Abstract:
An articulating joint apparatus includes a first rotational member having an axis, a second rotational member coupled with and positioned generally coaxial to the first rotational member, and a boot cover assembly for sealing at least part of the first rotational member to the second rotational member. The boot cover assembly is selectively coupled to both the first rotational member and the second rotational member. The joint apparatus also includes an insert positioned at least partially between the first rotational member and the second rotational member. The insert will deform in response to axial movement of the second rotational member relative to the first rotational member.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates generally to articulated joints, and more specifically to a system and method for reducing the volume of lubricant for an articulated joint. 
       BACKGROUND 
       [0002]    Constant velocity joints (CVJ joints) and other rotational joints are common components in automotive vehicles. Typically, constant velocity joints are used where a transmission of constant velocity rotating motion is required. The common types of constant velocity joints are plunging tripod, a fixed tripod, a plunging ball joint and a fixed ball joint. These types of joints are currently used in front wheel drive vehicles, rear wheel drive vehicles and on propeller shafts found in rear wheel drive, all wheel drive, and four wheel drive vehicles. The constant velocity joints are generally grease lubricated for life and sealed by a sealing boot when used on driveshafts or half shafts. Therefore, constant velocity joints are sealed in order to retain grease inside the joint and keep contaminates, such as dirt and water out of the joint. To achieve this protection the constant velocity joint is usually enclosed at the opened end of an outer race by a sealing boot made of a rubber, thermoplastic, or silicone type material. The opposite end of the outer race generally is enclosed by a dome or cap, known as a grease cap in the case of a disk type joint. A mono block or integral stem and race design style joint is sealed by the internal geometry of the outer race. This sealing and protection of the constant velocity joint is necessary because contamination of the inner chamber of the joint generally will cause damage to the joint. 
         [0003]    A main function of the constant velocity joint is the transmission of rotational forces and torque. A plunging joint will transmit rotational velocity while permitting relative axial displacement within the joint. Generally, a tripode joint operates as a plunging constant velocity joint while providing some degree of axial articulation. In typical joint assemblies, a variety of bolted joint designs are used to assemble a joint to a propshaft or halfshaft within the automotive vehicle. These propshaft and halfshaft assemblies are typically assembled prior to installation within a driveline of a vehicle. 
         [0004]    When a joint is installed within a vehicle, the lubricant within the joint will tend to exert a force on the boot when the joint is rotating thus causing deformation. Deformation of the boot is undesirable because damage to the boot my result from boot-to-boot contact. Damage to the boot causes loss of lubricant from the joint and contamination of the joint with water and debris. Additionally, lubricant is a very expensive component of a joint. Reducing the volume of lubricant is desirable for cost savings and to minimize the forces exerted on the boot and causing deformation. However, decreasing the volume of lubricant in a joint, with nothing more, may result in a joint with inadequate lubrication of the internal components resulting in a less effective joint. What is needed, therefore, is a system for decreasing the volume of lubricant in a joint while still maintaining adequate lubrication of the internal components. 
       SUMMARY 
       [0005]    An embodiment includes a joint apparatus including a first rotational member having an axis, a second rotational member coupled with and positioned generally coaxial to said first rotational member, and a boot cover assembly for sealing at least part of the first rotational member to the second rotational member. The boot cover assembly is selectively coupled to both the first rotational member and the second rotational member. The joint apparatus also includes an insert positioned at least partially between the first rotational member and the second rotational member. The insert will deform in response to axial movement of the second rotational member relative to the first rotational member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Referring now to the drawings, preferred illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the embodiments set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
           [0007]      FIG. 1  is a top view of a driveline system. 
           [0008]      FIG. 2  is a partial sectional top view of the propshaft illustrated in  FIG. 1 . 
           [0009]      FIG. 3  is a partial sectional view of a portion of the propshaft of  FIG. 2 . 
           [0010]      FIG. 4  is an exploded perspective view of a portion of a propshaft of  FIG. 2 . 
           [0011]      FIG. 5  is a sectional view taken along broken line  5 - 5  of  FIG. 3 , with some section graphics removed for clarity. 
           [0012]      FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 3 . 
           [0013]      FIG. 7  is a partial sectional view of a portion of the propshaft of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates a driveline  20  of a vehicle (not shown). The driveline  20  includes an engine  22  that is connected to a transmission  24  and a power take off unit  26 . A front differential  32  has a right hand front half shaft  34  and a left hand front half shaft  36 , each of which are connected to a wheel  38  and deliver power to those wheels  38 . The power take off unit  26  has a propeller shaft  40  and a front wheel propeller shaft  42  extending therefrom. The front wheel propeller shaft  42  connects the front differential  32  to the power take off unit  26 . The propeller shaft  40  connects the power take off unit  26  to a rear differential  44 , wherein the rear differential  44  includes a rear right hand side shaft  46  and a rear left hand side shaft  48 , each of which ends with a wheel  38  on one end thereof. 
         [0015]    The propeller shaft  40 , as best seen in  FIG. 2 , includes a front prop shaft  52 , a rear prop shaft  54 , an articulated tripode joint  50  and two high speed constant velocity joints  60 . The front prop shaft  52  is defined by an axis A-A, and the rear prop shaft  54  is defined by an axis B-B. The constant velocity joints transmit power to the wheels  38  through the driveshaft  40  even if the wheels or the shaft have changing angles due to steering and suspension jounce and rebound. A constant velocity joint  60  is also located on both ends of the half shafts that connect to the wheel  38  and the rear differential  44 . On both ends of the right hand front half shaft  34  and left hand front half shaft  36  are constant velocity joints  60 . 
         [0016]    The constant velocity joints  60  may be of any of the standard types known, such as plunging tripod, cross groove joint, fixed ball joint, fixed tripod joint, or double offset joints, all of which are commonly known terms in the art for different varieties of constant velocity joints. The constant velocity joints  60  allow for transmission of constant velocities at angles which are found in everyday driving of automotive vehicles in both the half shafts and prop shafts of these vehicles. 
         [0017]    The driveline  20  represents an all wheel drive vehicle, however it should be noted that the embodiment of the constant velocity joints  60  of the current disclosure can also be used in rear wheel drive vehicles, front wheel drive vehicles, all wheel drive vehicles and four wheel drive vehicles. 
         [0018]    As best seen in  FIGS. 3-5 , the joint  50  includes a tulip, first rotational member, or an outer joint portion  70 , connected to the front prop shaft  52 , and a second rotational member, or an inner joint portion,  72 . The second rotational member  72  includes a shaft  74  connected to the rear prop shaft  54 . The second rotational member  72  also includes a tripode star, or spider,  76  splined to the shaft  74 . As best seen in  FIGS. 2 and 3 , the first rotational member  70  is also generally defined by the axis A-A of the front prop shaft  52  and the shaft  74  is also generally defined by the axis B-B of the rear prop shaft  54 . 
         [0019]    The first rotational member  70  is provided with a first inner surface  80  and a second inner surface  82  defining an inner recess  84  having three uniformly circumferentially distributed vaults  86  (see  FIG. 4 ). The vaults  86  form pairs of circumferentially opposed fillet-shaped tracks  88  connected by a vault major surface  90  that extend from an opening end  94  of the first rotational member  70  to a wall  96 . The wall  96  is defined, in part, by the first inner surface  80 . The tracks  88  of adjacent vaults  86  are connected by a tulip minor surface  92 . The spider  76  includes an annular hub portion  100  provided with an aperture  102  for inserting the shaft  74  therein and three uniformly circumferentially distributed trunnion lands  104 . As illustrated, the spider  76  is splined to the shaft  74  for rotation therewith. Extending from the hub portion  100  (at each trunnion land  104 ) are three uniformly circumferentially distributed trunnions  106  having axes T 1 , T 2 , and T 3  having a trunnion crown  108  at a distal end. One trunnion  106  is interposed into each vault  86 . A roller assembly  110  is interposed within each vault  86  with a trunnion  106  interposed therein. Each roller assembly  110  includes bearing needles  116  and rollers  118 . 
         [0020]    Each roller  118  with bearing needles  116  are axially restrained on each trunnion  106  by a securing ring  120 . The roller assemblies  110  are permitted to axially float along axes T 1 , T 2 , T 3  between the trunnion lands  104  and the securing rings  120 . Additionally, a substantially hollow-cylindrical roller carrier (not shown) may be interposed between each trunnion  106  and the bearing needles  116 . Generally, the vault major surface  90  is defined by a first vault diameter DV, and the tulip minor surface  92  is defined by a second vault diameter dv ( FIG. 5 ). Each trunnion  106  includes a cylindrical outer surface  124  and a trunnion end  126 . When the spider  76  is positioned concentric to the first rotational member  70 , a clearance C is generally provided between each trunnion end  126  and vault major surface  90  ( FIGS. 3 and 5 ). 
         [0021]    As best illustrated in  FIG. 5 , the joint  50  may be trisected about the axes A-A and B-B into three generally equal portions. When the joint  50  is in operation with the first rotational member  70  and shaft  74  generally axially aligned, the rotational forces within the joint  50  urge the axes A-A and B-B to be co-axial and the trunnions float within the roller assemblies  110  to provide a generally equal clearance C between each trunnion crown  108  and vault major surface  90 . 
         [0022]    As best seen in  FIG. 3 , the joint  50  also includes a boot assembly  130 . The boot assembly  130  includes a boot can  132  and a flexible boot  134 . The flexible boot  134  includes an outer bead end  140 , an inner shaft end  142 , a flexible portion  144  extending therebetween, an outer boot surface  146 , and an inner boot surface  148 . The boot can  132  includes a crimped end  150  that is folded over the bead end  140 , a tulip end  152  connected to the first rotational member  70 , a generally cylindrical can body  154  extending therebetween, an outer can surface  156 , and an inner can surface  158 . 
         [0023]    The joint  50  also includes an insert  170  ( FIGS. 3 ,  4 , and  6 - 8 ). The insert  170  includes a body defined by a contoured outer surface  174 , a first insert surface  176 , and a second insert surface  178 . As best seen in  FIG. 6 , the insert also includes a central insert portion  180  having vault insert portions  186  extending therefrom. In the embodiment illustrated, the contoured outer surface  174  closely contours the second inner surface  82 . In other embodiments, the contoured outer surface  174  may not closely contour circumferential surfaces of the joint. Although a plunging tripod joint is illustrated, an insert, such as the insert  170  may be used in any other type of joints, including cross groove joints, fixed ball joints, fixed tripod joints, double offset joints and the like. 
         [0024]    The joint  50  further includes a predetermined amount of lubricant, such as a grease, within the recess  84 . This lubricant reduces wear between frictional surfaces and increases joint life. When the joint  50  is rotating, centripetal forces exerted by at least the second inner surface  82  on the lubricant will force the lubricant into the vaults  86  and form a generally cylindrical inner lubricant void  192 . In one example, a typical inner lubricant void  192  is illustrated in  FIGS. 3 ,  5 , and  6  generally defining a diameter DG. The diameter DG and the inner lubricant void  192  are both interrupted by the shaft  74  and spider  76 . That is, when the joint  50  is operating at sufficient speed to create an inner lubricant void  192 , the lubricant will fill the recess  84  with the exception of the physical space occupied by the shaft  74  and spider  76 . 
         [0025]    As the speed of the joint  50  increases, such as an increase to a speed of several thousand rotations per minute (rpm), the lubricant will be forced away from the axis A-A (centrifuge) due to the rotation of the joint and the lubricant will also be urged such that the lubricant exerts a force on the boot  134 . This force exerted on the boot  134  by the lubricant will deform the boot  134  away from the spider  76 . Undesirable amounts of deformation of the boot  134  away from the spider  76  may result from the geometry of the joint  50  and the volume of lubricant. Accordingly, the force exerted by the lubricant on the boot  134  is related to the amount of lubricant within the joint  50 . Stated differently, reducing the volume of lubricant within the joint  50  will result in less force, and therefore, less deformation of the boot  134  at a given rotational speed of the joint  50 . 
         [0026]    As best seen in comparing  FIGS. 3 and 7 , the first rotational member  70  may be axially displaced relative to the shaft  74 . This relative axial displacement is limited by contact between the shaft  74  and spider  76  and the insert  170  at a full shaft insertion configuration ( FIG. 7 ) and extension of the boot  134  at a shaft extended configuration (not shown). The insert  170  is compressible such that the insert  170  may be deformed in the direction generally along the axis A-A resulting in the insert  170  occupying less volume within the recess  84 . In the embodiment illustrated, the insert  170  is constructed of a closed cell foam, although other materials may be used in other embodiments. In a joint  50  that does not include an insert, such as the insert  170 , the relative axial displacement would be limited by contact between the shaft  74 /spider  76  and the wall  96  at a full shaft insertion configuration (not shown). Therefore, the insert  170  limits contact between the first rotational member  70  and the second rotational member  72 , although the configuration of the driveline  20  may also prevent contact. 
         [0027]    As also seen in comparing  FIGS. 3 and 7 , the clearance C between each trunnion end  126  and vault major surface  90  permits the shaft  74  to plunge (relative movement along the axis A-A) relative to the first rotational member  70  as in  FIG. 8  and permits at least a portion of the lubricant to pass through the area A 1  ( FIG. 5 ) between the trunnions  106  and the second inner surface  82  (at least partially defined by the clearance C). 
         [0028]    When the joint  50  is operated, a desirable volume of lubricant is inserted into the joint to lubricate the frictional surfaces and aid in heat transfer. Generally, this volume of lubricant provides a desirable volume of lubricant at the portions of the joint  50  that are within the joint  50  and positioned farther from the axis A-A. That is, the volume of lubricant in a joint may be determined based upon a desirable volume that will ensure that the frictional surfaces are covered during joint  50  operation. In the forgoing example, the desired volume of lubricant is the volume of the joint  50  outside of the lubricant void  192 . In other examples, the joint, such as a joint  50  may have any desirable volume of lubricant, including a joint completely full of lubricant with no air or lubricant void. 
         [0029]    In one embodiment of operation of a joint, such as the joint  50 , the joint is assembled as described. When the joint  50  rotates sufficiently to form a generally cylindrical lubricant void  192 , the frictional surfaces of the joint  50  are lubricated. Although the volume of lubricant exerts a force on the boot  134 , the volume of lubricant adequate to form a lubricant void of equal diameter to the lubricant void  192  in an otherwise identical joint that does not include an insert, such as the insert  170 , is greater, resulting in a greater force on the boot of the joint without an insert  170 . 
         [0030]    When the joint  50  experiences an axial deflection where the second rotational member  72  is forced toward the wall  96 , the insert is compressed. Therefore the presence of the insert  170  will not limit the joint  50  from performing the ‘plunge’ function of a joint  50  that does not include an insert. Therefore the insert  170  enables the joint  50  to provide a lower volume of lubricant while having a desired amount of lubricant void  192  and permitting a desired amount of joint plunge. 
         [0031]    In the embodiment illustrated, the insert  170  will not absorb appreciable amounts of grease, although some absorption of grease may occur, depending upon material selection. Further the material of the insert  170  is desirably durable to withstand heat and compressive pressures due to operation of the joint  50 . 
         [0032]    In the embodiment illustrated, the insert  170  will axially deform when the second rotational member  72  moves toward the wall  96 . Additionally, the insert  170  may axially deform, and may radially deform such that the contoured outer surface  174  of the insert will separate from the tulip major surface  90 , due to the generally axial force exerted by the lubricant as the lubricant is centrifuged within a rotating joint  50 . This deformation of the insert  170  is preferably minimized by material selection. That is, since the force exerted by the lubricant during operation of the joint  50  is lower than the force exerted by the second rotational member  72  during operation, the material of the insert  170  will compress, or deform, from the thickness T 1  to the thickness T 2  without appreciably affecting operation of the joint  50  while resisting undesired deflection due to any force exerted by the lubricant. 
         [0033]    The central insert portion  180  that lies within the diameter DG of the lubricant void  192  does not necessarily displace lubricant during operation of the joint  50 , but will direct the lubricant toward the radial surfaces  90 ,  92  during centrifuging of the lubricant. Further, the lubricant may separate into constituent portions due to temperature and shear forces within the joint  50  during operation while performing as described herein. 
         [0034]    The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. 
         [0035]    The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims.