Abstract:
A lubrication flow control mechanism for a power transmission includes a bearing member and a spring biasing the bearing member in a direction. The bearing member and the spring cooperate to sufficiently restrict flow past the bearing to cause increased fluid flow to a lubrication-requiring member located downstream of the bearing. A method of limiting lubrication flow in a transmission is also provided.

Description:
CORSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/589,279, filed Jul. 20, 2004, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to lubrication of a power transmission.  
       BACKGROUND OF THE INVENTION  
       [0003]     Lubrication fluid within a power transmission follows a path of least resistance. This makes it difficult to sufficiently lubricate transmission components that require fluid to flow along a more restrictive path when a less restricted path is also available. Due to assembly gaps formed between transmission components, unintended flow paths are created that must be addressed in order to ensure adequate flow to components located along more restricted paths.  
       SUMMARY OF THE INVENTION  
       [0004]     A lubrication flow control mechanism for a power transmission is provided that enables sufficient lubricating fluid flow to lubrication requiring members located at restricted flow paths. Accordingly, a lubrication flow control mechanism includes a bearing and a spring biasing the bearing in a direction. The bearing member and the spring cooperate to sufficiently restrict a first flow passage to cause increased fluid flow to a second flow passage. The bearing and the spring sufficiently restrict flow past the bearing to cause increased fluid flow to a lubrication-requiring member located downstream of the bearing.  
         [0005]     In one aspect of the invention, the bearing and spring cooperate to restrict flow in a first flow passage defined between a differential mechanism and a transmission gear, such as a sun gear. The bearing and the spring are disposed between the differential mechanism and the gear in the first flow passage. The bearing may include an inner bearing race connected to the transmission gear for rotation therewith as well as an outer bearing race connected to the differential mechanism for rotation therewith. Preferably, the outer bearing race has an axial flange formed with circumferentially-spaced slots. The spring includes circumferentially-spaced tabs fittable within the slots so that the spring is secured to the outer bearing race for rotation therewith. Preferably, the tabs extend from the small diameter end of the spring. The spring is compressible and extendable so that a large diameter end of the spring contacts the differential mechanism when the tabs are fitted in the slots.  
         [0006]     In another aspect of the invention, the differential mechanism includes a differential carrier and a side gear rotatable with respect to the carrier. The differential carrier partially defines the first flow passage and the side gear partially defines the second flow passage. Specifically, the second flow passage is defined between intermeshing teeth of the side gear in the rotatable shaft.  
         [0007]     A method of limiting lubrication flow in a transmission includes providing a thrust bearing and connecting a spring with the thrust bearing. In another step, the thrust bearing and spring are positioned between adjacent transmission components. In another step, fluid is directed toward the thrust bearing and spring. Radial flow of the directed fluid between the adjacent transmission components is blocked and fluid flow is increased downstream of the thrust bearing and spring via the positioning step. Thus, the method may include lubricating a downstream transmission component (e.g., such as the side gear) with the increased downstream fluid flow.  
         [0008]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic side view illustration of a vehicle including a power transmission;  
         [0010]      FIG. 2  is a schematic cross-sectional illustration in fragmentary view of the transmission of  FIG. 1 , including a needle thrust bearing;  
         [0011]      FIG. 3  is a schematic cross-sectional illustration in fragmentary view of the transmission of  FIGS. 1 and 2 , showing a spring abutting the bearing of  FIG. 2 ; and  
         [0012]      FIG. 4  is a schematic perspective illustration in fragmentary cross-sectional view of the spring of  FIG. 3  connected with the bearing of  FIGS. 2 and 3 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     Referring to the drawings, wherein like reference numbers refer to like components, a vehicle  10  includes an engine  12  operatively connected to a transmission  14  for transmitting power to wheels  16  to propel the vehicle, as is know in the art.  
         [0014]     Referring to  FIGS. 2 and 3 , the power transmission  14  includes a planetary gear set  17  that has an output sun gear  18  disposed adjacent to a transmission output shaft  20  and rotatable with the shaft  20 , forming an intermediate flow passage  22  therebetween. Fluid is supplied to the intermediate flow passage  22  through a feeder passage  24  formed at least partially by a transmission case  26 . A fluid source, such as a pump (not shown), provides fluid gathered in an oil sump (not shown) to the feeder passage  24 , as is well understood by those skilled in the art. (Fluid flow is represented by arrows labeled F shown in the various flow passages described herein.)  
         [0015]     The fluid passing between the sun gear  18  and the output shaft  20  via the intermediate flow passage  22  is eventually supplied to a side gear  28  of a differential mechanism  30 . The lubrication fluid passing through the intermediate flow passage  22  also encounters a needle thrust bearing  32 , which is positioned between the output sun gear  18  and a differential carrier  34 . In order to restrict a first flow passage  36  past the bearing  32  in an axial space between the sun gear  18  and the differential carrier  34 , a wave or Belleville spring  38  is positioned between the thrust bearing  32  and the differential carrier  34 . This enforces axial tightness of the space occupied by the thrust bearing  32 , thereby limiting direct radial flow past the thrust bearing  32  (i.e., through the space between the sun gear  18  and the differential carrier  34 ). Centrifugal force will encourage such radially-outward flow.  
         [0016]     The bearing  32  includes a roller element  39  disposed between a generally annular inner bearing race  40  and a generally annular outer bearing race  42 . The inner bearing race  40  is secured to the sun gear  18  via welding or any other known connecting means. The outer bearing race  42  is secured to the differential carrier  34  by any known connecting means. As best shown in  FIG. 4 , the outer bearing race  42  includes an axial flange  43  formed with a plurality of circumferentially spaced slots  44 . The spring  38  includes a plurality of circumferentially spaced tabs  46  extending from an inner diameter  48 . The tabs  46  fit within corresponding slots  44  to secure the spring  38  to the outer bearing race  42  for rotation therewith. An outer diameter  50  of the spring  38  rests against the differential carrier  34  (shown in  FIG. 3 ). The spring  38  flexes axially between its inner and outer diameters so that the bearing  32  and spring  38  together fill the axial space between the sun gear  18  and the differential carrier  34  and prevent fluid flow radially past the bearing  32  through the first flow passage  36  defined between the sun gear  18  and differential carrier  34 .  
         [0017]     In normal thrust bearing operation, the bearing  32  is not always fully loaded and therefore can provide a large flow area for the lubrication fluid. The spring  38  prevents this large flow area from being presented to the lubrication flow by limiting the discharge of fluid radially through the planetary gear set  17  via the first flow passage  36 . The bearing  32  and spring  38  together form a lubrication flow limiting assembly  32 ,  38  which acts as a dam to force fluid toward, for example, a second flow passage  52  formed between respective intermeshing teeth  54 ,  56  of the intermeshing side gear  28  and output shaft  20 . Thus, the lubrication flow limiting assembly  32 ,  38 , by virtue of the biasing function of the spring  38 , causes more efficient fluid flow to high resistance flow areas, such as the second flow passage  52 , thus providing better lubrication to components at such high resistance flow areas, such as the side gear  28 .  
         [0018]     While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.