Abstract:
A wheel hub assembly is provided including a movable clutch ring for selective engagement between an engaged and disengaged position for providing driving torque from an axle shaft to a wheel hub. The clutch ring is in full-time engagement with external clutch teeth of the axle shaft and is movable to an engaged position with external clutch teeth of a coupler that is secured to the wheel hub. Furthermore, the coupler is provided with a travel limiter for preventing the clutch ring from traveling beyond a predetermined desired position along the coupler.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an actuator for initiating the shifting action of a clutch to affect engagement/disengagement of drive and driven shafts.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     In recent years it has become increasingly popular to provide vehicles with the ability to convert between two-wheel and four-wheel drive. As popularity has grown, so to have the many ways of affecting conversion. In one example there is a permanently driven drive line segment to the rear wheels of a vehicle, and a part-time driven drive line segment to the front wheels. The part-time driven drive line segment is simply disconnected/decoupled from the engine&#39;s drive shaft at the transmission or transfer case and that segment is rendered passive (undriven).  
         [0003]     There is often a second point of disconnection which may be at or near the differential (a center disconnect) or at both wheels. There is a mechanical action that takes place to achieve each connection and disconnection as contemplated herein. Two shafts or drive line segments are in close relationship and a clutch ring that is permanently coupled to one shaft is slidable into engagement with the other shaft to couple the shafts and is slidable out of engagement with other shaft to decouple the two shafts.  
         [0004]     The sliding movement is achieved by what will here be referred to as an actuator. The actuator can be many types including, e.g., a shift lever, manual or electrically driven, it can be cam actuated and it can be pneumatically actuated.  
         [0005]     Pneumatic actuators in general are not new. Pneumatic actuators of this kind are disclosed in commonly assigned U.S. Pat. Nos. 5,704,895; 6,109,411 and 6,234,289. In the above listed patents, the clutch ring and components to be coupled are rotating and the annular actuator is designed to shift a non-rotating member (referred to as a fork) that is placed in contact with the rotating clutch ring. The contact between the rotating clutch ring and fork is designed to form a bearing that permits rotation of the clutch ring while the entire actuator remains static. The annular configuration of the actuator which surrounds the juncture to be coupled enables the use of a greater surface area on which the air acts. Thus, the available air pressure (from the manifold) is being applied to the greater surface area and produces a greater accumulated force. The diaphragm that is used as the movable wall is made of material that conforms and seals against metal objects. Placing the diaphragm in an opening that needs otherwise to be sealed allows the diaphragm to serve dual purposes.  
         [0006]     Having thus achieved a far more efficient air actuated clutch ring actuator, all or most of the actuators heretofore provided along the drive line are advantageously replaced with the annular actuator of the patented designs.  
         [0007]     Even with the improved performance and efficiency of the air actuated clutch ring actuator, additional improvements in the manufacture and assembly of the hub assembly have been developed. In particular, the present invention provides a clutch ring travel limiter to reduce the risk of damage to the shift fork during assembly of the half shaft to the wheel end. Additionally, a coupler is secured to the wheel hub by roll-forming the inboard end of the wheel hub around the coupler.  
         [0008]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a perspective view of an annular actuator of the present invention;  
         [0011]      FIG. 2  is an exploded view of the annular actuator of  FIG. 1 ;  
         [0012]      FIG. 3  is a cross sectional view of the annular actuator of  FIG. 1  as applied to a wheel hub showing the engaged position;  
         [0013]      FIG. 4  is a view similar to  FIG. 3  but showing the disengaged position;  
         [0014]      FIG. 5  is a detailed cross-sectional view of an alternative coupler design,  
         [0015]      FIG. 6  is a detailed cross-sectional view of a second alternative coupler design, and  
         [0016]      FIG. 7  is a detailed cross-sectional view of a third alternative coupler design. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0018]      FIGS. 1-4  illustrate one embodiment of an annular actuator  10  of the present invention. Referring to  FIGS. 1 and 2 , the actuator  10  has a housing  12  that is arranged to be fixedly mounted in a non-rotative manner. The actuator  10  is circular in configuration and has a center opening (bore)  14 . A defined gas chamber  22  (best shown in  FIG. 3 ) is formed within the housing  12  including a pliable diaphragm  40  which defines a movable wall of the chamber  22 . The diaphragm  40  is biased axially outwardly by a biasing member such as a spring  30  which expands the chamber  22 . The diaphragm  40  is moved axially inwardly by withdrawing a media from the defined chamber  22  which contracts the chamber against the biasing force of the spring  30 .  
         [0019]     Referring now to the exploded view of  FIG. 2 , the housing  12  of the actuator  10  is preferably molded and is circular in configuration resembling a ring like structure. The housing  12  has its center opening  14  defined by an inner wall  18  extending from a base portion  20 . An outer circular wall  16  also extends from the base portion  20  in combination with the inner wall  18  and the base portion  20  define the fixed wall portion of the interior vacuum or gas chamber (cavity)  22 .  
         [0020]     The outer surface of the wall  16  typically has a slight taper resulting from the molding operation. A port  24  communicates with the chamber  22  and is provided to input or exhaust air from the defined chamber  22 . As shown in the figure, the outer wall  16  extends from the base portion  20  a slightly greater distance than the inner wall  18 . Projecting tabs  29  are provided to facilitate mounting the housing  12  to a member of a vehicle chassis, although other mounting arrangements are clearly possible.  
         [0021]     A spring  30  is sized to fit within the chamber  22  between the walls  18  and  16  with one end of the spring  30  being in abutment with the base portion  20  of the housing  12 . A piston  34  that is ring like in structure abuts the spring  30  when the components of the actuator  10  are assembled. The piston  34  is placed on an opposite side of the diaphragm  40  from a shifting fork  68  as will be later explained.  
         [0022]     The elastomeric pliable diaphragm  40  is configured to fit the housing  12  of the actuator  10 . A rim  42  of the diaphragm  40  is sized to fit within the bore  14  (fitted against wall  18 ) of the housing  12 . The rim  42  is reinforced by a metallic ring  44  (best shown in  FIG. 4 ) that is molded integral with the rim  42 . Upon installation, the rim  42  is press fit into the bore  14  which provides a seal (between the wall  18  and the diaphragm  40 ) to seal the chamber  22  of the housing  12 . The end of the ring  44  may be swaged over (see  FIG. 3 ) to assure retention of the rim  42  in the bore  14 . The outer diameter  50  of the diaphragm  40  has a projecting bead  52  formed around its periphery. A ring  54  molded integral with the diaphragm  40  ( FIG. 3 ) supports the bead  52  and acts as a compression member to compress the bead  52  against the outer surface of the housing  12  upon installation. When the diaphragm  40  is installed on the housing  12 , the bead  52  will be in compressive contact with the outer surface of the wall  16  which provides a seal (between the wall  16  and the bead  52  of the diaphragm  40 ) to seal the chamber  22  of the housing  12 . A base portion  56  of the diaphragm  40  is secured to the piston  34 .  
         [0023]     A peripheral ultrasonic weld is provided between the circular shifting fork  68  and the piston  34  with the diaphragm  40  sandwiched in between. The fork  68  has a projecting L-shaped arcuate section  74  extending from the base portion  69  that is configured to reside in a groove  82  of a clutch ring  80 .  
         [0024]     The circular clutch ring  80  has a peripheral groove  82  that receives the L-shaped section  74  of the shifting fork  68 . The groove  82  and the formed section  74  provide a bearing section such that the clutch ring  80  may rotate relative to the shifting fork  68 . The clutch ring  80  has internal clutch teeth  84  that are matable with clutch teeth of a drive and driven member of a vehicle.  
         [0025]      FIGS. 3 and 4  of the drawings illustrate the annular actuator applied to a wheel hub. The housing  12  of the actuator is fixedly mounted to a knuckle  100  of the vehicle. An air line  102  is coupled to the port  24  of the housing  12  with the air line  102  being connected to an air source such as an intake manifold. The actuator is assembled as previously described with the clutch ring  80  being rotatable relative to the fork  68 . As shown, the L-shaped section  74  of the fork  68  fits in the groove  82  of the clutch ring  80 . The internal clutch teeth  84  of the clutch ring  80  are permanently engaged with clutch teeth  106  on axle shaft  108 . A coupler  112  having internal splines  113  is mounted on the wheel hub spindle  116  with the internal splines  113  of the coupler  112  being mated with the external splines  114  of the wheel hub spindle  116 . The coupler  112  has external clutch teeth  118  that are alignable with the clutch teeth  106  of the axle shaft  108 . The coupler  112  being in splined engagement with the hub spindle  116  rotates with the hub spindle  116 . The end  119  of the hub spindle  116  is roll formed around the inboard edge of the coupler  112 .  
         [0026]     The coupler  112  is provided with an outside diameter ring  124  to limit the clutch ring  80  travel relative to the coupler  122 . The outside diameter ring  124  provides a supplemental stop against which the clutch ring  80  can abut during installation of the half shaft  108 . Specifically, as the hub assembly is being assembled to the half shaft  108 , the clutch teeth  84 ,  119  of the clutch ring  80  and coupler  122 , respectively, are aligned but the half shaft clutch teeth  106  may be out of alignment with the internal clutch teeth  84  of the clutch ring  80 . In this instance, the forces applied to the clutch ring  80  by the half shaft  108  would have a tendency to press against the ends of the splines  84  of the clutch ring  80  while the base portion  69  of the shift fork  68  is in abutting relationship with the knuckle  100 . Since the base portion  69  is pressed against the knuckle  100 , forces applied to the clutch ring  80  might impart undesirable forces on the L-shaped section  74  of the shifting fork  68  that can potentially cause breakage or cracking of the shift fork  68  during installation. Thus, the travel limiter ring  124  prohibits the clutch ring  80  from applying undesirable forces on the shift fork  68  during installation and alignment of the clutch teeth  106  of the half shaft  108  with the internal clutch teeth  84  of the clutch ring  80 . The travel limiter ring  124  can also function as the travel limiter during normal actuation.  
         [0027]     It is anticipated that the travel limiter  124  can take on several forms. In particular, as shown in  FIGS. 3 and 4 , the outside diameter of the coupler  112  is provided with a recessed portion  126  and a separate ring member  128  is received in the recessed groove to provide a travel limiter against which the clutch ring  80  is abutted. It is noted that in order to reduce the size and weight of the clutch ring  80 , the clutch ring  80  has a smaller outside diameter than the inside diameter of the knuckle  100 , so that the knuckle  100  does not serve as a stop for the clutch ring  80 , but may serve as a stop for the base portion  69  of the shift fork  68  as shown.  
         [0028]     Alternative designs of the travel limiter are illustrated in  FIGS. 5-7 . In the embodiment shown in  FIG. 5 , the travel limiter  124 ′ is integrally formed with the coupler  112 ′ and has a radially outwardly extending portion  130  against which the clutch ring  80  abuts prior to exceeding the desired range of motion of the clutch ring  80 .  
         [0029]     As illustrated in  FIG. 6 , the external clutch teeth  118 ″ of the coupler  112 ″ have a closed end portion  134  against which the end of the internal clutch teeth  84  of the clutch ring  80  abut in order to limit axial movement of the clutch ring  80  relative to the coupler  112 ″ beyond a predetermined desired position to thereby prevent excessive forces from being applied to the shift fork  68  during installation of the hub assembly to the axle shaft  108 .  
         [0030]     In yet another embodiment, as shown in  FIG. 7 , the clutch teeth  118 ′″ of the coupler  112 ′″ extend across the outer diameter of the coupler  112 ′″ and a radially outwardly extending shoulder portion  142  extends radially outward such that the clutch ring  80  abuts the shoulder portion  142  for preventing further movement of the clutch ring  80  relative to the coupler beyond a predetermined desired distance. The shape of the clutch teeth  118 ′″ extending across the outer diameter of the coupler  112 ′″ allows for easier forming of the external clutch teeth  118 ′″.  
         [0031]     The spring  30  of the actuator is captive between the base  20  and the piston  34  and urges the assembly of the piston  34 , diaphragm  40  and fork  68  to move axially away from the base  20  of the housing  12 . The spring  30  moves the clutch ring  80  axially along the clutch teeth  106  of the axle  108  and will urge the clutch ring  80  into engagement with the clutch teeth  118  of the coupler  112 . Thus, the spring force positions the clutch ring  80  in engagement with both the axle  108  and the coupler  112  ( FIG. 3 ) and since the coupler  112  is in splined engagement with the hub spindle  116 , the hub spindle  116  rotates with the axle  108 . During normal actuation in the assembled condition, the knuckle  100  provides a travel limiter function to limit the travel of the fork  68  and clutch ring  80 .  
         [0032]     When air is withdrawn from the housing  12  via port  24 , negative air (vacuum) pressure generated within the chamber  22  of the housing  12  will force the assembly of the piston  34 , the diaphragm  40  and the fork  68  toward the base  20  of the housing  12 . Negative air pressure is sufficient to compress the spring  30  and thus the clutch ring  80  will be moved out of engagement with the coupler  112  to be only engaged with the axle  108  as shown in  FIG. 4 .  
         [0033]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.