Abstract:
A joint operable to couple a first shaft to a second shaft includes a first yoke coupled to the first shalt and defining a first aperture. A second yoke is coupled to the second shaft and defines a second aperture. A first bearing is coupled to the first yoke and is at least partially disposed within the first aperture. A second bearing is coupled to the second yoke and is at least partially disposed within the second aperture. A cross member has a first boss coupled to the first bearing and a second boss coupled to the second bearing. A first resilient member is positioned between the first bearing and the first boss to interconnect the first boss and the first yoke, and a second resilient member is positioned between the second bearing and the second boss to interconnect the second boss and the second yoke.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. §119 to provisional patent application No. 60/724,737, filed on Oct. 7, 2005, which is hereby fully incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     The present invention relates to a universal joint (U-joint). More particularly, the invention relates to a U-joint that includes vibration isolation.  
         [0003]     Universal joints, commonly referred to as U-joints are often used to connect two rotating shafts that are not aligned on a common axis. The U-joint allows each shaft to rotate about its axis without excessive friction or variation in rotational forces throughout the rotation.  
         [0004]     Applications that commonly employ a U-joint include rack-and-pinion and recirculating-ball steering systems, including direct (manual) and hydraulic and electric power steering. Many automobiles employ steering systems that includes one or more U-joints. In automobile applications, the design of the steering system and the U-joint can affect the overall noise, vibration, and handling of the vehicle.  
         [0005]     At present, steering systems generally employ a flexible disk coupling or a bushing style isolator that partially isolates the front wheels from the steering wheel. Thus, many of the vibrations and forces applied to the front wheels of the vehicle or generated by the power steering system are not transferred through the steering wheel to the driver&#39;s hands. However, the amount of isolation provided can adversely affect the handling of the vehicle. As such, the design of the system should account for vibration, noise, and handling.  
       SUMMARY  
       [0006]     The present invention provides a U-joint that includes a first yoke and a second yoke interconnected by a cross member. The cross member includes four trunions with a trunion end coupled to each trunion. Each trunion end includes a resilient member coupled to a trunion boss, an inner cap covering the resilient member, and an outer cup. A bearing is disposed between the inner cap and the outer cup such that the trunion is rotatable relative to the yoke.  
         [0007]     In one embodiment, the invention provides a joint operable to couple a first shaft to a second shaft. The joint includes a first yoke coupled to the first shaft and defining a first aperture, a second yoke coupled to the second shaft and defining a second aperture, and a first bearing coupled to the first yoke and at least partially disposed within the first aperture. A second bearing is coupled to the second yoke and is at least partially disposed within the second aperture. A cross member has a first boss coupled to the first bearing and a second boss coupled to the second bearing. A first resilient member is positioned between the first bearing and the first boss to interconnect the first boss and the first yoke, and a second resilient member is positioned between the second bearing and the second boss to interconnect the second boss and the second yoke.  
         [0008]     In another embodiment, the invention provides a joint operable to couple a first shaft to a second shaft. The joint includes a first yoke coupled to the first shaft, a second yoke coupled to the second shaft, and a cross member that includes a first trunion and a second trunion. The second trunion is engageable with the second yoke. A first resilient member has an inner surface sized to closely fit the first trunion and an outer surface. A first inner cap has an inner cap surface sized to closely fit the outer surface of the first resilient member and a cap outer surface engageable with the first yoke.  
         [0009]     In another embodiment, the invention provides a joint that is operable to couple a first shaft to a second shaft. The joint includes a first yoke coupled to the first shaft, a second yoke coupled to the second shaft, and a cross member that includes a first trunion and a second trunion. The second trunion is engageable with the second yoke. A first resilient member at least partially covers the first trunion and a first inner cap at least partially covers the first resilient member. A first outer cup at least partially covers the first inner cap and is engageable with the first yoke. A first leg is formed as part of and extends from the first resilient member. The leg is positioned such that a portion of the leg is disposed outside of the first outer cup. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a portion of a rack and pinion steering system including a U-joint;  
         [0011]      FIG. 2  is an exploded view of the U-joint of  FIG. 1 ;  
         [0012]      FIG. 3  is a schematic section view of the U-joint of  FIG. 1  taken along line  3 - 3  of  FIG. 2 ; and  
         [0013]      FIG. 4  is an enlarged view of a trunion end of the U-joint of  FIG. 1 ;  
         [0014]      FIG. 5  is an enlarged view of a portion of the trunion end of  FIG. 4 ; and  
         [0015]      FIG. 6  is an enlarged view of a portion of another trunion including a lip seal. 
     
    
     DETAILED DESCRIPTION  
       [0016]     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
         [0017]      FIG. 1  illustrates a portion of one possible steering mechanism  10  that includes a U-joint  15  and is suited for use in converting rotary motion to linear motion. In a typical application, the linear motion is used to turn a pair of turnable wheels on a vehicle such as an automobile. The steering system  10  includes a steering wheel  20  that is coupled to a steering shaft  25  such that rotation of the steering wheel  20  produces a corresponding rotation of the steering shaft  25 . The steering shaft  25  generally extends downwardly and forwardly from the steering wheel  20 .  
         [0018]     The steering mechanism  10  also includes a rack-and-pinion arrangement  30 . A rack  35  extends between the turnable wheels of the vehicle and moves along a substantially linear path  37  in response to rotation of the steering wheel  20 . The rack  35  includes a plurality of teeth  40  that extend outwardly from a substantially planar surface. The teeth  40  are spaced apart from one another to define a plurality of channels that extend in a direction that is substantially normal to the direction of movement  37  of the rack  35 . Of course other rack designs may employ differently arranged teeth as may be desired for the particular application.  
         [0019]     A pinion  45  includes a plurality of teeth  50  that are sized and pitched to substantially match the teeth  40  of the rack  35 . A pinion shaft  55  supports the pinion  45  in an engaged position such that rotation of the pinion  45  produces a corresponding linear movement of the rack  35 . In most applications, the pinion shaft  55  resides in substantially the same plane as the rack  35  and is oriented such that the pinion shaft  55  is normal to the direction of movement  37  of the rack  35 . With this arrangement, the pinion shaft  55  is not parallel to the steering shaft  25 . As such, the U-joint  15  interconnects the steering shaft  25  and the pinion shaft  55  such that rotation of the steering shaft  25  produces a corresponding rotation of the pinion shaft  55  and the pinion  45  to produce the desired linear movement of the rack  35  to turn the wheels of the vehicle.  
         [0020]     It should be noted that many other steering systems that employ one or more U-joints  15  are possible. As such, the invention should no be limited to steering systems similar to the simple rack-and-pinion system  10  illustrated herein. For example, steering systems may employ multiple shafts with multiple U-joints that allow the shaft to move around multiple objects that impede the straight path. In addition, many steering systems are far more complex than the one illustrated. For example, a hydraulic steering system includes a valve that is moved by the shaft to actuate the power steering mechanism and turn the vehicle. Furthermore, U-joints  15  can also be used in applications other than steering systems. For example, an automobile drive shaft o ten includes one or more U-joints and may be a suitable application for the invention. As such, the invention should not be limited to steering system applications alone.  
         [0021]     The U-joint  15 , illustrated in  FIGS. 2 and 3  includes a cross member  60 , a first yoke  65 , and a second yoke  70 . The cross member  60  includes four trunions that are equally spaced around an axis. As illustrated in  FIGS. 2 and 3 , a first trunion  75  is at the twelve o&#39;clock position, a second trunion  80  is at the three o&#39;clock position, a third trunion  85  is at the six o&#39;clock position, and a fourth trunion  90  is at the nine o&#39;clock position. However, these orientations are given for discussion purposes only, as the invention is not limited to these orientations. Trunion ends  95  are coupled to, or formed as part of, each trunion  75 ,  80 ,  85 ,  90  as will be described in greater detail with regard to  FIGS. 4 and 5 .  
         [0022]     Each yoke  65 ,  70  attaches to, or is formed as part of, one of the steering shaft  25  and the pinion shaft  55  and includes two ears  100  that extend along the axis of the respective shaft  25 ,  55 . Of course, the yokes  65 ,  70  could alternatively be formed on or attached to other shafts in the steering linkage. The two ears  100  of each yoke  65 ,  70  are spaced apart from one another to define a substantially U-shaped space  102 . Ear apertures  105  are formed in each of the yoke ears  100  to receive the trunions ends  95 . As illustrated in  FIG. 2 , the ear apertures  105  of the first yoke  65  are formed along a first axis  110  and receive the ends of the first trunion  75  and the third trunion  85 , while the ear apertures  105  of the second yoke  70  are formed along a second axis  115 , generally perpendicular to the first axis  110 , and receive the ends of the second trunion  80  and the fourth trunion  90 . In some constructions, the ear apertures  105  are blind holes as illustrated in  FIG. 2 , while other constructions may employ through holes. The actual arrangement of the ear apertures  105  is not critical to the function of the invention so long as they are properly sized to receive the trunion ends  95 .  
         [0023]     Turning to  FIGS. 4 and 5 , one of the trunion ends  95  is shown in greater detail. The trunion end  95  includes a resilient member  120 , an inner cap  125 , and a bearing  135  that includes an outer cup  130  and a seal  140 . Each trunion defines a substantially cylindrical boss  145  that receives the resilient member  120 . As shown in  FIG. 4 , the resilient member  120  is substantially cup-shaped with an inner surface  150  that closely fits the surface of the boss  145 . The resilient member  120  includes a substantially cylindrical outer surface  155  on which are disposed several ribs  160 . Each rib  160  extends around the circumference of the resilient member  120  and is substantially semi-circular in cross section, with other cross sections also being possible. In the illustrated construction, five ribs  160  are employed with more or fewer ribs  160  also being possible. In other constructions, ribs are positioned on the inner surface  150  rather than the outer surface  155 .  
         [0024]     The resilient member  120  can be formed using a resilient or elastomeric material such as urethane, with other materials also being suitable for use (e.g., polyurethane, plastic, natural rubber, nitrile, silicone, synthetic rubber, cork, and the like). Thus, various resilient members made of various materials having different properties are possible. For example, soft rubber may be employed where high resilience is required, while hard plastic or another less resilient material may be employed in applications that require less resilience. As one of ordinary skill will realize, many different materials may be suited for use in manufacturing resilient members  120 . As such, the invention should not be limited to the materials listed herein.  
         [0025]     The inner cap  125  is also substantially cup-shaped and defines an inner cylindrical surface  165  and an inner race surface  170 . The inner cylindrical surface  165  is sized to closely fit over the ribs  160  of the resilient member  120 . In the illustrated construction, a small press fit or interference fit is established between the inner cap  125  and the ribs  160 . The ribs  160  reduce the total surface area that must be compressed during the installation of the inner cap  125 . Thus, the ribs  160  serve to increase the effective resilience of the resilient member  120  as it is compressed, thereby making it easier to install the inner cap  125  over the resilient member  120 . However, as the amount of compression increases, a greater amount of surface area must be compressed, thus reducing the effective resilience of the resilient member  120 . As such, the shape, size, quantity, and arrangement of the ribs  160  can be varied to vary the effective resilience of the resilient member  120 . The inner race surface  170  is substantially smooth and defines an inner race for the bearing  135  as discussed below. In the illustrated construction, the inner cap  125  is manufactured from a steel material (e.g., carbon steel, stainless steel, etc.). However, other materials may also be suitable for use in manufacturing the inner cap  125  (e.g., brass, bronze, iron, ceramic, composite, plastic, etc.).  
         [0026]     The outer cup  130  includes a cylindrical wall that defines an outer race  175  and an outer cylindrical surface  180 . The outer race  175  is a substantially smooth cylindrical surface that defines the innermost surface of the outer cup  130  and serves as the outer race for the bearing  135 . The outer cylindrical surface  180  is sized to fit within the ear aperture  105  of one of the yoke ears  100 . In the illustrated construction, an interference or press fit is established between the ear aperture  105  and the outer cylindrical surface  180  such that no additional components are needed to hold the outer cylindrical surface  180  within the ear aperture  105 . However, in some applications is may be desired to provide for serviceability of the bearings and cross member. In these constructions, a looser fit is employed with a locking member (e.g., snap rings, and the like) retaining the outer cup in the desired position.  
         [0027]     The outer cup  130  also includes two walls that are substantially normal to the outer cylindrical surface  180 . A first wall  185  spans the entire area defined by the outer cylindrical surface  180  and defines an end. In constructions in which the ear apertures  105  are blind holes, the end provides a positive stop when the trunion end  95  or outer cup  130  is inserted into the ear aperture  105 . A second wall  190  extends only partially across the opposite end surface, and as such defines a boss aperture  195  sized to allow for the passage of the boss  145 , resilient member  120 , and inner cap  125 .  
         [0028]     With reference to  FIG. 5 , the bearing  135  includes several needles  200  or rolling elements supported by a cage  205  such that the needles  200  engage the outer race  175  and the inner race surface  170  to allow the inner cap  125  to rotate with respect to the outer cup  130  about the ear aperture axis  110  or  115  with little resistance. As is well known in the art, the needles  200  of the bearing  135  are supported by a cage  205  in a manner that maintains their spacing and allows them to rotate around axes that are substantially parallel to the ear aperture axis  110  or  115 . The outer race surface  175 , the inner race surface  170 , and the needles  200  are sized to provide a tight fit between the three components when assembled. The tight fit reduces unwanted play between the components and aids in maintaining the position of the needles  299  within the outer cup  130 .  
         [0029]     Before proceeding, it should be noted that while a bearing  135  is shown and described, other types of bearings are also suitable for use. For example, other constructions may employ needle bearings with a full complement of needles (no cage) or other bearings or roller elements such as, but not limited to roller bearings, ball bearings, taper bearings, journal bearings or the like, rather than needle bearings. As such, the invention should not be limited to needle bearings alone.  
         [0030]     The seal  140  is an annular resilient member that fits between the outer cup  130  and the inner cap  125  and inhibits movement of matter between the bearing  135  and the exterior of the outer cup  130 . As illustrated in  FIG. 5 , the outer cup includes a lip or shoulder  210  that supports the seal  140  between the bearing  135  and the boss aperture  195 . In most constructions, the space occupied by the bearing  135  is also filled with a lubricant, such as grease. The seal  140  inhibits the loss of the grease and also reduces the likelihood of dirt, rocks, pebbles, chips, or other debris entering the grease. In preferred constructions, the seal  140  is larger than the space into which it fits such that it is slightly compressed during assembly. In addition, the use of a press fit between the outer cup  130  and the ear aperture  105  further compresses the seal  140  as the outer Cup  130  displaces during installation. The compression of the seal  140  serves to maintain the position of the seal  140  within the outer cup  130  and enhances the performance of the seal  140 .  
         [0031]     To assemble each trunion end  95 , the resilient member  120  is placed over the boss  145  In some constructions one of, or both of, the boss  145  and the inner surface  150  of the resilient member  120  may be roughened or contoured to improve the engagement between the boss  145  and the resilient member  120 . Furthermore, some constructions may employ an adhesive to further enhance the bond between the resilient member  120  and the boss  145 . The inner cap  125  is then positioned on top of the resilient member  120 . As discussed, a slight interference lit between the resilient member  120  and the inner cap  125  is desirable. Thus, the friction between the two components is generally sufficient to maintain the position of the inner cap  125 . However, in some constructions, an adhesive may be used to enhance the connection between the resilient member  120  and the inner cap  125 . The needles  200  and cage  205  are positioned within the outer cup  130  such that the cage  205  contacts the first wall  185 . The seal  140  is then positioned within the outer cup  130  such that it engages the lip  210 . In this position, the seal  140  is between the needles  200  and the boss aperture  195 .  
         [0032]     The outer cup  130 , including the needles  200  and the seal  140 , is then coupled to the trunion end  95 , including the resilient member  120  and the inner cap  125 . The spacing between the inner cap  125  and the outer cup  130  is such that the bearing  135  pushes the inner cap  125  radially and axially inward (toward the center of the boss  145 ), further compressing the resilient member  120 . Thus, the bearing  135  is held firmly in place with little or no unwanted play, and the resilient member  120  is compressively preloaded. In addition, the sizing is such that less restrictive tolerances can be employed during the manufacture of the resilient member  120 , the inner cap  125 , the needles  200 , and the outer cup  130  as any tolerance stackups are accommodated by the resilient member  120 . Once the trunion ends  95  are assembled onto the cross member  60 , the cross member  60  and yokes  65 ,  70  can be assembled into the completed U-joint  15  as is known in the art. In applications with through hole ear apertures, the resilient member  120  and inner cap  125  are first assembled onto the cross member  60 . The cross member is then positioned within the ear aperture, and the bearing  135  is installed or pressed into the ear aperture such that it also engages the outer cup  125 .  
         [0033]     With reference to  FIG. 1 , the operation of the illustrated steering mechanism  10  employing the U-joint  15  of the invention will be described. As the vehicle passes over a road, the wheels pass over bumps that produce vibrations. The vibrations pass from the wheels to the rack  35  and from the rack  35 , to the pinion  45 . From the pinion, the vibrations pass to the pinion shaft  55 , and to the second yoke  70  attached to the pinion shaft  55 . However, the resilient members  120  within the U-joint  15  absorb many of the vibrations such that they do not pass to the first yoke  65 , the steering shaft  25 , or the steering wheel  20 . Other sources of undesired vibrations, which can be absorbed by the resilient members  120 , include vibrations produced by the engine and power steering system.  
         [0034]     As one of ordinary skill will realize, the level of resilience provided by the resilient members  120  can be varied to accommodate different types of vibrations or larger magnitude vibrations. Generally, more resilient members  120  will isolate more vibrations. However, if the resilient members  120  are too resilient, the steering will feel “soft” and the handling of the vehicle may be adversely affected. As such, the amount of vibration isolation provided by the resilient members  120  should be balanced against the effect the resilient members  120  may have on the handling characteristics of the vehicle.  
         [0035]     Generally, each of the four trunion ends  95  would be similar to the trunion end  95  illustrated in  FIGS. 4 and 5 . However, other constructions may employ two trunion ends  95  that include resilient members  120  and two trunion ends that do not. For example, the first trunion  75  and third trunion  85 , or the second trunion  80  and fourth trunion  90  could include resilient members while the second trunion  80  and fourth trunion  90 , or the first trunion  75  and third trunion  85  do not. Such an arrangement would still provide vibration isolation between the two shafts  25 ,  55  that are coupled by the U-joint  15 .  
         [0036]     The placement of the resilient members  120  adjacent the boss  145  allows the inner cap  125  to substantially cover and protect the resilient member  120 , while simultaneously defining the inner race  170  for the bearing  135 . The only exposed portion of the resilient member  120  is the end. If desired, a face seal (not shown) can be positioned near the exposed end to completely enclose the resilient member  120  and/or to cover the seal  140  and the bearing  135 .  
         [0037]     In another construction, illustrated in  FIG. 6 , a resilient member  300  is formed to also function as the face seal. In this construction, the resilient member  300  includes a leg portion or circumferentail flange  305  that extends substantially normal to the inner surface  150 . The flange  305  extends radially outward and includes an angled portion  310  that contacts or is positioned close to the outer cylindrical surface  180  (i.e., is disposed radially outside of the outer cup  130  of the bearing  135 ). Thus, the resilient member  300  itself substantially encloses the space that includes the bearing  135 .  
         [0038]     The arrangement described herein includes a reduced number of parts compared to prior vibration isolation systems. In addition, the arrangement is simpler than previous arrangements, thereby allowing easier, faster, and more accurate assemblies. By elimination of the extra components of a typical isolation system, the new system is smaller and can better fit into space-restricted applications.  
         [0039]     Furthermore, the system described herein can be easily adapted to different applications with slight changes to the resilient member  120  (e.g., thickness, resilience (durometer), rib orientation, rib spacing, rib quantity, etc.). As such, the U-joint  15  is easily adapted to many different applications, only some of which have been described herein.  
         [0040]     The U-joint  15  described herein provides many advantages over prior vibration isolation systems such as those used in steering systems. For example, the U-joint  15  reduces axial and radial looseness within the steering linkage. The compression of the resilient member in the radial direction by the bearing and the compression of the resilient member in the axial direction by the inner cap take-up excess clearance and reduce the looseness of the steering linkage. The U-joint  15  occupies less space than typical isolator systems and thus also provides for an increased collapse stroke should a crash occur. In addition, the U-joint  15  allows for additional commonization of parts as each steering system design can employ a U-joint  15  that also performs the function of the prior vibration isolation system. In addition, the U-joint bending effort is reduced due to the low compressive stresses of the resilient member  120 .  
         [0041]     Thus, the invention provides, among other things, a new and useful U-joint  15 . More particularly, the invention provides a new and useful U-joint  15  that provides vibration isolation between two shafts  25 ,  55  that may or may not be aligned along a common axis.