Abstract:
A universal joint assembly includes a universal joint and a housing encasing the universal joint. An isolator encases the housing. The isolator includes at least one chamber formed therein. The housing is moveable relative to the isolator by compression of the isolator.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to universal joint assemblies and more particularly to a tunable rubber isolated bipod universal joint assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     The use of universal joints in automotive systems is common within the industry. Universal joints transmit constant torque through an angle between two shafts. However, it is important to reduce any noise or vibrations through the joint that may cause damage or annoyance during operation. Accordingly, isolators have been used to encase the universal joint. The isolators have typically been made from elastomeric materials that elastically deform as the universal joint moves relative to a housing surrounding the joint. In this way, the isolator absorbs a portion of the vibrations transmitted through the universal joint. While these isolators have been successful for their intended purpose, there is room in the art for improvements.  
       SUMMARY OF THE INVENTION  
       [0003]     A universal joint assembly is provided. The assembly includes a universal joint and a housing encasing the universal joint. An isolator encases the housing. The isolator includes at least one chamber formed therein for defining a stiffness of the isolator. The housing is moveable relative to the isolator by compression of the isolator. The stiffness of the isolator is tunable by modifying the characteristics of the chamber.  
         [0004]     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  
       [0005]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0006]      FIG. 1A  is a front sectional view of a universal joint assembly constructed according to the principles of the present invention;  
         [0007]      FIG. 1B  is a side sectional view of universal joint assembly of the present invention;  
         [0008]      FIG. 2  is a front view of a tunable isolation member constructed according to the principles of the present invention; and  
         [0009]      FIG. 3  is a front view of a housing member constructed according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]     With reference to  FIGS. 1A and 1B , a bipod universal joint assembly constructed according to the principles of the present invention is generally indicated by reference numeral  10 . The assembly  10  includes a bipod universal joint  12 , a bipod housing  14 , an tunable isolator  16 , and a housing  18 . In the particular example provided, the assembly  10  is used in operative association with an automotive driveshaft. However, it should be appreciated that the assembly  10  may be used in various other environments requiring torque to be transmitted through an angle.  
         [0011]     The bipod universal joint  12  includes a spider  20  having a central hub  22  and a pair of trunnions  24  extending from opposite sides thereof. The hub  22  is coupled to a stub shaft  26  which defines a horizontal axis  23 . The stub shaft  26  is in turn coupled to a conventional driveshaft tube (not shown). The trunnions  24  are generally cylindrical in shape and include spherical ends  28 . The trunnions  24  define a vertical axis  25 .  
         [0012]     The bipod universal joint  12  further includes a pair of rollers  30 . The rollers  30  are coupled to the trunnions  24  of the spider  20 . In the example provided, the rollers  30  have a truncated spherical outer shape and a cylindrical inner bore  32 . The cylindrical inner bore  32  includes a plurality of needles (not shown) along its inner circumference. Each roller  30  is fitted overtop a trunnion  24  such that the trunnion  24  fits within the cylindrical inner bore  32 . The rollers  30  are able to move up and down relative to the trunnions  24  along the axis  25  and are able to rotate relative to the spider  20 .  
         [0013]     The bipod housing  14  encases the bipod universal joint  12 . In the example provided, the bipod housing  14  includes a body  34  having an inner cavity  36  sized to receive the bipod universal joint  12  therein. The inner cavity  36  includes top and bottom cylindrical tracks  38  formed therein. The top and bottom cylindrical tracks  38  are sized to constrain the spherical ends  28  of the trunnions of the spider  20  therein. The inner cavity  36  further includes roller tracks  40  formed therein. The roller tracks  40  are generally cylindrical in shape and are sized to receive the rollers  30  therein. The roller tracks  40  prevent the rollers  30  from rotating relative to the bipod housing  14  while simultaneously allowing the rollers  30  (and therefore the entire universal joint  12 ) to move along the axis  23 . The bipod universal joint  12  in conjunction with the bipod housing  14  allow torque to be transmitted through the universal joint  12  at an angle and on to a driveshaft (not shown) of the motor vehicle (not shown).  
         [0014]     The tunable isolator  16  encases the bipod housing  14 . In the particular example provided, the tunable isolator  16  is made from rubber. However, it is to be appreciated that any elastomeric material may be employed with the present invention. Turning to  FIG. 2 , the tunable isolator  16  includes an inner socket  42  that is shaped to match the outer contour of the bipod housing  14  ( FIG. 1 ). In the particular example provided, the tunable isolator  16  includes vertical wings  44  and horizontal wings  46 . The vertical wings  44  extend generally vertically and the horizontal wings  46  extend generally horizontally. The wings  44 ,  46  are adapted to engage the housing  18 .  
         [0015]     Each vertical wing  44  may include a first chamber  48  and a second chamber  50 . The first and second chambers  48 ,  50  may extend throughout the length of the tunable isolator  16  along the axis  23 . In the particular example provided, the first and second chambers  48 ,  50  have an oval cross sectional shape. Moreover, the first chambers  48  are larger than the second chambers  50  and may be formed in the tunable isolator  16  at a location that is relatively closer to the inner socket  42 . The horizontal wings  46  may each include a third chamber  52 . The third chambers  52  may extend throughout the length of the tunable isolator  16  along the axis  23 . The third chambers  52  are preferably larger than the first and second chambers  48 ,  50 . The first, second, and third chambers  48 ,  50 ,  52  allow the elastomeric material of the tunable isolator  16  to compress and deflect to a greater extent (thereby partially defining the stiffness of the tunable isolator  16 ). It is to be appreciated that the shape, size, and location of the chambers  48 ,  50 , and  52  within the tunable isolator  16  may be varied without departing from the scope of the present invention. Moreover, the tunable isolator  16  may include a number of chambers greater than or fewer than those illustrated and may include none of the chambers without departing from the scope of the present invention. By adjusting the properties of the chambers  48 ,  50 ,  52 , the tunable isolator  16  is easily “tunable” to provide any desired stiffness.  
         [0016]     Turning back to  FIG. 1 , the housing  18  receives the tunable isolator  16  and is coupled to a source of torque, such as, for example, an engine (not shown). More specifically, the housing  18  includes a control bore  53 , which is sized to receive the tunable isolator  16 , the bipod housing  14  and the bipod universal joint  12 , and a plurality of drive tabs  55  that extend inwardly into the central bore  53  and drivingly engage the tunable isolator  16 . Accordingly, drive torque that is transmitted between the housing  18  and the stub shaft  26  (or vice versa) is transmitted through the tunable isolater  16 . The tunable isolator  16  allows the bipod universal joint  12  and bipod housing  14  to move relative to the housing  18  by compression and elastic deformation of the tunable isolator  16 . The stiffness of the tunable isolator  16  is determined by its geometry and material characteristics and may be designed to affect the torsional compliance of the assembly  10  in any manner desired. In the example provided, this designing or “tuning” is accomplished by adjusting the properties of the chambers  48 ,  50 ,  52 .  
         [0017]     With reference to  FIG. 3 , an alternate embodiment of the bipod housing  14  is generally indicated by reference numeral  14 ′. The bipod housing  14 ′ includes a plurality of plates  54  integrated with a plastic body  56 . The plates  54  may be formed of sheet steel in an appropriate process, such as stamping, though various other materials and forming processes may be employed. Additionally, the plates  50  may be heat treated and/or coated with an appropriate coating (e.g., for lubricity, corrosion, resistance and/or wear resistance). The plates  54  form the contact surfaces for the rollers  30  and the spherical ends  28  of the trunnions  24  of the spider  20  (see  FIGS. 1A, 1B ). In the example provided, there are six plates  54 , each corresponding to a point of contact with the universal joint  12 . The plastic body  56  is preferably a high strength thermosetting plastic which may be injected into a hold (not shown) that carries the plates  54 , though various other materials may be employed. Torque transmission through the bipod housing  14 ′ puts the plastic body  56  primarily under compression between the tunable isolator  16  ( FIGS. 1A, 1B ) and the rollers  30  of the universal joint  12 .  
         [0018]     Preferably, the plates  54  are positioned during or prior to molding of the plastic body  56 . This allows the plates  54  to be precisely positioned relative to the rollers  30  and trunnions  24 . Moreover, the plastic body  56  is relatively less expensive to manufacture and is of lighter weight than a full steel body, while the plates  54  assure that the bipod housing  14 ′ has suitable strength and durability.  
         [0019]     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.