Wheel bearing device

Abstract

To provide a bearing device for a wheel which enables improvement of repletion of resin in injection molding of a retainer and can inhibit increase of bearing torque.SOLUTION: A bearing device 1 for a wheel includes: a resin retainer 7 which has an annulus part 7a formed into an annular shape and multiple column parts 7b which extends from the annulus part 7a in an axial direction and arranged at constant intervals in a circumferential direction and in which a pocket Pt having a curve surface 7c along an outer peripheral surface of a rolling element (8) is formed by the adjacent column parts 7b and the annulus part 7a and the rolling element (8) is retained in each pocket Pt. The column part 7b has: a root part 7f extending from the annulus part 7a in the axial direction; and a branch part 7b extending from the root part 7f in the axial direction. The branch part 7b is formed only at the outer diameter side of the root part 7f.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Conventionally, a wheel bearing device for rotatably supporting a wheel in a suspension device such as an automobile has been known. In the wheel bearing device, an inner member including a hub ring is rotatably supported by an outer member via a plurality of rolling elements (here, balls). The plurality of balls are equally arranged in the circumferential direction by a cage and are held in a state where contact between adjacent balls is prevented.

[0003] In such a wheel bearing device, by reducing the circumferential thickness of the column portion of the cage that separates adjacent balls and forming a notch in the column portion to increase the number of balls, a cage has been known that enables an increase in bearing life without a problem of insufficient strength. For example, it is as described in Patent Document 1 and Patent Document 2.

[0004] In the cages described in Patent Document 1 and Patent Document 2, the circumferential thickness of the column portion of the cage is reduced, and a notch is formed in the portion where adjacent balls are closest to each other. That is, between adjacent balls, the column portion does not intervene in the closest portion. Thereby, the cage has a structure in which the number of balls that can be incorporated is increased by shortening the circumferential ball-to-ball distance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the retainers described in Patent Documents 1 and 2 above, the columnar portion is branched into two branches, an inner diameter side and an outer diameter side, by a notch. In Patent Document 1, as shown in Figure 7(A), starting from the end of the annular portion opposite the columnar portion in the axial direction, the axial length a1 of the inner diameter side columnar portion is approximately the same as the axial length b1 to the center position of the ball. In Patent Document 2, as shown in Figure 7(B), starting from the end of the annular portion opposite the columnar portion in the axial direction, the axial length a2 of the inner diameter side columnar portion is longer than the axial length b2 to the center position of the ball. With such a shape of the inner diameter side columnar portion, there is a concern that the resin may not reach the tip of the columnar portion during injection molding of the retainer, potentially leading to inconsistent quality of the retainer.

[0007] Furthermore, with the increasing fuel efficiency of vehicles in recent years, there is a demand for lower torque in wheel bearing systems. In cages, shear resistance of the grease occurs between the cage and the balls when the wheel bearing system rotates, leading to an increase in bearing torque, and therefore improvements are needed.

[0008] Therefore, the present invention aims to provide a wheel bearing device that improves the resin filling performance in injection molding of the retainer and suppresses the 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 double rows of outer raceway surfaces formed on its inner circumference; an inner member having double rows of inner raceway surfaces facing the double rows of outer raceway surfaces; double rows of rolling elements interposed between the raceway surfaces of the outer member and the inner member so as to be rotatable; and a resin retainer having an annularly formed ring portion and a plurality of columnar portions extending axially from the ring portion at regular intervals in the circumferential direction, wherein adjacent columnar portions and the ring portion form a pocket having a curved surface along the outer circumferential surface of the rolling elements, and the pocket holds the rolling elements, wherein the columnar portions have a root portion extending axially from the ring portion and a branch portion extending axially from the root portion, and the branch portions are formed only on the outer diameter side of the root portion.Furthermore, the base portion has an inclined surface on the inner diameter side of the base portion that connects to the branch portion, and the inclined surface of the base portion is located on the annular portion side of the center position of the rolling element. This is the result. [Effects of the Invention]

[0010] The present invention provides the following effects:

[0011] In other words, according to the first invention, the resin filling performance into the column portion is improved, and the shear resistance of the grease between the ball and the column portion is reduced. Therefore, the resin filling performance in the injection molding of the retainer can be improved, and the increase in bearing torque can be suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] A cross-sectional view showing the overall configuration of a wheel bearing device. [Figure 2] An enlarged cross-sectional view showing the configuration of the ball and retainer. [Figure 3] A plan view showing the overall configuration of the retainer. [Figure 4] A cross-sectional view showing the overall structure of the retainer. [Figure 5] Enlarged cross-sectional view showing the axial length of the inner diameter end of the retainer. [Figure 6] An enlarged perspective view showing the structure of the column section. [Figure 7] An enlarged cross-sectional view showing the axial length of the inner diameter column in a conventional retainer. [Modes for carrying out the invention]

[0013] Below, an embodiment of the wheel bearing device according to the present invention, namely a wheel bearing device 1, will be described with reference to Figures 1 and 2.

[0014] As shown in FIG. 1, the wheel bearing device 1 rotatably supports a wheel 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 side ball rows 5 as rolling element rows, an outer side ball row 6, an inner side seal member 9 as a seal member, and an outer side 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 attached to 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 attached to the vehicle body. Also, the direction parallel to the rotation axis of the wheel bearing device 1 is referred to as the "axial direction", the direction orthogonal to the rotation axis of the wheel bearing device 1 is referred to as the "radial direction", and the direction along an arc centered on the rotation axis of the wheel bearing device 1 is referred to as the "circumferential direction". Further, the side away from the inside of the bearing along the rotation axis is referred to as the "outer side in the axial direction", and the side approaching the inside of the bearing along the rotation axis is referred to as the "inner side in the axial direction".

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

[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 attachment flange 2e for attachment to a knuckle of the suspension device is integrally formed on the outer peripheral surface of the outer ring 2.

[0017] The hub ring 3 rotatably supports the vehicle wheel. The hub ring 3 is formed in a cylindrical shape. At the inner side end of the hub ring 3, a small-diameter stepped portion 3a with a reduced outer peripheral diameter is formed. At the outer side end of the hub ring 3, a wheel mounting flange 3b for mounting the wheel is integrally formed. Hub bolts 3d are inserted through the wheel mounting flange 3b at circumferentially equally spaced positions. Further, the hub ring 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 to the small-diameter stepped portion 3a of the hub ring 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 side end of the hub ring 3 by caulking. That is, on the inner side of the hub ring 3, the inner raceway surface 4a is formed 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] The inner ball row 5 and the outer ball row 6 are annularly held by a resin cage 7 with a plurality of balls 8 as rolling elements. The inner ball row 5 is interposed between the inner raceway surface 4a of the inner ring 4 and the outer raceway surface 2c on the inner side of the outer ring 2 so as to be freely rotatable. The outer ball row 6 is interposed between the inner raceway surface 3c of the hub ring 3 and the outer raceway surface 2d on the outer side of the outer ring 2 so as to be freely rotatable.

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

[0021] As shown in Figure 2, the retainer 7 has an annular ring portion 7a and a plurality of columnar portions 7b. The columnar portions 7b extend axially outward from the ring portion 7a. The columnar portions 7b are arranged at equal intervals along the circumferential direction of the ring portion 7a. Pockets Pt for independently holding the balls 8 are formed in the retainer 7 at equal intervals between adjacent columnar portions 7b (see Figure 3).

[0022] The ball 8 is made of steel balls made of high-carbon chromium bearing steel SUJ2. Multiple balls 8 are rotatably held in pockets Pt of the cage 7.

[0023] As shown in Figure 1, the inner side sealing member 9 closes the gap between the inner side opening 2a of the outer ring 2 and the inner ring 4. The inner side sealing member 9 is composed of, for example, a two-side lip type pack seal that brings two sealing lips into contact. The inner side sealing member 9 comprises a substantially cylindrical sealing plate and a substantially cylindrical slinger.

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

[0025] Next, the retainer 7 will be explained in detail using Figures 2 to 4.

[0026] As shown in Figure 2, the annular portion 7a is located axially inward from the center position P1 of the ball 8. The columnar portion 7b does not branch out toward the inner diameter side of the annular portion 7a, but extends inclined away from the annular portion 7a toward the outer diameter side of the outer diameter surface 7q of the annular portion 7a, and extends axially from the inclined portion.

[0027] As shown in Figures 3 and 4, a curved surface 7c is formed in a substantially hemispherical shape with the annular portion 7a as its base, along the outer circumferential surface of the ball 8, in the portion formed by the annular portion 7a on the opposing sides of adjacent columnar portions 7b and the annular portion 7a between them. In addition, a guide surface 7d is formed on the columnar portion 7b, extending straight in the axial direction from the edge of the hemispherical curved surface 7c toward the tip of the columnar portion 7b (see Figure 6). The guide surface 7d is configured to guide the ball 8 from the tip of the columnar portion 7b into the space enclosed by the curved surface 7c. As a result, the retainer 7 has equally spaced pockets Pt for holding the ball 8 between adjacent columnar portions 7b, formed by the curved surface 7c and the guide surface 7d.

[0028] The balls 8 contact the inner surface of the column 7b, thereby restricting the minimum spacing between adjacent balls 8 on the pitch circle PCD. The thickness of the column 7b is thinnest on the pitch circle PCD and gradually increases as you move away from it towards the inner and outer diameters.

[0029] The curved surface 7c of the column portion 7b is curved with the approximate center of the adjacent column portion 7b as its base. The spacing between adjacent column portions 7b is formed such that the spacing Wi between the inner diameter ends and the spacing Wo between the radially outer ends are smaller than the spacing Wc between the approximate radial centers. In this way, the column portion 7b restricts the radially inward and radially outward movement of the ball 8 located inside the pocket Pt. At the tip of the column portion 7b, claw portions 7e are formed that protrude toward the adjacent column portions 7b on both sides in the circumferential direction (see Figure 6).

[0030] As shown in Figure 2, the columnar portion 7b has a base portion 7f extending axially outward from the annular portion 7a, and a branch portion 7g extending axially outward from the outer diameter side of the base portion 7f. Furthermore, the branch portion 7g extends on the outer diameter side of the annular portion 7a. In other words, there is no branch portion 7g on the inner diameter side of the annular portion 7a.

[0031] The base portion 7f holds the ball 8 at the base end of the column portion 7b. The base portion 7f has an inner diameter surface 7h and an inclined surface 7j. The inner diameter surface 7h is formed extending axially outward from the inner diameter surface 7k of the annular portion 7a. The inclined surface 7j is formed extending inclined away from the inner diameter surface 7h toward the outer diameter and is connected to the branch portion 7g (curved surface 7m).

[0032] The branch portion 7g holds the ball 8 at the tip of the column portion 7b. The branch portion 7g is formed only on the outer diameter side of the base portion 7f. Specifically, the radial center line L of the branch portion 7g is located on the outer diameter side of the outer diameter surface 7q of the annular portion 7a. The branch portion 7g has a curved surface 7m, an inner diameter surface 7n, and an axial end surface S. The curved surface 7m is formed extending from the inclined surface 7j in a cross-sectional arc shape. The inner diameter surface 7n is formed extending axially from the curved surface 7m toward the axial end surface S of the column portion 7b. Thus, the column portion 7b is configured such that no axially extending branch portions are formed on the inner diameter side of the base portion 7f. The radial center line L is a line parallel to the axial direction and passes through the radial center of the axial end surface S.

[0033] The inner diameter surface 7n is located on the outer diameter side of the ball 8's center position P1. The inclined surface 7j is located on the annular portion 7a side of the ball 8's center position P1. In other words, the column portion 7b is formed so as not to overlap the ball 8's center position P1 in the circumferential direction. This configuration allows the holder 7 to reduce the spacing between the balls 8 and increase the number of balls 8 it can hold. The shapes of the surfaces of the base portion 7f and the branch portion 7g can be modified as appropriate. For example, although the inclined surface 7j is shown as a straight shape, it may also be a bent or curved shape.

[0034] Next, using Figures 5 and 6, the axial length from the inner diameter surface 7h of the root portion 7f to the tip position P2 will be explained in detail. In the following explanation, the axial length will be described starting from the end portion 7p of the annular portion 7a on the axial side opposite to the root portion 7f.

[0035] As shown in Figure 5, the retainer 7 is formed such that the axial length a to the tip position P2 is shorter than the axial length d to the base end position of the branch portion 7g (the axial length to the base end position P3 of the curved surface 7m). Furthermore, the retainer 7 is formed such that the axial length a to the tip position P2 is longer than the axial length e to the tip position P4 on the inner diameter surface 7k of the annular portion 7a. In other words, the axial length a to the tip position P2 is shorter than the axial length d to the base end position of the branch portion 7g, and longer than the axial length e to the tip position P4 on the inner diameter surface 7k of the annular portion 7a.

[0036] Furthermore, the column portion 7b is formed so that its axial length to the axial end face S is longer than its axial length to the center position P1 of the ball 8. As a result, the column portion 7b restricts the axial movement of the ball 8 by the claw portion 7e (see Figure 6).

[0037] Thus, in the wheel bearing device 1, since the axially extending branches are not formed on the inner diameter side of the root portion 7f, the resin filling performance on the inner diameter side of the cage 7 is improved. In addition, the reduced proximity area between the ball 8 and the cage 7 reduces the shear resistance of the grease between the column portion 7b and the ball 8. Therefore, the resin filling performance in injection molding of the cage 7 is improved, and the increase in bearing torque can be suppressed. Furthermore, since the resin filling performance on the inner diameter side of the cage 7 is improved, the moldability of the cage 7 is improved, and the strength of the cage 7 can be ensured. In addition, since the axially extending branches are not formed on the inner diameter side of the root portion 7f, the weight of the cage 7 can be reduced.

[0038] Next, using Figures 2 and 6, we will explain other features and effects of the wheel bearing device 1.

[0039] The wheel bearing device 1 has grease sealed inside the bearing, which is equipped with balls 8. The kinematic viscosity of the grease is 30 mm². 2 / s~200mm 2A kinematic viscosity of 30 mm² is preferred. If the kinematic viscosity of the grease is too low, the oil film formation will be insufficient, which may damage the cage 7, etc. On the other hand, if the kinematic viscosity of the grease is too high, the viscous resistance will increase, leading to increased temperature rise and friction loss. In the wheel bearing device 1, the kinematic viscosity is set to 30 mm² as described above. 2 / s~200mm 2 By setting it to / s, the kinematic viscosity of the grease is optimized.

[0040] Furthermore, a pocket gap f is provided between the pocket Pt and the ball 8. The pocket gap f is preferably 0.05 mm to 0.45 mm. The retainer 7 can move freely relative to the ball 8 within the range of the pocket gap f. If the pocket gap f 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 f is too large, the ball 8 will rattle within the pocket Pt, degrading the acoustic characteristics. In the wheel bearing device 1, the pocket gap f is optimized by setting it to 0.05 mm to 0.45 mm as described above.

[0041] Furthermore, the retainer 7 is an injection-molded resin product. During injection molding, resin is injected into the mold from the gate of the mold. The retainer 7 has a gate portion 7r, which is located at a position corresponding to the gate of the mold. The retainer 7 has a weld 7s formed by the convergence of the resin filled from the gate portion 7r.

[0042] As shown in Figure 6, the gate portion 7r is provided on the inner diameter surface 7k of the annular portion 7a and is located on the axial extension of the column portion 7b. The weld 7s is located midway between the column portions 7b. Several gate portions 7r are provided, and the number of them is determined according to the retainer 7. The weld 7s has lower strength than other parts where weld 7s are not formed. Since the number of weld 7s increases with the number of gate portions 7r installed, it is preferable to minimize the number of gate portions 7r installed within the range where resin filling is possible.

[0043] Thus, in the wheel bearing device 1, the gate portion 7r into which the resin is filled is provided on the annular portion 7a and is located on the axial extension of the column portion 7b, which improves the ability to fill the column portion 7b with resin. In addition, by preventing the formation of weld lines 7s on the column portion 7b, the moldability of the retainer 7 can be improved.

[0044] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, and these are merely examples. It is understood that the invention can be implemented in various other forms without departing from the spirit of the invention, and the scope of the present invention is indicated by the claims, and further includes all modifications within the meaning and scope of equivalents as described in the claims. In addition, in this embodiment, the wheel bearing device 1 is configured as a third-generation wheel bearing device in which the inner raceway surface 3c is directly formed on the outer circumference of the hub ring 3, but it 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 ring, or a first-generation structure in which a double row of angular contact ball bearings is fitted between the knuckle and the hub ring. [Explanation of symbols]

[0045] 1. Wheel bearing device 2. Outer ring (outer member) 2c Outer raceway surface 2d outer raceway 3. Hub ring (inner member) 3c Inner raceway surface 4. Inner ring (inner member) 4a Inner raceway surface 5. Inner ball row 6 Outer ball rows 7 Cage 7a Annular section 7b Pillar part 7f Root 7g branch 7h Inner diameter surface of the base 7j Sloping surface at the base 7k Inner diameter surface of the annular section 7n Inner diameter surface of the branch 7p The end of the ring portion opposite the base and the axial direction. 7q Outer diameter surface of the annular portion 7r Gate section 7s Weld 8. Ball (rolling element) a. Axial length from the inner diameter surface of the base to the tip position d. Axial length to the base of the branch. e. Axial length from the inner diameter surface of the annular portion to the tip position. f Pocket gap L Radial center line P1 Center position of the rolling element P2 Tip position of the inner diameter surface at the base P4 Tip position on the inner diameter surface of the annular portion Pt Pocket

Claims

1. An outer member having double rows of outer raceway surfaces formed on its inner circumference, An inner member having a double row of inner raceway surfaces facing the double row of outer raceway surfaces, A double row of rolling elements is interposed between the raceway surfaces of the outer member and the inner member so as to be rotatable, It has an annular ring portion and a plurality of columnar portions extending axially from the annular portion at regular intervals in the circumferential direction, and adjacent columnar portions and the annular portion form a pocket having a curved surface along the outer surface of the rolling element, and a resin retainer holds the rolling element in the pocket, A wheel bearing device comprising, The column portion has a base portion extending axially from the annular portion and a branch portion extending axially from the base portion, and the branch portion is formed only on the outer diameter side of the base portion. The base portion has an inclined surface on the inner diameter side of the base portion that connects to the branch portion. A wheel bearing device characterized in that the inclined surface of the root portion is located on the annular portion side of the center position of the rolling element.

2. The wheel bearing device according to claim 1, characterized in that the radial center line of the branch portion is located on the outer diameter side of the outer diameter surface of the annular portion.

3. The root portion has an inner diameter surface of the root portion that extends axially from the inner diameter surface of the annular portion, The wheel bearing device according to claim 1 or 2, characterized in that, starting from the end of the annular portion opposite the root portion in the axial direction, the axial length from the end of the annular portion on the inner diameter surface of the root portion to the tip position is shorter than the axial length from the base end position of the branch portion and longer than the axial length from the end of the annular portion on the inner diameter surface of the annular portion.

4. The bearing in which the rolling elements are arranged is sealed with grease. The aforementioned grease has a kinematic viscosity of 30 mm ２ / s ~ 200mm ２ A wheel bearing device according to any one of claims 1 to 3, characterized in that it is / s.

5. The wheel bearing device according to any one of claims 1 to 4, characterized in that the pocket clearance between the rolling element and the pocket is 0.05 mm to 0.45 mm.

6. The retainer is an injection-molded body having a gate portion, and the gate portion is positioned in correspondence with the gate of the mold into which the resin is injected during injection molding. The wheel bearing device according to any one of claims 1 to 5, characterized in that the gate portion is provided on the annular portion and is located on the axial extension of the column portion.

7. The retainer has a weld formed by the merging of the resin that was filled from the gate portion. The wheel bearing device according to claim 6, characterized in that the weld is located midway between the column portions.

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