Wheel support rolling bearing unit

Abstract

To provide a rolling bearing unit for supporting a wheel which inhibits flow of grease at the interior of a bearing to inhibit poor lubrication of an inner ring raceway surface and occurrence of grease stirring resistance at both ends of the bearing by improving a shape of a retainer.SOLUTION: A cylindrical part 55, formed by an inner peripheral surface of a small annular part 51 and an inner peripheral surface of a pillar part 53, and a small shoulder part 38 of an inner ring 32, located closer to a bearing center than an inner ring raceway surface 33 are located close to and face each other so as to form a labyrinth. The cylindrical part 55 extends to the bearing end side so as to intersect with a virtual line L1 extending from a border part 33a between the inner ring raceway surface 33 and the small shoulder part 38 in a direction of a contact angle. The pillar part 53 includes two inner diameter side inclined surfaces 57a, 57b so as to form a recessed part 58 at the inner diameter side. On a projection cross section viewed from a circumferential direction, both of intersection angles θ1, θ2 between the two inner diameter side inclined surfaces 57a, 57b and a contact angle line γ, which extends along the direction of the contact angle α passing through a center O of a ball 40, are acute angles.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wheel-supporting rolling bearing unit, and more particularly to a first- or second-generation wheel-supporting rolling bearing unit that uses balls as rolling elements. [Background technology]

[0002] The wheels and braking members of an automobile are rotatably supported relative to a suspension by a wheel-supporting rolling bearing unit (hereinafter also referred to as a "hub unit bearing"). As a wheel-supporting rolling bearing unit, for example, a double-row angular contact ball bearing in which balls are assembled back-to-back with a contact angle, the so-called first-generation hub unit bearing, has been disclosed (see, for example, Patent Document 1).

[0003] As shown in FIG. 9, the first-generation hub unit bearing 100 described in Patent Document 1 has an inner ring 101 and an outer ring 102 arranged opposite each other so as to be rotatable relative to each other, a plurality of balls 103 incorporated so as to roll freely along the annular internal space of the bearing defined between the inner ring 101 and the outer ring 102, a cage 104 that rotatably holds the plurality of balls 103, and a sealing member 105 that seals the internal space of the bearing from the outside of the bearing.

[0004] The retainer 104 used is an inclined retainer having a small ring portion 104a located near the axial center of the double-row angular ball bearing 100 (hereinafter also referred to as the "bearing center"), a large ring portion 104b located near the axial end of the double-row angular ball bearing 100 (hereinafter also referred to as the "bearing end"), and a pillar portion (not shown) that diagonally connects the small ring portion 104a and the large ring portion 104b.

[0005] In addition, the retainer 104 is formed with a plurality of locking claws 104d that protrude toward the inner diameter at predetermined intervals from the inner surface of the small ring portion 104a in the circumferential direction, and the multiple locking claws 104d are engaged with an annular locking groove 101a formed on the outer surface of the inner ring 101, thereby preventing the retainer 104 and the inner ring 101 from being separated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-229736 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, in a back-to-back double-row angular contact ball bearing, the pre-filled grease G tends to collect on both end sides of the bearing (the back sides of the sealing members 105) due to the influence of centrifugal force and the shape.

[0008] In addition, in the inclined cage 104, the column portion has an inclined surface whose diameter increases toward the end of the bearing. Here, the cage 104 revolves as the balls 103 push against the pockets in the circumferential direction. The ball surfaces that were in contact with or close to the inner ring raceway surface 101b roll and push against the pockets. Therefore, near the equator on the side of the revolution direction of the balls 103 (the rolling surface that matches the contact angle with the rotation axis as the center of rotation), the inclined inner diameter surface of the column portion and the ball surface come close to each other. When the surface of the rotating ball 103 enters the inner diameter side of the pocket of the cage 104, grease G adhering to the ball surface is scraped off by the inclined inner diameter surface of the column portion and, due to the influence of centrifugal force, is easily guided along the inclined inner diameter surface of the column portion and toward both ends of the bearing.

[0009] In recent years, in response to demands for reducing CO2 emissions and the environmental impact, the amount of grease packed into hub unit bearings has been on a downward trend in order to lower torque by reducing stirring resistance and to reduce the use of chemical substances. For this reason, there is a need to suppress the above-mentioned grease flow in order to prevent poor lubrication of the inner ring raceway surface and the occurrence of grease stirring resistance on both ends of the bearing.

[0010] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a wheel-support rolling bearing unit that, by improving the shape of the retainer, can suppress the flow of grease inside the bearing, thereby suppressing poor lubrication of the inner ring raceway surface and the occurrence of grease agitation resistance at both ends of the bearing. [Means for solving the problem]

[0011] The above object of the present invention can be achieved by the following configuration. [1] A wheel-supporting rolling bearing unit comprising: an outer ring having a double-row outer ring raceway surface on its inner peripheral surface; a pair of inner rings each having a double-row inner ring raceway surface on its outer peripheral surface; a plurality of balls provided rollably with contact angles between the outer ring raceway surfaces and the inner ring raceway surfaces; and a pair of cages rotatably holding the plurality of balls, The cage includes a small annular portion located near the center of the bearing, and a plurality of pillar portions extending from the small annular portion at an angle in the axial direction and provided at predetermined intervals in the circumferential direction, a cylindrical portion formed by the inner peripheral surface of the small annular portion and the inner peripheral surface of the column portion and a small shoulder portion of the inner ring closer to the center of the bearing with respect to the inner ring raceway surface are closely opposed to each other so as to form a labyrinth; the cylindrical portion extends toward a bearing end portion so as to intersect with an imaginary line extending from a boundary between the inner ring raceway surface and the small shoulder portion in the direction of the contact angle, The pillar portion has two inclined inner diameter surfaces that form a recess on the inner diameter side, In a projected cross section obtained by superimposing an axial cross section passing through the center of the ball and an axial cross section of the circumferentially intermediate portion of the column portion, the intersection angles between the two inner diameter side inclined surfaces and a contact angle line passing through the center of the ball and extending along the contact angle direction are all acute angles. Rolling bearing unit for wheel support. [Effects of the Invention]

[0012] According to the wheel support rolling bearing unit of the present invention, by configuring the retainer as described above, the flow of grease inside the bearing can be suppressed, thereby preventing poor lubrication of the inner ring raceway surface and the occurrence of grease agitation resistance on both ends of the bearing. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of a wheel support structure according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a cross-sectional view showing the first-generation rolling bearing unit for a wheel support structure of FIG. 1. [Figure 3] 3 is an enlarged cross-sectional view of part III in FIG. 2 taken at the circumferential middle of the column portion. [Figure 4] FIG. 10 is a cross-sectional view of the cage showing the inner surface of the pocket. [Figure 5] 1A is a partial side view of the cage as seen from the center of the bearing, and FIG. 1B is a partial side view of the cage as seen from the end of the bearing. [Figure 6] 10A and 10B are diagrams for explaining the state of grease on the balls and the inner ring raceway surface as the balls pass through the inner ring raceway surface; [Figure 7] FIG. 10 is a cross-sectional view showing a modified example of the cage of the double-row angular contact ball bearing. [Figure 8] FIG. 6 is a partial cross-sectional view of a wheel supporting rolling bearing unit according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view showing a conventional wheel-supporting rolling bearing unit. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) A wheel support structure 10 according to a first embodiment of the present invention will be described below with reference to Figures 1 to 6. In this specification, the outer side in the axial direction refers to the side that is on the outer side in the width direction of the vehicle body when assembled to the suspension, and corresponds to the left side in Figure 1. On the other hand, the inner side in the axial direction refers to the side that is on the center side in the width direction of the vehicle body, and corresponds to the right side in Figure 1.

[0015] As shown in FIG. 1, the wheel support structure 10 of the first embodiment is for a drive wheel, and includes an outer ring 20, a hub 30, a plurality of balls 40, 40, and a pair of seal portions .

[0016] The outer ring 20 has a cylindrical outer peripheral surface and double-row (two-row) outer ring raceway surfaces 22 with an arc-shaped cross section on its inner peripheral surface. When in use, the outer ring 20 is fitted and fixed into a support hole 3 formed in a knuckle 2 that constitutes the suspension system, and when in use, it does not rotate while supported by the knuckle 2. An inward-facing flange-shaped locking collar 4 is formed at the inner end opening of the support hole 3, and the axial inner end face of the outer ring 20 abuts against the locking collar 4. In this state, the axial outer end face of the outer ring 20 is pressed down by a retaining ring 5 engaged with a locking groove formed in the inner peripheral surface of the outer end of the support hole 3, preventing the outer ring 20 from slipping out of the support hole 3.

[0017] The hub 30 is configured by joining a hub ring 31 and a pair of inner rings 32 together, and is disposed coaxially (concentrically) with the outer ring 20 on the inner diameter side of the outer ring 20 .

[0018] The hub wheel 31 is provided with a circular rotating side flange 34 that extends radially outward from a portion that protrudes axially outward from the axially outer (outboard side) opening of the outer ring 20, and is used to support and fix rotating braking members such as a wheel and a disc rotor. In the multiple insertion holes 34a provided in the rotating side flange 34, if each insertion hole 34a has an internal thread, a hub bolt (not shown) is threadedly engaged, and if each insertion hole 34a is a cylindrical hole, a stud bolt 41 is serrated and fitted into the insertion holes 34a.

[0019] A cylindrical small diameter step 35 is formed on the outer peripheral surface of the hub ring 31 from near the rotating side flange 34 to the axially inner side (inboard side). The pair of inner rings 32 are press-fit onto the outer peripheral surfaces of the small diameter step 35 with their small flanges abutting each other, and are positioned and fixed to the hub ring 31 by pressing down on the axially inner end face of the inner ring 32 on the axially inner side with a crimped portion 37 formed on the axially inner end of the hub ring 31. A spline hole 36 is formed in the center of the hub ring 31.

[0020] As a result, an inner ring raceway surface 33 having an arc-shaped cross section formed on the outer peripheral surface of the inner ring 32 of the axially outer row is provided at a portion facing the outer ring raceway surface 22 of the axially outer row provided on the inner peripheral surface of the outer ring 20. Furthermore, an inner ring raceway surface 33 having an arc-shaped cross section formed on the outer peripheral surface of the inner ring 32 of the axially inner row is provided at a portion facing the outer ring raceway surface 22 of the axially inner row provided on the inner peripheral surface of the outer ring 20.

[0021] 2, multiple balls 40 are provided in the axially outer row between the outer ring raceway surface 22 and the inner ring raceway surface 33, and multiple balls 40 are provided in the axially inner row between the outer ring raceway surface 22 and the inner ring raceway surface 33, and are held by a cage 50 so that they can roll freely. In this state, the balls 40 arranged in double rows are assembled back-to-back at a contact angle α (the angle between the contact angle line γ, which is a straight line passing through the center O of the ball 40 and connects the center position Co of the contact area between the outer ring raceway surface 22 and the ball 40 and the center position Ci of the contact area between the inner ring raceway surface 33 and the ball 40, and the radial line passing through the center O of the ball 40).

[0022] Furthermore, a pair of seals 42, 42 such as a seal ring or a combination seal ring consisting of a seal ring and a slinger are arranged between the inner peripheral surfaces at both ends of the outer ring 20 and the outer peripheral surface at the outer end of the inner ring 32 and the outer peripheral surface at the inner end of the inner ring 32, and close both axial end openings (axially outer and axially inner) of the internal space 45 in which the multiple balls 40 are provided. This prevents lubricant such as grease sealed in the internal space 45 from leaking to the outside, and prevents foreign matter such as muddy water from entering the internal space 45 from the outside.

[0023] That is, the wheel support structure 10 of this embodiment is configured such that the knuckle 2 is fitted onto the outer peripheral surface of the outer ring 20 of a first-generation hub unit bearing (back-to-back double-row angular ball bearing) 11, and a hub ring 31 having a rotating side flange 34 is fitted into the inner peripheral surface of a pair of inner rings 32.

[0024] 4, the cage 50 is an inclined cage and includes a small ring portion 51 near the center of the bearing, a large ring portion 52 near the end of the bearing, and a plurality of pillar portions 53 that connect the small ring portion 51 and the large ring portion 52 at an angle and are provided at predetermined intervals in the circumferential direction. The small ring portion 51, the large ring portion 52, and the adjacent pillar portions 53 form pockets 54 that hold the balls.

[0025] 3, a small shoulder portion 38 is formed on the inner ring 32 near the center of the bearing relative to the inner ring raceway surface 33. The small shoulder portion 38 is continuous with the inner ring raceway surface 33 and has a diameter approximately 0.05 mm (radius value) larger than the groove bottom of the inner ring raceway surface 33. The inner circumferential surface of the column portion 53 forms a partial cylindrical surface of the same diameter as the cylindrical surface of the small ring portion 51, which extends continuously from the inner circumferential surface of the small ring portion 51 toward the bearing end. The cage 50 has a cylindrical portion 55 formed by the inner circumferential surface (cylindrical surface) of the small ring portion 51 and the inner circumferential surface (partial cylindrical surface) of the column portion 53, which closely opposes the small shoulder portion 38 of the inner ring 32 so as to form a labyrinth.

[0026] 3 and 5, the inner peripheral surface of the small ring portion 51 is formed with a plurality of locking pawls 56 that protrude inward at predetermined circumferential intervals. These locking pawls are engaged with an annular locking groove 39 formed in the outer peripheral surface of the inner ring 32, preventing separation of the cage 50 and the inner ring 32. The locking pawls 56 and the annular locking groove 39 are closely opposed to each other so as to form a labyrinth together with the gap between the cylindrical portion 55 and the small shoulder portion 38 of the inner ring 32. As shown in FIG. 5, the locking pawls 56 are provided in the same phase as the pillar portions 53, and the circumferential width W1 of the locking pawls 56 is wider than the circumferential width W2 of the pillar portions 53.

[0027] 3, the cylindrical portion 55 extends toward the bearing end so as to intersect with an imaginary line L1 extending in the direction of the contact angle α from the boundary 33a between the inner ring raceway surface 33 and the small shoulder portion 38. That is, in the axial cross section shown in FIG. 3 that passes through the circumferential middle portion of the column portion 53, the terminal position 55a of the cylindrical portion 55 toward the bearing end is located closer to the bearing end than the intersection X1 where the imaginary line L1 intersects with the cylindrical portion 55. This allows a long labyrinth to be formed in the axial direction between the small shoulder portion 38 of the inner ring 30 and the cylindrical portion 55 of the cage 50, making it possible to prevent grease sealed toward the center of the bearing from migrating toward the bearing end.

[0028] It is more preferable that the cylindrical portion 55 extends toward the bearing end so as to intersect with an imaginary line L2 extending radially from the boundary 33a between the inner ring raceway surface 33 and the small shoulder portion 38. In this case, the terminal position 55a of the cylindrical portion 55 on the bearing end side is located closer to the bearing end than the intersection X2 where the imaginary line L2 extending radially from the boundary 33a between the inner ring raceway surface 33 and the small shoulder portion 38 intersects with the cylindrical portion 55.

[0029] 2 and 4, in this embodiment, the inner peripheral surface of base portion 53 has two inner diameter side inclined surfaces 57a, 57b, which form recess 58 and overlap with inner ring raceway surface 33 in the radial direction. In addition, in a projected cross section obtained by superimposing an axial cross section passing through center O of ball 40 and an axial cross section of a circumferentially intermediate portion of base portion 53, intersection angles θ1, θ2 between two inner diameter side inclined surfaces 57a, 57b and contact angle line γ are both acute angles. Note that each inclined surface 57a, 57b is linear in cross section and forms a concave arc surface.

[0030] By forming recess 58 on the inner diameter side of column portion 53 in this way, the inner diameter side inclined surfaces 57a, 57b of column portion 53 scrape off the portion of the grease adhering to ball 40 that is thicker than the gap between pocket 54 and ball 40, and the scraped off grease G is guided by the two inner diameter side inclined surfaces 57a, 57b and collected in the center of recess 58, making it less likely for grease G to flow toward the end of the bearing. In addition, the supply of grease G to the point where ball 40 presses pocket 54 is also promoted, reducing friction between ball 40 and pocket 54.

[0031] Specifically, on the inner ring raceway surface 33, which has a radius of curvature approximately 2% larger than that of the balls 40, grease G is applied to the balls 40 in a cycle as adjacent balls 40 pass by, as shown in Figure 6. That is, as a ball 40 passes the inner ring raceway surface 33, the grease G that is pushed outward from the inner ring raceway surface 33 moves to both axial sides of the inner ring raceway surface 33 before the next ball 40 arrives, so that the next ball 40 has more grease G attached to it at parts B near the poles than at part A near the rotation equator.

[0032] The area near the equator of ball 40 becomes the point at which it presses against pocket 54 (which has a radius of curvature slightly larger than ball 40), and ball 40 and pocket 54 have a structure in which the convex spherical surface and concave spherical surface come into contact at one point. At the entrance to pocket 54, there is a gap between ball 40 and pocket 54, and the recess 58 described above makes it easier for grease G to enter this gap, resulting in a thick oil film at the point at which ball 40 presses pocket 54, thereby reducing friction between ball 40 and pocket 54.

[0033] Furthermore, in the above projected cross section, the top 58a of the recess 58 formed by the two inclined surfaces 57a, 57b is formed near the contact angle line γ. This allows the recess 58 to be formed large, allowing more grease to remain in the recess 58 and supplying grease G onto the equator of the ball 40 while suppressing the movement of grease G toward the end of the bearing.

[0034] As shown in FIG. 4, the cage 50 is manufactured by injection molding using an axial draw, and at the boundary between the radially outer and inner parts of the inner surface of the pocket 54, there is a parting line 70 that was located at the butt joint between a fixed mold and a movable mold (not shown).

[0035] The radially inner portion of the inner surface of pocket 54 is made up of an inner guide surface 71 on the other axial side which is a concave curved surface with a radius of curvature slightly larger than that of balls 40, and an inner retraction surface 72 on one axial side which is a cylindrical concave surface centered on a central axis parallel to the central axis of cage 50. The radially outer portion of the inner surface of pocket 54 is made up of an outer guide surface 75 on one axial side which is a concave curved surface with a radius of curvature slightly larger than that of balls 40, and an outer retraction surface 76 on the other axial side which is a cylindrical concave surface centered on a central axis parallel to the central axis of cage 50.

[0036] A boundary line 73 between the inner guide surface 71 and the inner retraction surface 72 is located on the other axial side of the contact angle line γ (see Figure 1), and a boundary line 77 between the outer guide surface 75 and the outer retraction surface 76 is located on one axial side of the contact angle line γ, and both boundary lines 73, 77 are arc curves that exist in an imaginary plane perpendicular to the central axis of the retainer 50.

[0037] Here, in the above projected cross section, the apex 58a of the recess 58 being located in the vicinity of the contact angle line γ means that the apex 58a is located within the range of lines γ1 and γ2 parallel to the contact angle line γ that pass through the intersections Q1 and Q2 between the parting line 70 and the boundary line 73 and boundary line 77.

[0038] As described above, according to wheel support rolling bearing unit 11 of this embodiment, two inner diameter side inclined surfaces 57a, 57b that form recess 58 are formed on the inner diameter side of pillar portion 53, so that grease G adhering to balls 40 that is scraped off by inner diameter side inclined surfaces 57a, 57b of pillar portion 53 is guided to the two inner diameter side inclined surfaces 57a, 57b and can remain in recess 58, thereby suppressing the movement of grease G toward the bearing end side. In addition, the supply of grease G onto the equator of ball 40 is promoted, reducing friction between ball 40 and pocket 54. This prevents grease adhering to the balls 40 on the inner ring raceway surface from being scraped off by the inclined inner diameter surface of the column portion 53 of the retainer 50, and from being guided along the inner diameter side of the column portion 53 to both ends of the bearing due to the influence of centrifugal force, or from moving into the inter-row space due to the pumping action caused by the passing of the balls 40.As a result, poor lubrication of the inner ring raceway surface 33 and the occurrence of grease agitation resistance on both ends of the bearing can be suppressed.

[0039] In the above embodiment, the apex 58a of the recess 58 is formed near the contact angle line γ when viewed from the circumferential direction. However, as shown in FIG. 7, the apex 58a of the recess 58 may be located away from the vicinity of the contact angle line γ, for example, between the contact angle line γ and the terminal position 55a on the bearing end side of the cylindrical portion 55.

[0040] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 8. The wheel supporting rolling bearing unit 11 of this embodiment has a hub fitted onto the outer diameter of the outer ring, and is configured to be used with the outer ring rotating, and the shape of the cage 50 is different from that of the first embodiment.

[0041] 8, in this embodiment, a small shoulder portion 23 is formed on the outer ring raceway surface 22 of the outer ring 20 near the bearing end, which is continuous with the outer ring raceway surface 22 and has a smaller diameter than the groove bottom of the outer ring raceway surface 22. For convenience of assembly (the assembly of balls 40 and cage 50 needs to be locked within the outer ring raceway surface 22), the small shoulder portion 23 of the outer ring 20 has a larger cross-sectional height than the small shoulder portion 38 side of the inner ring 30.

[0042] In the inclined cage 50, another cylindrical portion 59 formed by the outer circumferential surface of the large ring portion 52 and the outer circumferential surface of the column portion 53 faces closely to form a labyrinth with the small shoulder portion 23 of the outer ring 20. This labyrinth structure makes it possible to confine the enclosed grease within the outer ring raceway surface 22, suppressing poor lubrication of the outer ring raceway surface 22 and further suppressing the occurrence of grease agitation resistance on both ends of the bearing.

[0043] Furthermore, the terminal position 59a of the other cylindrical portion 59 described above, which is closer to the center of the bearing, is formed so that an imaginary line L3 extending in the direction of the contact angle α from the boundary 22a between the outer ring raceway surface 22 and the small shoulder portion 23 intersects with the other cylindrical portion 59. This allows a labyrinth that is long in the axial direction to be formed between the small shoulder portion 23 of the outer ring 20 and the other cylindrical portion 59 of the cage 50, making it possible to confine the sealed grease within the outer ring raceway surface 22. Although not shown, in this embodiment as well, it is more preferable that the terminal position 59a of the other cylindrical portion 59 near the bearing end be formed so that an imaginary line extending radially from the boundary portion 22a between the outer ring raceway surface 22 and the small shoulder portion 23 intersects with the other cylindrical portion 59.

[0044] Furthermore, in this embodiment, the outer peripheral surface of the base portion 53 has two outer diameter side inclined surfaces 60a, 60b, which constitute another recess 61 and overlap the outer ring raceway surface 22 in the radial direction. Furthermore, in the above-mentioned projected cross section, the intersection angles θ3, θ4 between the two inclined surfaces 60a, 60b and the contact angle line γ are both acute angles. The recess 61 overlaps the outer ring raceway surface 22 in the radial direction. In this case, the two outer diameter side inclined surfaces 60a, 60b that constitute the other recess 61 are also formed on the outer diameter side of the base portion 53. Therefore, grease G scraped off by the outer diameter side inclined surfaces 60a, 60b of the base portion 53 from the grease adhering to the balls 40 is guided to the two outer diameter side inclined surfaces 60a, 60b and collected in the center of the other recess 61, making it less likely for the grease G to flow toward the bearing end. Furthermore, the supply of grease G onto the equator of the ball 40 is promoted, thereby reducing friction between the ball 40 and the pocket 54. Each of the inclined surfaces 60a and 60b has a linear cross section and is formed by a convex arc surface.

[0045] In addition, in the above projected cross section, it is preferable that the top 61a of the recess 61 formed by the two outer diameter side inclined surfaces 60a, 60b is formed in the vicinity of the contact angle line γ when viewed from the circumferential direction.

[0046] The recess 61 on the outer ring side and the labyrinth structure can be provided only on the outer diameter side inclined surface of the pillar portion 53 of the retainer 50, but when the hub unit bearing 11 is used with the outer ring rotating, the tendency of grease to flow to both ends of the bearing is greater than when the inner ring is rotating, so it is preferable to provide the recesses 58, 61 on both the outer diameter side inclined surface and inner diameter side inclined surface of the pillar portion 53 of the retainer 50.

[0047] The present invention is not limited to the above-described embodiments, and modifications and improvements are possible as appropriate. For example, in the above embodiment, a first-generation wheel-supporting rolling bearing unit in which a knuckle or hub is fitted onto the outer peripheral surface of the outer ring has been described, but the present invention is also applicable to, for example, a second-generation wheel-supporting rolling bearing unit in which a hub flange or a flange for fastening to a knuckle is formed on the outer peripheral surface of the outer ring.

[0048] In addition, in the above embodiment, an inclined cage in which multiple pillars are connected by small ring portions and large ring portions has been described, but the present invention may also be a crown-type cage in which pillars protrude obliquely from the small ring portions.

[0049] As described above, the present specification discloses the following: (1) A wheel-supporting rolling bearing unit comprising: an outer ring having a double-row outer ring raceway surface on its inner peripheral surface; a pair of inner rings each having a double-row inner ring raceway surface on its outer peripheral surface; a plurality of balls provided rollably with contact angles between the outer ring raceway surfaces and the inner ring raceway surfaces; and a pair of cages rotatably holding the plurality of balls, The cage includes a small annular portion located near the center of the bearing, and a plurality of pillar portions extending from the small annular portion at an angle in the axial direction and provided at predetermined intervals in the circumferential direction, a cylindrical portion formed by the inner peripheral surface of the small annular portion and the inner peripheral surface of the column portion and a small shoulder portion of the inner ring closer to the center of the bearing with respect to the inner ring raceway surface are closely opposed to each other so as to form a labyrinth; the cylindrical portion extends toward a bearing end portion so as to intersect with an imaginary line extending from a boundary between the inner ring raceway surface and the small shoulder portion in the direction of the contact angle, The pillar portion has two inclined inner diameter surfaces that form a recess on the inner diameter side, In a projected cross section obtained by superimposing an axial cross section passing through the center of the ball and an axial cross section of the circumferentially intermediate portion of the column portion, the intersection angles between the two inner diameter side inclined surfaces and a contact angle line passing through the center of the ball and extending along the contact angle direction are all acute angles. Rolling bearing unit for wheel support. This configuration allows the labyrinth to be formed long, suppressing the flow of grease inside the bearing and preventing poor lubrication of the inner ring raceway and grease stirring resistance at both ends of the bearing. Furthermore, grease adhering to the balls is scraped off by the inclined inner diameter surfaces of the column section, and is guided to the two inclined inner diameter surfaces, where it can be retained in the recesses, preventing the grease from moving toward the ends of the bearing. Furthermore, promoting the supply of grease to the equator of the balls reduces friction between the balls and the pockets.

[0050] (2) A plurality of locking claws are formed on the inner peripheral surface of the small ring portion at predetermined intervals in the circumferential direction and protrude toward the inner diameter side, the plurality of locking claws and an annular locking groove formed on the outer peripheral surface of the inner ring and into which the plurality of locking claws can be engaged are closely opposed to each other so as to form the labyrinth together with a gap between the cylindrical portion and a small shoulder portion of the inner ring; A wheel supporting rolling bearing unit according to (1). According to this configuration, a labyrinth can also be formed between the multiple locking pawls and the locking grooves, making it possible to further suppress the flow of grease inside the bearing.

[0051] (3) The cylindrical portion extends toward the bearing end portion so as to intersect with an imaginary line extending radially from a boundary between the inner ring raceway surface and the small shoulder portion. A wheel supporting rolling bearing unit according to (1) or (2). With this configuration, the labyrinth can be formed longer, and the flow of grease inside the bearing can be further suppressed.

[0052] (4) In the projected cross section, the top of the recess is formed in the vicinity of the contact angle line. A wheel-supporting rolling bearing unit according to any one of (1) to (3). With this configuration, the recess can be made larger, allowing more grease to remain in the recess, supplying grease to the equator of the ball while suppressing the grease from moving toward the end of the bearing.

[0053] (5) The cage further includes a large ring portion near the bearing end portion and connected to the plurality of pillar portions, another cylindrical portion formed by the outer peripheral surface of the large ring portion and the outer peripheral surface of the column portion and a small shoulder portion of the outer ring closer to a bearing end portion with respect to the outer ring raceway surface are closely opposed to each other so as to form a labyrinth, the other cylindrical portion extends toward the center of the bearing so as to intersect with an imaginary line extending in the direction of the contact angle from a boundary between the outer ring raceway surface and the small shoulder portion of the outer ring, The pillar portion has two outer diameter side inclined surfaces that form another recess, In the projected cross section, the intersection angles between the two outer diameter side inclined surfaces and the contact angle line are all acute angles. A wheel-supporting rolling bearing unit according to any one of (1) to (4). With this configuration, the sealed grease can be confined within the outer ring raceway surface, which prevents poor lubrication of the outer ring raceway surface and further prevents grease stirring resistance from occurring at both ends of the bearing. [Explanation of symbols]

[0054] 10 Wheel support structure 20 outer ring 22 Outer ring raceway 23,38 Small shoulder 39 Locking groove 30 Hub 32 Inner circle 33 Inner ring raceway surface 40 balls 50 retainer 51 Ringlet 52 Greater ring 53 Pillar section 56 Locking claw 57a,57b Inner diameter side inclined surface 55,59 Cylindrical part 58,61 Recess 60a,60b Outer diameter side inclined surface

Claims

1. A wheel-supporting rolling bearing unit comprising: an outer ring having double-row outer ring raceway surfaces on its inner peripheral surface; a pair of inner rings each having a single row of inner ring raceway surfaces on its outer peripheral surface; a plurality of balls provided so as to be rollable with contact angles formed between the outer ring raceway surfaces and the inner ring raceway surfaces; and a pair of cages rotatably holding the plurality of balls, The cage includes a small annular portion located near the center of the bearing, and a plurality of pillar portions extending from the small annular portion at an angle in the axial direction and provided at predetermined intervals in the circumferential direction, a cylindrical portion formed by the inner peripheral surface of the small annular portion and the inner peripheral surface of the column portion and a small shoulder portion of the inner ring closer to the center of the bearing with respect to the inner ring raceway surface are closely opposed to each other so as to form a labyrinth; the cylindrical portion intersects with an imaginary line extending in the direction of the contact angle from a boundary between the inner ring raceway surface and the small shoulder portion, the pillar portion has two inclined inner diameter surfaces that form a recess on the inner diameter side, In a projected cross section obtained by superimposing an axial cross section passing through the center of the ball and an axial cross section of a circumferentially intermediate portion of the column portion, the intersection angles between the two inner diameter side inclined surfaces and a contact angle line passing through the center of the ball and extending along the contact angle direction are all acute angles. Rolling bearing unit for wheel support.

2. A plurality of locking claws are formed on the inner peripheral surface of the small ring portion at predetermined intervals in the circumferential direction and protrude inward, the plurality of locking claws and an annular locking groove formed on the outer peripheral surface of the inner ring and into which the plurality of locking claws can be locked are closely opposed to each other so as to form a labyrinth together with a gap between the cylindrical portion and a small shoulder portion of the inner ring; 2. A wheel supporting rolling bearing unit according to claim 1.

3. the cylindrical portion intersects with an imaginary line extending in a radial direction from a boundary between the inner ring raceway surface and the small shoulder portion; 3. A wheel supporting rolling bearing unit according to claim 1 or 2.

4. In the projected cross section, the top of the recess is formed in the vicinity of the contact angle line. The wheel supporting rolling bearing unit according to any one of claims 1 to 3.

5. the retainer further includes a large ring portion near the bearing end portion, the large ring portion being connected to the plurality of posts; another cylindrical portion formed by the outer peripheral surface of the large ring portion and the outer peripheral surface of the column portion and a small shoulder portion of the outer ring closer to a bearing end portion with respect to the outer ring raceway surface are closely opposed to each other so as to form a labyrinth, the other cylindrical portion intersects with an imaginary line extending in the direction of the contact angle from a boundary between the outer ring raceway surface and the small shoulder portion of the outer ring, The pillar portion has two outer diameter side inclined surfaces that form another recess, In the projected cross section, the intersection angles between the two outer diameter side inclined surfaces and the contact angle line are both acute angles. The wheel supporting rolling bearing unit according to any one of claims 1 to 4.

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