Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-12-03
2001-07-10
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C168S018000, C168S039001, C168S039001, C192S070190, C192S113210
Reexamination Certificate
active
06257376
ABSTRACT:
The present invention relates to a friction disk assembly, and more particularly to a friction assembly comprising a rotor disk interposed between two stator disks.
A particular intended field of application is that of brake, transmission, or retarder devices for motor vehicles, in particular heavy trucks.
Multidisk type brake devices made up of a plurality of stator disks alternating with rotor disks are well known. When such brake devices are installed on aircraft, the disks are now commonly made of a thermostructural composite material, and in particular of carbon/carbon (C/C) composite material. These materials have excellent mechanical properties and have the ability of conserving them up to high temperatures. In addition, they also provide very good friction behavior and a significant saving in mass compared with traditional metal disks.
Stator/rotor/stator (SRS) type disk brake devices using C/C composite materials have also been proposed for land vehicles, but until now use thereof has been limited to fields that are very special, for example Formula 1 motor racing. Reference can be made in particular to patent FR-A-2 655 397.
The saving in mass compared with metal disks and the performance of such devices encourage the idea of extending their use to other motor vehicles, in particular to heavy trucks, and not only for wheel brakes, but also for transmission brakes or “retarders”.
The problem which then arises, and which the present invention seeks to solve, is that of making mounting and thrust structures for the stator disks which not only have the mechanical strength necessary for taking up braking forces, but which also enable the heat that is generated by the friction to be evacuated effectively, and for this to be possible over a period of time that can be very long compared with that which occurs on aircraft where braking can be intense, but is of short duration. With disks that are made at least in part out of thermostructural composite material, another difficulty to be overcome lies in the difference between the coefficients of thermal expansion of said material and of the metal used for the disk mounting and thrust structure.
To this end, the present invention provides a friction assembly of the type comprising: first and second stator disks each having an outer thrust face and an inner friction face, and a rotor disk disposed between the stator disks and having two friction faces, the disks being made of thermostructural composite material at least in the wear portions thereof adjacent to the friction faces; first and second thrust structures respectively for the outer thrust faces of the stator disks; and an actuator device designed to act on at least one of the thrust structures to cause the disks to be urged together,
in which assembly, according to the invention:
the first thrust structure is bell-shaped, having an end wall portion against which the first stator disk bears and a skirt portion which is connected to the end wall portion and which surrounds the disks, the bell-shaped structure having cooling means to encourage evacuation of the heat produced by friction between the disks;
the second thrust structure has an annular plate-shaped thrust portion against which the second stator disk bears; and
the end wall portion of the bell-shaped structure and the thrust plate are provided with radial ribs or keys which co-operate with corresponding radial housings formed in the outer faces of the stator disks so as to prevent them from rotating relative to the thrust structures.
Thus, a characteristic of the friction assembly lies in the way in which the stator disks are prevented from moving relative to the keys or ribs of the thrust structures which co-operate with corresponding housings in the form of radial grooves formed in the outside faces of the rotor disks. As a result, differential expansion between the disks and the thrust structures can be compensated by relative axial displacement. In addition, the transfer of heat to the thrust structures can be minimized, and it is possible to reduce the size of the keys or ribs and the housings so as to leave sheets of air in the gaps between the keys or ribs at the outside faces of the disks, thereby favoring ventilation of the friction device.
Another characteristic of the friction assembly lies in making a thrust structure in the form of a bell provided with cooling means. The cooling means can be constituted by ventilation openings, e.g. in the form of slots formed in the skirt portion, and/or cooling fins, e.g. formed at the periphery of the skirt. The bell-shaped structure is advantageously made as a single casting, e.g. of cast iron, thus making it easy to give it the required mechanical properties.
The friction assembly may also have a support structure with a ring-shaped portion connected to the skirt portion of the bell-shaped thrust structure, said support structure advantageously being provided with ventilation openings.
Evacuation of the heat produced by the friction can also be facilitated by providing ventilation channels in the disks, at least in the rotor disks. These channels open out at the outer ring of the disk and can extend as far as the inner ring of the disk, or they can be in the form of blind holes. It is also possible to form channels that branch so as to ensure that the ratio between the mass of composite material and the heat exchange area remains uniform throughout the volume of the disk. In addition, at least one of the disks can be made up of a plurality of sectors.
REFERENCES:
patent: 4326614 (1982-04-01), Matagrano
patent: 5101940 (1992-04-01), Mungo et al.
patent: 5205380 (1993-04-01), Paquet et al.
patent: 5323881 (1994-06-01), Machan et al.
patent: 6029781 (2000-02-01), Carrier et al.
patent: 3740373 A1 (1988-06-01), None
patent: 37 40 373 (1988-06-01), None
patent: 44 38 456 (1996-05-01), None
patent: 1 324 457 (1963-07-01), None
patent: 2 655 397 (1991-06-01), None
patent: WO 97/20150 (1997-06-01), None
Borgeaud Olivier
Clement Didier
Messier-Bugatti
Oberleitner Robert J.
Siconolfi Robert A.
Weingarten, Schurgin Gagnebin & Hayes LLP
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