Rolling Bearing Device

Abstract

To provide a structure of a rolling bearing device which can maintain sufficient conduction between an outer member and an inner member even when a rotation speed is accelerated faster and faster.SOLUTION: A deep groove ball bearing 1 includes an outer ring 2, an inner ring 3, a plurality of balls 4, and a magnetic field generation device 6. The magnetic field generation device 6 generates a magnetic field in an annular space 11 existing between an inner peripheral face of the outer ring 2 and an outer peripheral face of the inner ring 3 in a direction of an auto-rotation axis of the balls 4. Particularly, the magnetic field generated by the magnetic field generation device 6 is configured to change in magnitude in a circumferential direction of the annular space 11. By revolving the balls 4 so as to cross the magnetic field generated by the magnetic field generation device 6, the balls 4 generates electromotive force in a direction of a contact angle.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The body of an automobile becomes charged with static electricity due to friction with the air that occurs when the automobile is moving. It is known that when a certain amount of charge accumulates in the body of the automobile, insulation breakdown occurs, causing a discharge phenomenon (spark). Such sparks can cause radio noise and can damage the on-board computer.

[0003] One of the factors that causes static electricity to build up on a vehicle body is the formation of a highly insulating, non-conductive EHL oil film between the rolling elements and raceways of a rolling bearing device known as a hub unit bearing, which is used to support the wheels so that they can rotate freely, while the vehicle is traveling.

[0004] When the vehicle is stopped, the rolling elements and raceways of the rolling bearing device are in direct metal contact without an EHL oil film and are electrically connected to each other, so static electricity on the vehicle body can flow to the tire via the rolling bearing device and be discharged to the ground. However, when the vehicle is running, an EHL oil film is formed between the rolling elements and raceways, so the static electricity cannot flow from the vehicle body to the tire. In other words, the EHL oil film insulates the vehicle body from the tire. As a result, the vehicle body is easily charged with static electricity while running.

[0005] If the EHL oil film is removed from between the rolling elements and the raceways, it would be possible to suppress static electricity buildup on the vehicle body; however, because the EHL oil film contributes to lower torque and longer life for the rolling bearing device, removing the EHL oil film cannot be used as a measure to suppress static electricity buildup on the vehicle body.

[0006] In view of these circumstances, for example, JP 2015-102200 A (Patent Document 1) describes a technique for electrically connecting an outer member and an inner member, which are a pair of raceways that make up a rolling bearing device, by conductive rubber and conductive grease that make up a seal ring. According to the rolling bearing device of the conventional structure described in JP 2015-102200 A, the outer member and the inner member are electrically connected by the conductive rubber and conductive grease, so that it is possible to suppress static electricity on the vehicle body without removing the EHL oil film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-102200 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the rolling bearing device of the conventional structure described in JP 2015-102200 A has room for improvement in terms of discharging static electricity charged to the vehicle body for the following reasons.

[0009] That is, when the temperature rises or mechanical force is applied, the conductive rubber constituting the seal ring undergoes intense Brownian motion of the rubber polymer, weakening the bonding strength of the conductive components and ionic components, and the conductivity of the rubber tends to decrease. Also, when conductive grease is stirred, the bonds of the conductive components tend to break, and the conductivity of the grease tends to decrease. For this reason, the rolling bearing device of the conventional structure described in JP 2015-102200 A tends to have a lower conductivity during rotation (operation) when temperature rises or stirring occurs, and the conductivity tends to decrease as the rotation speed increases.

[0010] On the other hand, the faster the vehicle travels, the more easily the vehicle body becomes charged with static electricity. Therefore, it becomes difficult for the rolling bearing device of the conventional structure described in JP 2015-102200 A to fully discharge the static electricity that has been charged to the vehicle body while the vehicle is traveling. In addition, when carbon black is used as the conductive component contained in the conductive grease, it is likely to cause agglomeration, which may increase the rotational resistance of the rolling bearing device or cause a rough feeling (a sudden change in rolling resistance caused by carbon black agglomerates getting caught between the raceway surface and the rolling element).

[0011] As described above, the problem of a rolling bearing device insulating two components, such as between a vehicle body and a tire, and preventing static electricity from dissipating from one of the two components to the other is not a problem specific to rolling bearing devices for supporting wheels (hub unit bearings), but is a problem that can similarly arise in rolling bearing devices incorporated into the rotational support parts of various types of mechanical equipment.

[0012] The present invention has been made to solve the above-mentioned problems, and has an object to provide a rolling bearing device that can ensure sufficient electrical conductivity between the outer member and the inner member even when the rotational speed increases. [Means for solving the problem]

[0013] A rolling bearing device according to one aspect of the present invention comprises an outer member, an inner member, a plurality of rolling elements, and a magnetic field generating device. The outer member is electrically conductive and has an outer ring raceway on its inner circumferential surface. The inner member is electrically conductive and has an inner ring raceway on its outer circumferential surface. The rolling elements are electrically conductive and are disposed between the outer ring raceway and the inner ring raceway. The magnetic field generating device generates a magnetic field in a direction coinciding with the direction of the rotation axis of the rolling elements in an annular space existing between the inner circumferential surface of the outer member and the outer circumferential surface of the inner member. In addition, the direction that coincides with the direction of the rotation axis includes a direction that is approximately the same as the direction of the rotation axis, that is, a direction that is slightly tilted (about 10°) with respect to the direction of the rotation axis. In one embodiment of the rolling bearing device of the present invention, the magnetic field generated by the magnetic field generating device varies in magnitude in the circumferential direction of the annular space, and the rolling elements are caused to revolve across the magnetic field, thereby generating an electromotive force in the rolling elements in the direction of the contact angle. The direction of the magnetic field generated by the magnetic field generator does not refer to the direction of the rolling element that is located at a position deviated from the magnetic field in the circumferential direction, but refers to the direction of the rolling element that crosses the magnetic field. Also, the direction of the contact angle is a direction perpendicular to the direction of the rotation axis in a virtual plane including the revolution axis and the rotation axis, and refers to the direction of the line of action of the load acting on the rolling element.

[0014] In one embodiment of the rolling bearing device of the present invention, the magnetic field generating device has a plurality of magnetic field generating sections in which north and south poles are arranged to sandwich the rolling element on either side in the direction of the rotation axis, and the magnetic field generating sections can be arranged at equal intervals in the circumferential direction of the annular space. In this case, the number of the rolling elements can be an integer multiple of the number of the magnetic field generating sections. Alternatively, the magnetic field generating device may be configured from one magnetic field generating unit disposed at one location in the circumferential direction of the annular space. In addition, in a rolling bearing device in which a loaded zone and a non-loaded zone exist in a usage state, at least one of the magnetic field generating units among the plurality of magnetic field generating devices can be disposed in the loaded zone.

[0015] In the rolling bearing device according to one aspect of the present invention, one of the outer member and the inner member can be a stationary ring that does not rotate in use, and the other of the outer member and the inner member can be a rotating ring that rotates together with a wheel in use. In this case, the rolling bearing device becomes a hub unit bearing.

[0016] In the rolling bearing device according to one aspect of the present invention, a non-conductive lubricant can be sealed in the annular space. Alternatively, in the rolling bearing device according to one aspect of the present invention, a conductive lubricant can be sealed in the annular space. Effect of the Invention

[0017] According to the present invention, it is possible to realize a rolling bearing device that can maintain sufficient electrical continuity between the outer member and the inner member even when the rotational speed increases. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing a deep groove ball bearing according to a first embodiment as viewed from the axial direction. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a diagram corresponding to FIG. 2, showing a modification of the first example of the embodiment. [Figure 4] FIG. 4 is a half cross-sectional view showing a hub unit bearing according to a second example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [First Example of Implementation] A first embodiment will be described with reference to Figures 1 and 2. In this embodiment, a deep groove ball bearing 1 will be used as an example of a rolling bearing device. Note that with respect to deep groove ball bearing 1, the axial outer side refers to both sides in the left-right direction of Figure 2, and the axial inner side refers to the center side in the left-right direction of Figure 2.

[0020] Deep groove ball bearing 1 comprises outer ring 2 which is an outer member, inner ring 3 which is an inner member, a plurality of balls 4 each of which is a rolling element, a pair of shield plates 5a, 5b, and a magnetic field generator 6.

[0021] The outer ring 2 is made of a conductive metal such as medium carbon steel or high carbon chromium bearing steel, and is configured in an annular shape as a whole. The outer ring 2 has a deep groove type (arcuate cross section) outer ring raceway 7 in the axial middle part of the inner peripheral surface. The outer ring 2 also has locking grooves 8a, 8b on both axial outer parts of the inner peripheral surface. The radial outer ends of the shield plates 5a, 5b are locked in the locking grooves 8a, 8b. The outer ring 2 is fitted and fixed in a housing (not shown), and does not rotate even during use.

[0022] The inner ring 3 is made of a conductive metal such as medium carbon steel or high carbon chromium bearing steel, and is configured in an annular shape as a whole. The inner ring 3 is arranged radially inside the outer ring 2 and coaxially with the outer ring 2. The inner ring 3 has a deep groove type (arc-shaped cross section) inner ring raceway 9 in the axial middle part of the outer peripheral surface. The inner ring 3 also has seal grooves 10a, 10b with a U-shaped or J-shaped cross section on both axial outer sides of the outer peripheral surface. The inner ring 3 is fitted and fixed to the outside of a rotating shaft (not shown), and rotates during use.

[0023] An annular space 11 having a circular ring shape is provided between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the inner ring 3. A lubricant (grease) (not shown) is filled in the annular space 11 for the purpose of forming an EHL oil film between the outer ring raceway 7 and the inner ring raceway 9 and the rolling surfaces of the balls 4. The lubricant used in this example is a normal lubricant that has no electrical conductivity, but when implementing the present invention, a lubricant that has electrical conductivity can also be used.

[0024] The balls 4 are made of a conductive hard metal such as high carbon chromium bearing steel, and are arranged between the outer ring raceway 7 and the inner ring raceway 9 so as to be freely rollable. That is, the balls 4 are arranged in the annular space 11. The balls 4 are arranged inside the annular space 11 at equal intervals in the circumferential direction. When the inner ring 3 rotates together with the rotating shaft, the balls 4 rotate about a rotation axis R that is arranged parallel to the central axis of the deep groove ball bearing 1 and faces the left-right direction in FIG. 2. In addition, since the contact angle of the balls 4 of the deep groove ball bearing 1 is 0 degrees, the direction of the contact angle of the balls 4 (= the direction of the line of action of the load of the balls 4) faces the radial direction of the deep groove ball bearing 1 (the radial direction in FIG. 1, the vertical direction in FIG. 2). When implementing the present invention, a cage made of a non-magnetic material such as synthetic resin may be further provided to hold the balls so as to be freely rollable.

[0025] The shield plates 5a and 5b are sealing members that prevent foreign matter from entering the annular space 11. The shield plates 5a and 5b are made of corrosion-resistant metal plates such as nonmagnetic stainless steel plates, and are configured in an annular shape as a whole. The shield plates 5a and 5b are arranged at the openings on both axially outer sides of the annular space 11 so as to sandwich the ball 4 from both axial sides. Each of the shield plates 5a and 5b is fixed to the outer ring 2 by engaging the radially outer ends with the engaging grooves 8a and 8b. The radially inner ends of the shield plates 5a and 5b are closely opposed to the inner surfaces of the seal grooves 10a and 10b, and are not in contact with the inner ring 3. For this reason, the shield plates 5a and 5b constitute a non-contact type sealing device. In addition, as the sealing member, a contact seal having a structure in which an elastic material having a seal lip is vulcanized and bonded to a core metal, as described in JP 2015-102200 A, can also be used. In this case, the elastic material is made of non-conductive rubber, and the core is made of non-magnetic stainless steel plate. By making the core constituting the shield plates 5a, 5b or the contact seal out of non-magnetic stainless steel, magnetic leakage through the outer ring 2 or the inner ring 3 can be prevented.

[0026] The magnetic field generator 6 is supported by a pair of shield plates 5a, 5b fixed to the outer ring 2, and has a plurality of (four in the illustrated example) magnetic field generating units 12. When implementing the present invention, the number of magnetic field generating units 12 is not particularly limited, but may be, for example, in the range from four to the same number as the number of balls. The deep groove ball bearing 1 is used in a state where an internal gap remains after being installed between a housing (not shown) and a rotating shaft. For this reason, the deep groove ball bearing 1 is used in a state where an internal gap remains after being installed between the housing and a rotating shaft (not shown). For this reason, the deep groove ball bearing 1 has a range of less than 50% (30% to 50%) of the entire circumference as a loaded area that supports the load, and the remaining range as a non-loaded area that does not support the load. Here, a gap exists between the balls 4 in the non-loaded area and the outer ring raceway 7 or the inner ring raceway 9, so that the outer ring 2 and the inner ring 3 cannot be electrically connected. Therefore, if only one magnetic field generating unit 12 (one location) is provided in the annular space 11, it is necessary to adjust the positions of the shield plates 5a, 5b to which the magnetic field generating unit 12 is fixed, and align the phase of the deep groove ball bearing 1, so that the single magnetic field generating unit 12 is within the load zone. In contrast, if four or more magnetic field generating units 12 are provided in the annular space 11 at equal intervals in the circumferential direction, at least one magnetic field generating unit 12 will be within the load zone even when the deep groove ball bearing 1 is assembled without regard to its phase, so the work of aligning the phase of the deep groove ball bearing 1 can be omitted.

[0027] Each of the magnetic field generating units 12 is supported by a pair of shield plates 5a, 5b, and has a configuration in which the north pole and south pole are arranged to sandwich the ball 4 from both sides in the direction of the rotation axis R. For this reason, in this example, the magnetic field generating units 12 are composed of a pair of magnet elements 13a, 13b, each of which is made of a permanent magnet. When implementing the present invention, instead of magnet elements made of permanent magnets, it is also possible to use magnetized magnetic rubber vulcanized and molded on the shield plates (or the core metal constituting the contact seal) as the magnet elements.

[0028] Each of the magnet elements 13a, 13b is in the form of a piece, for example, a cylinder or a prism, has an N pole on one half, and an S pole on the other half. When the magnet elements 13a, 13b are supported by the shield plates 5a, 5b, the radial width dimension of the magnet elements 13a, 13b is smaller than the diameter of the ball 4.

[0029] One magnet element 13a constituting the magnetic field generating unit 12 is supported and fixed to the axially inner surface of the shield plate 5a with its N pole facing the ball 4 and its S pole facing the shield plate 5a. On the other hand, the other magnet element 13b constituting the magnetic field generating unit 12 is supported and fixed to a portion of the axially inner surface of the shield plate 5b whose phase in the circumferential direction coincides with that of the one magnet element 13a with its S pole facing the ball 4 and its N pole facing the shield plate 5b. Therefore, the N pole of the magnet element 13a and the S pole of the magnet element 13b are arranged opposite to each other in the axial direction. In addition, a gap slightly larger than the diameter of the ball 4 is provided between the end face of the magnet element 13a on the N pole side and the end face of the magnet element 13b on the S pole side. The means for attaching the magnet elements 13a and 13b to the shield plates 5a and 5b is not particularly limited, but they can be attached, for example, by using an adhesive. Furthermore, the mounting phases of the pair of magnet elements 13a, 13b constituting the magnetic field generating unit 12 are preferably aligned, but may be slightly out of phase (by about 10°).

[0030] Magnetic field generating unit 12 generates a magnetic field in annular space 11 in a direction that coincides with the direction of the rotation axis R of ball 4, as indicated by arrow α in Fig. 2, which exits from the north pole end face of magnet element 13a and enters the south pole end face of magnet element 13b. Specifically, the direction of the magnetic field generated by magnetic field generating unit 12 coincides with the direction of the rotation axis R of ball 4 at a portion whose circumferential position coincides with magnetic field generating unit 12 (i.e., crosses the magnetic field). Note that when the direction of the magnetic field generated by magnetic field generating unit 12 coincides with the direction of the rotation axis R of ball 4, this includes not only cases where it coincides completely with the direction of the rotation axis R, but also cases where it approximately coincides (shifted by about 10°).

[0031] In this example, the magnetic field generating unit 12 consisting of a pair of magnet elements 13a, 13b is disposed at equal intervals in the circumferential direction of the annular space 11. Therefore, the magnetic field generating device 6 of this example generates a magnetic field in a direction that coincides with the direction of the rotation axis R of the ball 4 at a plurality of points at equal intervals in the circumferential direction of the annular space 11. Therefore, the magnitude of the magnetic field generated in the annular space 11 is larger in a portion where the phase in the circumferential direction coincides with the magnetic field generating unit 12 than in a portion where the phase in the circumferential direction is out of the magnetic field generating unit 12. As a result, the magnetic field generated by the magnetic field generating device 6 of this example changes in magnitude in the circumferential direction of the annular space 11. In other words, the magnetic field generating device 6 generates a magnetic field that is not uniform in the circumferential direction of the annular space 11. Specifically, the magnitude of the magnetic field generated by the magnetic field generating device 6 (magnetic field strength) alternates between large and small in the circumferential direction of the annular space 11.

[0032] In this example, the number (total number) of magnetic field generating units 12 is regulated in relation to the number (total number) of balls 4. That is, the number of balls 4 and the number of magnetic field generating units 12 are regulated so that the number of balls 4 is an integer multiple of the number of magnetic field generating units 12. Note that Fig. 1 shows a case where the number of balls 4 is eight, which is twice the number of magnetic field generating units 12.

[0033] When deep groove ball bearing 1 is in operation (when inner ring 3 is rotating), balls 4 rotate about rotation axis R oriented in the left-right direction in Fig. 2, while revolving around annular space 11 about the central axis of deep groove ball bearing 1. As balls 4 revolve around annular space 11, they cross the magnetic field generated by magnetic field generator 6 in the circumferential direction. Because balls 4 are made of a conductive metallic material, when they cross the magnetic field, an electromotive force is generated in ball 4 in the direction of the contact angle (up and down direction in Fig. 2) according to Fleming's right-hand rule.

[0034] Specifically, when the direction of the magnetic field is the direction of the arrow α in FIG. 2 and the balls 4 revolve from the front side to the back side in FIG. 2 (revolving in the direction of the arrow X in FIG. 1), an electromotive force is generated in the balls 4 in the radially inward direction (the lower side in FIG. 2). Therefore, when the outer ring 2 side is positively charged or the inner ring 3 side is negatively charged, static electricity can be removed efficiently. On the other hand, when the direction of the magnetic field is the direction of the arrow α in FIG. 2 and the balls 4 revolve from the back side to the front side in FIG. 2 (revolving in the direction of the arrow Y in FIG. 1), an electromotive force is generated in the balls 4 in the radially outward direction (the upper side in FIG. 2). Therefore, static electricity can be removed efficiently when the outer ring 2 side is negatively charged or the inner ring 3 side is positively charged. If the static electricity removal direction does not match, the static electricity removal direction can be matched by swapping the left and right sides of the deep groove ball bearing 1 and assembling them.

[0035] In particular, in the deep groove ball bearing 1 of this example, the magnetic field generating unit 12 is arranged at multiple locations in the circumferential direction of the annular space 11, and since the magnetic field in the circumferential direction of the annular space 11 is not uniform, the electromotive force generated in the balls 4 becomes a pulse wave electromotive force (an electromotive force that changes periodically between a maximum value and a minimum value whose sign does not change). For this reason, a pulse wave current tries to flow in the balls 4 every time they cross the magnetic field generated by the magnetic field generating unit 12.

[0036] Since the annular space 11 is filled with lubricant, a highly insulating non-conductive EHL oil film is formed between the outer ring raceway 7 and inner ring raceway 9 in the load zone and the rolling elements of the balls 4. However, a pulse-shaped electromotive force is generated in the balls 4 every time they cross the magnetic field generated by the magnetic field generating unit 12, causing a dielectric phenomenon in the EHL oil film, allowing current to pass through the EHL oil film. In other words, a displacement current flows in the EHL oil film, just as when a voltage whose magnitude changes over time is applied to a capacitor. In this example, this principle is used to make the outer ring 2 and the inner ring 3 conductive.

[0037] Furthermore, the higher the rotational speed of deep groove ball bearing 1 (the rotational speed of inner ring 3), the higher the orbital speed of balls 4 and the more frequently balls 4 cross the magnetic field (the shorter the time interval), and therefore the frequency of the generated pulse-shaped electromotive force increases. For this reason, the conductive effect between outer ring 2 and inner ring 3 due to the dielectric phenomenon increases as the rotational speed of deep groove ball bearing 1 increases. Therefore, with the deep groove ball bearing 1 of this example, sufficient conductivity can be achieved between outer ring 2 and inner ring 3 even when the rotational speed increases.

[0038] Furthermore, the deep groove ball bearing 1 of this example can utilize the pulse-shaped electromotive force generated in the balls 4 to dissipate (remove) static electricity from one of the housing in which the outer ring 2 is fitted and the rotating shaft on which the inner ring 3 is fitted (the one that is charged and has a higher absolute value of voltage) to the other.

[0039] In the deep groove ball bearing 1 of this embodiment, a pulse-shaped electromotive force is generated in the balls 4, causing a dielectric phenomenon in the EHL oil film, thereby establishing electrical continuity between the outer ring 2 and the inner ring 3, so that a normal (non-conductive) lubricant can be used as the lubricant. Therefore, electrical continuity can be established between the outer ring 2 and the inner ring 3 without sacrificing the low torque and long life of the deep groove ball bearing 1.

[0040] Also, unlike the discharge phenomenon caused by insulation breakdown, no electrolytic corrosion occurs on the outer ring raceway 7, inner ring raceway 9, and rolling surfaces of the balls 4, so there is no reduction in the bearing life. Also, since there is no need to use conductive grease, there is no increase in rotational resistance of the deep groove ball bearing 1 or a rough feeling, as occurs when carbon black is used as a conductive component.

[0041] Furthermore, in this example, since the number of balls 4 is an integer multiple of the number of magnetic field generating units 12, the phases of the currents generated in the balls 4 at multiple locations in the circumferential direction of the annular space 11 in which the magnetic field generating units 12 are arranged can be made to be in phase. This allows current to flow simultaneously through multiple balls 4, and the total amount of instantaneous current flowing between the outer ring 2 and the inner ring 3 can be increased. This prevents the timing of the two currents from being out of sync, as occurs when, for example, the magnetic field generating units are arranged at two diametrically opposite locations in the annular space and the number of balls is an odd number. This allows effective electrical continuity between the outer ring 2 and the inner ring 3.

[0042] Even if a conductive lubricant (grease) is used instead of a non-conductive lubricant, the lubricant has dielectric properties similar to a capacitor in addition to being conductive, so the pulse-shaped electromotive force generated in the balls can increase the electrical conductivity between the outer and inner rings.In addition, the movement of the lubricant induces current in the conductive components, further increasing the electrical conductivity.

[0043] [Modification of the first embodiment] A modification of the first embodiment will be described with reference to FIG.

[0044] In this example, the deep groove ball bearing 1 has an outer ring 2a and an inner ring 3a each made of non-magnetic stainless steel, and the structure of the multiple magnetic field generating units 12a that make up the magnetic field generating device 6a is changed from the structure in the first example of the embodiment.

[0045] That is, in the magnetic field generating device 6a of this example, each of the multiple magnetic field generating units 12a is composed of only one magnet element 13c supported by one of the shield plates 5a (5b). In this example, contact seals such as those described in JP 2015-102200 A can be used instead of the shield plates 5a and 5b.

[0046] Each of the magnet elements 13c is in the form of a piece, for example, a cylinder or a prism, and has an N pole on one half and an S pole on the other half. The magnet elements 13c are supported and fixed to the axially inner surface of the shield plate 5a (5b) with the N pole (or S pole) facing the ball 4 and the S pole (or N pole) facing the shield plate 5a (5b).

[0047] Magnetic field generating unit 12a generates a magnetic field in annular space 11 in a direction that coincides with the direction of the rotation axis of ball 4, exiting from the N-pole end face of magnet element 13c and entering (returning) to the S-pole end face of magnet element 13c. Note that the magnitude (magnetic field strength) of the magnetic field generated by magnetic field generating unit 12a is smaller than the magnitude of the magnetic field generated by magnetic field generating unit 12 according to the first example of the embodiment.

[0048] In this example, magnetic field generating units 12a having the above-mentioned configuration are arranged at equal intervals in the circumferential direction of annular space 11. Therefore, in the case of magnetic field generating device 6a of this example as well, a magnetic field in a direction coinciding with the direction of the rotation axis of ball 4 is generated at multiple points at equal intervals in the circumferential direction of annular space 11. In other words, magnetic field generating device 6a generates a magnetic field that is not uniform in the circumferential direction of annular space 11.

[0049] In the case of this example as described above, the conductivity effect is lower than in the structure of the first example of the embodiment, but it is possible to establish conductivity between the outer ring 2a and the inner ring 3a by generating a pulse-shaped electromotive force in the balls 4 and causing a dielectric phenomenon in the EHL oil film. Also, because the magnetic field generating unit 12a is composed of only one magnet element 13c, the weight and cost of the rolling bearing device 1 can be reduced. The other configurations and effects are the same as those of the first embodiment.

[0050] [Second Example of the Implementation Form] A second embodiment of the present invention will be described with reference to Fig. 4. In this embodiment, a hub unit bearing 14 for rotatably supporting an automobile wheel will be used as an example of a rolling bearing device.

[0051] The hub unit bearing 14 is an inner ring rotating type, so-called third generation hub unit bearing for a driven wheel. The hub unit bearing 14 includes an outer ring 15 as an outer member, a hub 16 as an inner member, a plurality of rolling elements 17a, 17b, a seal ring 18, a cap 19, and a pair of magnetic field generators 20a, 20b. With regard to hub unit bearing 14, the axially outer side is the left side in FIG. 4, which is the outer side in the width direction of the vehicle when assembled to the vehicle, and the axially inner side is the right side in FIG. 4, which is the center side in the width direction of the vehicle when assembled to the vehicle.

[0052] The outer ring 15 is made of a conductive metal such as medium carbon steel and has a generally cylindrical shape. The outer ring 15 has double-row outer ring raceways 21a, 21b on its inner circumferential surface, and a stationary flange 22 protruding radially outward at the axially middle portion of its outer circumferential surface. The stationary flange 22 has support holes 23 penetrating in the axial direction at multiple locations in the circumferential direction. The outer ring 15 is supported and fixed to a suspension device constituting the vehicle body by bolts inserted into the support holes 23, and does not rotate even when the wheels rotate.

[0053] Hub 16 is disposed radially inside outer ring 15 and coaxially therewith, and is formed by combining a hub ring 24 made of a conductive metal such as medium carbon steel with an inner ring 25 made of a conductive metal such as high carbon chromium steel. Hub 16 has double row inner ring raceways 26a, 26b on the outer circumferential surface in portions facing double row outer ring raceways 21a, 21b.

[0054] The hub ring 24 is a shaft member that fits and holds the inner ring 25, and has a shaft portion 27, a rotation flange 28, and a pilot portion 29. In this example, the hub unit bearing 14 is for a driven wheel, so the hub ring 24 is configured to be solid. However, when the present invention is applied to a hub unit bearing for a driving wheel, a hub ring having a spline hole that penetrates in the axial direction at the radial center can be used. A drive shaft that constitutes a constant velocity joint is splined into the spline hole.

[0055] The shaft portion 27 is provided in a range extending from the axially inner portion to the axially intermediate portion of the hub wheel 24. The shaft portion 27 has, at its axially inner portion, a small diameter portion 30 on which the inner ring 25 is fitted, the outer diameter of which is smaller than that of the portion adjacent to it on the axially outer side, and has an outer row of inner ring raceways 26a on the outer peripheral surface of the axially intermediate portion. The shaft portion 27 has, at its axially inner end portion, a crimping portion 31 for pressing the axially inner end face of the inner ring 25. When carrying out the present invention, a male thread portion may be formed on the outer peripheral surface of the axially inner end portion of the shaft portion, and the inner ring may be fixed to the hub wheel by screwing a nut onto the male thread portion.

[0056] The rotating flange 28 is provided on a portion of the hub wheel 24 that is located axially outward of the axially outer end of the outer ring 15, and has a generally circular ring shape. The rotating flange 28 has mounting holes 32 penetrating in the axial direction at multiple circumferential positions in a radially intermediate portion. A stud 33 is press-fitted into each of the mounting holes 32. A nut (not shown) is screwed into the tip of the stud 33. In this way, the wheel and braking rotor that constitute the wheel are fixed to the axially outer side of the rotating flange 28. When carrying out the present invention, a female threaded hole may be formed in the rotating flange, and a hub bolt may be directly screwed into the female threaded hole to fix the wheel and braking rotor to the axially outer side of the rotating flange.

[0057] The pilot portion 29 is provided at the axially outer end of the hub wheel 24 so that the wheel and the braking rotor are fitted thereto with a clearance fit without any rattle, and has a generally cylindrical shape.

[0058] The inner ring 25 has an annular shape and has an inner ring raceway 26b in the axially inner row at the axially middle portion of the outer circumferential surface. The inner ring 25 is fitted onto the small diameter portion 30 of the shaft portion 27 by interference fit.

[0059] An annular space 11a having a circular ring shape is provided between the inner peripheral surface of the outer ring 15 and the outer peripheral surface of the hub 16. In the present embodiment, annular space 11a is filled with a non-conductive lubricant (grease) (not shown) for the purpose of forming an EHL oil film between the outer ring raceways 21a, 21b and the inner ring raceways 26a, 26b and the rolling surfaces of the rolling elements 17a, 17b.

[0060] The rolling elements 17a, 17b are made of conductive hard metal such as high carbon chromium bearing steel. The rolling elements 17a in the outer row arranged on the axially outer side are arranged at equal intervals in the circumferential direction between the outer ring raceway 21a and the inner ring raceway 26a, and are rollably held by a cage 34a made of a non-magnetic material such as synthetic resin. On the other hand, the rolling elements 17b in the inner row arranged on the axially inner side are arranged at equal intervals in the circumferential direction between the outer ring raceway 21b and the inner ring raceway 26b, and are rollably held by a cage 34b made of a non-magnetic material such as synthetic resin. As a result, the hub 16 is supported rotatably on the radially inner side of the outer ring 15.

[0061] In this example, balls are used as the rolling elements 17a, 17b, but tapered rollers can be used instead of balls. Also, in this example, the pitch circle diameter of the rolling elements 17a in the axially outer row and the pitch circle diameter of the rolling elements 17b in the axially inner row are made the same, but the pitch circle diameter of the rolling elements in the axially outer row and the pitch circle diameter of the rolling elements in the axially inner row can be made different from each other.

[0062] The seal ring 18 closes the axially outer opening of the annular space 11a. The seal ring 18 includes a core metal 35 and a seal material 36.

[0063] The core metal 35 is formed into an annular shape by bending a non-magnetic stainless steel plate. The core metal 35 is fitted and fixed to the outer ring 15 at the end on the outer side in the axial direction.

[0064] The seal material 36 is made of an elastic material such as an elastomer like rubber, and is supported and fixed to the core metal 35 by vulcanization adhesion. The seal material 36 has at least one seal lip 37 (three in the illustrated example). The tip of each seal lip 37 is in sliding contact with the outer circumferential surface of the shaft portion 27 and / or the axially inner surface of the rotating flange 28 over the entire circumference.

[0065] The cap 19 is fitted into the axially inner end of the outer ring 15 and closes the axially inner opening of the outer ring 15. The cap 19 is made of non-magnetic stainless steel plate or resin, and is configured as a cylinder with a bottom as a whole. That is, the cap 19 includes a cylindrical fitting tubular portion 38 that is fitted into the axially inner end of the outer ring 15, and a bottom plate portion 39 that bends radially inward from the axially inner end of the fitting tubular portion 38 and closes the axially inner opening of the fitting tubular portion 38.

[0066] The magnetic field generating device 20a is disposed in the axially outer space of the annular space 11a in which the rolling elements 17a in the axially outer row are arranged. О In contrast, the magnetic field generating device 20b generates a magnetic field in a direction that coincides with the direction of the rotation axis R of the rolling elements 17b in the axially inner space of the annular space 11a where the rolling elements 17b in the axially inner row are arranged. i It generates a magnetic field in a direction that matches the direction of the magnet.

[0067] The magnetic field generating device 20a has a plurality of magnetic field generating units 40a. Each of the magnetic field generating units 40a rotates the rolling element 17a along the rotation axis R. О The magnetic field generating unit 40a has a configuration in which the N pole and the S pole are arranged so as to sandwich the N pole and the S pole from both sides in the direction of the magnetic field. For this reason, in this example, the magnetic field generating unit 40a is composed of a pair of magnet elements 41 and 42, each of which is made of a permanent magnet.

[0068] The magnetic field generating device 20b has a plurality of magnetic field generating units 40b. In this example, the number of the magnetic field generating units 40b constituting the magnetic field generating device 20b is the same as the number of the magnetic field generating units 40a constituting the magnetic field generating device 20a, and the plurality of magnetic field generating units 40b are arranged in the same phase as the plurality of magnetic field generating units 40a. Each of the magnetic field generating units 40b has a rolling element 17b aligned with the rotation axis R. i The magnetic field generating unit 40b has a configuration in which the N pole and the S pole are arranged so as to sandwich the N pole and the S pole from both sides in the direction of the magnetic field. For this reason, in this example, the magnetic field generating unit 40b is composed of a pair of magnet elements 42 and 43, each of which is made of a permanent magnet.

[0069] In this way, in this example, one magnet element 42 is used for both the magnetic field generating unit 40a and the magnetic field generating unit 40b. In other words, the magnet element 42 is used not only for constituting the magnetic field generating unit 40a, but also for constituting the magnetic field generating unit 40b.

[0070] Each of the magnet elements 41, 42, 43 is in the form of a piece, for example, a cylinder or a prism, with an N pole on one half and an S pole on the other half. In the illustrated example, the size of the magnet element 41 arranged on the axially outer side is smaller than the size of the magnet element 42 arranged in the axially middle part and the magnet element 43 arranged on the axially inner side, but when implementing the present invention, the sizes of the magnet elements 41, 42, 43 can be changed as appropriate. In addition, although the magnitude of the magnetic field will be smaller, the magnet element 42 can also be replaced with a non-magnetic ferromagnetic material.

[0071] The magnet element 41 constituting the magnetic field generating unit 40a is supported and fixed to the axial inner surface of the core metal 35 constituting the seal ring 18 with its south pole facing the rolling body 17a and its north pole facing the seal ring 18.

[0072] In addition, when implementing the present invention, the magnet element 41 constituting the magnetic field generating unit 40a can be replaced with a magnet element made of a permanent magnet, and magnetic rubber can be vulcanized and bonded separately from the sealing material constituting the seal ring, and the magnetic rubber material can be magnetized to use the magnetized part as the magnet element.

[0073] The magnet elements 42 constituting the magnetic field generating units 40a and 40b are supported by a holder 44 at the axial middle part of the inner circumferential surface of the outer ring 15 with their N poles facing the rolling elements 17a in the axial outer row and their S poles facing the rolling elements 17b in the axial inner row. The holder 44 is made of a non-magnetic material such as synthetic resin, and is supported and fixed to the axial middle part of the inner circumferential surface of the outer ring 15.

[0074] The magnet element 43 constituting the magnetic field generating unit 40b is supported and fixed to the axially outer surface of the bottom plate portion 39 constituting the cap 19 with the N pole facing the rolling element 17b and the S pole facing the cap 19. The means for attaching the magnet element 41 to the seal ring 18, the means for attaching the magnet element 42 to the holder 44, and the means for attaching the magnet element 43 to the cap 19 are not particularly limited, and may be attached, for example, by using an adhesive.

[0075] The magnetic field generating unit 40a is disposed in the space axially outside the annular space 11a, and extends from the N-pole end face of the magnet element 42 to the S-pole end face of the magnet element 41 along the axis R of the rotation axis of the rolling element 17a. О On the other hand, the magnetic field generating unit 40b generates a magnetic field in a direction that coincides with the direction of the rotation axis R of the rolling element 17b, which exits from the N-pole end face of the magnet element 43 and enters the S-pole end face of the magnet element 42, in the space on the axial inside of the annular space 11a. i The hub unit bearing 14 for rotatably supporting the right wheel and the hub unit 14 for rotatably supporting the left wheel rotate in opposite directions when the vehicle is traveling forward (or backward), so the magnetic fields generated by the magnetic field generating units 40a, 40b are directed in opposite directions for the hub unit bearing 14 for the right wheel and the hub unit bearing 14 for the left wheel.

[0076] In this embodiment, the magnetic field generating unit 40a, which is composed of a pair of magnet elements 41 and 42, is disposed at equal intervals in the circumferential direction of the annular space 11a. Therefore, the magnetic field generating device 20a detects the rotation axis R of the rolling element 17a at a plurality of points at equal intervals in the circumferential direction of the annular space 11a.О The magnetic field generating device 20a generates a magnetic field in a direction that coincides with the direction of the magnetic field generating unit 40a. Therefore, the magnitude of the magnetic field generated in the axially outer portion of the annular space 11a is larger in a portion where the phase in the circumferential direction coincides with the magnetic field generating unit 40a than in a portion where the phase in the circumferential direction is out of the magnetic field generating unit 40a. As a result, the magnetic field generated by the magnetic field generating device 20a of this example changes in magnitude in the circumferential direction of the annular space 11a. In other words, the magnetic field generating device 20a generates a magnetic field that is not uniform in the circumferential direction of the annular space 11a. Specifically, the magnitude of the magnetic field generated by the magnetic field generating device 20a (magnetic field strength) alternates between large and small in the circumferential direction of the annular space 11a.

[0077] In this example, the magnetic field generating unit 40b, which is composed of a pair of magnet elements 42 and 43, is disposed at equal intervals in the circumferential direction of the annular space 11a. Therefore, the magnetic field generating device 20b detects the rotation axis R of the rolling element 17b at a plurality of points at equal intervals in the circumferential direction of the annular space 11a. i Therefore, the magnitude of the magnetic field generated in the axially inner portion of the annular space 11a is greater in the portion where the phase in the circumferential direction coincides with the magnetic field generating unit 40b than in the portion where the phase in the circumferential direction deviates from the magnetic field generating unit 40b. As a result, the magnetic field generated by the magnetic field generating device 20b of this embodiment is larger in the annular space 11a than in the portion where the phase in the circumferential direction deviates from the magnetic field generating unit 40b. 11a The magnitude of the magnetic field (magnetic field strength) generated by the magnetic field generating device 20b changes in the circumferential direction of the annular space 11a. In other words, the magnetic field generating device 20b generates a magnetic field that is not uniform in the circumferential direction of the annular space 11a. Specifically, the magnitude of the magnetic field (magnetic field strength) generated by the magnetic field generating device 20b changes alternately between large and small in the circumferential direction of the annular space 11a.

[0078] In this example, the number of magnetic field generating units 40a is regulated in relation to the number of rolling bodies 17a, and the number of magnetic field generating units 40b is regulated in relation to the number of rolling bodies 17b. That is, the number of rolling bodies 17a and the number of magnetic field generating units 40a are regulated so that the number of rolling bodies 17a is an integer multiple of the number of magnetic field generating units 40a, and the number of rolling bodies 17b and the number of magnetic field generating units 40b are regulated so that the number of rolling bodies 17b is an integer multiple of the number of magnetic field generating units 40b.

[0079] When the hub unit bearing 14 is in operation, each of the rolling elements 17a and 17b is aligned with the rotation axis R О , R i While rotating about the axis R, the rolling elements 17a of the axially outer row revolve around the annular space 11a about the central axis O of the hub unit bearing 14. When the rolling elements 17a of the axially outer row revolve around the annular space 11a, the rolling elements 17a cross the magnetic field generated by the magnetic field generating device 20a in the circumferential direction. Therefore, according to Fleming's right-hand rule, the rolling elements 17a are rotated in the direction of the contact angle (the rotation axis R О In addition, when the rolling elements 17b in the axially inner row revolve around the annular space 11a, the rolling elements 17b cross the magnetic field generated by the magnetic field generating device 20b in the circumferential direction. Therefore, according to Fleming's right-hand rule, an electromotive force is generated in the rolling elements 17b in the direction of the contact angle (direction perpendicular to the rotation axis R). i In addition, since the vehicle body is usually charged positively, the direction of the magnetic field generated by the magnetic field generating units 40a, 40b and the revolution direction of the rolling elements 17a, 17b when the vehicle is traveling forward are regulated so that an electromotive force directed radially inward is generated in the rolling elements 17a, 17b when the vehicle is traveling forward (or backward).

[0080] In the hub unit bearing 14 of this example, the magnetic field generating units 40a, 40b are each disposed at multiple locations in the circumferential direction of the annular space 11a, and since the magnetic field in the circumferential direction of the annular space 11a is not uniform, the electromotive force generated in the rolling elements 17a, 17b becomes a pulse wave electromotive force. Therefore, a pulse wave current tries to flow in each of the rolling elements 17a, 17b every time they cross the magnetic field generated by the magnetic field generating units 40a, 40b.

[0081] Therefore, in this example as well, an electromotive force is generated in the rolling elements 17a, 17b, causing a dielectric phenomenon in the EHL oil film, thereby establishing electrical continuity between the outer ring 15 and the hub 16. As a result, static electricity charged to the vehicle body can be efficiently released to the tire side through the hub unit bearing 14.

[0082] In addition, since rubber tires have electrical characteristics as a parallel circuit of resistors and capacitors, the conduction by pulse-wave electromotive force reduces the resistance value and enhances the effect of removing static electricity from the vehicle body. Therefore, as in this example, by restricting the number of rolling bodies 17a and the number of magnetic field generating units 40a so that the number of rolling bodies 17a is an integer multiple of the number of magnetic field generating units 40a, and restricting the number of rolling bodies 17b and the number of magnetic field generating units 40b so that the number of rolling bodies 17b is an integer multiple of the number of magnetic field generating units 40b, the phases of the currents generated by the multiple magnetic field generating units 40a can be made the same, and the phases of the currents generated by the multiple magnetic field generating units 40b can be made the same, so that the conduction to the tire can be improved.

[0083] Furthermore, as the rotational speed of the hub unit bearing 14 (the rotational speed of the hub 16) increases, the revolution speed of the rolling elements 17a, 17b increases, and the rolling elements 17a, 17b cross the magnetic field more frequently (the time interval becomes shorter), so the frequency of the generated pulsed current increases. For this reason, the conduction effect between the outer ring 15 and the hub 16 increases as the rotational speed of the hub unit bearing 14 increases. Therefore, with the hub unit bearing 14 of this example, the conduction effect between the outer ring 15 and the hub 16 can be improved as the vehicle speed increases and the vehicle body is more likely to be charged with static electricity, and the static electricity charged on the vehicle body can be efficiently released to the tire side. The other configurations and effects are the same as those of the first embodiment.

[0084] Although not shown in the figures, as a modified example of the second embodiment, the magnet element 41 constituting the magnetic field generating unit 40a arranged on the axially outer side can be omitted, and the magnetic field generating unit 40a can be composed of only the magnet element 42. Alternatively, the magnet element 42 constituting the magnetic field generating unit 40a arranged on the axially outer side can be omitted, and the magnetic field generating unit 40a can be composed of only the magnet element 41, and the magnetic field generating unit 40b can be composed of only the magnet element 43. In these cases, the conductive effect of the hub unit bearing 14 is reduced, but the conductive effect generated in each of the axially outer row and the axially inner row can be improved. Pulse WaveSince the electromotive forces generated by the two electrodes do not cancel each other out, the electrical conductivity of the tire can be improved.

[0085] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of the examples of the embodiment can be combined as appropriate as long as no contradiction occurs.

[0086] When implementing the present invention, if a plurality of magnetic field generating units constituting the magnetic field generating device are provided, the plurality of magnetic field generating units can be arranged at unequal intervals in the circumferential direction. Also, only one magnetic field generating unit constituting the magnetic field generating device can be provided. Furthermore, the magnet element constituting the magnetic field generating unit can be made of a permanent magnet, or can be formed by magnetizing magnetic rubber. Also, the shape and size of the magnet element are not limited to the structures of each example of the embodiment, and can be changed as appropriate. Furthermore, the rolling bearing device of the present invention is not limited to deep groove ball bearings and hub unit bearings, and can be applied to various bearings, such as angular ball bearings, cylindrical roller bearings, needle bearings, tapered roller bearings, and spherical roller bearings, regardless of whether they are single row or double row. Also, the rolling bearing device of the present invention is not limited to inner ring rotating type, but can be applied to outer ring rotating type structures. [Explanation of symbols]

[0087] 1 Deep groove ball bearing 2, 2a Outer ring 3, 3a Inner ring 4 balls 5a, 5b Shield plate 6, 6a Magnetic field generator 7 Outer raceway 8a, 8b Locking groove 9 Inner raceway 10a, 10b Seal groove 11, 11a Annular space 12, 12a Magnetic field generating unit 13a, 13b, 13c magnet elements 14 Hub unit bearing 15 Outer ring 16 Hub 17a, 17b rolling elements 18 Seal ring 19 Cap 20a, 20b Magnetic field generating device 21a, 21b Outer raceway 22 Stationary Flange 23 Support hole 24 Hub wheel 25 Inner Circle 26a, 26b Inner raceway 27 Shaft 28 Rotating flange 29 Pilot Division 30 Small diameter section 31 Crimping part 32 Mounting hole 33 Stud 34a, 34b retainer 35 Core wire 36 Sealing material 37 Sealing lip 38 Fitting cylinder part 39 Bottom plate part 40a, 40b magnetic field generating unit 41 Magnet element 42 Magnet element 43 Magnet Element 44 Holder

Claims

1. an outer member having electrical conductivity and including an outer ring raceway on an inner circumferential surface thereof; an inner member having electrical conductivity and including an inner ring raceway on an outer circumferential surface thereof; a plurality of rolling elements having electrical conductivity, the rolling elements being disposed between the outer ring raceway and the inner ring raceway; a magnetic field generating device that generates a magnetic field in a direction that coincides with the direction of the rotation axis of the rolling elements in an annular space that exists between an inner peripheral surface of the outer member and an outer peripheral surface of the inner member, The magnetic field generated by the magnetic field generating device varies in magnitude in the circumferential direction of the annular space, By revolving the rolling body so as to cross the magnetic field, an electromotive force is generated in the rolling body in the direction of the contact angle. Rolling bearing device.

2. the magnetic field generating device has a plurality of magnetic field generating units each having a north pole and a south pole arranged to sandwich the rolling element from both sides in the direction of the rotation axis, The magnetic field generating units are arranged at equal intervals in the circumferential direction of the annular space.

2. A rolling bearing device according to claim 1.

3. 3. The rolling bearing device according to claim 2, wherein the number of said rolling elements is an integer multiple of the number of said magnetic field generating sections.

4. one of the outer member and the inner member is a stationary wheel that does not rotate during use; The other of the outer member and the inner member is a rotating wheel that rotates together with the wheel during use. A rolling bearing device according to any one of claims 1 to 3.

5. 5. The rolling bearing device according to claim 1, wherein a non-conductive lubricant is sealed in the annular space.

Images