Patent Publication Number: US-2005143178-A1

Title: Method and apparatus for detecting worn universal joint components

Description:
BACKGROUND OF THE INVENTION  
      This invention generally relates to a method and apparatus for servicing a universal joint assembly installed in a vehicle driveline to detect worn components.  
      Vehicle drivelines include at least one driveshaft that is used to transmit power from a vehicle engine and transmission to a single drive axle or tandem drive axle. Typically, heavy-duty vehicles, such as large trucks, include more than one driveshaft due to the long wheelbase and/or use of a tandem drive axle. At each end of a driveshaft, universal joints (U-joints) are used to connect the driveshaft to the next driveline component. For example, U-joints can be used to connect one driveshaft to another driveshaft or can be used to connect a driveshaft to a drive axle component.  
      U-joints allow two driveline components to be positioned at different angles relative to each other to accommodate relative movement and angular misalignment. Further, as the drive axles cooperate with a vehicle suspension to dampen shocks from rough road conditions, the U-joints provide flexibility to allow the adjoining driveline components to move relative to one another.  
      Typically, U-joints include two yokes that each have two bore locations at diametrically opposed positions. The yokes are each mounted to two trunnions on a center cross member. The combination allows the two yokes to move angularly relative to each other with respect to the center of the cross member.  
      In order for the U-joint to operate properly overlong periods of time, it is important to have good lubrication. The center cross member typically includes an external grease fitting that is in fluid communication with each of the trunnion members via internal grease grooves or channels. Bearing packs are mounted on each of the trunnions and receive lubrication through the grease grooves. The bearing packs include a seal assembly that seals the grease within the center cross member.  
      It is often difficult to detect when U-joint components have worn sufficiently, such that repair or replacement operations are required. Currently, to detect worn seals, the U-joint must be completely disassembled and inspected. This process is time consuming and labor intensive, which results in increased service costs and vehicle downtime, both of which are undesirable.  
      Thus, it would be valuable to have a simple and efficient inspection procedure to detect worn U-joint components without having to disassemble the U-joint. The method and apparatus to detect worn components should be easily incorporated into existing U-joints without significant increases in cost.  
     SUMMARY OF THE INVENTION  
      A serviceable, permanently lubed, universal joint assembly utilizes a fluid pressure member to detect the operating condition of a universal joint assembly during a service operation. The universal joint assembly includes a cross member having a plurality of trunnions that cooperate with yoke members supported by adjacent driveline components. Each trunnion supports a seal and bearing assembly which are mounted within a cap installed over a distal end portion of the trunnion.  
      The operating condition of the internal components, such as bearings and seals, can be easily detected without having to disassemble the universal joint assembly. A lubricating fluid is injected into the cross member via an external lubrication fitting. A properly operating universal joint assembly is detected when lubricating fluid exits the fluid pressure member, and an improperly operating universal joint assembly is detected when the lubricating fluid exits at least one of the seal assemblies instead of the fluid pressure member.  
      In the preferred embodiment, the cross member includes a central body portion with a first pair of trunnions coupled to a first yoke member and a second pair of trunnions coupled to a second yoke member. The cross member includes an internal lubrication channel that is in fluid communication with each of the trunnions. An external lubrication fitting is supported by the cross member and is in fluid communication with the internal lubrication channel. The fluid pressure member is supported by the cross member and also is in fluid communication with the internal lubrication channel. An internal fluid pressure is generated within the cross member in response to a lubricating fluid being injected into the internal lubrication channel via the external lubrication fitting. A first operating condition is indicated when the internal fluid pressure is below a predetermined pressure value and a second operating condition, different than the first operating condition, is indicated when the internal fluid pressure exceeds the predetermined pressure value.  
      As discussed above, each of the trunnions includes a seal assembly that seals the lubricating fluid within the internal lubrication channel. Each seal assembly has a predetermined initial sealing force that is greater than the predetermined pressure value. The first operating condition is defined as the improperly operating universal joint and occurs when at least one of the seal assemblies has an operating sealing force that is less than the predetermined initial sealing force and less than the predetermined pressure value, such that the lubricating fluid exits the cross member through the defective seal assembly instead of through the fluid pressure member. The second operating condition is defined as the properly operating universal joint and occurs when the internal fluid pressure achieves the predetermined pressure value, which activates the fluid pressure member and allows lubricating fluid to exit the cross member via the fluid pressure member.  
      In one disclosed embodiment, the fluid pressure member comprises a pressure relief valve mounted directly to the cross member. The pressure relief valve is resiliently biased such that lubricating fluid cannot exit the cross member until the predetermined pressure value is achieved. The pressure relief valve is preferably threaded to the central body portion and is centrally positioned on an end face of the central body portion or on an edge between adjacent trunnions.  
      Thus, the subject invention provides a method and apparatus for easily detecting worn components in a universal joint assembly without requiring the universal joint assembly to be disassembled. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an overhead schematic view of driveline for a heavy-duty vehicle.  
       FIG. 2  is a magnified exploded view of a portion of the driveline from  FIG. 1 .  
       FIG. 3  is a perspective view of a universal joint cross member incorporating the subject invention.  
       FIG. 4  is a perspective internal view of one of the needle cups of  FIG. 3 .  
       FIG. 5  is top cross-sectional view of the cross member of  FIG. 3 .  
       FIG. 6  is a side cross-sectional view of another embodiment of a cross member incorporating the subject invention.  
       FIG. 7  is side view shown in partial cross-section of a fluid pressure member in a first position.  
       FIG. 8  is side view shown in partial cross-section of a fluid pressure member in a second position. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT  
      A heavy-duty vehicle  10  includes a powertrain assembly, shown generally at  12 , that transfers driving power from an engine  14  to a plurality of wheels  16 . The engine  14  is operably coupled to a transmission  18  as is known in the art. A driveline assembly  20 , including at least one driveshaft  22 , is used to transfer driving power from the transmission  18  to a drive axle assembly  24  that supports the wheels  16 . The drive axle assembly  24  can be a single drive axle (not shown) or can be a tandem drive axle as shown in  FIG. 1 . The tandem drive axle includes a forward-rear axle  24   a  and a rear-rear axle  24   b  that are interconnected to each other.  
      Preferably, due to the long wheelbase required for heavy-duty vehicles  10  and/or due to the use of a tandem drive axle, a plurality of driveshafts  22  are used to connect the transmission  18  to the drive axle assembly  24 . It should be understood however, that while multiple driveshafts  22  are preferred, a single driveshaft  22  could be used to connect the transmission  18  to a single drive axle for lighter duty applications.  
       FIG. 2  shows a typical driveshaft arrangement that includes a first driveshaft  22   a  connected to the transmission  18  at one end and connected to a second driveshaft  22   b  at an opposite end. The second driveshaft  22   b  is connected to the drive axle assembly  24  at an end opposite from connection to the first driveshaft  22   a . A third driveshaft  22   c  is used to interconnect the forward-rear axle  24   a  to the rear-rear axle  24   b . A yoke member  26  is supported on each end of the driveshafts  22   a ,  22   b ,  22   c . A cross member  28  is used to interconnect adjoining yoke members  26 . One cross member  28 , coupled to two ( 2 ) yoke members  26 , defines a universal joint assembly (U-joint)  30 .  
      U-joints allow two adjoining driveline components to be positioned at different angles relative to each other to accommodate relative movement and angular misalignment. Misalignment and relative movement can be caused by adjoining driveline components not being mounted within a common plane, or can be caused by a driveline component, such as a drive axle assembly  24 , moving relative to adjoining driveline component, such as a driveshaft  22 , in response to interaction with a vehicle suspension.  
      The cross member  28  is shown in greater detail in  FIG. 3 . The cross member  28  includes a central body portion  32  with a plurality of trunnions  34  extending out radially from the central body portion  32 . Each yoke member  26  is attached to a pair of trunnions  34 , as is known in the art.  
      Bearing packs or needle cups  36  are installed over each trunnion  34 . The needle cups  36  include a mounting interface  38  that attaches to the yoke member  26 . The cross member  28  shown in  FIG. 3  has one exposed trunnion  34  and three trunnions with installed needle cups  36 . The central body portion  32  also includes at least one external lubrication fitting  40  through which a lubricating fluid, such as grease, is injected into the cross member  28  to provide lubrication so that the U-joint  30  can operate properly.  
      Each needle cup  36  includes an internal cavity  42  that is slidably received over one trunnion  34 . A plurality of needle bearings  44  is mounted within the cavity  42 . A thrust washer  46  is preferably mounted within the bottom of the cavity  42  and a seal assembly  48  surrounds a lip of the cavity  42  to seal the lubricating fluid within the cross member  28 .  
      The cross member  28  includes an internal lubrication channel  50 , shown in  FIG. 5 , which is in fluid communication with the external lubrication fitting  40 . The internal lubrication channel  50  includes a central portion  50   a , trunnion portions  50   b  that extend into each trunnion  34 , and a fitting portion  50   c  that communicates with the lubrication fitting  40 . This allows lubricating fluid, which is injected through the lubrication fitting  40 , to be communicated through internal lubrication channel  50  to each trunnion  34 , so that the needle bearings  44  can be sufficiently lubricated.  
      A fluid pressure member  52  is supported by the central body portion  32  and is positioned to be in fluid communication with the internal lubrication channel  50 . The fluid pressure member  52  is utilized during service operations to detect U-joints  30  that have worn internal components, such as bearings  44  and seal assemblies  48 , without having to disassemble the U-joint  30 .  
      Each of the seal assemblies  48  has a predetermined initial sealing force when the U-joint  30  is first assembled. Over time, as components wear and as the vehicle  10  experiences heavy operating loads and adverse road conditions, the initial sealing force is reduced. During service, lubricating fluid is injected with a grease gun or other similar mechanism, into the cross member  28  via the lubrication fitting  40 . This generates an internal fluid pressure within the cross member  28 . If the seal assemblies are still in good working condition, the internal lubrication channel  50  will fill with fluid until fluid is forced to exit via the fluid pressure member  52 . Thus, the fluid pressure member  52  is responsive to or activated when a predetermined pressure value is achieved within the cross member  28 . This predetermined pressure value is less than the initial sealing force for the seal assemblies  48 .  
      If the seal assemblies  48  are worn and need to be replaced, as the internal fluid pressure increases, fluid will exit the cross member  28  via the defective seal assembly  48 , instead of through the fluid pressure member  52 . In other words, fluid will exit the cross member  28  from a defective seal assembly  48  because the worn seal has a reduced sealing force is less than the predetermined pressure value that activates the fluid pressure member  52 . Thus, when fluid exits the cross member from the fluid pressure member  52 , the U-joint  30  internal components are still in good operating condition, and when the fluid exits from at least one of the seal assemblies  48 , a worn internal component is detected. Thus, a simple external visual inspection can be used to detect internal worn components.  
      In one embodiment, the fluid pressure member  52  is located at an edge  54  of the central body portion  32  of the cross member  28 , as shown in  FIG. 5 . The fluid pressure member  52  in this embodiment, is positioned between adjacent trunnions  34  and extends out radially from the central body portion  32 . The internal lubrication channel  50  is formed with a channel portion  50   d  that extends to the fluid pressure member  52 .  
      In another embodiment, the fluid pressure member  52  is located centrally on the central body portion  32 , as shown in  FIGS. 3 and 6 . The internal lubrication channel  50  includes a similar channel portion  50   d  that communicates with the fluid pressure member. It should be understood that the fluid pressure member  52  could be mounted in other positions or locations on the central body portion  32 . Similarly, the external lubrication fitting  40  could also be mounted at other locations on the central body portion.  
      Preferably, the fluid pressure member  52  is a pressure relief  60  valve that is movable between a sealed or closed position, shown in  FIG. 7 , and an unsealed or open position, shown in  FIG. 8 . The pressure relief valve  60  includes a longitudinal valve body  62  mounted within a bore  80  that extends from an internal end  64  to an external end  66 . The internal end  64  of the bore  80  is in fluid communication with the internal lubrication channel  50  and the external end of the bore  80  is selectively opened to the external atmosphere when the predetermined pressure value is achieved within the cross member  28 .  
      The pressure relief valve  60  preferably includes a threaded external surface  68  that is threaded into a threaded bore  70  formed within the cross member  28 . A resilient member  72 , such as a coil spring or other similar mechanism, cooperates with a movable cap  74  formed on the valve body  62 . The movable cap  74  is resiliently biased to seal the external end  66  of the bore  80  under normal operating conditions. During a service operation, when lubricating fluid is injected into the cross member  28  and the internal fluid pressure is greater than the predetermined pressure value, the resilient bias force is overcome and the movable cap  74  opens. This allows fluid communication to the external surface of the cross member  28  via the external end  66  of the bore  80 . Once the internal pressure is reduced, the resilient member  72  returns the movable cap to the initial position.  
      The subject invention provides a method and apparatus for easily detecting worn components in a universal joint assembly that does not require disassembly. An additional benefit is that a simple external visual inspection can be used to detect internal worn components in the U-joint. Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.