Brakes – Elements – Brake wheels
Reexamination Certificate
2002-04-25
2003-08-12
Schwartz, Christopher P. (Department: 3683)
Brakes
Elements
Brake wheels
Reexamination Certificate
active
06604613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a brake assembly including a hub and rotor.
2. Description of Related Art
Prior brake designs are hat rotor hubs that use a hat rotor fixed to a brake hub, or integrated rotor hubs.
Integrated rotor hubs, as the name suggests, are constructions that integrate a rotor and a hub into a single element. These integrated rotor hubs are typically manufactured by known metal manufacturing methods such as sand casting. The hub and rotor are typically integrally cast. Subsequent to casting, the integrated rotor hub must be machined. The manufacturing costs of integrated hubs are considerable, as different vehicles each require a unique integrated hub design. Therefore, separate tooling and specific machining processes are also required for each integrated hub design.
In addition to the relatively high manufacturing costs of integrated rotor hubs, are high replacement costs. For example, a worn or cracked braking surface on the rotor requires the replacement of the entire hub. Such hub replacements are costly due to high labor costs and high material costs in replacing the entire integrated hub and rotor. The replacement of an integrated rotor hub requires the re-packing or re-installation of bearing assemblies that allow the hub to rotate about a wheel shaft. The bearing re-packing or re-installation procedures are labor intensive and are occasionally poorly performed. Poorly re-packed or reinstalled bearings result in excessive wear in the hub, shaft, and bearing. Poorly re-packed or re-installed bearings also result in excessive rotor run-out.
Rotor run-out is the rotational misalignment of the rotor. Specifically, rotor run-out is the measurement of the extent to which the rotor wobbles, or deviates outside the intended plane of rotation, as the rotor rotates with the hub about the wheel shaft. Rotor run-out causes excessive and uneven wear in the rotor braking surfaces and in brake pads which contact the rotor braking surfaces. Rotor run-out also increases thermal distortion of the brake rotor. The thermal distortion results in thermal judder, noise, and vibrations during braking, as well as causing irregular braking pulsations.
Hat rotor hubs have a hat rotor that is detachable from a hub. These hat rotors are typically one piece metal castings having a rotor portion integrally cast with a hat portion. The hat portion of the hat rotor is a large flange that fits over a mounting surface of the hub. The hat portion includes wheel stud apertures through which wheel studs can pass. The hat rotor is loosely mounted on the hub until a wheel is subsequently mounted on the hub. As wheel lug nuts are tightened to the wheel studs, the hat rotor is sandwiched between the wheel and the hub, thus securing the hat rotor to the hub.
Hat rotor hubs have an advantage over integrated rotor hubs. Hat rotors can be easily replaced when the brake surfaces of the rotor become worn or cracked, or the rotor becomes warped. However, hat rotors also have deficiencies.
A deficiency with hat rotor hubs results from the configuration of the typical hat rotor hub design. Hat rotors and hubs are typically individual metal castings. Subsequent to casting, the hat rotor and the hub must both be individually machined. The machined surfaces of the rotor hat portion, the rotor braking surfaces, and the mounting surface of the hub must all be in the proper plane to minimize rotor run-out. The rotor braking surfaces extend outwardly a considerable distance from the rotor hat portion. Consequently, the rotor braking surfaces also extend outwardly a considerable distance from the mounting surface of the hub, where the rotor hat portion is mounted on the hub. Should the mounting surface of the hub, or the hat portion, include an imperfectly machined surface, the rotor will have considerable run-out as it rotates. Stated differently, a small error in the machined surfaces of the mounting surface, or the rotor hat portion, will have a proportionally magnified effect on the rotational alignment of the rotor braking surfaces due to the large distance the rotor braking surfaces extend from the mounting surface.
Another deficiency with hat rotor hubs results from the manner in which a hat rotor and a wheel are mounted together on the hub. The hat rotor is installed over a mounting surface of the hub. The hat rotor is loosely mounted on the hub until a wheel is subsequently mounted on the hub. As wheel lug nuts are tightened to the wheel studs, the hat rotor is sandwiched between the wheel and the hub, thus securing the hat rotor to the hub. However, if the wheel lug nuts are not evenly tightened, the uneven forces acting on the hub may result in the distortion of the hub. Additionally, if the wheel rim has been improperly manufactured, the wheel rim might impose a distortion on the hub as the lug nuts are tightened. Any distortion on the hub will be directly transferred to the rotor, as the portion of the hub that is potentially distorted is also the mounting surface for the rotor in all hat rotor designs.
Additionally, as the hat rotor is loosely held on the hub when the wheel is removed, debris such as brake pad material or dirt can slip between the rotor hat portion and the mounting surface when the wheel is removed from the hub. Extraneous material in this location will obviously prohibit the hat portion from mating properly with the mounting surface of the hub. Extraneous material will cause the rotor to run-out as it rotates about the wheel spindle.
Another deficiency of hat rotor hubs is the requirement of a specific hat rotor for every hub. Consequently, specific casting tooling and specific machining steps are typically required for each hat rotor hub design. The cost of hat rotors is increased as the tooling, casting, and machining costs are greatly increased due to the large number of hat rotors that must be manufactured. Inventory costs are also correspondingly increased.
FIG. 20A
is a partial side view in section of a prior art hat rotor hub assembly. Specifically,
FIG. 20A
shows a wheel shaft
1002
, a hub
1012
, which rotates about the wheel shaft
1002
through bearings
1009
a
and
1009
b,
a nut
1004
securing the hub
1012
to the wheel shaft
1012
, and a hat rotor
1018
that includes a hat portion
1030
and opposing braking surfaces
1040
and
1042
. The hub
1012
further includes a mounting surface
1013
and a plurality of wheel studs
1015
which extend outwardly from the mounting surface
1013
. The hat portion
1030
of the hat rotor
1018
includes a mounting surface
1032
which mates with the mounting surface
1013
. The hat portion
1030
also includes wheel stud passages
1034
through which the wheel studs
1015
pass. A wheel (not shown) is mounted on the hub outwardly of the hat portion
1030
. The wheel (not shown) would contact the exterior surface
1033
of the hat portion
1030
. A wheel lug nut (not shown) is used with each wheel stud
1015
to secure the wheel to the hub. Upon the securement of the wheel to the hub, the hat portion
1030
of the hat rotor
1018
is sandwiched between the wheel and the mounting surface
1013
. However, when the wheel is removed, as is shown in
FIG. 20A
, the hat rotor
1018
is loosely held on the hub
1012
.
The mounting of the wheel on the hub and the tightening of the lug nuts both may contribute to rotor run-out in this hub design. Both the rotor and the wheel are mounted at the same location on the hub (the mounting surface
1013
). Should the mounting surface become distorted, the rotor will subsequently also become distorted. Unevenly tightened lug nuts may distort the mounting surface
1013
. An improperly manufactured wheel rim (not shown) also could distort the hub mounting surface
1013
, as the rim is tightened onto the hub.
FIG. 20A
also shows the rotor braking surfaces
1040
and
1042
of the hat rotor
1018
are disposed at a considerable distance from the mounting surface
1013
on the hub
1012
. Consequently, the rotor brake surfaces
1040
and
104
Burgoon Donald L.
Killeen Sean E.
Qian Wenqi
Performance Friction Corporation
Schwartz Christopher P.
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