WO2009040001A1 - Wheel bearing for a motor vehicle - Google Patents

Abstract

The invention relates to a wheel bearing (1) for a motor vehicle, particularly for a commercial vehicle, having a wheel bearing unit (2), which supports a wheel hub (3) on an steering knuckle (8) by means of rolling bearings (4, 5, 6, 7) acting axially and radially. In order to reduce the rolling friction to a minimum during the operation of the motor vehicle, the invention provides for the wheel hub (3) to be equipped directly or indirectly with two cylindrical raceways (9, 10) for cylinder rollers (11, 12), and with two raceways (15, 16) for balls (17, 18), placed on the front side in at least one radially extending annular section (13, 14), and for the steering knuckle (8) to be equipped directly or indirectly with two cylindrical raceways (19, 20) for the cylinder rollers (11, 12), and with two raceways (23, 24) for the balls (17, 18), placed on the front side in two radially extending annular sections (21, 22), wherein the cylinder rollers (11, 12) are disposed between the cylindrical raceways (9, 10, 19, 20), and the balls (17, 18) are disposed between the raceways (15, 16, 23, 24).

Description

 Description

Wheel bearing for a motor vehicle

The invention relates to a wheel bearing for a motor vehicle, in particular for a commercial vehicle, with a wheel bearing unit which supports a wheel hub by means of an axially and radially acting rolling bearing on a steering knuckle.

Tapered roller bearings, which are usually mounted in an O arrangement, are common for wheel bearings, in particular for commercial vehicle and trailer axles. Here, two tapered roller bearings are employed as far as possible without play or with slight preload in order to mount the wheel hub on the steering knuckle. The two tapered roller bearings thus serve as a combined radial and axial bearing.

It has also become known to use multi-row angular contact ball bearings for supporting a wheel hub, wherein up to four rows of bearings are arranged side by side. It is thus desirable to reduce the frictional torque or the power loss of the bearing in relation to said solution with two tapered roller bearings and thus to achieve a reduction in fuel consumption.

Also, said bearing arrangements with multiple angular contact ball bearings still have a considerable bearing friction, which entails a corresponding fuel consumption. There is therefore a need to Wheel bearing unit, which must store the hub radially and axially on the steering knuckle, so educate that even lower power loss can be achieved during operation.

The invention is therefore based on the invention, a wheel bearing for a motor vehicle of the type mentioned in such a way that a further reduced bearing friction during operation can be achieved, whereby the fuel consumption and thus the emission of pollutants can be reduced. At the same time, the rigidity of the storage should be improved.

The solution to this problem by the invention is characterized in that the wheel hub is provided directly or indirectly with two cylindrical raceways for cylindrical rollers and two in at least one radially extending annular portion frontally introduced raceways for balls and that the steering knuckle directly or indirectly with two cylindrical raceways for the cylindrical rollers and provided with two radially extending ring sections frontally introduced raceways for the balls, wherein between the cylindrical raceways, the cylindrical rollers and between the raceways, the balls are arranged.

The two cylindrical roller bearings are preferably arranged axially outboard and include the two ball bearings.

The rolling bearing is advantageously formed symmetrically to a perpendicular to the axis of rotation of the steering knuckle center plane.

The two cylindrical roller bearings can be made the same size. The two ball bearings can be made the same size. The cylindrical raceways of the two cylindrical roller bearings are preferably incorporated directly into the material of the wheel hub. The raceways for balls of the two ball bearings can also be incorporated directly into the material of the wheel hub in at least one radially extending ring section. Other solutions, for example, with pressed into a cast hub outer rings are also possible.

The bearing rings, which are mounted on the steering knuckle, may be L-shaped in radial section and have both a cylindrical raceway of the two cylindrical roller bearings and a raceway for balls of the two ball bearings. In this case, it has proven useful if the cylindrical raceway of the two cylindrical roller bearings of the bearing rings is bounded on both sides by one board. The two bearing rings can be kept at a defined axial distance by means of a spacer sleeve.

A further development provides that the two axial ends of the spacer sleeve are inserted in grooves in the two bearing inner rings, wherein there is a radial interference fit between the spacer sleeve and the bearing ring. This is achieved in an advantageous manner that results in a transport or assembly aid even without further components or elements, since the entire storage unit is then captive due to the non-positive holding effect of the press fit.

The wheel hub can have, as an integrally formed part, the two cylindrical raceways of the two cylindrical roller bearings and the two raceways for balls of the two ball bearings.

The wheel bearing unit is preferably designed as a preloaded and life-lubricated unit. It can be biased by means of an axle nut screwed onto the steering knuckle. The wheel bearing unit can be sealed from the environment by means of at least one sealing element.

To simplify the transport and / or assembly process, a sleeve may also be provided whose outer diameter corresponds to the inner bore of the wheel bearing unit and which is located temporarily in the preassembled wheel bearing unit. The sleeve is preferably made of plastic. It can be arranged with a press fit in the wheel bearing unit.

In accordance with the present invention, therefore, the radial and axial forces acting on the wheel and the tilting moments acting therefrom are absorbed by two cylindrical roller bearings and two axial ball bearings, which form a self-retaining bearing unit. The proposed embodiment allows a very low-friction power transmission between the hub and the steering knuckle and thus in vehicle operation a significant reduction in friction losses. At the same time an increase of the bearing stiffness is made possible by the separate recording of the radial and axial forces.

In the usual storage using tapered roller bearings acts because of the structural nature of the tapered roller bearing even when driving straight ahead of the vehicle, d. H. with pure radial load an axial force induced in both bearings, which in turn is partially supported by the roller end faces on the guide board of the two inner rings and is effective as sliding friction. The relatively high sliding friction between the roller end faces and the inner ring guide board occurs particularly strong in the low speed range in appearance.

In contrast, the proposed solution works in all driving conditions with pure rolling friction at a constantly low level. Consequently results for comparable operating forces a lower friction torque and consequently a lower steady-state temperature, which ultimately also positively affects the fat life. As a consequence of the lower operating temperatures, a higher kinematic lubricant viscosity is present, and thus, as a prerequisite for a long bearing life, reliable lubrication.

A sufficiently high torque stiffness of the bearing unit, which plays an important role especially in combination with disc brakes is ensured by the two cylindrical roller bearing sets with the design-related pressure angle (α = 0 °) and their sufficiently large distance to each other.

Previously known bearing arrangements for wheel bearings run mostly with a friction torque of up to 5 Nm, d. H. For a trailer with three axles, ie six wheel hubs, a total friction torque of approx. 30 Nm is calculated. With the proposed solution, this value can be significantly reduced.

Finally, the assembly of the unit is significantly simplified, since employment of the wheel bearing is basically eliminated. The assembly is limited to the sliding of the bearing unit on the steering knuckle and a distortion of the inner rings and the spacer sleeve by means of the axle nut with a defined torque.

The bearing unit is minimally preloaded after mounting on the steering knuckle and tightening the axle nut via the two thrust ball bearings. A slight axial preload only ensures that the balls are subjected to a minimum load in all load states to avoid sliding.

The proposed arrangement is further characterized by a lower wear. Lower heat generation advantageously results in lower lubricant aging and a longer storage life.

The proposed wheel bearing can be used on all commercial vehicle axles (trucks and trailer axles).

In the drawing, an embodiment of the invention is shown. The single figure shows the radial section through a wheel bearing of a truck or trailer.

In the figure, a wheel bearing 1 can be seen for a truck. The bearing of the (not shown) wheel is carried out with a wheel bearing unit 2, which consists of four rolling bearings 4, 5, 6 and 7. With the wheel bearing unit 2, a wheel hub 3 is mounted relative to a steering knuckle 8 of the vehicle axle. The stub axle 8 can - as in the embodiment - have a minimally stepped shaft, which is advantageous for the assembly of the wheel bearing unit.

The four antifriction bearings 4, 5, 6 and 7 are two cylindrical roller bearings 4 and 7 and two thrust ball bearings 5 and 6.

The cylindrical roller bearings 4, 7 have cylindrical raceways 9 and 10 of an outer ring, which in the present case is formed by the wheel hub 3 itself. The cylindrical raceways 19 and 20 are formed by bearing rings (inner rings) 27 and 28, which are placed on the steering knuckle 8. Between the cylindrical raceways 9, 10, 19, 20 cylindrical rollers 11 and 12 are arranged.

Axial between the two cylindrical roller bearings 4 and 7, the two thrust ball bearings 5 and 6 are positioned. The balls 17, 18 are arranged between each two annular or disc-shaped components, which have the corresponding raceways for the balls. For this purpose, the wheel hub 3 has one or two radially extending annular sections 13, 14, in each of the front side raceways 15, 16 are incorporated. The bearing rings 27 and 28 have a radial contour in an L-shaped contour, so that there is a radially extending annular portion 21 and 22, respectively, are incorporated into the respective raceways 23 and 24 respectively.

As can be seen, the entire wheel bearing unit 2 is formed with its four bearings 4, 5, 6, 7 symmetrical to a center plane 26 which is perpendicular to the axis of rotation 25 of the steering knuckle 8.

The cylindrical rollers 11, 12 transmit pure radial forces. For axial guidance of the cylindrical rollers, the inner rings 27, 28 on both sides edges 29 and 30 on the bearing ring 27 and 31 and 32 on the bearing ring 28. At the corresponding outer ring, the cylindrical track 9, 10 is not limited by ribs.

A spacer sleeve 33 holds the two bearing rings 27, 28 at a defined distance when an axle nut 34 is screwed onto the steering knuckle 8 during assembly of the wheel bearing unit. The width of the spacer sleeve is preferably to be chosen so that after tightening the axle nut, the two thrust ball bearings 5, 6 are slightly biased.

In addition, the spacer sleeve 33 also serve as a frictional connection element between the two inner rings 27 and 28. In this case, the sleeve sits over its outer diameter with coverage, d. H. with a press fit, in recesses 37, which are introduced into the inner rings 27 and 28. A captive unit is created, which has a positive effect on transport and installation.

A sealing element 35 in the form of a radial shaft seal provides a seal to the environment. The wheel bearing unit can optionally be sealed on both sides. The radial shaft sealing ring for the seal towards the inside of the wheel is thus to be understood as an example here.

The cylindrical roller bearing on the inside of the wheel can be made stronger than the arranged on the outside of the wheel cylindrical roller bearing because of the usually higher radial force acting there; however, this is by no means mandatory.

For economic reasons, the use of identical sets of rollers is preferred for the respective same bearings 4 and 7 or 5 and 6 respectively.

Particularly advantageous in steering knuckles without grading and at the same bore diameters of the inner rings providing a sleeve 36 (in the figure in addition to the steering knuckle 8 shown), which preferably consists of plastic and which allows a very simple installation. The pressed into the bore of the wheel bearing unit 2 sleeve 36 with its outer diameter D holds the storage unit together during transport. During the sliding of the bearing unit 2 on the steering knuckle 8, the sleeve 36 is simultaneously pushed out of the bearing bore.

Alternatively, to assist handling during transport and / or assembly, the mentioned solution may be used, whereafter the spacer sleeve 33 seats with moderate interference fit in the recesses 37 of the inner rings 27, 28 so that the two inner rings are held together in the axial direction.

The lubrication of the bearing unit is carried out with an application-optimized smooth running grease.

When driving straight ahead, the wheel force acting at the tire contact point becomes proportionate to the two according to the axial position of the wheel pressure line Cylindrical roller bearings added. The resulting from the camber axial force is absorbed by one of the two thrust ball bearings. Otherwise, the applied during assembly axial preload force acts in two rows of balls.

When cornering, the radial Radaufstandskraft corresponding to the axial position of the Raddrucklinie proportionately received by the two cylindrical roller bearings and the induced by the axial force and the dynamic tire radius tilting also supported over both cylindrical roller bearings. The axial force that arises at the wheel hub by the force acting on the vehicle centrifugal force is transmitted depending on the direction of force (inside or outside curve wheel) of the central housing disc on each loaded thrust ball bearing and passed over the "wave washer" of the respective inner ring in the steering knuckle.

When mounting the wheel bearing unit proceed as follows:

First, the wheel bearing unit is pushed over the end face of the outer cylindrical roller bearing inner ring. The inner rings are seated with a loose fit on the steering knuckle (recommended tolerance field: "f7") .The transport sleeve (sleeve 36) prevents the bearing components from being separated.The transport sleeve is pushed out when the bearing unit is pushed on.

Then, the central axle nut 34 is tightened to a previously specified tightening torque. The two inner rings 27, 28 and the intermediate sleeve (spacer sleeve) 33 are clamped together. The clamping force simultaneously secures the axle nut against loosening.

The radial clearance in the cylindrical roller bearings is preset and is very close to zero; a change during assembly is excluded by the loose fit of the inner ring. LIST OF REFERENCE NUMBERS

1 wheel bearing

2 wheel bearing unit

3 wheel hub

4 rolling bearing (cylindrical roller bearing)

5 rolling bearing (thrust ball bearing)

6 Rolling bearings (thrust ball bearings)

7 Rolling bearings (cylindrical roller bearings)

8 stub axles

9 cylindrical track

10 cylindrical track

1 1 cylindrical roller

12 cylindrical roller

13 ring section

14 ring section

15 career

16 career

17 ball

18 ball

19 cylindrical track

20 cylindrical track

21 ring section

22 ring section 23 career

24 career

25 axis of rotation

26 middle level

27 bearing ring

28 storage

29 board

30 board

31 board

32 board

33 spacer sleeve

34 axle nut

35 sealing element

36 sleeve

37 Turning

D diameter

Claims

P atentansprü e eRadlagerung for a motor vehicle 1. wheel bearing (1) for a motor vehicle, in particular for a commercial vehicle, with a wheel bearing unit (2) having a wheel hub (3) by means of an axially and radially acting roller bearing (4, 5, 6, 7) on a steering knuckle (8) superimposed, characterized in that the wheel hub (3) directly or indirectly with two cylindrical raceways (9, 10) for cylindrical rollers (11, 12) and with two in at least one radially extending annular portion (13, 14) frontally introduced raceways (15th , 16) for balls (17, 18) is provided and that the steering knuckle (8) directly or indirectly with two cylindrical Runningways (19, 20) for the cylindrical rollers (1 1, 12) and with two radially extending ring sections (21, 22) frontally introduced raceways (23, 24) for the balls (17, 18) is provided, wherein between the cylindrical raceways (9, 10, 19, 20), the cylindrical rollers (11, 12) and between the raceways (15, 16, 23, 24) the Balls (17, 18) are arranged. 2. wheel bearing according to claim 1, characterized in that the two cylindrical roller bearings (9, 11, 19, 10, 12, 20) are arranged axially outboard and the two ball bearings (15, 17, 23, 16, 18, 24) include. 3. wheel bearing according to claim 1 or 2, characterized in that the rolling bearing (4, 5, 6, 7) to a on the axis of rotation (25) of the stub axle (8) perpendicular center plane (26) is formed symmetrically. 4. Wheel bearing according to one of claims 1 to 3, characterized in that the two cylindrical roller bearings (9, 11, 19, 10, 12, 20) are of equal size. 5. Wheel bearing according to one of claims 1 to 4, characterized in that the two ball bearings (15, 17, 23, 16, 18, 24) are of equal size. 6. Wheel bearing according to one of claims 1 to 5, characterized in that the cylindrical raceways (9, 10) of the two cylindrical roller bearings (9, 11, 19, 10, 12, 20) are incorporated directly into the material of the wheel hub (3) , 7. Wheel bearing according to one of claims 1 to 6, characterized in that the raceways (15, 16) for balls (17, 18) of the two ball bearings (15, 17, 23, 16, 18, 24) directly into the material of Wheel hub (3) in at least one radially extending annular portion (13, 14) are incorporated. 8. wheel bearing according to one of claims 1 to 7, characterized in that the bearing rings (27, 28) which are placed on the steering knuckle (8) are formed in radial section L-shaped and both a cylindrical track (19, 20) The two cylindrical roller bearings (9, 11, 19, 10, 12, 20) and a raceway (23, 24) for balls (17, 18) of the two ball bearings (15, 17, 23, 16, 18, 24). 9. Wheel bearing according to claim 8, characterized in that the cylindrical raceway (19, 20) of the two cylindrical roller bearings (9, 11, 19, 10, 12, 20) of the bearing rings (27, 28) on both sides of a respective board (29 , 30, 31, 32) is limited. 10. Wheel bearing according to claim 8 or 9, characterized in that the two bearing rings (27, 28) by means of a spacer sleeve (33) are held at a defined axial distance. 1 1. Wheel bearing according to claim 10, characterized in that the two axial ends of the spacer sleeve (33) in recesses (38) in the two bearing rings (27, 28) are inserted, wherein between the spacer sleeve (33) and the bearing ring (27 , 28) a radial interference fit is present. 12. Wheel bearing according to one of claims 1 to 11, characterized in that the wheel hub (3) as an integrally formed part of the two cylindrical raceways (9, 10) of the two cylindrical roller bearings (9, 11, 19, 10, 12, 20) and the two raceways (15, 16) for balls (17, 18) of the two ball bearings (15, 17, 23, 16, 18, 24). 13. Wheel bearing according to one of claims 1 to 12, characterized in that the wheel bearing unit (2) is designed as a prestressed and life-lubricated unit. 14. Wheel bearing according to claim 13, characterized in that the wheel bearing unit (2) by means of a on the steering knuckle (3) screwed axle nut (34) is biased. 15. Wheel bearing according to one of claims 1 to 14, characterized in that the wheel bearing unit (2) relative to the environment by means of at least one sealing element (35) is sealed. 16. Wheel bearing according to one of claims 1 to 15, characterized by a sleeve (36) whose outer diameter (D) corresponds to the inner bore of the wheel bearing unit (2) and which is temporarily in the preassembled wheel bearing unit (2). 17. Wheel bearing according to claim 16, characterized in that the sleeve (36) consists of plastic. 18. Wheel bearing according to claim 16 or 17, characterized in that the sleeve (36) is arranged with a press fit in the wheel bearing unit (2).