Brakes – Elements – Brake wheels
Reexamination Certificate
1998-06-30
2001-02-27
Butler, Douglas C. (Department: 3613)
Brakes
Elements
Brake wheels
Reexamination Certificate
active
06193027
ABSTRACT:
The invention at issue concerns a friction unit, in particular a brake disk, which shows at least a plane of friction with a friction body and with at least a molded body, where the friction body is build of carbon-fiber reinforced composite materials and is strongly joined together with the molded body.
A friction unit of this type is described in the DE-A1 44 38 456. This friction unit is identified by a core and at least one of these composite friction bodies, where the friction body and the core are fastened to the back side of the plane of friction. The blending of both parts is achieved by a high-temperature tolerance composite sheet. Preferably the composite sheet is made of silicon carbide. An essential problem on such brake disks, or rather brake disks in general, is the sufficient dispersion of the generated heat from the plane of friction. For this reason, the core of these brake disks has hollow spaces that allow sufficient cool air to be conducted to the insides of the friction part. As a result of the cooling channels and hollow spaces, a large surface is provided to convey the heat to the surrounding air. In a completed assembly, a space is kept between two friction parts through a core, built of planks, where a hollow space is created between the planks. The planks are set in the grooves of the inner side of the particular friction part inserted and held to the friction part.
Based on the above described state of the art, the invention at issue addresses the underlying object to further build a friction unit, in particular a brake disk, where the heat generated on the plane of friction is removed more effectively compared to known systems.
This objective is achieved by a friction unit according to the invention, in which at least one molded body is joined to the friction body so that at least a section becomes part of the plane of friction, and the molded body, in the perpendicular direction to surface, shows a higher heat transmission than the plane of friction itself.
In accordance with the teachings of the invention, which, for one, are comprised in that the molded bodies reach the surface of the plane of friction of the friction body, but also, in that the molded bodies show a preferred heat transmission direction, and, by these, the heat transmission direction is so oriented that, in essence, it is the direction that the perpendicular plane to the plane of friction extends, with the result, on account of defined heat gradients over these molded bodies, that the resulting heat generated in the plane of friction is removed to prevent a heat buildup on the plane of friction. The friction surface areas, which are not made of the particular molded body endings on the plane of friction, can be optimized based on the friction coefficients, so that the brake disks show good friction characteristics in these areas, and also exhibit a good removal of the heat through the molded bodies. This fast removal of the heat is particularly essential, since, with increased temperature on the friction surface, the friction characteristics of the friction unit are reduced significantly. In addition, locking can increase with increasing plane of friction temperatures, which can be minimized in accordance with the invented measures.
The molded bodies are mainly made of a carbon-fiber reinforced laminated material, that is, from a material specified or equal to the friction body. In the development of such a molded body the carbon-fibers are oriented in such way, in contrast to the building of the actual friction body, that at least 50% of the molded body carbon fibers are aligned longitudinal to the surface of the friction body, so that its longitudinal axis and the surface perpendicular to the plane of friction enclose a ≦45° angle; the carbon-fibers in the friction body should essentially run parallel to the friction surface. Preferably the angle between the perpendicular surface and the longitudinal axis of the fibers of the molded bodies amount to <30, but preferably maximum 10°; these fibers would in the ideal case wind up vertical to the friction surface or parallel to the surface perpendicular to the plane of friction. The proportion of fibers proceeding vertically to the surface, or rather, in the direction of the perpendicular surface comprise more than 75%; this proportion is preferably over 90%. In the ideal plate, the molded bodies are formed of fiber bundles, the fibers being arranged together in parallel and oriented in the direction perpendicular to, or at least extended to, the surface area of the plane of friction.
To obtain a stable structure with a good heat compartment, the molded bodies should extend through the entire thickness of the friction body. A multitude of molded bodies should be comprehended, which, as described above, are integrated into the friction body. These individual molded bodies are spaced equally from one another, so that between the surface of the molded bodies which end on the plane of friction, sufficient surface area and corresponding friction qualities are preserved. In such an arrangement of the molded bodies, bolt-like made molded bodies are preferred, which have a frontal surface ending in the plane of friction. Preferably the total of the frontal surface of the molded body on the plane of friction of a single molded body should be between 30 and 50% of the total surface of the plane of friction in the friction unit. The diameter of the bolts, or rather, for the diameter of the frontal surface of the molded bodies ending in the plane of friction, diameters of 10 up to 20 mm, preferable between 12 and 14 mm, are to be selected.
The molded bodies can be modified according to assembly, and insertion can protrude through the friction body, or rather, the friction unit, which has an additional advantage, in that the free surface of the molded body protruding through the plane of friction increases the cooling.
The bolt-like molded bodies can taper from the plane of friction to the plane of friction of the opposite surface. This means that such molded bodies, as viewed from the plane of friction, are set in tapered openings. Such an assembly has among others, the advantage that the molded bodies are also held in the friction body wedged under higher heat effects through the tapered, for instance, conical, cross section. As far as the gradation of cross section, if it widens or tapers, shoulders or impact surface can be made, which in turn guarantee a secure position or orientation to each other of the molded bodies and the friction bodies. From a finishing technician's view, the molded bodies show a somewhat round cross section. In such a cross section fiber, bundles can be compactly fastened, with an equal, radial distributed orientation.
As previously indicated, molded bodies are preferred such that a shoulder or fastening surface is shown. Two friction bodies can be spaced and jointly oriented with molded bodies made this way, so that the shoulder area of the molded bodies in relation to the friction body, which it supports, serves as a surface for placing of the backside of the opposite friction body on the friction surface. The area, or rather the hollow area formed between both friction bodies by the molded body can be used in such way, that, when the friction unit is turned a strong air circulation can be achieved in the hollow areas and heat can be removed therethrough.
To achieve the heat transfer to the surface of the molded bodies, which are in the middle reach of the respective molded bodies, which lies free between the space of both friction bodies, the carbon-fibers are arranged in such manner, that they are essentially arranged in a level perpendicular to the lengthwise direction of the fiber, which runs along the friction surface boundary, and thereby perpendicular to a cooling current. The course of the fibers are accordingly reverse-oriented from the friction surface to the free surface in the middle range of the molded bodies, so that an optimal heat drainage can be achieved, namely using a forward directio
Kochendorfer Richard
Krapf Jürgen
Krenkel Walter
Butler Douglas C.
Deutsches Zentrum fur Luft-und Raumfahrt e.V.
Fulbright & Jaworski LLP
Siconolfi Robert A.
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