Bearing device

Abstract

To provide a bearing device capable of stably performing radio transmission of radio waves to the outside of a bearing, and capable of suppressing deterioration of detection sensitivity of a gas sensor.SOLUTION: A bearing device 1 includes a bearing 2 and a retaining member 12. The retaining member 12 is fixed to one of an outer ring 3 and an inner ring 4. A circuit board 13 is fixed to a surface 12f of a side plate 12A in an axial direction. At least one gas sensor SSR for detecting a state of the bearing 2 and a wireless communication circuit for transmitting output of the gas sensor SSR to the outside by radio are mounted on the circuit board 13. A through hole 42 is formed in the side plate 12A, and a porous film 41 is attached to cover the through hole 42.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a bearing device. [Background technology]

[0002] In order to monitor the condition of rolling bearings for equipment maintenance, bearing devices are used that have sensors located adjacent to the bearings. These bearing devices may be configured to wirelessly transmit data detected by the sensors for the purpose of conveniently transmitting the data.

[0003] An example of the above-described bearing device is disclosed in, for example, Japanese Patent Application Laid-Open No. 2017-72170 (Patent Document 1). In Japanese Patent Application Laid-Open No. 2017-72170, a multi-pole ring magnet is provided on one axial end face of a retainer that constitutes the bearing, an annular seal is installed to seal the gap between the inner ring and the outer ring, and a power generation coil and a wireless processing circuit are installed on the surface of the annular seal facing the multi-pole ring magnet.

[0004] Furthermore, an example in which the sensor of the bearing device is a gas sensor that detects deterioration of a lubricant used in the bearing is disclosed in, for example, WO 2017 / 188314 (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-72170 [Patent Document 2] International Publication No. 2017 / 188314 Summary of the Invention [Problem to be solved by the invention]

[0006] In the bearing device disclosed in JP 2017-72170 A, if the annular seal were made of metal, the radio waves emitted from the wireless processing circuit would be blocked and would not be transmitted outside the bearing. This is because the power-generating coil and wireless processing circuit are installed facing inward in the axial direction (toward the rolling elements). On the other hand, if the annular seal were made of a non-metallic material such as resin, or if the annular seal were provided with sufficient slits or other features to allow radio waves to pass through, radio waves could be transmitted outside the bearing. However, in this case, the rigidity of the annular seal would be reduced because it is made of resin. This could hinder the operation of the bearing device when it is vibrating.

[0007] Next, in WO 2017 / 188314, the gas sensor is installed outside the housing that houses the bearing, at a distance from the housing. However, in this case, the distance between the gas sensor and the bearing becomes wider, which may reduce the detection sensitivity of the gas sensor.

[0008] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a bearing device that is capable of stably wirelessly transmitting radio waves to the outside of the bearing and that suppresses a decrease in the detection sensitivity of the gas sensor. [Means for solving the problem]

[0009] A bearing device according to the present disclosure includes a bearing and a retaining member. The bearing includes an outer ring, an inner ring, and rolling elements. The retaining member is fixed to either the outer ring or the inner ring. The retaining member includes a side plate portion that has a width in the radial direction and extends along the circumferential direction. At least a portion of a power source capable of generating electric power and a circuit board are fixed to the retaining member. The circuit board is fixed axially to a surface of the side plate portion that does not face the rolling elements. At least one gas sensor that detects the state of the bearing and a wireless communication circuit that wirelessly transmits the output of the gas sensor to the outside are mounted on the circuit board. A through hole is formed in the side plate portion, connecting a first surface facing the rolling elements to a second surface located opposite the first surface. A porous film is attached to cover the through hole. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a bearing device that is capable of stably transmitting radio waves to the outside of the bearing and that suppresses a decrease in the detection sensitivity of the gas sensor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a bearing device according to a first embodiment. [Figure 2] FIG. 10 is a perspective view of the entire bearing device according to a second embodiment. [Figure 3] FIG. 2 is a cross-sectional view taken along a plane including the rotation axis of the bearing. [Figure 4] FIG. 4 is a diagram illustrating a cage. [Figure 5] FIG. 2 is a view of the bearing device as seen from the sensor unit side. [Figure 6] FIG. 10 is an exploded perspective view of a sensor unit according to a second embodiment. [Figure 7] FIG. 10 is a perspective view of the sensor unit according to the second embodiment after assembly. [Figure 8] 2 is an enlarged cross-sectional view of the sensor unit of FIG. 1 according to the first embodiment. FIG. [Figure 9] FIG. 11 is an enlarged cross-sectional view of the sensor unit of FIG. 10 according to the third embodiment. [Figure 10] 10 is a cross-sectional view of a first example of a bearing according to a third embodiment, taken along a plane including a rotation axis. FIG. [Figure 11] 10 is a cross-sectional view of a second example of the bearing according to the third embodiment, taken along a plane including the rotation axis. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present embodiment will be described below with reference to the drawings.

[0013] (Embodiment 1) <Bearing device configuration> FIG. 1 is a cross-sectional view of a bearing device according to a first embodiment. This corresponds to a cross-sectional view of a plane including a rotation axis O in FIG. 2 of a second embodiment, which will be described later. The positions of the components fixed to a retaining member 12 in FIG. 1 do not necessarily correspond to their actual positions. Referring to FIG. 1, a bearing device 1 according to this embodiment includes a bearing 2 and a sensor unit 6. Bearing 2 is a standard bearing whose axial dimensions are specified in a specific standard. A standard bearing is a bearing whose dimensions are specified in, for example, ISO or JIS standards. Bearing 2 is a radial bearing, and the axial dimension from one end to the other of bearing 2 is a dimension specified in ISO 15 or JIS B 1512-1. Hereinafter, bearing 2 will also be referred to as standard bearing 2.

[0014] Bearing 2 includes outer ring 3, inner ring 4, rolling elements 8, cage 9, and seal 10. In bearing 2, for example, outer ring 3 is the stationary ring and inner ring 4 is the rotating ring. Bearing 2 will be described as a deep groove ball bearing as an example, but the type of bearing 2 is not limited to a deep groove ball bearing. Bearing 2 may be selected from the model size of a standard bearing in which the distance W between end face 11 of bearing 2 and rolling elements 8 can accommodate sensor unit 6. End face 11 is also the end face of outer ring 3.

[0015] The rolling elements 8 are arranged at intervals in the circumferential direction of the bearing 2 (depth direction in Figure 1). The rolling elements 8 are held in place by a cage 9. The cage 9 is a resin component. The cage 9 is open on one end face side in the axial direction, i.e., the left-right direction in Figure 1 (the right side in Figure 1). The cage 9 has a shape in which the other end face side in the axial direction (the left side in Figure 1) is connected. For this reason, in Figure 1, the cage 9 is arranged only in the area roughly to the left of the center of the rolling elements 8, and is not arranged in the area to the right of the center of the rolling elements 8.

[0016] The sensor unit 6 includes a holding member 12, a circuit board 13, and a lid 14. The holding member 12 is made of a magnetic material, and is made of metal. The holding member 12 is disposed at a position on one end face side (the right side in FIG. 1 ) of the retainer 9 relative to the rolling elements 8. In other words, the holding member 12 is disposed on the axial side where the retainer 9 is open and not disposed. The holding member 12 is disposed at a position where the retainer 9 should originally be disposed.

[0017] The retaining member 12 includes a side plate portion 12A. The side plate portion 12A has a width in the radial direction of the bearing 2 (the vertical direction in FIG. 1) that is sufficient to extend from the outer ring 3 to the inner ring 4. The side plate portion 12A extends in the circumferential direction, i.e., in the shape of a ring. In other words, the side plate portion 12A extends continuously in the circumferential direction (for one circumference). The retaining member 12 is formed by the side plate portion 12A and an outer diameter surface and an inner diameter surface in the radial direction.

[0018] Side plate portion 12A is disposed at a position of retaining member 12 closest to rolling element 8 in the axial direction (inner side within bearing 2) so as to be adjacent to rolling element 8. Side plate portion 12A has a back surface 12b (first surface) facing the rolling element 8 and a front surface 12f (second surface) opposite back surface 12b (i.e., the side not facing rolling element 8). In other words, back surface 12b faces the inside of bearing 2, and front surface 12f faces the outside of bearing 2.

[0019] A through hole 42 connecting the back surface 12b and the front surface 12f is formed in the side plate portion 12A. The through hole 42 is connected to a space adjacent to the rolling element 8 inside the bearing 2. A porous film 41 is attached so as to cover the through hole 42. In particular, the porous film 41 covers the through hole 42 from the rolling element 8 side (back surface 12b side) in the axial direction, thereby blocking the through hole 42. In other words, the porous film 41 blocks the through hole 42 in the axial direction.

[0020] The porous membrane 41 is mainly composed of fluororesin. That is, although the porous membrane 41 may contain a small amount of materials other than fluororesin, the majority of the membrane is formed from fluororesin. The size (maximum diameter) of the pores contained in the porous membrane 41 is preferably, for example, 10 nm or more and 100 μm or less, and more preferably 100 nm or more and 10 μm or less. In FIG. 1, the porous membrane 41 is disposed in the through hole 42 so as to block the cross section intersecting the extension direction (axial direction) of the through hole 42.

[0021] At least a portion of a power source PWR capable of generating electric power and a circuit board 13 are fixed to the holding member 12. Note that the power source PWR in FIG. 1 may be, for example, a power source in any of the following embodiments 2 to 4, or may be a power source of another type. In other words, the power source PWR in FIG. 1 is a general term for power sources of any type. The circuit board 13 is fixed to a surface 12f of a side plate portion 12A of the holding member 12.

[0022] One or more gas sensors SSR that monitor and detect the state of the bearing 2 are mounted on the circuit board 13. Note that the type of gas sensor SSR shown in Figure 1 is not important. The gas sensor SSR is a general term for sensors that can detect gas. A wireless communication circuit 18 is also mounted on the circuit board 13.

[0023] The SSR gas sensor is, for example, a sensor that applies MEMS (Micro-Electro Mechanical Systems) technology. The SSR gas sensor has a structure in which a sensitive membrane that reacts to a specific gas is supported by multiple detection parts. When a gas is adsorbed onto the sensitive membrane of the SSR gas sensor, the sensitive membrane deforms. The SSR gas sensor detects gas by the strain (change in electrical resistance) induced in the detection part by this deformation.

[0024] Deterioration (oxidation) of the lubricant used in bearing 2 begins with a reaction that generates alkyl radicals due to the influence of light, heat, metals, etc. Primary and secondary products include aldehydes, ketones, carboxylic acids, and esters. The above-mentioned gas sensor SSR can be of any type, as long as it is capable of detecting the above products. For example, the gas sensor SSR may be capable of highly accurately detecting minute amounts of carbonyl compounds (formaldehyde, acetaldehyde, etc.), which are the main components of the odor that occurs when the lubricant in bearing 2 deteriorates.

[0025] Among these, it is preferable that the gas sensor SSR detects at least one of aldehydes and carboxylic acids having 8 or less carbon atoms.

[0026] The lid 14 is a non-metallic (resin) sealing member that covers the circuit board 13. The lid 14 protects the circuit board 13 fixed to the holding member 12, and also protects the inside of the sensor unit 6. A resin sealing material may be used to seal the circuit board 13 instead of the lid 14. The lid 14 also protects components other than the circuit board 13 that are fixed to the surface 12f of the side plate portion 12A (for example, the wireless communication circuit 18, the gas sensor SSR, etc.).

[0027] The outer diameter surface of the retaining member 12 on the radially outer side is fitted into and fixed to the first notch portion 3a formed in the outer ring 3. Note that, particularly when the inner ring 4 is a stationary ring, the retaining member 12 may be fixed to the inner ring 4. The retaining member 12 is press-fitted or bonded so that it does not protrude axially outward from the end face 11 of the outer ring 3. Note that the retaining member 12 may be fixed using a combination of press-fitting and bonding, or by other methods. When the retaining member 12 is fixed to the first notch portion 3a, a certain gap is secured between the rolling elements 8 and the retaining member 12. This gap prevents the rolling elements 8 and the retaining member 12 from coming into contact with each other even when axial displacement occurs.

[0028] By positioning retaining member 12 so that it does not protrude axially outward from end face 11 of outer ring 3, circuit board 13 and power supply PWR fixed to retaining member 12 are also positioned so that they do not protrude axially outward from end face 11 of outer ring 3. Note that retaining member 12, circuit board 13, and power supply PWR are preferably positioned so that they do not protrude axially outward from end face 20 of inner ring 4.

[0029] <Action and effect> A bearing device 1 according to the present disclosure comprises a bearing 2 and a retaining member 12. The bearing 2 includes an outer ring 3, an inner ring 4, and rolling elements 8. The retaining member 12 is fixed to either the outer ring 3 or the inner ring 4. The retaining member 12 includes a side plate portion 12A that has a width in the radial direction and extends along the circumferential direction. At least a portion of a power source PWR capable of generating electric power and a circuit board 13 are fixed to the retaining member 12. The circuit board 13 is fixed axially to a surface (surface 12f) of the side plate portion 12A that does not face the rolling elements 8. At least one gas sensor SSR that detects the state of the bearing 2 and a wireless communication circuit 18 that wirelessly transmits the output of the gas sensor SSR to an external device are mounted on the circuit board 13. The side plate portion 12A has a through hole 42 formed therein, which connects a first surface (back surface 12b) facing the rolling elements 8 to a second surface (front surface 12f) located on the opposite side to the first surface, and which communicates with a space adjacent to the rolling elements 8. A porous membrane 41 is attached so as to cover the through hole 42.

[0030] In the above-described bearing device 1, the through hole 42 may be formed so as to connect the internal space formed between the outer ring 3 and the inner ring 4 of the bearing 2 to the space in which the gas sensor SSR is disposed. The internal space formed between the outer ring 3 and the inner ring 4 is the space in which the rolling elements 8 are disposed.

[0031] Because circuit board 13 is fixed to surface 12f, circuit board 13 is fixed on retaining member 12 so that it faces outward from bearing 2. For this reason, even if retaining member 12 is made of metal, which is more rigid than resin, it is possible to prevent problems such as radio waves being blocked from wireless communication circuit 18 mounted on circuit board 13 and being unable to be transmitted outside bearing 2. In other words, radio waves can be transmitted stably wirelessly to outside bearing 2.

[0032] The wireless communication circuit 18 receives the output signal of the gas sensor SSR and transmits it wirelessly to the outside, allowing stable wireless transmission of radio waves to the outside of the bearing 2.

[0033] Furthermore, gas generated inside the bearing 2, for example, by oxidation of the lubricant, passes through the holes formed in the porous film 41. The porous film 41 allows the above-mentioned product gases to pass through but prevents wear particles, dust, and oil from entering the inside of the bearing 2. By attaching the porous film 41 to the through-hole 42 in the side plate portion 12A, only the product gases can pass from inside the bearing 2 to the surface 12f side of the side plate portion 12A. This allows the gas to be supplied to the gas sensor SSR mounted on the surface 12f side, for example, on the circuit board 13. Therefore, the gas sensor SSR can detect only the gas generated by the lubricant with high accuracy.

[0034] Furthermore, due to the function of the porous film 41, in this embodiment, it is possible to prevent foreign metal matter and lubricants from penetrating into the circuit board 13 (such as the wireless communication circuit 18 mounted thereon) on the surface 12f side, thereby preventing defects such as short-circuiting or deterioration of the circuit.

[0035] As described above, according to the present disclosure, it is possible to provide a bearing device 1 that can suppress a decrease in the detection sensitivity of the gas sensor SSR and can stably transmit radio waves to the outside of the bearing 2, regardless of the material of the holding member 12.

[0036] In the above-described bearing device 1, the circuit board 13 is covered with a non-metallic lid 14. This prevents gas generated inside the bearing 2 from unintentionally escaping from the gas sensor SSR after it has flowed to the gas sensor SSR mounted on the circuit board 13. This is because the lid 14 blocks the flow of gas. This allows gas generated inside the bearing 2 to be more reliably supplied to the gas sensor SSR. This further improves the gas detection sensitivity of the gas sensor SSR.

[0037] In the above-described bearing device 1, the porous film 41 is preferably disposed inside the through-hole 42 so as to close a cross section intersecting the extension direction of the through-hole 42. This allows gas passing through the porous film 41 to easily pass through the through-hole 42 and flow toward the gas sensor SSR.

[0038] The axial position of the porous membrane 41 within the through-hole 42 is arbitrary. That is, the porous membrane 41 may be disposed on the front surface 12f side (right side) or in the center of the through-hole 42 in FIG. 1 . However, it is more preferable that the porous membrane 41 be disposed on the back surface 12b side (left side) within the through-hole 42. In this way, the porous membrane 41 is disposed closer to the outer ring 3, inner ring 4, and rolling elements 8 inside the bearing 2. This makes it easier for gas generated by the lubricant and the like inside the bearing 2 to reach the porous membrane 41. This makes it easier for gas to enter the through-hole 42 and the gas sensor SSR side from the porous membrane 41.

[0039] In the bearing device 1, the porous film 41 preferably contains fluororesin as its main component. In this way, the porous film 41 allows only gas generated by oxidation of the lubricant in the bearing 2 to pass through, allowing it to penetrate to the gas sensor SSR mounted on the circuit board 13. In other words, the porous film 41 prevents wear powder, dust, and oil from penetrating the inside of the bearing 2 into the gas sensor SSR and the wireless communication circuit 18 on the circuit board 13.

[0040] In the above-described bearing device 1, the gas sensor SSR detects at least one of aldehydes and carboxylic acids having 8 or less carbon atoms. Specifically, it is preferable that the gas sensor SSR detects gases of compounds shown in Table 1 (chain aliphatic aldehydes) and Table 2 (carboxylic acids).

[0041] [Table 1]

[0042] [Table 2]

[0043] Tables 1 and 2 show low-molecular-weight, chain-like aliphatic aldehydes and carboxylic acids. The fewer the carbon atoms in these compounds, the lower their boiling points (i.e., they are more volatile). For this reason, gases containing compounds with fewer carbon atoms are suitable for detection by gas sensors. Bearings 2 are used under a variety of temperature conditions. A typical rolling bearing material is carbon steel SUJ2. The upper allowable temperature limit for bearings manufactured from SUJ2 through standard heat treatment is approximately 120°C. However, by subjecting the bearing to dimensional stabilization treatment, the bearing can be used at temperatures above 200°C. Considering these typical operating conditions for bearings, aldehydes and carboxylic acids with eight or fewer carbon atoms are particularly suitable as target products for detecting lubricant oxidation.

[0044] In the bearing device 1, the bearing 2 includes a cage 9 that holds the rolling elements 8 at intervals in the circumferential direction. The cage 9 has one axial end face that is open and the other axial end face that is connected. A holding member 12 is disposed on the cage 9 at a position closer to one end face than the rolling elements 8.

[0045] In the above-described bearing device 1, one axial end face of the cage 9 is open, and so a space is provided in the open portion (where the cage 9 would normally be located) for arranging the circuit board 13, power supply PWR, etc. In other words, a space for arranging the circuit board 13 and power supply PWR is effectively provided inside the bearing 2. Furthermore, a gas sensor SSR that detects conditions such as deterioration of the lubricant in the bearing 2 can be disposed in this space. This allows the gas sensor SSR to be disposed in a position very close to the bearing 2, enabling the gas sensor SSR to detect abnormalities in the bearing 2 with high accuracy.

[0046] Of the lubricants, those that are particularly susceptible to oxidation due to the effects of heat and metal (wear debris) are those that are located close to the outer ring 3, inner ring 4, and rolling elements 8 of the bearing 2. For this reason, if a gas sensor SSR is placed in the above spaces, it can detect deterioration of the lubricant due to oxidation with high accuracy.

[0047] In the above-described bearing device 1, the retaining member 12 may be made of metal.

[0048] Because the retaining member 12 is made of metal, it can hold the circuit board 13 and the gas sensor SSR mounted thereon with high rigidity. Therefore, even if the retaining member 12 is fixed directly to the vibrating bearing 2, malfunction of the gas sensor SSR can be suppressed. As a result, even in an operating environment where vibrations are applied, the bearing device 1 can stably monitor the deterioration of the lubricant with the gas sensor SSR and wirelessly transmit the data detected by the gas sensor SSR.

[0049] (Embodiment 2) <Bearing device configuration> In the following description of the bearing device in each embodiment, the same components as those in the bearing devices of the previous embodiments are given the same reference numerals, and unless there are particular differences in configuration and function, their description will not be repeated. In the second embodiment, an electromagnetic induction generator is used as the power source PWR provided in the bearing device 1 of the first embodiment. Figure 2 is a perspective view of the entire bearing device of the second embodiment. Referring to Figure 2, the bearing device 1 includes a bearing 2, a sensor unit 6, and a magnetic ring 7.

[0050] The sensor unit 6 includes a holding member 12, a circuit board 13, a lid 14, and a stator 5. The circuit board 13 is fixed to the radially outer region of the side plate portion 12A of the holding member 12, and the stator 5 is arranged so as to encompass the entire holding member 12.

[0051] The lid 14 is a non-metallic resin member that protects the inside of the sensor unit 6. In this embodiment, the lid 14 may be arranged to cover the area other than the stator 5, as shown in FIG. 3. Alternatively, the lid 14 may be arranged to cover the entire area including the stator 5. In either case, the lid 14 covers the circuit board 13. From the viewpoint of further increasing the gas detection sensitivity of the gas sensor SSR, it is preferable that the distance between the gas sensor SSR and the through-hole 42 is as short as possible. For this reason, in FIG. 3, which will be described next, the gas sensor SSR is shown at the position of the wireless communication circuit 18 in the other figures. However, in FIG. 3 and the subsequent cross-sectional views, as in FIG. 1, the positions of the components within the holding member 12 do not necessarily represent the actual positions.

[0052] The stator 5 includes two magnetic members 21 and 22, a bobbin 23, and a coil 24. A portion of the holding member 12 is used as the magnetic member 21 of the stator 5.

[0053] The magnetic ring 7 is a magnetic member magnetized with alternating north and south poles in the circumferential direction. The stator 5 is fixed to the outer ring 3, and the magnetic ring 7 is fixed to the inner ring 4. The stator 5 and the magnetic ring 7 form a generator G. The generator G is a claw-pole type generator, but may be a generator of other structure. The dot-dash line in Figure 2 indicates the rotation axis O of the bearing 2.

[0054] Fig. 3 is a cross-sectional view taken along a plane including the rotation axis of the bearing. Referring to Fig. 3, a stepped first cutout 3a is formed in the inner peripheral surface of one end of the outer ring 3, as in the first embodiment. Furthermore, a stepped second cutout 4a is formed in the outer peripheral surface of one end of the inner ring 4 so as to face the first cutout 3a. In the axial direction of the bearing 2 (also referred to as the axial direction), from the outer ring 3 to the inner ring 4, an annular recess 50 is formed by the first cutout 3a and the second cutout 4a, cut out toward the rolling element 8.

[0055] The magnetic ring 7 includes a core 7a and a multi-pole magnet 7b. The multi-pole magnet 7b is formed by vulcanizing and bonding a magnetic material, for example, a mixture of magnetic powder and rubber, to the core 7a, and then magnetizing the N and S poles alternately around the circumferential direction of the bearing 2. The core 7a of the magnetic ring 7 has a flange portion 7c to increase rigidity. The magnetic ring 7 is fixed to the outer diameter surface 4b of the inner ring 4 by press-fitting or the like. The flange portion 7c fits into a second notch portion 4a formed in the inner ring 4. The magnetic ring 7 is positioned so as not to protrude from the end face 20 of the inner ring 4.

[0056] The magnetic ring 7, stator 5, and circuit board 13 are arranged inside the annular recess 50 so that they do not overlap one another in the radial direction of the bearing 2. This allows each component to be arranged inside the annular recess 50, thereby reducing the axial thickness of the bearing 2. Furthermore, in the bearing device 1, for example, the magnetic ring 7 is fixed to the inner ring 4, and the stator 5 is fixed to the outer ring 3 at an opposing position. Because the inner ring 4 and outer ring 3 are subject to smaller axial movement of the bearing 2 than the cage 9, a stable amount of power can be generated by the generator G.

[0057] FIG. 4 is a diagram illustrating a retainer. Referring to FIG. 4, in retainer 9, recesses 93 are formed at a predetermined pitch along the circumferential direction of an axial end face 91 of an annular retainer body. A pair of claws 94, 94 are formed to protrude from opening ends that face each other in the circumferential direction of recess 93. The recess 93 and the pair of claws 94, 94 form a pocket 95 in which the rolling element 8 shown in FIG. 3 is housed. As described above, retainer 9 has a shape in which one end face 91 is open and the other end face 92 is connected. Retainer 9 is a resin member, and sensor unit 6 and magnetic ring 7 are arranged on the open side so as not to protrude from end face 11 and end face 20.

[0058] Figure 5 is a view of the bearing device as seen from the sensor unit side. In Figure 5, part of the lid 14 is omitted so that the inside of the sensor unit 6 can be seen. Referring to Figure 5, one or more gas sensors SSR that monitor the state of the bearing 2 are mounted on the circuit board 13. In addition, an acceleration sensor 15 and a temperature sensor 16 may also be mounted on the circuit board 13, for example.

[0059] The circuit board 13 also has a power supply circuit 17 and a wireless communication circuit 18 mounted thereon. The power supply circuit 17 rectifies AC power generated by the generator G and converts it into DC power. In other words, the power supply circuit 17 is completely separate from the power supply PWR (see FIG. 1), that is, the generator G (electromagnetic induction generator) in this embodiment. The gas sensor SSR, the acceleration sensor 15, the temperature sensor 16, and the wireless communication circuit 18 use the DC power converted by the power supply circuit 17. Terminals 25 are arranged on the circuit board 13.

[0060] The wireless communication circuit 18 includes an antenna unit 18a. The wireless communication circuit 18 wirelessly transmits the output of the gas sensor SSR, which monitors conditions such as deterioration of the lubricant in the bearing 2, to the outside using the antenna unit 18a. The circuit board 13 is fixed to the holding member 12 with a plurality of screws 19. The circuit board 13 may also be adhesively fixed to the holding member 12. The circuit board 13 on which the wireless communication circuit 18 is mounted is disposed opposite the resin cover 14. This results in a structure in which the wireless communication circuit 18 is not sealed with a conductive material such as metal. This enables wireless communication using the antenna unit 18a in the wireless communication circuit 18.

[0061] The wireless communication circuit 18 may include a calculation unit 18b. The calculation unit 18b is, for example, a commonly known CPU (Central Processing Unit) that analyzes and processes the components of the gas detected by the gas sensor SSR. In FIG. 5, for ease of viewing, the calculation unit 18b is arranged adjacent to the main body of the wireless communication circuit 18. However, this is not a limitation. The calculation unit 18b may be mounted inside the main body of the wireless communication circuit 18 so that it is not visible from the outside. The calculation unit 18b wirelessly transmits data on the gas analysis results received from the gas sensor SSR to the outside.

[0062] FIG. 6 is an exploded perspective view of the sensor unit according to the second embodiment. FIG. 7 is a perspective view of the sensor unit according to the second embodiment after assembly. With reference to FIGS. 6 and 7, the circuit board 13 is fixed to a surface 12f of the side plate portion 12A of the holding member 12 on the side that does not face the rolling elements 8. The circuit board 13 is disposed in a relatively outer region of the surface 12f in the radial direction. The stator 5 includes a stator 5A and a stator 5B. The stator 5A corresponds to the holding member 12 and the magnetic member 21. The stator 5B corresponds to the magnetic member 22. In other words, the stator 5A, the holding member 12, and the magnetic member 21 are the same, and the stator 5B and the magnetic member 22 are the same.

[0063] The magnetic material members 21 and 22 have a U-shaped cross section. However, while the magnetic material member 21 occupies the entire holding member 12, the magnetic material member 22 is arranged in a radially inner region of the holding member 12. The radially inner region of the U-shaped cross section of the magnetic material member 21 faces the U-shaped cross section of the magnetic material member 22. A coil 24 including a bobbin 23 is attached between the opposing magnetic material members 21 and 22 so as to be surrounded by the magnetic material members 21 and 22. A plurality of claw portions 21a are formed on the inner peripheral portion of the magnetic material member 21. A plurality of claw portions 22a are formed on the inner peripheral portion of the magnetic material member 22. The coil 24, which is wound with magnet wire multiple times, is arranged in a groove provided in the circumferential direction of the bobbin 23. The bobbin 23 may be omitted.

[0064] The sensor unit corresponding to the perspective view of FIG. 7 in the first embodiment does not have the stator 5, the plurality of claws 21a and the claws 22a, but otherwise is basically the same as that in FIG.

[0065] The method of assembling the stator 5 will be described below. First, the bobbin 23 wound with the coil 24 is inserted into the magnetic member 22, and the magnetic member 21 and the magnetic member 22 are assembled so that the claws 21a of the magnetic member 21 and the claws 22a of the magnetic member 22 are alternately arranged with gaps in the circumferential direction. Next, the outer peripheral surface 22b of the magnetic member 22 is fixed so that its end contacts the surface 12f of the side plate portion 12A of the magnetic member 21. At this time, the openings of the magnetic member 21 and the magnetic member 22 face each other, and the bobbin 23 and the coil 24 are housed in the openings.

[0066] The multiple claws 21a of the magnetic member 21 and the multiple claws 22a of the magnetic member 22 are arranged facing each other with a gap maintained between them and the multi-pole magnet 7b of the magnetic ring 7 shown in Fig. 3. The multiple claws 21a of the magnetic member 21 and the multiple claws 22a of the magnetic member 22 in the stator 5, together with the magnetic ring 7, form a claw-pole generator G. The total number of the multiple claws 21a, 22a is equal to the number of poles (the total number of north and south poles) of the multi-pole magnet 7b.

[0067] The magnetic flux emitted from the north pole of the multi-pole magnet 7b enters the magnetic member 21 (or magnetic member 22) through, for example, the multiple claws 21a (or multiple claws 22a) that are magnetic poles, circulates around the coil 24, passes through the multiple adjacent claws 22a (or multiple claws 21a), and returns to the south pole of the multi-pole magnet 7b. When the positions of the north pole and south pole of the multi-pole magnet 7b are swapped due to the rotation of the inner ring 4, the direction of the magnetic flux is reversed. The alternating magnetic field generated in this way generates alternating current at both ends of the coil 24.

[0068] The start and end (not shown) of the coil 24 drawn out from the stator 5 are connected to terminals 25 provided on the circuit board 13. The AC power output from the generator G as the inner ring 4 rotates is converted into DC power by the power supply circuit 17.

[0069] The sensor unit 6 of the bearing device 1 may be divided into two regions by a partition wall (not shown) in the radial direction of the holding member 12. In this case, as in the above, the circuit board 13 is disposed in the radially outer region, and the stator 5 of the claw-pole generator G is disposed in the radially inner region. The magnetic ring 7 is disposed on the inner diameter side facing the stator 5.

[0070] <Action and effect> This embodiment has the porous film 41 and the through-holes 42 as in the first embodiment, and provides the same effects as in the first embodiment. That is, the circuit board 13 is covered with the non-metallic lid 14. This makes it possible to prevent gas generated inside the bearing 2 from unintentionally escaping from the gas sensor SSR after it flows to the gas sensor SSR mounted on the circuit board 13. This is because the lid 14 blocks the flow of gas.

[0071] In the bearing device 1 of this embodiment, the power source PWR (see FIG. 1) is an electromagnetic induction generator (generator G) having a magnetic ring 7 fixed to the other different one of the outer ring 3 and the inner ring 4, and a coil 24 attached to the retaining member 12 so as to face the magnetic ring 7 in the radial direction of the bearing 2. A plurality of permanent magnets may be fixed to the magnetic ring 7 as a multi-pole magnet 7b, or a magnetic body having a plurality of magnetic poles may be fixed to the magnetic ring 7.

[0072] In the bearing device 1, the stator 5 and magnetic ring 7 are arranged in the radial direction to form a claw-pole type generator G. Therefore, the stator 5 and magnetic ring 7 can ensure a stable amount of power generation by the generator G. The power generated here can be used by the wireless communication circuit 18, enabling stable wireless transmission of radio waves to the outside of the bearing 2.

[0073] In the bearing device 1 according to this embodiment, only a portion of the power source capable of generating electric power is fixed to the holding member 12. The generator G serving as the power source is an electromagnetic induction generator, which includes a magnetic ring 7 and a stator 5. The stator 5 is fixed to the holding member 12. This is because the holding member 12 is the stator 5A, which is part of the stator 5, and the bobbin 23 and coil 24 that make up the stator 5 are fixed to the holding member 12. On the other hand, the magnetic ring 7 faces the stator 5 and is fixed to the inner ring 4 side, which is a rotating ring. In other words, the magnetic ring 7 is not fixed to the holding member 12. Therefore, only the components of the generator G other than the magnetic ring 7 are fixed to the holding member 12.

[0074] In the bearing device 1 of this embodiment, the wireless communication circuit 18 includes a calculation unit 18b. The wireless communication circuit 18 is mounted on a circuit board 13 fixed to the retaining member 12, and the retaining member 12 is fixed to either the outer ring 3 or the inner ring 4 included in the bearing 2. Therefore, the calculation unit 18b is arranged in the open space of the retainer 9. The calculation unit 18b wirelessly transmits the gas analysis result data received from the gas sensor SSR to the outside. Because both the gas sensor SSR and the calculation unit 18b are arranged in the open space of the retainer 9, the distance from the gas sensor SSR to the calculation unit 18b is shortened. This improves the reliability of the gas analysis result data transmitted to the outside from the calculation unit 18b (wireless communication circuit 18). This is because the data reception sensitivity of the calculation unit 18b is improved.

[0075] (Embodiment 3) FIG. 8 is an enlarged cross-sectional view of the sensor unit of FIG. 1 in embodiment 1. FIG. 9 is an enlarged cross-sectional view of the sensor unit of FIG. 10 in embodiment 3. Referring to FIGS. 8 and 9, embodiment 1 and embodiment 3 are common in that a through hole 42 is formed penetrating side plate portion 12A from back surface 12b to front surface 12f, and a porous membrane 41 is attached so as to cover through hole 42 in the axial direction. However, in embodiment 1, porous membrane 41 is disposed within through hole 42, whereas in embodiment 3, porous membrane 41 is disposed outside through hole 42 and spaced apart from through hole 42. In this respect, embodiment 3 differs from embodiment 1.

[0076] Fig. 10 is a cross-sectional view of a plane including the rotation axis of a bearing in a first example of embodiment 3. Referring to Fig. 10, in embodiment 3, the gas sensor SSR is disposed in through-hole 42. To achieve this, the gas sensor SSR is mounted on the surface of circuit board 13, to which side plate portion 12A is fixed, that faces rolling elements 8 (similar to back surface 12b). In this respect, embodiment 3 differs from embodiment 1, in which the gas sensor SSR is mounted on the surface of circuit board 13 opposite the side that faces rolling elements 8 (similar to front surface 12f).

[0077] In this embodiment, the porous film 41 is formed so as to float with respect to the through-hole 42. In other words, the porous film 41 is bonded to an area of ​​the back surface 12b adjacent to the through-hole 42. The porous film 41 covers the through-hole 42 from the rolling element 8 side in the axial direction. However, in the area overlapping with the through-hole 42, the porous film 41 has a cross-sectional shape that is bent so as to be farther away from the back surface 12b than in the area on the back surface 12b adjacent to the through-hole 42. As a result, the porous film 41 is disposed at a position overlapping with the through-hole 42 in a plan view so as to cover the through-hole 42 with a gap therebetween in the axial direction.

[0078] Fig. 11 is a cross-sectional view taken along a plane including the rotation axis of a bearing in a second example of embodiment 3. Referring to Fig. 11, the first example of Fig. 10 shows a power supply PWR similar to that in Fig. 1, whereas the second example of Fig. 11 uses a claw-pole type generator G similar to that in Fig. 3. However, the porous membrane 41 and gas sensor SSR in Fig. 11 are the same as those in Fig. 10.

[0079] As in each example of this embodiment, the gas sensor SSR may be mounted on the back surface of the circuit board 13 (the surface facing the rolling elements 8 on the inside of the bearing 2) so that it is inserted through a through-hole 42 provided in the side plate portion 12A of the retaining member 12 and is close to (or in contact with) the end face of the first cutout portion 3a of the outer ring 3. This brings the gas sensor SSR close to the outer ring 3, making it possible to accurately detect deterioration of the lubricant in the bearing 2. The effects of the porous film 41 are similar to those of the first and second embodiments.

[0080] The features described in each of the above-described embodiments (each example included therein) may be applied in an appropriate combination within the scope of technical compatibility.

[0081] 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. [Explanation of symbols]

[0082] REFERENCE SIGNS LIST 1 bearing device, 2 bearing, 3 outer ring, 3a first notch portion, 4 inner ring, 4a second notch portion, 4b outer diameter surface, 5, 5A, 5B stator, 6 sensor unit, 7 magnetic ring, 7a core metal, 7b multi-pole magnet, 7c flange portion, 8 rolling element, 9 retainer, 10 seal, 11, 20, 91, 92 end face, 12 holding member, 12A side plate portion, 12b back surface, 12f front surface, 13 circuit board, 14 lid, 15 acceleration sensor, 16 temperature sensor, 17 power supply circuit, 18 wireless communication circuit, 18a antenna portion, 18b calculation unit, 19 screw, 21, 22 magnetic member, 21a, 22a claw portion, 23 bobbin, 24 coil, 25 terminal, 31 storage battery, 41 Porous membrane, 42 through-hole, 50 annular recess, 93 recess, 94 claw, 95 pocket, PWR power supply, SSR gas sensor.

Claims

1. a bearing including an outer ring, an inner ring, and rolling elements; a holding member; the retaining member is fixed to one of the outer ring and the inner ring, the holding member includes a side plate portion having a width in a radial direction and extending along a circumferential direction, At least a portion of a power source capable of generating electric power and a circuit board are fixed to the holding member; the circuit board is fixed to a surface of the side plate portion on a side of the holding member that does not face the rolling elements in the axial direction, At least one gas sensor that detects a state of the bearing and a wireless communication circuit that wirelessly transmits an output of the gas sensor to an external device are mounted on the circuit board, a through hole is formed in the side plate portion, the through hole connecting a first surface facing the rolling element and a second surface located on the opposite side to the first surface; a porous membrane is attached so as to cover the through-hole; the power source is an electromagnetic induction generator having a magnetic ring fixed to the other different one of the outer ring and the inner ring, and a coil attached to the holding member so as to face the magnetic ring in the radial direction of the bearing, the retaining member is a part of a stator, the stator having a first stator and a second stator; a bobbin and a coil are mounted between the first stator and the second stator facing each other so as to be surrounded by the first stator and the second stator; A bearing device, wherein the first stator, the second stator, the bobbin, and the coil are arranged so as not to protrude axially outward from end faces of the outer ring and the inner ring.

2. The bearing assembly according to claim 1 , wherein the circuit board is covered with a non-metallic lid.

3. The bearing device according to claim 1 or 2, wherein the porous film is disposed in the through hole so as to close a cross section intersecting the direction in which the through hole extends.

4. The gas sensor is disposed in the through hole, The bearing device according to claim 1 or 2, wherein the porous film is disposed so as to cover the through hole at a position overlapping the through hole in plan view and spaced apart from the through hole.

5. 5. The bearing device according to claim 1, wherein the porous film is mainly composed of a fluororesin.

6. 6. The bearing device according to claim 1, wherein the gas sensor detects at least one of an aldehyde and a carboxylic acid having eight or less carbon atoms.

7. the bearing further includes a cage that holds a plurality of the rolling elements spaced apart in the circumferential direction, the cage has an open end face in the axial direction and a connected end face in the other axial direction, 7. The bearing device according to claim 1, wherein the retaining member is disposed at a position closer to the one end face side of the cage than the rolling elements.

8. The bearing device according to any one of claims 1 to 7, wherein the retaining member is made of metal.

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