross the object 9 from the downstream side to the upstream side in the y direction.

[0064] In the foreign object detection system 1 of this embodiment, the magnetization direction of the foreign object 91 by the magnetization unit 20 is the same as the direction of the magnetic lines of force passing through the sensing element 50, so that the signal-to-noise ratio of the output signal can be increased compared to when the magnetization direction of the foreign object 91 by the magnetization unit 20 is different from the direction of the magnetic lines of force passing through the sensing element 50 (for example, when they are opposite directions).

[0065] 9(a)-(b) are diagrams for explaining the relationship between the magnetization direction of the foreign object 91 and the output signal from the magnetic sensor 40. FIG. 9(a)-(b) show the change over time of the output signal from the magnetic sensor 40 when the foreign object 91 passes through a region of the magnetic sensor 40 facing the bias magnet 60 periodically at a predetermined time interval. The horizontal axis of FIG. 9(a)-(b) shows time (seconds), and the vertical axis shows the magnitude of the output signal from the magnetic sensor 40. Note that FIG. 9(a)-(b) shows the change in voltage (V) corresponding to the amount of change ΔZ in the impedance Z that changes due to the magnetic field H sensed by the magnetic sensor 40, as the output signal.

[0066] The structure of the magnetic sensor 40 is similar to that of the magnetic sensor 40 of the embodiment used in Fig. 8. In the magnetic sensor 40, a bias magnetic field Hb is applied so that the magnetic field lines generated by the bias magnet 60 pass through the sensing element 50 from the downstream side to the upstream side in the y direction. The foreign matter 91 was a spherical iron particle having a particle size of 136 μm. 9(a), the foreign object 91 is magnetized so that the magnetization direction of the foreign object 91 is the same as the direction of the magnetic field lines penetrating the sensing element 50. In addition, in FIG. 9(a), the foreign object 91 is magnetized using an NdFe magnet with a surface magnetic flux density of 0.48 T so that the foreign object 91 has a magnetic field that faces from the downstream side to the upstream side in the y direction. On the other hand, in Fig. 9(b), the foreign object 91 is magnetized so that the magnetization direction of the foreign object 91 is opposite to the direction of the magnetic field lines passing through the sensing element 50. In addition, in Fig. 9(b), the foreign object 91 is magnetized using an NdFe magnet with a surface magnetic flux density of 0.48 T so that the foreign object 91 has a magnetic field that faces from the upstream side to the downstream side in the y direction.

[0067] 9(a)-(b), the distance in the y direction between the surface of the wide portion 412 of the first induction member 41 opposite the sensing element 50 and the center of the foreign object 91 was set to 2 mm. Detection of the foreign object 91 by the magnetic sensor 40 was performed by using a rotation mechanism (not shown) such that the foreign object 91 periodically passed through an area facing the wide portion 412 of the first induction member 41 at intervals of 0.67 seconds.

[0068] 9(a)-(b), peaks were observed in the output signal at intervals of 0.67 seconds when the foreign object 91 passed. In addition, the peaks were observed on the negative side in the output signal of FIG. 9(a), and the peaks were observed on the positive side in the output signal of FIG. 9(b). 9(a) has a higher peak signal strength (peak absolute value) and a higher S / N ratio than those in FIG. 9(b). That is, it was confirmed that when the magnetization direction of the foreign object 91 and the direction of the magnetic field lines passing through the sensing element 50 are the same, the peak signal strength is higher and the S / N ratio is higher than when the magnetization direction of the foreign object 91 and the direction of the magnetic field lines passing through the sensing element 50 are opposite directions. This confirmed that the detection accuracy of the foreign object 91 is higher when the magnetization direction of the foreign object 91 and the direction of the magnetic field lines passing through the sensing element 50 are the same, compared to when the magnetization direction of the foreign object 91 and the direction of the magnetic field lines passing through the sensing element 50 are opposite directions.

[0069] 6, when the magnetization direction of the foreign object 91 is the same as the direction of the magnetic field lines passing through the sensing element 50, the magnetization direction of the foreign object 91 will be the same as the direction of the magnetic field lines extending from the bias magnet 60 into the external space toward the foreign object 91. In this case, the magnetic field lines from the bias magnet 60 are more likely to be sucked into the foreign object 91, and the amount of change in the magnetic field H applied to the sensing element 50 due to the action of the foreign object 91 becomes larger. It is presumed that this results in a larger change in impedance Z due to a change in the magnetic field H applied to the sensing element 50, and thus increases the peak signal strength and S / N ratio of the output signal.

[0070] Furthermore, when the magnetization direction of the foreign object 91 and the direction of the magnetic field lines penetrating the sensing element 50 are opposite to each other, the magnetic field H applied to the sensing element 50 changes to be smaller than the bias magnetic field Hb due to the action of the foreign object 91, as shown by the arrow Q in Fig. 5. In this case, the impedance Z changes to be smaller due to the change in the magnetic field H applied to the sensing element 50. On the other hand, when the magnetization direction of the foreign object 91 and the direction of the magnetic lines of force penetrating the sensor element 50 are the same, the magnetic field H applied to the sensor element 50 changes to be larger than the bias magnetic field Hb due to the action of the foreign object 91, as shown by the arrow P in Fig. 5. In this case, the impedance Z changes to be larger due to the change in the magnetic field H applied to the sensor element 50. It is therefore presumed that when the magnetization direction of the foreign object 91 and the direction of the magnetic lines of force penetrating the sensor element 50 are the same, the peak signal strength and the S / N ratio of the output signal will be larger.

[0071] (Detection of non-magnetic material by detection unit 30) Here, in the above-described embodiment, an example has been described in which the magnetic sensor 40 of the detection unit 30 detects the foreign object 91 made of a magnetic material. However, the detection unit 30 of this embodiment is capable of detecting the foreign object 91 by the magnetic sensor 40 even if the foreign object 91 is made of a non-magnetic metal. As described above, in the detection unit 30 of this embodiment, the magnetic field lines generated from the bias magnet 60 of the magnetic sensor 40 pass through the foreign object 91 included in the target object 9. If the foreign object 91 is made of a non-magnetic metal, the magnetic field lines passing through the foreign object 91 generates an eddy current around the foreign object 91 due to electromagnetic induction. The magnetic sensor 40 can detect the presence of the foreign object 91 in the target 9 by sensing the eddy current generated in the foreign object 91 .

[0072] [Embodiment 2] Next, a second embodiment of the present invention will be described. FIG. 10 is a diagram for explaining the configuration of a magnetic sensor 40 to which the second embodiment is applied, and is a diagram showing the magnetic sensor 40 of the second embodiment as viewed from the upstream side in the z direction. The magnetic sensor 40 of the second embodiment is different from the magnetic sensor 40 of the first embodiment in the shapes of the first induction member 41 and the second induction member 42 and the arrangement of the bias magnet 60. Note that in the second embodiment, the same reference numerals are used for the same configurations as in the first embodiment, and detailed description thereof will be omitted here.

[0073] The magnetic sensor 40 of the second embodiment includes a sensing element 50, a first induction member 41, a second induction member 42, and a bias magnet 60. In the magnetic sensor 40 of the first embodiment, the first induction member 41 and the second induction member 42 have a symmetrical shape in the y direction, whereas in the magnetic sensor 40 of the second embodiment, the first induction member 41 and the second induction member 42 have an asymmetrical shape. In addition, the magnetic sensor 40 of the second embodiment includes three bias magnets 60F, 60G, and 60H as the bias magnet 60. In this embodiment, the bias magnet 60F is an example of an application member that applies a bias magnetic field to the sensing element 50, and the bias magnets 60G and 60H are examples of other application members that apply a bias magnetic field to the sensing element 50 together with the application member. In the description of this embodiment, when the three bias magnets 60F, 60G, and 60H are not distinguished from each other, they are simply referred to as the bias magnet 60.

[0074] The first induction member 41 faces the sensing element 50 and has a rectangular shape extending in the y direction. The width of the first induction member 41 in the x direction can be approximately the same as the width of the sensing element 50 in the x direction, and is, for example, 4.2 mm. The length of the first induction member 41 in the y direction is, for example, 4.5 mm. Note that these values ​​are merely examples and other values ​​may be used.

[0075] The second guide member 42 includes a facing portion 423 facing the sensing element 50, a wide portion 424 that is wider in the x direction than the facing portion 423, and extension portions 425, 426 that extend upstream in the y direction from both ends in the x direction of the wide portion 424. That is, the second guide member 42 has an E-shape in plan view, with the facing portion 423 and the extension portions 425, 426 as horizontal bars and the wide portion 424 as a vertical bar. In the second induction member 42, the width in the x direction of the portion of the facing portion 423 facing the sensing element 50 can be approximately the same as the width in the x direction of the sensing element 50, for example, 4.2 mm. In addition, in the second induction member 42, the length in the y direction of the facing portion 423 is, for example, 4.5 mm. Furthermore, in the second guide member 42, the width of the wide portion 424 in the x direction is, for example, 13 mm, and the length in the y direction is, for example, 2 mm. Furthermore, in the second guide member 42, the width of the extensions 425, 426 in the x direction is, for example, 4.2 mm, and the length in the y direction is, for example, 13.5 mm.

[0076] In the magnetic sensor 40 of the second embodiment, the bias magnets 60 are provided on the first induction member 41 and the extensions 425 and 426 of the second induction member 42, respectively. Specifically, the bias magnet 60F is provided in contact with a surface of the first induction member 41 opposite to the sensing element 50. In addition, the bias magnet 60F is provided on the outer side of the first induction member 41 as viewed from the sensing element 50. Also, the bias magnet 60F is disposed such that its S pole is in contact with the first induction member 41.

[0077] The bias magnet 60G is provided in contact with a surface of the extending portion 425 of the second induction member 42 opposite to the wide portion 424. In addition, the bias magnet 60G is disposed such that its N pole is in contact with the extending portion 425 of the second induction member 42. The bias magnet 60H is provided in contact with a surface of the extending portion 426 of the second induction member 42 opposite to the wide portion 424. In addition, the bias magnet 60H is disposed such that its N pole is in contact with the extending portion 426 of the second induction member 42.

[0078] In the magnetic sensor 40 of the second embodiment, the magnetic field lines generated by the bias magnet 60F exit from the north pole of the bias magnet 60F toward the upstream side in the y direction to the outside of the magnetic sensor 40. The magnetic field lines that exit the magnetic sensor 40 proceed upstream in the x-direction and reach the S pole of the bias magnet 60G. The magnetic field lines that reach the S pole of the bias magnet 60G then pass through the bias magnet 60G, the extension 425, the wide portion 424, and the facing portion 423 of the second induction member 42, and penetrate the sensing element 50. The magnetic field lines that have exited from the magnetic sensor 40 travel downstream in the x-direction and reach the S pole of the bias magnet 60H. The magnetic field lines that have reached the S pole of the bias magnet 60H then pass through the bias magnet 60H, the extension 426, the wide portion 424, and the opposing portion 423 of the second induction member 42, and penetrate the sensing element 50. The magnetic field lines that have passed through the sensing element 50 pass through the first induction member 41 and reach the south pole of the bias magnet 60F.

[0079] As described above, in the magnetic sensor 40 of the second embodiment, the magnetic field lines from the bias magnets 60F, 60G, and 60H pass through the sensing element 50 via the first induction member 41 and the second induction member . In the magnetic sensor 40 of embodiment 2, the magnetic field lines generated from the bias magnet 60 pass through the external space of the magnetic sensor 40, more specifically, the external space of the magnetic sensor 40 located upstream of the first induction member 41 in the y direction.

[0080] In the magnetic sensor 40 of the second embodiment, similarly to the first embodiment, when a foreign object 91 is present in the target object 9, as described above, the magnetic field lines generated by the bias magnet 60 pass through the foreign object 91. Then, due to the action of the foreign object 91, the magnetic field H applied to the sensing element 50 by the magnetic field lines generated by the bias magnet 60 changes from the bias magnetic field Hb. As a result, in the magnetic sensor 40 of the second embodiment, similarly to the first embodiment, the foreign object 91 acts directly on the magnetic field lines generated by the bias magnet 60, and it is presumed that the detection accuracy of the foreign object 91 is improved.

[0081] 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.

[0082] For example, in the magnetic sensor 40 of the above-described embodiment, multiple bias magnets 60 are used, but the number and arrangement of the bias magnets 60 are not limited as long as the magnetic field lines generated from the bias magnets 60 pass through the external space in which the object 9, which is the detection target for the foreign object 91, is located and penetrate the sensing element 50. [Explanation of symbols]

[0083] Reference Signs List 1...foreign object detection system, 9...target object, 20...magnetized portion, 30...detection portion, 40...magnetic sensor, 41...first induction member, 42...second induction member, 50...sensing element, 60...bias magnet, 91...foreign object

Claims

1. a sensing element including a soft magnetic material, having a longitudinal direction and a lateral direction, 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 and a second induction member that face each other in the longitudinal direction with the sensing element therebetween and induce magnetic lines of force in the sensing element; an application member that applies a bias magnetic field to the sensing element; Detecting a foreign object present on an opposite side of the sensing element across the first induction member, The application member is provided on the opposite side of the sensing element with respect to the first induction member. Detection device.

2. Detecting a foreign object made of a magnetic body magnetized in a predetermined magnetization direction; 2. The detection device according to claim 1, wherein the direction in which the magnetic field lines generated by the bias magnetic field pass through the sensing element is the same as the magnetization direction.

3. The first guide member includes a facing portion facing the sensor element in the longitudinal direction, and a wide portion located on the opposite side of the sensor element from the facing portion and extending in the lateral direction, The detection device according to claim 1 or 2, wherein the application member is provided on a side of the wide portion of the first induction member opposite to the sensing element.

4. The first guide member faces one end of the sensing element in the longitudinal direction, The second guide member includes a facing portion facing the other end of the sensor element in the longitudinal direction, a wide portion located on the opposite side of the sensor element with respect to the facing portion and extending in the short direction, and an extension portion extending from the end of the wide portion in the short direction in a direction from the other end in the longitudinal direction toward the one end, and another application member attached to the other end of the extending portion of the second induction member and applying a bias magnetic field to the sensing element together with the application member.

3. A detection device according to claim 1 or 2.

5. a sensing element including a soft magnetic material, having a longitudinal direction and a lateral direction, 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 and a second induction member that face each other in the longitudinal direction with the sensing element therebetween and induce magnetic lines of force in the sensing element; an application member that is provided on the opposite side of the sensing element with respect to the first induction member and applies a bias magnetic field to the sensing element; A magnetic sensor comprising:

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