192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
1999-07-02
2001-10-02
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S057000, C192S025000
Reexamination Certificate
active
06296095
ABSTRACT:
BACKGROUND OF THE INVENTION
There are known coupling assemblies for transmitting torque between a first part and a second part, each of said parts being rotatable with respect to one another. A coupling assembly of this type is described in German Patent No. P 43 43 307 C2, and is sold by the assignee of the present application under the trademark VISCO-LOK™.
Such a coupling assembly, which may be referred to as a locking or limited-slip differential device, has various practical applications. A first application is in a differential drive to provide a self-inhibiting or self-locking effect. Such differential drives may constitute axle differentials or central differentials in automotive vehicles.
A second application of a coupling assembly of this type is in the drive train of automotive vehicles having one permanently-driven axle and one axle which is selectively driven only when the coupling assembly is closed, with the coupling assembly being connected between two portions of a shaft linking the source of automotive power to the selectively-driven axle. If a speed differential occurs between the permanently-driven axle and the selectively-driven axle, the coupling assembly is closed to exert torque on the selectively-driven axle. If no speed differential exists between the permanently-driven axle and the selectively-driven axle, the coupling assembly is opened to render the selectively-driven axle free-wheeling.
The reaction behavior of the coupling assembly and the achievable pressure values in the pressure chamber are determined by geometry, particularly by the width and depth of the shear channel. With a predetermined coupling assembly diameter, the width of the shear channel is particularly limited. Although pressure generation may be very effective, and the piston able to apply high forces to the friction coupling, there are applications wherein a more rapid reaction and/or the application of even higher forces to the piston are/is essential, even at small speed differentials.
The present applicants have addressed this need, and have designed a coupling assembly that exhibits such increased performance characteristics without the need for an assembly of undesirably large axial and radial dimensions.
SUMMARY OF THE INVENTION
The present invention is embodied in a coupling assembly for transmitting torque between a first part and a second part, said parts being rotatable with respect to one another. The coupling assembly comprises a friction coupling having first friction plates non-rotatably connected to the first part of the coupling assembly and second friction plates non-rotatably connected to the second part of the coupling assembly. The coupling assembly further comprises a pressure-generating device comprising a pump body member, an axially-displaceable piston loading the friction coupling, and a pressure chamber formed by the pump body and by the piston and filled with a highly-viscous fluid, with the pump body member being non-rotatably connected to the first part of the coupling assembly, and with at least one conveying plate being provided in the pressure chamber and non-rotatably connected to the second part of the coupling assembly. A shear channel with a control member is provided in the pressure chamber, the control member cooperating with at least one conveying plate.
In a first embodiment of the inventive coupling assembly, the shear channel with a control member forms two circumferential grooves of limited length and each covered by one of the two radial surfaces of the conveying plate, thereby forming two shear channels. The conveying plate comprises passages through which the two shear channels are connected to one another. There is also an open connection between one end of each of the two shear channels and a reservoir, and between the other end of each of the two shear channels and the pressure chamber.
In a second embodiment of the inventive coupling assembly, the shear channel with a control member forms a circumferential groove of limited arcuate length which is covered by one of the two radial surfaces of the conveying plate, thereby forming a first shear channel. In the shear channel with a control member, there is a circumferential slot of limited arcuate length which is covered by the other one of the two radial surfaces of the conveying plate and by a second conveying plate, the latter being non-rotatably connected to the second part of the coupling assembly to form a second shear channel. The first conveying plate includes fluid passages extending therethrough and connecting both shear channels to one another. There is an open fluid connection between one end of the second shear channel and a reservoir, and between the other ends of both shear channels and the pressure chamber.
In the shear channel-control member subcombination of this invention, there are formed two shear channels: in the first embodiment, both channels are formed entirely by the one and only conveying plate; in the second embodiment, one channel is formed entirely by a first conveying plate, and the second channel by the first conveying plate in cooperation with a second conveying plate. By retaining the existing external diameter of the pressure-generating assembly and by leaving the design of the main components unchanged and keeping the design changes simple, the capacity of the pressure generating unit is doubled, while only the functional parts contained in the pressure chamber are modified. Because of the sound design of the pump body member and the piston in the prior art embodiments, the present applicants' inventive structural designs can be achieved as described herein without any need for modification of those components.
Several features ensure that the coupling is effective in both directions of rotation of the first part relative to the second part. For this purpose, in the pump body member at least one axial connecting channel is provided for connecting the reservoir with the shear channels, and at least one radial connecting channel is provided for connecting the shear channels to the pressure chamber. Furthermore, in the shear channel-control member subcombination, control apertures are provided for connecting the first ends of the two shear channels to the first ones of the connecting channels and for connecting the second ends of the two shear channels to the second ones of the connecting channels. In addition, the shear channel-control member subcombination is rotatable through a limited angle relative to the pump body member so that in the first limit position, one end of each of the shear channels is connected to the reservoir, with the respective other end of each of the shear channels being connected to the pressure chamber, and that in the second limit position, each of the above-mentioned first ends of the shear channels is connected to the pressure chamber, with each of the above-mentioned second ends of the shear channels being connected to the reservoir.
The inventive through-apertures ensure that both the control apertures and the connecting channels for the two shear channels can be of simple design. According to the first preferred embodiment, the shear channel-control member subcombination consists of two dish-shaped formed sheet metal parts in which the grooves are formed by being stamped out. According to the second preferred embodiment, the shear channel-control member subcombination is formed of two dish-shaped sheet metal parts in which the groove is produced by being stamped out of the first part, with the slot being formed by being punched out of the second part.
REFERENCES:
patent: 4574926 (1986-03-01), Bubak
patent: 4997071 (1991-03-01), Villata et al.
patent: 5556343 (1996-09-01), Gassmann et al.
patent: 5706923 (1998-01-01), Gassmann
patent: 5935036 (1999-08-01), Gassmann et al.
patent: 43 27 519 A1 (1995-02-01), None
patent: 43 43 307 A1 (1995-06-01), None
Böttger Frank
Gassmann Theodor
GKN Viscodrive GmbH
Marmor Charles A
Rodriguez Saul
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