Abstract:
A cross for a universal joint in a vehicle driveshaft assembly is comprised of a hollowed block of material having four openings. The hollowed block holds an inner cross that has a first cross member and a second cross member. Each cross member has an end portion that extends through a thrust bearing, and each thrust bearing is engaged with an opening in the hollowed block. The resulting thrust bearing joint can operate at higher loads than conventional cross designs.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates in general to universal joints, such as for use in a vehicle driveshaft assembly. More specifically, this invention relates to an improved structure for a cross for a universal joint capable of withstanding high axial loads.  
         BACKGROUND OF THE INVENTION  
         [0002]    In most land vehicles in use today, a drive train assembly is provided for transmitting rotational power from an output shaft of an transmission to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a typical vehicular drive train assembly includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the transmission and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the transmission through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.  
           [0003]    A typical universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cup having a cylindrical outside wall and a circular end wall is mounted on the end of each of the trunnions. A bearing structure, such as a plurality of needle bearings or roller bearings, is provided between the trunnion and the associated bearing cup to facilitate relative rotational movement therebetween. The bearing cups that are mounted on a first opposed pair of the trunnions can be connected to a first yoke secured to a first component of the drive train assembly, while the bearing cups mounted on a second opposed pair of the trunnions can be connected to a second yoke secured to a second component of the drive shaft assembly.  
           [0004]    When the bearing cups are mounted on the associated trunnions, the circular end walls of the bearing cups are disposed adjacent to the axially outer ends of the trunnions and bearings. If the inner surfaces of these end walls directly contact the axially outer end surfaces of the trunnions during operation, friction caused by such direct contact can generate undesirable heat and wear. However, if the inner end surfaces of the bearing cups do not fit snugly against the axially outer end surfaces of the trunnions, relative axial movement between the bearing cups and the trunnions can cause imbalances and result in undesirable noise and vibrations. Thus, to address these situations, it is known to position a thrust washer between the inner end surface of the bearing cup and the axially outer end surface of the trunnion. A typical thrust washer is formed from a relatively low friction, wear resistant material, such as plastic, that can absorb the thrust loads that occur between the end of the trunnion and the bearing cap and take up any looseness therebetween.  
           [0005]    A thrust washer can absorb some axial load and torque from the vehicle driveline such as that experienced under normal driving conditions. However, a typical Cardan universal joint is not equipped for handling high axial loads and torque. Under high thrust loads, the normal tolerance of a thrust washer will be exceeded, resulting in unacceptable vibrations in the vehicle driveline. In addition, excessive axial loads and torque may cause the ends of a typical cross to flex while placing unacceptable load and torque on the lug structures of the yoke. Thus, it would be desirable to provide an improved structure for a universal joint assembly that addresses these concerns.  
         SUMMARY OF THE INVENTION  
         [0006]    A cross for a universal joint in a vehicle driveshaft assembly is comprised of a hollowed block of material having four openings. The hollowed block holds an inner cross that has a first cross member and a second cross member. Each cross member has an end portion that extends through a thrust bearing, and each thrust bearing is engaged with an opening in the hollowed block. The resulting universal joint can operate at higher loads than conventional cross designs.  
           [0007]    According to this invention there is also provided a cross for a universal joint, suitable for use in a vehicle driveshaft assembly. The cross includes a hollowed block of material having two pairs of opposed openings normal to each other, and an inner cross positioned within the hollowed block. The inner cross has a first cross member and a second cross member positioned normal to each other, the first cross member extending through the first pair of hollowed block openings and the second cross member extending through the second pair of hollowed block openings. The cross members pass through a thrust bearing at each of the hollowed block openings, the thrust bearings are positioned within the openings.  
           [0008]    According to this invention there is also provided a cross for a universal joint, suitable for use in a vehicle driveshaft assembly. The cross includes an inner cross having a first bore and a second bore formed therethrough, the first bore and second bore extending through the inner cross at right angles relative to one another. First and second bolts are threaded into opposing sides of the first bore, the first and second bolt securing a first pair of thrust bearings to the inner cross. A third bolt passes through the second bore, the third bolt having a nut to secure a second pair of thrust bearings to opposing sides of the second bore of the inner cross.  
           [0009]    Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an exploded schematic view in perspective of a universal joint cross according to the invention with a sectional perspective view of the cross outer block.  
         [0011]    [0011]FIG. 2 is a schematic perspective view of a universal joint cross according to the invention with a sectional perspective view of the cross outer block.  
         [0012]    [0012]FIG. 3 is a schematic perspective view of the universal joint cross in FIG. 2 including the complete cross outer block.  
         [0013]    [0013]FIG. 4 is sectional elevation view of a universal joint cross and yoke in accordance with the invention.  
         [0014]    [0014]FIG. 5 is a second sectional elevation view of the universal cross and yoke is rotated 90 degrees from the view of FIG. 4.  
         [0015]    [0015]FIG. 6 is a schematic perspective view of an alternative embodiment of a universal joint cross according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring now to the drawings, there is illustrated in FIG. 1 a universal joint cross, indicated generally at  10 , in accordance with this invention. The universal joint cross  10  includes an inner cross  12  having a first bore  14  and a second bore  16  formed therethrough. The bores  14  and  16  extend through the inner cross  12  at right angles relative to one another and intersect at the rotational center thereof. Thrust bearings  18  rest against the tapered end portions  14   a  of the first bore  14 . Thrust bearings  18  are bearings designed to take axial load into the bearing along its rotating axis. The thrust bearings  18  are comprised of an annular bearing  20  having an inner race  22 , a cage  23 , and a plurality of cylindrically shaped rolling elements  24 . The thrust bearings  18  also include an outer race  26  and a thrust washer  28 . In the preferred embodiment, the diameter of the tapered end portions  14   a  of the first bore  14  is approximately the same as the diameter of the inner face  27  of the inner race  22  of annular bearing  20  so that the tapered end portion  14   a  pushes securely against the inner race  22 . In addition, the thrust washer  28  in the preferred embodiment also has approximately the same diameter as the outer face  25  of the inner race  22 . Although inner face  27  and outer face  25  may have approximately the same diameter, the inner face  27  may have a smaller diameter than the outer face  25  if bearing  20  is a tapered bearing.  
         [0017]    Two thrust bearings  18   a  are also aligned with the second bore  16  of the inner cross  12 . Thrust bearings  18   a  may be of the same shape and design as thrust bearings  18 , but such is not necessary. The thrust bearings  18   a  are comprised of a annular bearing  20   a  having an inner race  22   a,  a cage  23   a,  and a plurality of cylindrically shaped rolling elements  24   a.  The thrust bearings  18   a  also include an outer race  26   a  and a thrust washer  28   a.    
         [0018]    In the preferred embodiment, a cylindrical sleeve  30  extends through the second bore  16 . The cylindrical sleeve  30  is loosely positioned in the second bore  16  to allow for rotation. The sleeve  30  is slightly longer than the length of the second bore  16  to prevent contact between the inner face  27   a  of the inner race  22   a  and the body of the inner cross  12 . The sleeve  30  also has a diameter that is approximately the same as the diameter of the inner face  27   a  of the inner race  22   a  so the sleeve end portions  30   a  fit securely against both inner races  22   a.  Although the preferred embodiment of FIG. 1 shows the use of a sleeve  30  at the second bore  16 , the universal joint cross may be constructed without a sleeve  30  without departing from the scope of the invention.  
         [0019]    A first cross member  31  is divided into two first cross member components  32 . Each first cross member component  32  extends through a thrust bearing  18  and into the first bore  14  at opposing ends of the inner cross  12 . In the preferred embodiment, the first cross member components  32  are threaded adapters, such as the bolts shown in FIG. 1. Each bolt  32  has a threaded portion  32   a  and a head portion  32   b.  The diameter of the threaded portion  32   a  of the first cross member components  32  is slightly less than the inside diameter of the thrust washer  28 , while the head portion  32   b  of the first cross member components  32  is larger than the inside diameter of the thrust washer  28 . Although the head portions  32   b  are shown with a hexagonal head in the figures, it should be recognized that the head portions  32   b  may be of any shape as long as they are larger than the inside diameter of the thrust washers  28 .  
         [0020]    When the first cross member components  32  are threaded into opposing ends of the first bore  14 , the head portion  32   b  secures the thrust washers  28  and inner races  22  of the thrust bearings  18  against the end portions  14   a  of the inner cross  12 . The length of the first cross member components  32  is such that the threaded portion  32   a  extends only partially into the body of the inner cross  12  so the components  32  do not block the second bore  16 , thus allowing a second cross member  33  to extend through the second bore  16  in a manner that allows for a limited amount of rotation between the first cross member  31  and the second cross member  33  during operation of the universal joint.  
         [0021]    The second cross member  33  extends through a thrust bearing  18   a  on either side of the second bore  16 . In the preferred embodiment, the second cross member  33  is comprised of a threaded adapter or bolt  34  having a threaded portion  34   a  and a head portion  34   b.  The threaded portion  34   a  of the bolt  34  has a diameter slightly less than the inside diameter of the thrust washer  28   a  while the head portion  34   b  is larger than the inside diameter of the thrust washer  28   a.  Although the head portion  34   b  is shown as a hexagonal head in the figures, it should be recognized that the head portion  32   b  may be of any shape as long as it is larger than the inside diameter of the thrust washers  28   a.  Since the bores  14  and  16  extend through the inner cross  12  at right angles relative to one another, the first cross member  31  and the second cross member  33  are positioned normal to each other.  
         [0022]    The length of the bolt  34  is such that the threaded portion  34   a  extends completely through the body of the inner cross  12  so a threaded nut  36  may be secured at the opposing side. In passing through the body of the inner cross  12 , the second cross member  33  passes through two thrust bearings  18   a  located on opposing sides of second bore  16 . The second cross member  33  also passes through the cylindrical sleeve  30  which is rotatably mounted within the second bore  16 . When the threaded nut  36  is tightened onto the threaded portion  34   a  of the bolt  34 , the threaded nut  36  and head portion  34   b  push the opposing thrust washers  28   a  against the inner faces  27   a  of the inner races  22   a  of the thrust bearings  18   a.  Thus, the inner races  22   a  are pushed against the end portions  30   a  of the cylindrical sleeve  30 .  
         [0023]    Although the preferred embodiment of FIG. 1 shows the second cross member  33  being comprised of a single threaded adapter  34  and nut  36  tightened against a rotatable cylindrical sleeve  30 , it should be recognized that other similar embodiments may be used without departing from the scope of the invention. For example, the second cross member  33  could instead be constructed using two threaded adapters that thread into opposing ends of sleeve  30 .  
         [0024]    The universal joint cross  10  includes a block  38  having an interior or hollowed portion  39  and two opposed pairs of openings  40  and  40   a.  The opposed pairs of openings  40  and  40   a  are located normal or at right angles relative to one another to correspond with the first cross member  31  and the second cross member  33 , respectively. The openings  40  and  40   a  are sized to respectively receive the outer races  26  and  26   a  of thrust bearings  18  and  18   a.    
         [0025]    The block  38  is preferably constructed of a strong, durable material such as hardened steel. The wall thickness t of the block  38  is preferably at least 10 percent of the maximum dimension T of the block  38 . Although the block  38  is shown with a cubical shape, the block  38  may have many shapes without departing from the scope of the invention, as will be shown below. The block  38  may be constructed in half sections as shown in FIG. 1 to facilitate installation of the inner cross  12 , with the half sections later assembled by conventional means such as welding or bolting.  
         [0026]    As is best shown in FIGS. 2 and 3, the head portions  32   b  of first cross member  31  each extend through thrust bearings  18 , while thrust bearings  18  are positioned within the openings  40 . The thrust bearings can be retained within the openings  40  by the geometry of the structure, by press fitting, or by any other suitable means. Thus, when torque is transferred through the universal joint cross  10  at the first cross member  31 , the torque is transmitted through the thrust bearings  18  to the outer block  38 , thereby preventing undesirable deflections or vibrations in the first cross member  31 . The head portions  32   b  are shown compressed against the thrust washers  28  in FIGS. 2 and 3, which is a position in which the components may be shipped prior to attachment to a conventional yoke. This position will change when the cross  10  is attached to a conventional yoke to form a universal joint, as will be explained below.  
         [0027]    Similar to the first cross member  31 , the second cross member  33  has head portions  34   b  that extend through thrust bearings  18   a.  Each thrust bearing  18   a  is positioned and retained by the geometry of openings  40   a,  preferably by press fitting. Thus, when torque is transferred between the universal joint  10  and the second cross member  33 , the torque is transmitted through the thrust bearings  18   a  to the outer block  38 , thereby preventing undesirable deflections in the second cross member  33 . The head portion  34   b  and nut  36  are shown compressed against the thrust washers  28   a  in FIGS. 2 and 3, which is a position in which the components may be shipped prior to attachment to a conventional yoke. This position will change when the cross  10  is attached to a conventional yoke to form a universal joint, as explained below.  
         [0028]    [0028]FIG. 4 shows the universal joint cross  10  engaged with a yoke  41 . Although the yoke  41  is shown as an end yoke, the yoke may be any conventional type of yoke secured to a driving or driven member (not shown) by any conventional means, such as by welding, adhesives, bolting, or slip joint. The end yoke includes arms  42  with lug openings  44  in the arms  42  to receive either the first cross member  31  or second cross member  33 . In FIG. 4, the second cross member  33  passes through the lug openings  44  of the yoke arms  42 . When the cross  10  is engaged with the yoke arms  42 , an additional washer  29  may be placed between the head portion  34   b  and one of the yoke arms  42 , and another washer  29  may be placed between the nut  36  and a second yoke arm  42 , as shown in FIG. 4. If yoke  41  is rotating as a driven member in FIG. 4, then yoke  41  transfers torque to second cross member  33 , and the load is then applied through the block  38  to the first cross member  31  at thrust bearings  18 . The first cross member  31  then further applies the torque to a driven member (not shown).  
         [0029]    [0029]FIG. 5 shows the universal joint of FIG. 4 from an alternate sectional view to show the portion of the cross  10  that would engage with a driven member (not shown). The head portions  32   b  of the bolts  32  are shown compressed against thrust bearing  28  in FIG. 5, which is a position in which the universal joint cross  10  might be shipped prior to installation. However, when a driven yoke (not shown) is attached to the first cross member  31 , the bolts  32  would be loosened to secure a yoke arm to the first cross member  31  in a manner similar to that shown in FIG. 4. When the driven yoke (not shown) is engaged with the first cross member  31 , additional washers  29  may also be placed between the head portions  32   b  and the arms of the driven yoke.  
         [0030]    As previously mentioned, the block  38  surrounding the inner cross  12  may take on many shapes other than cubical. One such embodiment of a universal joint cross  10   a  of the invention is shown in FIG. 6 where the block  38   a  is shown with an approximately cylindrical shape. Other possible shapes for the block may include a spherical or multi-sided block, but are not limited to such.  
         [0031]    The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.