192 clutches and power-stop control – Clutches – Plural clutch-assemblage
Reexamination Certificate
2000-03-20
2001-08-21
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Plural clutch-assemblage
C192S070270, C192S089220
Reexamination Certificate
active
06276504
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a twin clutch for motor-vehicle gearboxes having two clutch discs, each arranged on one of two coaxial shafts. A clutch cage surrounds the clutch discs in the manner of an annulus. Pressure plates are held in a rotationally fixed manner and are arranged axially in such a way that they can be displaced separately axially between the clutch discs. The pressure plates can be pressed against the clutch discs by a diaphragm-spring arrangement arranged axially between them and can be disengaged from the respective clutch disc by separate release members.
DESCRIPTION OF PRIOR DEVELOPMENT
Twin clutches are required in motor vehicles for two-path gearboxes which can be operated without interruption of the tractive effort. Gearboxes of this kind have two inputs which are coupled continuously in terms of drive via selectable transmission stages, which are generally different, to a common gearbox output which, for its part, is connected to the driven wheels of the vehicle. The twin clutch assigned to these two-path gearboxes has an input which is connected in terms of drive to the vehicle engine and, in the case of the twin clutch stated at the outset, is formed by the clutch cage. This clutch input can be coupled via two separately controllable clutches which, in the case of the abovementioned twin clutch, are formed by the clutch discs and the associated pressure plates, to the two gearbox inputs which are connected in terms of drive to mutually coaxial shafts.
In normal driving operation, one clutch is closed while the other clutch is open, with the engine and the driven wheels thus being connected to one another in terms of drive via one clutch and the gearbox path associated with this clutch. Within the other path of the gearbox, it is now possible to select, in principle, any drive ratio and this then takes effect when the other clutch is closed and the first clutch is opened.
It is advantageous that, by virtue of the diaphragm-spring arrangement arranged between the pressure plates, the closing force of one clutch is automatically increased when the other clutch is opened if the release members of the first clutch remain unactuated.
There is furthermore the possibility of configuring the spring characteristic of the diaphragm-spring arrangement in such a way that, although both clutches are simultaneously closed when the release members of both clutches remain unactuated, the clutch torques of both clutches which are brought about with this mode of operation are each significantly below the maximum torque of the vehicle engine. This prevents locking up of the drive line if both clutches fail to close properly.
SUMMARY OF THE INVENTION
It is then the object of the invention to optimize the design of a twin clutch of the type stated above.
According to the invention, this object is achieved by virtue of the fact that the diaphragm-spring arrangement includes at least two diaphragm springs of essentially the same type arranged in series which, when the release members are unactuated and the clutches are free from wear, are preloaded to within the vicinity of an upper limit of their range of constant force and, within this range, have a pressure force at which approximately half of a maximum clutch torque to be transmitted can be transmitted at each clutch disc when the release members are unactuated.
The invention is based on the general idea of exploiting the fact that, in a range of medium spring travels, diaphragm springs have an essentially constant spring force. Arranging at least two diaphragm springs in series makes it possible to ensure a comparatively large spring travel with a constant spring force and to use it irrespective of clutch wear. It is possible at the same time to ensure the desirable protection of the drive line from locking up if the clutch torques brought about in the range of constant force of the diaphragm springs are each no more than half of the maximum torque to be transmitted, i.e. the maximum engine torque.
According to a preferred embodiment of the invention, the two diaphragm springs are arranged approximately symmetrically with respect to a radial plane of the coaxial shafts. In this arrangement, the abutments of the diaphragm-spring arrangement which are on the pressure-plate side can likewise be designed so as to be symmetrical with respect to one another, and an intermediate bearing between the two diaphragm springs can be dispensed with.
REFERENCES:
patent: 3215233 (1965-11-01), Smith et al.
patent: 4210232 (1980-07-01), Beccaris
patent: 4214653 (1980-07-01), Slack
patent: 4440281 (1984-04-01), Hauguth
patent: 5678669 (1997-10-01), Rainer
patent: 2044865 (1980-10-01), None
Salecker Michael
Tscheplak Ernst
Worner Gunter
Calcaterra Mark P.
Daimler-Chrysler AG
Lorence Richard M.
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