Rolling bearing
Patent Information
- Application Number
- JP2024051632
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-10-09
Smart Images
Figure 2025150638000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a rolling bearing. [Background technology]
[0002] For example, when a shaft provided in a drive motor or reducer of an electric axle unit (so-called e-Axle) of an electric vehicle or the like is supported by a rolling bearing so that it can rotate freely relative to a housing, the inner diameter surface of the inner ring or the outer diameter surface of the outer ring may be clearance-fitted into the mating shaft or housing.
[0003] In recent years, housings have been made thinner to make electric axle units more compact. When the outer diameter surface of the outer ring and the housing are loosely fitted, the thinner housing lengthens the contact area between the outer ring and the housing in the load-bearing zone of the rolling bearing in the circumferential direction. This increases the risk of creep, a mechanism in which traveling waves generated on the outer diameter surface of the outer ring during rotation of the rolling bearing cause the outer ring to move relative to the housing in the orbital direction of the rolling elements. To prevent this creep, it has been proposed to form a relief surface that divides the inner diameter surface of the inner ring (the mating surface with the shaft) or the outer diameter surface of the outer ring (the mating surface with the housing) over its entire width (Patent Documents 1 to 3).
[0004] The flanks proposed in Patent Documents 1 to 3 have a radial depth relative to an imaginary circle tangent to the inner diameter surface of the inner ring or the outer diameter surface of the outer ring, and form a radial gap with the mating member, which is a shaft or housing. Even when the rolling bearing is subjected to a maximum radial load, a radial gap remains between the flank and the mating member. Therefore, even if creep occurs due to the mechanism described above, when the flank of the inner ring or outer ring reaches the load bearing area due to creep, the traveling wave is blocked at the flank, and creep is suppressed. [Prior art documents] [Patent documents]
[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-45987 [Patent Document 2] Patent No. 7108569 [Patent Document 3] Japanese Patent Application Publication No. 2020-190289 Summary of the Invention [Problem to be solved by the invention]
[0006] In recent years, drive motors for electric axle units have been inverter-controlled, and efforts are being made to increase the output of their driving force. As a result, it is expected that in the future, the potential difference between the housing that houses the drive motor and reducer and the shaft of the drive motor or reducer will increase, causing discharges between the rolling elements and raceway surfaces of the rolling bearings that support the shafts relative to the housing, increasing the risk of electrolytic corrosion on the rolling elements and raceway surfaces.
[0007] Patent Documents 1 to 3 do not mention suppressing electrolytic corrosion of rolling bearings.
[0008] Patent Document 1 merely discloses that the inner or outer ring is cut to form a flank.
[0009] Patent Document 2 discloses forming the inner diameter surface and flank of the inner ring or the outer diameter surface and flank of the outer ring by forming a base film by phosphate treatment on the inner or outer circumference of a metal ring, including the raceway surface, and then applying a resin solid lubricant, which is a resin-based binder mixed with PTFE, once or in multiple coats onto the base film, or omitting the base film and applying a resin solid lubricant once or in multiple coats onto the inner or outer circumference of the metal ring. In this case, the phosphate base film and resin solid lubricant film are insulating, so it is possible that the inner circumference of the inner ring and the shaft, or the outer circumference of the outer ring and the housing, will be electrically insulated.
[0010] However, in the rolling bearing disclosed in Patent Document 2, only the inner diameter surface and flank of the inner ring or the outer diameter surface and flank of the outer ring are formed with a resin solid lubricant film or the like, and the width surface of the inner ring or the width surface of the outer ring is not covered with a coating or the like. Rolling bearings that support the motor shaft of an electric axle unit or the transmission shaft of a reducer are generally supported in the axial direction by the width surface of the inner ring or the width surface of the outer ring against the abutting portion of the corresponding shaft or the abutting portion of the housing. If the rolling bearing disclosed in Patent Document 2 is used in such a bearing support structure, there is no insulation between the width surface of the inner ring or the width surface of the outer ring and the corresponding shaft or housing, and therefore the above-mentioned electrolytic corrosion cannot be suppressed.
[0011] Patent Document 3 discloses a rolling bearing in which the inner ring or outer ring is composed of a metal ring and a buildup member, and the inner diameter surface and flank of the inner ring or the outer diameter surface and flank of the outer ring are formed by fixing the buildup member to the metal ring, and the buildup member is an integrally molded resin product.If this rolling bearing is used in the above-mentioned bearing support structure, it may be possible to achieve insulation between the inner peripheral portion of the inner ring and the shaft, or between the outer peripheral portion of the outer ring and the housing, but there is no insulation between the width surface of the inner ring or the width surface of the outer ring and the abutting portion of the corresponding shaft or abutting portion of the housing, so the above-mentioned electrolytic corrosion cannot be suppressed.
[0012] In view of the above background, the problem that the present invention aims to solve is to provide a rolling bearing that is suitable for electric axle units and that can suppress creep of a traveling wave type inner or outer ring while suppressing electrolytic corrosion of the inner and outer rings and rolling elements. [Means for solving the problem]
[0013] In order to achieve the above object, the present invention provides a bearing comprising: an inner ring having a first outer peripheral portion including a first raceway surface, a first inner peripheral portion including an inner diameter surface along the circumferential direction, and a first width surface extending radially at a side portion between the first outer peripheral portion and the first inner peripheral portion; an outer ring having a second inner peripheral portion including a second raceway surface, a second outer peripheral portion including an outer diameter surface along the circumferential direction, and a second width surface extending radially at a side portion between the second inner peripheral portion and the second outer peripheral portion; and a plurality of rolling elements arranged between the first raceway surface and the second raceway surface, In a rolling bearing in which one of the peripheral portions further includes a flank surface that has a radial depth relative to the inner diameter surface or the outer diameter surface included in the one peripheral portion and divides the inner diameter surface or the outer diameter surface over the entire width, and the inner ring or the outer ring has a metal ring that includes the first raceway surface of the inner ring or the second raceway surface of the outer ring, and a resin part that covers the metal ring, the inner diameter surface or the outer diameter surface included in the one peripheral portion, the flank surface, and the first width surface or the second width surface that is continuous with the one peripheral portion are formed by the resin part, configuration 1 is adopted.
[0014] According to the above-described configuration 1, it is possible to provide a clearance fit between the first inner peripheral portion of the inner ring or the second outer peripheral portion of the outer ring, which is one of the peripheral portions including the flank, and the corresponding shaft or housing. This creates a radial gap between the flank and the corresponding shaft or housing. This allows traveling waves generated on the first inner peripheral portion or the second outer peripheral portion to be blocked at the flank, thereby suppressing creep of the inner ring or the outer ring due to the traveling waves. Furthermore, it is possible to provide insulation between the inner ring or the outer ring, which has one peripheral portion, and the corresponding shaft or housing with a resin part, and also to provide insulation between the first width face of the inner ring or the second width face of the outer ring and the abutting portion of the corresponding shaft or the abutting portion of the housing with a resin part. Therefore, it is possible to suppress electrolytic corrosion of the inner and outer rings and the rolling elements even in bearing support structures such as those used in electric axle units. Thus, according to the above-mentioned configuration 1, it is possible to suppress creep of the traveling wave type inner or outer ring while suppressing electrolytic corrosion of the inner and outer rings and rolling elements, and it is possible to provide a rolling bearing that is suitable for an electric axle unit.
[0015] In the above configuration 1, configuration 2 can be adopted in which the resin portion is integrated with the metal ring.
[0016] According to the above configuration 2, the inner ring or the outer ring can be manufactured at reduced cost.
[0017] In the above configuration 2, configuration 3 can be adopted in which the resin portion does not include a weld.
[0018] According to the above configuration 3, since the resin portion does not include a weld that would be a weak portion, it is possible to make the resin portion less likely to crack.
[0019] In the above configuration 2, a configuration 4 can be adopted in which the flank has a gate mark and does not include a weld.
[0020] According to the above configuration 4, cracks on the flank can be made less likely to occur.
[0021] In any one of the above configurations 1 to 4, a configuration 5 can be adopted in which a resin portion covering the inner diameter surface or the outer diameter surface included in the one circumferential portion includes a groove extending in the circumferential direction.
[0022] Generally, rolling bearings in electric axle units are lubricated with oil lubrication methods such as splash lubrication, where oil is supplied to the side of the rolling bearing from outside the bearing, or oil bath lubrication. With configuration 5, the oil supplied to the side of the rolling bearing enters the groove on one of the peripheries that is clearance-fit with the shaft or housing, and spreads between the inner or outer diameter surface included in the one periphery and the corresponding shaft or housing. Therefore, even if the inner or outer ring having one periphery creeps, wear of the inner or outer diameter surface and the corresponding shaft or housing can be prevented.
[0023] In the above configuration 5, configuration 6 can be adopted in which the groove intersects with the flank surface.
[0024] According to the sixth aspect, the oil can be guided by the groove from the radial gap where oil is abundant, and can contribute to lubrication between one circumferential portion and the corresponding shaft or housing.
[0025] In any one of the above configurations 1 to 6, configuration 7 can be adopted in which the radial depth of the flank is 0.1 mm or more and 2.5 mm or less.
[0026] According to the above configuration 7, a radial gap can be secured between the relief surface and the corresponding shaft or housing under the inner diameter and load conditions of a general rolling bearing incorporated in a drive motor or reducer of an electric axle unit.
[0027] In any one of the above configurations 1 to 7, configuration 8 can be adopted in which the resin portion has a thickness of at least 0.8 mm.
[0028] According to the above configuration 8, the resin portion can achieve sufficient insulation performance for use in an electric axle unit.
[0029] In any one of the above configurations 1 to 8, a configuration 9 can be adopted in which the power transmission is disposed between a rotating shaft provided in the electric axle unit and a housing. [Effects of the Invention]
[0030] As described above, by adopting the above configuration 1, the present invention can provide a rolling bearing that is suitable for an electric axle unit, which can suppress creep of the traveling wave type inner or outer ring and suppress electrolytic corrosion of the inner and outer rings and rolling elements at the same time. [Brief explanation of the drawings]
[0031] [Figure 1] FIG. 3 is a partial vertical sectional front view showing the rolling bearing according to the first embodiment of the present invention, taken along the line II in FIG. 2 . [Figure 2] A side view of the rolling bearing of Figure 1 [Figure 3]1 is a side view of an outer ring according to a first embodiment; [Figure 4] Schematic diagram showing the definition of fiber orientation degree [Figure 5] FIG. 2 is a perspective view showing a modified example of the outer ring of FIG. 1; [Figure 6] FIG. 10 is a partial vertical sectional front view showing a rolling bearing according to a second embodiment of the present invention; [Figure 7] A perspective view of the inner ring of FIG. [Figure 8] FIG. 10 is a partial vertical sectional front view showing a rolling bearing according to a third embodiment of the present invention; [Figure 9] A perspective view of the outer ring of Figure 8 [Figure 10] FIG. 10 is a partial vertical sectional front view showing a rolling bearing according to a fourth embodiment of the present invention; [Figure 11] 11 is a perspective view of the inner ring of FIG. DETAILED DESCRIPTION OF THE INVENTION
[0032] A rolling bearing according to a first embodiment, as one example according to the present invention, will be described with reference to the accompanying drawings, FIGS. 1 to 4. FIG.
[0033] 1 and 2 is disposed between a rotating shaft 100 and a housing 110. The inner diameter of the rolling bearing 1 can be in the range of 30 mm to 45 mm, for example.
[0034] Here, the direction along the central axis of the rolling bearing 1 is referred to as the "axial direction." The direction along the circumference around the central axis of the bearing is referred to as the "circumferential direction." The direction perpendicular to the central axis of the bearing is referred to as the "radial direction."
[0035] The housing 110 houses an AC drive motor, a reducer, etc., which are provided in an electric axle unit for an automobile, and is made up of one or more members including a motor case, a gear case, etc. The rotating shaft 100 rotates relative to the housing 110 and is the motor shaft of the AC drive motor or the transmission shaft of the reducer.
[0036] Oil is supplied to the side of the rolling bearing 1.
[0037] The rotating shaft 100 and the housing 110 each have a cylindrical bearing seat 101, 111 extending in the circumferential direction. In Figures 1 and 2, the bearing center axis of the rolling bearing 1 and the center lines of the bearing seats 101, 111 are coaxial.
[0038] The rolling bearing 1 comprises an inner ring 10, an outer ring 20, a plurality of rolling elements 30, and a cage 40 that holds these rolling elements 30. The rolling bearing 1 rotatably supports a rotating shaft 100 relative to a housing 110, and bears a radial load acting between the rotating shaft 100 and the housing 110. Figure 2 illustrates a case in which a unidirectional radial load F is applied to the rolling bearing 1 between bearing seat surfaces 101, 110 while the rolling bearing 1 is in operation.
[0039] The inner ring 10 has a first outer peripheral portion 11 including a first raceway surface 11a, a first inner peripheral portion 12 including an inner diameter surface 12a along the circumferential direction, and first width faces 13, 13 extending radially in a side surface region between the first outer peripheral portion 11 and the first inner peripheral portion 12. The two first width faces 13, 13 are located on both ends of the axial width of the inner ring 10 and each have the shape of a circular surface extending radially. The outer peripheral edges of the first width faces 13, 13 intersect with the first outer peripheral portion 11, and the inner peripheral edges of the first width faces 13, 13 intersect with the first inner peripheral portion 12.
[0040] The inner diameter surface 12a of the inner ring 10 and the bearing seat surface 101 of the rotating shaft 100 are tightly fitted together.
[0041] The outer ring 20 has a second inner peripheral portion 21 including a second raceway surface 21a, a second outer peripheral portion 22 including an outer diameter surface 22a along the circumferential direction, and second width faces 23, 23 extending radially in a side surface region between the second inner peripheral portion 21 and the second outer peripheral portion 22. The two second width faces 23, 23 are located on both ends of the axial width of the outer ring 20 and each have the shape of an annular surface extending radially. The outer peripheral edges of the second width faces 23, 23 intersect with the second outer peripheral portion 22, and the inner peripheral edges of the second width faces 23, 23 intersect with the second inner peripheral portion 21.
[0042] There is a clearance fit between the outer diameter surface 22a of the outer ring 20 and the bearing seat surface 111 of the housing 110. A second width surface 23 on one end side of the outer ring 20 is supported in the axial direction by an abutment portion 112 provided on the housing 110.
[0043] The rolling elements 30 are made of balls.
[0044] The first raceway surface 11a and the second raceway surface 21a are each formed as raceway grooves having an arc-shaped cross section.
[0045] The rolling bearing 1 is configured as a deep groove ball bearing.
[0046] The second outer peripheral portion 22 of the outer ring 20 further includes a flank 22b that divides the outer diameter surface 22a over the entire axial width. The flank 22b has a radial depth δ relative to the outer diameter surface 22a. The radial depth δ corresponds to the radial distance from an imaginary circle VC that is tangent to the outer diameter surface 22a to the flank 22b.
[0047] As shown in FIG. 3, the radial depth δ of the flank 22b is set to be maximum at the center of the circumferential length of the flank 22b relative to the diameter of the outer diameter surface 22a, and to be smaller as the position becomes farther circumferentially from the center.
[0048] The outer ring 20 is supported in the radial direction by the bearing seat 111 of the housing 110 at its outer diameter surface 22a. As shown in FIGS. 1 and 2, the flank 22b generates a radial gap g between the flank 22b and the bearing seat 111 of the housing 110. The radial gap g is a space that passes through in the axial direction between the second outer peripheral portion 22 of the outer ring 20 and the bearing seat 111 of the housing 110. Note that the radial gap g in FIGS. 1 and 2 and the maximum radial depth δ in FIG. 3 are exaggerated in size.
[0049] The load zone of the rolling bearing 1, in which the rolling elements 30 are subjected to a radial load, extends over approximately half the circumference of the rolling bearing 1. The circumferential center of this load zone is the position where the rolling element load is maximum, and corresponds to the load direction of the radial load F (corresponding to the position on the extension of the arrow of the radial load F in FIG. 1). In this load zone, the second outer peripheral portion 22 of the outer ring 20 receives the radial load on the second raceway surface 21a via the rolling elements 30, and is therefore elastically deformed in a wave-like manner. The radial height of this wave-like shape is greatest at the circumferential center of the load zone and decreases the further away from the circumferential center.
[0050] Flank 22b may be formed so as to ensure a non-contact area across the entire width between flank 22b and bearing seat surface 111 of housing 110 in the load zone when a predetermined radial load F is applied to rolling bearing 1. In the case of ball bearings that support the motor shaft of an electric axle unit or the transmission shaft of a reducer, a radial load is generally applied within a range that satisfies (equivalent load applied to ball bearing: P / basic dynamic load rating of ball bearing: C)≦0.4. Therefore, if we assume that P / C of rolling bearing 1 = 0.4 as the predetermined radial load F mentioned above, it is generally possible to ensure the non-contact area mentioned above.
[0051] 3 is set to be greater than the maximum radial height of the corrugated shape described above in the load zone of the rolling bearing 1 when the maximum radial load F is applied. Moreover, the radial depth of the flank 22b gradually decreases from the center of the circumferential length of the flank 22b toward the end e of the outer diameter surface 22a so as not to exceed the reduction in the radial height of the corrugated shape that corresponds to the circumferential position described above.
[0052] In the illustrated example, the flank surface 22b is continuous between both circumferential ends e, e of the arc-shaped outer diameter surface 22a and is formed as a substantially arc-shaped surface along the axial direction. The radius of curvature of the substantially arc-shaped surface is larger than that of the outer diameter surface 22a, and the center line (center of curvature) of the substantially arc-shaped surface is set at a position shifted in one radial direction (downward in FIG. 3) from the center line of the outer diameter surface 22a.
[0053] The circumferential length of the flank 22b can be defined by angle α around the bearing center axis. Here, when the pitch angle between the rolling elements 30 shown in Fig. 1 is θ, the angle α corresponding to the circumferential length of the flank 22b shown in Fig. 3 can be set, for example, to 0<α≦2θ. It is preferable to set 0.5θ≦α≦θ so that the outer ring 20 and the bearing seat 111 of the housing 110 do not come into contact with each other even when the outer ring 20 is deflected by a radial load.
[0054] Although the flank 22b has a substantially arc-shaped shape, the shape of the flank is not limited. For example, the radial depth may be substantially constant over substantially the entire circumferential length of the flank. However, if a step occurs at the circumferential end of the flank, creating a linear corner, the contact pressure at the corner will become excessive. Therefore, it is preferable that the flank and the resin surface adjacent to it in the circumferential direction be smoothly connected by a single or multiple curved surfaces.
[0055] The outer ring 20 is composed of a metal ring 24 including the second raceway surface 21 a and a resin portion 25 covering the metal ring 24 .
[0056] The second outer peripheral portion 22 of the outer ring 20 is made up of the outer peripheral surface of the resin portion 25. The entire outer diameter surface 22a and the entire flank surface 22b included in the second outer peripheral portion 22, as well as the entire second width surfaces 23, are formed by the resin portion 25 at the joints.
[0057] The second inner peripheral portion 21 of the outer ring 20 is constituted by the inner peripheral surface of the metal ring 24 and the inner peripheral surfaces of both axial ends of the resin portion 25 .
[0058] Resin portion 25 covers metal ring 24 by insert molding. Insert molding allows one layer of resin portion 25, including outer diameter surface 22a, flank surface 22b, and second width surface 23, to be molded all at once and simultaneously integrated with metal ring 24. Therefore, compared to forming multiple insulating layers in multiple stages as in Patent Document 2, there are fewer manufacturing steps for the outer ring, and the manufacturing costs of outer ring 20 can be reduced.
[0059] If high dimensional accuracy is required for the surface of the insert-molded resin portion 25, it may be finished to the required dimensions by appropriate post-processing such as grinding.
[0060] Furthermore, portions of the flank 22b that do not come into contact with the bearing seat 111 of the housing 110 and that can ensure a sufficient spatial distance for insulation between them and the bearing seat 111 do not necessarily need to be formed from the resin portion 25, and it is also possible to expose the surface of the metal ring 24 in such portions. Since a spatial distance cannot be ensured near both circumferential ends of the flank 22b, it is sufficient to include at least such regions in the resin portion 25.
[0061] However, in an electric axle unit, metal powder is generated due to deterioration of gears and the like in the reducer, and this metal powder can get into the radial gap g between the bearing seat surface 111 of the housing 110 and the flank surface 22b, and become lodged or caught in this gap. If part of the flank surface is made of the surface of the metal ring, there is a concern that the bearing seat surface and the metal ring may be electrically connected via the metal powder. To eliminate this concern, it is preferable to form the entire flank surface 22b with the resin portion 25, as in the outer ring 20, and more preferably, the entire second outer peripheral portion 22 with the resin portion 25.
[0062] The resin portion 25 is preferably made of, for example, polyphenylene sulfide resin (PPS), polyamide resin (PA6T, PA10T, etc.), syndiotactic polystyrene resin (SPS), liquid crystal polymer (LCP), or the like.
[0063] The radial depth δ of the flank 22b is 0.1 mm or more and 2.5 mm or less. The Young's modulus of resin is lower than that of steel, and so when pressed down, resin deflects more than steel. Compared to a typical steel outer ring, the diameter of the circular outer peripheral surface of the steel metal ring 24 is set smaller, and the outer peripheral surface of the metal ring 24 is covered with the resin portion 25, making the outer ring 20 more susceptible to deflection under a radial load F. For this reason, the radial depth δ of the flank 22b needs to be set deeper than the radial depth of the flank when the entire outer ring 20 is made of steel. In applications where a typical bearing inner diameter (equivalent to the inner diameter of inner diameter surface 12a) is 30 mm or more and 40 mm or less when used to support the motor shaft of an electric axle unit or the transmission shaft of a reducer, and the aforementioned specified radial load F satisfies (P / C)≦0.4, if the radial depth δ is less than 0.1 mm, there is a concern that a non-contact area may not be secured between flank surface 22b and bearing seat surface 111 of housing 110, while if the radial depth δ exceeds 2.5 mm, an excessively large radial gap g will be created.
[0064] The flanks may be formed in multiple locations in the circumferential direction. In this case, when creep of the traveling-wave outer ring occurs, one of the multiple flanks distributed around the circumference will reach the load bearing zone early, thereby reducing the amount of creep of the outer ring. When the second width surface extending around the entire circumferential direction is formed by the resin portion, even when flanks are formed in multiple locations around the circumference, it is possible to integrate the resin portion with the outer ring by insert molding.
[0065] In order to ensure good insulation between the metal ring 24 of the outer ring 20 and the housing 110 by the resin portion 25, the resin portion 25 is provided to have a thickness of at least 0.8 mm.
[0066] The thickness t of the resin portion 25 is sufficient to ensure the creepage distance between the housing 110 and the metal wheel 24. Due to the increasing output of drive motors and other components of electric axle units, the system voltage of electric axle units is expected to increase to approximately 1000 V in the future, in which case the potential difference between the rotating shaft 100 and the housing 110 is expected to be approximately 100 V. Even with this potential difference, as long as the thickness t of the resin portion 25 is 0.3 mm or greater, the creepage distance required for insulation can be provided. Furthermore, even when considering the fluidity of the resin during molding, injection molding is possible if the thickness t of the resin portion 25 is 0.3 mm or greater, preferably 0.4 mm or greater.
[0067] The resin portion 25 does not include a weld. A weld is a relatively weak structure formed at the confluence of resin flows within a mold. Because the difference between the linear expansion coefficient of the resin portion 25 and the linear expansion coefficient of the metal ring 24 is large, circumferential stress based on this difference can occur in the resin portion 25. There is a limit to how much circumferential strength can be ensured by increasing the thickness t of the resin portion 25 in order to meet the demand for compactness. For this reason, it is not desirable for the resin portion 25 to include a weld, which is a locally weak portion.
[0068] When insert molding the resin part 25 by placing a metal ring 24 in the cavity of a mold to transfer the shape of the resin part 25, a disk gate is used as the gate method for injecting resin into the cavity, and by simultaneously injecting the resin from the disk gate in the axial direction around the entire circumference, a resin part 25 that does not contain welds can be realized.
[0069] In order to increase the strength of the resin part 25, it is preferable to use a resin such as the aforementioned PPS as the matrix resin, and to use a fiber-reinforced resin in which non-conductive fibers such as glass fibers and resin fibers are mixed as a filler in the matrix resin as the material for the resin part 25.
[0070] When the fiber reinforced resin is injected from the disk gate as described above, if the average fiber orientation degree (see FIG. 4) of the filler contained in the resin portion 25 is 1.0, the resin portion 25 will not have sufficient strength against the circumferential stress described above, and cracks may occur in the resin portion 25. To avoid this, the average fiber orientation degree is preferably 0.92 or less.
[0071] Here, the fiber orientation degree is a value defined as "1" when the filler contained in the resin portion 25 extends completely in the axial direction, "0.5" when the filler extends at a 45° angle relative to the circumferential direction, and "0" when the filler extends completely in the circumferential direction. A fiber orientation degree of 0.92 or less corresponds to the filler extending at an angle of 82.8° relative to the circumferential direction. The average fiber orientation degree is calculated by setting an arbitrary range on the outer diameter surface 22a of the resin portion 25, calculating the fiber orientation degree for all fillers within that range, and averaging the average. There is a concern that the fiber orientation degree may vary depending on the measurement location. Therefore, the measurement range preferably includes both axial ends of the resin portion, and it is even more preferable to evaluate a portion where the circumferential measurement distance is 1 mm or more.
[0072] The fiber orientation of each filler in the aforementioned range is calculated by fiber orientation extraction using cylinder fitting. That is, the image of the aforementioned range is analyzed to extract each filler as a cylinder, and the angle at which each cylinder is tilted relative to the circumferential direction is determined. The fiber orientation of each filler is calculated from the determined angle. Fiber orientation extraction using cylinder fitting is disclosed in detail in the following document: Toru Suzuki, Toshio Sugita, Masahiro Seto, Hironori Kakishima, Hiroaki Tanaka, and Masaru Yamabe. Molding. Japan Society of Plastics Processing. 2016, 28(6), pp. 239-246
[0073] As described above, the rolling bearing 1 (see Figures 1 to 3) comprises an inner ring 10 having a first outer peripheral portion 11 including a first raceway surface 11a, a first inner peripheral portion 12 including an inner diameter surface 12a along the circumferential direction, and a first width surface 13 extending radially in a side portion between the first outer peripheral portion 11 and the first inner peripheral portion 12, an outer ring 20 having a second inner peripheral portion 21 including a second raceway surface 21a, a second outer peripheral portion 22 including an outer diameter surface 22a along the circumferential direction, and a second width surface 23 extending radially in a side portion between the second inner peripheral portion 21 and the second outer peripheral portion 22, and a plurality of rolling elements 30 arranged between the first raceway surface 11a and the second raceway surface 21a.
[0074] In the rolling bearing 1, the second outer peripheral portion 22, which is one of the first inner peripheral portion 12 and the second outer peripheral portion 22, has a radial depth δ with respect to the outer diameter surface 22a included in the second outer peripheral portion 22 and further includes a flank 22b that divides the outer diameter surface 22a over its entire width, so that when the second outer peripheral portion 22 of the outer ring 20 is clearance-fitted into the bearing seat 111 of the housing 110, a radial gap g can be generated between the flank 22b and the bearing seat 111 of the housing 110. For this reason, the rolling bearing 1 can block, at the flank 22b, traveling waves generated on the second outer peripheral portion 22 by the rolling-element load of the revolving rolling elements 30, and suppress creep of the outer ring 20 due to the traveling waves.
[0075] In addition, the rolling bearing 1 has an outer ring 20 which has a metal ring 24 including a second raceway surface 21a and a resin part 25 which covers the metal ring 24, and the outer diameter surface 22a, the relief surface 22b, and the second width surface 23 which is continuous with the second outer peripheral portion 22 (one peripheral portion) of the outer ring 20 are formed by the resin part 25, so that the resin part 25 insulates between the second outer peripheral portion 22 of the outer ring 20 and the bearing seat surface 111 of the housing 110, and also insulates between the second width surface 23 of the outer ring 20 and the abutting portion 112 of the housing 110, and electrolytic corrosion of the inner and outer rings 10, 20 and the rolling elements 30 can be suppressed even in a bearing support structure such as that used in an electric axle unit.
[0076] In this way, the rolling bearing 1 can suppress creep of the traveling wave type outer ring 20 while suppressing electrolytic corrosion of the inner and outer rings 10, 20 and the rolling elements 30, and can be provided as a rolling bearing suitable for electric axle units.
[0077] Furthermore, in the rolling bearing 1, the resin part 25 is integrated with the metal ring 24 by insert molding, so the outer ring 20 can be produced at low manufacturing costs using a simple manufacturing method in which the metal ring 24 is covered at the same time as the resin part 25 is molded.
[0078] Furthermore, since the rolling bearing 1 does not include a weld in the resin portion 25, cracks in the resin portion 25 due to circumferential stress can be made less likely to occur.
[0079] Furthermore, since the radial depth δ of the relief surface 22b of the rolling bearing 1 is 0.1 mm or more and 2.5 mm or less, a radial gap g can be secured between the relief surface 22b and the bearing seat surface 111 of the housing 110 under the inner diameter and load conditions of a typical rolling bearing incorporated into the drive motor or reducer of an electric axle unit.
[0080] Furthermore, in the rolling bearing 1, the resin portion 25 has a thickness t of at least 0.8 mm, so that the resin portion 25 can achieve sufficient insulation performance for use in an electric axle unit.
[0081] In the rolling bearing 1, an example has been shown in which the resin portion 25 is formed by insert molding using a disk gate, but it is also possible to perform insert molding using a pinpoint gate at one or more points.
[0082] In this case, by setting the position of the pin gate, i.e., the position of the gate mark G on the outer ring 20, on the flank 22b as shown in Figure 5, it is possible to place the weld in a location other than the flank 22b, for example, only in the resin portion that forms the outer diameter surface 22a. When using multiple pin gates, it is sufficient to set one pin gate on the flank 22b and set the other pin gates at positions sufficiently distant from the flank 22b in the circumferential direction.
[0083] In this way, the gate mark G is present on the flank 22b, and the flank 22b does not include a weld, so that cracks on the flank 22b due to circumferential stress can be made less likely to occur.
[0084] A rolling bearing according to the second embodiment is shown in Figures 6 and 7. In the explanation of the second embodiment, only the differences from the first embodiment will be described.
[0085] 6 and 7 has a first outer peripheral portion 51 including a first raceway surface 51a, a first inner peripheral portion 52 including a first inner diameter surface 52a, and first width surfaces 53, 53 at both ends, which are formed from a metal ring 54 and a resin portion 55. The outer ring 60 is made of a metal ring including a second inner peripheral portion 61 including a second raceway surface 61a, and a second outer peripheral portion 62 including a second outer diameter surface 62a.
[0086] The entire surface of the first inner peripheral portion 52 of the inner ring 50 and the entire surfaces of the first width faces 53, 53 are formed by a seamless resin portion 55.
[0087] There is a clearance fit between the inner diameter surface 52a of the inner ring 50 and the bearing seat surface 101 of the rotating shaft 100. A first width surface 53 on one end side of the inner ring 50 is supported in the axial direction by an abutment portion 102 provided on the rotating shaft 100.
[0088] A radial gap g is secured between a flank 52b included in the first inner peripheral portion 52 and the bearing seat surface 101 of the rotating shaft 100. The shape and effects of the flank 52b are in the opposite relationship to those of the first embodiment in the radial direction.
[0089] The outer diameter surface 62a of the outer ring 60 and the bearing seat surface 111 of the housing 110 are tightly fitted together.
[0090] As shown in FIG. 6, a gate mark G corresponding to the position of the pin gate during insert molding is located on the flank 52b, and does not include a weld on the flank 52b.
[0091] The only difference is that the average fiber orientation degree is set to an arbitrary range on the inner diameter surface 52a.
[0092] As described above, in the rolling bearing according to the second embodiment, the first inner peripheral portion 52, which is one of the first inner peripheral portion 52 and the second outer peripheral portion 62, further includes a flank 52b that has a radial depth relative to the inner diameter surface 52a included in the first inner peripheral portion 52 and divides the inner diameter surface 52a over the entire width, so that when the first inner peripheral portion 52 of the inner ring 50 is clearance-fitted into the bearing seat 101 of the rotating shaft 100, a radial gap g can be generated between the flank 52b and the bearing seat 101 of the rotating shaft 100. For this reason, in the rolling bearing according to the second embodiment, traveling waves generated on the first inner peripheral portion 52 by the rolling-element load of the revolving rolling elements 30 are blocked at the flank 52b, and creep of the inner ring 50 due to the traveling waves can be suppressed.
[0093] In addition, in the rolling bearing of the second embodiment, the inner ring 50 has a metal ring 54 including a first raceway surface 51a and a resin part 55 covering the metal ring 54, and the inner diameter surface 52a, the relief surface 52b, and the first width surface 53 continuous with the first inner peripheral portion 52 (one of the peripheral portions) of the inner ring 50 are formed by the resin part 55.Therefore, the resin part 55 insulates between the first inner peripheral portion 52 of the inner ring 50 and the bearing seat surface 101 of the rotating shaft 100, and the resin part 55 also insulates between the first width surface 53 of the inner ring 50 and the abutting portion 102 of the rotating shaft 100, making it possible to suppress electrolytic corrosion of the inner and outer rings 50, 60 and the rolling elements 30 even in a bearing support structure such as that used in electric axle units.
[0094] In this way, the rolling bearing of the second embodiment can suppress creep of the traveling wave type inner ring 50 while suppressing electrolytic corrosion of the inner and outer rings 50, 60 and the rolling element 30, and can be provided as a rolling bearing suitable for electric axle units.
[0095] Furthermore, in the rolling bearing according to the second embodiment, the resin portion 55 is integrated with the metal ring 54 by insert molding, so that the inner ring 50 can be produced at low manufacturing costs using a simple manufacturing method in which the metal ring 54 is covered at the same time as the resin portion 55 is molded.
[0096] Furthermore, in the rolling bearing according to the second embodiment, the flank 52b has gate marks G and does not include a weld, making it difficult for the flank 52b to crack due to circumferential stress.
[0097] Furthermore, in the rolling bearing of the second embodiment, the radial depth of the relief surface 52b is 0.1 mm or more and 2.5 mm or less, so that a radial gap g can be secured between the relief surface 52b and the bearing seat surface 102 of the rotating shaft 100 under the inner diameter and load conditions of a typical rolling bearing incorporated into the drive motor or reducer of an electric axle unit.
[0098] Furthermore, in the rolling bearing according to the second embodiment, the resin portion 55 has a thickness of at least 0.8 mm, so that the resin portion 55 can achieve sufficient insulation performance for use in an electric axle unit.
[0099] 6 and 7 show examples of insert molding using one or more pinpoint gates, but it is also possible to form the resin part 55 by insert molding using a disk gate. In such a rolling bearing, the resin part 55 does not include a weld, making it less likely for the resin part 55 to crack due to circumferential stress.
[0100] A rolling bearing according to the third embodiment is shown in Figures 8 and 9. In the explanation of the third embodiment, only the differences from the first embodiment will be described.
[0101] The rolling bearing according to the third embodiment differs from the first embodiment only in that a groove 22c is added to the resin portion 25.
[0102] Groove 22c extends circumferentially in the axial center of second outer peripheral portion 22. The outer diameter surface 22a of outer ring 20 is formed on both axial sides of groove 22c. Groove 22c is adjacent to outer diameter surface 22a in the axial direction over the entire circumferential length thereof, and intersects with relief surface 22b at open groove ends on both circumferential ends. Therefore, groove 22c communicates circumferentially with radial gap g (see FIG. 2).
[0103] In the rolling bearing according to the third embodiment (see FIGS. 2, 8, and 9), the second outer peripheral portion 22 (one peripheral portion) of the outer ring 20 includes a groove 22c axially adjacent to the outer diameter surface 22a, and the groove 22c is formed by a resin portion 25. Therefore, oil supplied to the side of the rolling bearing enters the groove 22c of the second outer peripheral portion 22, which is clearance-fit with the bearing seat 111 of the housing 110, and spreads between the outer diameter surface 22a and the bearing seat 111 of the housing 110. As a result, an oil film is formed between the bearing seat 111 of the housing 110 and the outer diameter surface 22a of the outer ring 20, and this oil film reduces the coefficient of friction when the outer diameter surface 22a slides circumferentially against the bearing seat 111. Therefore, the rolling bearing according to the third embodiment can prevent wear of the outer diameter surface 22a and the bearing seat 111 of the housing 110, even if the outer ring 20 creeps.
[0104] Furthermore, in the rolling bearing according to the third embodiment, the groove 22c intersects with the relief surface 22b, so that the groove 22c guides oil from the radial gap g, which is rich in oil, and contributes to lubrication between the second outer peripheral portion 22 and the bearing seat surface 111 of the housing 110.
[0105] A rolling bearing according to the fourth embodiment is shown in Figures 10 and 11. In the explanation of the fourth embodiment, only the differences from the second embodiment will be described.
[0106] The rolling bearing according to the fourth embodiment differs from the second embodiment only in that a plurality of grooves 52c are added to the resin portion 55.
[0107] Each groove 52c extends circumferentially in the axially intermediate portion of the first inner peripheral portion 52. An inner diameter surface 52a is formed on both axial sides of each groove 52c. Each groove 52c is adjacent to the inner diameter surface 52a in the axial direction over the entire circumferential length thereof, and intersects with the relief surface 52b at the open groove ends at both circumferential ends. Therefore, each groove 52c communicates circumferentially with a radial gap (see FIG. 6).
[0108] In the rolling bearing according to the fourth embodiment (see FIGS. 6, 10, and 11), the first inner peripheral portion 52 (one peripheral portion) of the inner ring 50 includes a groove 52c axially adjacent to the inner diameter surface 52a, and the groove 52c is formed of a resin portion 55. Therefore, oil supplied to the side of the rolling bearing enters the groove 52c of the first inner peripheral portion 52, which is clearance-fit with the bearing seat 101 of the rotating shaft 100, and spreads between the inner diameter surface 52a and the bearing seat 101 of the rotating shaft 100. As a result, an oil film is formed between the bearing seat 101 of the rotating shaft 100 and the inner diameter surface 52a of the inner ring 50, and this oil film reduces the coefficient of friction when the inner diameter surface 52a slides circumferentially against the bearing seat 101. Therefore, the rolling bearing according to the fourth embodiment can prevent wear of the inner diameter surface 52a and the bearing seat 101 of the rotating shaft 100, even if the inner ring 50 creeps.
[0109] Furthermore, in the rolling bearing according to the fourth embodiment, the groove 52c intersects with the relief surface 52b, so that the groove 52c guides oil from the radial gap g, which is rich in oil, and contributes to lubrication between the first inner peripheral portion 52 and the bearing seat surface 101 of the rotating shaft 100.
[0110] As exemplified in the third and fourth embodiments, the number of grooves formed in the resin portion may be one or more. Furthermore, as exemplified in the third and fourth embodiments, the grooves may be formed with a finite length in the circumferential direction, may extend over the entire circumferential circumference, or may be formed intermittently in the circumferential direction and distributed over the entire circumference. Furthermore, the grooves do not need to extend along the circumferential direction; it is sufficient that there is a circumferential region in which the inner diameter surface of the inner ring or the outer diameter surface of the outer ring and the groove are adjacent in the axial direction. It is preferable for the grooves that intersect the flank face to extend along the circumferential direction, since this makes it easier for the grooves to take in oil from radial gaps during creep of the inner ring or outer ring.
[0111] The rolling bearing according to the present invention can also be used in applications other than electric axle units, and can be used to suppress creep of the inner or outer ring and to suppress electrolytic corrosion of the rolling bearing in a rotating electric machine in which a potential difference occurs between the shaft and the housing and the inner or outer ring is clearance-fitted to the corresponding shaft or housing.
[0112] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]
[0113] 1. Rolling bearings 10, 50 inner circle 11, 51 First outer periphery 11a, 51a First orbital plane 12, 52 First inner circumference 12a, 52a Inner surface 13, 53 First width 20, 60 outer ring 21, 61 Second inner circumference 21a, 61a Second orbital plane 22, 62 Second outer periphery 22a, 62a outer diameter surface 22b, 52b relief face 22c, 52c groove 23 Second width 24, 54 Metal wheels 25, 55 Resin part 30 rolling elements 100 Rotating shaft of electric axle unit 110 Electric axle unit housing G Gate marks δ Radial depth t Thickness of resin part
Claims
1. an inner ring having a first outer peripheral portion including a first raceway surface, a first inner peripheral portion including an inner diameter surface along the circumferential direction, and a first width surface extending radially at a side surface portion between the first outer peripheral portion and the first inner peripheral portion; an outer ring having a second inner peripheral portion including a second raceway surface, a second outer peripheral portion including an outer diameter surface along the circumferential direction, and a second width surface extending radially at a side surface portion between the second inner peripheral portion and the second outer peripheral portion; a plurality of rolling elements disposed between the first raceway surface and the second raceway surface, One of the first inner peripheral portion and the second outer peripheral portion further includes a relief surface that has a radial depth with respect to the inner diameter surface or the outer diameter surface included in the one of the first inner peripheral portion and divides the inner diameter surface or the outer diameter surface over an entire width, In a rolling bearing, the inner ring or the outer ring has a metal ring that includes the first raceway surface of the inner ring or the second raceway surface of the outer ring, and a resin part that covers the metal ring, a rolling bearing, characterized in that the inner diameter surface or the outer diameter surface included in the one peripheral portion, the relief surface, and the first width surface or the second width surface continuing to the one peripheral portion are formed by the resin portion.
2. 2. The rolling bearing according to claim 1, wherein the resin portion is integrated with the metal ring.
3. 3. The rolling bearing according to claim 2, wherein the resin portion does not contain a weld.
4. 3. The rolling bearing according to claim 2, wherein the flank has a gate mark and does not include a weld.
5. The rolling bearing according to claim 1 , wherein a resin portion covering the inner diameter surface or the outer diameter surface included in the one of the circumferential portions includes a groove extending in the circumferential direction.
6. 6. A rolling bearing according to claim 5, wherein the groove intersects the flank.
7. 5. The rolling bearing according to claim 1, wherein the radial depth of the flank is 0.1 mm or more and 2.5 mm or less.
8. 5. The rolling bearing according to claim 1, wherein the resin portion has a thickness of at least 0.8 mm.
9. 5. The rolling bearing according to claim 1, which is disposed between a rotary shaft and a housing of an electric axle unit.