Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
1999-12-06
2001-10-09
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, C464S145000, C464S143000
Reexamination Certificate
active
06299544
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a constant velocity ball joint and, more particularly, to a double-offset joint with centering means for a cage. Constant velocity ball joints include an outer joint part with an inner cylindrical guiding face provided with first, longitudinally extending ball grooves; an inner joint part with a convex guiding face provided with second, longitudinally extending ball grooves; and torque transmitting balls which run in the first and second ball grooves. The balls are held by an annular ball cage in a ball center plane E. The ball cage comprises an outer spherical control face whose greatest diameter is axially removed in a first direction by a distance x from the ball center plane E. The ball cage also comprises an inner concave control face whose greatest diameter is axially removed in a second direction by a distance x from the ball center plane E. The inner control face in the ball cage forms end stops for delimiting an axial displacement path of the inner joint part relative to the ball cage. With reference to the positions of the central planes of the control faces at the ball cage relative to the ball center plane, such joints are called double offset joints (DO joints). They are described in DE 24 61 226 C2, for example.
If the outer joint part is articulated relative to the inner joint part, the control faces at the ball cage control the balls received in circumferentially distributed cage windows in the ball cage in such a way that they move on to the plane bisecting the angle between the axes of the outer joint part and of the inner joint part. In consequence, while ignoring the different contact radii, the balls carry out a predominantly rolling movement in the outer ball grooves and in the inner ball grooves.
Because the cage, by way of the outer control face, engages the inner cylindrical guiding face of the outer joint part with a corresponding diameter, the joint is also able to carry out axial displacement movements between the outer joint part and the inner joint part. Under ideal conditions, it is assumed that by rolling movements, the balls would set themselves in the outer ball grooves and the inner ball grooves to half the axial displacement between the inner joint part and the outer joint part. In fact, however, the balls are prevented from doing so because of the substantially fitting, positive engagement between the ball cage and the inner joint part. Furthermore, because of the common axial movement of the ball cage and the inner joint part, there occurs a sliding movement between the balls and the inner ball grooves. As a result, there are generated high axial displacement forces in the joint. Moreover, any vibrations introduced into the joint are transmitted almost in their entirety.
By specifically designing the convex guiding face of the inner joint part as compared to the inner concave control face of the ball cage, it has already been proposed to permit a short axial displacement path between the ball cage and the inner joint part. This is intended to permit the required rolling movements of the balls in the inner ball grooves in a small axial region and thus to reduce friction and to tackle the problem of the transmission of vibrations in the range of slight axial vibration symptoms. But in such a case, the ball cage—because of its indifferent position and the influence of torque when the joint is articulated—moves into one of the positions of abutment relative to the inner joint part. The result is that the required effect of free rolling movements in both directions is lost. In addition, if the joint is used in the motor vehicles for example, vibrations are transmitted “rigidly” from the engine-gearbox unit via the joint to the vehicle body.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a constant velocity joint that reliably cuts off the vibrations resulting from slight axial vibration symptoms.
According to the invention, there is provided a joint having a resilient means which is effective between the ball cage and the inner joint part and which, at least when the ball cage is axially displaced relative to the inner joint part from the center of the axial displacement path in one axial direction, is pre-tensioned.
According to a first embodiment, the joint includes one or more resilient members which are effective between the ball cage and the inner joint part and which, when the ball cage is axially displaced relative to the inner joint part from the center of the axial displacement path, are pre-tensioned. The resilient members ensure that the ball cage, especially when the joint is in the aligned position, is set, even under torque. Preferably, it is set to the center of the possible relative displacement path relative to the inner joint part, so that in the case of external axial excitations, the desired vibration cut-off is ensured by the joint. The characteristics of the joint when articulated are also improved because in that case, the different rolling paths in the outer ball grooves and inner ball grooves do not initially lead to sliding movements of the balls relative to the inner ball grooves. Further, from the central position of the ball cage relative to the inner joint part, relative axial displacements are possible. The tendency of the ball sliding in the inner ball groove is therefore avoided for a certain articulation angle.
A second embodiment comprises a constant velocity ball joint which is characterized by resilient members which are effective between the ball cage and the inner joint part and which, at least when the ball cage is axially displaced relative to the inner joint part from the central position of the axial displacement path in one axial direction, are pre-tensioned. According to this design, especially when the joint is articulated under torque, the cage is loaded in a first direction by forces applied by the ball grooves to the balls while being loaded by the resilient members in the opposed axial direction. Thus, in operation, the cage is set to the center of the possible relative displacement path relative to the inner joint part, thus achieving the desired vibration cut-off when external axial excitations are introduced into the joint.
According to a preferred embodiment, the resilient members consist of resilient annular rings which are inserted inside the ball cage and which are in contact with the convex guiding face of the inner joint part on both sides of the greatest diameter. For fixing the resilient members, there are provided simple recesses or grooves, otherwise, the design of the components remains unchanged. To increase the size of the contact face, the inner joint part can be axially increased in length in the direction of the outer control face of the ball cage.
In one embodiment, the resilient annular rings, on their inside or their outside, can be provided with radial fingers, by means of which, like plate springs, they are axially deflectable at their inner annular edges which cooperate with the inner joint part.
According to a further embodiment, the resilient annular rings can be radially resiliently inserted into the grooves or recesses in the ball cage, while being especially circumferentially slotted. When axially loaded by the inner joint part, such annular rings can be widened by being radially expanded, as a result of which they penetrate the grooves or recesses in the ball cage more deeply.
According to yet a further embodiment, the resilient annular rings can be provided in the form of a resilient crinkled spring washer which is supported by a securing ring and which, in itself, is axially compressible.
A preferred embodiment of the convex face of the inner joint part comprises two spherical face portions whose centers are displaced relative to the plane of the greatest diameter by equal amounts in opposite directions in such a way that the radii of curvature of the spherical face portions intersect one another. In a longitudinal section, this results in a so-called Gothic shape which, as comp
John Friedhelm
Schwarzler Peter
Browne Lynne H.
Dunwoody Aaron
GKN Lobro GmbH
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