Bearing device

Abstract

To provide a bearing device where a sensor and wireless communication means are provided for a rolling bearing, for improving dust resistance and waterproofness of the wireless communication means while suppressing a reduction in the assemblability and communicating performance.SOLUTION: Wireless communication means 23 for a sensor unit 20 has a circuit board 25 mounted with a wireless communication circuit 26 and an external antenna 28 connected to the circuit board 25 via a cable 27. The circuit board 25 and the wireless communication circuit 26 are coated with a coating film CT, and the external antenna 28 is not coated with the coating film CT. A space is provided between a resin cover 24 covering the wireless communication means 23 and the external antenna 28 to prevent a wavelength reduction of electric waves caused by the external antenna 28, thus compatibly securing the dust resistance, waterproofness and communication performance of the wireless communication means 23.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, there is known a bearing device that is equipped with a sensor that detects the condition of a rolling bearing and a wireless communication means that transmits information from the sensor to the outside. Some of these bearing devices have a circuit board on which the sensor and a wireless module as the wireless communication means are mounted, coated with a potting material to improve dustproofness and water resistance.

[0003] However, in a bearing device in which the circuit board is coated as described above, if the antenna for wireless communication included in the wireless module (hereinafter also referred to as the "internal antenna") comes into contact with the resin used as the 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 FIG. 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, degradation of communication performance is suppressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-63591 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the bearing device of Patent Document 1 mentioned above, during assembly, it is necessary to attach a small cover 65 that covers only the wireless module 61 including the internal antenna to the circuit board 62 in the narrow space inside the holder (lid member) 63, which has the drawback that this work is 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. [Means for solving the problem]

[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 for detecting the state of the rolling bearing, and wireless communication means for transmitting 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 arranged separately from the circuit board and connected to the circuit board by a cable, the circuit board and the wireless communication circuit being covered with a coating film, and the antenna being 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, so that the dustproofness and waterproofness of the wireless communication means can be improved, and the antenna (hereinafter also referred to as "external antenna") arranged separately from the circuit board is not covered with a coating film, so that the wavelength shortening of radio waves due to the dielectric properties of the coating film does not occur, and deterioration of communication performance can be prevented. In addition, since the work of connecting the external antenna and the circuit board covered with a coating film in advance with a cable during assembly is not time-consuming, deterioration of assembly is also suppressed.

[0010] In the above 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 race 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, a configuration (configuration 3) in which a resin cover for covering the wireless communication means is attached to the holder and a space is provided between the antenna and the cover can be used to further improve the dustproofness and waterproofness of the entire wireless communication means including the antenna (external antenna) without degrading communication performance. Effect of the Invention

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

[0013] [Figure 1] FIG. 1 is an external perspective view of a bearing device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a longitudinal sectional front view of the main part of the bearing device shown in FIG. [Diagram 3] FIG. 2 is a right side view showing the sensor unit in FIG. 1 with a part of the cover cut away. [Figure 4] FIG. 2 is an exploded perspective view of the sensor unit of FIG. 1; [Diagram 5] FIG. 2 is a cross-sectional view of the main part of the sensor unit in FIG. 1 taken along the circumferential direction. [Figure 6] FIG. 1 is a longitudinal sectional front view of a main portion of a conventional bearing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, a 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) is referred to as the circumferential direction, the direction along the bearing central axis is referred to as the axial direction, and the direction perpendicular to the bearing central axis is referred to as the radial direction. One axial side is the right side in Fig. 2, and the other axial side is the left side in Fig. 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 at equal intervals so that they can roll freely, 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 the rotating shaft.

[0017] An annular cutout 16, 17 is formed at one axial end of the inner peripheral surface of the outer ring 11 and the outer peripheral surface of the inner ring 12, respectively, and a sensor unit 20 and a generator 30 are arranged between the cutouts 16, 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 expanding in the radial and circumferential directions, and a fitting portion 21b protruding annularly from the outer periphery of the disk portion 21a to one side in the axial direction. The fitting portion 21b is press-fitted into the notch portion 16 of the outer ring 11 with the disk portion 21a facing the balls 13 of the rolling bearing 10, thereby fixing the holder 21 to the outer ring 11.

[0020] The sensor 22 detects the state of the rolling bearing 10 (temperature inside the bearing, vibration, rotation speed, etc.), 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 an arc-shaped plate shape, 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] As the wireless communication circuit 26, a wireless module in which an IC chip 26a having a wireless function and an antenna (internal antenna) 26b are arranged on a base substrate is used, but the internal antenna 26b is not used and an antenna terminal (not shown) is connected to a connector 25a mounted on a circuit board 25. The connector 25a and an external antenna 28 are connected by a cable 27. Note that the wireless communication circuit can also use an IC chip that does not have an internal antenna. In that 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 spaced apart from the circuit board 25 in the circumferential direction.

[0025] As shown in FIG. 5, a circuit board 25 and electronic components mounted thereon, such as a wireless communication circuit 26 and a sensor 22 (an acceleration sensor 22a and a 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 parts to be coated in the coating agent or by brushing the coating agent onto the parts to be coated. The coating agent is selected according to the conditions of use from types such as urethane, acrylic, silicone, olefin, and fluorine.

[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 in order to avoid poor contact with the cable 27. Moreover, the cable 27 and the external antenna 28 connected to the connector 25a are also not covered with the coating film CT, and the coating film CT does not cause shortening of the wavelength of the radio waves emitted by the external antenna 28.

[0028] 2 to 4, cover 24 is a resin member having annular protrusions protruding in the axial direction from the outer and inner peripheries of an annular disk portion, and the annular protrusion on the outer periphery fits into the inner periphery of fitting portion 21b of holder 21 to cover wireless communication means 23 (circuit board 25, wireless communication circuit 26, cable 27, and external antenna 28) and electronic components such as sensor 22 mounted on circuit board 25. A space is provided between cover 24 and external antenna 28, so that cover 24 does not shorten the wavelength of radio waves (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 with an air gap therebetween.

[0030] The magnetic ring 31 is a rotor that generates a rotating magnetic field for the stator 32, and is made by adhering magnets 31a made of magnetic rubber, which are magnetized with alternating north and south poles in the circumferential direction, to a core metal 31b over the entire circumference. The magnetic ring 31 is formed in a shape having a flange at one end of a cylindrical portion, and the other end side 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 from the magnetic ring 31 with a yoke structure and induces an AC voltage in a coil 34 wound around a bobbin 33 in 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 in the axial direction at regular intervals from their respective inner peripheries are alternately arranged in the circumferential direction. An annular protrusion on the inner periphery of the cover 24 fits into the outer periphery of the sub-stator 36, sealing the space in which the sensor 22 and wireless communication means 23 of the sensor unit 20 are provided.

[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. Almost the entire circuit board 25 is covered 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 shortening of the wavelength of the radio waves emitted by the external antenna 28, so that 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 covered in advance with the coating film CT, must be connected with a cable 27. However, this connection does not require much work, making it easier to assemble than the conventional method 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 a target frequency band when it is installed in the bearing device. For example, when the external antenna is fixed to the disk part of the holder and covered with a cover as in the above-mentioned embodiment, it is designed to have a target frequency, taking into consideration the material, dimensions, dielectric constant, and other physical properties of the holder and cover. The target frequency is set to 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 and not restrictive in all respects. The scope of the present invention is defined by the claims, not 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 a fixed ring, with the fitting portion facing axially outward, but conversely, the holder may be fitted and fixed to the outer ring with the fitting portion facing axially inward.

[0038] In the embodiment, the outer ring of the rolling bearing is a fixed ring and the inner ring is a rotating ring, but the inner ring may be a fixed ring and the outer ring a rotating ring. In this case, the sensor unit holder is fitted and fixed in 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 as in the embodiment. [Explanation of symbols]

[0040] 10 Deep groove ball bearing (rolling bearing) 11 Outer ring (fixed ring) 12 Inner wheel (rotating wheel) 13 Ball (rolling element) 20 Sensor unit 21 Holder 21a Disc section 22 Sensors 23 Wireless communication means 24 Cover 25 Circuit Board 25a Connector 26 Wireless communication circuits 27 Cable 28 External Antenna (Antenna) 30 Generator

Claims

1. 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 between the outer ring (11) and the inner ring (12) so as to be freely rollable; A sensor (22) for detecting a state of the rolling bearing (10); and a wireless communication means (23) for transmitting information detected by the sensor (22) to an outside. The wireless communication means (23) includes a circuit board (25), a wireless communication circuit (26) mounted on the circuit board (25), and an antenna (28) arranged separately from the circuit board (25) and connected to the circuit board (25) by a cable (27); A bearing device characterized in that 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. 2. The bearing device according to 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 holder (21) for holding the sensor (22) and the wireless communication means (23) is fixed to a fixed raceway of the outer race (11) and the inner race (12); The holder (21) has an annular disk portion (21a) arranged to face the rolling element (13), and the circuit board (25) and the antenna (28) are fixed to one surface of the disk portion (21a); 3. The bearing device according to claim 1 or 2, wherein a resin cover (24) covering 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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