wireless communication system

Abstract

To provide a wireless communication system that can be widely applied independently of an inner structure of a rotary machine while suppressing reduction in electric field intensity.SOLUTION: In a wireless communication system, a motor 50 comprises: a wireless sensor unit 5 provided in a metal housing 51; a first passive relay 60 provided between the interior and the exterior of the metal housing 51; and a second passive relay 80 provided in the metal housing 51 to relay an electric wave transmitted from the wireless sensor unit 5 to the first passive relay 60. A reception antenna 85 of the second passive relay 80 is configured by a conductor provided on an antenna substrate 84a. A transmission antenna 81 of the second passive relay 80 is a directional antenna configured by a conductor provided on an antenna substrate 84b and having a single directivity in a horizontal plane of the concerned antenna substrate 84b. A reception antenna 65 of the first passive relay 60 is arranged on an extension plane of the horizontal plane of the antenna substrate 84b.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to wireless communication systems. [Background technology]

[0002] A bearing with a wireless sensor has been proposed that incorporates a wireless sensor unit containing various sensors such as a vibration sensor, acceleration sensor, rotation sensor, and temperature sensor, and outputs data acquired by the various sensors via wireless communication (for example, Patent Document 1).In a rotating machine to which such a bearing with a wireless sensor is applied, a wireless communication system that includes a non-powered repeater that relays radio waves between the inside and outside of the metal casing of the rotating machine has been disclosed as a technology for sending data measured by the wireless sensor unit to the outside (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-66433 [Patent Document 2] International Publication No. 2020 / 209206 Summary of the Invention [Problem to be solved by the invention]

[0004] In a wireless communication system using a parasitic repeater, it is necessary to suppress the propagation loss of radio waves in order to maintain a high electric field strength. In the above-mentioned conventional technology, the terminal part of the parasitic repeater inserted into the metal housing of the rotating machine is connected to the receiving antenna with a coaxial cable, and the receiving antenna of the parasitic repeater is positioned opposite the transmitting antenna of the wireless sensor unit, and the electromagnetic coupling effect of the near field generated between the transmitting antenna of the wireless sensor unit and the receiving antenna of the parasitic repeater is used to enhance the suppression effect of the propagation loss of the radio waves emitted from the wireless sensor unit. Alternatively, a second parasitic repeater that changes the transmission direction of the radio waves and repeats them between a first parasitic repeater that relays radio waves inside and outside the metal casing of the rotating machine and a wireless sensor unit is provided, and a terminal portion of the first parasitic repeater inserted into the metal casing of the rotating machine and a receiving antenna are connected by a coaxial cable, and the receiving antenna of the first parasitic repeater is arranged opposite the transmitting antenna of the second parasitic repeater, and the effect of suppressing the propagation loss of the radio waves radiated from the second parasitic repeater is enhanced by utilizing the electromagnetic coupling effect of the near field generated between the transmitting antenna of the second parasitic repeater and the receiving antenna of the first parasitic repeater. When a wireless communication system of this type is applied to a rotating machine such as a motor or a reducer, the routing of the coaxial cable inside the metal casing and the placement of the second parasitic repeater may be restricted by the internal structure of the metal casing, multipath fading due to reflections, etc.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication system that can reduce the size of a rotating machine in the axial direction while suppressing a decrease in electric field strength. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a wireless communication system according to one embodiment of the present invention comprises a wireless sensor unit provided inside a metal casing, a first unpowered repeater provided between the inside and outside of the metal casing, and a second unpowered repeater provided inside the metal casing and relaying radio waves transmitted from the wireless sensor unit to the first unpowered repeater, wherein the receiving antenna of the second unpowered repeater is formed by a conductor provided on a first board, the transmitting antenna of the second unpowered repeater is formed by a conductor provided on a second board different from the first board, and is a directional antenna having a unidirectional pattern within the horizontal plane of the second board, and the receiving antenna of the first unpowered repeater is arranged on an extension plane of the horizontal plane of the second board.

[0007] According to the above configuration, a wireless communication system can be obtained that can be widely applied regardless of the internal structure of a rotating machine while suppressing a decrease in electric field strength.

[0008] As a desirable aspect of the wireless communication system, the transmitting antenna of the second parasitic repeater is preferably configured with a plurality of layers of conductors provided on the second substrate.

[0009] As a desirable aspect of the wireless communication system, the transmitting antenna of the second parasitic repeater is preferably a log periodic antenna.

[0010] In a preferred embodiment of the wireless communication system, the transmitting antenna of the second parasitic repeater is a Huygens source antenna.

[0011] As a desirable aspect of the wireless communication system, the transmitting antenna of the wireless sensor is preferably constructed of a conductor provided on a substrate, and the first substrate is preferably arranged approximately parallel to the substrate on which the transmitting antenna of the wireless sensor unit is provided. [Effects of the Invention]

[0012] According to the present invention, a wireless communication system can be obtained that can reduce the size of a rotary machine in the axial direction while suppressing a decrease in electric field strength. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a bearing with a wireless sensor. [Figure 2] FIG. 2 is an exploded perspective view of the bearing with a wireless sensor. [Figure 3] FIG. 3 is a cross-sectional view of a portion of the bearing with wireless sensor, including the power generating portion and the protruding portion. [Figure 4] FIG. 4 is a cross-sectional view of a portion of the bearing with wireless sensor, including the power generating section and the recessed section. [Figure 5] FIG. 5 is a cross-sectional view of a portion of a bearing with a wireless sensor, including a sensor substrate. [Figure 6] FIG. 6 is an explanatory diagram for explaining the relationship between the voltage of the electromotive force and time in a bearing with a wireless sensor. [Figure 7] FIG. 7 is a plan view of the wireless sensor unit. [Figure 8] FIG. 8 is a perspective view of the cover. [Figure 9] FIG. 9 is a diagram showing an example of the internal configuration of a motor equipped with a bearing with a wireless sensor. [Figure 10] FIG. 10 is a diagram illustrating an application example of a wireless communication system according to a first example of a comparative example. [Figure 11] FIG. 11 is a diagram illustrating an application example of a wireless communication system according to a second example of the comparative example. [Figure 12] FIG. 12 is a diagram showing a specific example of a motor to which the wireless communication system according to the embodiment is applied. [Figure 13] FIG. 13 is a diagram showing the structure of an antenna substrate on which a receiving antenna of the second passive repeater is provided. [Figure 14A] FIG. 14A is a diagram showing the structure of an antenna substrate on which a transmitting antenna of a second passive repeater is provided. [Figure 14B] FIG. 14B is a diagram showing a conductor of a first layer of an antenna substrate on which a transmitting antenna of a second passive repeater is provided. [Figure 14C] FIG. 14C is a diagram showing a conductor of a second layer of the antenna substrate on which the transmitting antenna of the second parasitic repeater is provided. [Figure 15] FIG. 15 is a schematic structural diagram of a second passive repeater according to the embodiment. [Figure 16] FIG. 16 is a diagram illustrating an application example of a wireless communication system according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0015] First, a bearing with a wireless sensor will be described as an example to which the wireless sensor according to this embodiment is applied.

[0016] FIG. 1 is a perspective view of a bearing with a wireless sensor. FIG. 2 is an exploded perspective view of a bearing with a wireless sensor. FIG. 3 is a cross-sectional view of a portion of the bearing with a wireless sensor that includes a power generating section and a convex section. FIG. 4 is a cross-sectional view of a portion of the bearing with a wireless sensor that includes a power generating section and a concave section. FIG. 5 is a cross-sectional view of a portion of the bearing with a wireless sensor that includes a sensor board. The bearing with a wireless sensor 1 shown in FIG. 1 has a wireless sensor unit 5, a tone ring 30, and a bearing body 20, as shown in FIG. 2.

[0017] 3 to 5, the bearing body 20 is a rolling bearing having an outer ring 21, an inner ring 22, and rolling elements 23. The outer ring 21 and the inner ring 22 rotate relatively around a rotation axis Ax (see FIG. 1). In the following description, the inner ring 22 will be described as the rotating ring, but as long as the inner ring 22 and the outer ring 21 rotate relatively, it does not matter which one is rotating.

[0018] The cover 10 has an annular top plate 12 and a cylindrical side plate 11 connected to the periphery of the top plate 12. The cover 10 is made of a magnetic material such as silicon steel plate, carbon steel (JIS standard SS400 or S45C), martensitic stainless steel (JIS standard SUS420), or ferritic stainless steel (JIS standard SUS430).

[0019] 2, in the wireless sensor unit 5, a plurality of power generation units 3 and a substrate 40 are attached to one surface 12A of the top plate 12. The one surface 12A is the surface facing the bearing body 20. The substrate 40 has a power supply substrate 41 and a sensor substrate 42.

[0020] 1 and 2, for example, bolts 19A made of a non-magnetic material such as brass are fastened to female threaded holes in the top plate 12, thereby fixing the power generation unit 3 to the top plate 12. Similarly, bolts 19B made of a non-magnetic material such as brass are fastened to female threaded holes in the top plate 12, thereby fixing the power supply board 41 and the sensor board 42 to the top plate 12. As shown in FIG. 1, bolts 19A and 19B have a length such that they do not protrude from the cover 10 when attached to the cover 10.

[0021] The tone ring 30 has alternating convex portions 31 protruding outward from the outer diameter and concave portions 32 recessed inward from the convex portions 31 in the circumferential direction. The tone ring 30 has cylindrical protrusions 33 on its inner periphery that protrude toward the bearing body 20. The tone ring 30 is made of a magnetic material such as silicon steel plate, carbon steel (JIS standard SS400 or S45C), martensitic stainless steel (JIS standard SUS420), or ferritic stainless steel (JIS standard SUS430).

[0022] The power generation unit 3 has a permanent magnet 13, a yoke 14, and a coil 15. The permanent magnet 13 is fixed so as to be in contact with the top plate 12. The yoke 14 is fixed so as to be in contact with the permanent magnet 13. The yoke 14 only needs to be magnetically connected to the permanent magnet 13, and does not have to be directly connected. The yoke 14 is made of a magnetic material such as a silicon steel plate or a NiFe alloy. It is desirable that the yoke 14 be made of a material with magnetic permeability equal to or higher than that of the material of the cover 10, so as to increase the amount of magnetic flux inside the yoke 14. If the yoke 14 is made of a silicon steel plate, the magnetic permeability will be high, making it easier for magnetic flux to pass through the yoke 14.

[0023] The coils 15 are so-called magnet wires in which a conducting wire is wound around the yoke 14. The coils 15 of adjacent power generation units 3 are connected in series, and wiring drawn from the coils 15 of the plurality of series-connected power generation units 3 is connected to the power supply board 41.

[0024] As shown in Figure 3, one end of the side plate 11 is fitted into and fixed to a groove 21A provided on the outer periphery of the outer ring 21. The cylindrical protrusion 33 is fitted into and fixed to a groove 22A provided on the inner periphery of the inner ring 22. As a result, as shown in Figures 3 and 4, the inner end faces of the yoke 14 and the top plate 12 are positioned opposite the protrusions 31 and recesses 32 of the tone ring 30. The cover 10 and the tone ring 30 can then be easily attached to the bearing body 20.

[0025] The magnetic field of permanent magnet 13 causes magnetic flux Mf to pass through yoke 14, protrusion 31 or recess 32 of tone ring 30, and top plate 12 of cover 10. Therefore, permanent magnet 13, yoke 14, protrusion 31 or recess 32 of tone ring 30, and top plate 12 of cover 10 form a magnetic circuit.

[0026] As shown in FIG. 5 , a magnetic body 311 exhibiting stronger magnetism than the tone ring 30 is attached to a portion of the outer peripheral end face 31IF of the protrusion 31. For example, a recess corresponding to the shape and size of the magnetic body is provided in the outer peripheral end face 31IF of the protrusion 31. The magnetic body 311 is fitted into this recess. The magnetic body 311 and the outer peripheral end face 31IF around the magnetic body 311 are flush or nearly flush with each other. The magnetic body 311 is, for example, a hard magnetic permanent magnet. The magnetic body 311 is attached to only one location on the tone ring 30. With each rotation (360° rotation) of the inner ring 22 relative to the outer ring 21, the magnetic body 311 comes closest to the angle sensor 443. The angle sensor 443 includes, for example, a Hall element.

[0027] FIG. 6 is an explanatory diagram illustrating the relationship between the voltage of the electromotive force and time in a bearing with a wireless sensor. The horizontal axis in FIG. 6 represents time T, and the vertical axis represents the voltage Vi of the electromotive force. As the outer ring 21 is fixed and the inner ring 22 rotates, the tone ring 30 rotates along with the inner ring 22, causing the tone ring 30 and the power generator 3 to rotate relative to each other. For the yoke 14, the air gap from the inner peripheral end face to the outer peripheral end face 31IF of the protrusion 31 shown in FIG. 3 alternates with the air gap from the inner peripheral end face to the outer peripheral end face 32IF of the recess 32 shown in FIG. 4.

[0028] In this way, the convex portions 31 and concave portions 32 on the outer periphery of the tone ring 30 cause the distance between the yoke 14 of the power generation unit 3 and the outer periphery of the tone ring 30 to periodically change. This causes a change in the density of the magnetic flux Mf generated in the power generation unit 3. When the yoke 14, which includes the permanent magnet 13, and the tone ring 30 are close to each other, the magnetic flux Mf passing through the permanent magnet 13, yoke 14, and tone ring 30 is large; when the yoke 14 and the tone ring 30 are farther apart, the magnetic flux Mf passing through the permanent magnet 13, yoke 14, and tone ring 30 is small. This change in the density of the magnetic flux Mf generates a voltage change in the coil 15, which is made of magnet wire wound around the yoke 14.

[0029] That is, when the yoke 14 and the outer peripheral end surface 31IF of the protrusion 31 are closest to each other, the magnetic flux Mf shown in Fig. 3 becomes larger, and the electromotive force voltage V1 shown in Fig. 6 is supplied to the power supply board 41. When the yoke 14 and the outer peripheral end surface 32IF of the recess 32 are farthest from each other, the magnetic flux Mf shown in Fig. 4 becomes smaller, and the electromotive force voltage V2 shown in Fig. 6 is supplied to the power supply board 41.

[0030] FIG. 7 is a plan view of the wireless sensor unit. As shown in FIG. 7, a power supply unit 43 is mounted on a power supply board 41. The power supply unit 43 converts single-phase AC power supplied from the power generation unit 3 into DC voltage and supplies it to a sensor board 42. A sensor 44, a control unit 45 having a communication circuit, and a transmitting antenna 47 are mounted on the sensor board 42. DC power from the power supply unit 43 is supplied to the sensor 44 and the control unit 45. The sensor 44, the control unit 45, and the transmitting antenna 47 may be configured on separate IC (Integrated Circuit) chips, or some or all of them may be configured on a single IC chip. The sensor 44 includes, for example, an acceleration sensor 441, a temperature sensor 442, and an angle sensor 443. The sensor 44 may be any one or two of the acceleration sensor 441, the temperature sensor 442, and the angle sensor 443 described above, or may be a sensor that measures other physical quantities.

[0031] FIG. 8 is a perspective view of the cover. As shown in FIG. 8, a through-hole 12H is formed in the cover 10. As shown in FIG. 1, the through-hole 12H is sealed with a non-magnetic lid 17 made of a non-magnetic material such as resin. As described above, the cover 10 is provided with the transmitting antenna 47 on the bearing body 20 side. Here, the cover 10 is magnetic, and therefore has the effect of shielding electromagnetic waves from the transmitting antenna 47. For this reason, as shown in FIG. 7, the transmitting antenna 47 is arranged to overlap the non-magnetic lid 17 in a plan view seen from the direction of the rotation axis Zr of the bearing body 20. In other words, the non-magnetic lid 17 is provided on a portion of the cover 10 facing the transmitting antenna 47. For this reason, the electromagnetic waves WV from the transmitting antenna 47 can reach the communication unit 151 via the non-magnetic lid 17.

[0032] 8, one surface 12A of the top plate 12 is provided with a plurality of recesses 18 for arranging the power generation unit 3. For example, each of the plurality of recesses 18 has a first recess 18A for arranging the coil 15 and a second recess 18B for arranging the permanent magnet 13. When the one surface 12A is taken as the reference plane, the first recess 18A is deeper than the second recess 18B.

[0033] The control unit 45 has a function of converting various data detected by the sensor 44 from analog data to digital data (for example, A / D conversion) and storing the data. The control unit 45 also has a function of transmitting the stored digital data to the outside via a transmission antenna 47. The control unit 45 operates using DC power supplied from the power supply unit 43.

[0034] The digital data transmitted from the wireless sensor unit 5 is received by the communication unit 151 of the higher-level device 150 shown in Figure 1. The digital data received by the communication unit 151 is processed by the computer 152. In this way, the bearing with wireless sensor 1 can transmit digital data wirelessly, which allows for miniaturization.

[0035] In addition to the above-described wireless sensor bearing 1, the wireless sensor according to this embodiment also includes a spacer-type wireless sensor module that is installed near the bearing. Below, a wireless communication system using a wireless sensor such as the above-described wireless sensor bearing 1 or wireless sensor module will be described. Note that the following description includes components that are substantially the same as the configuration of the wireless sensor bearing 1 and host device 150 described in Figures 1 to 8.

[0036] In this embodiment, a specific example of application of the wireless communication system to a motor equipped with a bearing equipped with a wireless sensor will be described. Fig. 9 is a diagram showing an example of the internal configuration of a motor equipped with a bearing equipped with a wireless sensor. Note that components that are the same as those in the configuration described above are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, the rotating machine to which the wireless communication system according to this embodiment is applied is not limited to a motor, and may be, for example, a reducer equipped with a bearing equipped with a wireless sensor.

[0037] The motor 50 basically comprises a metal housing 51, a rotor 52, a stator 53, and an output shaft 54.

[0038] The rotor 52 and the output shaft 54 ​​are rotatably held relative to the metal casing 51 and the stator 53 of the motor 50. The bearing with wireless sensor 1 is provided on the load side of the output shaft 54 ​​to which a rotation-controlled object 100 of the motor 50 is mechanically connected. In this embodiment, the rotation-controlled object 100 of the motor 50 (hereinafter also referred to as the "load") is a rotating machine such as a pump or a reducer.

[0039] The wireless sensor unit 5 is provided on the inside of the load-side bearing body 20 in the direction of the rotation axis Ax. The transmitting antenna 47 of the wireless sensor unit 5 is made up of a conductor provided on the sensor substrate 42. The transmitting antenna 47 is made up of, for example, one of a pattern antenna, a microstrip patch antenna, and a chip antenna. The transmitting antenna 47 is arranged so that the strength of the radio waves it radiates is greatest in the vertical direction of the sensor substrate 42 (the direction of the arrow in Figure 9), and the maximum radiation direction of the radio waves faces inward in the direction of the rotation axis Ax.

[0040] When the wireless communication system according to the embodiment is applied to the motor 50 shown in FIG. 9, the elements of the wireless communication system are provided in a space A on the load side of the output shaft 54 ​​inside the metal casing 51, where the bearing with wireless sensor 1 is provided.

[0041] Fig. 10 is a diagram showing an application example of a wireless communication system according to a first example of a comparative example. The same components as those in Fig. 9 are given the same reference numerals, and duplicated explanations will be omitted.

[0042] In the motor 50 configured as shown in Fig. 9, the parasitic repeater 60 cannot be provided on an extension of the radiation direction (inward in the direction of the rotation axis Ax) of the radio waves from the transmitting antenna 47 of the wireless sensor unit 5. For this reason, in the example shown in Fig. 10, the parasitic repeater 60 has a terminal portion 62 inserted into a hole provided on the top surface of the metal casing 51. In other words, the radiation direction of the radio waves from the wireless sensor unit 5 and the drilling direction of the hole in the metal casing 51 through which the terminal portion 62 of the parasitic repeater 60 is inserted are different.

[0043] The transmitting antenna 61 of the parasitic repeater 60 is provided outside the metal housing 51. The transmitting antenna 61 can be configured, for example, as a dipole antenna or a monopole antenna.

[0044] The receiving antenna 65 of the parasitic repeater 60 is configured, for example, by a conductor provided on a resin antenna substrate 64, and is provided inside the metal housing 51. The receiving antenna 65 can be configured, for example, by a pattern antenna or a microstrip patch antenna, and has maximum receiving sensitivity in the vertical direction of the antenna substrate 64. In a first example of the comparative example shown in FIG. 10 , the receiving antenna 65 of the parasitic repeater 60 is arranged at a position where the maximum sensitivity direction substantially coincides with the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5.

[0045] The terminal portion 62 and the antenna substrate 64 are connected by, for example, a coaxial cable 63. That is, the transmitting antenna 61 and the receiving antenna 65 are connected via the terminal portion 62 and the coaxial cable 63. The antenna substrate 64 and the coaxial cable 63 are connected by, for example, an SMA connector or a U.FL connector. The coaxial cable 63 is, for example, a coaxial cable with a diameter of about 1.37 mm that is compatible with these SMA connectors and U.FL connectors.

[0046] 10, the receiving antenna 65 of the parasitic repeater 60 is disposed opposite the transmitting antenna 47 of the wireless sensor unit 5. As a result, the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 and the maximum sensitivity direction of the receiving antenna 65 of the parasitic repeater 60 are approximately aligned.

[0047] Furthermore, by positioning the receiving antenna 65 of the parasitic repeater 60 at a position where the distance d from the transmitting antenna 47 of the wireless sensor unit 5 is λ / 2π or less, where λ is the wavelength of the fundamental wave of the radio wave, it is possible to utilize the electromagnetic coupling effect of the near field that occurs between the transmitting antenna 47 of the wireless sensor unit 5 and the receiving antenna 65 of the parasitic repeater 60.

[0048] FIG. 11 is a diagram illustrating an application example of a wireless communication system according to a second example of the comparative example.

[0049] The first parasitic repeater 60 corresponds to the parasitic repeater 60 shown in Fig. 10. In the example shown in Fig. 11, a second parasitic repeater 80 is provided inside a metal housing 51.

[0050] The receiving antenna 85 of the second parasitic repeater 80 and the transmitting antenna 81 of the second parasitic repeater 80 are configured with conductors provided on an antenna substrate 84 made of, for example, resin. In a second example of the comparative example shown in FIG. 11 , the receiving antenna 85 and the transmitting antenna 81 are configured with, for example, a pattern antenna or a microstrip patch antenna, and the receiving sensitivity is maximized in the vertical direction of the antenna substrate 84. The second parasitic repeater 80 is disposed at a position where the maximum sensitivity direction of the receiving antenna 85 substantially coincides with the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5, and the maximum radiation direction of the transmitting antenna 81 substantially coincides with the maximum sensitivity direction of the receiving antenna 65 of the first parasitic repeater 60. The receiving antenna 85 and the transmitting antenna 81 may be provided on separate substrates, and the substrates may be connected to each other by coaxial cables.

[0051] 11, the receiving antenna 85 of the second parasitic repeater 80 is disposed opposite the transmitting antenna 47 of the wireless sensor unit 5. As a result, the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 and the maximum sensitivity direction of the receiving antenna 85 of the second parasitic repeater 80 are approximately aligned.

[0052] Furthermore, the transmitting antenna 81 of the second parasitic repeater 80 is disposed opposite the receiving antenna 65 of the first parasitic repeater 60. As a result, the maximum radiation direction of the transmitting antenna 81 of the second parasitic repeater 80 and the maximum sensitivity direction of the receiving antenna 65 of the first parasitic repeater 60 are approximately aligned.

[0053] In addition, by positioning the receiving antenna 85 of the second unpowered repeater 80 at a position where the distance d1 from the transmitting antenna 47 of the wireless sensor unit 5 is λ / 2π or less, it is possible to utilize the near-field electromagnetic coupling effect that occurs between the transmitting antenna 47 of the wireless sensor unit 5 and the receiving antenna 85 of the second unpowered repeater 80.

[0054] Furthermore, by positioning the transmitting antenna 81 of the second unpowered repeater 80 and the receiving antenna 65 of the first unpowered repeater 60 at a position where the distance d2 between them is λ / 2π or less, where λ is the wavelength of the fundamental wave of the radio wave, it is possible to utilize the electromagnetic coupling effect of the near field that occurs between the transmitting antenna 81 of the second unpowered repeater 80 and the receiving antenna 65 of the first unpowered repeater 60.

[0055] As described above, in the first comparative example shown in FIG. 10 and the second comparative example shown in FIG. 11, the transmitting antenna 61 and the receiving antenna 65 of the first parasitic repeater 60 are connected via the terminal portion 62 and the coaxial cable 63 in the space A on the load side of the output shaft 54 ​​in which the wireless sensor-equipped bearing 1 is provided inside the metal casing 51. In such an embodiment, the routing of the coaxial cable 63 and the arrangement of the second parasitic repeater 80 in the second comparative example shown in FIG. 11 are limited by the structures of the metal casing 51, the rotor 52, and the stator 53 (for example, ribs provided on the metal casing 51, windings of the rotor 52, or magnets of the stator 53). In particular, in the second comparative example shown in FIG. 11, the second parasitic repeater 80 has a substantially L-shaped structure, which increases the size of the rotating machine in the rotational axis direction, thereby limiting the rotating machines to which the wireless communication system can be applied.

[0056] Fig. 12 is a diagram showing an application example of the wireless communication system according to the embodiment. Note that the same components as those in Fig. 11 are given the same reference numerals, and duplicated explanations will be omitted. The wireless communication system according to the embodiment differs from the second example of the comparative example shown in Fig. 11 in the configuration of the second parasitic repeater 80.

[0057] In the configuration shown in Figure 12, the receiving antenna 85 of the second unpowered repeater 80 is composed of a conductor provided on, for example, a resin antenna substrate 84a (first substrate), and is an antenna whose receiving sensitivity is greatest in the vertical direction of the antenna substrate 84a (first substrate).

[0058] Fig. 13 is a diagram showing the structure of an antenna substrate on which a receiving antenna of a second parasitic repeater is provided. The antenna substrate 84a (first substrate) on which a receiving antenna 85 of the second parasitic repeater 80 is provided is configured, for example, by a flexible printed circuit board (FPC) made of a polyimide resin. In the example shown in Fig. 13, the receiving antenna 85 of the second parasitic repeater 80 is a spiral antenna configured by a conductor provided on the antenna substrate 84a (first substrate). Feed points 86a and 86b of the receiving antenna 85 of the second parasitic repeater 80 are provided with, for example, an SMA connector or a U.FL connector, and are connected to the transmitting antenna 81 via a coaxial cable (not shown) or a transmission line 88 described later in Fig. 15.

[0059] The antenna substrate 84a (first substrate) on which the receiving antenna 85 of the second parasitic repeater 80 is provided is disposed substantially parallel to and facing the substrate on which the transmitting antenna 47 of the wireless sensor unit 5 is provided, similar to the second example of the comparative example shown in Fig. 11. This causes the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 (the direction indicated by arrow b in Fig. 12) and the maximum sensitivity direction of the receiving antenna 85 of the second parasitic repeater 80 to substantially coincide.

[0060] The receiving antenna 85 of the second passive repeater 80 is not limited to the spiral antenna shown in FIG. 13, but may be any antenna that maximizes the receiving sensitivity in the vertical direction of the antenna substrate 84a (first substrate).

[0061] In addition, in the configuration shown in Figure 12, the transmitting antenna 81 of the second unpowered repeater 80 is composed of a conductor provided on an antenna substrate 84b (second substrate) which is composed of, for example, a high-frequency multilayer substrate, and is a directional antenna having unidirectionality within the horizontal plane of the antenna substrate 84b (second substrate).

[0062] The receiving antenna 65 of the first parasitic repeater 60 is arranged on an extension plane (a plane including the direction of arrow a in FIG. 12) of the horizontal plane of the antenna substrate 84b (second substrate) on which the transmitting antenna 81 of the second parasitic repeater 80 is provided. A specific embodiment of the transmitting antenna 81 of the second parasitic repeater 80 will be described below.

[0063] FIG. 14A is a diagram showing the structure of an antenna substrate on which a transmitting antenna of a second parasitic repeater is provided. FIG. 14A is a diagram seen from the right side of FIG. 12, and furthermore, the upper side of FIG. 12 corresponds to the left side. The antenna substrate 84b (second substrate) has at least two conductor layers. The transmitting antenna 81 of the second parasitic repeater 80 includes, for example, a first-layer conductor 81a of the antenna substrate 84b (second substrate) shown by a solid line in FIG. 14A and a second-layer conductor 81b of the antenna substrate 84b (second substrate) shown by a dashed line in FIG. 14A. The first-layer conductor 81a of the antenna substrate 84b (second substrate) shown by a solid line in FIG. 14A and the second-layer conductor 81b of the antenna substrate 84b (second substrate) shown by a dashed line in FIG. 14A are laminated. FIG. 14B is a diagram showing a first-layer conductor of the antenna substrate on which a transmitting antenna of a second parasitic repeater is provided. FIG. 14C is a diagram showing a conductor of a second layer of the antenna substrate on which the transmitting antenna of the second parasitic repeater is provided.

[0064] In the examples shown in Figures 14A, 14B, and 14C, the transmitting antenna 81 of the second parasitic repeater 80 is a log periodic antenna (logarithmic periodic antenna) made up of a conductor provided on the antenna substrate 84b (second substrate).

[0065] The log periodic antennas in the aspects shown in FIGS. 14A, 14B, and 14C satisfy the relationships of the following formulas (1) and (2).

[0066] l n+1 / l n =x n+1 / x n ···(1)

[0067] α=tan -1(l n / x n )···(2)

[0068] In the above formulas (1) and (2), n=1, 2, 3, 4 in the embodiments shown in FIGS. 14A, 14B, and 14C.

[0069] 14A, 14B, and 14C, the conductor constituting the transmitting antenna 81 of the second parasitic repeater 80 is, for example, an 18 μm copper foil pattern provided on an antenna substrate 84b (second substrate) that is 46 mm long, 18 mm wide, and 0.5 mm thick, as shown in FIGS. 14A, 14B, and 14C. Examples of communication standards used in the present disclosure include short-range wireless communication standards such as 2.4 GHz band BLE (Bluetooth LE, Bluetooth Low Energy). This makes it possible to fabricate a small antenna suitable for use in the space A on the load side of the output shaft 54 ​​where the wireless sensor-equipped bearing 1 is provided inside the metal housing 51.

[0070] The antenna substrate 84b (second substrate) on which the transmitting antenna 81 of the second parasitic repeater 80 is provided is made of, for example, a Teflon (registered trademark) rigid substrate. This makes it possible to suppress the dielectric constant in the high frequency range. The antenna substrate 84b (second substrate) may also be configured to contain additives such as glass fiber or fused silica. This makes it possible to improve thermal and electrical characteristics.

[0071] A feed point 82a of the conductor 81a and a feed point 82b of the conductor 81b are provided with, for example, an SMA connector or a U.FL connector, and are connected to a receiving antenna 85 via a coaxial cable.

[0072] 11, the receiving antenna 65 of the first parasitic repeater 60 is an antenna that is configured of a conductor provided on an antenna substrate 64 made of, for example, resin, and has maximum receiving sensitivity in the vertical direction of the antenna substrate 64. The first parasitic repeater 60 is disposed at a position where the maximum sensitivity direction of the receiving antenna 65 substantially coincides with the maximum radiation direction of the transmitting antenna 81 of the second parasitic repeater 80 (the direction indicated by arrow a in FIG. 12).

[0073] The form of the transmitting antenna 81 of the second parasitic repeater 80 is not limited to the forms shown in Figures 14A, 14B, and 14C, and may also be, for example, a Huygens Source Antenna of the form described in the following paper.

[0074] P. Jin and RW Ziolkowski, “Metamaterial-Inspired, Electrically Small Huygens Sources,” in IEEE Antennas and Wireless Propagation Letters, vol. 9, pp. 501-505, May 2010.

[0075] In the above-described embodiment, the antenna substrate 84a (first substrate) on which the receiving antenna 85 of the second parasitic repeater 80 is provided and the antenna substrate 84b (second substrate) on which the transmitting antenna 81 of the second parasitic repeater 80 is provided are arranged in close proximity to each other and substantially parallel to each other. This makes it possible to reduce the size of the second parasitic repeater 80 in the direction of the rotation axis Ax compared to the configuration of the second example of the comparative example shown in Fig. 11, thereby expanding the application range of the wireless communication system according to the present disclosure.

[0076] Fig. 15 is a schematic structural diagram of a second parasitic repeater according to an embodiment. In the example shown in Fig. 15, an antenna substrate 84a (first substrate) on which a transmitting antenna 81 of a second parasitic repeater 80 is provided and an antenna substrate 84b (second substrate) on which a receiving antenna 85 of the second parasitic repeater 80 is provided are fitted into a resin bracket 87 (resin member) so as to be approximately parallel to each other. Note that the bracket 87 (resin member) may be configured in any manner as long as it maintains insulation between the conductors (copper foil patterns) of both the antenna substrate 84a (first substrate) and the antenna substrate 84b (second substrate). This allows the antenna substrate 84a (first substrate) and the antenna substrate 84b (second substrate) to be held in a state in which they are arranged closely to each other and approximately parallel to each other.

[0077] The transmitting antenna 81 and the receiving antenna 85 are connected by a transmission line 88 provided on a bracket 87. In the example shown in Fig. 15, the transmission line 88 may be, for example, a coaxial cable or a waveguide, as described above. Alternatively, the transmission line 88 may be formed by embedding a rod-shaped or plate-shaped conductor in the bracket 87, and the transmitting antenna 81 and the receiving antenna 85 are connected by this conductor. In this case, it is preferable that the conductor is formed in a gentle curve without any acute bends.

[0078] In the above-described configuration, the antenna board 84a (first board) on which the receiving antenna 85 of the second parasitic repeater 80 is provided is arranged approximately parallel to the board on which the transmitting antenna 47 of the wireless sensor unit 5 is provided so that the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 and the maximum sensitivity direction of the receiving antenna 85 of the second parasitic repeater 80 coincide (the direction indicated by arrow b in Figure 12), and the receiving antenna 85 of the second parasitic repeater 80 is arranged in a position where the distance from the transmitting antenna 47 of the wireless sensor unit 5 is λ / 2π or less.This makes it possible to utilize the electromagnetic coupling effect of the near field that occurs between the transmitting antenna 47 of the wireless sensor unit 5 and the receiving antenna 85 of the second parasitic repeater 80, and to suppress the propagation loss of the radio waves radiated from the transmitting antenna 47 of the wireless sensor unit 5.

[0079] Furthermore, as shown in Fig. 12, the receiving antenna 65 of the first parasitic repeater 60 is mounted on a plane extending from the horizontal plane of the antenna substrate 84b (second substrate) on which the transmitting antenna 81 of the second parasitic repeater 80 is provided (a plane including the direction of arrow a in Fig. 12). As described above, by arranging the receiving antenna 65 of the first parasitic repeater 60 in the maximum radiation direction (the direction of arrow a in Fig. 12) of the transmitting antenna 81 of the second parasitic repeater 80, which has unidirectionality within the horizontal plane of the antenna substrate 84b (second substrate), the multipath fading phenomenon caused by reflection within the metal housing 51 of the radio waves radiated from the transmitting antenna 81 of the second parasitic repeater 80 is suppressed. This makes it possible to suppress the propagation loss of the radio waves radiated from the transmitting antenna 81 of the second parasitic repeater 80.

[0080] Furthermore, in the above-described configuration, by arranging the antenna board 84a (first board) on which the receiving antenna 85 of the second parasitic repeater 80 is provided and the antenna board 84b (second board) on which the transmitting antenna 81 is provided approximately parallel to each other, the second parasitic repeater 80 can be made more compact than the second example of the comparative example shown in Figure 11.

[0081] Fig. 16 is a diagram showing an application example of a wireless communication system according to a modified example of the embodiment. Fig. 12 shows an example in which the first parasitic repeater 60 is provided on an extension line of the radiation direction of radio waves from the transmitting antenna 81 of the second parasitic repeater 80. However, as shown in Fig. 16, an insertion hole for inserting the first parasitic repeater 60 may be provided at a position off an extension plane (a plane including the direction of arrow a) of the horizontal plane of an antenna substrate 84b (second substrate) on which the transmitting antenna 81 of the second parasitic repeater 80 is provided, and the transmitting antenna 61 and receiving antenna 65 of the first parasitic repeater 60 may be connected via a terminal portion 62 and a coaxial cable 63.

[0082] The configuration of the above-described embodiment provides a wireless communication system that can be widely applied regardless of the internal structure of a rotating machine while suppressing a decrease in electric field strength.

[0083] The figures used above are conceptual diagrams for qualitatively explaining the present disclosure, and are not intended to be limiting. Furthermore, while the above-described embodiment is an example of a preferred implementation of the present disclosure, the present disclosure is not limited thereto, and various modifications can be made without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0084] 1. Bearings with wireless sensors 5 Wireless Sensor Unit 10 Cover 20 Bearing body 21 outer ring 22 Inner Circle 40 boards 41 Power supply board 42 Sensor board 43 Power supply section 44 sensors 45 Control Unit 47 Transmitting antenna (wireless sensor unit) 50 motor 51 Metal Case 52 rotor 53 Stator 54 Output shaft 60 Unpowered Repeater (First Unpowered Repeater) 61 Transmitting antenna (parallel repeater, first parallax repeater) 62 Terminal section 63 Coaxial Cable 64 Antenna board 65 Receiving antenna (parasitic repeater, first parasitic repeater) 80 Second unpowered repeater 81 Transmitting antenna (second non-powered repeater) 81a, 81b conductor 82a, 82b feeding points 84a Antenna board (first board) 84b Antenna board (second board) 85 Receiving antenna (second non-powered repeater) 86a, 86b power supply points 87 Bracket (resin part) 88 Transmission Line 100 Rotation control target 150 Upper device 151 Communications Department 152 Computer 441 Acceleration Sensor 442 Temperature Sensor 443 Angle Sensor

Claims

1. A rotary machine includes a shaft, a metal housing, and a bearing that rotatably holds the shaft relative to the metal housing. The rotary machine includes a wireless sensor unit that is located inside the metal housing and in the vicinity of the bearing, and that transmits data detected by a sensor indicating the state of the bearing via a transmitting antenna. a first passive repeater provided between the inside and the outside of the metal housing; a second passive repeater provided inside the metal housing and configured to relay radio waves transmitted from the wireless sensor unit to the first passive repeater; Equipped with the receiving antenna of the second parasitic repeater is an antenna formed of a conductor provided on a first substrate, and having a maximum receiving sensitivity in a direction perpendicular to the first substrate; a transmitting antenna of the second parasitic repeater is a directional antenna formed of a conductor provided on a second substrate different from the first substrate, and having unidirectionality in a direction parallel to the second substrate; the maximum radiation direction of the radio waves emitted from the transmitting antenna of the wireless sensor unit is parallel to the rotation axis of the shaft; a receiving antenna of the second parasitic repeater is arranged in a maximum radiation direction of radio waves radiated from a transmitting antenna of the wireless sensor unit; the first substrate and the second substrate are disposed on a plane perpendicular to the rotation axis of the shaft, and are disposed in close proximity to each other and substantially parallel to each other at overlapping positions when viewed from a direction parallel to the rotation axis of the shaft; The receiving antenna of the first parasitic repeater is arranged in the maximum radiation direction of the radio wave radiated from the transmitting antenna of the second parasitic repeater. Wireless communication system.

2. The transmitting antenna of the second parasitic repeater is composed of a plurality of layers of conductors provided on the second substrate.

10. The wireless communication system of claim 1.

3. The transmitting antenna of the second parasitic repeater is a log periodic antenna.

3. The wireless communication system according to claim 2.

4. The transmitting antenna of the second parasitic repeater is a Huygens source antenna.

3. The wireless communication system according to claim 2.

5. a transmitting antenna of the wireless sensor unit is formed by a conductor provided on a substrate; The first substrate is disposed substantially parallel to a substrate on which a transmitting antenna of the wireless sensor unit is provided. A wireless communication system according to any one of claims 1 to 4.

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