Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
1997-12-12
2001-01-09
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Coupling transmits torque via radially spaced ball
C464S906000
Reexamination Certificate
active
06171196
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a VL constant velocity universal joint for accommodating axial displacements in a propeller shaft of a motor vehicle and for connecting a drive unit to a rear axle gearbox, having at least two articulatably connected shaft portions, a standard plunge usable in a damage-free way, an outer joint part with outer ball tracks, an inner joint part with inner ball tracks, a plurality of torque transmitting balls each guided in outer and inner ball tracks associated with one another, with associated outer ball tracks on the one hand and inner ball tracks on the other hand, forming angles of intersection in respect of the central axis A of the joint, which are of identical size but are set in opposite directions, and having a ball cage which is provided with a plurality of cage windows each accommodating one of the balls and which hold the balls in one plane when the joint is axially displaced or articulated, with the outer joint part having to be connected to an annular flange and the inner joint part to a connecting shaft.
Propeller shafts of this type are used in motor vehicles to transmit torque from a front drive unit to the rear axle. Apart from having to ensure functional safety under normal operating conditions, these structures also have to fulfil certain requirements in the case of a vehicle crash wherein the front part of the vehicle and thus the first part of the propeller shaft is displaced towards the rear axle. To prevent the shaft from kinking towards the vehicle cell and in order not to prevent a greatest possible absorption of energy in the front part of the vehicle through deformation work, by supporting the drive unit at the rear axle, and to avoid any damage to the rear axle, it must be possible to shorten the shafts further beyond the range predetermined by the standard plunge of the VL joint with a minimum of energy being absorbed. The component particularly suitable for accommodating such shortening is the respective axially plungeable constant velocity universal joint in the propeller shaft.
Propeller shafts of this type for motor vehicles are known from DE 42 24 201 C2 wherein it is proposed that at the end of the predetermined standard plunging distance between the outer joint part and the inner joint part, the balls of the cage stop against the annular flange and that the connection between the plug-in shaft and the inner joint part is to be destroyed. Hereafter, the plug-in shaft slides into the annular flange and into the hollow shaft adjoining same. This embodiment presupposes plug-in shafts which, with a reduced diameter, follow the toothed region engaging a correspondingly toothed region in the inner joint part.
DE 43 44 177 C1 describes a similar type of propeller shaft for motor vehicles, which comprises a cage-less joint with axis-parallel ball tracks, which cage-less joint, in operation, is suitable for very small articulation angles only. With this embodiment, the plug-in shaft cannot be slid in beyond the predetermined standard plunging region unless the outer joint part and the adjoining tubular shaft are deformed, thus absorbing a large amount of energy.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a VL constant velocity universal joint for a propeller shaft of a motor vehicle, which joint, after the predetermined standard plunging distance has been exceeded, is destructible with only a small amount of energy being absorbed and which, in an non-obstructive way, permits the plug-in shaft to be inserted further along a considerable length towards the annular flange.
The objective is achieved in that, when the outer joint part is displaced relative to the inner joint part, the effective guiding length of the ball tracks in one of the two joint parts, in the sense of shortening the propeller shaft, is shorter than the effective guiding length of the ball tracks in the other one of the two joint parts; that there are provided stop means which become effective at the end of the standard plunging path to prevent the balls from leaving the ball tracks with the shorter guiding length; and that the stop means comprise nominal deformation means which are deformable when the standard plunging path is exceeded.
The effect of these measures consists in that, after a predetermined standard plunging length has been exceeded, there first become effective stop means which prevent unintended dismantling during transport and assembly and which, without suffering any damage, limit any drive unit displacement relative to the rear axle drive, such displacement occurring in service under extreme service loads. In the case of loads exceeding the aforementioned loads, which only occur as a result of deformation suffered by the front part of the vehicle in an accident, the nominal deformation means are destroyed. Thereafter, with only slight resistance forces having to be overcome, the balls are caused to leave the ball tracks of one of the two joint parts so that axial forces can non longer be supported by the propeller shaft and the transmission of torque ceases immediately. This means that the propeller shaft can be shortened further while absorbing only small amounts of energy.
According to first preferred embodiments it is proposed that, starting from a central plane of the joint, the inner ball tracks at the shaft connection end are shorter than the outer ball tracks at the annular flange end or the outer ball tracks at the annular flange end are shorter than the inner ball tracks at the shaft connection end.
In these embodiments, there are provided stop means which, as nominal deformation means, have to be deformed or destroyed before the balls are able to leave the ball tracks. The stop means can be provided directly at the ends of the respective shorter ball tracks, for example in the form of annular members arranged between the connecting shaft and the inner joint part or the outer joint part and the annular flange or they can be provided locally independently of the shorter ball tracks in the form of a cover which is inserted into the annular flange or the adjoining tubular shaft and against which there stops the inner joint part and, respectively, a front end of the connecting shaft inserted into same.
According to a second embodiment it is proposed that the inner ball tracks in the inner joint part comprise track end portions consisting of an elastically resilient or easily plastically deformable material and that in the circumferential direction, the cage windows form fixed end stops for the balls when these reach the track end portions. When, by reaching the fixed end stops in the cage windows, the balls are prevented from moving further in the circumferential direction and thus from being displaced further along the ball tracks extending at an angle of intersection, axially moving the balls out of said ball tracks while deforming the track end portions is achieved. In this embodiment, said track end portions form the destructible nominal deformation means of the stop means, i.e. in this case, too, the effective guiding length of one of the joint parts is reduced. The plasticity of the track end portions can be achieved by doing without hardening the respective joint parts in this region.
The annular members which serve as nominal deformation means may consist of plate metal rings or plastic rings. The annular elements may optionally cooperate with the balls or with the cage. By providing the annular elements or cover parts in the annular flange with a suitable design, it is possible to set the absorption of a defined amount of energy after the dismantling of the joint, while shortening the propeller shaft further, provided this is desirable as an additional measure towards the absorption of energy in the front part of the vehicle in the case of a vehicle accident. The cover parts can also be used as means additional to the second embodiment.
Fixed stops can be provided at the ends of the respective longer ball tracks. Alternatively, it is possible to provide axial stops
Binda Greg
Browne Lynne H.
GKN Lobro GmbH
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