JP2024107907A - Hub unit bearing - Google Patents

Abstract

To provide a hub unit bearing which provides rigidity in a circumferential direction and an axial direction which is close to rigidity of a round flange to a hub flange while achieving reduction of the weight.SOLUTION: An inner ring member 30 of a hub unit bearing 10 has: a hub shaft 31 in which a plurality of outward-directed flange parts 33 are provided at intervals in a circumferential direction; and a plurality of reinforcement members 40 each of which is disposed between circumferential side surfaces 33b of the outward-directed flange parts 33 located adjacent to each other in the circumferential direction, cooperates with the outward-directed flange parts 33 to form a disc-like hub flange 38, and is formed of a material which is lighter than the hub shaft 31. The circumferential side surface 33b of the outward-directed flange part 33 and a circumferential side surface 40a of the reinforcement member 40 are connected by engagement of a protruding part formed on one of the circumferential side surfaces and a recessed part formed at the other circumferential side surface.SELECTED DRAWING: Figure 2

Description

The present invention relates to a hub unit bearing.

Hub unit bearings are the unsprung load, so reducing the weight of these bearings not only contributes to energy and resource conservation, but also has a significant impact on improving ride comfort. In order to reduce the weight of hub unit bearings, it is most effective to reduce the weight of the hub flange, which has a large diameter and therefore a large mass. This reduces the energy required to start and stop the vehicle, and also reduces fuel consumption by reducing inertia.

Patent Document 1 discloses a hub unit bearing in which the hub flange is intermittently provided by cold lateral extrusion, i.e., multiple outward flange portions are provided at intervals in the circumferential direction, to reduce the weight of the hub flange. In this type of structure, the work hardening effect of cold forging also has the effect of making the hub flange thinner, making it possible to reduce the weight of the hub flange.

JP 2011-201421 A

However, with the hub unit bearing described in Patent Document 1, the contact area between the hub flange and the brake rotor is reduced, which raises concerns about increased stress in the mounting area. In addition, hub flanges formed intermittently (in a cross or star shape) have lower circumferential and axial rigidity than continuously formed disk-shaped flanges, so-called round flanges, which may affect handling stability and increase stress in the mounting areas of the wheel and brake rotor.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a hub unit bearing that is lightweight while providing the hub flange with circumferential and axial rigidity similar to that of a round flange, thereby improving handling stability and reducing stress on the mounting parts of the wheel and brake rotor.

The above object of the present invention can be achieved by the following configuration.
[1] An outer ring member having a double row outer ring raceway on an inner circumferential surface thereof;
an inner ring member having a double row inner ring raceway on its outer circumferential surface and a hub flange on one axial side to which a wheel and a brake rotor are attached;
a plurality of rolling elements disposed between the double row outer ring raceways and the double row inner ring raceways so as to be freely rollable;
A hub unit bearing comprising:
the inner ring member includes a hub axle having a plurality of radially extending outward flange portions spaced apart in the circumferential direction, and a plurality of reinforcing members made of a material lighter than the hub axle, the reinforcing members being respectively disposed between circumferential side surfaces of the outward flange portions adjacent in the circumferential direction and cooperating with the plurality of outward flange portions to form the disk-shaped hub flange,
a circumferential side surface of the outward flange portion and a circumferential side surface of the reinforcing member are connected to each other by engaging a convex portion formed on one of the circumferential side surfaces with a concave portion formed on the other circumferential side surface.
Hub unit bearing.

The hub unit bearing of the present invention provides the hub flange with circumferential and axial rigidity similar to that of a round flange while reducing weight, improving handling and reducing stress at the attachment points of the wheel and brake rotor.

FIG. 1 is a cross-sectional view of a hub unit bearing according to a first embodiment of the present invention. FIG. 2 is a perspective view of the hub axle shown in FIG. FIG. 3 is a side view of a main portion of the hub flange, showing the engagement between the circumferential side surface of the outward flange portion and the circumferential side surface of the reinforcing member. 3A to 3C are diagrams showing an example of a method for manufacturing a hub shaft by cold forging in order of steps. FIG. 2 is a cross-sectional view illustrating a cold forging device for manufacturing a hub shaft. FIG. 6 is a side view of a main portion of the hub flange, showing another state of engagement between the circumferential side surface of the outward flange portion and the circumferential side surface of the reinforcing member. Figure 7(a) is a side view of a key portion of a hub flange showing yet another engagement state between the circumferential side surface of the outward flange portion and the circumferential side surface of the reinforcing member, and Figure 7(b) is a side view of a key portion of a hub flange showing yet another engagement state between the circumferential side surface of the outward flange portion and the circumferential side surface of the reinforcing member. FIG. 8 is a perspective view of a hub axle according to a second embodiment of the present invention. 9 is a side view of a main portion of the hub flange, showing the engagement between the circumferential side surface of the outward flange portion in FIG. 8 and the circumferential side surface of the reinforcing member. 10 is a side view of a main portion of the hub flange, showing another state of engagement between the circumferential side surface of the outward flange portion and the circumferential side surface of the reinforcing member in FIG. 8. FIG.

First Embodiment
A hub unit bearing according to a first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.
In this specification, the "inboard side" refers to the vehicle body side of the hub unit bearing 10 when it is attached to the vehicle body, and is the right side in Fig. 1. The "outboard side" refers to the wheel side of the hub unit bearing 10 when it is attached to the vehicle body, and is the left side in Fig. 1.

The hub unit bearing 10 of this embodiment is for a drive wheel and mainly comprises an outer ring member 20, an inner ring member 30, a number of rolling elements 11, a pair of sealing members 12, and a retainer 13.

The outer ring member 20 has a mounting flange 22 that extends outward from the outer peripheral surface of the body 21, which is formed in a substantially cylindrical shape, and double-row (two-row) outer ring raceways 23a, 23b that are provided on the inner peripheral surface. When in use, the outer ring member 20 is fixed to a knuckle (not shown) of the suspension device by a mounting bolt that is screwed into a screw hole 22a provided in the mounting flange 22, and the outer ring member 20 does not rotate when supported by the suspension device.

The inner ring member 30 is composed of a hub axle 31, an inner ring 32, and multiple reinforcing members 40, and is arranged coaxially (concentrically) with the outer ring member 20 on the inner diameter side of the outer ring member 20. In addition, the inner ring member 30 of this embodiment has double row inner ring raceways 36a, 36b on the outer peripheral surface of the hub axle 31 and the outer peripheral surface of the inner ring 32.

Specifically, an inner raceway 36a is provided on the outer peripheral surface of the hub axle 31 at a portion facing the outer raceway 23a of the outer race member 20, and a small diameter step 35 is provided at a portion facing the outer raceway 23b of the outer race member 20.

The inner ring 32 is fixed to the hub axle 31 by being press-fitted onto the outer circumferential surface of the small diameter step 35 with the outboard end face 32a abutting against the step surface 35a of the small diameter step 35. An inner ring raceway 36b is provided on the outer circumferential surface of the inner ring 32 in a portion facing the outer ring raceway 23b of the outer ring member 20.

A spline hole 37 that axially passes through the rotation axis O is formed on the inner peripheral surface of the cylindrical portion 34 of the hub axle 31. Although not shown, a spline shaft connected to a constant velocity joint engages with the spline hole 37, and the spline shaft and hub axle 31 are fixed by abutting the outboard end face of the spline shaft against the inboard end face 32b of the inner ring 32 and screwing a nut onto the male thread provided at the tip of the spline shaft. This positions and fixes the inner ring 32 in the axial direction relative to the hub axle 31.

The cylindrical portion 34 of the hub axle 31 is provided with a plurality of outward flanges 33 spaced apart in the circumferential direction, extending radially, i.e., extending outward from the cylindrical portion 34, on one axial side that protrudes outboard from the outboard opening of the outer ring member 20. The number of outward flanges 33 is arbitrary; for example, four outward flanges may be provided at 90° intervals, or five outward flanges may be provided at 72° intervals.

A plurality of reinforcing members 40 are disposed between the circumferential side surfaces 33b of the circumferentially adjacent outward flange portions 33, specifically in the substantially sector-shaped space surrounded on three sides by the circumferential side surfaces 33b of the adjacent outward flange portions 33 and the outer circumferential surface of the cylindrical portion 34. The plurality of reinforcing members 40 cooperate with the plurality of outward flange portions to form a disk-shaped hub flange 38, a so-called round flange.

The hub bolt 15, which is a fastening member, is serrated and fitted into the through hole 33a of the outward flange portion 33, and the wheel and brake rotor, both of which are not shown, are fastened together with a nut member, not shown, to attach them to the hub flange 38.

The rolling elements (balls) 11 are arranged back-to-back at a predetermined contact angle between the outer ring raceways 23a, 23b and the inner ring raceways 36a, 36b, and are held by the cage 13 so that they can roll freely. This allows the inner ring member 30 to rotate relative to the outer ring member 20.

A pair of sealing members 12 are disposed between the outboard end of the outer ring member 20 and the axial middle portion of the hub axle 31, and between the inboard end of the outer ring member 20 and the inboard end of the inner ring 32, sealing both axial sides of the internal space 14 in which the multiple rolling elements 11 are provided.

Next, we will explain in detail the hub flange 38, which is a key part of the present invention, with reference to Figure 3.

The outward flange portion 33 of the hub axle 31 is formed, for example, by cold lateral extrusion, in which steel material is pushed out to the side from the extrusion opening of a molding die, and its circumferential width W (see FIG. 2) is formed to be approximately the same on the small diameter side and the large diameter side. The manufacturing method of the hub axle 31, which includes cold lateral extrusion, will be described later.

The reinforcing member 40 has the same thickness as the outward flange portion 33. In other words, both axial side surfaces of the reinforcing member 40 are flush with both axial side surfaces of the outward flange portion 33 without any step. The outer diameter of the reinforcing member 40 is approximately the same as the outer diameter of the outward flange portion 33. The reinforcing member 40 is formed by die-casting or molding a lightweight material such as a light alloy such as an aluminum alloy or a fiber-reinforced plastic (FRP) onto the hub axle 31.

The reinforcing member 40, such as a light alloy or fiber-reinforced resin, has no common area in the liquid phase temperature with the steel outward flange portion 33, and is die-cast or molded while the steel outward flange portion 33 remains in the solid phase. Here, even if the circumferential side surface 33b of the outward flange portion 33 has been roughened by, for example, shot blasting, laser processing, plating, or the like, the reinforcing member 40 is likely to come off from the outward flange portion 33 due to molding shrinkage of the reinforcing member 40.

On the other hand, as shown in FIG. 3, the hub flange 38 of this embodiment has a dovetail groove 41, which is a recess with an inverted V-shaped cross section, formed on the circumferential side surface 33b of the outward flange portion 33, and a reinforcing member 40 is die-cast or molded into the dovetail groove 41, so that a protrusion portion 42, which is a convex portion with an V-shaped cross section, is formed on the circumferential side surface 40a of the reinforcing member 40.

As a result, the outward flange portion 33 and the reinforcing member 40 are connected to each other by the protrusion portion 44 and the dovetail groove 45. In particular, a part of the outward flange portion 33 constituting the dovetail groove 41 is inserted into the recess formed between the tip portion 42a of the protrusion portion 42 and the circumferential side surface 40a of the reinforcing member 40 by the protrusion portion 42 having a tip portion 42a whose axial width is larger than that of the base portion, and as a result, at least a part of the tip portion 42a of the protrusion portion 42 and the circumferential side surface 33b of the outward flange portion 33 overlap when viewed from the circumferential direction. Therefore, the dovetail groove 41 and the protrusion portion 42 firmly engage the outward flange portion 33 and the reinforcing member 40. In addition, the reinforcing member 40 is pulled in the circumferential direction by the molding shrinkage of the reinforcing member 40, and a force toward the center side of the hub axle 31 acts on the reinforcing member 40, so that the reinforcing member 40 does not come off the outward flange portion 33, and the hub flange 38 can be given circumferential and axial rigidity similar to that of a round flange.

The dovetail groove 41 on the circumferential side surface 33b of the outward flange portion 33 can be formed by extruding the outward flange portion 33 to the outer diameter side (side) by cold lateral extrusion of steel material.

Here, as shown in FIG. 4, the hub axle 31 is first prepared as a cylindrical material 60 shown in (A). This material 60 is softened and annealed in advance to make it easy to plastically deform even at room temperature. This material 60 is extruded forward to obtain a stepped first intermediate material 61 as shown in (B). This first intermediate material 61 is then cold forged (extruded) using a floating die to obtain a second intermediate material 62 as shown in (C). Next, this second intermediate material 62 is extruded to form a stepped portion or the like for providing an angular inner ring raceway 36a on the axial outer side, to obtain a third intermediate material 63 as shown in (D). Furthermore, this third intermediate material 63 is extruded sideways to form an outward flange portion 33, and further processed to form the inner ring raceway 36a, to obtain a hub axle 31 as shown in (E).

As shown in FIG. 5, the cold forging device 50 for cold lateral extrusion includes a lower die 51, which is a fixed die, a cylindrical mandrel 57 fixed together with the lower die 51 inside the lower die 51, an upper die 52, which is a movable die, a ring punch 53 and a pressing punch 54 slidably fitted into the upper die 52, and an extrusion punch 55 slidably fitted into the lower die 51. These dies and punches form flange forming cavities 56 for forming the outward flange portion 33, which extend radially outward in the radial direction.

In the lateral extrusion molding by the cold forging device 50 described above, the third intermediate material 63 in FIG. 4(D) is placed in the cold forging device 50, and then, with the lower die 51 and the upper die 52 closed, the axial upper end of the third intermediate material 63 is crushed from above by the ring punch 53 and the pressing punch 54, causing the third intermediate material 63 to flow into the flange molding cavity 56. That is, the third intermediate material 63 is extruded into the flange molding cavity 56. As a result, the outward flange portion 33 is molded integrally with the hub axle 31. The shape of the dovetail groove 41 of the outward flange portion 33 is formed by the upper surface of the lower die 51 and the lower surface of the upper die 52, which form the flange molding cavity 56. Cold lateral extrusion is also described in detail in JP 2013-23086 A.

As described above, according to the hub flange 38 of this embodiment, a reinforcing member 40 is disposed between the outward flange portions 33, flush with the outward flange portions 33, and engages with the circumferential side surface 33b of the outward flange portions 33, thereby providing the hub flange 38 with circumferential and axial rigidity close to that of a round flange while reducing weight. This improves handling stability and reduces stress at the attachment portions of the wheel and brake rotor.

(Modification)
6 shows a modified example of a recess formed on the circumferential side surface 33b of the outward flange portion 33 and a protrusion formed on the circumferential side surface 40a of the reinforcing member 40. A T-shaped groove 43, which is a recess, is formed on the circumferential side surface 33b of the outward flange portion 33, and the reinforcing member 40 is die-cast or molded into the T-shaped groove 43 to form a protrusion 44, which is a protrusion with a T-shaped cross section. As a result, at least a portion of the tip 44a of the protrusion 44 and the circumferential side surface 33b of the outward flange portion 33 overlap when viewed from the circumferential direction, so that the T-shaped groove 43 and the protrusion 44 with a T-shaped cross section are firmly engaged with each other.
In this case too, the reinforcing member 40 is pulled circumferentially due to molding shrinkage of the reinforcing member 40, and a force toward the center of the hub axle 31 is applied, so that the reinforcing member 40 does not come off the outward flange portion 33, and the hub flange 38 can be given circumferential and axial rigidity similar to that of a round flange.

Figure 7 shows another modified example in which a convex portion is formed on the circumferential side surface 33b of the outward flange portion 33. In Figure 7(a), a protrusion 42, which is a convex portion with a V-shaped cross section, is formed on the circumferential side surface 33b of the outward flange portion 33, and the circumferential side surface 40a of the reinforcing member 40 is die-cast or molded to the protrusion 42 to form a dovetail groove 41, which is a recess with an inverted V-shaped cross section.

In addition, in FIG. 7(b), a protrusion 44, which is a convex portion with a T-shaped cross section, is formed on the circumferential side surface 33b of the outward flange portion 33, and a T-shaped groove 43, which is a concave portion, is formed on the circumferential side surface 40a of the reinforcing member 40.

In the case of the outward flange portion 33 shown in Figures 7(a) and 7(b), in which convex portions (ridge portions 42, 44) are formed on the circumferential side surface 33b, it can be formed not only by cold forging (cold lateral extrusion) but also by hot forging. However, in the case of the outward flange portion 33 shown in Figures 3 and 6, in which concave portions (dovetail groove 41, T-shaped groove 43) are formed on the circumferential side surface 33b, it is difficult to form it by hot forging. In other words, in hot forging, the die is moved in the axial direction of the hub axle to crush the upset billet in the axial direction to protrude the outward flange portion, so it is difficult to machine a concave portion on the circumferential side surface 33b of the outward flange portion 33.

In addition, with hot forging, the outward flange portion 33 can have not only a shape with a constant circumferential width (see FIG. 2), but also a tapered shape that gradually becomes narrower toward the outside in the radial direction (see FIG. 8). Hot forging makes molding easy and reduces manufacturing costs.

In any of the above-mentioned modified examples, at least a portion of the tip of the protrusion 42 overlaps, as viewed from the circumferential direction, with the circumferential side surface 33b of the outward flange portion 33 in which the recess is formed or the circumferential side surface 40a of the reinforcing member 40, so that the dovetail groove 41 and the protrusion 42, and the T-groove 43 and the protrusion 44 are firmly engaged, providing the hub flange 38 with circumferential and axial rigidity close to that of a round flange.

Second Embodiment
A hub unit bearing according to a second embodiment of the present invention will be described with reference to FIGS.
In the hub unit bearing 10 of this embodiment, the hub axle 31 is formed by hot forging (semi-closed forging), and flash 33c is generated on the circumferential side surface 33b of the outward flange portion 33. The flash 33c is utilized as a protrusion to which the reinforcing member 40 is fixed.

That is, when the hub axle 31 is formed by hot forging (semi-closed forging), the flash 33c generated on the outboard side of the circumferential side surface 33b of the outward flange portion 33 is trimmed leaving a certain amount, and then the remaining flash 33c is inclined in the axial direction by stamping (see, for example, JP 2012-215269 A) or rolling, specifically, is bent to tilt toward the inboard side, and the reinforcing member 40 is die-cast or molded to engage with the flash 33c. Therefore, a recess is formed on the circumferential side surface of the reinforcing member 40 so as to engage with the flash 33c.

The hub axle 31 of this embodiment is formed by hot forging, so the shape of the outward flange portion 33 as viewed in the axial direction is tapered so that the circumferential width gradually narrows as it moves radially outward, but it can be formed into any shape, such as a rod shape with a constant circumferential width.

Figure 10 shows an example in which the flash 33c is formed in the axial middle of the circumferential side surface 33b of the outward flange portion 33. In this case as well, the remaining flash 33c after trimming is pressed inboard by stamping or rolling, and the reinforcing member 40 is die-cast or molded to engage with the flash 33c.

In the hub unit bearing 10 of this embodiment, at least a portion of the tip of the flash 33c overlaps, as viewed from the circumferential direction, with the circumferential side surface 40a of the reinforcing member 40. As a result, molding shrinkage of the reinforcing member 40 causes the reinforcing member 40 to be pulled in the circumferential direction and a force toward the center of the hub axle 31 is applied, so that the hub flange 38 can be given circumferential and axial rigidity similar to that of a round flange, resulting in improved handling and reduced stress at the attachment portions of the wheel and brake rotor.
The other effects and actions are similar to those of the first embodiment.

The present invention is not limited to the above-described embodiment and modifications, and can be modified and improved as appropriate.
For example, in the illustrated embodiment, the dovetail groove or T-shaped groove is formed in one location, but it may be provided in multiple locations.
Also, although the inboard side surface of the hub flange is flush with the outboard flange portion and the reinforcing member, the reinforcing member may be made thinner than the outboard flange portion and the inboard side surface of the reinforcing member may be recessed from the inboard side surface of the outboard flange portion, forming a so-called scalloped flange.Also, the outboard side surface of the hub flange may also be made thinner than the outboard flange portion and the side surface of the reinforcing member may be recessed from the side surface of the outboard flange portion, provided that there is a sufficient contact area with the mounting portion of the brake rotor.

As described above, the present specification discloses the following:
(1) an outer ring member having a double row outer ring raceway on an inner circumferential surface;
an inner ring member having a double row inner ring raceway on its outer circumferential surface and a hub flange on one axial side to which a wheel and a brake rotor are attached;
A plurality of rolling elements rollably disposed between the double row outer ring raceways and the double row inner ring raceways;
A hub unit bearing comprising:
the inner ring member includes a hub axle having a plurality of radially extending outward flange portions spaced apart in the circumferential direction, and a plurality of reinforcing members made of a material lighter than the hub axle, the reinforcing members being respectively disposed between circumferential side surfaces of the outward flange portions adjacent in the circumferential direction and cooperating with the plurality of outward flange portions to form the disk-shaped hub flange,
a circumferential side surface of the outward flange portion and a circumferential side surface of the reinforcing member are connected to each other by a convex portion formed on one of the circumferential side surfaces engaging with a concave portion formed on the other circumferential side surface,
Hub unit bearing.
With this configuration, it is possible to provide the hub flange with circumferential and axial rigidity similar to that of a round flange while still achieving a lightweight design, improving handling stability and reducing stress in the attachment points of the wheel and brake rotor.

(2) The hub unit bearing according to (1), wherein at least a portion of the tip end of the protrusion and the other circumferential side surface overlap when viewed in the circumferential direction.
According to this configuration, the outward flange portion and the reinforcing member can be firmly engaged with each other.

(3) The recess is a dovetail groove or a T-groove having an inverted V-shape in cross section,
The hub unit bearing according to (1), wherein the convex portion is a protruding portion having a V-shaped or T-shaped cross section that engages with the dovetail groove or the T-shaped groove.
With this configuration, the outward flange portion and the reinforcing member can be firmly engaged with each other using a dovetail groove and a V-shaped protrusion portion, or a T-groove and a T-shaped protrusion portion, thereby providing the hub flange with circumferential and axial rigidity similar to that of a round flange while achieving weight reduction.

(4) The convex portion is a flash formed on a circumferential side surface of the outward flange portion during molding of the inner ring member, and is bent so as to be inclined in the axial direction.
The hub unit bearing according to (1).
According to this configuration, the flash formed on the circumferential side surface of the outward flange portion during molding of the inner ring member can be utilized as a protrusion that engages with the reinforcing member, thereby reducing manufacturing costs.

10 Hub unit bearing 11 Rolling element 20 Outer ring member 23a, 23b Outer ring raceway 30 Inner ring member 31 Hub shaft 33 Outward flange portion 33b Circumferential side surface 33c Flash 34 Cylindrical portion 36a, 36b Inner ring raceway 38 Hub flange 40 Reinforcing member 40a Circumferential side surface 41 Dovetail groove (recess)
42, 44 Protrusions (convex portions)
43 T-groove (recess)

Claims (4)

an outer ring member having a double row outer ring raceway on an inner circumferential surface thereof;
an inner ring member having a double row inner ring raceway on its outer circumferential surface and a hub flange on one axial side to which a wheel and a brake rotor are attached;
A plurality of rolling elements rollably disposed between the double row outer ring raceways and the double row inner ring raceways;
A hub unit bearing comprising:
the inner ring member includes a hub axle having a plurality of radially extending outward flange portions spaced apart in the circumferential direction, and a plurality of reinforcing members made of a material lighter than the hub axle, the reinforcing members being respectively disposed between circumferential side surfaces of the outward flange portions adjacent in the circumferential direction and cooperating with the plurality of outward flange portions to form the disk-shaped hub flange,
a circumferential side surface of the outward flange portion and a circumferential side surface of the reinforcing member are connected to each other by engaging a convex portion formed on one of the circumferential side surfaces with a concave portion formed on the other circumferential side surface.
Hub unit bearing. The hub unit bearing according to claim 1, wherein at least a portion of the tip of the protrusion and the other circumferential side surface overlap when viewed in the circumferential direction. The recess is a dovetail groove or a T-groove having an inverted V-shape in cross section,
2. The hub unit bearing according to claim 1, wherein said convex portion is a protruding portion having a V-shaped or T-shaped cross section that engages with said dovetail groove or said T-shaped groove. the protruding portion is a flash formed on a circumferential side surface of the outward flange portion during molding of the inner ring member, and is bent so as to be inclined in the axial direction.
The hub unit bearing according to claim 1 .

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