Bearing device

Abstract

To provide a bearing device for enabling the wireless transmission of data to the outside without forming a space between components around a bearing to easily propagate electric waves.SOLUTION: A bearing device (30) includes two bearings (5a, 5b) rotatably supporting a main shaft (4), a spacer (6) arranged between the two bearings (5a, 5b), and a communication module (140) arranged in the spacer (6), the bearing (5a) including a metal inner ring (5ia) and an outer ring (5ga), a plurality of rolling elements (Ta) arranged between the inner ring (5ia) and the outer ring (5ga), and the communication module (140) incorporating a plurality of sensors and a communication device for wirelessly transmitting the detection results of the sensors. An outer diameter size (D1) of the inner ring (5ia) of the bearing (5a) is set to be smaller than an inner diameter size (D2) of the outer ring (5ga) of the bearing (5a). A material for each rolling element (Ta) is silicon nitride through which electromagnetic waves can pass.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bearing device having a wireless communication function. [Background technology]

[0002] Machines that include rolling or oscillating mechanisms, such as those used in machine tool spindles, are sometimes fitted with detection devices such as sensors to control or monitor the condition of the machine. In particular, in machines that use rolling bearings, it is effective to detect characteristics near the bearings inside the machine, so it is desirable to place various sensors, such as rotation sensors and temperature sensors, near the bearings inside the machine.

[0003] Furthermore, conventionally, electrical wires are often used to transmit data detected by sensors, but placing electrical wires inside a machine can lead to interference with other mechanisms inside the machine and reduced functionality of those mechanisms (for example, reduced dimensional accuracy and reduced shape accuracy).It can also make the machine harder to assemble, which can be a factor in reducing productivity.

[0004] To address the above-mentioned problems, for example, Japanese Patent Laid-Open Publication No. 2003-28151 (Patent Document 1) discloses a bearing device in which a wireless sensor with an antenna is attached to the outer ring of the bearing, and data detected by this wireless sensor is transmitted wirelessly to the outside via radio waves.In this bearing device, in light of the fact that the bearing and its peripheral parts (housing, lid, etc.) are made of metal (magnetic material) which does not easily transmit radio waves, a space (hole or groove) is formed in the housing located around the part where the wireless sensor is attached, to make it easier for the radio waves transmitted from the wireless sensor to propagate to the outside. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-28151 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in the bearing device disclosed in JP 2003-28151 A, a space (hole or groove) is formed in the housing located around the part where the wireless sensor is attached to facilitate the propagation of radio waves.

[0007] However, the housing around the bearing is usually equipped with other mechanisms for cooling the bearing, and if there is interference with other mechanisms, it may not be possible to create sufficient space in the housing. Furthermore, if a space with a complex shape is created in the housing to avoid interference with other mechanisms, there are concerns that this will lead to a deterioration in the shape precision of the housing and an increase in costs.

[0008] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a bearing device that can transmit data wirelessly to the outside without having to create space to facilitate the propagation of radio waves in parts around the bearing. [Means for solving the problem]

[0009] (1) A bearing device according to the present disclosure is accommodated inside a cylindrical housing. The bearing device is disposed between a first bearing having an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, and a second bearing different from the first bearing, and is configured to communicate wirelessly using electromagnetic waves. A non-magnetic region for passing electromagnetic waves is formed somewhere between the inner diameter surface of the housing and the inner ring.

[0010] (2) In one embodiment, the vehicle further includes a self-power generating device disposed between the first bearing and the second bearing, which supplies power to the communication device.

[0011] (3) In one embodiment, the outer diameter of the inner ring is equal to or smaller than the inner diameter of the outer ring, and the nonmagnetic region is formed in the region between the inner ring and the outer ring.

[0012] (4) In one embodiment, the rolling elements are arranged at predetermined intervals on a pitch circumference between the inner ring and the outer ring, and the occupancy rate of the rolling elements on the pitch circumference is 40% or more and 90% or less.

[0013] (5) In one embodiment, the rolling elements are made of a non-magnetic material. (6) In one embodiment, the non-magnetic material is silicon nitride.

[0014] (7) In one embodiment, the rolling elements are made of a magnetic material. (8) In one embodiment, the magnetic material is high carbon chromium steel.

[0015] (9) In one aspect, the bearing device further includes a component disposed between the outer diameter surface of the outer ring and the inner diameter surface of the housing and made of a non-magnetic material. The non-magnetic region is formed in the region between the outer diameter surface of the outer ring and the inner diameter surface of the housing.

[0016] (10) In one aspect, the communication device performs wireless communication using electromagnetic waves with a frequency greater than the revolution period of the rolling elements when the first bearing rotates. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a bearing device that can transmit data wirelessly to the outside without forming a space in the parts around the bearing to facilitate the propagation of radio waves. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view (part 1) showing a schematic configuration of a spindle device including a bearing device. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a communication module. [Figure 3] FIG. 2 is a diagram showing an example of the arrangement of rolling elements in a bearing. [Figure 4]FIG. 2 is a cross-sectional view (part 2) showing a schematic configuration of a spindle device including a bearing device. [Figure 5] FIG. 10 is a cross-sectional view (part 3) showing a schematic configuration of a spindle device including a bearing device. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0020] FIG. 1 is a cross-sectional view showing a schematic configuration of a spindle device 1 equipped with a bearing device 30 according to this embodiment.

[0021] The spindle device 1 shown in Fig. 1 is used, for example, as a built-in motor type spindle device for a machine tool. In this case, a motor (not shown) is built into one end (the right side in Fig. 1) of the spindle 4 supported by the spindle device 1 for the machine tool main shaft, and a motor (not shown) is built into the other end A cutting tool such as an end mill (not shown) is connected to the left side in FIG. 1. In this embodiment, the diameter of the main spindle 4 is set to 70 mm, and the maximum rotation speed of the main spindle 4 is set to 20,000 rpm.

[0022] The spindle device 1 includes a bearing device 30. The bearing device 30 includes a bearing 5 including two bearings 5a and 5b, and a spacer 6 disposed between the bearings 5a and 5b. The main shaft 4 is provided inside a cylindrical housing 3 embedded in the inner diameter portion of the outer cylinder 2, and is rotatably supported by the bearings 5a and 5b.

[0023] The bearing 5a is a rolling bearing including a metal inner ring 5ia, a metal outer ring 5ga, a plurality of rolling elements Ta disposed between the inner ring 5ia and the outer ring 5ga, and a cage Rta. The spacing between the rolling elements Ta is maintained by the cage Rta.

[0024] The bearing 5b is a rolling bearing including a metal inner ring 5ib, a metal outer ring 5gb, a plurality of rolling elements Tb disposed between the inner ring 5ib and the outer ring 5gb, and a cage Rtb. The spacing between the plurality of rolling elements Tb is maintained by the cage Rtb.

[0025] An inner ring 5ia of a bearing 5a and an inner ring 5ib of a bearing 5b, which are spaced apart in the axial direction, are fitted onto the main shaft 4 in an interference fit state (press-fit state).

[0026] The spacers 6 include an inner ring spacer 6i and an outer ring spacer 6g. The inner ring spacer 6i is disposed between the inner rings 5ia and 5ib, and the outer ring spacer 6g is disposed between the outer rings 5ga and 5gb.

[0027] The bearings 5a and 5b may be angular contact ball bearings, deep groove ball bearings, tapered roller bearings, or the like. The bearing device 30 shown in Fig. 1 uses angular contact ball bearings, and the two bearings 5a and 5b are installed in a back-to-back (DB) configuration. Note that the bearing arrangement is not limited to a back-to-back configuration, and may also be, for example, a face-to-face configuration.

[0028] Here, a structure in which the main shaft 4 is supported by two bearings 5a and 5b is described as an example, but the main shaft 4 may be supported by two or more bearings.

[0029] A coolant flow path is formed in the housing 3. By flowing a coolant between the housing 3 and the outer cylinder 2, the bearings 5a and 5b can be cooled.

[0030] A communication module 140 with a built-in sensor is disposed between the bearing 5a and the bearing 5b. More specifically, the communication module 140 is attached to the outer ring spacer 6g in a state where it is exposed on the end face of the outer ring spacer 6g on the bearing 5a side (cutting tool side) in the axial direction. Note that a communication module similar to the communication module 140 may also be provided on the end face of the outer ring spacer 6g on the bearing 5b side (motor side) in the axial direction.

[0031] 2 is a block diagram showing an example of the configuration of a communication module 140 according to this embodiment. The communication module 140 has multiple sensors (a heat flow sensor 11 for measuring heat flux, a temperature sensor 56 for measuring temperature, a vibration sensor 57 for measuring vibration, and a load sensor 59 for measuring preload) built in for controlling the spindle 4 and monitoring the state of the bearing device 30, a communication device 141, and a power generation device 142.

[0032] The communication device 141 is connected to each sensor by an electric wire and collects data indicating the detection results of each sensor. Note that the communication device 141 may be connected to each sensor wirelessly and collect data indicating the detection results of each sensor wirelessly.

[0033] The communication device 141 transmits data collected from each sensor to an external device 200 provided outside the bearing device 30 via wireless communication using electromagnetic waves. In this embodiment, the communication device 141 complies with the Bluetooth (registered trademark) communication standard and wirelessly transmits data indicating the detection results of each sensor to the external device 200 using radio waves in the 2.4 GHz frequency band. It is assumed that the external device 200 is disposed axially outward of the bearing 5a (to the left of the bearing 5a in FIG. 1). Therefore, the bearing 5a is located between the communication device 141 and the external device 200.

[0034] Power generation device 142 is connected to communication device 141 and self-generates power to drive communication device 141. For example, a thermoelectric element (Peltier element) that generates power by the Seebeck effect can be used as power generation device 142. Note that when power is required to drive each sensor, power generation device 142 may supply power from power generation device 142 to the sensor.

[0035] In this embodiment, an example is described in which each sensor, communication device 141, and power generation device 142 are modularized into a single communication module 140 and placed in the outer ring spacer 6g, but each sensor, communication device 141, and power generation device 142 may also be placed individually without being modularized.

[0036] <About wireless data transmission> As described above, in the bearing device 30 according to this embodiment, a communication module 140 incorporating multiple sensors and a communication device 141 is disposed between the bearing 5a and the bearing 5b, and is configured to wirelessly transmit data indicating the detection results of each sensor to the outside.

[0037] However, the inner ring 5ia and outer ring 5ga of the bearing 5a are both made of metal, which makes it difficult for radio waves to propagate through them. Furthermore, the rolling elements Ta disposed between the inner ring 5ia and the outer ring 5ga revolve while in contact with the inner ring 5ia and the outer ring 5ga as the inner ring 5ia rotates. Therefore, if the rolling elements Ta were also made of metal, it would be difficult for radio waves to pass from the communication module 140 to the outside of the bearing 5a.

[0038] Furthermore, if a space were formed radially around the bearing 5a in the housing 3 to facilitate the propagation of radio waves, problems could arise such as interference with the cooling medium flow path of the housing 3, deterioration in the shape accuracy of the housing 3, and increased costs.

[0039] In consideration of this, in the bearing device 30 according to this embodiment, as shown in FIG. 1, the outer diameter D1 of the inner ring 5ia of the bearing 5a is set to be less than the inner diameter D2 of the outer ring 5ga of the bearing 5a, ensuring space in the region sandwiched between the inner ring 5ia and the outer ring 5ga. Furthermore, silicon nitride (e.g., Si3N4), which allows electromagnetic waves to pass through, is used as the material for the rolling elements Ta disposed between the inner ring 5ia and the outer ring 5ga. This allows the nonmagnetic region necessary for electromagnetic waves to pass through to be formed in the region sandwiched between the inner ring 5ia and the outer ring 5ga of the bearing 5a.

[0040] As a result, in the bearing device 30 according to this embodiment, data from the communication module 140 can be transmitted wirelessly to the outside of the bearing device 30 via the non-magnetic region between the inner ring 5ia and the outer ring 5ga of the bearing 5a. This allows data to be transmitted wirelessly to the outside without having to form a space to facilitate the propagation of radio waves in parts such as the housing 3 arranged around the bearing 5a. As a result, detection information from each sensor can be transmitted wirelessly to the outside of the bearing device 30 while preventing problems such as interference with other mechanisms around the bearing 5a, deterioration in the shape accuracy of the housing 3, and increased costs.

[0041] Furthermore, in bearing device 30 according to this embodiment, power generation device 142, which self-generates power to drive communication device 141, is disposed between bearings 5a and 5b, the same location as communication device 141. Therefore, communication device 141 can be driven without providing an electric wire outside bearing device 30 for supplying drive power to communication device 141.

[0042] If data is also to be wirelessly transmitted axially outward from bearing 5b (to the right of bearing 5b in FIG. 1), bearing 5b can be configured in the same manner as bearing 5a. That is, the outer diameter of inner ring 5ib of bearing 5b can be made smaller than the inner diameter of outer ring 5gb of bearing 5b to ensure space between inner ring 5ib and outer ring 5gb, and the material of multiple rolling elements Tb arranged between inner ring 5ib and outer ring 5gb can be silicon nitride.

[0043] Furthermore, the material of the rolling elements Ta and Tb is not limited to the silicon nitride as described above, as long as it is a non-magnetic material that allows electromagnetic waves to pass through. For example, the material of the rolling elements Ta and Tb may be a ceramic material such as alumina or zirconia, a resin material such as PEEK (polyether ether ketone) or PPS (polyphenylene sulfide), a material reinforced with carbon fiber or glass fiber, glass, or rubber.

[0044] Furthermore, if a non-magnetic area is secured in the space between the inner ring 5ia and the outer ring 5ga of the bearing 5a by using a non-magnetic material for the material of the multiple rolling elements Ta, the outer diameter dimension D1 of the inner ring 5ia of the bearing 5a may be the same as the inner diameter dimension D2 of the outer ring 5ga of the bearing 5a.

[0045] [Variation 1] In the above-described embodiment, the outer diameter dimension D1 of the inner ring 5ia of the bearing 5a is made smaller than the inner diameter dimension D2 of the outer ring 5ga, and the material of the rolling element Ta is made of a non-magnetic material, thereby forming a non-magnetic region between the inner ring 5ia and the outer ring 5ga.

[0046] In contrast, in this modified example 2, the outer diameter D1 of the inner ring 5ia of the bearing 5a is set to be smaller than the inner diameter D2 of the outer ring 5ga, as in the above-described embodiment, and the occupancy rate of the multiple rolling elements Ta on the pitch circumference sandwiched between the inner ring 5ia and the outer ring 5ga is set to be 40% or more and 90% or less, thereby forming a nonmagnetic region between the inner ring 5ia and the outer ring 5ga. The other configurations are the same as those of the above-described embodiment.

[0047] 3 is a diagram showing an example of the arrangement of rolling elements Ta in a bearing 5a according to Modification 1. The rolling elements Ta are held by a cage Rta so as to be arranged at predetermined intervals on a pitch circumference sandwiched between an inner ring 5ia and an outer ring 5ga.

[0048] 3 shows an example in which the occupancy rate of the rolling elements Ta on the pitch circumference is approximately 50%. By setting the occupancy rate of the rolling elements Ta on the pitch circumference at 50%, the load capacity of the bearing 5a is ensured while the space required for transmitting data between adjacent rolling elements Ta is secured, thereby forming a non-magnetic region.

[0049] If the occupancy rate of the rolling elements Ta on the pitch circumference is less than 40%, the load capacity of the bearing 5a may be insufficient. Furthermore, if the occupancy rate of the rolling elements Ta on the pitch circumference exceeds 90%, the space required for wireless data transmission between adjacent rolling elements Ta cannot be secured, and a non-magnetic region cannot be formed. Therefore, it is desirable that the occupancy rate of the rolling elements Ta on the pitch circumference be 40% or more and 90% or less. Of the range of 40% or more and 90% or less, a range of 50% or more is the optimal range for securing sufficient load capacity of the bearing 5a while also being able to form a non-magnetic region between adjacent rolling elements Ta.

[0050] When the occupancy rate of the multiple rolling elements Ta on the pitch circle circumference is set to 40% or more and 90% or less, the space required for wireless data transmission between adjacent rolling elements Ta is secured, so that the rolling elements Ta can be made of a metal (magnetic material) rather than a non-magnetic material. For example, the rolling elements Ta can be made of high-carbon chromium steel, which has excellent wear resistance. Note that using a non-magnetic material for the rolling elements Ta may also facilitate the transmission of radio waves. Furthermore, more than half of the multiple rolling elements Ta may be made of a magnetic material, and the remaining rolling elements Ta may be made of a non-magnetic material.

[0051] Furthermore, the communication module 140 conforms to the Bluetooth (registered trademark) communication standard and transmits radio waves in the 2.4 GHz frequency band, but the orbital frequency of the rolling element Ta relative to the outer ring 5ga when the inner ring 5ia rotates at 20,000 rpm, the maximum rotational speed of the main shaft 4, is about 100 to 150 Hz, and the frequency of the transmitted radio waves is sufficiently higher than the orbital frequency of the rolling element Ta. Therefore, even while the inner ring 5ia is rotating, the radio waves from the communication module 140 can pass sufficiently between the rolling elements Ta.

[0052] As described above, by making the outer diameter dimension D1 of the inner ring 5ia of the bearing 5a less than the inner diameter dimension D2 of the outer ring 5ga, and making the occupancy rate of the multiple rolling elements Ta on the pitch circumference sandwiched between the inner ring 5ia and the outer ring 5ga 40% or more and 90% or less, a non-magnetic region can be formed between the inner ring 5ia and the outer ring 5ga.

[0053] [Variation 2] 4 is a cross-sectional view showing the schematic configuration of a spindle device 1A equipped with a bearing device 30A according to Modification 2. The bearing device 30A is configured by replacing the communication module 140 of the bearing device 30 shown in FIG. 1 with a communication module 140A and adding an O-ring 160 made of a non-magnetic material. The other configurations of the spindle device 1A and bearing device 30A are the same as those of the spindle device 1 and bearing device 30 described above.

[0054] The communication module 140A is attached to the outer ring spacer 6g in a state where it is exposed on the outer diameter surface of the outer ring spacer 6g. The basic configuration of the communication module 140A is the same as that of the communication module 140 described above.

[0055] Two circumferential grooves 161 extending in the circumferential direction are provided in parallel on the outer diameter surface of the outer ring 5ga of bearing 5a and the outer diameter surface of the outer ring 5gb of bearing 5b. An annular O-ring 160 made of a non-magnetic material is attached to each of these circumferential grooves 161. The material of O-ring 160 may be any non-magnetic material, such as nitrile rubber or resin.

[0056] By inserting such a bearing device 30A into the housing 3, the non-magnetic areas necessary for wirelessly transmitting data can be formed not only in the area between the inner ring 5ia and outer ring 5ga of the bearing 5a, but also in the area between the outer diameter surfaces of the outer rings 5ga and 5gb of each bearing 5a and 5b and the inner diameter surface of the housing 3.

[0057] As a result, in the bearing device 30A according to this modified example 2, data from the communication module 140A can be wirelessly transmitted to the outside of the bearing device 30A via a non-magnetic region formed in the region between the inner ring 5ia and the outer ring 5ga of the bearing 5a, and a non-magnetic region formed in the region between the outer diameter surface of the outer ring 5ga of the bearing 5a and the inner diameter surface of the housing 3.

[0058] In the bearing device 30A according to the second modification, a non-magnetic region is formed by providing an O-ring 160 in the region between the outer diameter surface of the outer ring 5ga of the bearing 5a and the inner diameter surface of the housing 3, so the region between the inner ring 5ia and the outer ring 5ga of the bearing 5a is not necessarily a non-magnetic region. That is, in the bearing device 30A, the material of the rolling elements Ta of the bearing 5a may be a magnetic material such as a metal.

[0059] [Variation 3] Fig. 5 is a cross-sectional view showing a schematic configuration of a spindle device 1B equipped with a bearing device 30B according to Modification 3. The bearing device 30B is configured by adding a band 162 instead of the O-ring 160 of the bearing device 30A shown in Fig. 4 above. Other configurations of the spindle device 1B and bearing device 30B are the same as those of the spindle device 1 and bearing device 30 described above.

[0060] Two circumferential grooves 163 extending in the circumferential direction are provided in parallel at the portions of the inner diameter surface of the housing 3 where the outer ring 5ga of the bearing 5a and the outer ring 5gb of the bearing 5b are fitted. Annular bands 162 made of a non-magnetic material are attached to the circumferential grooves 163. The material of the bands 162 may be any non-magnetic material, such as nitrile rubber or resin.

[0061] In the bearing device 30B according to this modified example 3, as in the bearing device 30A according to the above-mentioned modified example 2, the non-magnetic areas necessary for wirelessly transmitting data can be formed not only in the area between the inner ring 5ia and outer ring 5ga of the bearing 5a, but also in the area between the outer diameter surfaces of the outer rings 5ga, 5gb of each bearing 5a, 5b and the inner diameter surface of the housing 3.

[0062] In bearing device 30B according to Modification 3, similarly to bearing device 30A according to Modification 2 described above, a nonmagnetic region is formed in the region between the outer diameter surface of outer ring 5ga of bearing 5a and the inner diameter surface of housing 3, so the region between inner ring 5ia and outer ring 5ga of bearing 5a does not necessarily have to be a nonmagnetic region. That is, in bearing device 30B, the material of rolling element Ta of bearing 5a may be a magnetic material such as metal.

[0063] [Variation 4] The components disposed between the outer diameter surfaces of the outer rings 5ga, 5gb of the bearings 5a, 5b and the inner diameter surface of the housing 3 are not limited to annular components such as the O-ring 160 in the above-described modified example 2 or the band 162 in modified example 3. For example, a rectangular component or a piece of paper-like component may be disposed between the outer diameter surface of the outer ring and the inner diameter surface of the housing to ensure the space required for transmitting data.

[0064] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0065] 1 spindle device, 2 outer cylinder, 3 housing, 4 main shaft, 5, 5a, 5b bearings, 5ga, 5gb outer ring, 5ia, 5ib inner ring, 6 spacer, 6g outer ring spacer, 6i inner ring spacer, 11 heat flow sensor, 30, 30A, 30B bearing device, 56 temperature sensor, 57 vibration sensor, 59 load sensor, 140, 140A communication module, 141 communication device, 142 power generation device, 160 O-ring, 161, 163 circumferential groove, 162 band, 200 external device, Rta, Rtb cage, Ta, Tb rolling element.

Claims

1. A bearing device accommodated inside a cylindrical housing, a first bearing having an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring; a communication module that is attached in an exposed state to a spacer that is disposed between the first bearing and a second bearing different from the first bearing, and that performs wireless communication using electromagnetic waves, a non-magnetic region is formed in any region between the inner diameter surface of the housing and the inner ring, allowing the electromagnetic waves to pass to the outside of the bearing device without passing through the housing and the spacer.

2. The outer diameter of the inner ring is formed to be equal to or smaller than the inner diameter of the outer ring, the nonmagnetic region is formed in a region sandwiched between the inner ring and the outer ring, the spacer includes an outer ring spacer disposed between the outer ring and the outer ring of the second bearing, The bearing device according to claim 1 , wherein the communication module is attached to an end surface of the outer ring spacer in an exposed state in the axial direction.

3. The first bearing and the second bearing are angular contact ball bearings, the plurality of rolling elements are arranged at predetermined intervals from one another on a pitch circumference sandwiched between the inner ring and the outer ring, 3. The bearing device according to claim 1, wherein an occupancy rate of the plurality of rolling elements on the pitch circumference is 40% or more and 90% or less.

4. 4. The bearing device according to claim 1, wherein the material of the plurality of rolling elements is a non-magnetic material.

5. 4. The bearing device according to claim 1, wherein the material of the plurality of rolling elements is a magnetic material.

6. The bearing device according to any one of claims 1 to 5, further comprising a self-power generating device disposed between the first bearing and the second bearing, for supplying power to the communication module.

7. The bearing device according to any one of claims 1 to 6, wherein the communication module performs wireless communication using electromagnetic waves having a frequency greater than the orbital period of the rolling element when the first bearing is rotating at an allowable rotational speed.

8. A bearing device described in any one of claims 1 to 7, wherein the first bearing and the second bearing are used to support the main spindle of a machine tool.

Images