The invention relates to a wheel bearing unit having at least one outer part, at least one inner part and having at least two rows of rolling elements between the outer part and the inner part, on the outer part at least one inner raceway respectively being configured, and on the inner part at least one outer raceway for the rolling elements of a row respectively being configured.
Known wheel bearing units have a relatively high weight and a relatively low bearing stiffness. The bearing stiffness is here the resistance which the unit puts up against elastic deflections provoked by loads. From the bearing stiffness a tilt stiffness results, which derives from the ratio of load-generated moments to the tilt angle in the bearing, e.g. in Nm/°. The more the bearing tilts under loads, i.e. the greater is the tilt angle under equal load, the lesser is this tilt stiffness. The loads are the loads which essentially act upon a vehicle wheel and the associated wheel suspension in the running state of a vehicle. The lower the bearing stiffness, the more the loads induce tiltings of the wheel system, which adversely affect the driving characteristics of the vehicle, especially when cornering, and adversely affect brake wear and brake functioning.
The object of the invention is therefore to provide a wheel bearing unit having a high bearing stiffness.
The object has been achieved with the subject of the characterizing part of claim 1, in that the ratio of the pitch circle diameter TK of a row of rolling elements of the wheel bearing unit to the diameter dK of the rolling elements is greater than the numerical value 6. Thus:
TK>6·dK
on the following marginal conditions:
With the choice of the ratio, there is a departure from the opinion prevailing amongst experts that the dimensions of wheel bearing units must be chosen as small as possible. As a result of the larger rolling element pitch circle, and assuming the same static rated load C0 relative to a bearing of the prior art,
C0=f0·i·z·dK2·cos α0
yields a larger number of balls per row for the bearing according to the invention, especially if the ball diameter dK is chosen as small as possible, wherein:
fo=factor dependent upon the bearing construction
The stiffness is dependent upon factors such as the modulus of elasticity of the roller bearing material, the osculation of the raceway and, to a large degree, upon the number of rolling elements, as well as upon the diameter of the rolling elements. Thus, for example, for a bearing having a pitch circle diameter of TK=64 to 65 mm and for z=14 rolling elements with dK=12.7 mm in a bearing according to the prior art, a lower stiffness is obtained than an advantageously higher stiffness which is obtained for the wheel bearing unit according to the invention having the same pitch circle diameter and for z=21 with dK=11.112 mm.
The bearing stiffness, which is markedly increased as a result of the invention by about 40% relative to the prior art, leads to increased bearing tilt stiffness. The increased bearing tilt stiffness leads to lower load-dependent deformations on the wheel bearing unit and thus to lower deformations on the brake disks.
One embodiment of the invention provides that the row spacing rL between two axially adjoining rows (the axial center-to-center distance from rolling element center to rolling element center) corresponds to at least 1.22 times the diameter dK of the rolling elements. Thus:
rL>=1.22·dK
It is further provided that the axial bearing width bL of the outer part is at least three times the diameter of the smallest supporting rolling element of the wheel bearing unit. Thus:
bL>=3·dK
on the following marginal conditions:
Finally, with one embodiment of the invention, it is provided that the bearing cross section qL corresponds to at least 1.5 times the diameter of the smallest rolling elements of the wheel bearing unit. Thus:
qL>=1.5dK
on the following marginal conditions:
The points P1 and P2 here lie in a common radial plane E running through the centers of the rolling elements of one of the rows. The radial plane E runs through the row which produces the smallest radial distance DA. In the examples according to
A further embodiment of the invention provides for a wheel bearing unit having a wheel hub in that the diameter dz of the tip circle of the inner toothing corresponds at least to the dimension of the axial bearing width of the outer part. Thus:
dz>=1·bL
on the following marginal conditions:
Further embodiments of the invention are obtained by virtue of the ratios in column 8 according to table 1, below, quoted as minimum values, which ratios, up to the time at which the invention was made, are not realized on wheel bearing units of the prior art. The values are examples drawn from the characteristic values of an illustrative embodiment of the invention which are recorded in columns 1 to 7 according to line 2 and are designated in line 1.
All representations are in a longitudinal section along the rotation axes 1a and 4a of the wheel bearing units 1 and 4 respectively and are not to scale.
The inner toothing 3 on the wheel hub 2 is designed for engagement in an outer toothing of a drive journal (not represented). The wheel hub 2 is mounted rotatably in the outer part 8 and has a flange 9 for the fastening of a vehicle wheel (not represented) and of a brake disk. On the wheel hub 2 are seated the inner parts 10 in the form of inner rings 6 and 7, which respectively have an outer raceway 13 and 14 for the rolling contact with a respective row of rolling elements 11 in the form of balls. The rolling elements 11 of a row are guided in a cage 12. The outer part 8 replaces as a flange element the traditional outer ring(s) and has, for this purpose, the inner raceways 15 and 16 for the rolling contact with the rolling elements 11. The outer part 8 is provided with a flange 17 for the vehicle-sided fastening of the wheel bearing unit 1.
The wheel bearing unit 4 for non-driven wheels has a wheel hub 5 on which an inner raceway 18 for a row of rolling elements 11 is configured. On the wheel hub 5 is seated an inner ring 19 as the inner part 10, which has a further inner raceway 20 for further rolling elements 11. The outer part 21 of the wheel bearing unit 4 is configured in one piece with the inner raceways 22 and 23 and has a flange 24 for the vehicle-sided fastening.
Number | Date | Country | Kind |
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10 2004 055 786 | Nov 2004 | DE | national |
This application claims the benefit of the United States Provisional Patent Application No. 60/655,337 filed on 22 Feb. 2005 and German Application No. 10 2004 055 786.1, filed Nov. 18, 2004, the disclosures of which is hereby incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
4465326 | Guimbretiere | Aug 1984 | A |
4765688 | Hofmann et al. | Aug 1988 | A |
5114247 | Folino | May 1992 | A |
5458352 | Lederman | Oct 1995 | A |
5536098 | Schwarzler | Jul 1996 | A |
5975767 | Mizukoshi et al. | Nov 1999 | A |
6135571 | Mizukoshi et al. | Oct 2000 | A |
6428214 | Tajima et al. | Aug 2002 | B2 |
6497515 | Sahashi et al. | Dec 2002 | B1 |
6551190 | Hofmann et al. | Apr 2003 | B2 |
6626580 | Tajima et al. | Sep 2003 | B2 |
20030048967 | Sahashi et al. | Mar 2003 | A1 |
Number | Date | Country |
---|---|---|
4210461 | Oct 1993 | DE |
2246187 | Jan 1992 | GB |
Number | Date | Country | |
---|---|---|---|
20060120650 A1 | Jun 2006 | US |
Number | Date | Country | |
---|---|---|---|
60655337 | Feb 2005 | US |