Abstract:
A shift mechanism for a vehicle wheel wherein a pneumatic annular actuator, through air pressurization and depressurization, produces clutch ring movement to engage and disengage the wheel from the vehicle&#39;s drive axle. The components of the wheel end providing an air tight cavity in which the clutch ring is manipulated and which is subjected to air pressure changes. The components include a pneumatic annular actuator, a CV-joint, a rotary seal between the actuator and the CV-joint and a vent passage formed between the air chamber and rotary seal and breaching said air tight cavity. An air line from said passage to non-contaminated ambient air to provide continuous ambient air pressure to said cavity.

Description:
FIELD OF THE INVENTION 
     This invention relates to a mechanism in the wheel end of a vehicle for shifting the wheel between driven and non-driven states and more particularly it relates to the manner of maintaining the predictability of such shifting. 
     BACKGROUND OF THE INVENTION 
     Recent developments in four-wheel to two-wheel drive shift mechanism provides for clutch ring shifting inboard of the vehicle&#39;s knuckles at the front end of the vehicle. (See commonly assigned U.S. Pat. Nos. 6,170,628 and 6,234,289) A typical arrangement is one where a pneumatic annular actuator is mounted between the knuckle and the CV-joint. The actuator slidably moves a clutch ring for engagement and disengagement as between the CV-joint and the wheel hub of the vehicle. The actuator by its mounting produces a seal surrounding the inner cavity containing the clutch ring and associated components which are accordingly protected from contamination. The actuator produces actuation by axial movement of a flexible wall forming one side of an annular vacuum chamber. The flexible wall is exposed to the cavity and is connected to the clutch ring for moving the clutch ring and thus producing engagement and disengagement. 
     The sealing of the cavity provides a valuable function by keeping out dust and moisture that are contaminants that can interfere with the functioning of the shift components. That same seal, because it provides air tight sealing, can be disruptive of the shifting function. The area of the vehicle whereat the cavity resides is subjected to dramatic changes in temperature during normal operation of the vehicle. Elevation differences may also have an affect and even the axial movement of the movable wall which changes the cavity volume produces pressure changes. Whereas the sealing of the cavity is necessary to avoid contamination of the components (clutch ring, fork, bearings, etc.), the pressure changes within the cavity inhibits or enhances the expansion of the air chamber to negatively affect the predictability of the shifting force. An objective of the invention is to provide venting of the cavity to avoid pressure changes within the cavity but without allowing contamination of the cavity. 
     DESCRIPTION OF THE INVENTION 
     A solution to the above problem is to provide a special vent including an air line that is open to ambient air at a location where the air is not contaminated. This amounts to providing a passage at some point through the cavity wall, connecting an air line to the passage and extending the air line to a location where there are no contaminants, e.g., in the engine compartment of the vehicle. 
     As contemplated herein, a rotating CV-joint is located in close adjacency to a rotatively fixed knuckle. The annular actuator is mounted to the knuckle and includes a rotary seal that is in abutting relation with the rotating CV-joint and which prevents passage of air/contaminants between the actuator and the CV-joint. The CV-joint does not lend itself to attachment to a fixed air line and drilling a hole through the knuckle is undesirable for a number of reasons. The annular actuator is essentially an outer fixed ring and an inner expandable ring that form opposing walls of the expandable air chamber. An air line extends through the fixed wall and into the expandable chamber to provide controlled pressurization of the chamber and thus axial movement of the inner wall. A passage cannot be provided through the air chamber and the assembly of the three components (CV joint, knuckle and actuator) does not appear to lend itself to any form of venting. 
     The present invention nevertheless provides the venting of the cavity through the actuator but without breaching the air chamber. The metal ring forming the outer wall of the actuator is U or cup shaped. An inner elastomeric ring mates to the metal ring and provides the movable wall that expands into the sealed cavity whereat the clutch ring resides. In the prior actuator, a boss was provided integral with the metal ring and a hole or passage was drilled through the boss and through the metal ring and into the chamber. A vacuum tube extended from the hole in the boss to the intake manifold for pressurization of the chamber. The outer side of the ring is provided with the rotary seal that seals against the rotating CV-joint and creates the sealed cavity at the inner side of the actuator. The boss of the present invention is configured to overlap this rotary seal. A second passage or hole is drilled through the boss (and not through the metal ring) to the juncture whereat the rotary seal is attached to the metal ring. An annular groove is formed in the ring at the juncture and intersects the vent passage whereby exterior air can pass through the vent passage and into the groove. At least one slot and preferably several slots extend from the groove inwardly and behind the seal to the sealed cavity. An air line is connected to the passage and extends to a position where contamination is not a problem. 
    
    
     The above invention as briefly described provides an equalizing vent through or around the actuator where there is no apparent way to provide such a vent. The invention and the embodiments encompassing the invention will be more fully appreciated upon reference to the following detailed description and drawings referred to therein. 
     DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B illustrate a vehicle and a wheel end of the vehicle for which the present invention is contemplated 
     FIG. 2 is an enlarged illustration in cross section of the wheel end and components including an annular actuator designed in accordance with the present invention; 
     FIG. 3 is a partial perspective view showing a portion of the annular actuator&#39;s metal ring; and 
     FIG. 4 is a full front view of the metal ring of the annular actuator from the direction of arrow A in FIG. 2 but without the rotary seal. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1A schematically illustrates a vehicle chassis including front wheels  10  as may incorporate the present invention. FIG. 1B is a partial view as taken on view lines  1 B— 1 B of FIG.  1 A and illustrates a front wheel  10  having a hub  12  extended inward where it is supported by a steering knuckle  14 . A bearing pack  16  (See FIG. 2) allows rotation of the wheel  10  relative to the steering knuckle  14 . As noted in FIG. 1B, a drive axle  17  (of the vehicle drive train) connects to a CV-joint  18  which is secured to the knuckle as will be discussed hereafter. As well known to the industry, the CV-joint is adapted to accommodate the pivotal axis  20  of the wheel  10  and knuckle  14  whereby turning of the front wheel is permitted while remaining in driving engagement with the axle  17 . 
     FIG. 2 is an enlarged cross sectional view of the wheel hub  12 , knuckle  14  and CV-joint  18 . As illustrated, the bearing pack  16  is bolted (bolts  22 ) to the knuckle and the wheel hub  12  extends through the inner race  24  of bearing pack  16  with the inboard end  26  roll formed to secure a coupler  28  in abutting engagement with the inner race  24  and thereby the wheel hub  12  in engagement with the bearing pack  16  and knuckle  14 . 
     The CV-joint  18  includes an axle portion  30  that is supported by bearing  32  to the inner side of the hub  12 . The CV-joint is configured to provide an annular portion  34  having splines  36  that are in mating alignment with splines  38  provided on coupler  28 . 
     It will thus be apparent that the CV-joint is rotatably supported in the hub  12  which is rotatably supported in the knuckle  14 . 
     A clutch ring  40  is shown in engagement with both spline sets  36 ,  38  of the CV-joint and the coupler  28 , respectively. In this relation, the CV-joint (driven by axle  17 ) drives the wheel hub  12  and accordingly wheel  10 . The clutch ring  40  is, however, slidable inwardly from the position of FIG. 2 to disengage from the coupler  28  thereby disengaging wheel  10  from the drive axle. Such sliding movement of the clutch ring  40  is provided by the annular actuator  42  parts of which are shown also in FIGS. 3 and 4. 
     The actuator  42  includes a metal annular ring  44  and an opposing elastomeric ring  46  which together define an air chamber  48 . Secured to the elastomeric ring  46  is positioning fork  50  which is engaged with bearing groove  52  of clutch ring  40 . It will be noted that fork  50  does not rotate while the clutch ring does. The arrangement of the fork  50  and clutch ring groove  52  is well known to the industry and accommodates such relative rotation. 
     Forming a part of the metal ring outer exterior is a boss  54 . A passage  58  is provided through the boss and through the metal ring for coupling of air line  56 . The air line  56  is connected at its other end to an intake manifold of the vehicle&#39;s engine (not shown) to produce a negative air pressure in the chamber  48 . When actuated, the negative air pressure draws the fork  50  inwardly relative to chamber  48  and the clutch ring  40  accordingly to cause the clutch ring to disengage from the coupler  28  and thus allow free wheeling of wheel  10 . Upon venting of air line  56  to the atmosphere, the air chamber  48  is permitted to expand assisted by a compression spring  49  to return the clutch ring  40  to its engaged position with coupler  28 . 
     As can be seen in FIG. 2, the space or cavity  64  surrounding the clutch ring  40  is sealed off from the surrounding environment. Most notably a rotary seal  60  is carried by the annular actuator  42  and has sealing lips  62  that slidably engage the rotating CV-joint  18  to thereby prevent contaminated air from leaking past the annular ring and into the cavity  64 . 
     As explained in the background of the invention, the cavity  64  as defined by the assembled components including in particular rotary seal  60  is air tight. As this cavity is subjected to pressure variations (due to operating temperatures, elevation and the axial movement of the elastomeric ring  46  which changes the volume in the cavity), the resistance to expansion of chamber  48  varies and this affects the actuating force imparted to the fork  50  and clutch ring  40 . This variation is undesirable and is avoided by providing non-contaminated venting of the cavity  64  as illustrated and which will be now explained. 
     The boss  54  is enlarged sufficiently to accommodate a second passage  66 . This passage is strategically formed to avoid penetration through the metal ring  44  and into the chamber  48 . It is provided to intersect the juncture between the rotary seal  60  and the metal ring  44 . At this intersection, there is a circular groove  68  provided as can also be seen in FIGS. 3 and 4. This groove  68  enables air access through passage  66  to the groove  68  which encircles the outer side of ring  44  and is positioned behind rotary seal  60 . A plurality of slots  70  extends from the groove  68  to a position behind and under the rotary seal  60 . As will be apparent, this position is within the cavity  64 . An air line  72  is connected to passage  66  and is extended (preferably coupled to and in parallel with line  56 ) to a location where the opposite end of line  72  is open to non-contaminated air. 
     This invention has solved a perplexing problem of clutch ring actuation by providing a contaminant free environment for clutch ring actuation while avoiding the affect of air pressure variation. Those skilled in the art will likely conceive of variations or modifications to the disclosed embodiment while utilizing the disclosed inventive precepts to achieve the above-described venting. Accordingly, the claims are not to be limited to the above disclosure and are intended to apply broadly to all structures encompassed by a fair and broad interpretation of the terms set forth in the claims.