Apparatus for acquiring state of magnetic powder and method for acquiring state of magnetic powder

Abstract

To acquire a state of magnetic powder in a fluid easily with low energy by using a simple and compact apparatus.SOLUTION: An apparatus 1 according to an embodiment acquires a state of magnetic powder in a surrounding fluid F. The apparatus 1 includes a coil 2, a housing 3 that accommodates the coil 2, a detector 4 that detects a value based on an impedance of the coil 2, and a processor 5 that acquires the state of the magnetic powder in the fluid F from a detection value by the detector 4. The housing 3 is configured to prevent the fluid F from entering an interior of the housing 3. The coil 2 is held inside the housing 3 so as to be movable between a first position and a second position in an axial direction AD of the coil 2. The processor 5 is configured to acquire the state of the magnetic powder in the fluid F from a difference between a detection value obtained by the detector 4 for the coil 2 at the first position and a detection value obtained by the detector 4 for the coil 2 at the second position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an apparatus for acquiring the state of magnetic particles in a surrounding fluid, and a method for acquiring the state of magnetic particles. [Background technology]

[0002] Conventionally, in various mechanical devices, the concentration of metal powder contained in lubricating oils and greases supplied to engaging parts such as bearings and gears has been measured to prevent or predict failures. Specifically, as wear progresses in mechanical components such as metal bearings, metal powder scraped off from each mechanical component becomes mixed into the lubricating oil or grease. Therefore, by appropriately acquiring the state of metal powder contamination in lubricating oils, the wear state of the mechanical components can be grasped. Then, based on the obtained state of metal powder, for example, metal powder concentration, preventive maintenance such as part replacement or adjustment can be performed before a substantial failure occurs. In measuring such metal powder concentration, the magnetic properties (ferromagnetism) of metal powder are advantageously utilized. For example, the concentration of magnetic powder in a liquid to be measured can be measured by moving a container containing magnetic powder near a search coil. The voltage generated in the search coil due to electromagnetic induction caused by the movement can be used to measure the concentration of magnetic powder in the liquid to be measured (see, for example, Patent Document 1).

[0003] Furthermore, Patent Document 2 discloses a method for measuring the concentration of magnetic powder in a fluid using a coil wound around a cylindrical detection unit body provided in the flow path of a pipe through which a fluid containing magnetic powder flows as a measurement target. In the method disclosed in Patent Document 2, the fluid to be measured is introduced from the pipe into the cylindrical detection unit body and discharged from the detection unit body into the pipe by sliding a piston disposed in the detection unit body. The concentration of magnetic powder in the fluid to be measured is then measured from the change in inductance of the coil caused by the introduction of the liquid to be measured into the detection unit body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-194495 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-8885 Summary of the Invention [Problem to be solved by the invention]

[0005] The method disclosed in Patent Document 1 requires transferring the liquid to be measured to a container suitable for measuring the magnetic powder concentration. This makes the process of measuring the magnetic powder concentration cumbersome and difficult to automate. Continuous measurement is also considered difficult. On the other hand, the method disclosed in Patent Document 2, once a measuring unit with a coil surrounding it is attached to a pipe or the like, the work required for each measurement is considered relatively easy. However, sealing is required to prevent leakage of the fluid to be measured from the gap between the moving part, such as a piston that slides inside the cylindrical detecting unit, and the inner wall of the cylindrical detecting unit. This is considered to result in a complex structure of the detecting unit. To reliably prevent fluid leakage, strict sealing is desirable, but the tighter the sealing, the greater the force required for sliding the moving part, such as the piston. Therefore, moving the moving part manually places a heavy burden on the operator, and moving it automatically consumes a lot of energy, such as electricity.

[0006] The present invention has been made in consideration of the above problems, and aims to realize an easy acquisition of the state of magnetic powder in a fluid using a simple, small device with low energy consumption. [Means for solving the problem]

[0007] The device for acquiring the state of magnetic powder of the present invention is a device for acquiring the state of magnetic powder in a surrounding fluid, the device comprising: a coil, a housing for accommodating the coil, a detector for detecting a value based on the impedance of the coil, and a processor for acquiring the state of magnetic powder in the fluid from the detected value by the detector, wherein the housing is configured to prevent the fluid from entering the housing, the coil is held inside the housing so as to be movable between a first position and a second position in the axial direction of the coil, and the processor is configured to acquire the state of magnetic powder in the fluid from the difference between the detected value for the coil at the first position and the detected value for the coil at the second position.

[0008] The device may further include a driver that generates power to move the coil along the axial direction, and a movable part that transmits the power to the coil between the driver and the coil may be housed in the housing together with the coil.

[0009] The housing may have a partition wall facing the coil in the axial direction, and the distance between the partition wall and the coil may change as the coil moves along the axial direction.

[0010] The device may further include a shield formed of a material that is more ferromagnetic than the material of the partition and positioned on the opposite side of the coil from the partition so as to overlap the coil in the axial direction.

[0011] The housing has a first part that is exposed to the fluid when the device is in use, and a second part other than the first part, and the second part may have a connection part or opening used to electrically connect the processing unit or the measuring unit to an external device.

[0012] The processor may obtain a value corresponding to a concentration of magnetic powder in the fluid from a difference between the detection value for the coil at the first position and the detection value for the coil at the second position.

[0013] The method of the present invention for acquiring the state of magnetic powder includes placing a coil at a first position in a space separated from the fluid to be measured by a housing placed in the fluid, detecting a value based on the impedance of the coil at the first position, moving the coil from the first position to a second position along the axial direction of the coil, detecting a value based on the impedance of the coil at the second position, and deriving an indicator of the state of magnetic powder using the difference between the value detected for the coil at the first position and the value detected for the coil at the second position.

[0014] The housing may have a partition wall facing the coil in the axial direction, and moving the coil to the second position may include changing a distance between the partition wall and the coil.

[0015] Moving the coil to the second position may include moving a shield, which is disposed on an opposite side of the coil from the partition wall in the axial direction, together with the coil.

[0016] The indicator may be an indicator of the concentration of the magnetic powder. [Effects of the Invention]

[0017] According to the present invention, it is believed that the state of magnetic powder in a fluid can be easily obtained using a simple and small device with little energy consumption. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view showing an example of a device for acquiring the state of magnetic powder according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a schematic diagram showing an example of the internal structure of the device of FIG. 1 partially immersed in a fluid. [Figure 3A]3 is an enlarged view of part III of FIG. 2, showing the device of FIG. 1 with the coil in one of the first and second positions; [Figure 3B] 3 is an enlarged view of part III in FIG. 2, showing the state in which the coil is placed in the other of the first position and the second position in the device of FIG. 1. [Figure 4] 10A and 10B are schematic diagrams illustrating different inductances between coils at two positions in an embodiment of the present invention. [Figure 5A] FIG. 2 is a perspective view showing an example of a coil structure according to an embodiment of the present invention. [Figure 5B] FIG. 10 is a perspective view showing another example of the structure of the coil in the embodiment of the present invention. [Figure 6] 1. FIG. 4 is a schematic diagram showing a modified example of the tip of the housing on the coil side in the device of FIG. [Figure 7] FIG. 10 is a block diagram illustrating one manner in which a value based on the impedance of a coil is detected in an embodiment of the present invention. [Figure 8A] 10A and 10B are diagrams showing actual measurement results of values ​​based on the impedance of the coil, performed by changing the distance between the coil and the fluid in the configuration of the device according to the embodiment. [Figure 8B] 10 is a diagram showing the results of an investigation into the relationship between the difference between values ​​based on the impedance of coils at two positions detected by the configuration of the device according to the embodiment and the concentration of magnetic powder in the fluid. FIG. [Figure 8C] 10A and 10B are diagrams showing the results of an investigation into the relationship between temperature and a value based on the impedance of a coil detected by the configuration of the device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, with reference to the accompanying drawings, an apparatus for acquiring the state of magnetic powder in a surrounding fluid (hereinafter also simply referred to as a "state acquisition apparatus") and a method for acquiring the state of magnetic powder (hereinafter also simply referred to as a "state acquisition method") according to an embodiment of the present invention will be described. However, the embodiment described below and the accompanying drawings merely show one example of the state acquisition apparatus and the state acquisition method according to the present invention. The state acquisition apparatus and the state acquisition method according to the present invention are not limited to the structure, shape, and relative size and positional relationship between the respective components exemplified in the embodiment described below and the accompanying drawings.

[0020] <Configuration of the status acquisition device according to the embodiment> FIG. 1 shows a status acquisition device 1, which is an example of a device for acquiring the status of magnetic particles in a surrounding fluid, according to one embodiment of the present invention. FIG. 2 schematically shows an example of the internal structure of the status acquisition device 1. FIG. 2 shows the internal structure of the status acquisition device 1 in use. In FIG. 2, the status acquisition device 1 is partially inserted into a fluid F, the status of which is to be acquired. As shown in FIG. 2, the status acquisition device 1 acquires the status of magnetic particles (not shown) in the fluid F surrounding the status acquisition device 1. Examples of the fluid F include oils and greases used in the mining and industrial fields, such as oils and greases, which are used for lubrication, cooling, corrosion prevention, and other purposes in the various mechanical devices mentioned above. However, the fluid F is not limited to oils and greases used in the mining and industrial fields. The fluid in which the status acquisition device of the embodiment is used to acquire the status of magnetic particles therein may be any raw material, intermediate material, finished material, or auxiliary material used, processed, or produced in various industries, such as food, raw materials, and ceramics, in which detection of magnetic particles, which may be impurities, is required.

[0021] As shown in FIG. 1, the status acquisition device 1 includes a coil 2, a housing 3 that houses the coil 2, a detector 4, and a processor 5. The detector 4 detects a value based on the impedance of the coil 2. The processor 5 acquires the status of the magnetic powder in the fluid F from the value detected by the detector 4. The coil 2 is held inside the housing 3 so as to be movable in the axial direction AD of the coil 2. The housing 3 is configured to prevent the fluid F from entering the housing 3. Therefore, the coil 2 is prevented from being exposed to the fluid F. In the status acquisition device 1 of FIGS. 1 and 2, the detector 4 and processor 5 are also housed inside the housing 3.

[0022] The status acquisition device 1 shown in FIG. 2 includes a control unit 10. In the status acquisition device 1 of FIG. 2, the detector 4 and the processor 5 are included in the control unit 10. The control unit 10 may be, for example, an integrated circuit device (IC) that performs predetermined operations according to instructions from a built-in program, such as a microcomputer, a programmable logic device, or a field programmable gate array. The control unit 10 may be configured with any of these ICs, its peripheral components, and a wiring board on which these components are mounted. The control unit 10 may have not only the functions of the detector 4 and the processor 5, but also any other functions, such as a memory function, a voltage and signal generation function, etc. Although not shown in FIG. 2, the status acquisition device of the embodiment may also include a communication device that communicates with external devices, such as a server, a monitoring device, or a control device, external to the status acquisition device.

[0023] As described above, the detector 4 detects a value based on the impedance of the coil 2. In theory, the impedance of the coil 2 is composed of the inductance and equivalent series resistance of the coil 2, so the detector 4 may detect a value based on the inductance of the coil 2, or may detect a value based on the equivalent series resistance of the coil 2. Unless otherwise specified, the phrase "value based on impedance" used in the following description means at least "a value based on impedance or a value based on inductance."

[0024] The detector 4 may be any device capable of detecting a value based on the impedance of the coil 2. For example, the detector 4 may be a voltmeter or ammeter that detects the impedance, inductance, or equivalent series resistance of the coil 2 by measuring the voltage across the coil 2 or the current flowing through the coil 2. The detector 4 may also be a phase meter that measures the phase of the voltage or current based on the impedance, inductance, or equivalent series resistance of the coil 2. The detector 4 may also be a frequency counter that measures the oscillation frequency of the signal generated by the coil 2 as a value based on the inductance of the coil 2. When the control unit 10 includes the detector 4 as shown in FIG. 2, the detector 4 may be embodied as a timekeeping (counting) function block or an analog-to-digital conversion function block of an IC such as a microcomputer that constitutes the control unit 10. The detector 4 may also be the voltmeter, ammeter, phase meter, or frequency counter that is provided separately from the IC such as a microcomputer that constitutes the control unit 10.

[0025] In the example of FIG. 2 , the processor 5 included in the control unit 10 is realized by a combination of functions such as calculation, comparison, storage, and input / output possessed by an IC such as a microcomputer constituting the control unit 10. For example, the processor 5 performs a predetermined calculation on the detection value detected and input by the detector 4 to derive a numerical value indicating a specific state of the magnetic powder in the fluid F. The processor 5 may compare the detection value by the detector 4 or a value obtained by performing a predetermined calculation on the detection value by the detector 4 with one or more stored reference values, and determine a specific state previously assigned to the comparison result as the state of the magnetic powder at that time. Alternatively, the processor 5 may select a specific state from a pre-prepared lookup table of magnetic powder states as the state of the magnetic powder at that time based on the detection value by the detector 4 or a value obtained by performing a predetermined calculation on the detection value by the detector 4. The method by which the processor 5 obtains the state of the magnetic powder in the fluid F from the detection value by the detector 4 is not limited to these exemplary methods.

[0026] A cable CB is connected to the status acquisition device 1. The status acquisition device 1 in the example of FIG. 2 is electrically connected to an external device (not shown), such as an external server, monitoring device, or control device, via the cable CB. Specifically, each device constituting the control unit 10, such as the detector 4 and processor 5, and each functional block of the control unit 10, are electrically connected to external devices (not shown) via the cable CB. The status acquisition device 1 in the example of FIG. 2 is provided with a connection unit 11 that is combined with the cable CB. The connection unit 11 is a plug-side or receptacle-side connector, a terminal block, or the like. The cable CB is provided with a connection unit CB1 that is a receptacle-side or plug-side connector, or the like, and the connection unit 11 is connected to the connection unit CB1.

[0027] The state of the magnetic powder acquired by the processor 5 in the state acquisition device 1 of the embodiment is, for example, the concentration of the magnetic powder. Therefore, the processor 5 may acquire a value corresponding to the concentration of the magnetic powder in the fluid F. By acquiring the state of the concentration of the magnetic powder in the fluid F, it is possible to understand the degree of wear of the mechanical device through which the fluid F flows, and it is believed that efficient and effective preventive maintenance, such as timely part replacement and various maintenance, can be realized. Note that the state of the magnetic powder acquired by the state acquisition device of the embodiment is not limited to the concentration of the magnetic powder, and may also be an index indicating the risk of wear of the mechanical device obtained from the presence, size, and shape of the magnetic powder.

[0028] When the status acquisition device 1 is used, i.e., when acquiring the status of the magnetic powder, it is combined with a container V containing a fluid F, the target of which is to acquire the status of the magnetic powder, as shown in Fig. 2. The fluid F may simply be stored inside the container V, or may be flowing inside the container V.

[0029] The housing 3 has a first portion 31 exposed to the fluid F when the status acquisition device 1 is in use, and a second portion 32 other than the first portion 31. The first portion 31 and the second portion 32 are aligned in the axial direction AD and connected to each other. In the status acquisition device 1, a portion of the housing 3 on the first portion 31 side is inserted into the container V when the status acquisition device 1 is in use, and the portion not inserted into the container V (e.g., the second portion 32) protrudes from the container V. When the status acquisition device 1 is in use, the first portion 31 is inserted into the container V that contains the fluid F or through which the fluid F flows, i.e., into the fluid F. On the other hand, the second portion 32 is preferably not exposed to the fluid F even when the status acquisition device 1 is in use. The housing 3 is formed of, for example, a metal such as aluminum or a resin such as various engineering plastics. However, the housing 3 may be formed using any metal or resin other than aluminum, and is not particularly limited in terms of material.

[0030] The housing 3 has a first internal space 31c surrounded by an outer wall constituting the first portion 31, and a second internal space 32c surrounded by an outer wall constituting the second portion 32. The first internal space 31c and the second internal space 32c are aligned in the axial direction AD and communicate with each other. The coil 2 is accommodated in the first internal space 31c. Meanwhile, the control unit 10 is accommodated in the second internal space 32c. In the example of FIG. 2, the detector 4 and the processor 5 are also accommodated in the second internal space 32c.

[0031] The housing 3 has an engagement portion 33 that is coupled to the container V to attach the status acquisition device 1 to the container V when the status acquisition device 1 is in use. The engagement portion 33 contacts the inner wall of a through-hole provided in the container V. In the example of FIG. 2 , a male thread is formed on the outer wall surface of the engagement portion 33, and the male thread engages with a female thread formed on the inner wall surface exposed at the through-hole of the container V. The male thread on the engagement portion 33 makes it easy to attach the status acquisition device 1 to the container V. Furthermore, the presence of the thread extends the interface between the container V and the housing 3 from the inside to the outside of the container V, thereby suppressing leakage of the fluid F to the outside of the container V. Note that instead of providing a male thread, a sealing material such as a packing may be provided on the engagement portion 33 to suppress leakage of the fluid F from the container V. Even if a sealing material is provided on the engagement portion 33 of the housing 3, there is no particular need to move the housing 3 relative to the container V while acquiring the status of the magnetic material, and therefore such a sealing material does not increase energy consumption when acquiring the status of the magnetic material.

[0032] The housing 3 has a partition wall 3a as an outer wall constituting a tip portion including an end face of the first portion 31 opposite to the second portion 32 side. The partition wall 3a has an inner surface substantially perpendicular to the axial direction AD of the coil 2. The partition wall 3a faces the coil 2 in the axial direction AD. Specifically, the inner surface of the partition wall 3a faces the winding surface of the coil 2 (the surface perpendicular to the axial direction AD).

[0033] The second portion 32 of the housing 3 has an opening 3h penetrating the outer wall constituting the second portion 32. Wires 3w passing through the opening 3h electrically connect the connection portion 11 to each device of the control unit 10, such as the detector 4 and processor 5, and each functional block of the control unit 10. As described above, a cable CB connected to an external device (not shown) is connected to the connection portion 11. The second portion 32 of the housing 3 may thus have the connection portion 11 and opening 3h used to electrically connect the processor 5 or detector 4 to the external device. Because the second portion 32, which is not exposed to the fluid F, has the opening 3h and connection portion 11, electrical connection between the status acquisition device 1 and the external device can be realized without allowing the fluid F to enter the housing 3 or exposing electrical connection points to the fluid F.

[0034] The second portion 32 may not have the connection portion 11 but may have only the opening 3h, and the cable CB may be introduced into the housing 3 from the opening 3h to be connected to the processor 5 and / or the detector 4. Alternatively, the second portion 32 may not have a through-hole like the opening 3h in Fig. 2, and the contact pin (not shown) of the connection portion 11 may be inserted into the housing 3 or molded integrally with the molding material of the housing 3, and may be connected to the wire 3w.

[0035] The status acquisition device 1 of FIG. 2 further includes a driver 6 that generates power to move the coil 2 along the axial direction AD, and a movable part 7 that transmits the power generated by the driver 6 to the coil 2 between the driver 6 and the coil 2. The driver 6 is disposed within the second internal space 32c. Meanwhile, the movable part 7 is disposed across the first internal space 31c and the second internal space 32c. That is, the driver 6 and the movable part 7, together with the coil 2, are housed within the housing 3. Therefore, the movable part 7 is not exposed to the fluid F during use of the status acquisition device 1. Therefore, sealing that strictly prevents the inflow of the fluid F around the movable part 7 (and the outflow of the fluid F from around the movable part 7) is not required. This allows the coil 2 to be moved with little energy consumption.

[0036] The actuator 6 in the example of FIG. 2 includes a rod 61, and moves the rod 61 to move the coil 2 along the axial direction AD under the control of the control unit 10. The actuator 6 moves the rod 61 forward from the main body of the actuator 6 by a predetermined distance along the axial direction AD of the coil 2, or moves the rod 61 back toward the main body of the actuator 6. Alternatively, the actuator 6 may rotate the rod 61 by a predetermined angle or a predetermined number of rotations. In this way, the actuator 6 moves the rod 61 under the control of the control unit 10 to move the coil 2 by a predetermined distance along the axial direction AD. Examples of the actuator 6 include a linear actuator and a motor, but the actuator 6 is not limited to these and may be any device that converts energy such as electricity into mechanical energy.

[0037] The movable part 7 includes a transmission member (shaft) 71. In the example shown in FIG. 2 , the transmission member 71 in the movable part 7 specifically transmits the power generated by the driver 6 to the coil 2. The transmission member 71 is configured so that the movement of the rod 61 of the driver 6 is transmitted to the transmission member 71, and is coupled to, engaged with, or in contact with the rod 61 directly or via some medium. The transmission member 71 is also configured so that the movement of the transmission member 71 is transmitted to the coil 2, and is coupled to, engaged with, or in contact with the coil 2 directly or via some medium. The transmission member 71 moves along the axial direction AD in response to the movement of the rod 61, thereby moving the coil 2 in the axial direction AD.

[0038] The transmission member 71 is inserted into a holding member 74 fixed to the inner wall of the housing 3 and is held inside the housing 3 by the holding member 74 so as to be movable in the axial direction AD. A face plate 72 that moves together with the transmission member 71 is fixed to the transmission member 71. As an example, the transmission member 71 rotates around a central axis in the axial direction AD in response to rotation of the rod 61 of the driver 6. The transmission member 71 may move relative to the holding member 74 along the axial direction AD due to the interaction between a male thread on the surface of the transmission member 71 and a female thread on the through hole of the holding member 74. The transmission member 71 may also move relative to the holding member 74 simply in response to the forward and backward movement of the rod 61 along the axial direction AD. An elastic body 73 is sandwiched between the face plate 72 and the holding member 74. In the example of FIG. 2, the elastic body 73 is a coil spring. The elastic body 73 biases one of the holding member 74 and the face plate 72 toward or away from the other in the axial direction AD of the coil 2. Therefore, even when the transmission member 71 is simply in contact with the rod 61 of the driver 6, the transmission member 71 can be moved together with the coil 2 in the axial direction AD in accordance with the movement of the rod 61. Note that the holding member 74 may be fixed to the transmission member 71 without being fixed to the housing 3, while the transmission member 71 may simply be inserted through the face plate 72. The holding member 74 may then move together with the transmission member 71 relative to the face plate 72 fixed to the housing 3.

[0039] In the example of FIG. 2 , in addition to the transmission member 71, the movable unit 7 includes a substrate 76, a relay member 77, and a support member 75 connecting the substrate 76 and the relay member 77. The movable unit 7 may include the holding member 74 when the holding member 74 moves together with the transmission member 71, or may include the face plate 72 when the face plate 72 moves together with the transmission member 71. At least one of the substrate 76 and the relay member 77 is fixed to the transmission member 71. The substrate 76 may have an electrical circuit pattern formed thereon, for example, necessary for applying a desired voltage and / or signal to the coil 2 or detecting the impedance, inductance, etc. of the coil 2, and may further have predetermined components mounted thereon. For example, the detector 4 and the processor 5 may be configured on the substrate 76. The electrical circuit configured on the substrate 76 and / or the electrical circuit included in the control unit 10 may be connected to the coil 2 via the relay member 77 and wires 78.

[0040] 2 is provided with a shield 21 closer to the center of the housing 3 than the coil 2 in the axial direction AD. The shield 21 moves along the axial direction AD together with the coil 2 by a transmission member 71. The shield 21 may be fixed to the transmission member 71 together with the coil 2, or may simply be engaged with or in contact with the transmission member 71 so that the movement of the transmission member 71 is transmitted to the shield 21.

[0041] The shield 21 functions as a magnetic shield for the coil 2. For this reason, it is preferable that the shield 21 be made of a ferromagnetic material. Preferably, the shield 21 is formed of a material that is more ferromagnetic than the material of the partition wall 3a. The shield 21 is disposed on the opposite side of the coil 2 from the partition wall 3a so as to overlap with the coil 2 in the axial direction AD of the coil 2. By providing such a shield 21, it is thought that the influence of the magnetic environment on the second internal space 32c side on obtaining the state of the magnetic powder is reduced, and the detection sensitivity of the coil 2 to the magnetic powder in the fluid F is improved.

[0042] 2, the shield 21 also covers the coil 2 on the radially outer side of the coil 2 that is perpendicular to the axial direction AD (i.e., the radially outer periphery of the coil 2, hereinafter also referred to simply as "the side part of the coil 2"). This may reduce the effect of the magnetic environment of the side part of the coil 2 on acquiring the state of the magnetic powder. Examples of materials that can be used to configure the shield 21 include metals such as iron, cobalt, and nickel, alloys of these metals, rare earth metals such as gadolinium, and ceramics such as ferrite.

[0043] The partition 3a for such a shield 21 may be formed of any metal or resin, as described above for the housing 3, or may be formed of any inorganic compound. Among these various materials, the partition 3a is preferably formed of a material that is less susceptible to the effects of magnetic fields. Therefore, from the perspective of a material that is less susceptible to the effects of magnetic fields, the partition 3a is preferably formed of a material made of a so-called non-magnetic substance, such as ceramics or various plastics.

[0044] In the status acquisition device 1 of FIG. 2, the coil 2 is surrounded by a cap portion 3b that forms the tip of the housing 3 on the first portion 31 side. The partition wall 3a is part of the cap 3b. In the housing 3 shown in FIG. 2, the cap portion 3b is made of a material that is different from the material that forms the other parts of the housing 3, i.e., the parts that do not surround the coil 2. The cap portion 3b and the other parts of the housing 3 are joined together via a sealing material such as an adhesive or packing, thereby preventing the fluid F from entering the inside of the housing 3.

[0045] <Getting the status of magnetic powder> Next, the operation and function of the state acquisition device of the embodiment, which acquires the state of magnetic powder in the surrounding fluid, will be described with reference to FIGS. 3A, 3B, and 4. FIGS. 3A and 3B each show an enlarged view of the coil 2 and its surrounding area in the state acquisition device 1 shown in FIG. 2. In the state acquisition device 1 of the embodiment, the coil 2 is held inside the housing 3 so as to be movable between at least two arbitrary positions, a first position and a second position, in the axial direction AD of the coil 2. The processor 5 (see FIG. 2) is configured to acquire the state of the magnetic powder in the fluid F from the difference between the detection value by the detector 4 (see FIG. 2) for the coil 2 in the position before movement and the detection value by the detector 4 for the coil 2 in the position after movement.

[0046] FIG. 3A shows the coil 2 in FIG. 2 at position P1, which is an example of one of the first and second positions in the axial direction AD. FIG. 3B shows the coil 2 at position P2, which is an example of the other of the first and second positions. Either position P1 or P2 may be the first position, and either position P1 or P2 may be the second position. In FIGS. 3A and 3B, position P1 is closer to the partition wall 3a than position P2. The coil 2 is surrounded by the cap portion 3b at both positions P1 and P2. The operation and function of the status acquisition device 1 will be described below using an example in which the coil 2 is held inside the housing 3 so as to be movable at least between positions P1 and P2. The processor 5 acquires the status of the magnetic powder in the fluid F from the difference between the detection value for the coil 2 at position P1 and the detection value for the coil 2 at position P2.

[0047] In the state acquisition device 1, the detector 4 detects a value based on the impedance of the coil 2 at position P1 (hereinafter also referred to as the "first value") and a value based on the impedance of the coil 2 at position P2 (hereinafter also referred to as the "second value"). That is, in the state acquisition device 1, one of the first value and the second value is detected with the first portion 31 inserted into the target fluid F. Thereafter, the coil 2 is moved from one of positions P1 and P2 to the other under the control of the control unit 10 (see FIG. 2), and the other of the first value and the second value is detected. The coil 2 may be moved from position P1 to position P2, or from position P2 to position P1.

[0048] The detector 4 detects any value based on the impedance of the coil 2 in any manner, without particular limitations. For example, as described above, the detector 4 measures the voltage or current generated in the coil 2 by the current or voltage applied to the coil 2 by the control unit 10 (see FIG. 2 ) as a value based on the impedance. The detector 4 may also measure the phase of the voltage or current generated in the coil 2 by the application of the current or voltage as a value based on the impedance of the coil 2. The detector 4 may also measure the frequency of a signal generated in an oscillator circuit including the coil 2 as a value based on the inductance of the coil 2.

[0049] Movement of coil 2 along the axial direction AD between positions P1 and P2 changes the distance between partition 3a and coil 2. That is, movement of coil 2 between positions P1 and P2 changes the distance in the axial direction AD between coil 2 and fluid F, the state of the magnetic powder inside of which is to be acquired. On the other hand, if magnetic powder is present in fluid F, the magnetic permeability of fluid F containing that magnetic powder changes. As described below, the magnetic permeability of fluid F affects the inductance of coil 2, i.e., the impedance, to an extent that depends on the distance between fluid F and coil 2.

[0050] Fig. 4 is a schematic diagram illustrating that the inductance of coil 2 differs between positions P1 and P2. Fig. 4 schematically illustrates the housing 3 and shield 21 of the state acquisition device 1 of the embodiment inserted into fluid F, as well as coil 2α and coil 2β as the coil 2 shown in Fig. 3A and the like. Coil 2α is shown as the coil 2 located at position P1, and coil 2β is shown as the coil 2 located at position P2. Note that in Fig. 4, the distance between positions P1 and P2 is enlarged to make it easier to understand the difference in the status of coil 2α and coil 2β.

[0051] As shown in FIG. 4, when magnetic powder M is present in fluid F, the magnetic permeability of the entire fluid F changes depending on the state of the magnetic powder M, such as its concentration. The change in the magnetic permeability of fluid F has a greater effect on the magnetic permeability acting on coil 2α, which is closer to partition 3a, than on the magnetic permeability acting on coil 2β, which is farther from partition 3a. Therefore, the change in the interdigital magnetic flux φ accompanying the change in the magnetic permeability of fluid F is greater for coil 2α than for coil 2β. Therefore, as the magnetic permeability of fluid F increases or decreases depending on the state of the magnetic powder M, the inductance of coil 2α changes more than the inductance of coil 2β. Therefore, the state of the magnetic powder M, such as its concentration, can be obtained from the difference between the value based on the impedance of coil 2α at position P1 and the value based on the impedance of coil 2β at position P2.

[0052] In addition, since there is no difference between coil 2α and coil 2β in the distance from the fluid F at the side portions of coil 2, the difference in inductance between coil 2α and coil 2β is unlikely to be affected by the fluid F at the side portions of coils 2α and 2β. Also, as shown in FIGS. 2 to 4, by covering coil 2 (coils 2α and 2β) with shield 21 at the side portions of coil 2 as well, the influence of the magnetic environment at the side portions of coil 2 can be reduced. In comparison, it is thought that it becomes easier to understand the difference in inductance due to the difference in distance from the fluid F in the axial direction AD.

[0053] Furthermore, since the shield 21 is interposed between the coil 2 and the region opposite the partition wall 3a, it is believed that the magnetic environment of the region opposite the partition wall 3a has little effect on the inductance of the coil 2. Therefore, it is believed that it is possible to more accurately detect a value based on the impedance of the coil 2, which corresponds to the state of the magnetic powder M. Furthermore, by forming the partition wall 3a from a material that is not easily affected by magnetic fields, it is believed that the coil 2 becomes more susceptible to changes in the state of the magnetic powder M in the fluid F, and it is believed that it is possible to improve the detection sensitivity of the state of the magnetic powder M, such as concentration.

[0054] The distance D1 between the coil 2 at position P1 and the outer surface 3aa of the partition 3a facing the fluid F in the axial direction AD may be, for example, 0.3 mm or more and 4.0 mm or less. Meanwhile, the distance D2 between the coil 2 at position P2 and the outer surface 3aa of the partition 3a may be, for example, 1.0 mm or more and 6.0 mm or less. The thickness T of the partition 3a may be, for example, 0.2 mm or more and 2.0 mm or less. The difference between the distance D1 and the distance D2 is, for example, 0.5 mm or more and 5.5 mm or less, preferably 2.0 mm or more and 4.5 mm or less, more preferably 2.5 mm or more and 4.0 mm or less, and most preferably 3.0 mm. It is believed that a sufficient difference in impedance-based values ​​can be obtained between the coil 2 at the two positions under conditions of a limited travel distance. The coil 2 in FIGS. 3A and 3B is formed on a wiring board (wiring board 20 in FIG. 5A) as in the example of FIG. 5A, which will be referred to later. Distances D1 and D2 are the distances between the outer surface 3aa of the partition wall 3a and the surface of the wiring board on which the coil 2 is formed that faces the partition wall 3a.

[0055] The processor 5 obtains the state of the magnetic powder in the fluid F from the difference between the first value and the second value detected by the detector 4. That is, the processor 5 derives the difference between the first value and the second value by an operation such as subtraction. If necessary, the processor 5 may further perform a predetermined operation on the subtraction result to obtain a numerical value related to the state of the magnetic powder. The processor 5 may also compare the subtraction result between the first value and the second value with one or more preset reference values ​​and obtain a specific state pre-assigned to the comparison result as the state of the magnetic powder. The processor 5 may apply the subtraction result between the first value and the difference value to a calibration curve prepared in advance for the state of the magnetic powder, and obtain the specific state indicated by the calibration curve as the state of the magnetic powder. The processor 5 may also select a specific state from a lookup table prepared in advance for the state of the magnetic powder based on the subtraction result between the first value and the second value, and obtain the specific state as the state of the magnetic powder.

[0056] An example of the state of the magnetic powder in the fluid F that is acquired by the processor 5 is the concentration of the magnetic powder. Therefore, the processor 5 may acquire the concentration value of the magnetic powder in the fluid F itself from the difference between the first value and the second value, or may acquire a value corresponding to the concentration.

[0057] Furthermore, the processor 5 or the control unit 10 (see FIG. 2 ) may determine that the magnetic powder is in a specific, predefined state based on the results of the processor 5's calculation, comparison with a reference value, application to a calibration curve, or reference to a lookup table. For example, the processor 5 or the control unit 10 may determine that the concentration of the magnetic powder exceeds a predetermined threshold based on these results. Based on this determination, the control unit 10 may then issue an alarm indicating that the mechanical device using the fluid F is in an abnormal state due to wear of mechanical components or the like, or may notify the user of the need for repair or inspection. As described above, the processor 5 and the control unit 10 are embodied by an IC such as a microcomputer. Therefore, the IC embodying the processor 5 may be programmed to perform the above-mentioned calculation processing, comparison processing, application to a calibration curve, reference to a lookup table, judgment processing, and notification processing such as an alarm.

[0058] <Example of a coil> The structure of the coil included in the status acquisition device according to the embodiment will be described with reference to FIGS. 5A and 5B. FIGS. 5A and 5B each show a more specific example of the structure of the coil 2. In the example shown in FIG. 5A, the coil 2 is formed using a wiring board 20. That is, the coil 2 in the example of FIG. 5A is configured with a spiral conductor pattern formed on the wiring board 20. The conductor pattern configuring the coil 2 may be formed on only one surface of the wiring board 20, or may be formed on both surfaces. Furthermore, when the wiring board 20 is a multilayer wiring board having an inner conductor layer, the coil 2 may be configured with an inner conductor pattern, or may be configured with a surface conductor pattern and an inner conductor pattern connected by through-hole conductors in the wiring board 20. Using multiple conductor layers allows a coil 2 with greater inductance to be provided in a smaller occupied area.

[0059] The coil 2 is combined with a shield 21. The shield 21 in FIG. 5A has an overall disk-like shape and includes a core portion 21a extending along the axial direction AD of the coil 2, a base portion 21b on which the wiring board 20 is placed, and a sidewall portion 21c protruding from the periphery of the base portion 21 along the axial direction AD to cover the side surface of the wiring board 20. In a front view, the area of ​​the shield 21 is larger than the area of ​​the region surrounded by the outer periphery of the coil 2. When the coil 2 is formed on the wiring board 20 as in the example of FIG. 5A, the area of ​​the shield 21 is larger than the area of ​​the wiring board 20 in a front view. Note that "front view" means viewing an object from a line of sight along the axial direction AD of the coil 2. If the area of ​​the shield 21 in a front view is larger than the area of ​​the region occupied by the coil 2, it is believed that the influence of the magnetic environment on the region opposite the coil 2 side with respect to the shield 21 can be more reliably reduced.

[0060] When the coil 2 and the shield 21 are combined, the core portion 21a functions as the core of the coil 2. The core portion 21a can increase the impedance of the coil 2 to a level that makes it easy to detect. Furthermore, when the coil 2 is combined with the shield 21, the side surfaces of the coil 2 are covered by the side wall portions 21c. Therefore, as described above, the inductance of the coil 2 is less susceptible to the magnetic environment on the sides of the coil 2.

[0061] The dimensions and specifications of the coil 2 and shield 21 configured as in the example of Fig. 5A are exemplified below. The diameter D21 of the shield 21 is exemplified as 14 mm, and the thickness T21 of the shield 21 is exemplified as 4.25 mm. The wiring board 20 is, for example, a four-layer board, and its thickness T20 is exemplified as 0.8 mm. The number of turns of the coil 2 is, for example, 27.5 (turns).

[0062] The coil 2 in the example of Fig. 5B is configured by a conductor 2a wound around the core portion 21a of the shield 21, similar to the example of Fig. 5A. Therefore, the coil 2 tends to have a relatively small resistance component. Furthermore, since a component such as the wiring board 20 in Fig. 5A is not required, the coil 2 can be formed relatively easily and at low cost.

[0063] <Modified housing> Fig. 6 shows a modified example of the tip end portion of the housing 3 on the coil 2 side, which is included in the status acquisition device of the embodiment. In the example of Fig. 6, the housing 3 has a partition wall 3a facing the coil 2, similar to the example of Fig. 2 etc., and also has a peripheral wall 34 surrounding the coil 2 on the side of the coil 2. The peripheral wall 34 surrounds the partition wall 3a along the entire outer periphery of the partition wall 3a and is in contact with the side surface of the partition wall 3a along the entire outer periphery of the partition wall 3a. The peripheral wall 34 constitutes the part of the tip end portion of the housing 3 on the coil 2 side other than the partition wall 3a.

[0064] The peripheral wall 34 protrudes further from the partition wall 3a toward the side opposite to the coil 2 in the axial direction AD of the coil 2. Therefore, the peripheral wall 34, which protrudes further from the partition wall 3a, may prevent contact between the partition wall 3a and an external object. That is, the partition wall 3a may be protected from mechanical stress such as impact due to contact, and damage to the partition wall 3a may be avoided. When the partition wall 3a is thin and / or formed of a material such as resin that does not have very high mechanical strength, the housing 3 in the example of FIG. 6 may be useful.

[0065] From the viewpoint of protecting the partition wall 3a, the peripheral wall 34 is preferably formed of a material having at least higher mechanical strength than the partition wall 3a. For example, the peripheral wall 34 may be formed of a metal such as aluminum. The peripheral wall 34 may be formed integrally with the portion of the housing 3 other than the tip portion, or may be formed separately and combined with the portion other than the tip portion. The protruding length L34 of the peripheral wall 34 from the partition wall 3a may be, for example, greater than 0 mm and equal to or less than 50 mm. It is believed that this provides a protective effect for the partition wall 3a, and that the peripheral wall 34 protruding from the partition wall 3a does not significantly obstruct the flow of the fluid F.

[0066] <Example of a mode for detecting a value based on coil impedance> With reference to the block diagram shown in FIG. 7, one mode of detecting a value based on the impedance of a coil in the state acquisition device 1 of the embodiment will be described. FIG. 7 shows an example of internal functional blocks of the state acquisition device 1 of the embodiment that detects a value based on the impedance of the coil 2 by measuring the oscillation frequency of the oscillation circuit OS configured by the coil 2 and the capacitor 8. That is, the oscillation circuit OS is configured by the coil 2, the capacitor 8, and the auxiliary oscillation circuit OS1. The auxiliary oscillation circuit OS1 is configured by a bias source, an inverter, and / or a feedback amplifier, etc., which are necessary for the LC resonant circuit configured by the coil 2 and the capacitor 8 to oscillate as intended. The oscillation frequency of the oscillation circuit OS is detected by a detector 4 configured by, for example, a counter. The oscillation circuit OS configured by an LC resonant circuit has a frequency f=1 / (2×π×(L×C)) expressed by the inductance L of the coil 2 and the capacitance C of the capacitor 8. 1 / 2 ) Therefore, the oscillation frequency of the oscillator circuit OS is suitable for detection as a value based on the impedance of the coil 2, more specifically, as a value based on the inductance.

[0067] Meanwhile, under the control of a control unit 10 mainly composed of an IC such as a microcomputer, a driver 6, which may be an actuator or a motor, generates power for moving the coil 2 along the axial direction AD. The power generated by the driver 6 is transmitted to the coil 2 by a transmission member 71, and the coil 2 is moved along the axial direction AD between two positions (a first position and a second position). A detector 4 detects the oscillation frequency of the oscillator circuit OS when the coil 2 is in the first position and when it is in the second position.

[0068] In the example of FIG. 7, the processor 5, which is part of the control unit 10, derives the difference δ between the frequency detected by the detector 4 for the coil 2 at the first position and the frequency detected by the detector 4 for the coil 2 at the second position. For example, if the first position is position P1 in FIG. 3A and the second position is position P2 in FIG. 3B, and the fluid to be measured contains magnetic powder, the inductance of the coil 2 at the first position is greater than the inductance of the coil at the second position. In other words, the oscillation frequency when the coil 2 is at the first position is lower than the oscillation frequency when the coil 2 is at the second position. Therefore, the processor 5 may calculate the difference δ by subtracting the frequency detected by the detector 4 for the coil 2 at the first position from the frequency detected by the detector 4 for the coil 2 at the second position.

[0069] The processor 5 then acquires the state of the magnetic powder to be acquired, for example, the concentration of the magnetic powder, by substituting or applying the difference δ into a predefined relational expression or lookup table that indicates the relationship between the difference δ and the state of the magnetic powder. The state acquisition device 1 in FIG. 7 is equipped with a communication device CM. Therefore, the state of the magnetic powder acquired by the processor 5 is transmitted to a device external to the state acquisition device 1 via wired or wireless communication as necessary.

[0070] <How to obtain the status of magnetic powder> Next, a method for acquiring the state of magnetic powder (status acquisition method) according to an embodiment of the present invention will be described with reference again to Figures 2, 3A, and 3B. Note that the operation of the status acquisition device described in the description of the status acquisition device of the embodiment may be performed in the status acquisition method of the embodiment even if it is not mentioned in the following description.

[0071] In the state acquisition method of the embodiment, as illustrated in FIG. 2, a coil 2 is placed at a first position in a space (first internal space 31c of the housing 3 in the example of FIG. 2) separated from the fluid F by a housing 3 placed in the fluid F, the state of which is to be measured for magnetic powder. The first position may be position P1 shown in FIG. 3A or position P2 shown in FIG. 3B. When the coil 2 is placed at the first position, a value based on the impedance of the coil 2 at the first position is detected. The value based on the impedance of the coil 2 may be, for example, a voltage or current generated in the coil 2 by a current or voltage applied to the coil 2, or the phase of the voltage or current generated by the application of the current or voltage to the coil 2. Furthermore, the value based on the impedance of the coil 2 may be the frequency of a signal generated by an oscillator circuit including the coil 2, or any value based on the inductance of the coil 2 may be detected.

[0072] In the state acquisition method according to the embodiment, after detecting a value based on the impedance of the coil 2 at the first position, the coil 2 is moved from the first position to a second position along the axial direction AD of the coil 2. For example, the coil 2 is moved from position P1 shown in FIG. 3A to position P2 shown in FIG. 3B. Alternatively, the coil 2 is moved from position P2 shown in FIG. 3B to position P1 shown in FIG. 3A. The first position and the second position are separated by a predetermined distance in the axial direction AD. The predetermined distance is, for example, 0.5 mm or more and 5.5 mm or less, preferably 2.0 mm or more and 4.5 mm or less, more preferably 2.5 mm or more and 4.0 mm or less, and most preferably 3.0 mm.

[0073] 2, 3A, and 3B, the housing 3 has a partition wall 3a that faces the coil 2 in the axial direction AD of the coil 2. Therefore, moving the coil 2 from the first position to the second position may include changing the distance between the partition wall 3a and the coil 2.

[0074] 2, 3A, and 3B, a shield 21 is disposed on the side of the coil 2 opposite the partition wall 3a in the axial direction AD of the coil 2. Therefore, moving the coil 2 from the first position to the second position may include moving the shield 21 together with the coil 2. Doing so may reduce the effect on the inductance of the coil 2 of the magnetic environment in the region opposite the partition wall 3a side of the coil 2 in both the first and second positions.

[0075] When coil 2 is placed in the second position, a value based on the impedance of coil 2 at the second position is detected. The value based on the impedance of coil 2 at the second position is the same as the value detected as the value based on the impedance of coil 2 at the first position. Therefore, the value detected for coil 2 at the second position may be the voltage or current generated in coil 2 by the current or voltage applied to coil 2, the phase of the voltage or current, or the frequency of a signal generated in an oscillator circuit including coil 2.

[0076] In the state acquisition method according to the embodiment, an index of the state of the magnetic powder is derived using the difference between the value (first value) detected for the coil 2 at the first position and the value (second value) detected for the coil 2 at the second position. That is, the difference δ between the first value and the second value is derived by subtraction. Then, for example, a calculation is performed using a predefined relational expression between the difference δ and the state of the magnetic powder, and the index of the state of the magnetic powder is derived from the result of the calculation. Alternatively, the difference δ may be compared with one or more preset reference values, and a numerical value, level, degree, scale, or degree (hereinafter collectively referred to as "level") assigned to the comparison result may be derived as the index of the state of the magnetic powder. Alternatively, the difference δ may be applied to a calibration curve prepared in advance for the state of the magnetic powder, and a specific level indicated by the calibration curve may be derived as the index of the state of the magnetic powder. Alternatively, a specific level may be selected from a lookup table prepared in advance for the state of the magnetic powder based on the difference δ, and the specific level may be derived as the index of the state of the magnetic powder.

[0077] By deriving an index indicating the state of the magnetic powder using these means, the state of the magnetic powder indicated by the derived index can be obtained. The index derived in the state acquisition method of the embodiment may be an index of the concentration of the magnetic powder. Therefore, an example of the state of the magnetic powder acquired in the state acquisition method of the embodiment may be the concentration of the magnetic powder or a value corresponding to the concentration of the magnetic powder.

[0078] <Example of measuring values ​​based on impedance> 8A to 8C show the results of investigating the interrelationships between the distance between the coil 2 and the fluid F, the state of the magnetic powder in the fluid F, temperature, and values ​​based on the impedance of the coil 2, using the configuration of an embodiment of a status acquisition device having the functional blocks shown in FIG. 7. FIG. 8A shows the relationship between the distance D0 (horizontal axis) between the coil 2 and the inner surface of the partition wall 3a (see FIG. 2) and the frequency of the oscillator circuit OS (vertical axis) of FIG. 7, which is a value based on the impedance of the coil 2, for magnetic powder concentrations of 0 ppm and 20,000 ppm, which represent the state of the magnetic powder in the fluid F. The vertical axis shows the count value of the frequency of the oscillator circuit OS counted by the counter constituting the detector 4 of FIG. 7. FIG. 8B shows the results of investigating the relationship between the difference (vertical axis) between the count values ​​of the frequency of the oscillator circuit OS obtained for the coil 2 located at a distance D=1.0 mm and a distance D=4.0 mm from the fluid F, and the concentration of the magnetic powder in the fluid F (horizontal axis). Figure 8C also shows the results of investigating the relationship between temperature (horizontal axis) and the count value (vertical axis) of the frequency of the oscillator circuit OS at a magnetic powder concentration of 20,000 ppm using detector 4 of Figure 7, as in Figure 8A, for coils located at a distance D = 1.0 mm from the fluid F and at a distance D = 4.0 mm.

[0079] 8A, when the magnetic powder concentration is 0 ppm, the count value of detector 4 (oscillation frequency of oscillator circuit OS) does not change substantially depending on the distance D0 between coil 2 and the inner surface of partition wall 3a. In contrast, when the magnetic powder concentration is 20,000 ppm, the count value of detector 4 at each distance D0 is different from the count value at a concentration of 0 ppm, and changes significantly depending on the distance D0. This demonstrates that the count value of detector 4 (frequency of oscillator circuit OS) is based on the magnetic powder concentration, and also shows that the value changes depending on the distance from partition wall 3a, i.e., from fluid F, to coil 2.

[0080] 8B also shows that there is a roughly proportional relationship between the difference in count values ​​obtained by the detector 4 for the coil 2 at two positions having a predetermined difference in distance from the fluid F and the concentration of the magnetic powder in the fluid F. Therefore, by using FIG. 8B as a relational expression or calibration curve that represents the relationship between the difference in frequency of the oscillator circuit OS obtained by the coils at two positions having different distances from the fluid F and the concentration of the magnetic powder in the fluid F, the concentration of the magnetic powder in the fluid F can be obtained from the detection results of the detector 4. By using the difference in the detection values ​​obtained by the coils at the two positions, it is thought that even if the characteristics of the coil 2 vary due to manufacturing variations, for example, it is possible to cancel out the variations and appropriately obtain the state of the magnetic powder, such as the concentration.

[0081] FIG. 8C also shows that the count value of detector 4, i.e., the oscillation frequency of the oscillator circuit OS including coil 2, changes with temperature. However, FIG. 8C also shows that the trend of change is substantially the same between coils 2 at two positions with different distances from fluid F. Therefore, by using the difference in the detection values ​​obtained by the coils at two positions with different distances from fluid F, it is possible to obtain the state of the magnetic powder, such as its concentration, from the detection results of detector 4 using a single calibration curve or relational expression, even if there is temperature fluctuation, for example, over the course of a year. Note that, since it is unlikely that the temperature of fluid F will fluctuate while coil 2 is moved between the first and second positions, the fact that the detection results of detector 4 have the temperature characteristics shown in FIG. 8C is unlikely to have any effect on obtaining the state of the magnetic powder according to the embodiment.

[0082] As described above, in the state acquisition device and state acquisition method of the embodiment, the coil is moved between two positions without exposing the coil or the moving part that moves the coil to the fluid, and the state of the magnetic powder can be acquired from the difference in values ​​based on the impedance of the coil detected at each position, so a strict sealing structure is not required, and it is thought that the state of the magnetic powder can be easily acquired using a simple device and little energy. In the state acquisition device and state acquisition method of the embodiment, as described above, the state of the magnetic powder may be acquired from the difference in values ​​based on the inductance of the coil detected at each of the two positions. [Explanation of symbols]

[0083] 1. Device for acquiring the status of magnetic powder (status acquisition device) 11 Connection 2, 2α, 2β coils 21 Shield 3. Housing 31 Part 1 32 Part 2 3a Bulkhead 3h opening 4. Detector 5. Processor 6 Driver 7 Moving parts 8 Capacitors Axial direction of AD coil D1: Distance between the coil surface at position P1 and the outer surface of the partition wall D2: Distance between the coil surface at position P2 and the outer surface of the partition wall F fluid M magnetic powder P1, P2 Coil first or second position

Claims

1. 1. An apparatus for acquiring the state of a magnetic particle in a surrounding fluid, the apparatus comprising: A coil and a housing that houses the coil; a detector for detecting a value based on the impedance of the coil; a processor for acquiring the state of the magnetic powder in the fluid from the detected value by the detector; Equipped with the housing is configured to prevent the fluid from entering the interior of the housing; the coil is held inside the housing so as to be movable between a first position and a second position in an axial direction of the coil, The processor is configured to obtain the state of magnetic powder in the fluid from the difference between the detection value for the coil at the first position and the detection value for the coil at the second position.

2. The apparatus further includes a driver that generates power to move the coil along the axial direction; The device according to claim 1 , wherein a moving part that transmits the power to the coil between the driver and the coil is accommodated in the housing together with the coil.

3. the housing has a partition wall facing the coil in the axial direction, The device of claim 1 , wherein the distance between the septum and the coil varies with movement of the coil along the axial direction.

4. The device of claim 3 , further comprising a shield formed of a material that is more ferromagnetic than the material of the partition wall and positioned on the opposite side of the coil from the partition wall so as to overlap the coil in the axial direction.

5. the housing has a first portion that is exposed to the fluid when the device is in use, and a second portion other than the first portion; The device according to claim 1 , wherein the second portion has a connection or opening used for electrical connection between the processor or the measuring device and an external device.

6. The apparatus of claim 1 , wherein the processor obtains a value corresponding to a concentration of magnetic powder in the fluid from a difference between the detection value for the coil at the first position and the detection value for the coil at the second position.

7. A method for acquiring a state of magnetic powder, the method comprising: disposing a coil at a first location in a space separated from the fluid to be measured by a housing placed in the fluid; Detecting a value based on the impedance of the coil at the first position; moving the coil from the first position to a second position along an axial direction of the coil; detecting a value based on the impedance of the coil at the second position; deriving an indication of the condition of magnetic powder using a difference between the detected value for the coil at the first position and the detected value for the coil at the second position; A method including:

8. the housing has a partition wall facing the coil in the axial direction, The method of claim 7 , wherein moving the coil to the second position comprises changing a distance between the septum and the coil.

9. 9. The method of claim 8, wherein moving the coil to the second position includes moving a shield along with the coil, the shield being positioned on an axially opposite side of the coil from the bulkhead.

10. The method of claim 7 , wherein the indicator is an indicator of the concentration of the magnetic powder.

Images