Torque-damping anti-vibration device

Details Torque-damping anti-vibration device Torque-damping anti-vibration device

2000-04-06

2001-03-13

Schwartz, Christopher P. (Department: 3613)

Spring devices

Resilient shock or vibration absorber

Including energy absorbing means or feature

Reexamination Certificate

active

06199841

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to anti-vibration devices for damping torque.
More specifically, the invention relates to an anti-vibration device for damping torque, designed to couple an engine with a motor vehicle chassis with a view to limiting displacements of the engine in at least a first direction, this torque-damping device comprising:
first and second rigid reinforcements, which are designed to be fixed one to the engine and the other to the chassis, the second reinforcement defining a hollow interior space in which the first reinforcement is disposed with a certain amount of clearance in the first direction and in second and third directions perpendicular to one another and to said first direction,
a first elastomer limiting unit which is bonded onto the second reinforcement and inserted between the first and second reinforcements in order to restrict their relative displacement in the first direction, depending on a first direction corresponding to a displacement to which the engine is subjected when it produces a driving force, the first limiting unit having a first thickness of elastomer in the interior space of the second reinforcement as measured in the first direction,
and a second elastomer limiting unit which is bonded onto the second reinforcement and inserted between the first and second reinforcements in order to limit their relative displacement in the first direction, depending on a second direction opposite said first direction and corresponding to the displacement to which the engine is subjected when it produces a deceleration, the second limiting unit having a second thickness of elastomer in the interior space of the second reinforcement, measured in the first direction.
BACKGROUND OF THE INVENTION
In the known anti-vibration devices of this type, the first and second elastomer limiting units consist of two diametrically opposed arms which are joined at a central part moulded onto the first reinforcement.
These known anti-vibration devices have the following disadvantages, depending on how they are oriented relative to the displacement:
if the arms are working under a shearing action, the vibrations of the engine relative to the chassis are not appropriately filtered in the second direction (generally substantially vertical) because the anti-vibration device is of a relatively high rigidity in said second direction,
if one of the elastomer arms is working under compression, the other arm is then working in traction, which has a very adverse effect on the capacity of the elastomer to withstand fatigue.
Furthermore, since only a small volume is free for mounting the anti-vibration device, the elastomer arms are short and are therefore subjected to particularly high stress, which also has an adverse effect on the capacity of the coupling device to withstand fatigue.
OBJECTS AND SUMMARY OF THE INVENTION
The specific objective of the invention is to overcome these disadvantages.
To this end, the invention proposes an anti-vibration device of the type outlined above, essentially characterised in that:
the first reinforcement is of a substantially flat shape in the second and third directions,
the first reinforcement is simply inserted between the first and second elastomer limiting units, without any adhesion between the first reinforcement and said first and second limiting units,
and the first thickness of elastomer is greater than the second thickness of elastomer.
As a result of these features, each of the first and second limiting units works solely under compression which avoids the tensile stress detrimental to the capacity of the elastomer to withstand fatigue.
Furthermore, the first elastomer limiting unit, which is the one subjected to the greater stress, is also the one with the biggest elastomer thickness in the main direction of displacement, which makes the anti-vibration device more efficient.
Finally, the vibrations of the engine in the second direction are efficiently filtered, as are vibrations of the engine in the third direction, since the anti-vibration device is of a very low rigidity in these directions, due to:
the biasing of the rubber under shearing,
and the relatively large elastomer thickness of the first limiting unit against which the first reinforcement is supported for most of the time, which imparts quite good flexibility to this first limiting unit in the second and third directions.
It should be pointed out that the fact that the first reinforcement is not adhered in the second and third directions also makes it easier to accommodate mounting tolerances, particularly in the third direction.
In preferred embodiments of the invention, one and/or the other of the following features may optionally be incorporated:
the first reinforcement is inserted in a nest-fit between the first and second elastomer limiting units in contact with the first and second limiting units;
the first reinforcement is clamped between the first and second elastomer limiting units, thereby inducing an initial stress in the first and second limiting units in the first direction;
the second reinforcement is annular in shape, having an interior face which is lined with an elastomer body comprising the first and second limiting units;
the first limiting using consists of an elastomer lobe which projects into the interior space of the second reinforcement along a central axis parallel with the first direction;
the second limiting unit comprises second and third elastomer lobes which project into the interior space of the second reinforcement parallel with the first direction, opposite the first lobe, these second and third lobes being disposed on either side of the central axis of the first lobe, and the first reinforcement is designed in a shape similar to an arched tile with a concave aspect directed towards the first lobe;
the first reinforcement has a bore extending in the third direction which is designed to receive a bearing rod permanently jointed either to the engine or to the chassis, said first reinforcement forming a boss on a level with this bore which projects between the second and third elastomer lobes towards an elastomer stop moulded in a single piece with these second and third lobes and which is disposed in a recess between these lobes;
the first reinforcement is made by moulding and has stops which are directed in two opposite direction parallel with the third direction and which co-operate with at least one of the first and second elastomer limiting units in order to restrict relative displacements of the first and second reinforcements parallel with the third direction, these stops being offset from one another perpendicularly to said third direction so that, viewed in a projection parallel with this third direction, said stops do not overlap at any point which means that the first reinforcement can be moulded in a two-part mould and de-moulded parallel with the third direction;
the stops frame one of the first and second elastomer limiting units in order to restrict relative displacements of the first and second reinforcements parallel with the third direction;
the stops are disposed on two opposing faces belonging to the same reinforcement and co-operate one with the first elastomer limiting unit and the other with the second elastomer limiting unit in order to restrict relative displacements of the first and second reinforcements parallel with the third direction.
Another objective of the invention is a motor vehicle comprising an engine coupled with a chassis by at least one torque-damping device of the type defined above.


REFERENCES:
patent: 5031885 (1991-07-01), Schwerdt
patent: 42 15 195 (1993-11-01), None
patent: 0 258 103 (1988-03-01), None
patent: 0 371 194 (1990-06-01), None
patent: 05104922 (1993-04-01), None
patent: 08233006 (1996-09-01), None

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