Wheel bearing device

Abstract

To provide a wheel bearing device which can improve the filling performance of resin at the injection molding of a cage, and can suppress an increase of bearing torque.SOLUTION: A wheel bearing device 1 has a circular disc part 7a formed into an annular shape, and a plurality of column parts 7b extending in an axial direction at constant intervals in a circumferential direction from the circular disc part 7a. A pocket Pt having a curved face 7e along an external peripheral face of a rolling body (ball 8) is formed of the adjacent column parts 7b and the circular disc part 7a, a resin-made cage 7 for holding the rolling body (8) at the pocket Pt is arranged, and the column parts 7b are formed while being branched to an inside diameter side and an outside diameter side by a notched part 7k. An axial length a of the column part 7c at the inside diameter side is set shorter than an axial length b up to a center position P1 of the rolling body (8) with an end part 7p of the circular disc part 7a at a side opposite to the column part 7b in an axial direction as a start point, and set longer than an axial length c up to an end part position P2 of the notched part 7k at the circular disc part 7a side.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, a wheel bearing device that rotatably supports a wheel in a suspension system of an automobile or the like is known. In the wheel bearing device, an inner member including a hub ring is rotatably supported on an outer member via a plurality of rolling elements (here, balls). The plurality of balls are evenly distributed in the circumferential direction by a cage, and are held in a state in which adjacent balls are prevented from contacting each other.

[0003] In such wheel bearing devices, there are known devices that make it possible to increase the bearing life while eliminating the problem of insufficient strength of the cage by reducing the circumferential thickness of the column parts of the cage that separate adjacent balls and by forming cutout parts in the column parts to increase the number of balls, as described in Patent Documents 1 and 2, for example.

[0004] In the cages described in Patent Documents 1 and 2, the circumferential thickness of the bar portions of the cage is reduced, and notches are formed in the portions where adjacent balls are closest to each other. In other words, there are no bar portions between adjacent balls at their closest points. This shortens the circumferential distance between the balls, and increases the number of balls that can be installed in the cage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 0592839 [Patent Document 2] JP 2005-180630 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the cages described in the above Patent Documents 1 and 2, the bar portion is bifurcated into two branches, one on the inner diameter side and the other on the outer diameter side, by a notch portion. In Patent Document 1, as shown in FIG. 7(A), the axial length a1 of the bar portion on the inner diameter side, starting from the end of the annular portion on the axial opposite side of the bar portion, is approximately the same as the axial length b1 to the center position of the ball. In Patent Document 2, as shown in FIG. 7(B), the axial length a2 of the bar portion on the inner diameter side, starting from the end of the annular portion on the axial opposite side of the bar portion, is longer than the axial length b2 to the center position of the ball. With such a shape of the bar portion on the inner diameter side, there is a concern that the resin may not reach the tip of the bar portion during injection molding of the cage, resulting in insufficient filling of the resin, and the quality of the cage may not be stable.

[0007] Furthermore, with the trend toward lower fuel consumption in recent years, wheel bearing devices are also required to have lower torque. In the cage, shear resistance of the grease occurs between the cage and the balls when the wheel bearing device rotates, which leads to an increase in bearing torque, so improvements are required.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a wheel bearing device which improves the filling properties of resin during injection molding of a cage and which can suppress an increase in bearing torque. [Means for solving the problem]

[0009] That is, the first invention is a wheel bearing device comprising: an outer member having a double-row outer raceway surface formed on its inner circumference; an inner member having a double-row inner raceway surface formed opposite the double-row outer raceway surface; double-row rolling elements interposed between the raceway surfaces of the outer member and the inner member so as to be able to roll freely; and a resin cage having an annular portion formed in an annular shape and a plurality of pillar portions extending axially at regular intervals from the annular portion, wherein adjacent pillar portions and the annular portion form pockets having curved surfaces that follow the outer peripheral surfaces of the rolling elements, and the rolling elements are held in the pockets, wherein the pillar portions are branched into an inner diameter side and an outer diameter side by cutout portions, and wherein, starting from an end of the annular portion axially opposite to the pillar portions, the axial length of the pillar portion on the inner diameter side is shorter than the axial length to a center position of the rolling elements and longer than the axial length to an end position of the end portion of the cutout on the annular portion side. Effect of the Invention

[0010] The present invention has the following advantages.

[0011] That is, according to the first aspect of the present invention, the fillability of the resin into the column portion is improved and the shear resistance of the grease between the ball and the column portion is reduced, thereby improving the fillability of the resin during injection molding of the cage and suppressing an increase in bearing torque. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing an overall configuration of a wheel bearing device; [Diagram 2] FIG. 4 is an enlarged cross-sectional view showing the configuration of the ball and the cage. [Diagram 3] FIG. [Figure 4] FIG. 3 is a cross-sectional view showing the overall configuration of the cage. [Diagram 5] FIG. 4 is an enlarged cross-sectional view showing the axial length of a column portion on the inner diameter side. [Figure 6] FIG. 4 is an enlarged perspective view showing the positions of the gate and the weld. [Figure 7]FIG. 11 is an enlarged cross-sectional view showing the axial length of a column portion on an inner diameter side in a conventional cage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a wheel support bearing device 1, which is one embodiment of the wheel support bearing device according to the present invention, will be described with reference to Figs. 1 and 2.

[0014] As shown in FIG. 1, the wheel bearing device 1 supports a wheel rotatably in a suspension device of a vehicle such as an automobile. The wheel bearing device 1 includes an outer ring 2 as an outer member, a hub ring 3 as an inner member, an inner ring 4, two inner ball rows 5 as rolling rows, an outer ball row 6, an inner seal member 9 as a seal member, and an outer seal member 10 as a seal member. Here, in this specification, the inner side refers to the vehicle body side of the wheel bearing device 1 when the wheel bearing device 1 is mounted on the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when the wheel bearing device 1 is mounted on the vehicle body. In addition, the direction parallel to the rotation axis of the wheel bearing device 1 is referred to as the "axial direction", the direction perpendicular to the rotation axis of the wheel bearing device 1 is referred to as the "radial direction", and the direction along the arc centered on the rotation axis of the wheel bearing device 1 is referred to as the "circumferential direction". Additionally, the side moving away from the inside of the bearing along the rotation axis is referred to as the "axially outer side," and the side moving toward the inside of the bearing along the rotation axis is referred to as the "axially inner side."

[0015] The outer ring 2 supports the hub ring 3 and the inner ring 4 via an inner ball row 5 and an outer ball row 6. The outer ring 2 is formed in a substantially cylindrical shape. An inner side opening 2a is formed at the inner side end of the outer ring 2, into which an inner side seal member 9 can be fitted. An outer side opening 2b is formed at the outer side end of the outer ring 2, into which an outer side seal member 10 can be fitted.

[0016] An inner-side outer raceway surface 2c and an outer-side outer raceway surface 2d are provided on the inner diameter surface of the outer ring 2. A vehicle body mounting flange 2e for mounting to a knuckle of a suspension system is integrally formed on the outer peripheral surface of the outer ring 2.

[0017] The hub wheel 3 supports the wheel of a vehicle so that it can rotate freely. The hub wheel 3 is formed in a cylindrical shape. At the inner end of the hub wheel 3, a small diameter step 3a is formed with a reduced diameter on the outer circumferential surface. At the outer end of the hub wheel 3, a wheel mounting flange 3b for mounting a wheel is integrally formed. Hub bolts 3d are inserted into the wheel mounting flange 3b at circumferentially evenly spaced positions. The hub wheel 3 is arranged such that the inner raceway surface 3c on the outer side faces the outer raceway surface 2d on the outer side of the outer ring 2. An inner ring 4 is fitted into the small diameter step 3a of the hub wheel 3.

[0018] The inner ring 4 applies preload to the inner ball row 5 and the outer ball row 6. An annular inner raceway surface 4a is formed in the circumferential direction on the outer peripheral surface of the inner ring 4. The inner ring 4 is fixed to the inner end of the hub ring 3 by crimping. In other words, the inner raceway surface 4a is formed on the inner side of the hub ring 3 by the inner ring 4. The inner ring 4 is arranged such that its inner raceway surface 4a faces the outer raceway surface 2c on the inner side of the outer ring 2.

[0019] In the inner ball row 5 and the outer ball row 6, a plurality of balls 8, which are rolling elements, are held in an annular shape by a resin cage 7. The inner ball row 5 is rollably interposed between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2c of the outer ring 2. The outer ball row 6 is rollably interposed between the inner raceway surface 3c of the hub ring 3 and the outer outer raceway surface 2d of the outer ring 2.

[0020] The cage 7 holds the balls 8. The cage 7 is made of synthetic resins with excellent oil resistance, wear resistance, and lubricity, such as polyamide 46 (PA46), polyamide 66 (PA66), polyamide 9T (PA9T), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), etc. Furthermore, the resin may contain glass fiber, carbon fiber, etc. as a reinforcing material.

[0021] As shown in Fig. 2, the cage 7 has an annular ring portion 7a and multiple pillar portions 7b. The pillar portions 7b extend axially outward from the ring portion 7a. The pillar portions 7b are arranged at equal intervals along the circumferential direction of the ring portion 7a. In the cage 7, pockets Pt that independently hold balls 8 are formed at equal intervals between adjacent pillar portions 7b (see Fig. 3).

[0022] The balls 8 are formed of steel balls made of high carbon chromium bearing steel SUJ2, etc. The plurality of balls 8 are rotatably held in pockets Pt of the cage 7.

[0023] As shown in Fig. 1, the inner seal member 9 closes the gap between the inner opening 2a of the outer ring 2 and the inner ring 4. The inner seal member 9 is, for example, a two-side lip type pack seal in which two seal lips are in contact with each other. The inner seal member 9 includes a substantially cylindrical seal plate and a substantially cylindrical slinger.

[0024] The outer seal member 10 seals the gap between the outer opening 2b of the outer ring 2 and the hub wheel 3. The outer seal member 10 has a core bar made of a steel plate of the same material as the seal plate, formed into a substantially cylindrical shape, and multiple seal lips made of synthetic rubber such as NBR (acrylonitrile-butadiene rubber) are fixed to the core bar.

[0025] Next, the cage 7 will be described in detail with reference to FIGS.

[0026] As shown in Fig. 2, the annular portion 7a is located axially inward of a center position P1 of the ball 8. The columnar portions 7b are provided on both the inner diameter side and the outer diameter side of the annular portion 7a. The columnar portion 7c on the inner diameter side extends in the axial direction from the annular portion 7a. The columnar portion 7d on the outer diameter side has a first portion 7f that extends from the annular portion 7a at an angle away from the outer peripheral surface of the annular portion 7a toward the outer diameter side, and a second portion 7g that extends in the axial direction from the first portion 7f.

[0027] An axial end face S1 of the inner diameter side column portion 7c is formed closer to the annular portion 7a than an axial end face S2 of the outer diameter side column portion 7d. In other words, the inner diameter side column portion 7c is formed shorter in the axial direction than the outer diameter side column portion 7d.

[0028] As shown in Fig. 3 and Fig. 4, in the portion consisting of the annular portion 7a side of the opposing side surfaces of the adjacent column portions 7b and the annular portion 7a between them, a curved surface 7e along the outer circumferential surface of the ball 8 is formed in a substantially hemispherical shape with the annular portion 7a as the bottom. In addition, the column portion 7d on the outer diameter side is formed with a guide surface 7h that extends straight in the axial direction from the edge of the hemispherical curved surface 7e toward the tip of the column portion 7b (see Fig. 6). The guide surface 7h is configured to guide the ball 8 from the tip of the column portion 7b into the space surrounded by the curved surface 7e. As a result, the retainer 7 has pockets Pt formed at equal intervals between the adjacent column portions 7b, which hold the balls 8 from the curved surface 7e and the guide surface 7h.

[0029] The balls 8 come into contact with the inner surface of the column portion 7b, thereby restricting the minimum distance on the pitch circle PCD between adjacent balls 8. The thickness of the column portion 7b is the thinnest on the pitch circle PCD, and gradually becomes thicker toward the inner diameter side and the outer diameter side.

[0030] The curved surface 7e of the pillar portion 7b is curved with the approximate center of the adjacent pillar portion 7b as the bottom. The interval between the adjacent pillar portions 7b is formed so that the interval Wi between the inner diameter side ends and the interval Wo between the radially outer ends are smaller than the interval Wc between the approximate radial centers. This allows the pillar portions 7b to restrict the movement of the balls 8 arranged inside the pocket Pt in the radially inward and outward directions. At the tip portion of the outer diameter side pillar portion 7d, claw portions 7j are formed, which protrude toward the adjacent pillar portions 7b on both sides in the circumferential direction (see FIG. 6).

[0031] As shown in FIG. 2, a cutout 7k having a curved surface of a predetermined radius is formed in the approximate center of the radial width of the column portion 7b. The cutout 7k branches the column portion 7c on the inner diameter side from the column portion 7d on the outer diameter side, and is formed by removing a member in the approximate center of the radial width of the column portion 5b. For example, the cutout 7k is formed so as to remove a portion that does not have the necessary strength, centered on the portion where the thickness of the column portion 7b is thinnest due to the curved surface 7e and the guide surface 7h (see FIG. 6). The shape of the cutout 7k is not particularly limited, and may be formed by removing a member of the column portion 5b so that the facing surfaces of the column portion 7c on the inner diameter side and the column portion 7d on the outer diameter side extend parallel to each other at the tip of the column portion 7c on the inner diameter side. The end position P2 of the cutout 7k on the annular portion 5a side is located closer to the annular portion 7a than the center position P1 of the ball 8. Furthermore, the center positions P1 of the balls 8 are located within the range of the radial width W (see FIG. 5) of the cutout portions 7k. In other words, the pillar portions 7b are formed so as not to circumferentially overlap with the center positions P1 of the balls 8. By configuring the cage in this way, the spacing between the balls 8 becomes smaller, and the number of balls 8 that the cage can hold can be increased.

[0032] Next, the features and effects of the wheel bearing device 1 will be described with reference to Figures 5 and 6. In the following, the axial length will be described starting from the end 7p of the annular portion 7a axially opposite to the column portion 7c.

[0033] As shown in Fig. 5, the cage 7 is bifurcated into an inner diameter side column portion 7c and an outer diameter side column portion 7d by the cutout portion 7k. The inner diameter side column portion 7c is formed so that its axial length a is shorter than the axial length b to the center position P1 of the ball 8. The inner diameter side column portion 7c is also formed so that its axial length a is longer than the axial length c to the end position P2 of the cutout portion 7k on the annular portion 5a side. In other words, the axial length a of the inner diameter side column portion 7c is shorter than the axial length b to the center position P1 of the ball 8 and longer than the axial length c to the end position P2 of the cutout portion 7k on the annular portion 5a side.

[0034] The outer diameter side pillar portion 7d is formed so that its axial length is longer than the axial length b to the center position P1 of the ball 8. As a result, the outer diameter side pillar portion 7d restricts the axial movement of the ball 8 by the claw portions 7j (see FIG. 6).

[0035] In this way, in the wheel bearing device 1, the axial length a of the inner diameter side pillar portion 7c is formed shorter than in the past, so that the fillability of the resin into the pillar portion 7b is improved. In addition, the approach area between the balls 8 and the retainer 7 is reduced, so that the shear resistance of the grease between the pillar portion 7b and the balls 8 is reduced. Therefore, the fillability of the resin in the injection molding of the retainer 7 is improved, and the increase in the bearing torque can be suppressed. In addition, the fillability of the resin into the pillar portion 7b is improved, so that the moldability of the retainer 7 is improved and the strength of the retainer 7 can be ensured. In addition, the axial length a of the inner diameter side pillar portion 7c is formed shorter than in the past, so that the weight of the retainer 7 can be reduced.

[0036] The cage 7 is an injection-molded body made of resin. During injection molding, resin is injected into a mold from a gate of the mold. The cage 7 has a gate portion 7m, which is located at a position corresponding to the gate of the mold. The cage 7 has a weld 7n formed by the joining of the resin filled from the gate portion 7m.

[0037] As shown in FIG. 6, the gate portion 7m is provided on the inner diameter surface of the annular portion 7a and is located on the axial extension of the column portion 7c on the inner diameter side. In other words, the gate portion 7m is provided on the annular portion 7a and is located on the axial extension of the column portion 7b. The welds 7n are located midway between the column portions 7b. The gate portions 7m are provided in several locations, and the number of locations is determined according to the cage 7. The welds 7n have lower strength than other portions where the welds 7n are not formed. Since the number of welds 7n increases according to the number of gate portions 7m, it is preferable to minimize the number of gate portions 7m within the range where resin can be filled.

[0038] In this way, in the wheel bearing device 1, the gate portion 7m into which the resin is filled is provided in the annular portion 7a and located on the axial extension of the pillar portion 7b, so that the filling of the resin into the pillar portion 7b can be improved. Also, by preventing the weld 7n from being formed in the pillar portion 7b, the moldability of the cage 7 can be improved.

[0039] Next, other features and effects of the wheel bearing device 1 will be described with reference to FIG.

[0040] In the wheel bearing device 1, grease is sealed inside the bearing in which the balls 8 are provided. The kinetic viscosity of the grease is 30 mm 2 / s~200mm 2 If the kinetic viscosity of the grease is too low, the oil film formation becomes insufficient, and there is a risk of damage to the cage 7 and the like. On the other hand, if the kinetic viscosity of the grease is too high, the viscous resistance becomes large, leading to an increase in temperature rise and friction loss. In the wheel bearing device 1, the kinetic viscosity is set to 30 mm 2 / s~200mm 2 / s optimizes the kinetic viscosity of the grease.

[0041] Also, a pocket gap e is provided between the pocket Pt and the ball 8. The pocket gap e is preferably 0.05 mm to 0.45 mm. The cage 7 can move freely relative to the ball 8 within the range of the pocket gap e. If the pocket gap e is too small, the pocket Pt and the ball 8 may interfere with each other and be damaged. On the other hand, if the pocket gap e is too large, the ball 8 may rattle within the pocket Pt, deteriorating acoustic characteristics. In the wheel bearing device 1, the pocket gap e is optimized by setting the pocket gap e to 0.05 mm to 0.45 mm as described above.

[0042] Although the embodiment of the present invention has been described above, the present invention is not limited to these embodiments, but is merely illustrative, and can of course be embodied in various other forms without departing from the spirit of the present invention, and the scope of the present invention is set forth in the claims, and further includes the equivalent meanings set forth in the claims and all modifications within the scope of the claims. In addition, in this embodiment, the wheel bearing device 1 is configured as a wheel bearing device of a third generation structure in which the inner raceway surface 3c is directly formed on the outer periphery of the hub wheel 3, but is not limited to this, and may be a second generation structure in which a pair of inner rings are press-fitted and fixed to the hub wheel, or a first generation structure in which a double-row angular contact ball bearing is fitted between the knuckle and the hub wheel. [Explanation of symbols]

[0043] 1 Wheel bearing device 2 Outer ring (outer component) 2c Outer raceway surface 2d outer raceway 3 Hub ring (inner part) 3c Inner raceway surface 4 Inner ring (inner component) 4a Inner raceway surface 5 Inner ball row 6 Outer ball row 7 Cage 7a Circular section 7b Pillar part 7c Inner diameter side column 7d Outer diameter column 7e Curved surface along the outer periphery of the rolling element 7m Gate 7n Weld 7p End of the ring part on the axially opposite side of the column part 8 balls (rolling elements) a Axial length of the column part on the inner diameter side b Axial length to the center position of the rolling element c Axial length to the end position of the notch on the annular part side e Pocket gap P1 Ball center position P2 End position of the notch on the annular side Pt Pocket W Radial width of the cutout

Claims

1. an outer member having a double row outer raceway surface formed on an inner periphery thereof; an inner member having a double row inner raceway surface opposed to the double row outer raceway surface; a double row of rolling elements rollably interposed between both raceway surfaces of the outer member and the inner member; a resin cage having an annular portion formed in an annular shape and a plurality of bar portions extending in an axial direction at regular intervals from the annular portion in a circumferential direction, wherein adjacent bar portions and the annular portions form pockets having curved surfaces that conform to outer circumferential surfaces of the rolling elements, and the rolling elements are held in the pockets; The pillar portion is formed by being branched into an inner diameter side and an outer diameter side by a cutout portion, Starting from the end of the annular portion on the axially opposite side to the column portion, The axial length of the column portion on the inner diameter side is The length is shorter than the axial length to the center position of the rolling element, and the length of the cutout portion to the end position of the annular portion in the axial direction is longer than the length of the cutout portion to the end position of the annular portion in the axial direction, A wheel bearing device, characterized in that a center position of the rolling element is located within a range of a radial width of the cutout portion.

2. 2. The wheel bearing device according to claim 1, wherein an end position of the cutout portion on the annular portion side is located closer to the annular portion than a center position of the rolling element.

3. the cage is an injection molded body having a gate portion, the gate portion being located corresponding to a gate of a mold into which a resin is injected during injection molding; 3. The wheel bearing device according to claim 1, wherein the gate portion is provided on the annular portion and is located on an axial extension of the column portion.

4. the cage has a weld formed by the resin filling the gate portion joining together, 4. The wheel bearing device according to claim 3, wherein the weld is positioned midway between the pillar portions.

5. Grease is sealed inside the bearing in which the rolling elements are arranged, The grease has a dynamic viscosity of 30 mm ２ / s~200mm ２ 5. The wheel bearing device according to claim 1, wherein the ratio of the rotational speed of the wheel to the rotational speed of the bearing is 0.1 to 0.

25.

6. 6. The wheel bearing device according to claim 1, wherein a pocket clearance between the rolling element and the pocket is 0.05 mm to 0.45 mm.

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