192 clutches and power-stop control – Clutches – Plural clutch-assemblage
Reexamination Certificate
1999-12-16
2001-07-31
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Plural clutch-assemblage
C192S057000, C192S058410, C192S058420, C192S10400R
Reexamination Certificate
active
06267214
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a coupling, either in the form of an conventional viscous coupling or in the form of a Viscotrac® coupling, comprising two parts which are supported inside one another, which are rotatable around a common longitudinal axis and which form an annular space which is filled with a highly viscous medium and in which there are arranged inner plates which are non-rotatably connected to the inner one of the parts and form a set of inner plates, as well as outer plates which are non-rotatably connected to the outer one of the parts and form a set of outer plates, said inner plates and outer plates being arranged so as to alternate in the longitudinal direction for the purpose of generating a coupling effect between the two parts when the latter rotate relative to one another.
In the case of conventional viscous couplings such as those described in DE 38 23 180 C1, the differential-speed-dependent or wheel-slip-dependent engaging effect is based on the build-up of shear forces in the viscous medium in the spaces between inner plates and outer plates.
In the applicant's Viscotrac® coupling described in DE 196 53 310 A1, differential-speed-dependent or wheel-slip-dependent shear forces are built up in the viscous medium in the spaces between inner plates and outer plates in the same way as described above. In addition, in a helical channel between a cylindrical surface of an annular piston dividing the annular space into two chambers and a counter face of the annular space, a medium is conveyed by shear forces from the one chamber into the other chamber, so that the annular piston is axially displaced in the annular space and moves part of the inner plates and outer plates of the coupling plate type into friction contact.
Couplings of said type are used in the driveline of a motor vehicle which comprises both a constantly driven axle and an axle that is driven only if there exists slip between the wheels of the axles, the couplings being provided in the connecting driveline between the two axles.
Under operational conditions, for example, when accelerating from start conditions or during off-highway driving or in curves, when at the constantly driven axle there is wheel-slip, there occurs a relative rotation between the coupling parts, as a result of which a coupling effect is built up, so that the second axle is also driven. In the case of vehicles with new types of driving dynamics systems which, for instance, cause the brake to engage in individual wheels if lateral guidance is lost at the wheels, just as in the case of vehicles with anti-lock braking systems which release the braking force when a wheel is locked, control must be affected only to a slight extent by said coupling engagement. It is therefore the object of the present invention to provide a coupling of the above-mentioned type which is more compatible with control systems for driving dynamics and with anti-lock braking systems of motor vehicles.
BRIEF SUMMARY OF THE INVENTION
The present invention is embodied in and carried out by a coupling of the aforesaid type, wherein in the case of a viscous coupling, the objective is achieved in that a partial set of one of the complete sets of inner plates and outer plates is directly carried by a sleeve which is coupled to that part of the coupling which carries said complete set of inner plates or outer plates in such a way that it will be uncoupled in respect of relative rotation at a raised rotational speed. The corresponding solution in the case of a Viscotrac® coupling consists in that the annular piston is carried directly by a sleeve which is connected to the coupling part carrying the annular piston in such a way that it will be uncoupled therefrom in respect of relative rotation at a raised rotational speed. In particular, it is proposed that a partial set of one of the sets of inner plates and outer plates is also carried directly by the sleeve. The above-mentioned helical channel can be formed by a groove in the cylindrical surface, or in the counter face of the annular space, or optionally in an inserted sleeve.
By using a coupling of this type, it is possible to provide a two-part characteristic curve with a jump function which, in a first portion over the rotational speed follows the characteristics of a viscous coupling or of a Viscotrac® coupling of a certain size and, in a second portion over the rotational speed, represents the characteristics of a viscous coupling with a much smaller number of plates. The latter characteristics are able to provide the comparability with a control system for driving dynamics, a slip limiting control system or an anti-lock braking system. The coupling can be switched from one part of the characteristic curve to the other part of the characteristic curve by any conceivable means, in particular by magnetic, pneumatic or hydraulic means, with the switching process being released by the corresponding control system for driving dynamics or the corresponding anti-lock braking system. All these systems record the vehicle speed and hence the rotational speed of the coupling, which is decisive for the switching process.
According to a preferred simple solution, switching can be effected by a mechanical setting device which is actuated by a centrifugal force and which is integrated into the coupling. In such a case again, it has to be assumed that the rotational speed of the coupling is proportional to the vehicle speed. The setting device actuated by a centrifugal force can comprise circumferentially positioned ball members which, on the one hand, are supported on a first radial face and, on the other hand, on the conical face of an axial adjusting element. The coupling device for the sleeve actuated in this way can, substantially, comprise a central draw key which, in the case of an axial adjustment, causes dwelling balls to engage, or be disengaged from, the respective part of the coupling or of the sleeve in a rotationally positive way. Further preferred embodiments of the invention are described hereunder in further subclaims to which reference is made hereby.
REFERENCES:
patent: 4690258 (1987-09-01), Teraoka et al.
patent: 5156247 (1992-10-01), Weise et al.
patent: 5273147 (1993-12-01), Beigang et al.
patent: 5338266 (1994-08-01), Guimbretiere
patent: 3823 180 C1 (1990-02-01), None
patent: 196 53 310 C1 (1996-12-01), None
patent: 1-224528 (1987-05-01), None
patent: 62-118123 (1987-05-01), None
patent: 63-9734 (1988-01-01), None
GKN Viscodrive GmbH
Lorence Richard M.
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