Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
1999-07-09
2001-06-26
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
C464S167000, C464S906000, C464S180000
Reexamination Certificate
active
06251021
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a drive assembly which comprises a constant velocity fixed joint and means for attaching same to a driving or driven attaching part.
Constant velocity fixed joints are known in various designs. For example, DE 40 31 820 C2 describes a constant velocity fixed joint whose outer part comprises a first and a second open end. The device comprises a cavity which is centered on the longitudinal outer part axis and which is open towards both open ends. Furthermore, the outer part, in its inner face delimiting its cavity, is provided with two types of outer running grooves which are arranged in a regular sequence around the longitudinal outer part axis in planes containing the longitudinal outer part axis. The first outer running grooves start from the first open end and extend towards the second open end in a curve-like and undercut-free way. The second outer running grooves start from the second open end and extend towards the first open end in a curve-like and undercut-free way. In the cavity of the outer part, there is arranged an inner part. The inner part comprises a longitudinal inner part axis and a spherical outer face in which there are provided first and second inner running grooves which are positioned opposite the first and second outer running grooves and which, with reference to the longitudinal inner part axis, are arranged in planes containing the longitudinal inner part axis. The first inner running grooves are positioned opposite the first outer running grooves in such a way that they form pairs, with the first inner running grooves starting from the first open end and extending towards the second open end in a curve-like and undercut-free way. The second inner running grooves are arranged opposite the second outer running grooves and form pairs therewith, while starting from the second open end and extending towards the first open end in a curve-like and undercut-free way. Between the inner face of the outer part and the spherical outer face of the inner part, there is arranged a cage whose spherical outer face comprises play relative to the inner face of the outer part. The cage comprises a cylindrical bore which is held with play relative to the spherical outer face of the inner part. The cage comprises radial apertures which are distributed in accordance with the pairs of inner running grooves and outer running grooves and constitute windows and guide balls which, for the transmission of torque between the outer part and inner part, each engage a pair of outer and inner running grooves. The centers of all balls are held in a plane containing the window centers.
Such joints are intended to be used in the driveline provided for driving the wheels of a motor vehicle. They can be used in either propeller shafts or in sideshafts. Sideshafts extend from the axle drive to the driven wheels. For example, they connect the output ends of the rear axle differential with the driven wheel hubs of the wheels. Propeller shafts serve to transmit the drive from the gearbox output of the front wheel drive unit to the rear axle differential associated with the rear axle.
As far as propeller shafts are concerned, a number of different designs are used. They may comprise, for example, two joints which are arranged at the end of a shaft connecting same and which serve to be connected to the gearbox output in front and to the drive input at the rear. However, it is also possible to use a driveline consisting of several portions, for example two portions between which there is provided a bearing. Normally, at the ends of the propeller shaft, i.e. towards the gearbox output and the drive input, there are arranged universal joints. It is also possible for a universal joint to be provided in the central region. However, a constant velocity plunging joint can also be provided in said central region; for instance see the book by Prof. Dipl.-Ing. Jörnsen Reimpell: Fahrwerktechnik 1, 5
th
edition, Vogel-Verlag, page 285, Figure 3.1/21.
The drive unit of the motor vehicle generates vibrations which, in prior art assemblies, are transmitted to the propeller shaft in the form of movement vibrations and structure-borne sound. In this context it has to be taken into account that propeller shafts rotate at high speeds. In addition, changing torque values and rotational speeds constantly occur during the transmission of the rotational movement.
SUMMARY OF THE INVENTION
It is an object of the invention to propose a drive assembly which achieves smoother running characteristics of the vehicle in order to meet the ever increasing demands in respect to comfort.
In accordance with the invention, the objective is achieved by providing a drive assembly comprising a constant velocity fixed joint having an outer part which comprises a longitudinal outer part axis, a cavity and, in the cavity, outer running grooves extending in planes which are distributed around the longitudinal outer part axis and contain said axis. The outer part further comprises a flange to be connected to a driving or driven attaching part. The assembly also includes an inner part which is arranged in the cavity of the outer part and which, in its outer face, comprises inner running grooves which are positioned opposite the outer running grooves and which are arranged in planes which are distributed around the longitudinal inner part axis and contain said axis. The assembly further comprises a cage which is arranged between the outer part and the inner part. The cage is provided with windows distributed in accordance with the pairs of opposed outer and inner running grooves. Balls are also included which are guided in the windows of the cage and each extend into an associated outer running groove and inner running groove. Each of the above-mentioned components consist of a ferrous material. The above drive assembly, furthermore, comprises a damping element which consists of a material whose modulus of elasticity is smaller than that of the ferrous material and which is arranged in front of the flange of the outer part of the constant velocity fixed joint.
The advantage of the present embodiment is that by including a damping element whose modulus of elasticity is smaller than that of the material of which the components of the constant velocity fixed joint are produced and, together with the constant velocity fixed joint, vibrations are damped. The damping element is arranged between the flange of the outer part of the constant velocity fixed joint and the attaching part of the driving or driven component. It is also possible to arrange a cap therebetween which closes the outer part, for example.
According to a further embodiment of the invention, it is proposed that the damping element itself is provided in the form of a cover closing the outer part. However, it is also possible to provide the damping element in the form of a ring and to provide a separate cover.
A particularly advantageous damping effect is achieved if the modulus of elasticity of the material of which the damping element is made is less than 50% of the modulus of elasticity of the ferrous material used for producing the outer part and the remaining components of the constant velocity fixed joint, i.e. the inner part, the cage, and the balls. A preferred material for the damping element is an aluminum material. The damping element can also be produced from plastics, in which case it is important to select a design which reduces the flow of the plastic material. This can be achieved, for example, by using a plastic material with embedded fibers, preferably carbon fibers. Furthermore, a rubber ring reinforced by inserts, such as steel inserts, is advantageous.
In addition, such a drive assembly can actively prevent the transmission of movement vibrations from the drive unit and the component to be driven if the constant velocity fixed joint is additionally associated with a plunging unit with rolling contact members which engage guiding grooves. Such rolling contact member displacing elements comprise a friction coef
Browne Lynne H.
GKN Lobro GmbH
Thompson Kenneth
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