Bearing device

Abstract

This bearing device has a rolling bearing (10) provided with a sensor (22) and a wireless communication means (23) of a sensor unit (20). In order to improve the dust-proofness and watertightness of the communication means (23) while suppressing deterioration in communication performance and ease of assembly, the communication means (23) is equipped with a circuit board (25) having a wireless communication circuit (26) mounted thereon and an external antenna (28) connected to the circuit board (25) through a cable (27), the circuit board (25) and the communication circuit (26) are covered with a coating film (CT), the external antenna (28) is not covered with the coating film (CT), and a space is provided between the external antenna (28) and a resin cover (24) covering the communication means (23).

Description

Bearing device

[0001] The present invention relates to a bearing device in which a sensor and wireless communication means are provided in a rolling bearing.

[0002] Conventionally, bearing devices have been known in which a rolling bearing is equipped with a sensor that detects its condition and a wireless communication means for transmitting the sensor information to an external device. Some of these bearing devices have a circuit board on which the sensor and a wireless module serving as the wireless communication means are mounted, coated with a potting material to improve dustproofness and waterproofness.

[0003] However, in a bearing device in which the circuit board is coated as described above, if the wireless communication antenna (hereinafter also referred to as the "internal antenna") included in the wireless module comes into contact with the resin potting material, the dielectric properties of the resin may shorten the wavelength of the radio waves, potentially resulting in a decrease in communication performance.

[0004] In contrast, the bearing device (bearing with sensor) disclosed in Patent Document 1, as shown in Figure 6, has a sensor unit 60 provided on the side of a deep groove ball bearing 50 having balls 53 as rolling elements arranged between an outer ring 51 and an inner ring 52, and the sensor unit 60 comprises a circuit board 62 on which a wireless module 61 is mounted, a holder (lid member) 63 that houses the circuit board 62, resin 64 filled in the holder 63, and a cover 65 that provides an air layer between the internal antenna of the wireless module 61 and the resin 64, and by preventing the internal antenna from coming into contact with the resin 64, a deterioration in communication performance is suppressed.

[0005] Japanese Patent Application Laid-Open No. 2021-63591

[0006] However, in the bearing device of Patent Document 1, during assembly, it is necessary to assemble a small cover 65 that covers only the wireless module 61 including the internal antenna onto the circuit board 62 in the narrow space inside the holder (lid member) 63, which has the drawback of being time-consuming.

[0007] Therefore, an object of the present invention is to improve the dustproof and waterproof properties of the wireless communication means while suppressing deterioration in assembly ease and communication performance in a bearing device in which a sensor and wireless communication means are provided in a rolling bearing.

[0008] In order to solve the above problems, the present invention provides a bearing device comprising a rolling bearing having an outer ring, an inner ring arranged radially inside the outer ring, and a plurality of rolling elements arranged to roll freely between the outer ring and the inner ring, a sensor that detects the state of the rolling bearing, and wireless communication means that transmits information detected by the sensor to the outside, wherein the wireless communication means has a circuit board, a wireless communication circuit mounted on the circuit board, and an antenna that is arranged separately from the circuit board and connected to the circuit board by a cable, and the circuit board and the wireless communication circuit are covered with a coating film, and the antenna is not covered with the coating film (Configuration 1).

[0009] According to this configuration 1, the circuit board and the wireless communication circuit mounted thereon of the wireless communication means are covered with a coating film, thereby improving the dustproof and waterproof properties of the wireless communication means, and the antenna (hereinafter also referred to as the "external antenna") disposed separately from the circuit board is not covered with a coating film, so that the wavelength of radio waves is not shortened due to the dielectric properties of the coating film, thereby preventing a deterioration in communication performance. Furthermore, since the work of connecting the external antenna and the circuit board, which is pre-coated with a coating film, with a cable during assembly is not required, a deterioration in assembly efficiency is also suppressed.

[0010] In the above-mentioned configuration 1, when the cable is connected to a connector mounted on the circuit board, it is preferable that the connector is not covered with the coating film, since this can reliably avoid poor contact between the cable and the connector (configuration 2).

[0011] Furthermore, in the above configuration 1 or 2, if a holder for holding the sensor and the wireless communication means is fixed to the fixed raceway of the outer ring and the inner ring, the holder has an annular disk portion arranged to face the rolling elements, and the circuit board and the antenna are fixed to one surface of the disk portion, then by using a configuration (configuration 3) in which a resin cover that covers the wireless communication means is attached to the holder and a space is provided between the antenna and the cover, the dustproofness and waterproofness of the entire wireless communication means, including the antenna (external antenna), can be further improved without degrading communication performance.

[0012] As described above, this invention uses an external antenna as the antenna for the wireless communication means of the bearing device. The external antenna is arranged separately from the circuit board on which the wireless communication circuit is mounted and is connected to the circuit board by a cable, and the circuit board and the wireless communication circuit are covered with a coating film, while the external antenna is not. This makes it possible to improve the dustproofness and waterproofness of the wireless communication means while minimizing any deterioration in the assembly ease and communication performance of the bearing device.

[0013] 1 is a perspective view of the appearance of a bearing device according to an embodiment of the present invention; FIG. 2 is a longitudinal front view of the main part of the bearing device of FIG. 1; FIG. 3 is a right side view showing a part of the cover of the sensor unit of FIG. 1 cut away; FIG. 4 is an exploded perspective view of the sensor unit of FIG. 1;

[0014] An embodiment of the present invention will now be described with reference to Figures 1 to 5. As shown in Figures 1 and 2, the bearing device according to this embodiment has a sensor unit 20 and a generator 30 attached to one axial end of a rolling bearing 10.

[0015] In the following, the circumferential direction around the central axis of the rolling bearing 10 (bearing central axis) will be referred to as the circumferential direction, the direction along the bearing central axis will be referred to as the axial direction, and the direction perpendicular to the bearing central axis will be referred to as the radial direction. One axial side is the right side in Figure 2, and the other axial side is the left side in Figure 2.

[0016] The rolling bearing 10 is a deep groove ball bearing comprising an outer ring 11 having a raceway groove 11a on its inner circumference, an inner ring 12 having a raceway groove 12a on its outer circumference, a plurality of balls 13 as rolling elements arranged to roll freely between the raceway groove 11a of the outer ring 11 and the raceway groove 12a of the inner ring 12, a retainer 14 that holds the plurality of balls 13 so that they can roll freely at equal intervals, and a sealing member 15 that seals the other axial side of the bearing space between the outer ring 11 and the inner ring 12, with the outer ring 11 being a fixed ring fixed to a housing or the like (not shown), and the inner ring 12 being a rotating ring attached to a rotating shaft (not shown) so as to rotate integrally with it.

[0017] Annular cutouts 16 and 17 are formed on one axial end of the inner surface of the outer ring 11 and the outer surface of the inner ring 12, respectively, and a sensor unit 20 and a generator 30 are arranged between the cutouts 16 and 17.

[0018] As shown in Figures 2 to 4, the sensor unit 20 has a holder 21 that forms part of the generator 30, as described below, a sensor 22 and wireless communication means 23 held by the holder 21, and a lid-like cover 24 that covers the sensor 22 and wireless communication means 23.

[0019] The holder 21 is formed by pressing a single metal plate and has an annular disk portion 21a that expands in the radial and circumferential directions, and a fitting portion 21b that protrudes annularly from the outer periphery of the disk portion 21a to one side in the axial direction. The disk portion 21a faces the balls 13 of the rolling bearing 10, and the fitting portion 21b is press-fitted into the notch 16 of the outer ring 11, thereby fixing the holder 21 to the outer ring 11.

[0020] The sensor 22 detects the state of the rolling bearing 10 (temperature, vibration, rotational speed, etc. inside the bearing), and in this embodiment, an acceleration sensor 22a and a temperature sensor 22b are held by the holder 21. The type and number of sensors can be changed as appropriate.

[0021] The wireless communication means 23 includes a circuit board 25, a wireless communication circuit 26 mounted on the circuit board 25, and an antenna (external antenna) 28 arranged separately from the circuit board 25 and connected to the circuit board 25 by a cable (coaxial cable) 27.

[0022] The circuit board 25 is formed in the shape of an arcuate plate, and is screwed to one axial surface of the disk portion 21a of the holder 21. In addition to the wireless communication circuit 26, the sensor 22 and a power supply circuit (not shown) are also mounted on this circuit board 25.

[0023] The wireless communication circuit 26 is a wireless module in which an IC chip 26a having wireless functionality and an antenna (internal antenna) 26b are arranged on a base substrate, but the internal antenna 26b is not used; instead, an antenna terminal (not shown) is connected to a connector 25a mounted on the circuit board 25. The connector 25a is then connected to an external antenna 28 by a cable 27. Note that the wireless communication circuit can also use an IC chip that does not have an internal antenna. In this case, too, the antenna terminal of the IC chip is connected to the connector 25a of the circuit board 25.

[0024] The external antenna 28 is fixed to an arc-shaped mounting plate 29, which is screwed to one axial surface of the disk portion 21a of the holder 21 at a position circumferentially spaced from the circuit board 25.

[0025] As shown in FIG. 5, the circuit board 25 and the electronic components mounted thereon, such as the wireless communication circuit 26 and the sensors 22 (acceleration sensor 22a and temperature sensor 22b), are covered with a coating film CT made of a water- and oil-repellent resin.

[0026] The coating film CT is a thin film with a thickness ranging from several tens of μm to 200 μm, and is formed by immersing the part to be coated in a coating agent or by brushing the coating agent onto the part to be coated. The coating agent is selected from urethane-based, acrylic-based, silicone-based, olefin-based, fluorine-based, etc. depending on the conditions of use.

[0027] Here, the circuit board 25 is covered with the coating film CT as described above, but the connector 25a (and its surrounding area) mounted on the circuit board 25 is not covered with the coating film CT to avoid poor contact with the cable 27. In addition, the cable 27 and the external antenna 28 connected to the connector 25a are not covered with the coating film CT either, and the coating film CT does not shorten the wavelength of the radio waves emitted by the external antenna 28.

[0028] 2 to 4, the cover 24 is a resin member having annular protrusions that protrude in the axial direction from the outer and inner peripheries of an annular disk portion, and the annular protrusions on the outer periphery fit into the inner periphery of the fitting portion 21b of the holder 21 to cover the wireless communication means 23 (circuit board 25, wireless communication circuit 26, cable 27, and external antenna 28) and electronic components such as the sensor 22 mounted on the circuit board 25. A space is provided between the cover 24 and the external antenna 28 to prevent the wavelength of radio waves from being shortened by the cover 24 (see FIG. 5).

[0029] The generator 30 is a claw-pole type consisting of a magnetic ring 31 arranged so as to be rotatable integrally with the inner ring 12 of the rolling bearing 10, and an annular stator 32 fixed to the outer ring 11 in a state facing the magnetic ring 31 radially across an air gap.

[0030] The magnetic ring 31 is a rotor that generates a rotating magnetic field for the stator 32, and is made of magnetic rubber magnets 31a that are magnetized with alternating north and south poles in the circumferential direction and adhered to a core metal 31b around its entire circumference. The magnetic ring 31 is formed in a shape that has a flange at one end of a cylindrical portion, and the other end of the cylindrical portion is press-fitted or adhered to the peripheral portion of the cutout portion 17 of the inner ring 12, thereby fixing it to the inner ring 12.

[0031] The stator 32 is a stator that guides the magnetic flux emitted from the magnetic ring 31 through a yoke structure and induces an AC voltage in a coil 34 wound around a bobbin 33 within the yoke structure. The yoke structure is composed of a main stator 35 formed from the inner periphery of the holder 21 of the sensor unit 20, and a sub-stator 36 attached to the main stator 35. The main stator 35 and the sub-stator 36 are combined so that claw-shaped claw poles extending axially at regular intervals from their respective inner peripheries are alternately arranged in the circumferential direction. An annular convex portion on the inner periphery of the cover 24 fits onto the outer periphery of the sub-stator 36, sealing off the space in which the sensor 22 and wireless communication means 23 of the sensor unit 20 are installed.

[0032] When the inner ring 12 of the rolling bearing 10 rotates integrally with the rotating shaft, an AC voltage is generated at both ends of the coil 34 in response to the rotation, and the generated AC power is supplied to the sensor unit 20.

[0033] The bearing device of this embodiment has the above-mentioned configuration, and the wireless communication means 23 of the sensor unit 20 has a circuit board 25 on which a wireless communication circuit 26 is mounted, and an external antenna 28 connected to the circuit board 25 by a cable 27. The circuit board 25 is covered almost entirely with the coating film CT, while the external antenna 28 is not covered with the coating film CT. A space is provided between the resin cover 24 that covers the wireless communication means 23 and the external antenna 28 to prevent wavelength shortening of the radio waves emitted by the external antenna 28, and therefore it is possible to achieve both dustproofness and waterproofness of the wireless communication means 23 and ensure communication performance.

[0034] Furthermore, when assembling this bearing device, the external antenna 28 and the circuit board 25, which has been previously coated with the coating film CT, must be connected with a cable 27. However, this connection work does not require much effort, and is therefore easier to assemble than conventional devices in which a small cover that only covers the wireless module is attached to the circuit board.

[0035] The external antenna for this bearing device should be designed so that its radio wave characteristics are in the target frequency band when incorporated into the bearing device. For example, if the external antenna is fixed to the disk portion of the holder and covered with a cover as in the above-mentioned embodiment, it is designed to have the target frequency, taking into account the material, dimensions, dielectric constant, and other physical properties of the holder and cover. The target frequency is the 2.4 GHz band when the wireless communication standard is Bluetooth Low Energy (BLE).

[0036] 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.

[0037] For example, the holder of the sensor unit in the embodiment is fitted and fixed to the outer ring, which is the fixed ring, with the fitting portion facing outward in the axial direction, but the holder may also be fitted and fixed to the outer ring in the opposite manner, with the fitting portion facing inward in the axial direction.

[0038] In addition, although the outer ring of the rolling bearing is the fixed ring and the inner ring is the rotating ring in the embodiment, it is also possible to use the inner ring as the fixed ring and the outer ring as the rotating ring. In this case, the sensor unit holder is fitted and fixed into a notch formed in the shaft end of the inner ring.

[0039] Of course, the present invention can also be applied to a bearing device in which a sensor and wireless communication means are provided in a rolling bearing other than the deep groove ball bearing of the embodiment.

[0040] REFERENCE SIGNS LIST 10 deep groove ball bearing (rolling bearing) 11 outer ring (fixed ring) 12 inner ring (rotating ring) 13 ball (rolling element) 20 sensor unit 21 holder 21a disc portion 22 sensor 23 wireless communication means 24 cover 25 circuit board 25a connector 26 wireless communication circuit 27 cable 28 external antenna (antenna) 30 generator

Claims

1. A bearing device comprising: a rolling bearing (10) having an outer ring (11), an inner ring (12) disposed radially inside the outer ring, and a plurality of rolling elements (13) disposed for free roll between the outer ring (11) and the inner ring (12); a sensor (22) for detecting the state of the rolling bearing (10); and wireless communication means (23) for transmitting information detected by the sensor (22) to the outside, wherein the wireless communication means (23) has a circuit board (25), a wireless communication circuit (26) mounted on the circuit board (25), and an antenna (28) disposed separately from the circuit board (25) and connected to the circuit board (25) by a cable (27), wherein the circuit board (25) and the wireless communication circuit (26) are covered with a coating film (CT), and the antenna (28) is not covered with the coating film (CT).

2. A bearing device as described in claim 1, wherein the cable (27) is connected to a connector (25a) mounted on the circuit board (25), and the connector (25a) is not covered with the coating film (CT).

3. A bearing device as claimed in claim 1 or 2, wherein a holder (21) for holding the sensor (22) and the wireless communication means (23) is fixed to the raceway of one of the outer ring (11) and the inner ring (12) which is fixed to the stationary side, the holder (21) has an annular disk portion (21a) arranged to face the rolling body (13), the circuit board (25) and the antenna (28) are fixed to one surface of the disk portion (21a), a resin cover (24) which covers the wireless communication means (23) is attached to the holder (21), and a space is provided between the antenna (28) and the cover (24).

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