192 clutches and power-stop control – Clutches – Axially engaging
Patent
1998-05-06
2000-01-25
Bonck, Rodney H.
192 clutches and power-stop control
Clutches
Axially engaging
192 8923, 192109A, F16D 1350
Patent
active
060168978
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to friction clutches with a low declutching force, especially for motor vehicles, and relates more particularly to the clutch mechanism which is included in such a clutch.
2. Description of the Related Art
As is known in a conventional clutch, a diaphragm interposed between a driving shaft and a driven shaft bears on the base of a cover plate, which is fixed to a rotary driving flywheel, so as to displace a pressure plate towards the said flywheel, which constitutes a reaction plate, in order that the friction liners of a clutch friction wheel shall be gripped between the pressure plate and reaction plate.
The driving flywheel is fixed to a first shaft, for example a driving shaft, while the clutch friction wheel has at its inner periphery a hub for mounting it in rotation on a second shaft such as a driven shaft.
The clutch is accordingly normally engaged with torque transmission between the driving and driven shafts.
In order to disengage (declutch) the clutch, it is necessary, with the aid of a clutch release bearing, to exert an annular thrust, in the case of a clutch of the push-to-release type, on the inner ends of the fingers of the diaphragm so as to cause the said diaphragm to pivot and overcome the force exerted by the diaphragm on the axially movable pressure plate, whereby to release the friction liners.
The torque is then no longer transmitted from the driving shaft to the driven shaft, because the friction liners are no longer gripped between the pressure plate and the reaction plate which are fixed to the cover plate in rotation.
Typically, the cover plate, the pressure plate and the diaphragm constitute a unitary assembly, referred to as a clutch mechanism, which can be fitted through its cover plate on the flywheel, with elastic tongues coupling the pressure plate to the cover plate for rotation with axial mobility.
As is known, the diaphragm has a central hole and includes an outer peripheral portion in the form of a Belleville ring which is extended internally by a central portion divided into radial fingers by slots. The diaphragm bears, through its Belleville ring portion, on the cover plate and on the pressure plate. Thus, the declutching means for the clutch, which enables the action of the resilient clutch engaging means to be counteracted at will, consists of the fingers of the diaphragm, on the inner ends of which the clutch release bearing acts, while the Belleville ring of the diaphragm constitutes axially acting resilient clutch engaging means for causing the friction liners to be gripped between the pressure plate and the reaction plate, and therefore for axially urging the pressure plate in a direction away from the base of the cover plate.
In the free state, the diaphragm is frusto-conical in form. Once it has been mounted in the clutch, its Belleville ring is mounted under prestress, and is flattened to a greater or lesser extent. During operation of the clutch (i.e. disengagement of the clutch), the cone angle of its Belleville ring is modified.
As is known, the characteristic curve of this diaphragm (with force exerted plotted against deflection), for example taken at the level of the inner ends of the fingers of the diaphragm, is determined by the dimensions of its Belleville ring and by the ratio between the depth of the frustum of the cone of the Belleville ring in the free state and the thickness of the diaphragm.
This characteristic curve passes through a maximum.
Thus, the force to be exerted on the inner ends of the fingers of the diaphragm increases to a maximum, diminishes gradually down to a minimum, and then rises again.
The difference between the maximum and the minimum may be large. For more detail as to this characteristic curve, reference should be made for example to the documents FR-A-1 392 569 or WO97/19275, and also to FIGS. 4 and 5 which show respectively the depth H of the frustum of the cone of a Belleville ring and the said curve, in which the load it exerts is expr
REFERENCES:
patent: 4236620 (1980-12-01), Beccaris
patent: 5400887 (1995-03-01), Mizukami et al.
patent: 5452783 (1995-09-01), Thirion de Briel et al.
patent: 5579881 (1996-12-01), Weidinger
patent: 5632365 (1997-05-01), Maucher
patent: 5794753 (1998-08-01), Kemper
patent: 5862901 (1999-01-01), Weiss et al.
Bonck Rodney H.
Valeo
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