JP7735783B2 - wireless communication system - Google Patents

Description

The present invention relates to a wireless communication system.

Such bearings with wireless sensors have been proposed, each of which 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 (see, for example, Patent Document 1). In rotating machines that use such bearings with wireless sensors, a wireless communication system has been disclosed that includes a non-powered repeater that relays radio waves between the inside and outside of the metal casing of the rotating machine, as a technique for sending data measured by the wireless sensor unit to an external device (see, for example, Patent Document 2).

JP 2018-66433 A International Publication No. 2020/209206

In wireless communication systems using parasitic repeaters, it is necessary to suppress radio wave propagation loss in order to maintain high field strength. In the above-mentioned conventional technology, a coaxial cable is used to connect the terminal of the parasitic repeater, which is inserted into the metal casing of the rotating machine, to the receiving antenna, and the receiving antenna of the parasitic repeater is positioned opposite the transmitting antenna of the wireless sensor unit. This utilizes the near-field electromagnetic coupling that occurs between the transmitting antenna of the wireless sensor unit and the receiving antenna of the parasitic repeater to effectively suppress propagation loss of the radio waves emitted from the wireless sensor unit. Alternatively, a second parasitic repeater is provided between a first parasitic repeater that relays radio waves between the inside and outside of the metal casing of the rotating machine and a wireless sensor unit, and the second parasitic repeater changes the transmission direction of the radio waves and relays them. The terminal of the first parasitic repeater inserted into the metal casing of the rotating machine is connected to the receiving antenna with a coaxial cable, and the receiving antenna of the first parasitic repeater is positioned opposite the transmitting antenna of the second parasitic repeater. The near-field electromagnetic coupling between the transmitting antenna of the second parasitic repeater and the receiving antenna of the first parasitic repeater is utilized to effectively suppress propagation loss of the radio waves emitted from the second 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 limited by multipath fading caused by the internal structure and reflections of the metal casing.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a wireless communication system that can be widely applied regardless of the internal structure of the rotating machine while suppressing a decrease in electric field strength.

To achieve the above object, one aspect of the present invention provides a wireless communication system comprising: a wireless sensor unit provided inside a metal housing; a first parasitic repeater provided between the inside and outside of the metal housing; and a second parasitic repeater provided inside the metal housing and relaying radio waves transmitted from the wireless sensor unit to the first parasitic repeater; the receiving antenna of the second parasitic repeater is formed of a conductor provided on a substrate; the transmitting antenna of the second parasitic repeater is formed of a conductor provided on the substrate and is a directional antenna with unidirectionality within the horizontal plane of the substrate; the transmitting antenna of the second parasitic repeater and the receiving antenna of the second parasitic repeater are offset from each other at different positions when viewed from a direction perpendicular to at least the horizontal plane of the substrate on which the transmitting antenna of the second parasitic repeater is provided; and the receiving antenna of the first parasitic repeater is located on an extension of the horizontal plane of the substrate on which the transmitting antenna of the second parasitic repeater is provided.

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

A desirable aspect of the wireless communication system is that the board on which the receiving antenna of the second parasitic repeater is mounted and the board on which the transmitting antenna of the second parasitic repeater is mounted are embedded in a resin member, and the receiving antenna and transmitting antenna of the second parasitic repeater are connected by a transmission path provided in the resin member.

In a preferred embodiment of the wireless communication system, the transmission path is a coaxial cable.

In a preferred embodiment of the wireless communication system, the transmission path is a waveguide.

A desirable aspect of the wireless communication system is that the receiving antenna of the second parasitic repeater and the transmitting antenna of the second parasitic repeater are mounted on the same substrate, and that the receiving antenna of the second parasitic repeater and the transmitting antenna of the second parasitic repeater are connected by a conductor mounted on the substrate.

In a preferred embodiment of the wireless communication system, the transmitting antenna of the wireless sensor is composed of a conductor mounted on a substrate, and it is preferable that the substrate on which at least the receiving antenna of the second parasitic repeater is mounted is arranged approximately parallel to the substrate on which the transmitting antenna of the wireless sensor unit is mounted.

The present invention 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.

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, including the power generating portion and the protruding portion. FIG. 4 is a cross-sectional view of a portion of the bearing with a wireless sensor, including the power generating section and the recessed section. FIG. 5 is a cross-sectional view of a portion of a bearing with a wireless sensor, including a sensor substrate. 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. FIG. 7 is a plan view of the wireless sensor unit. FIG. 8 is a perspective view of the cover. FIG. 9 is a diagram showing an example of the internal configuration of a motor equipped with a bearing with a wireless sensor. FIG. 10 is a diagram illustrating an application example of a wireless communication system according to a first example of a comparative example. FIG. 11 is a diagram illustrating an application example of a wireless communication system according to a second example of the comparative example. FIG. 12 is a diagram showing a specific example of a motor to which the wireless communication system according to the embodiment is applied. FIG. 13 is a diagram illustrating an application example of a wireless communication system according to a modified example of the embodiment. FIG. 14 is a schematic structural diagram of a second passive repeater according to the embodiment. FIG. 15 is a schematic structural diagram of a second passive repeater according to a first modified example of the embodiment. FIG. 16 is a schematic structural diagram of a second parasitic repeater according to a second modified example of the embodiment. FIG. 17 is a schematic structural diagram of a second parasitic repeater according to a third modified example of the embodiment.

The following describes in detail modes for carrying out the invention (hereinafter referred to as "embodiments") 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 would 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.

First, we will explain a bearing with a wireless sensor as an example of an application of the wireless sensor according to this embodiment.

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

As shown in Figures 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 the rotation axis Ax (see Figure 1). In the following, 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 relative to each other, it does not matter which one is rotating.

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).

As shown in FIG. 2, in the wireless sensor unit 5, multiple 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.

For example, as shown in Figures 1 and 2, the power generation unit 3 is fixed to the top plate 12 by fastening a bolt 19A made of a non-magnetic material such as brass into a female threaded hole drilled in the top plate 12. Similarly, the power supply board 41 and sensor board 42 are fixed to the top plate 12 by fastening a bolt 19B made of a non-magnetic material such as brass into a female threaded hole drilled in the top plate 12. As shown in Figure 1, bolts 19A and 19B are long enough so that they do not protrude from the cover 10 when attached to the cover 10.

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 circumference 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).

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 silicon steel plate or NiFe alloy. To increase the amount of magnetic flux inside the yoke 14, it is desirable that the yoke 14 be made of a material with magnetic permeability equal to or greater than that of the material of the cover 10. If the yoke 14 is made of silicon steel plate, the magnetic permeability will be high, making it easier for magnetic flux to pass through the yoke 14.

The coils 15 are so-called magnet wires, with conducting wires wound around the yoke 14. The coils 15 of adjacent power generating units 3 are connected in series, and wiring drawn from the coils 15 of the multiple series-connected power generating units 3 is connected to the power supply board 41.

As shown in Figure 3, one end of the side plate 11 is fitted and fixed in a groove 21A provided on the outer periphery of the outer ring 21. The cylindrical protrusion 33 is fitted and fixed in 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 tone ring 30 can then be easily attached to the bearing body 20.

The magnetic field of the permanent magnet 13 causes magnetic flux Mf to pass through the yoke 14, the convex portion 31 or concave portion 32 of the tone ring 30, and the top plate 12 of the cover 10. As a result, the permanent magnet 13, yoke 14, the convex portion 31 or concave portion 32 of the tone ring 30, and the top plate 12 of the cover 10 form a magnetic circuit.

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 surface 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 surface 31IF of the protrusion 31. The magnetic body 311 is fitted into this recess. The magnetic body 311 and the outer peripheral end surface 31IF surrounding the magnetic body 311 are flush or nearly flush. 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.

Figure 6 is an explanatory diagram illustrating the relationship between the voltage of the electromotive force and time in a bearing with a wireless sensor. Here, the horizontal axis of Figure 6 represents time T, and the vertical axis represents the voltage Vi of the electromotive force. The outer ring 21 is fixed, and as the inner ring 22 rotates, the tone ring 30 rotates along with the inner ring 22, causing the tone ring 30 and the power generating unit 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 convex portion 31 shown in Figure 3 alternates with the air gap from the inner peripheral end face to the outer peripheral end face 32IF of the concave portion 32 shown in Figure 4.

In this way, the convex portions 31 and concave portions 32 on the outer periphery of the tone ring 30 periodically change the distance between the yoke 14 of the power generating unit 3 and the outer periphery of the tone ring 30. This changes the density of the magnetic flux Mf generated in the power generating unit 3. When the yoke 14 equipped with 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 tone ring 30 are farther apart, the magnetic flux Mf passing through the permanent magnet 13, yoke 14, and tone ring 30 is small. In response to this change in the density of the magnetic flux Mf, a voltage change occurs in the coil 15, which is made of magnet wire wound around the yoke 14.

In other words, when the yoke 14 and the outer peripheral end surface 31IF of the convex portion 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 concave portion 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.

Figure 7 is a plan view of the wireless sensor unit. As shown in Figure 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 the 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, temperature sensor 442, and angle sensor 443 described above, or it may be a sensor that measures other physical quantities.

Figure 8 is a perspective view of the cover. As shown in Figure 8, a through hole 12H is formed in the cover 10. As shown in Figure 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 a transmitting antenna 47 on the bearing body 20 side. Here, the cover 10 is magnetic, and therefore acts to shield electromagnetic waves from the transmitting antenna 47. For this reason, as shown in Figure 7, the transmitting antenna 47 is positioned so as 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 the portion of the cover 10 facing the transmitting antenna 47. Therefore, the electromagnetic waves WV from the transmitting antenna 47 can reach the communication unit 151 via the non-magnetic lid 17.

Also, as shown in FIG. 8, one surface 12A of the top plate 12 has 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.

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

The digital data transmitted from the wireless sensor unit 5 is received by the communication unit 151 of the host 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, making it possible to reduce its size.

In addition to the wireless sensor bearing 1 described above, the wireless sensor according to this embodiment also includes a spacer-type wireless sensor module that is installed near the bearing. Below, we will explain a wireless communication system that uses a wireless sensor such as the wireless sensor bearing 1 and wireless sensor module described above. Note that the following explanation includes components that are essentially the same as the configuration of the wireless sensor bearing 1 and host device 150 described in Figures 1 to 8.

In this embodiment, a specific example of application of a wireless communication system to a motor equipped with a bearing equipped with a wireless sensor is described. Figure 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 described above are given the same reference numerals, and duplicate explanations will be omitted. Furthermore, the rotating machine to which the wireless communication system according to this embodiment is applied is not limited to motors, and may also be, for example, a reducer equipped with a bearing equipped with a wireless sensor.

The motor 50 basically comprises a metal casing 51, a rotor 52, a stator 53, and an output shaft 54.

The rotor 52 and output shaft 54 are rotatably held relative to the metal casing 51 and 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 the object 100 to be controlled by the motor 50 is mechanically connected. In this embodiment, the object 100 to be controlled by the motor 50 (hereinafter also referred to as the "load") is a rotating machine such as a pump or a reducer.

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 composed of a conductor provided on the sensor substrate 42. The transmitting antenna 47 is, for example, one of a pattern antenna, a microstrip patch antenna, and a chip antenna.

As described above, the wireless sensor unit 5 of the present disclosure is covered by the cover 10 attached to the bearing body (first bearing) 20. The cover 10 is made of a magnetic material, and radio waves transmitted from the transmitting antenna 47 of the wireless sensor unit 5 are radiated in the direction of the rotation axis Ax of the bearing body (first bearing) 20 via the non-magnetic lid 17 that seals the through-hole 12H provided in the cover 10. When a bearing with a wireless sensor 1 is applied to a motor 50 having the structure shown in FIG. 9 , the transmitting antenna 47 of the wireless sensor unit 5 is positioned so that the maximum radiation direction of the radio waves faces inward in the direction of the rotation axis Ax. Therefore, the strength of the radio waves radiated from the transmitting antenna 47 of the wireless sensor unit 5 is greatest in the direction perpendicular to the sensor board 42. Therefore, when a bearing with a wireless sensor 1 is applied to a motor 50 having the structure shown in FIG. 9 , a system is required to extract the radio waves transmitted from the transmitting antenna 47 of the wireless sensor unit 5 to the outside of the metal housing 51.

The following describes a wireless communication system that can extract radio waves transmitted from the transmitting antenna 47 of the wireless sensor unit 5 outside the metal housing 51.

Figure 10 is a diagram showing an application example of a wireless communication system according to a first example of a comparative example. Components that are the same as those in Figure 9 are given the same reference numerals, and duplicate explanations will be omitted. In the first example of a comparative example shown in Figure 10, the wireless communication system includes a wireless sensor unit 5 and a non-powered repeater 60.

The elements that make up the passive repeater 60 are located in space A on the load side of the output shaft 54, where the wireless sensor bearing 1 is located. However, the internal space of a motor is generally narrow, and placement is restricted by the structure inside the metal casing.

In the motor 50 configured as shown in Figure 9, the parasitic repeater 60 cannot be installed on an extension of the direction of radio wave radiation (inward in the direction of the rotation axis Ax) of the transmitting antenna 47 of the wireless sensor unit 5. For this reason, in the example shown in Figure 10, the terminal portion 62 of the parasitic repeater 60 is inserted into a hole provided on the top surface of the metal casing 51. In other words, the direction of radio wave radiation 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.

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

The receiving antenna 65 of the parasitic repeater 60 is composed of a conductor mounted on an antenna substrate 64 made of, for example, resin, and is mounted inside the metal housing 51. The receiving antenna 65 can be composed of, for example, a pattern antenna or a microstrip patch antenna, and has maximum receiving sensitivity in the vertical direction of the antenna substrate 64. In the first comparative example shown in Figure 10, the receiving antenna 65 of the parasitic repeater 60 is positioned so that its direction of maximum sensitivity approximately coincides with the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5.

The terminal portion 62 and the antenna board 64 are connected, for example, by 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 board 64 is connected to the coaxial cable 63, for example, by an SMA connector or a U.FL connector. The coaxial cable 63 is, for example, a coaxial cable with a diameter of approximately 1.37 mm that is compatible with these SMA connectors and U.FL connectors.

As shown in Figure 10, the receiving antenna 65 of the parasitic repeater 60 is positioned opposite the transmitting antenna 47 of the wireless sensor unit 5. This means 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 65 of the parasitic repeater 60 are approximately aligned.

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

Figure 11 is a diagram showing an application example of a wireless communication system according to a second example of the comparative example. In the second example of the comparative example shown in Figure 11, the wireless communication system includes a wireless sensor unit 5, a first unpowered repeater 60, and a second unpowered repeater 80.

The first parasitic repeater 60 corresponds to the parasitic repeater 60 shown in Figure 10. In the example shown in Figure 11, a second parasitic repeater 80 is provided inside the metal housing 51. This second parasitic repeater 80 changes the radiation direction of the radio waves emitted from the transmitting antenna 47 of the wireless sensor unit 5 and transmits them to the first parasitic repeater 60.

The receiving antenna 85 of the second parasitic repeater 80 and the transmitting antenna 81 of the second parasitic repeater 80 are composed of conductors mounted on an antenna substrate 84 made of, for example, a resin. In the second comparative example shown in Figure 11, the receiving antenna 85 and the transmitting antenna 81 are composed of, 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 positioned so that the maximum sensitivity direction of the receiving antenna 85 approximately 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 approximately 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 each be mounted on separate substrates, and the substrates may be connected to each other by coaxial cables.

As shown in Figure 11, the receiving antenna 85 of the second parasitic repeater 80 is positioned opposite the transmitting antenna 47 of the wireless sensor unit 5. This causes the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 to approximately coincide with the maximum sensitivity direction of the receiving antenna 85 of the second parasitic repeater 80.

In addition, the transmitting antenna 81 of the second parasitic repeater 80 is positioned opposite the receiving antenna 65 of the first parasitic repeater 60. This means that 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.

Furthermore, by positioning the receiving antenna 85 of the second parasitic 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 that occurs between the transmitting antenna 47 of the wireless sensor unit 5 and the receiving antenna 85 of the second parasitic repeater 80.

Furthermore, by positioning the transmitting antenna 81 of the second parasitic repeater 80 and the receiving antenna 65 of the first parasitic repeater 60 so that 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 near-field electromagnetic coupling that occurs between the transmitting antenna 81 of the second parasitic repeater 80 and the receiving antenna 65 of the first parasitic repeater 60.

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 receiving antenna 65 of the first parasitic repeater 60 are connected via the terminal portion 62 and coaxial cable 63 in the space A on the load side of the output shaft 54 where the wireless sensor bearing 1 is provided inside the metal casing 51. In this configuration, the routing of the coaxial cable 63 and the placement 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, rotor 52, and stator 53 (e.g., ribs provided on the metal casing 51, windings on the stator 53, or magnets on the rotor 52). In particular, in the second comparative example shown in FIG. 11, the second parasitic repeater 80 has a substantially L-shaped structure, which limits the rotating machines to which the wireless communication system can be applied.

Below, we will explain a wireless communication system according to an embodiment that enables an expanded range of application.

Figure 12 is a diagram showing a specific example of a motor to which the wireless communication system according to the embodiment is applied. Note that components that are the same as those in Figure 11 are given the same reference numerals, and duplicate explanations will be omitted. The wireless communication system according to the embodiment differs from the second example of the comparative example shown in Figure 11 in the configuration of the second unpowered repeater 80.

In the configuration shown in Figure 12, the receiving antenna 85 of the second passive repeater 80 is composed of a conductor mounted on an antenna substrate 84a made of, for example, a resin, and is an antenna with maximum receiving sensitivity in the vertical direction of the antenna substrate 84a.

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

The receiving antenna 65 of the first parasitic repeater 60 is, like the second example of the comparative example shown in Figure 11, composed of a conductor mounted on a resin antenna substrate 64, and is an antenna with maximum receiving sensitivity in the vertical direction of the antenna substrate 64. The first parasitic repeater 60 is positioned so that 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 Figure 12).

The antenna board 84a on which the receiving antenna 85 of the second parasitic repeater 80 is mounted is arranged approximately parallel to the board on which the transmitting antenna 47 of the wireless sensor unit 5 is mounted, similar to the second example of the comparative example shown in Figure 11. As described above, the receiving antenna 85 of the second parasitic repeater 80 is an antenna whose receiving sensitivity is maximized in the vertical direction of the antenna board 84a. As a result, the maximum radiation direction of the transmitting antenna 47 of the wireless sensor unit 5 (the direction indicated by arrow b in Figure 12) and the maximum sensitivity direction of the receiving antenna 85 of the second parasitic repeater 80 are approximately aligned.

The antenna board 84a on which the receiving antenna 85 of the second parasitic repeater 80 is mounted is positioned approximately parallel to the board on which the transmitting antenna 47 of the wireless sensor unit 5 is mounted, 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). The receiving antenna 85 of the second parasitic repeater 80 is positioned so that 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 near-field electromagnetic coupling that occurs between the transmitting antenna 47 of the wireless sensor unit 5 and the receiving antenna 85 of the second parasitic repeater 80, thereby suppressing propagation loss of the radio waves radiated from the transmitting antenna 47 of the wireless sensor unit 5.

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 board 84b on which the transmitting antenna 81 of the second parasitic repeater 80 is mounted (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 board 84b, the multipath fading phenomenon caused by reflections within the metal casing 51 of radio waves radiated from the transmitting antenna 81 of the second parasitic repeater 80 is suppressed. This makes it possible to suppress propagation loss of radio waves radiated from the transmitting antenna 81 of the second parasitic repeater 80.

In this embodiment, the second parasitic repeater 80 has a transmitting antenna 81 and a receiving antenna 85 that are offset at different positions when viewed from a direction perpendicular to the horizontal plane of the antenna board 84a. This allows the size of the second parasitic repeater 80 in the direction of the rotation axis Ax to be reduced compared to the configuration of the second example of the comparative example shown in Figure 11, thereby expanding the range of application of the wireless communication system according to the present disclosure.

(Modification)
Fig. 13 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 the radio wave from the transmitting antenna 81 of the second parasitic repeater 80. However, as shown in Fig. 13, the first parasitic repeater 60 may be provided at a position deviated from the radiation direction of the radio wave from the transmitting antenna 81 of the second parasitic repeater 80, and the transmitting antenna 61 and the receiving antenna 65 of the first parasitic repeater 60 may be connected via a terminal part 62 and a coaxial cable 63.

The general structure of the second unpowered repeater 80 will be described below. Figure 14 is a schematic structural diagram of the second unpowered repeater according to the embodiment.

In the example shown in Figure 14, an antenna board 84a on which the transmitting antenna 81 of the second parasitic repeater 80 is mounted and an antenna board 84b on which the receiving antenna 85 of the second parasitic repeater 80 is mounted are fitted into a resin bracket 87 (resin member), and the transmitting antenna 81 and receiving antenna 85 are connected by a transmission path 88 provided in the bracket 87.

In the example shown in Figure 14, the transmission path 88 may be, for example, a coaxial cable or a waveguide. The transmission path 88 may also be configured such that a rod-shaped or plate-shaped conductor is embedded in the bracket 87, and the transmitting antenna 81 and the receiving antenna 85 are connected by this conductor. In this case, although the conductor is bent at a right angle in the illustrated example, it is preferable that it be formed in a gentle curve without any sharp bends.

Figure 15 is a schematic structural diagram of a second parasitic repeater according to a first modified example of the embodiment. Figure 14 shows an example in which an antenna board 84a on which the receiving antenna 85 of the second parasitic repeater 80 is mounted is fitted on one side of the bracket 87, and an antenna board 84b on which the transmitting antenna 81 of the second parasitic repeater 80 is mounted is fitted on the other side of the bracket 87. However, as shown in Figure 15, it is also possible to fit both the antenna board 84a on which the receiving antenna 85 of the second parasitic repeater 80a is mounted and the antenna board 84b on which the transmitting antenna 81 of the second parasitic repeater 80a is mounted on one side of the bracket 87.

Figure 16 is a schematic structural diagram of a second parasitic repeater according to a second modified example of the embodiment. While Figures 14 and 15 show an example in which the receiving antenna 85 and the transmitting antenna 81 are provided on different antenna boards 84a and 84b, as shown in Figure 16, the transmitting antenna 81 and receiving antenna 85 of the second parasitic repeater 80b may also be provided on the same antenna board 84.

In the example shown in Figure 16, the transmission path 88 is composed of a conductor provided on the antenna substrate 84, and the receiving antenna 85 and transmitting antenna 81 are connected via through holes and wiring provided on the antenna substrate 84.

Figure 17 is a schematic structural diagram of a second parasitic repeater according to a third modified example of the embodiment. While Figure 16 shows an example in which a receiving antenna 85 is provided on one side of the antenna board 84 and a transmitting antenna 81 is provided on the other side of the antenna board 84, as shown in Figure 17, it is also possible to provide both the receiving antenna 85 and the transmitting antenna 81 of the second parasitic repeater 80c on one side of the antenna board 84.

Note that while Figures 16 and 17 show an example in which the antenna board 84 is fitted into the bracket 87, the bracket 87 is not necessarily required in the examples shown in Figures 16 and 17.

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

In typical wireless communications, relaying radio waves using two wireless repeaters would result in significant loss and insufficient wireless signal strength, so such a design would not normally be considered. However, in this disclosure, we have taken into consideration the characteristics of industrial machinery such as rotating machinery, as described below, and discovered that a configuration that would not normally be considered in wireless communications is suitable.

The internal space of metal casings for so-called industrial machinery (motors, presses, machine tools, printing machines, etc.) is extremely narrow and complex. In contrast to wireless oscillators (IoT devices such as sensors) that acquire information from inside the machine, wireless repeaters that relay radio waves to the outside of the metal casing can often be placed relatively close to the wireless oscillators, such as sensors, minimizing wireless loss due to the distance between devices. However, as mentioned above, the narrow and complex structure inside metal casings makes it difficult for radio waves to diffract, resulting in significant loss due to the inability to reach the device directly. This disclosure focuses on this fact and has found that transmission loss can be significantly reduced by placing a repeater that changes the direction of radio waves near the wireless oscillator. In particular, it has been confirmed that the placement of such repeaters is highly effective in the rotating machinery described in the embodiments.

The figures used above are conceptual diagrams used to provide a qualitative explanation of the present disclosure, and are not intended to be limiting. Furthermore, while the above-described embodiment is one example of a preferred implementation of the present disclosure, it is not intended to be limiting, and various modifications may be made without departing from the spirit and scope of the present disclosure.

REFERENCE SIGNS LIST 1 Bearing with wireless sensor 5 Wireless sensor unit 10 Cover 20 Bearing body 21 Outer ring 22 Inner ring 40 Board 41 Power supply board 42 Sensor board 43 Power supply unit 44 Sensor 45 Control unit 47 Transmitting antenna (wireless sensor unit)
50 Motor 51 Metal housing 52 Rotor 53 Stator 54 Output shaft 60 Parasitic repeater (first parasitic repeater)
61 Transmitting antenna (parallel repeater, first parallax repeater)
62 Terminal portion 63 Coaxial cable 64 Antenna board 65 Receiving antenna (parasitic repeater, first parasitic repeater)
80 Second parasitic repeater 81 Transmitting antenna (second parasitic repeater)
84, 84a, 84b Antenna board 85 Receiving antenna (second non-powered repeater)
87 Bracket (resin member)
88 Transmission path 100 Rotation control target 150 Upper device 151 Communication unit 152 Computer 441 Acceleration sensor 442 Temperature sensor 443 Angle sensor

Claims (6)

a rotary machine including a shaft, a metal housing , and a bearing that rotatably holds the shaft relative to the metal housing; a wireless sensor unit that is provided inside the metal housing and in the vicinity of the bearing , the wireless sensor unit detecting the state of the bearing with a sensor and transmitting data 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 substrate, and having a maximum receiving sensitivity in a direction perpendicular to the substrate;
a transmitting antenna of the second parasitic repeater is a directional antenna that is formed by a conductor provided on a substrate and has unidirectionality in a direction parallel to the 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;
a transmitting antenna of the second parasitic repeater and a receiving antenna of the second parasitic repeater are arranged on a plane perpendicular to the rotation axis of the shaft, and are offset from each other at different positions when viewed from a direction parallel to the rotation axis of the shaft ;
the maximum radiation direction of the radio wave radiated from the transmitting antenna of the second parasitic repeater is directed in a direction perpendicular to the rotation axis of the shaft;
A wireless communication system , wherein the receiving antenna of the first parasitic repeater is arranged in a maximum radiation direction of radio waves radiated from the transmitting antenna of the second parasitic repeater. The wireless communication system of claim 1, wherein a substrate on which the receiving antenna of the second unpowered repeater is provided and a substrate on which the transmitting antenna of the second unpowered repeater is provided are embedded in a resin member, and the receiving antenna and transmitting antenna of the second unpowered repeater are connected by a transmission path provided in the resin member. The wireless communication system according to claim 2 , wherein the transmission path is a coaxial cable. The wireless communication system according to claim 2 , wherein the transmission path is a waveguide. 2. The wireless communication system of claim 1, wherein the receiving antenna of the second unpowered repeater and the transmitting antenna of the second unpowered repeater are provided on the same substrate, and the receiving antenna of the second unpowered repeater and the transmitting antenna of the second unpowered repeater are connected by a conductor provided on the substrate. a transmitting antenna of the wireless sensor unit is formed by a conductor provided on a substrate;
The wireless communication system according to any one of claims 1 to 5, wherein a substrate on which at least the receiving antenna of the second unpowered repeater is provided is arranged approximately parallel to a substrate on which the transmitting antenna of the wireless sensor unit is provided.