Vehicle wheel bearing unit and method for manufacturing wheel bearing unit

Abstract

The invention relates to a wheel bearing unit for a vehicle, comprising a wheel bearing (1) having at least one inner ring (5) which is fixedly mounted on a support (7) of a hollow cylindrical hub (9) of a hub (11), the hub (9) can be connected in a torque-transmitting manner to a joint bell (21) of a constant velocity joint of a joint shaft of a vehicle, the joint bell (21) axially pretensioning the inner ring (5) relative to a support (7) of the hub (9) of the hub (11). According to the invention, the contact surface (33) between the inner ring (5) and the bearing (7) and / or the contact surface (31) between the inner ring (5) and the universal joint bell (21) is coated with a coating (35) which reduces adhesion friction.

Description

Technical Field

[0001] The invention relates to a wheel bearing unit for a vehicle according to the preamble of claim 1 and to a method for producing such a wheel bearing unit according to claim 8. The invention also relates to a vehicle having such a wheel bearing unit. Background Art

[0002] A conventional wheel bearing unit comprises a wheel bearing with at least one inner ring fixedly mounted on a support in the hollow cylindrical hub of the wheel hub. The hub of the wheel hub is connected to the universal joint bell of the constant velocity joint of the vehicle's universal joint shaft in a torque-transmitting manner. To achieve this torque-transmitting connection, the universal joint bell extends outward in the vehicle's transverse direction via a journal that is splined to the inner circumference of the hollow cylindrical hub of the wheel hub. Furthermore, one or more inner rings of the wheel bearing are axially preloaded against the hub's support by an axial stop. To facilitate assembly, the splined connection has a circumferential clearance.

[0003] Especially in electric vehicles with high-torque drives and high-torque energy recovery, when the rotational direction of the universal joint shaft is reversed, the universal joint bell of the constant velocity joint (i.e., the outer universal joint of the drive shaft) twists, causing rattling noise. This causes relative movement between the shaft journal and the hub. Consequently, the contact surfaces between the universal joint bell and the inner ring, and between the inner ring and the wheel hub, also experience relative movement, causing rattling noise.

[0004] Various measures can be used to reduce this rattling noise in the prior art. For example, axial engagement can be provided between the end face of the hub and the joint bell. This axial engagement requires more axial installation space, which can negatively impact the vehicle's turning radius. Furthermore, axial engagement is complex to manufacture, as it must be sealed and installation is difficult (for example, in a tooth-on-tooth position). Alternatively, sliding plates can be used on the contact surfaces. These require additional installation space and reduce the transmittable torque due to the frictional connection, requiring a more durable and heavier design for the joint bell. Another alternative is to lubricate or bond the wheel bearings on the contact surfaces. This lubrication / bonding approach can result in additional production effort and contamination.

[0005] JP 2005308151 A discloses a wheel bearing unit for a vehicle. This wheel bearing unit is designed to prevent durability impairment due to corrosion and hydrogen embrittlement. US 2005 / 0254741 A1 discloses another wheel bearing unit in which the inner ring of the wheel bearing is coated with a thin layer. This thin layer comprises a zinc flake, zinc-nickel coating, or a ceramic-based coating. This coating is applied by a dip coating process. Summary of the Invention

[0006] The object of the present invention is to provide a wheel bearing unit for a vehicle which, compared to the prior art, can avoid noise generation when the direction of rotation of the cardan shaft is reversed in a structurally simpler manner and, in particular, does not negatively affect the turning radius of the vehicle.

[0007] This object is achieved by the features of claim 1 or claim 8. Preferred developments of the invention are disclosed in the dependent claims.

[0008] The present invention is based on a wheel bearing unit having, for example, an outer ring that can be connected to a wheel carrier / wheel support in a rotationally fixed manner, and at least one inner ring fixedly mounted on a seat in the hollow cylindrical hub of the wheel hub, with rolling elements rolling between the inner and outer rings. The hub is connected to the joint bell of a constant velocity joint of a vehicle's universal joint shaft in a torque-transmitting manner. Furthermore, the joint bell axially preloads the inner ring against an axial stop in the seat of the hub of the wheel hub. According to the characterizing portion of claim 1, the contact surfaces between the inner ring and the seat and / or between the inner ring and the joint bell are coated with a friction-reducing coating. This prevents rattling noises caused by stick-slip effects on the contact surfaces, particularly when the direction of rotation of the joint shaft is reversed. Preferably, the inner ring is coated with a friction-reducing coating on its contact surface. In contrast, the contact surfaces on the hub seat and the joint bell can remain uncoated. Therefore, it is not necessary to carry out an additional separate manufacturing step for applying the wheel hub and the universal joint bell with a coating that reduces traction friction.

[0009] The support / bearing seat comprises an axial stop and a radial mounting area / support area on the outer circumference of the hub, against which the inner ring is preloaded. To prevent rattling noises, it is advantageous if, in particular, the contact surfaces between the inner ring and the axial stop and / or the contact surfaces between the inner ring and the radial mounting area of the support and / or the contact surfaces between the inner ring and the joint bell are coated with a coating that reduces adhesion friction.

[0010] For easier torque transmission between the universal joint bell on the universal joint shaft side and the wheel hub, the universal joint bell can be extended outward in the transverse direction of the vehicle by a journal which can form a force-transmitting plug-in spline connection / plug-in engagement with the inner circumference of the hollow cylindrical hub of the wheel hub.

[0011] When the direction of rotation of the universal joint shaft is reversed, a stick-slip effect can occur, leading to rattling noises. In this stick-slip effect, relative movement occurs between the universal joint bell and the hub as the breakaway torque is reached, particularly due to torsion of the universal joint shaft and / or residual play between the journal of the universal joint shaft and the hub. The friction-reducing coating according to the invention can be used to adjust the coefficient of friction on the contact surface, in particular to reduce it, thereby preventing rattling noises.

[0012] Axial prestressing of the inner ring against its seat on the wheel hub can be achieved using a central bolt. This bolt is inserted from outside the vehicle into the hollow cylindrical hub of the wheel hub in the transverse direction of the vehicle, aligned / flush with the wheel hub's axis of rotation, and can be threaded into the internal thread of the shaft journal. The bolt head of the central bolt can be supported on the wheel hub from outside the vehicle, thereby achieving an axially compressed connection consisting of the central bolt, wheel hub, inner ring, and shaft journal, including the universal joint bell. Alternatively, axial prestressing of the inner ring against its seat on the wheel hub can be achieved using a central nut, which is threaded into the external thread of the shaft journal of the universal joint bell.

[0013] In a preferred embodiment, the friction-reducing coating can be a thin layer, preferably with a thickness of less than 25 microns, advantageous in terms of installation space. Compared to the prior art (when using sliding plates), the use of such a thin layer eliminates the need for structural modifications to conventional wheel bearing units to accommodate the friction-reducing coating. To ensure optimal functionality of the wheel bearing, the inner ring is preferably coated only on its contact surfaces with the hub-side support and with the joint bell. In contrast, the rolling surfaces of the rolling elements and the sealing seats can remain uncoated.

[0014] In this type of method for manufacturing a wheel bearing assembly according to the present invention, preprocessing steps can first be performed in a single process step to produce an inner ring blank. Such preprocessing steps may include, for example, forging, rolling, turning, heat treatment, finish turning, and grinding of the inner ring end face and / or inner circumference. Further steps may include grinding and honing of the rolling element and seal seat running surfaces, followed by bearing assembly, including mounting the completed inner ring on a support in a hollow cylindrical hub.

[0015] From a manufacturing perspective, it is advantageous to apply the friction-reducing coating during the coating process, preferably before rolling surface grinding and honing. In this case, the entire outer surface of the inner ring blank can be coated with the friction-reducing coating during the coating process. Subsequently, the friction-reducing coating can be removed from the rolling element rolling surfaces by subsequent rolling surface grinding and honing, thereby preventing the applied coating from affecting the function of the wheel bearing. From a manufacturing perspective, it is advantageous if the coating process can be a dip coating process. The friction-reducing coating can preferably be a zinc flake / zinc-nickel coating or a ceramic-based coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following describes an embodiment of the present invention based on the accompanying drawings.

[0017] Figure 1 showing a cross-sectional view of a wheel bearing unit;

[0018] Figure 2 and Figure 3 A detail view showing the inner race of a wheel bearing; and

[0019] Figure 4 and Figure 5 Other embodiments of the present invention are shown. DETAILED DESCRIPTION

[0020] exist Figure 1 shows a wheel bearing unit with a wheel bearing 1. The wheel bearing 1 has an outer ring flange 3, which can be mounted in a rotationally fixed manner on a wheel carrier / wheel support, for example. Furthermore, the wheel bearing 1 has an inner ring 5, which is fixedly mounted on a support 7 of the hollow cylindrical hub 9 of the wheel hub 11. The wheel bearing 1 is provided with two rows of balls 15 rolling in a cage 13. Each row of balls rolls on an outer running surface 17 located directly on the outer circumference of the hollow cylindrical hub 9 and on an inner running surface 19 formed on the inner ring 5. In the vehicle transverse direction y, facing outward, the hollow cylindrical hub 9 transitions into a widened rim flange 20, to which the rim of the vehicle wheel and the brake disc can be mounted via wheel bolts.

[0021] according to Figure 1The universal joint bell 21 of the (not shown) universal joint shaft is extended outward by a journal 23, which projects into the hollow cylindrical hub 9 and forms a plug-in spline connection 25 with the inner circumference of the hollow cylindrical hub. The universal joint bell 21 is axially preloaded against the end face of the inner ring 5 by a schematically illustrated central screw 27. Central screw 27 is inserted from the outside of the vehicle into the hollow cylindrical hub 9 of the wheel hub 11 in the transverse direction y of the vehicle and screwed into the internal thread 29 of journal 23. The head of the central screw is supported on the outside of the wheel hub 11. The bearing gap between the outer ring flange 3 and the inner ring 5 and the outer circumference of the hollow cylindrical hub 9 is sealed by an outer annular seal 16 and an inner annular seal 18. The inner annular seal 18 is supported on a sealing seat 20 of the inner ring 5.

[0022] like Figure 1 As further shown, the support 7 comprises an axial stop 22 and a radial mounting region 32 of the outer periphery of the hub 9 , against which the inner ring 5 is axially preloaded.

[0023] In electric vehicles with high-torque drives and high-torque energy recovery, the universal joint bell 21 twists when the rotational direction of the universal joint shaft is reversed. In the prior art, this reversal of the rotational direction of the universal joint shaft causes a stick-slip effect, which in turn generates rattling noises. In this stick-slip effect, relative movement occurs between the universal joint bell 21 and the hub 9 due to the twisting of the universal joint bell 21 and / or residual clearance. In the prior art, when the breakaway torque is exceeded, rattling noises occur at the contact surfaces between the universal joint bell 21 and the inner ring 5, at the contact surfaces between the inner ring 5 and the radial mounting area 32 of the support 7, or at the contact surfaces between the inner ring 5 and the axial stop 22 of the support 7.

[0024] According to the present invention, this rattling noise can be prevented by the following measures: Figure 2 As shown, the inner ring 5 has a friction-reducing coating 35 on its contact surface 31 with the joint bell 21, on its contact surface 33 with the radial mounting area 32 of the support 7, and on its contact surface with the axial stop 22. The friction-reducing coating 35 can adjust the friction coefficient on the contact surfaces to prevent rattling noises. Figure 2 As further shown, the inner ring 5 is coated with a friction-reducing coating 35 only on its contact surface, while the inner rolling surface 19 and the sealing seat 20 of the inner ring 5 remain uncoated. The friction-reducing coating 35 is preferably a thin layer with a coating thickness s of less than 25 micrometers.

[0025] Preferably, the inner ring 5 according to the present invention can be manufactured according to the following process chain: first, a pre-processing step of manufacturing the inner ring blank 37 is performed ( Figure 3), in particular forging, rolling, turning, heat treatment, finish turning, and grinding of the inner ring end face and / or inner ring inner circumference. The inner ring blank 37 thus produced is then subjected to rolling surface grinding and honing to produce the rolling element raceway 19 and the sealing seat 20. According to the present invention, a coating process is performed before the rolling surface grinding and honing, in which the inner ring blank 37 is completely coated with a coating 35 that reduces adhesion friction, such as a coating layer 35, such as a coating layer 35, is applied to the inner ring blank 37. Figure 3 shown.

[0026] After the coating process, the inner rolling surface 19 of the inner ring 5 is subjected to rolling surface grinding and honing, thereby removing the coating 35 on the inner rolling surface 19 and the sealing seat 20. Finally, the inner ring 5 thus completed is mounted on the seat 7 of the hollow cylindrical hub 9 of the wheel hub 11 during the bearing assembly process.

[0027] exist Figure 4 The second embodiment of the present invention is shown in FIG. 1 , and its structure and function are basically the same as those of FIG. Figures 1 to 3 The embodiment shown is identical to the embodiment shown, so reference can be made to the previous description. The difference from the first embodiment is that Figure 4 In the embodiment, the outer rolling surface 17 is not formed directly on the outer circumference of the hollow cylindrical hub 9, but on the inner ring 6, which is mounted together with the inner ring 5 on the support 7. In this case, the inner ring 6 on the outside of the vehicle thus forms an axial stop 22 for the inner ring 5 on the inside of the vehicle.

[0028] exist Figure 5 The third embodiment of the present invention is shown in FIG. Figures 1 to 3 The embodiment shown is basically the same, so reference can also be made to the previous description thereof. The difference from the first embodiment is that Figure 5 In the embodiment, the universal joint bell 21 is not axially preloaded relative to the end face of the inner ring 5 by the central bolt 27. Figure 5 In the embodiment, the inner ring 5 is axially preloaded relative to the axial stop surface 22 of the support 7 by means of a central nut 39 which is threadedly connected to the outer thread 41 of the journal 23 of the universal joint bell 21 .

[0029] List of reference numerals:

[0030] 1 Wheel bearing 3 Outer ring 5 Inner ring 7 Bearing 9 Hollow cylindrical hub 11 Wheel hub 13 Cage 15 Balls 16 Outer annular seal 17 Outer running surface 18 Inner annular seal 19 Inner running surface 20 Seal seat 21 Cardan joint bell 22 Axial stop 23 Axle journal 25 Plug-in spline connection 27 Central screw 29 Internal thread 31 Contact surface 32 Radial mounting area of bearing 7 33 Contact surface 35 Friction-reducing coating 37 Inner ring blank 39 Central nut 41 External thread s Coating thickness

Claims

1. A wheel bearing unit for a vehicle, comprising a wheel bearing (1) having at least one inner ring (5) fixedly arranged on a seat (7) of a hollow cylindrical hub (9) of a wheel hub (11), wherein: The hub (9) can be connected to a universal joint bell (21) of a constant velocity universal joint of a universal joint shaft of a vehicle in a torque-transmitting manner, wherein the universal joint bell (21) axially preloads the inner ring (5) relative to the support (7) of the hub (9) of the wheel hub (11), characterized in that the contact surface (33) between the inner ring (5) and the support (7) and / or the contact surface (31) between the inner ring (5) and the universal joint bell (21) is coated with a coating (35) that reduces adhesion friction, thereby preventing rattling noises, in particular due to stick-slip effects on the contact surfaces (31, 33) when the direction of rotation at the universal joint shaft is reversed, and / or the friction coefficient on the contact surfaces (31, 33) can be adjusted, in particular by means of the coating (35) that reduces adhesion friction, to prevent rattling noises.

2. The wheel bearing unit according to claim 1, characterized in that The inner ring (5) is coated on its contact surfaces (31, 33) with a coating (35) that reduces adhesion, while the support (7) of the hub (11) and the universal joint bell (21) remain uncoated.

3. The wheel bearing unit according to claim 1 or 2, characterized in that: In order to achieve a torque-transmitting connection, the universal joint bell (21) is extended outward in the vehicle transverse direction (y) by a journal (23) which is splined (25) with the inner circumference of the hollow cylindrical hub (9) of the wheel hub (11).

4. The wheel bearing unit according to claim 3, characterized in that When the direction of rotation is reversed, a relative movement occurs between the universal joint bell (21) and the hub (9), which is caused in particular by a twisting of the universal joint shaft and / or by a residual play between the journal (23) of the universal joint bell (24) and the hub (9).

5. The wheel bearing unit according to any one of the preceding claims, characterized in that The universal joint bell (21) can be axially preloaded relative to the inner ring (5) by means of a central bolt (27), which can be threadedly connected to the internal thread (29) of the journal (23) from outside the vehicle in the transverse direction (y) of the vehicle, the bolt head of the central bolt being supported on the wheel hub (11), or alternatively, the axial preload of the inner ring (5) relative to the support (7) of the wheel hub can be achieved by means of a central nut (39), which can be threadedly connected to the external thread (41) of the journal (23) of the universal joint bell (24).

6. The wheel bearing unit according to any one of the preceding claims, characterized in that The friction reducing coating (35) is a thin layer, in particular a thin layer having a coating thickness (s) of less than 25 microns.

7. The wheel bearing unit according to any one of the preceding claims, characterized in that The inner ring (5) is coated only on the contact surfaces (31, 33), while the rolling element running surface (19) of the inner ring (5) is uncoated.

8. A method for producing a wheel bearing arrangement according to any one of the preceding claims, wherein: In one process step, pre-processing steps for manufacturing the inner ring blank (37), in particular forging, rolling, turning, heat treatment, finish turning and grinding of the inner ring end face and / or inner ring inner circumference, are carried out, and in a further process step, the following steps are carried out: - rolling surface grinding and honing of the rolling element running surface (19), and finally - Bearing assembly, in which the inner ring (5) is mounted on a seat (7) of a hollow cylindrical hub (9).

9. The method according to claim 8, characterized in that Before the rolling surface grinding and honing, a coating process is carried out, in which the inner ring blank (37) is coated with a coating (35) that reduces adhesion friction. In particular, during the rolling surface grinding and honing process, the coating (35) is removed from the rolling surface (19) of the rolling element and, in particular, from the sealing seat (20).

10. The method according to claim 9, characterized in that The coating process is a dipping process, and / or the friction reducing coating (35) is a zinc flake / zinc nickel coating or a ceramic-based coating.

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