Patent Application
20100197414
The present application claims priority to European Patent Application No. 08172926.1 filed on Dec. 23, 2008, the contents of which are incorporated fully herein by reference.
The present invention refers to the coupling between a constant velocity joint and a hub bearing unit of a motor vehicle wheel.
Couplings between constant velocity joints and hub bearing units are known, such as for example, the arrangements disclosed in US Patent Application No. 2002/0070506 A1 and U.S. Pat. No. 6,354,952. In each prior art arrangement, the hub of the wheel receives driving torque from the bell of a constant velocity joint through a straight splined coupling. A ring is fixed on the hub with an axial outer tooth that is telescopically inserted in a tubular projection with an inner axial tooth of the outer part or “bell” of the constant velocity joint. The toothed ring and the tubular projection are both provided with a respective circular groove into which an elastic, open ring (or circlip or Seeger ring) is fitted to axially lock the hub to the joint.
The above conventional arrangement, although being highly serviceable, has the drawback of limited sealing capacity. More specifically, the above-described elastic ring has two gripping arms at its ends that project through a slot formed at the axially outer end (or outboard end) of the joint bell. As depicted in FIG. 5 of US Patent Application No. 2002/0070506, a rubber sleeve covers the slot in order to seal it. The sleeve provides only a minimally efficient sealing that often allows water to penetrate, especially through the slot formed at the end of the joint bell, into the splined interface zone. Rust may then form at the interface of the splined coupling, which renders the disassembling operation of the hub-bearing unit from the constant velocity joint particularly difficult and shortens the life of the coupling members.
It is a primary object of the invention to optimize the hermetic sealing action at the interface zone between the constant velocity joint and the hub bearing unit, closing the passages through which water may leak into the inner parts of the constant velocity joint and preventing water from accessing the splined coupling between the joint and the hub-bearing unit. Another object of the invention is to facilitate the assembly and disassembly of the hub-bearing unit to and from the constant velocity joint.
These objects are achieved, according to one aspect of the present invention, by a coupling arrangement that includes a rigid cap member received in the cavity of the bell member of the constant velocity joint and which axially abuts against a radial shoulder formed within the bell member. The hub and the constant velocity joint are releasably axially secured by a fastening means releasably connecting the cap to the hub in an axially tractive relationship (i.e., axial tension biases or pulls the cap generally toward the hub). The axial traction causes axial compression of an annular sealing gasket fitted between the bell member and the hub-bearing unit. As a result, a continuous sealing action is provided around the engaging splines of the bell member and the driving ring fixed to the hub.
A conventional straight splined coupling has a drawback due to the high noise that can be heard when the car is put into reverse, owing to the circumferential play between the splines on the bell of the constant velocity joint and the driving ring fixed on the hub.
It is a further object of the invention to overcome the above mentioned drawback concerning the noise. This other object is achieved, according to another aspect of the invention, by a coupling as defined in claim 10 or 11. The splined coupling is modified so that one of the two coupling members, i.e. the joint bell or the driving ring, has involute splines whereas the other member has straight axial splines. Due to the engagement of the different splines the relative angular or circumferential play between the constant velocity joint and the hub is taken up.
Preferred embodiments of the invention are set forth in the dependent claims.
The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, left”, “lower”, “upper”, “upward”, “down” and “downward” designate directions in the drawings to which reference is made. The words “inner”, “inwardly” and “outer”, “outwardly” refer to directions toward and away from, respectively, a designated centerline or a geometric center of an element being described, the particular meaning being readily apparent from the context of the description. As used herein, terms such as circumferential, radial, or axial are to be construed with respect to the central axis of rotation x of the hub. Further, as used herein, the words “connected” and “coupled” are each intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.
With reference initially to
The hub has a cylindrical surface 17 towards its axially outer end, onto which there is fixed a driving ring 18 with outer axial splines or teeth 19 for transferring the driving torque from the bell 30 of the constant velocity joint to the hub.
The driving ring 18 is securely axially locked against the inner bearing race 14 by cold forming, preferably by orbital rolling, of an end edge 20 of the hub. At an axially outer side, the joint bell 30 forms a tubular projection 31 within which the driving ring 18 is telescopically fitted. Formed within the tubular projection 31 are inner axial splines 32 which couple with the outer splines 19 of the driving ring 18.
The two engaging splines are of different types. The outer splines 19 of the driving ring may be axially straight and the inner ones 32 of the joint bell may be involute, or vice-versa. The helical pitch of the involute splines has sufficient length to allow an initial effortless insertion of the driving ring 18 into the joint bell, preferably with a slight angular play between these two members. During insertion of the ring 18, the flanks of the straight axial splines and the involute splines come into contact, taking up the angular play between the hub and the joint bell. Preferably, the helical pitch of the involute splines is selected such that an amount of axial force is required to reach the fully coupled condition shown in the drawing figures. This condition is schematically shown in
An elastic sealing ring 21 is axially compressed between the axially outer face 33 of the bell 30 and the facing axially inner face 22 of the bearing race 14.
The hub and the constant velocity joint are axially removably connected by an inner cap 40 which is received within the cavity of the joint bell and encloses it towards the outside. The cap has a peripheral edge or skirt 41 axially abutting against a radial shoulder 34 formed within the cavity of the bell. The cap 40 provides a central threaded bore 42 within which a fastening element 43 (e.g., a screw) is threadably engaged within a bore 44 extending centrally through the hub and which is tightenable from the outside (i.e., externally tightenable). Tightening the fastening element 43 displaces the hub toward the joint and causes axial compression of the sealing ring 21, thereby assuring an efficient sealing at the interface between the hub and the constant velocity joint.
In the alternative embodiment of
The embodiment of
As will be appreciated, the axial locking by means of the inner cap avoids the conventional circlip and the relevant slot in the bell for accessing the end gripping arms of the circlip. Hermetic sealing is ensured continuously around the splined coupling due to the ring being compressed between the bell joint and the bearing unit. This arrangement provides for compression of the sealing member and, to a certain extent, the sealing member is protected by two facing surfaces. Such an arrangement is more reliable over a period of time in comparison with a seal provided by a known rubber sleeve, which is relatively thin, less durable and subject to deterioration. It will also be appreciated that the absence of angular play between the hub and the joint bell eliminates the noise that is typically heard when a car is put into reverse gear with a splined coupling of conventional design.
Variations and modifications of the foregoing are within the scope of the present invention, and it will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. For example, those skilled in the art will readily recognize that the invention can be equally implemented if the involute splines are formed on the driving ring and the straight ones on the joint bell. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as generally defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08172926.1 | Dec 2008 | EP | regional |
