Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Coil spring
Reexamination Certificate
2000-06-06
2001-09-11
Knight, Anthony (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Coil spring
C074S574300, C192S070170, C192S214100
Reexamination Certificate
active
06287205
ABSTRACT:
The present invention relates to a dual mass damping flywheel for coupling an internal combustion engine in rotation to a transmission system, in particular for a motor vehicle.
Such a dual mass double flywheel is described in the document FR-A-2 749 904. In this latter, a torque limiter is interposed operatively between a plate, constituting the reaction plate of a friction clutch, and an internal hub which is surrounded by the reaction plate.
The reaction plate and the hub are part of a secondary flywheel which is adapted, through a friction face of the reaction plate, to be coupled disengageably with a driven member of a transmission system, such as the input shaft of a gearbox of a motor vehicle.
The dual mass flywheel also comprises a primary flywheel which is arranged to be coupled in rotation to a driving shaft, such as the crankshaft of an internal combustion engine of a motor vehicle.
The secondary flywheel is mounted for rotation, by means of its hub, on the primary flywheel, which includes a generally transversely orientated element such as a plate which is parallel to the reaction plate of the secondary flywheel.
Resilient members are interposed operatively between the transverse element of the primary flywheel and the hub of the secondary flywheel so as to couple the secondary flywheel elastically to the primary flywheel.
The resilient members may consist of curved springs, in particular pre-curved springs, which act circumferentially between abutment elements fixed with respect to the primary flywheel and arms which are provided at the outer periphery of a disc which is fixed with respect to the hub of the secondary flywheel. The arms are disposed between two abutment elements of the primary flywheel, in facing relationship with each other.
In another version, the resilient members act radially in the rest position of the dual mass damping flywheel.
In the document FR-A-2 749 904, the torque limiter has a friction ring which is provided with outwardly aligned lugs which extend through apertures formed in a ring with axial elasticity, which is fixed with respect to the hub.
The friction ring defines the flank of a groove, the other flank of which, and the base of which, are part of the outer periphery of the hub. The reaction plate has at its inner periphery an internal ring portion which is centred by the base of the groove and which is pinched between the flanks of the groove. This arrangement gives satisfaction because it is of reduced axial size.
The internal ring portion therefore ensures a frictional coupling which is elastically preloaded, between the reaction plate and the internal hub which are thereby assembled together with the reaction plate.
The Applicant has enquired whether it would not be possible to make use of the internal ring portion without increasing axial size.
The object of the present invention is to respond in a simple and inexpensive way to this requirement. According to the invention, a dual mass flywheel of the type defined above is characterised in that the internal ring portion is carried on the reaction plate and is of a different material.
The assembly consisting of the reaction plate and the internal ring portion is thus made of two materials, constituting the outer part of the secondary flywheel.
The invention is characterised by the assembly of the internal ring portion with the reaction plate.
Thanks to the invention, while keeping the axial size small in the region of the torque limiter, it is possible to obtain different mechanical and kinematic characteristics in the external part and in the central part of the assembly that consists of the reaction plate and the internal ring portion.
The secondary flywheel, the external part of which constitutes the reaction plate, has good resistance to heat and is rigid enough to resist the axial and centrifugal forces which are exerted on it in operation.
The reaction plate is of a mouldable material having suitably adequate friction characteristics. It is preferably a casting so as to give it the desired inertia. In another version, it is aluminium based, which was not possible in the prior art, while the friction face which it presents for contact with the friction liner of a friction disc may consist of a layer which is fixed in any suitable way on the material of the reaction plate, with the desired coefficient of friction. All of this is made possible because the internal ring portion is of a different material from the reaction plate and may be given the desired thickness and mechanical strength. This ring portion enables the axial size to be small in the region of the torque limiter despite the stack of components at this point, and this is achieved with reduced weight since the ring portion is, preferably, of metal. It is for example made from steel sheet. The steel sheet is, in one embodiment, heat treated so as to give it the desired hardness. In another version, the steel sheet is coated with a wear-resistant layer. The internal ring portion may therefore have a complex form, as is called for because of its function.
In one embodiment, this ring portion is thinner than the ring portion of the prior art, and wears to a lesser extent than a ring which is cast, so that the useful life of the dual mass damping flywheel is increased. Preferably, the internal ring is thinner than the reaction plate. The reduction in thickness of the internal ring enables the axial size of the torque limiter to be reduced, or alternatively, for the same size, it enables its performance to be increased by giving the torque limiter several axially acting resilient rings.
This ring will easily absorb the stresses to which it is subjected. The ring may be made by press-forming, with, if necessary, a plurality of pieces being welded together and being of the metal specification most appropriate to its function. The assembly of the ring on the reaction plate may be obtained in any appropriate way, for example by in situ moulding of the reaction plate on the internal ring which has interruptions such as holes, or hooking projections, or, alternatively, by seaming of lugs of the ring on the reaction plate.
In one embodiment the ring has only one active face, which enables its axial size to be reduced even more. This face serves as a friction face for contact with another friction face that is mounted in rotation on the internal hub or on a component fixed to the latter. This arrangement also enables the internal hub to be simplified by reducing the consumption of material for the latter. A cage may be formed, which is bounded by the internal ring portion and a component fixed to the internal hub, the internal ring portion being closer to the primary flywheel and offset axially with respect to the radial axis of symmetry of the reaction plate, towards the primary flywheel. The axially acting resilient means of the torque limiter are lodged within this cage. This is made possible because, in the way described above, the internal ring portion can be given the desired form and the required length. This ring may therefore extend further down than the internal ring in the prior art, which enables the consumption of material for the internal hub to be reduced. In general terms, the coefficient of friction of the material of the reaction plate may be different from that of the material of the internal ring, which enables the functions of the internal ring and the reaction plate to be optimised, given that the internal ring may be coated with a layer, or even a friction liner, which enables its wear to be reduced and/or its coefficient of friction to be limited.
Within the above mentioned cage, there may be mounted axially acting resilient means in the form of at least one element of elastic material such as an elastomer. The component fixed to the internal hub serves, in one embodiment, to centre the reaction plate, being configured at its outer periphery so as to come into intimate contact with the inner periphery of the reaction plate. For example, this component has at its outer periphery an axially orientated
Bochot Jean-Claude
Bonfilio Ciriaco
Fenioux Daniel
Knight Anthony
Liniak Berenato Longacre & White
Thompson Kenn
Valeo
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