U.S. patent application number 11/517600 was filed with the patent office on 2007-04-19 for asymmetric hub assembly.
Invention is credited to Cengiz R. Shevket.
Application Number | 20070086687 11/517600 |
Document ID | / |
Family ID | 34594742 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070086687 |
Kind Code |
A1 |
Shevket; Cengiz R. |
April 19, 2007 |
Asymmetric hub assembly
Abstract
A hub bearing assembly comprising a hub having a radially
outwardly directed flange at one axial end for mounting the wheel
of a vehicle, an outer ring having axially spaced raceways and a
plurality of rolling elements arranged in two rows in the annular
space between the outer ring and the hub, the diameter of the pitch
circle of the outboard row of rolling elements adjacent said flange
being greater than the diameter of the pitch circle of the rolling
elements in the inboard row.
Inventors: |
Shevket; Cengiz R.; (Novi,
MI) |
Correspondence
Address: |
Eugene E. Renz, Jr., P.C.
205 North Monroe Street
Post Office Box 2056
Media
PA
19063-9056
US
|
Family ID: |
34594742 |
Appl. No.: |
11/517600 |
Filed: |
September 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10964013 |
Oct 13, 2004 |
7104695 |
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11517600 |
Sep 8, 2006 |
|
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60511004 |
Oct 14, 2003 |
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Current U.S.
Class: |
384/289 |
Current CPC
Class: |
B60B 27/00 20130101;
F16C 2240/80 20130101; F16C 2326/02 20130101; F16C 19/186 20130101;
F16C 19/497 20130101; F16C 41/02 20130101 |
Class at
Publication: |
384/289 |
International
Class: |
F16C 33/10 20060101
F16C033/10 |
Claims
1. A hub bearing assembly comprising a hub (12) rotational about an
axis (A-A) having a radially outwardly directed flange (16) at one
axial end for mounting the wheel of a vehicle, an outer ring (26)
having axially spaced raceways (22, 24) and a plurality of tapered
rollers arranged in two rows R.sub.i, R.sub.o in the annular space
between the outer ring (26) and the hub (12), the diameter Do of
the pitch circle of the outboard row R.sub.o of tapered rollers
adjacent said flange being greater than the diameter D.sub.i of the
pitch circle of the tapered rollers in the inboard row R.sub.i
wherein the contact angle of the inner and outer rows of rolling
elements intersect the rotational axis (A-A) of the hub (12) at
pressure centers P.sub.i and P.sub.o which lie outside the flange
(16) at the outboard end of the hub assembly and outside the hub at
the inboard side to provide enhanced performance including higher
load carrying capability and better distribution of the load on the
bearings.
2. A hub bearing assembly comprising a hub having a radially
outwardly directed flange at one axial end for mounting the wheel
of a vehicle, an outer ring having axially spaced raceways and a
plurality of rolling elements arranged in two rows in the annular
space between the outer ring and the hub, the diameter of the pitch
circle of the outboard row of rolling elements adjacent said flange
being greater than the diameter of the pitch circle of the rolling
elements in the inboard row wherein the contact angle of the inner
and outer rows of rolling elements intersect the rotational axis
(A-A) of the hub (12) at pressure centers P.sub.i and P.sub.o which
lie outside the flange (16) at the outboard end of the hub assembly
and outside the hub at the inboard side to provide enhanced
performance including higher load carrying capability and better
distribution of the load on the bearings
Description
[0001] This application is a Continuation of pending Shevket
application Ser. No 10/964,013 filed Oct. 13, 2004 and entitled
Asymmetric Hub Assembly. The parent Shevket et al application Ser.
No. 10/964,013 claims the benefit of Ser. No. 60/511,004 filed Oct.
14, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to improvements in hub units
for vehicles and more specifically to a novel asymmetric bearing
arrangement for rotatably supporting a wheel of a vehicle.
BACKGROUND OF THE INVENTION
[0003] Hub units for vehicle wheels are not new per se. Typical of
the prior are units are shown in patents such as the OSHIAKI, U.S.
Pat. No. 6,036,371 for ROLLING BEARING UNIT FOR VEHICLE WHEEL
issued Mar. 14, 2000 and the Evans, U.S. Pat. No. 4,333,695 for
ROLLING BEARING issued Jan. 8, 1982. As shown in these patents, the
hub units typically comprise a generally cylindrical hub having a
radially outwardly directed flange for mounting to a wheel of a
vehicle via a series of circumferentially spaced bolt holes
accommodating lugs or studs for supporting the wheel. A pair of
axially spaced rows of bearings support the wheel for rotation
between an outer ring having internal raceways for the rolling
elements. In the Yoshiaki '371 patent, the bearing support
comprises a row of balls and a row of tapered rollers.
[0004] Even though these hub assemblies are generally satisfactory
for the intended purpose, the present invention is an improvement
in hub assemblies of this general type and is characterized by
novel features of construction and arrangement providing functional
advantages over the prior art such as a more balanced load
distribution on the bearings and what is termed a "stiffer" hub
reducing bending moments particularly beneficial in cornering
maneuvers.
SUMMARY OF THE INVENTION
[0005] The present invention provides an asymmetric unit wherein
the diameterof the pitch circle of the bearing in the outboard row
adjacent the radial flange of the hub is of a greater diameter than
the diameter of the pitch circle of the bearing at the inboard end.
In a preferred embodiment of the invention, the inner and outer
rows of the bearings are angular contact ball bearings and the
diameter of the row at the outboard or wheel end is preferably at
least five mm greater than the diameter of the pitch circle of the
row at the inner suspension end. By this arrangement the distance
between the pressure centers where the contact angle of the two
bearing rows intercept the axis of the hub can be maximized to
provide high camber stiffness. Further the outboard row preferably
intercepts the hub axis outboard of the hub flange which balances
the loads on the system more evenly between the inner and outer
bearing rows. Additionally, by reason of the asymmetric design, the
outboard row can accommodate more balls and thereby increase the
capacity of the bearing without changing the package geometry. With
this design, the outboard pressure center can be placed further
outboard than a symmetrical unit without having to increase the
contact angle and reducing bearing radial dynamic capacity
[0006] In other words, comparing the symmetrical ball units of the
prior art with the asymmetrical unit of the present invention, the
asymmetric arrangement provides more capacity without impacting the
knuckle or axial flange geometry. Thus bearing designers can
utilize ball bearings in applications which would normally require
tapered bearings thus providing an economy without jeopardizing
performance.
As noted above, increasing hub stiffness by the asymmetric design
improves noise and vibration harshness, enhances steering accuracy
and vehicle dynamic behavior and also improves brake wear due to
true running of the rotors.
[0007] With the enhanced stiffness of the asymmetrical design, the
hub unit can accommodate large diameter wheels which apply a
heavier bending moment on the hubs. The asymmetric designs allows
wheel size increases without any changes in the hub design.
[0008] In summary, the present invention improves hub flange
strength and increases robustness and enhances safety of hubs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other objects of the present invention and the
various features and details of the operation and construction
thereof are hereinafter more fully set forth with reference to the
accompanying drawings, wherein;
[0010] FIG. 1. is a transverse sectional view of an asymmetric hub
assembly in accordance with the present invention;
[0011] FIG. 2. is a transverse sectional view of another embodiment
of asymmetric hub assembly in accordance with the present
invention;
[0012] FIG. 2a. is a view of still another embodiment of asymmetric
hub assembly in accordance with the present invention;
[0013] FIG. 3. is a transverse sectional view of an asymmetric hub
in accordance with the present invention showing balancing the
loads and a reduction in the radial load component on the outer row
as compared to the prior art symmetric arrangement;
[0014] FIG. 4. is a free body diagram comparing load distribution
for symmetric prior art system and the asymmetric hub assembly of
the present invention; and
[0015] FIG. 5. is a free body diagram comparing bending moment of
asymmetric hub design of the present invention verses prior art
asymmetric systems.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0016] Referring now to the drawings and particularly to FIG. 1
thereof, there is shown an asymmetric hub assembly in accordance
with the present invention generally designated by the numeral
(10). The hub assembly (10) includes an elongated hub (12) having a
splined center opening running axially of the hub (12) and having
at its outboard or wheel end a circumferentially extending radially
outwardly directed flange (16) having a series of circumferentially
spaced holes (18) to mount a wheel of a vehicle by means of studs
(20).
[0017] The hub assembly (10) has an outboard and an inboard row of
the ball bearings, Ro, Ri which ride on outer raceways (22), (24)
of an outer ring (26). The inner raceway (28) for the outboard row
Ro is formed integrally with the hub (12) and the inner raceway
(30) for the inboard row of ball bearings R.sub.i is formed on a
annular insert (32) held in place after assembly of the balls in
the two rows R.sub.o, R.sub.i by a circumferentially extending lip
(34) at the inner axial end of the hub (12). Conventional seals S
are provided at the opposing axial ends of the annular space
between the hub (12) and the outer ring (26). Further, the outer
ring (26) has means (27) at its inboard or suspension end for
securing it to a frame or steering mechanism of a vehicle. A sensor
(38) is also mounted in the outer ring (26) which confronts a
sensing ring (40) on the hub to measure speed of rotation in the
conventional way.
[0018] The present invention is characterized by novel features of
construction and arrangement providing an asymmetric bearing which
has functional advantages over the prior art. To this end, the
diameter D.sub.o of the pitch circle of the outboard row of balls
R.sub.o is preferably greater than the diameter D.sub.i of the
pitch circle of the inboard row of balls R.sub.i. The difference in
the diameters D.sub.o, D.sub.i is preferably at least five (5) mm.
Further, the contact angle .alpha. of the bearings intersect the
rotational axis A-A of the hub at points defined herein as pressure
centers P.sub.o, P.sub.i. The pressure centers P.sub.o, P.sub.i lie
outside the flange (16) at the outboard end of the hub assembly and
outside the hub (12) at the inboard end to provide enhanced
performance such as higher load carrying capability and better
distribution of the load on the bearings R.sub.o, R.sub.i. The
asymmetric hub assembly shown in FIG. 2a is generally similar to
that shown in FIG. 2 except that the rolling elements for both rows
R.sub.i and R.sub.o are tapered rollers.
[0019] FIG. 3 illustrates how road forces act on the pressure
centers P.sub.o, P.sub.i of an angular contact ball hub unit in
accordance with the present invention to provide improved load
distribution on the bearings R.sub.o, R.sub.i, and also to reduce
the bending moment arm on the outboard flange (16) of the
assembly.
[0020] As illustrated in FIG. 3, for a bearing arrangement wherein
the pitch diameters of the inner and outer rows R.sub.i, R.sub.o,
are the same the load force F.sub.r from the road tire interface is
acting outboard of the geometric center B-B of the bearing.
Accordingly, the distance from the point of application of the
force F.sub.r at the bearing axis A-A to the outboard pressure
center P.sub.o is a shorter distance than the distance to the
inboard pressure center P.sub.i and therefore the magnitude of the
vertical force F.sub.v2 acting on the outboard row of the outboard
bearing R.sub.o will be larger than that of the inboard force
F.sub.v1 based on a simple beam theory. By increasing the pitch
circle diameter D.sub.o of the outboard bearing R.sub.o without
changing the contact angle .varies. as illustrated in FIG. 3, the
distance to the force F.sub.v3 is increased thereby producing a
reduction of the magnitude of this force. Increasing the outboard
pitch circle diameter D.sub.o provides more room or space between
each of the balls so that the diameter increase of the outboard row
of balls R.sub.o produces a two fold improvement in life expectancy
on the outer row R.sub.o and additional load carrying capacity by
more rolling elements and a more balanced load distribution between
the bearings R.sub.o, R.sub.i. In most instances, the overall
geometry of the assembly is not impacted by increasing the pitch
diameter D.sub.o of the outboard row R.sub.o of rolling elements
since there is more radial space on the outboard side of the
bearing than on the inboard side mainly due to the knuckle and
brake geometry.
[0021] FIG. 5 is a free body diagram showing effect of the lateral
road force F.sub.a under cornering conditions on the bending moment
acting on the hub assembly. As can be seen in FIG. 5, the moment
arm L.sub.1 of a symmetric arrangement is greater than the moment
arm L.sub.2 of the asymmetric arrangement and by reason of this
difference, the moments about A which is a product of
F.sub.a.times.L.sub.1 is greater than the moment about B which is
F.sub.a.times.L.sub.2. Therefore, by reason of the moment arm
differential, the effective moment on the symmetric is higher and
thus the hub flange will yield more and adversely effect the
"stiffness" of the hub assembly.
[0022] A modified embodiment of asymmetric hub assembly in
accordance with the present invention is shown in FIG. 2. The hub
assembly generally designated by the numeral 10a is the same in
terms of components except in this instance, the inboard bearing
R.sub.i is a tapered roller bearing and is used in applications
where the predominant load is radial this arrangement can be used
where an existing taper roller bearing needs to be replaced without
having to change the knuckle diameter.
[0023] The invention provides improved performance in predominantly
radial load conditions such as in heavy truck applications which
typically utilize tapered rollers. The bearings incorporate the
same offset relationship of the inner and outer rows R.sub.i,
R.sub.o as described above and the intersection of the contact
angle .alpha. is preferably outward of the axial end of the hub.
The preferred asymmetric design utilizing balls in the outboard row
R.sub.o provides hub stiffness and structural strength improvement
without sacrificing load carrying capacity.
[0024] As noted above, in the symmetric design, the magnitude of
the vertical force acting on the outboard row designated F.sub.v2
is larger than the force F.sub.v1 on the inboard side which lowers
life expectancy of the outboard row R.sub.o. By increasing the
pitch circle diameter to produce an asymmetric design, the
beneficial effects are manyfold even without a change of the
contact angle .alpha.. As illustrated in FIG. 3, the magnitude of
the force is reduced (F.sub.v3), more room is created to
accommodate more balls further improving life expectancy and
producing further force reduction F.sub.y4.
[0025] In summary, benefits of the asymmetric design include high
camber stiffness providing improved brakewear, betterdriving
precision, optimized bearing capacity and life expectancy.
[0026] Even though particular embodiments of the present invention
have been illustrated and described herein, it is not intended to
limit the invention and changes and modifications may be made
therein within the scope of the following claims.
* * * * *