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] This invention relates to a bearing device provided with a sensor and wireless communication means on a rolling bearing.

Background Art

[0002] Conventionally, a bearing device provided with a sensor for detecting its state and wireless communication means for transmitting information of the sensor to the outside is known. Some of these bearing devices coat a circuit board on which a sensor and a wireless module as the wireless communication means are mounted with a potting material to improve dustproof and waterproof properties.

[0003] However, in the bearing device with the circuit board coated as described above, when an antenna for wireless communication (hereinafter also referred to as "internal antenna") included in the wireless module comes into contact with the resin which is the potting material, the wavelength of the radio wave becomes shorter due to the dielectric property of the resin, and there is a risk that the communication performance deteriorates.

[0004] On the other hand, as shown in FIG. 6, the bearing device (bearing with sensor) disclosed in Patent Document 1 is provided on the side of a deep groove ball bearing 50 in which balls 53 as rolling elements are arranged between an outer ring 51 and an inner ring 52. A sensor unit 60 includes a circuit board 62 on which a wireless module 61 is mounted, a holder (lid member) 63 for housing the circuit board 62, a resin 64 filled in the holder 63, and a cover 65 for providing an air layer between the internal antenna of the wireless module 61 and the resin 64, thereby suppressing a decrease in communication performance by preventing the internal antenna from coming into contact with the resin 64.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the bearing device of Patent Document 1 described above, when assembling, it is necessary to perform an operation of assembling a small cover 65 that covers only the wireless module 61 including the internal antenna on the circuit board 62 in a narrow space inside the holder (lid member) 63, and there is a problem that this operation is time-consuming.

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

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention provides a rolling bearing having an outer ring, an inner ring disposed radially inside the outer ring, and a plurality of rolling elements rotatably disposed between the outer ring and the inner ring, a sensor for detecting the state of the rolling bearing, and a wireless communication means for transmitting information detected by the sensor to the outside. In the bearing device, the wireless communication means includes a circuit board, a wireless communication circuit mounted on the circuit board, and an antenna disposed 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, among the wireless communication means, since the circuit board and the wireless communication circuit mounted thereon are covered with a coating film, the dustproof and waterproof properties of the wireless communication means can be improved. The antenna (hereinafter, also referred to as "external antenna") disposed separately from the circuit board is not covered with a coating film, so that the shortening of the wavelength of radio waves due to the dielectric property of the coating film does not occur, and a decrease in communication performance can be prevented. In addition, since the operation of connecting the external antenna and the circuit board preliminarily covered with a coating film by a cable during assembly is not time-consuming, a decrease in assemblability can also be suppressed.

[0010] In the above-described Configuration 1, when the cable is connected to a connector mounted on the circuit board, if the connector is not covered with the coating film, it is possible to surely avoid poor contact between the cable and the connector, which is preferable (Configuration 2).

[0011] Further, in the above-described Configuration 1 or 2, when a holder for holding the sensor and the wireless communication means is fixed to the fixed-side raceway ring of the outer ring and the inner ring, and the holder has an annular disc portion arranged to face the rolling elements, and the circuit board and the antenna are fixed to one surface of the disc portion, if 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 (Configuration 3), it is possible to further improve the dustproof and waterproof properties of the entire wireless communication means including the antenna (external antenna) without degrading the communication performance.

Advantages of the Invention

[0012] As described above, in this invention, as an antenna of the wireless communication means of the bearing device, an external antenna that 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 is used. The circuit board and the wireless communication circuit are covered with a coating film, and the external antenna is not covered with the coating film. Therefore, it is possible to improve the dustproof and waterproof properties of the wireless communication means while suppressing the deterioration of the assemblability and communication performance of the bearing device.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

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

[0015] Hereinafter, the circumferential direction centered on the central axis (bearing central axis) of the rolling bearing 10 is referred to as the circumferential direction, the direction along the bearing central axis is referred to as the axial direction, and the direction orthogonal to the bearing central axis is referred to as the radial direction. One side in the axial direction is the right side in FIG. 2, and the other side in the axial direction is the left side in FIG. 2.

[0016] The rolling bearing 10 includes an outer ring 11 having a raceway groove 11a on the inner circumference, an inner ring 12 having a raceway groove 12a on the outer circumference, a plurality of balls 13 as rolling elements rotatably arranged between the raceway groove 11a of the outer ring 11 and the raceway groove 12a of the inner ring 12, a cage 14 that rotatably holds the plurality of balls 13 at equal intervals, and a seal member 15 that closes the other axial side of the bearing space between the outer ring 11 and the inner ring 12. The outer ring 11 is a fixed ring fixed to a housing (not shown), and the inner ring 12 is a rotating ring attached to rotate integrally with a rotating shaft (not shown).

[0017] And, annular notch portions 16 and 17 are respectively 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, and the sensor unit 20 and the generator 30 are arranged between the notch portions 16 and 17.

[0018] As shown in FIGS. 2 to 4, the sensor unit 20 includes a holder 21 that forms part of a generator 30 as will be described later, a sensor 22 and wireless communication means 23 held by the holder 21, and a lid-shaped cover 24 that covers the sensor 22 and the 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 projects annularly from the outer peripheral portion of the disk portion 21a to one side in the axial direction. Then, with the disk portion 21a facing the balls 13 of the rolling bearing 10, the fitting portion 21b is press-fitted into the notch portion 16 of the outer ring 11, thereby being fixed to the outer ring 11.

[0020] The sensor 22 detects the state of the rolling bearing 10 (such as the temperature, vibration, rotational speed, etc. inside the bearing). 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 that is disposed 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 plate shape and is screwed to the surface of the disk portion 21a of the holder 21 on one side in the axial direction. In addition to the wireless communication circuit 26, the sensor 22 and a power supply circuit (not shown) are mounted on the 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. However, the internal antenna 26b is not used, and an antenna terminal (not shown) is connected to a connector 25a mounted on the circuit board 25. Then, the connector 25a and the external antenna 28 are connected by a cable 27. Note that as the wireless communication circuit, an IC chip without an internal antenna can also be used. In that case as well, 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 plate-shaped mounting plate 29, and the mounting plate 29 is screwed to one axial side surface of the disk portion 21a of the holder 21 at a position circumferentially separated from the circuit board 25.

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

[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 a coating agent or by brushing the coating agent onto the parts to be coated. The coating agent is selected according to the usage conditions from types such as urethane-based, acrylic-based, silicone-based, olefin-based, and fluorine-based.

[0027] Here, although the circuit board 25 is covered with the coating film CT as described above, the connector 25a (and its peripheral part) mounted on the circuit board 25 is not covered with the coating film CT in order to avoid poor contact with the cable 27. Also, the cable 27 and the external antenna 28 connected to the connector 25a are not covered with the coating film CT, and the coating film CT does not cause a shortening of the wavelength of the radio wave emitted by the external antenna 28.

[0028] Also, as shown in FIGS. 2 to 4, the cover 24 is a resin member having annular convex portions protruding axially from the outer peripheral portion and the inner peripheral portion of the annular disc portion. The annular convex portion on the outer peripheral side thereof is fitted into the inner periphery of the fitting portion 21b of the holder 21, covering 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 so that the cover 24 does not cause shortening of the radio wave wavelength (see FIG. 5).

[0029] The generator 30 is of a claw-pole type composed of a magnetic ring 31 arranged to rotate integrally with the inner ring 12 of the rolling bearing 10 and an annular stator 32 fixed to the outer ring 11 so as to face the magnetic ring 31 with an air gap in the radial direction.

[0030] The magnetic ring 31 is a rotor that generates a rotating magnetic field with respect to the stator 32, and is formed by adhering magnetic rubber magnets 31a magnetized alternately as N poles and S 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 the cylindrical portion, and the other end side of the cylindrical portion is press-fitted or adhered to the peripheral edge of the notch portion 17 of the inner ring 12 and fixed to the inner ring 12.

[0031] The stator 32 is a stator that guides the magnetic flux emitted from the magnetic ring 31 with a yoke structure and induces an alternating 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 peripheral portion 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 such that claw-shaped claw poles extending axially at regular intervals in the circumferential direction from their respective inner peripheral portions are arranged alternately in the circumferential direction. The annular convex portion on the inner peripheral side of the cover 24 is fitted onto the outer periphery of the sub-stator 36, sealing the space where the sensor 22 and the 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 as it rotates, and the generated AC power is supplied to the sensor unit 20.

[0033] The bearing device of this embodiment has the above configuration. The wireless communication means 23 of the sensor unit 20 includes 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 a coating film CT, and the external antenna 28 is not covered with the coating film CT. A space is provided between the resin cover 24 covering the wireless communication means 23 and the external antenna 28 to prevent the wavelength shortening of the radio waves emitted by the external antenna 28. Therefore, it is possible to achieve both dust and water resistance and communication performance of the wireless communication means 23.

[0034] Also, in this bearing device, when assembling, there is an operation of connecting the external antenna 28 and the circuit board 25 pre-covered with the coating film CT with the cable 27. However, this connection operation is not time-consuming. Therefore, compared with the case of assembling a small cover that only covers the conventional wireless module on the circuit board, it is advantageous in terms of assemblability.

[0035] Note that as the external antenna of this bearing device, it is advisable to use one designed so that the radio wave characteristics become the target frequency band in the state of being incorporated into the bearing device. For example, when the external antenna is fixed to the disc portion of the holder and covered with a cover as in the above-described embodiment, it is designed to reach the target frequency in consideration of physical property values such as the material, dimensions, and dielectric constant of the holder and the cover. The target frequency is in the 2.4 GHz band when the wireless communication standard is Bluetooth Low Energy (BLE).

[0036] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of this invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

[0037] For example, although 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, conversely, the holder may be fitted and fixed to the outer ring with the fitting portion facing axially inward.

[0038] Also, in the embodiment, the outer ring of the rolling bearing is the fixed ring and the inner ring is the rotating ring, but conversely, the inner ring can be the fixed ring and the outer ring can be the rotating ring. In that case, the holder of the sensor unit is fitted and fixed to the notch formed at the axial end of the inner ring.

[0039] And this invention can of course be applied to a bearing device provided with a sensor and wireless communication means in a rolling bearing other than the deep groove ball bearing as in the embodiment.

Explanation of Signs

[0040] 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 Disk 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 rolling bearing (10) having an outer ring (11), an inner ring (12) arranged radially inside the outer ring, and a plurality of rolling elements (13) arranged to be rotatable between the outer ring (11) and the inner ring (12); A sensor (22) for detecting the state of the rolling bearing (10); In a bearing device comprising wireless communication means (23) for transmitting information detected by the sensor (22) to the outside, 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) arranged separately from the circuit board (25) and connected to the circuit board (25) by a cable (27), The circuit board (25) and the wireless communication circuit (26) are covered with a coating film (CT), the antenna (28) and the cable (27) are not covered with the coating film (CT), and a space is provided between a resin cover (24) covering the wireless communication means (23) and the antenna (28). A bearing device characterized by that.

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 the fixed-side raceway ring of the outer ring (11) and the inner ring (12), The holder (21) has an annular disc 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 disc portion (21a). The bearing device according to claim 1 or 2, wherein the cover (24) is attached to the holder (21).

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