Bearing device and spacer

Abstract

In order to prevent deterioration of wireless communication performance due to filling of a sealing material in a state in which a wireless communication circuit is accommodated in a housing chamber of a sensor-equipped spacer disposed between bearings, a spacer (5) is provided with a substrate (18) having an antenna (18a) of the wireless communication circuit formed on one surface thereof. A housing chamber (14) of the spacer (5) has a recess (20) that forms a space with the one surface of the substrate (18). The substrate (18) closes the recess (20) in a state in which the antenna (18a) faces the recess (20).

Description

Bearing device and spacer

[0001] The present invention relates to a bearing device in which a sensor and a wireless communication circuit are arranged in a spacer disposed between bearings, and to the spacer.

[0002] A known bearing device has been proposed in which a rotating shaft such as a spindle is supported by a plurality of bearings spaced apart in the axial direction, the spacing between these bearings is maintained by spacers, and a sensor and a wireless communication circuit are attached to the spacers to detect the condition of the bearings and transmit the detection results wirelessly to an external device (see Patent Document 1). This type of bearing device can monitor the operating conditions of the bearing device and the spindle equipped with it by using the detection results received by an external antenna.

[0003] The bearing device disclosed in Patent Document 1 has a circumferential groove-shaped storage chamber formed on one side of the spacer, sensors, wireless communication circuits, etc. surface-mounted on one side of a circuit board, the other side of the circuit board supported by the bottom surface of the groove in the storage chamber, and the circuit board protected by closing the storage chamber with a cover or filling the storage chamber with a sealant.

[0004] JP 2022-156079 A (see especially paragraphs 0048 to 0069, Figures 8 and 9)

[0005] When the storage chamber of the spacer in the bearing device of Patent Document 1 is closed with a cover, it is possible to suppress degradation of wireless communication performance by creating an air layer between the antenna of the wireless communication circuit and the cover and preventing dielectrics such as sealing material from coming into contact with the antenna, but this poses the problem of requiring a dedicated annular cover that fits into the circumferential groove-shaped storage chamber.This problem can be solved by filling the storage chamber with sealing material instead of using a dedicated cover, but in this case the sealing material covers the mounting surface of the circuit board and adheres to the antenna, attenuating the radio wave strength of a certain frequency and causing a problem of degradation of wireless communication performance.

[0006] Therefore, the problem to be solved by this invention is to prevent a decrease in wireless communication performance caused by filling a sealing material with a wireless communication circuit housed in a storage chamber of a sensor-equipped spacer disposed between bearings.

[0007] In order to solve the above problems, the present invention employs Configuration 1, which is a bearing device comprising a first bearing, a second bearing, a spacer arranged between the first bearing and the second bearing, a sensor attached to the spacer, and a wireless communication circuit that transmits the detection results of the sensor, wherein the spacer has a storage chamber that houses the wireless communication circuit and a sealant filled in the storage chamber, the bearing device is characterized in that it comprises a substrate having an antenna for the wireless communication circuit formed on one surface, the storage chamber has a recess that forms a space between it and the one surface of the substrate, and the substrate closes the recess with the antenna facing towards the recess.

[0008] As in the above configuration 1, a substrate having an antenna for a wireless communication circuit formed on one surface is used, a recess is provided in the storage chamber of the spacer to form a space between one surface of the substrate, the antenna faces the recess and the recess is covered with the substrate, and the space between the substrate and the periphery of the recess is sealed.By doing so, when filling the sealant, the plate portion of the substrate required to support the antenna can be used to prevent the sealant from entering the recess, and ultimately the sealant will not adhere to the antenna, making it possible to prevent a decrease in wireless communication performance due to the sealant.

[0009] In the above configuration 1, a configuration 2 can be adopted in which the storage chamber is formed by a spacer body sandwiched in the axial direction between the first bearing and the second bearing, and an attachment member facing the spacer body in the radial direction.

[0010] According to the above configuration 2, it is possible to provide a large accommodation space for the storage chamber between the mounting member and the spacer body while ensuring in the spacer body the rigidity required to maintain the gap between the first bearing and the second bearing.

[0011] In the above configuration 2, a configuration 3 can be adopted in which the recess is formed of a non-metallic material.

[0012] According to the above configuration 3, the recessed portion can be made radio wave transparent, thereby improving the radio wave reachability between the antenna and the outside.

[0013] In any one of the above configurations 1 to 3, a configuration 4 can be adopted, in which the device further includes a circuit board that processes the signal output from the sensor, the board and the circuit board are connected via wiring, and the circuit board is housed in the storage chamber and attached to a location different from the board.

[0014] According to the above-described configuration 4, the circuit board that performs signal processing can be housed in the storage chamber and protected together with the circuit board by the sealing material. Furthermore, the signal processing circuit section and the like are mounted on the circuit board to realize the required functions, and the specifications of the circuit board can be changed to change the functions realized by the circuit board without changing the board. Therefore, it is easy to develop products with different specifications in terms of the function of the circuit board.

[0015] In any one of the above configurations 1 to 4, a configuration 5 can be adopted in which the space between the substrate and the periphery of the recess is sealed with a sealant.

[0016] According to the fifth aspect, even when it is difficult to bring the substrate and the periphery of the recess into close contact in terms of dimensional accuracy, it is possible to reliably prevent the sealant from entering the recess.

[0017] Furthermore, in order to solve the above-mentioned problems, the present invention employs a configuration 6 comprising a sensor, a wireless communication circuit that transmits the detection result of the sensor, a storage chamber that houses the wireless communication circuit, a sealant filled in the storage chamber, and a substrate on one surface of which an antenna of the wireless communication circuit is formed, wherein the storage chamber has a recess that forms a space between the storage chamber and one surface of the substrate, and the substrate acts as a spacer that covers the recess with the antenna facing toward the recess.

[0018] By disposing the spacer according to the above configuration 6 between the first bearing and the second bearing, the bearing device according to the above configuration 1 can be configured, and degradation of wireless communication performance due to the sealing material can be prevented.

[0019] As described above, by adopting the above configuration 1, the present invention makes it possible to prevent a decrease in wireless communication performance due to a sealant in a bearing device in which a sensor is attached to a spacer between bearings of a bearing device, a wireless communication circuit that transmits the detection results of the sensor is housed in a storage chamber of the spacer, and the storage chamber is filled with a sealant.

[0020] 1 is a cross-sectional view showing a bearing device according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view showing a spindle equipped with the bearing device of FIG. 1; FIG. 3 is an exploded perspective view of the spacer of FIG. 1; FIG. 4 is a partial plan view showing a modification in which the base plate of FIG. 1 is screwed; FIG. 5 is a cross-sectional view showing a main part of a bearing device according to a second embodiment of the present invention;

[0021] A bearing device according to a first embodiment of the present invention (hereinafter simply referred to as "this bearing device") will be described with reference to FIGS. 1 to 4 of the accompanying drawings.

[0022] The bearing device shown in Figures 1 and 2 is used in a built-in motor type spindle of a machine tool, and includes a rotating shaft 1, a housing 2 surrounding the rotating shaft 1, a first bearing 3 and a second bearing 4 supporting the rotating shaft 1 so that it can rotate freely relative to the housing 2, and a spacer 5 and an inner spacer 6 arranged between the first bearing 3 and the second bearing 4.

[0023] Here, the direction along the central axis of rotation of the rotating shaft 1 is referred to as the "axial direction," the direction perpendicular to the central axis of rotation is referred to as the "radial direction," and the circumferential direction around the central axis of rotation is referred to as the "circumferential direction."

[0024] The rotary shaft 1 serves as the main shaft of the machine tool. A cutting tool (not shown), such as an end mill, is connected to one end of the rotary shaft 1 (the left side in FIG. 1 ).

[0025] The housing 2 has a motor housing 2a and a bearing housing 2b fitted inside one end of the motor housing 2a (left side in FIG. 1). A stator 7 and a rotor 8 of the built-in motor are arranged inside the other end of the motor housing 2a (right side in FIG. 1).

[0026] A cooling passage 2c is formed in the housing 2. By flowing a cooling medium through the cooling passage 2c, the bearing housing 2b can be cooled, and therefore the first bearing 3 and the second bearing 4 can be cooled.

[0027] As shown in FIG. 1, the first bearing 3 and the second bearing 4 are rolling bearings each having an inner raceway 3a, 4a fitted onto the rotating shaft 1, an outer raceway 3b, 4b fitted into the bearing housing 2b, a plurality of rolling elements 3c, 4c arranged between the inner raceway 3a, 4a and the outer raceway 3b, 4b, and cages 3d, 4d that hold the rolling elements 3c, 4c.

[0028] The first bearing 3 and the second bearing 4 are capable of applying a preload by an axial force, and are, for example, angular contact ball bearings, deep groove ball bearings, tapered roller bearings, etc. In the illustrated example, both bearings 3 and 4 are angular contact ball bearings, and are installed in a back-to-back configuration. These bearings 3 and 4 support the radial load and axial load acting on the rotating shaft 1 relative to the housing 2.

[0029] A third bearing 9 is provided between the rotating shaft 1 and the motor housing 2a at a position further toward the other end (to the right in FIG. 1 ) than the rotor 8, to rotatably support the rotating shaft 1 relative to the housing 2. The third bearing 9 supports a radial load acting on the rotating shaft 1 relative to the housing 2.

[0030] The spacer 5 is sandwiched in the axial direction between the outer raceway 3b of the first bearing 3 and the outer raceway 4b of the second bearing 4, and maintains the axial distance between these raceways 3b, 4b at a constant level or greater.

[0031] The inner spacer 6 is sandwiched in the axial direction between the inner raceway 3a of the first bearing 3 and the inner raceway 4a of the second bearing 4, and maintains the axial distance between these raceways 3a, 4a at a constant level or greater.

[0032] When assembling this bearing device, a preload is applied to the first bearing 3 and the second bearing 4 using the front cover 10 and lock nut 11. In the illustrated example, the front cover 10, first bearing 3, spacer 5, inner spacer 6, second bearing 4, etc. are inserted onto the rotating shaft 1, and the second bearing 4, etc. are tightened axially together with the lock nut 11 threaded onto the rotating shaft 1, thereby applying an initial preload to the first bearing 3 and the second bearing 4. The rotating shaft 1 is then inserted into the housing 2 until the outer race 4b of the second bearing 4 contacts the shoulder of the bearing housing 2b, and the front cover 10, which is axially fastened to the bearing housing 2b, presses the outer race 3b of the first bearing 3, thereby assembling the bearing device. Tightening the lock nut 11 applies an axial force to the inner race 4a of the second bearing 4, pushing the inner race 4a toward the inner spacer 6. This force is transmitted to the spacer 5 via the rolling elements 4c and outer raceway 4b of the second bearing 4, and from the spacer 5 to the outer raceway 3b, rolling elements 3c and inner raceway 3a of the first bearing 3, applying a preload to these bearings 3 and 4, and the spacer 5 is sandwiched axially between the outer raceway 3b of the first bearing 3 and the outer raceway 4b of the second bearing 4. The preload is determined by the amount of movement limited by the dimensional difference between the width of the spacer 5 and the width of the inner spacer 6.

[0033] As shown in FIGS. 1 and 3, the spacer 5 is divided into two parts in the radial direction: a spacer body 12 and a mounting member 13.

[0034] The spacer body 12 consists of a cylindrical portion that is sandwiched in the axial direction between the outer raceway 3b of the first bearing 3 and the outer raceway 4b of the second bearing 4. The mounting member 13 consists of a cylindrical portion that is inserted into the spacer body 12. The spacer body 12 and the mounting member 13 are each made of a single seamless member. A storage chamber 14 is formed by the spacer body 12 and the mounting member 13 that faces the spacer body 12 in the radial direction.

[0035] The storage chamber 14 shown in Fig. 1 is open at one axial end (the left end in Fig. 1) between the spacer body 12 and the mounting member 13 and closed at the other axial end (the right end in Fig. 1). The opening of the storage chamber 14 is located on one side of the spacer 5. The storage chamber 14 is filled with a sealant 15.

[0036] The sealing material 15 is intended to protect the sensor 16, circuit board 17, board 18, and power supply 19 housed in the storage chamber 14. The sealing material 15 is provided by injecting resin from an opening on one side of the storage chamber 14 and hardening it while the sensor 16 and other components are attached to the storage chamber 14.

[0037] The sealing material 15 may be any known resin sealing material or potting material that can be filled into the containment chamber 14 in a liquid state, has a fixed shape as the resin component hardens, and is fixed to the containment chamber 14. For example, an epoxy adhesive, a silicone sealing material, a liquid gasket, an epoxy resin, a urethane resin, or the like may be used as the sealing material 15.

[0038] The sensor 16 is an electric circuit that detects the state of the first bearing 3 and the second bearing 4 and the state of the surrounding area where these bearings 3, 4 are mounted, and outputs a signal indicating the detection result. Specifically, the sensor 16 detects at least one of a physical quantity and a chemical quantity related to the state of the first bearing 3 and the second bearing 4, and outputs a signal indicating the detection result. A temperature sensor, an acceleration sensor, a load sensor, etc. can be implemented as the sensor 16 as needed. There are no particular restrictions on the number or type of sensors attached to the spacer 5, and multiple sensors may be attached to the spacer, or in the case of a sensor that does not require protection by a sealing material, the sensor may be attached outside the containment chamber.

[0039] The circuit board 17 is an electric circuit that performs the signal processing and power supply control required to transmit information acquired by the sensor 16 to the outside of this bearing device. The circuit board 17 functions as a signal processing unit that processes the signal output from the sensor 16, as a communication processing unit of a wireless communication circuit that transmits the detection results of the sensor 16 to the outside, and as a power supply control unit that supplies power supplied from the power supply 19 to predetermined circuit units as a predetermined voltage and current. Necessary electronic components (not shown) for realizing these functions are mounted on the circuit board 17, and the sensor 16 and power supply 19 are each connected to the circuit board 17 via wiring (not shown).

[0040] An antenna 18a of a wireless communication circuit is formed on one surface of the substrate 18. The plate edge of one surface of the substrate 18 surrounds the antenna 18a. In order to attach the circuit boards 17 and 18 to different locations in the storage chamber 14, the substrates 17 and 18 are connected via wiring L. This connection allows the antenna 18a of the substrate 18 to transmit and receive radio waves, and a wireless communication circuit is constructed across the circuit boards 17 and 18, where the communication processing unit of the circuit board 17 sends and decodes the signals required for this transmission and reception. The wiring L can be soldered, for example, to a pad formed on the other surface of the substrate 18 opposite to the one surface.

[0041] The antenna 18a may be any conductor that complies with the wireless communication standard used in the wireless communication circuit, converts an electric signal (current) into radio waves and emits them into space, or receives radio waves and converts them into current. The type of the antenna 18a is not particularly limited, and examples thereof include a planar antenna (microstrip antenna, patch antenna), a planar inverted-F antenna (PIFA), a single-layer waveguide slot array antenna, and a wrap-around antenna.

[0042] The method for forming the antenna 18a on one side of the substrate 18 is not particularly limited, but examples include a method of surface-mounting an electronic component constituting the antenna on one side of a printed wiring board, or a method of printing the antenna on one side of a print wiring board. A printed wiring board in which an insulating resin is impregnated into the base material can be used as the substrate 18, and for example, any of a paper phenol substrate (bakelite substrate), paper epoxy substrate, glass composite substrate, glass epoxy substrate, and composite substrate can be used.

[0043] The power supply 19 is mounted to eliminate wired connection between the outer spacer 5 and the outside, and to enable wireless detection by the sensor 16 and wireless transmission of the detection results. Although an example in which a battery is attached to the spacer as the power supply 19 has been shown, as in Patent Document 1, the stator of a generator may be attached to the spacer and the rotor of the generator may be attached to the rotating shaft in order to use the generator as the power source, or both a generator and a battery may be used.

[0044] The output signal of the sensor 16 is input to the signal processing circuit section of the circuit board 17. Here, the output signal is subjected to required signal processing such as signal amplification and noise removal to generate a detection signal, which is input to the communication processing circuit section of the circuit board 17 as an electrical signal indicating the detection result of the sensor 16. Here, the detection signal is converted into an electrical signal conforming to a predetermined wireless communication protocol. This electrical signal is passed as an electric current to the antenna 18a. The antenna 18a radiates this electrical signal (current) into space as radio waves. The radio waves radiated from the antenna 18a are received by another antenna located externally.

[0045] 1 and 3 , the mounting member 13 of the spacer 5 has a recess 20 that forms a space between itself and one surface of the base plate 18 including the antenna 18a, a cylindrical wall 21 that extends all around the circumference, a flange 22 that protrudes radially from the cylindrical wall 21, and a nozzle portion 23 that sprays lubricating oil. The recess 20 is recessed radially from the tip of a frame-shaped wall that protrudes radially from the cylindrical wall 21 toward the spacer main body 12. The cylindrical wall 21 includes the bottom of the recess 20. The nozzle portion 23 protrudes radially toward the spacer main body 12 from a circumferential portion of the cylindrical wall 21 at a position circumferentially spaced from the recess 20.

[0046] The space formed between the spacer body 12 and the cylindrical wall 21 facing it in the radial direction serves as the accommodation space for the storage chamber 14. This accommodation space extends over the entire circumferential range excluding the nozzle portion 23. The flange 22 is a part for closing the accommodation space of the storage chamber 14 at the other axial end (the right end in FIG. 1 ), and is fitted onto the other axial end of the spacer body 12.

[0047] The nozzle portion 23 communicates with a through hole 24 formed in the spacer body 12. The through hole 24 communicates with a lubricating oil supply passage (not shown) provided in the bearing housing 2b. The nozzle portion 23 injects the lubricating oil that has flowed in from the through hole 24 toward the inside of the first bearing 3 and the second bearing 4. The lubricating oil may be injected in any of the forms of air oil, mist oil, or jet oil. By forming the nozzle portion 23 in the mounting member 13 and the through hole 24 in the spacer body 12, it is no longer necessary to install a separate nozzle member.

[0048] The spacer body 12 has a plurality of holes 25 formed in a predetermined arrangement to be used for attaching the circuit board 17 and the like to the spacer body 12. The circuit board 17 is placed on a flat concave bottom formed on the inner periphery of the spacer body 12, and is screwed to the spacer body 12 using the holes 25 formed therein. Note that there are no particular restrictions on the structure for attaching the sensor, circuit board, and power supply to the spacer, and adhesives or the like can also be used as appropriate.

[0049] The substrate 18 closes the recess 20 with the antenna 18a located on one surface of the substrate 18 facing the recess 20. The edge of one surface of the substrate 18 and the tip of the frame-shaped wall surrounding the recess 20 are sealed with an adhesive (not shown) as a sealant. This bonds the substrate 18 to the periphery of the recess 20 and also seals the gap between the substrate 18 and the periphery of the recess 20. The purpose of this sealing is to prevent the liquid sealant 15 from entering the recess 20 from between the substrate 18 and the periphery of the recess 20 when the sealant 15 is filled into the storage chamber 14. Therefore, the seal need only be liquid-tight, and does not need to be airtight.

[0050] To prevent the substrate 18 from being placed in a recessed state in the recess 20 and to facilitate positioning of the substrate 18 relative to the recess 20, it is preferable to support one surface of the substrate 18 around the periphery of the recess 20. To enable this support, it is preferable to set the opening area of ​​the recess 20 smaller than the area of ​​the printed wiring board of the substrate 18.

[0051] If the antenna 18a comes into contact with the recess 20, the dielectric constant around the antenna 18a may change, increasing the possibility that the wireless communication function may become unstable. In order to stabilize the wireless communication function, it is preferable that the antenna 18a not come into contact with the recess 20.

[0052] The depth from the periphery of the recess 20 supporting one surface of the substrate 18 to the bottom of the recess 20 may be set to be equal to or greater than the thickness of the substrate 18. For example, when electronic components are mounted on one surface of a printed wiring board, which is a component of the substrate 18, the depth of the recess 20 may be determined on the premise that it is set to be equal to or greater than the total thickness of the printed wiring board of the substrate 18 and the thickness of the electronic components to be mounted on this surface. If the depth of the recess 20 is insufficient, contact between the antenna 18a and the recess 20 may be avoided by interposing a thick sealant (not shown) between one surface of the printed wiring board of the substrate 18 and the periphery of the recess 20.

[0053] To facilitate sealing between the printed wiring board of the substrate 18 and the periphery of the recess 20, the periphery of the recess 20 is preferably a flat surface perpendicular to the thickness direction of the printed wiring board. The periphery of the recess 20 may be stepped, with a lower step overlapping the edge of the printed wiring board of the substrate 18 in the thickness direction and a higher step surrounding the edge. This prevents the printed wiring board of the substrate 18 from protruding from the periphery of the recess 20, improving the workability of interposing a sealant, and also facilitating the positioning of the substrate 18 relative to the recess 20 in the direction perpendicular to the thickness direction of the printed wiring board of the substrate 18.

[0054] It is preferable to use an adhesive as the sealing material, since it can simultaneously fix the substrate 18 and seal the recess 20. It is also preferable that the sealing material be a resin such as a sealing agent, from the viewpoints of insulation and radio wave transmission.

[0055] It is not necessary to glue one surface of the substrate 18 to the periphery of the recess 20. The substrate may be fixed to the spacer by screwing, or the above-mentioned adhesive and screwing may be used in combination to more firmly fix the substrate. An example of screwing the substrate is shown in FIG. 4. In the modified example shown in FIG. 4, a plurality of screw bosses 26 are formed in the recess 20, and through holes are formed in the printed wiring board of the substrate 18 in an arrangement corresponding to the screw bosses 26. Male screw members 27 are threaded through the through holes and into the screw bosses 26, thereby fixing the substrate 18 to the recess 20. In the modified example shown in FIG. 4, the stepped periphery of the recess 20 surrounds the edge of the printed wiring board of the substrate 18.

[0056] The spacer body 12 and the mounting member 13 are fixed together with an adhesive or the like. This fixing is performed with the necessary components to be housed in the storage chamber 14, such as the substrate 18 fixed to the mounting member 13 and the circuit board 17 fixed to the spacer body 12, fixed in their predetermined positions on the spacer body 12 and the mounting member 13. By combining the spacer body 12 and the mounting member 13 in this state and fixing the two together, the storage chamber 14 is formed and the storage of the circuit board 17 and the like in the storage chamber 14 is completed. Thereafter, a liquid sealant 15 is filled into the storage chamber 14 through an opening. As the filled sealant 15 hardens, the spacer body 12 and the mounting member 13 can be fixed more firmly than if they were fixed together using only adhesive.

[0057] When the storage chamber 14 is filled with the liquid sealant 15, the sealant 15 does not seep into the recess 20 from between the periphery of the substrate 18 and the recess 20, and the other surface of the substrate 18 is covered with the sealant 15, but the sealant 15 does not adhere to the antenna 18a on one surface of the substrate 18 that faces the storage space of the recess 20. Of course, since no holes such as through-holes are formed between the one surface and the other surface of the substrate 18, there is no concern that the liquid sealant 15 will seep into the recess 20 from other locations. Therefore, a gas layer filling the space formed by the recess 20 is formed between the antenna 18a and the recess 20, and the antenna 18a is in contact only with the gas layer. Note that when the substrate 18 is fixed in the atmosphere, the gas filling the space in the recess 20 is air, so the gas layer generally becomes an air layer.

[0058] Since the sealing material 15 does not come into contact with the antenna 18a, the strength of the frequency of the wireless communication using the antenna 18a does not decrease, and communication can be performed over a longer distance. Furthermore, since the recess 20 of the storage chamber 14 is covered by the printed wiring board of the substrate 18, which is necessary to support the antenna 18a as a circuit, there is no need to prepare a dedicated cover member for covering the recess 20.

[0059] When a printed wiring board such as a through-hole is used for mounting the substrate 18, the hole can be blocked by soldering the electronic component to be mounted or the wiring to be connected, thereby eliminating the concern that the liquid sealing material 15 will reach one side of the substrate 18 through the hole.

[0060] When a temperature sensor is used as the sensor to be attached to the spacer 5, it is also possible to mount the temperature sensor on one surface of the substrate 18. In this case, it is preferable to have the temperature sensor in contact with the recess 20. Since the temperature sensor in contact with the recess 20 has better thermal conductivity than the temperature sensor in contact with the air layer that fills the recess 20, the temperature sensor can accurately detect temperature changes that are conducted to the recess 20 due to the influence of the heat source.

[0061] Furthermore, when an acceleration sensor is used as the sensor to be attached to spacer 5, it is also possible to mount the acceleration sensor on one surface of substrate 18. In this case, if the acceleration sensor contacts recess 20, a force is applied directly to the surface of the acceleration sensor, which causes a decrease in detection accuracy, so it is preferable not to have the acceleration sensor contact recess 20.

[0062] Generally, since the rotating shaft 1 and the housing 2 are made of metal, if the antenna 18a is placed in the storage chamber 14 that faces the interior of the first bearing 3 and the interior of the second bearing 4, which are rolling bearings, in the axial direction, the radio wave arrival path between the outside of this bearing device and the antenna 18a will pass through the interior of the first bearing 3 and the interior of the second bearing 4. In order to make it easier for radio waves to pass through the interiors of these bearings 3 and 4, it is preferable to form the rolling elements 3c and 4c of the first bearing 3 and the second bearing 4 from ceramic, and form the cages 3d and 4d from resin.

[0063] Furthermore, it is preferable to form the recess 20 from a non-metallic material to improve radio wave reach from the recess 20 to the first bearing 3 and the second bearing 4. The mounting member 13, which is the component having the recess 20, does not need to be made of ceramic because it does not need to have the rigidity to withstand the preload applied to the first bearing 3 and the second bearing 4. Since resin is lighter and easier to process than ceramic, the mounting member 13 is made of resin.

[0064] On the other hand, the spacer body 12 needs to have enough rigidity to withstand the preload applied to the first bearing 3 and the second bearing 4. For this reason, the spacer body 12 is preferably made of metal or ceramic. As the metal, an iron-based material can be used.

[0065] This bearing device (see Figures 1 and 3) is as described above, and comprises a first bearing 3, a second bearing 4, a spacer 5 arranged between the first bearing 3 and the second bearing 4, a sensor 16 attached to the spacer 5, and a wireless communication circuit that transmits the detection results of the sensor 16 (in the illustrated example, a circuit that connects a communication processing circuit unit that is part of a circuit board 17 with an antenna 18a on a board 18), and the spacer 5 has a storage chamber 14 that houses the wireless communication circuit, and a sealant 15 that is filled in the storage chamber 14.

[0066] This bearing device, in particular, comprises a substrate 18 having an antenna 18a of the aforementioned wireless communication circuit formed on one surface thereof, the storage chamber 14 having a recess 20 which forms a space between it and one surface of the substrate 18, and the substrate 18 blocking the recess 20 with the antenna 18a facing the recess 20. As a result, when the liquid sealant 15 is filled into the storage chamber 14, the plate portion (printed wiring board in the illustrated example) of the substrate 18 required to support the antenna 18a can be used to prevent the sealant 15 from penetrating into the recess 20, and as a result, the sealant 15 does not adhere to the antenna 18a, and a decrease in wireless communication performance due to the sealant 15 can be prevented.

[0067] Furthermore, in this bearing device, the storage chamber 14 is formed by a spacer body 12 that is sandwiched axially between the first bearing 3 and the second bearing 4, and an attachment member 13 that faces the spacer body 12 in the radial direction. This ensures that the spacer body 12 has the rigidity to maintain the distance between the first bearing 3 and the second bearing 4, while allowing the storage space of the storage chamber 14 to be larger in the circumferential and radial directions between the attachment member 13 and the spacer body 12 compared to when the spacer is constructed using only the spacer body, thereby making it easier to store the substrate 18 and the like and to fill the sealing material 15.

[0068] Furthermore, in this bearing device, the recess 20 is formed from a non-metallic material, which allows the recess 20 to be radio wave transparent, thereby improving the radio wave reachability between the antenna 18a and the outside.

[0069] This bearing device also includes a circuit board 17 that processes the signal output from the sensor 16, and the board 18 and the circuit board 17 are connected via wiring L. The circuit board 17 is housed in the storage chamber 14 and attached to a different location from the board 18, so that the circuit board 17, which processes the signal, can be housed in the storage chamber 14 and protected together with the board 18 by the sealant 15. Furthermore, the signal processing circuit section, communication processing circuit section, etc. are mounted on the circuit board 17, and the required functions are realized by the circuit board 17, thereby avoiding mounting on the board 18. Because the board 18 and the circuit board 17 are attached to different locations and are connected by wiring L, even if the specifications of the circuit board 17 are changed, the specifications of the circuit board 17 can be changed to change the function realized by the circuit board 17 without changing the specifications or attachment position of the board 18. This makes it easy to develop products with different specifications in terms of the function of the circuit board.

[0070] Furthermore, since this bearing device seals the space between the substrate 18 and the periphery of the recess 20 with a sealing material (for example, an adhesive not shown), it can reliably prevent the sealing material 15 from penetrating into the recess 20 even in cases where it is difficult to tightly seal the substrate 18 and the periphery of the recess 20 in terms of dimensional accuracy, such as in the case of a printed wiring board which is a resin-impregnated board.

[0071] In this bearing device, an example has been shown in which the recess 20 is formed only in the mounting member 13, but the recess may be formed only in the spacer body, or may be formed across both the spacer body and the mounting member, or if multiple antennas are to be arranged, multiple recesses may be provided in the storage chamber. When multiple recesses are provided, one or more recesses may be provided in each of the spacer body and the mounting member.

[0072] A second embodiment, in which a recess is formed in a spacer body, is shown in Fig. 5. In the following, only differences from the first embodiment will be described, and the same reference numerals will be used for components corresponding to those in the first embodiment.

[0073] The mounting member 13 shown in Figure 5 differs from the first embodiment in that it does not include the recess 20. The spacer body 12 has the recess 20 formed on its inner periphery. The recess 20 does not have a frame-shaped wall protruding from the inner periphery of the spacer body 12, but has a shape that has depth in the radial direction from a flat portion formed on the inner periphery of the spacer body 12. The spacer body 12 is made of ceramic to ensure high rigidity while improving radio wave transmission between the recess 20 and the outside.

[0074] In the first and second embodiments described above, the recesses are formed on the radial end surfaces of the storage chamber, but they may also be formed on the closed end surface of the storage chamber. As an example, a third embodiment is shown in FIG. 6.

[0075] The mounting member 13 shown in Fig. 6 has a recess 20 formed on the side surface of a flange 22 (see Fig. 3). The substrate 18 is positioned in the radial direction by the mounting member 13 and the spacer body 12, and is abutted against the flange 22 in the axial direction.

[0076] In each of the above-described embodiments, the spacer is structured to be divided into a spacer body and an attachment member, but it is also possible to form the spacer from a single, seamless tubular member, and for example, a circumferential groove-shaped storage chamber can be formed on the side surface of the tubular member, and a recess can be formed on the bottom surface of the groove.

[0077] Furthermore, in each of the above-described embodiments, the communication processing circuit section of the wireless communication circuit is mounted on a circuit board, but it is also possible to mount all of the electronic components that make up the wireless communication circuit on the board. For example, all of these electronic components can be surface-mounted on one side of a printed wiring board to form a wireless module, and all of these electronic components can be housed in a recess.

[0078] Furthermore, in each of the above-described embodiments, a nozzle portion 23 is provided in the spacer 5, and for the convenience of supplying lubricating oil from the housing 2 to the nozzle portion 23 of the spacer 5, a storage chamber 14 including a recess 20 is provided in the spacer 5 sandwiched in the axial direction between the outer raceway 3 b of the first bearing 3 and the outer raceway 4 b of the second bearing 4. However, if no nozzle portion is provided in the spacer or if lubricating oil is supplied to the nozzle portion of the spacer from the rotating shaft, it is also possible to provide a storage chamber including a recess in the inner spacer.

[0079] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0080] REFERENCE SIGNS LIST 1 Rotating shaft 2 Housing 3 First bearing 4 Second bearing 5 Spacer 12 Spacer body 13 Mounting member 14 Storage chamber 15 Sealing material 16 Sensor 17 Circuit board 18 Board 18a Antenna 20 Recess L Wiring

Claims

1. A bearing device comprising a first bearing, a second bearing, a spacer arranged between the first bearing and the second bearing, a sensor attached to the spacer, and a wireless communication circuit that transmits the detection results of the sensor, wherein the spacer has a storage chamber that houses the wireless communication circuit and a sealant filled in the storage chamber, the bearing device is characterized in that it comprises a substrate having an antenna for the wireless communication circuit formed on one surface, the storage chamber has a recess that forms a space between it and one surface of the substrate, and the substrate covers the recess with the antenna facing towards it.

2. A bearing device according to claim 1, wherein the storage chamber is formed by a spacer body sandwiched axially between the first bearing and the second bearing, and a mounting member radially opposed to the spacer body.

3. A bearing device according to claim 2, wherein said recess is formed from a non-metallic material.

4. A bearing device as claimed in any one of claims 1 to 3, further comprising a circuit board that processes the signal output from the sensor, the circuit board and the circuit board being connected via wiring, the circuit board being housed in the storage chamber and attached to a location different from the circuit board.

5. A bearing device according to any one of claims 1 to 4, wherein the space between the substrate and the periphery of the recess is sealed with a sealing material.

6. A spacer comprising: a sensor; a wireless communication circuit that transmits the detection results of the sensor; a storage chamber that houses the wireless communication circuit; a sealant filled in the storage chamber; and a substrate on one surface of which an antenna for the wireless communication circuit is formed, wherein the storage chamber has a recess that forms a space between the storage chamber and one surface of the substrate, and the substrate covers the recess with the antenna facing towards the recess.

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