Rotary shafts – gudgeons – housings – and flexible couplings for ro – Fluid coupling – Including piston axially movable in cylinder having axis...
Reexamination Certificate
1999-12-27
2001-10-09
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Fluid coupling
Including piston axially movable in cylinder having axis...
C192S035000, C192S1030FA, C464S010000, C464S042000
Reexamination Certificate
active
06299538
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a coupling for transmitting torque between two parts which are rotatable relative to one another, which coupling comprises a friction coupling whose friction plates are each non-rotatably connected alternately to the one or to the other of the two parts which are rotatable relative to one another, having a pressure chamber which is filled with a highly viscous fluid and which is formed by a housing formed in one of the rotatable parts and by a displaceable piston sealed relative to said housing, and having a pump unit in which there rotates a conveying member connected to the other one of the rotatable parts, wherein a reservoir for a highly viscous fluid is provided in the housing, which reservoir is connected to the pump unit, and wherein the pressure chamber is supplied by the pump unit and wherein the piston loads the friction coupling.
Couplings of said type can be used as locking devices in axle differentials or central differentials, with axle differential, in the present context, meaning the conventional differential drive between the wheels of a driven vehicle axle, which differential drive is driven by a propeller shaft, and with central differential meaning the differential drive between two driven axles of a motor vehicle, which differential drive is driven by an intermediate driveshaft. In addition, couplings of said type can be used directly in a propeller shaft for a drive axle which is driven when required and which is torque-loaded only in the case of slip at a permanently driven drive axle. Couplings of said type are known, in particular, to have fluid shear pumps of the Visco-Lok® type as actuating elements. The fluid shear pumps used in said couplings, in view of the design principle, can only generate a limited volume flow which, with an increasing pressure, decreases towards zero even if there are no leakages. The volume flow of the fluid shear pumps can be increased by a wider or deeper shear channel. However, in view of the space restrictions, such an increase has its limits. The Visco-Lok® couplings provide soft connecting characteristics which are advantageous in avoiding engaging impacts and torque peaks, for example when used in pick-up vehicles and off-highway vehicles and which benefit the braking stability of the vehicle. For applications involving high demands regarding the reaction speed, the volume flow generated by the fluid shear pumps of Visco-Lok® couplings is not always sufficient.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide a coupling of said type which comprises the advantages of the Visco-Lok® couplings and does not feature any restrictions regarding the reaction speed. The objective is achieved in a coupling for transmitting torque and comprising first and second parts which are rotatable relative to one another, and further comprising a friction coupling whose friction plates are each non-rotatably connected alternately to the one or the other of said first and second rotatable parts, and a pressure chamber which is filled with a highly viscous fluid and which is formed by a housing formed in one of the rotatable parts and by a displaceable piston sealed relative to said housing, and further comprising a pump unit in which there rotates a conveying member connected to the other one of the rotatable parts, wherein a reservoir for said highly viscous fluid is provided in the housing, said reservoir being connected to said pump unit, and wherein said pressure chamber is supplied by said pump unit and wherein said piston loads said friction coupling, wherein the pump unit is provided in the form of an internally toothed rotor pump and the conveying member forms an externally toothed rotor which is concentrically connected to the other one of the parts which are rotatable relative to one another, and an internally toothed hollow gear constitutes a runner which is eccentrically supported and is dragged along by the externally toothed rotor, with the rotor together with the hollow gear forming a rotating pump chamber, and wherein the pump chamber of the rotor pump is laterally delimited by an end face of a reversing and guiding element on one side and by an end face of a sealing disc on the other side, and, by means of fluid friction forces, the reversing and guiding element is rotatable to a limited extent between two end positions relative to the one of the two parts rotatable relative to one another, and a pressure channel connects the pump chamber to the pressure chamber and a return line connects the pressure chamber to the reservoir.
While using the major characteristics of the Visco-Lok® coupling, i.e., a sealed system filled with a highly viscous fluid, the inventive type of pump is an internally toothed pump which meets the named objective. The advantage of the Visco-Lok® coupling having a negligible influence of temperature is maintained, as is the advantage of a hermetically sealed, maintenance-free and autonomously functioning system. In this case, by using a reversing element, the pump units also build up pressure independently of the direction of relative rotation between the two parts rotatable relative to one another, with a highly viscous fluid being guided directly into the pressure chamber for the purpose of displacing the piston.
According to a preferred embodiment, it is proposed that in the housing or in the reversing and guiding element, there are provided two C-shaped channels which, on the one hand, act as suction channel and, on the other hand, as pressure channel of the rotor pump, and that there are provided a connecting bore in the housing between the reservoir and the channels and a pressure channel in the housing between the channels and the pressure chamber and that in each of the two end positions of the reversing and guiding element, alternately, one of the channels is connected to the connecting bore and the other channel is connected to the pressure channel.
In a way that is known in itself, the C-shaped channels are designed to be symmetrical relative to the eccentricity of the runner bearing and are openly connected to the pump chamber. The two C-shaped channels are preferably provided in the form of through-holes or slots in the reversing and guiding element which are directly connected to the connecting bore(s) and the pressure channel. The two C-shaped channels can also be provided in the form of surface grooves in the housing, with the connection with the connecting bore(s) and the pressure channels being provided substantially by corresponding channels in the reversing and guiding element. The pressure channel is preferably provided by a groove in the end face of the pressure chamber.
Further structural design characteristics consist in that the means for supporting the hollow gear are provided in the form of an eccentric inner cylindrical face in the reversing and guiding element, which is supported centrally relative to the housing. The quantity of viscous medium conveyed corresponds to a multiple of the quantity conveyed in prior art Visco-Lok® pumps, so that said reaction speed can be increased accordingly. The pump characteristics can easily be set by dimensioning the return bore leading to the reservoir. It is possible to provide elements in the return bore which compensate for the effect of temperature. Further preferred embodiments are described hereunder in further sub-claims.
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Browne Lynne H.
Dunwoody Aaron
GKN Viscodrive GmbH
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