Wheel bearing unit for a vehicle, and method for manufacturing a wheel bearing unit
Patent Information
- Application Number
- EP2023818418
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-23
- Filing Date
- 2023-12-05
- Publication Date
- 2025-12-31
Smart Images
Figure EP2023084351_29082024_PF_FP_ABST
Abstract
Description
[0001] WHEEL BEARING UNIT FOR A VEHICLE AND METHOD FOR MANUFACTURING THE SAME
[0002] A WHEEL BEARING UNIT
[0003] DESCRIPTION:
[0004] 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. Furthermore, the invention relates to a vehicle with such a wheel bearing unit.
[0005] A generic wheel bearing unit comprises a wheel bearing with at least one inner ring, which is firmly seated on a bearing seat of a hollow cylindrical hub section of a wheel hub. The hub section of the wheel hub is connected in a torque-transmitting manner to a joint bell of a constant velocity joint of a vehicle's propeller shaft. For the torque-transmitting connection, the joint bell is extended outward in the vehicle's transverse direction by means of an axle journal that has a spline engagement with the inner circumference of the hollow cylindrical hub section of the wheel hub. Furthermore, the inner ring or rings of the wheel bearing are axially preloaded by the joint bell against an axial stop of the bearing seat of the hub section of the wheel hub. To simplify assembly, the spline engagement has a tooth clearance in the circumferential direction.
[0006] Particularly in electric vehicles with high torques during propulsion and recuperation, cracking noises occur when the direction of rotation of the drive shaft is reversed because the joint bell of the constant velocity joint (i.e. drive shaft outer joint) twists. This results in relative movement between the axle journal and the hub section. Accordingly, relative movement also occurs at the contact surfaces between the joint bell and the inner ring as well as between the inner ring and the hub, which generates cracking noises. In the state of the art, the generation of such cracking noises can be reduced by providing various measures: For example, axial gearing can be provided between one end face of the hub section and the joint bell. Such axial gearing requires more axial installation space, which has a negative impact on the vehicle's turning circle.In addition, the axial gearing is complex to manufacture, as it must be sealed and is more difficult to install (for example, in a tooth-on-tooth configuration). Alternatively, a sliding washer can be used on the contact surfaces. The use of such a sliding washer requires additional installation space and reduces the transmittable torque via frictional engagement, so the joint bell must be designed more robustly and heavier. As a further alternative, the wheel bearing can be lubricated or bonded in the area of the contact surfaces. This type of lubrication / bonding requires additional effort and creates contamination during production.
[0007] JP 2005308151 A discloses a wheel bearing unit for a vehicle. The wheel bearing unit is designed to prevent deterioration of durability due to corrosion and hydrogen embrittlement. US 2005 / 0254741 A1 discloses another wheel bearing unit in which an inner ring of the wheel bearing is coated with a thin layer. This layer comprises zinc flakes, a zinc-nickel coating, or a ceramic-based coating. The coating is applied using a dipping process.
[0008] The object of the invention is to provide a wheel bearing unit for a vehicle in which, compared to the prior art, noise generation during a reversal of the propeller shaft's rotation direction can be avoided in a structurally simple manner, particularly without negatively affecting the vehicle's turning circle. This object is achieved by the features of claim 1 or claim 8. Preferred developments of the invention are disclosed in the subclaims.
[0009] The invention is based on a wheel bearing unit whose wheel bearing has an outer ring that can be connected, for example, in a rotationally fixed manner to a wheel carrier, and at least one inner ring fixedly arranged on a bearing seat of a hollow cylindrical hub section of a wheel hub, with rolling elements rolling between the inner ring and outer ring. The hub section is connected in a torque-transmitting manner to a joint bell of a constant velocity joint of a propeller shaft of the vehicle. In addition, the joint bell axially preloads the inner ring against an axial stop of the bearing seat of the hub section of the wheel hub. According to the characterizing part of claim 1, the contact surfaces between the inner ring and the bearing seat and / or between the inner ring and the joint bell are coated with a static friction-reducing layer.In this way, cracking noises, particularly those caused by a stick-slip effect occurring at the contact surfaces, can be prevented when the direction of rotation of the drive shaft is reversed. Preferably, the inner ring, in particular, is coated with the static friction-reducing layer on its contact surfaces. In contrast, the contact surfaces at the bearing seat of the wheel hub and the joint bell can remain uncoated. Therefore, the wheel hub and the joint bell do not require an additional separate manufacturing step to be coated with the static friction-reducing layer.
[0010] The bearing seat consists of the axial stop, against which the inner ring is preloaded, and a radial seating area on the outer circumference of the hub section. To avoid cracking noises, it is advantageous if the contact surface between the inner ring and the axial stop and / or the contact surface between the inner ring and the radial seating area of the bearing seat and / or the contact surface between the inner ring and the joint bell are coated with the static friction-reducing layer. To facilitate torque transmission between the joint bell on the propeller shaft side and the wheel hub, the joint bell can be extended outward in the vehicle's transverse direction with an axle journal. This can be brought into force-transmitting spline engagement with the inner circumference of the hollow cylindrical hub section of the wheel hub.
[0011] If the direction of rotation of the propeller shaft is reversed, a stick-slip effect can occur, leading to cracking noises. Such a stick-slip effect results in relative movement between the joint bell and the hub section when a breakaway torque is reached, particularly due to torsion of the propeller shaft and / or residual play between the axle journal of the propeller shaft and the hub section. With the static friction-reducing layer according to the invention, a coefficient of friction at the contact surfaces can be adjusted, in particular reduced, to prevent cracking noises.
[0012] The axial preload of the inner ring against the bearing seat of the wheel hub can be achieved using a central screw. The central screw is inserted from the outside of the vehicle in the transverse direction into the hollow cylindrical hub section of the wheel hub, aligned with the wheel hub's axis of rotation, and can be screwed to an internal thread of the axle journal. The screw head of the central screw can be supported on the wheel hub from the outside of the vehicle, creating an axial interference fit consisting of the central screw, the wheel hub, the inner ring, and the axle journal including the joint bell. Alternatively, the axial preload of the inner ring against the bearing seat of the wheel hub can be achieved using a central nut, which is screwed to an external thread of the axle journal of the joint bell.
[0013] In a preferred embodiment, the static friction-reducing layer can be a thin layer, particularly with a layer thickness of less than 25 μm, to minimize installation space. When using such a thin layer, in contrast to the prior art (when using a sliding disk), no structural measures are required on a conventional wheel bearing unit to apply the static friction-reducing layer. To avoid impairing the functionality of the wheel bearing, it is preferred if the inner ring is coated only on the contact surfaces with the hub-side bearing seat and the joint bell. In contrast, the rolling element running surfaces and the seal seat can remain uncoated.
[0014] In a generic method for producing the wheel bearing assembly according to the invention, pre-processing steps can first be carried out in a process sequence, by means of which an inner ring blank is produced. Such pre-processing steps include, for example, forging, rolling, turning, heat treatment, precision turning, and grinding the inner ring end face and / or the inner ring inner circumference. In the further course of the process, the following process steps can be carried out: raceway grinding and honing of the rolling element raceways and the seal seat, and finally, bearing assembly, in which, among other things, the finished inner ring is mounted on the bearing seat of the hollow cylindrical hub section.
[0015] From a manufacturing perspective, it is advantageous if the static friction-reducing layer is applied during a coating process, preferably before raceway grinding and honing. In this case, the entire outer surface of the inner ring blank can first be coated with the static friction-reducing layer during the coating process. Subsequent raceway grinding and honing can then remove the static friction-reducing layer from the rolling element raceway, thereby preventing any functional impairment of the wheel bearing due to the applied layer. From a manufacturing perspective, the coating process can be a dipping process. The static friction-reducing layer can preferably be a zinc flake / zinc-nickel coating or a ceramic-based coating.
[0016] An embodiment of the invention is described below with reference to the accompanying figures. They show:
[0017] Fig. 1 shows a wheel bearing unit in a sectional view;
[0018] Fig. 2 and 3 Detailed views of an inner ring of the wheel bearing; and
[0019] Figures 4 and 5 show further embodiments of the invention.
[0020] 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, for example, on a wheel carrier. The wheel bearing 1 also has an inner ring 5, which is fixedly arranged on a bearing seat 7 of a hollow cylindrical hub section 9 of a wheel hub 11. The wheel bearing 1 is provided with two rows of balls 15 running in cages 13, each of which runs on an outer rolling track 17 directly on the outer circumference of the hollow cylindrical hub section 9 and on an inner rolling track 19 formed on the inner ring 5. The hollow cylindrical hub section 9 merges in the vehicle transverse direction y towards the outside of the vehicle into a widened wheel flange 20, to which a rim of the vehicle wheel and a brake disc can be mounted via wheel bolts.
[0021] According to Figure 1, a joint bell 21 of a propeller shaft (not shown) is extended outwardly from the vehicle by means of an axle journal 23 that projects into the hollow cylindrical hub section 9 and has a spline 25 on its inner circumference. The joint bell 21 is axially preloaded against an end face of the inner ring 5 by means of an indicated central screw 27. The central screw 27 is inserted from the outside of the vehicle in the vehicle transverse direction y into the hollow cylindrical hub section 9 of the wheel hub 11 and is screwed to an internal thread 29 of the axle journal 23, while its screw head is supported on the outside of the wheel hub 11. The bearing space between the outer ring flange 3 and the inner ring 5 or the outer circumference of the hollow cylindrical hub section 9 is sealed with an outer ring seal 16 and an inner ring seal 18. The inner ring seal 18 is supported on a sealing seat 20 of the inner ring 5.
[0022] As can be seen from Figure 1, the bearing seat 7 is formed from an axial stop 22, against which the inner ring 5 is axially preloaded, and from a radial seat area 32 on the outer circumference of the hub section 9.
[0023] In an electric vehicle with high torques during propulsion and recuperation, a reversal of the direction of rotation of the propeller shaft results in torsion of the joint bell 21. In the prior art, the reversal of the direction of rotation of the propeller shaft leads to a stick-slip effect that generates cracking noises. In the prior art, the stick-slip effect causes a relative movement between the joint bell 21 and the hub section 9 due to the torsion of the joint bell 21 and / or due to residual play. In the prior art, the cracking noises arise when a breakaway torque is exceeded at the contact surface between the joint bell 21 and the inner ring 5, or at the contact surface between the inner ring 5 and the radial seating area 32 of the bearing seat 7, or at the contact surface between the inner ring 5 and the axial stop 22 of the bearing seat 7.
[0024] Such cracking noises can be prevented according to the invention by the following measure: Thus, the inner ring 5 according to Figure 2 has a static friction-reducing layer 35 on its contact surface 31 with the joint bell 21, on its contact surface 33 with the radial seating area 32 of the bearing seat 7 and on its contact surface with the axial stop 22. By means of the static friction-reducing layer 35, a friction coefficient at the contact surfaces can be adjusted in order to prevent the cracking noises. As can also be seen from Figure 2, the inner ring 5 is only coated with the static friction-reducing layer 35 on its contact surfaces, while the inner rolling track 19 and the sealing seat 20 of the inner ring 5 are free of any coating. The static friction-reducing layer 35 is preferably a thin layer with a layer thickness s of less than 25 pm.The inner ring 5 according to the invention can preferably be manufactured according to the following process chain: First, pre-processing steps are carried out to produce an inner ring blank 37 (Figure 3), in particular forging, rolling, turning, heat treatment, precision turning, and grinding of the inner ring end face and / or the inner ring inner circumference. The inner ring blank 37 thus produced is then subjected to raceway grinding and honing to produce the rolling element outer raceway 19 and the seal seat 20. According to the invention, a coating process follows before the raceway grinding and honing, in which (for example, in a dipping process) the inner ring blank 37 is completely provided with the static friction-reducing layer 35, as shown in Figure 3.
[0025] After the coating process, the raceway grinding and honing of the inner rolling track 19 of the inner ring 5 is performed, whereby the layer 35 is removed from the inner rolling track 19 and also from the seal seat 20. The thus finished inner ring 5 is finally mounted in a bearing assembly on the bearing seat 7 of the hollow cylindrical hub section 9 of the wheel hub 11.
[0026] Figure 4 shows a second embodiment of the invention, the structure and mode of operation of which are essentially identical to the embodiment shown in Figures 1 to 3, so that reference can be made to the previous description. In contrast to the first embodiment, in Figure 4 the outer rolling track 17 is not formed directly on the outer circumference of the hollow cylindrical hub section 9, but rather on an inner ring 6, which is arranged together with the inner ring 5 on the bearing seat 7. In this case, the vehicle outer inner ring 6 forms the axial stop 22 for the vehicle inner inner ring 5.
[0027] Figure 5 shows a third embodiment of the invention, the structure and mode of operation of which are also largely identical to the embodiment shown in Figures 1 to 3, so that reference can again be made to its previous description. In contrast to the first embodiment, in Figure 5 the joint bell 21 is not axially preloaded against an end face of the inner ring 5 by means of a central screw 27. Rather, in Figure 5 the axial preload of the inner ring 5 against the axial stop 22 of the bearing seat 7 is achieved by means of a central nut 39, which is screwed to an external thread 41 of the axle journal 23 of the joint bell 21.
[0028] REFERENCE SYMBOL LIST:
[0029] I Wheel bearing
[0030] 3 Outer ring
[0031] 5 inner ring
[0032] 7 bearing seat
[0033] 9 hollow cylindrical hub section
[0034] II Wheel hub
[0035] 13 Cage
[0036] 15 balls
[0037] 16 outer ring seal
[0038] 17 Outer roller track
[0039] 18 inner ring seal
[0040] 19 Internal roller track
[0041] 20 Seal seat
[0042] 21 Joint bell
[0043] 22 Axial stop
[0044] 23 axle journals
[0045] 25 spline
[0046] 27 Central screw
[0047] 29 internal threads
[0048] 31 , contact surface
[0049] 32 radial seating area of the bearing seat 7
[0050] 33 Contact surface
[0051] 35 static friction reducing layer
[0052] 37 inner ring blank
[0053] 39 Central nut
[0054] 41 external thread s layer thickness
Claims
PATENT CLAIMS: 1 . Wheel bearing unit for a vehicle, comprising a wheel bearing (1) having at least one inner ring (5) fixedly arranged on a bearing seat (7) of a hollow cylindrical hub section (9) of a wheel hub (11), wherein the hub section (9) can be connected in a torque-transmitting manner to a joint bell (21) of a constant velocity joint of a propeller shaft of the vehicle, and wherein the joint bell (21) prestresses the inner ring (5) axially against the bearing seat (7) of the hub section (9) of the wheel hub (11), characterized in that contact surfaces (31, 33) between the inner ring (5) and the bearing seat (7) and / or between the inner ring (5) and the joint bell (21) are coated with a static friction-reducing layer (35), whereby, upon a reversal of the direction of rotation on the propeller shaft, cracking noises, in particular due to a friction generated at the contact surfaces (31, 33), the stick-slip effect can be prevented,and / or that in particular by means of the static friction-reducing layer (35) a friction coefficient at the contact surfaces (31, 33) can be adjusted in order to prevent the cracking noises.
2. Wheel bearing unit according to claim 1, characterized in that the inner ring (5) is coated on its contact surfaces (31, 33) with the static friction-reducing layer (35), while the bearing seat (7) of the wheel hub (11) and the joint bell (21) remain free of coating.
3. Wheel bearing unit according to claim 1 or 2, characterized in that for the torque-transmitting connection, the joint bell (21) is extended in the vehicle transverse direction (y) to the outside of the vehicle with an axle journal (23) which is in spline engagement (25) with the inner circumference of the hollow cylindrical hub section (9) of the wheel hub (11).
4. Wheel bearing unit according to claim 3, characterized in that when the direction of rotation is reversed, a relative movement occurs between the joint bell (21) and the hub section (9), in particular due to torsion of the cardan shaft and / or due to residual play between the axle journal (23) of the joint bell (24) and the hub section (9).
5. Wheel bearing unit according to one of the preceding claims, characterized in that the joint bell (21) can be axially preloaded against the inner ring (5) by means of a central screw (27), and that the central screw (27) can be screwed in the vehicle transverse direction (y) from the outside of the vehicle to an internal thread (29) of the axle journal (23) and can be supported with its screw head on the wheel hub (11), or that alternatively the axial preload of the inner ring (5) against the bearing seat (7) of the wheel hub takes place by means of a central nut (39) which can be screwed to an external thread (41) of the axle journal (23) of the joint bell (24).
6. Wheel bearing unit according to one of the preceding claims, characterized in that the static friction-reducing layer (35) is a thin layer with, in particular, a layer thickness (s) of less than 25 pm.
7. Wheel bearing unit according to one of the preceding claims, characterized in that the inner ring (5) is coated only on the contact surfaces (31, 33), while rolling element running surfaces (19) of the inner ring (5) are free of coating.
8. A method for producing a wheel bearing assembly according to one of the preceding claims, in which pre-processing steps for producing an inner ring blank (37) are carried out in a process sequence, in particular forging, rolling, turning, heat treatment, fine turning and grinding of the inner ring face and / or the inner ring inner circumference, and that the following process steps are carried out in the further course of the process: - Raceway grinding and honing of the rolling element raceway (19), and finally - Bearing assembly, in which, among other things, the inner ring (5) is mounted on the bearing seat (7) of the hollow cylindrical hub section (9).
9. Method according to claim 8, characterized in that before the raceway grinding and honing is carried out, a coating process is carried out in which the inner ring blank (37) is provided with the static friction-reducing layer (35), and that in particular during the raceway grinding and honing the layer (35) is removed from the rolling element raceway (19) and in particular from the seal seat (20).
10. The method according to claim 9, characterized in that the coating process is a dipping process, and / or that the static friction-reducing layer (35) is a zinc flake / zinc-nickel coating or a ceramic-based coating.