Brakes – Elements – Brake wheels
Reexamination Certificate
2000-04-26
2001-07-31
Schwartz, Christopher P. (Department: 3613)
Brakes
Elements
Brake wheels
Reexamination Certificate
active
06267210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a brake assembly including a hub and rotor. The brake assembly is particularly suited for application in a commercial vehicle.
2. Description of Related Art
Prior brake designs use a rotor fixed to a brake hub with fasteners or an integrated hub and rotor design. However, as the rotor is conventionally fixed with respect to the hub, the rotor must be carefully balanced to avoid uneven wear and compromised performance. Also, during braking, the rotor in such an assembly is subjected to high frictional forces that generate heat in the rotor causing thermal expansion/distortion, temperature variation across the face of the rotor, and heat transfer to the adjacent components including the hub and the fasteners. This is especially apparent in an integrated hub and rotor design.
When the rotor is fixed with respect to the hub, thermal expansion of the rotor is very limited because of the integral connection between the rotor and the hub. This creates thermal coning in the rotor surface and a large thermal gradient, which will induce high thermal stress leading to thermal cracking. The high thermal gradient generated during braking and the effects of the thermal expansion/distortion can cause vibration and thermal judder across the brake surfaces, resulting in a rough or irregular braking sensation. The high thermal stress and thermal distortion also reduce the life and performance of the rotor and increase maintenance costs.
Another problem associated with rotors connected to a hub, for example, a hat rotor that bolts onto a hub, is compound run-out. Referring to
FIG. 13
, this phenomenon is caused when a rotor surface
76
, which is not perfectly flat or parallel due to inherent imperfections created during manufacturing, is connected to a hub
72
, and the axes of rotation of the rotor
78
and the hub
72
are not in precise alignment. The potential run-out area in
FIG. 13
is shown at
70
. Misalignment results in poor rotor performance and durability.
Particularly in commercial braking applications, braking performance is especially stringent and closely monitored. It is important in such applications to provide a braking assembly that provides enhanced performance at low maintenance and replacement costs.
SUMMARY OF THE INVENTION
One aspect of the embodiments of the invention is to provide a braking assembly that is suitable for use on commercial vehicles, especially highway vehicles with a gross vehicle weight (GRW) of 5000 pounds or more and high performance vehicles.
Another aspect of the embodiments of the invention is to provide a rotor that floats with respect to the hub. This reduces the need for precise balancing due to float self balancing.
An additional aspect of the embodiments of the invention is to reduce first and second order thermal distortion by allowing the rotor to thermally expand. Embodiments of the invention provide a design that significantly reduces the temperature variation and thermal distortion across the rotor surface. This design can reduce thermal fatigue and prolong the life of the rotor.
The invention uses a floatation element with each fastener to allow the rotor to float or move with respect to the hub. The element can be made of a material resistant to corrosion and having low thermal conductivity so as to be viable for commercial highway vehicles.
The invention can reduce vibration and thermal judder across brake surfaces to ensure a smooth pedal feel during automobile or other vehicle braking applications.
A further aspect of the embodiments of the invention is to eliminate the compound run-out that is associated with the hub in a traditional integrated hub design.
Embodiments of the invention allow the rotor components to be family parts to reduce manufacturing tooling costs. The casting process can also be simplified, thus lowering costs and allowing improved quality control of castings.
Lower maintenance costs can be realized by tis invention by allowing replacement of the rotor without a hub change. Additionally, the hub and rotor can have different material specifications for optimal cost and performance.
These and other aspects and advantages of the invention can be realized by the various embodiments of the hub rotor assembly of the invention, which focuses on a brake hub and rotor assembly that uses a floatation element associated with a fastener to fasten the rotor to the hub while allowing the rotor to float relative to the hub. The rotor thus fastened is permitted to move in a limited manner with respect to the hub.
Other objects, aspects, and advantages of the embodiments of the invention will become apparent from the detailed description taken in conjunction with the drawings.
REFERENCES:
patent: 5190124 (1993-03-01), Haneda
patent: 5520269 (1996-05-01), Yamamoto et al.
patent: 5788026 (1998-08-01), Poli
patent: 6098764 (2000-08-01), Wirth et al.
Burgoon Donald L.
Killeen Sean E.
Qian Wenqi
Performance Friction Corporation
Pillsbury & Winthrop LLP
Schwartz Christopher P.
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