Abstract:
A thrust bearing assembly includes an upper thrust bearing and a lower thrust bearing for use in an engine assembly of a vehicle and which, are preferably, identically configured. The upper and lower thrust bearings each include an arcuate bearing shell with a concave inner surface and a convex outer surface and each may be formed with a pair of axially spaced flanges extending radially outwardly of the bearing shells. The flanges may be formed as one piece with the bearing shell and the thickness of one of the flanges is greater than that of the other of the flanges. The thicker flanges are load bearing and preferably contoured, whereas the thinner flanges are not. The bearings are installed with the thick flange of each bearing matched radially opposite the thin flange of the companion bearing to minimize fatigue and failure normally attributed to repeated seating and unseating of the bearing assemblies having flanges of equal thickness caused by changing bending loads imparted by a shaft.

Description:
[0001]    This divisional application claims priority to U.S. patent application Ser. No. 11/141,895, filed Jun. 1, 2005, and is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The subject invention relates to a thrust bearing assembly as part of an engine assembly for use in a vehicle and a method of aligning a thrust bearing in the engine assembly. 
         [0004]    2. Description of the Related Art 
         [0005]    Crankshafts are journaled in engine blocks by a series of axially spaced engine bearings. Each engine bearing includes an upper bearing half seated in an arcuate recess of the block and an accompanying lower bearing half clamped tightly against the upper bearing half by a supportive bearing cap bolted to the engine block. At least one of the engine bearings in the set is designed to absorb axial thrust forces imported by the crankshaft during operation. The so-called thrust bearing differs from the other engine bearing in that it has two axially spaced thrust flanges that project radially outwardly. The thrust bearing presents opposite axially outwardly directed thrust faces which are seated on their backsides against support surfaces of the block and engage associated lobes of the crank shaft, when necessary, to provide the thrust support. These thrust flanges typically have a uniform thickness and often are formed with oil grooves and contours to impart a hydrodynamic oil film action to the bearing. 
         [0006]    During operation of the engine, loads on the crank shaft tend to force it in axially opposite directions, accounting for the aforementioned thrust loads imparted to the thrust flanges of the thrust bearing. As the thrust loads are applied in one axial direction, it will be appreciated that the forward-most set of upper and lower thrust flanges will be confronted by the crankshaft lobe and will be seated tightly against the associated support surface of the block. It will be further appreciated that when a thrust force is applied by the crankshaft in the axially opposite direction that the opposite set of thrust flanges will be tightly seated against their associated support surfaces of the block. However, this reverse force also has the effect of unseating the forward-most set of thrust flanges. While the unseated thrust flanges will be re-seated the next time the axial thrust forces imported by the crankshaft change, this constant seating and unseating has the detrimental effect of repeatedly bending and thus stressing the thrust bearing of the base of the thrust flanges, which can lead to premature failure of the thrust bearing. Additionally, the repeated seating and unseating can cause the thrust bearing to become misaligned which can also lead to unwanted stress and failure of the thrust bearings. 
         [0007]    It is an object of the present invention to minimize or eliminate undesirable seating and unseating of thrust bearings and thus prolongs the operating life of the thrust bearings. 
       BRIEF SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0008]    The subject invention provides a thrust bearing having an arcuate bearing shell with a concave inner surface and a convex outer surface. The inner and outer surfaces extend arcuately between opposite ends and extend axially between opposite edges. A pair of flanges are formed as one piece with the bearing shell and extend radially outwardly of the bearing shell from the opposite edges thereof. The thickness of one of the flanges is greater than that of the other of the flanges. Such a thrust bearing is used in combination with another such thrust bearing, and orientated such that the thin flange of one bearing is arranged radially opposite the thick flange of the companion bearing in order to control thrust loads and seating and unseating forces on the thrust bearings. 
         [0009]    When installed in an engine to journal a crankshaft with thick and thin flanges oppositely arranged, thrust forces exerted by the crankshaft in one axial direction confront the thick flange of one of the bearings causing it to seat firmly in the block. Likewise, thrust forces exerted by the crankshaft in the opposite direction confront the thick flange of the other bearing causing it also to seat firmly in the block. Once seated, it is highly desirable to keep the bearings seated and shield them against any forces, which would cause them to unseat. The present invention provides such protection. 
         [0010]    This invention has the advantage of recessing the outer axial faces of the thin flanges axially inwardly of the faces of the thick flanges and by doing so, the crank shaft confronts only the thick flanges is prevented from contacting the thin flanges. As such, this construction and arrangement of the bearings isolates the bearings from any axial “unseating” forces that may otherwise be imparted by the crank shaft to the thin flanges and cause the associated bearings to shift away from this initial fully seated condition. Preventing the condition of repeated seating and unseating further isolates the bearings from bending forces that, over time, could lead to weakening or failure of the bearings. 
         [0011]    The invention has the further advantage of enabling companion bearings to be identically constructed for manufacturing simplicity and cost savings. 
     
    
     
       THE DRAWINGS 
         [0012]    These and other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description and accompanying drawings wherein: 
           [0013]      FIG. 1  is a perspective view of a thrust bearing assembly having an upper thrust bearing and a lower thrust bearing; 
           [0014]      FIG. 2  is a cross-sectional view of either one of the upper thrust bearing and the lower thrust bearing; 
           [0015]      FIG. 3  is a cross-sectional view of the thrust bearing assembly shown mounted into an engine assembly; and 
           [0016]      FIG. 4  is a cross-sectional view of one of the outer faces of the thrust bearing having contours. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    A thrust bearing assembly is shown generally at  10  in  FIG. 1 . The thrust bearing assembly  10  includes an upper thrust bearing  12  and a lower thrust bearing  14 . A cross-sectional view of the lower thrust bearing  14  is illustrated in  FIG. 2 . It is to be appreciated that the upper and lower thrust bearings  12 ,  14  are substantially identical, as will be described below. 
         [0018]    Both of the upper and lower thrust bearings  12 ,  14  include an arcuate bearing shell  16  with a concave inner surface  18  and a convex outer surface  20 . The bearing shell  16  extends between first and second ends  22 ,  24 , as shown in  FIG. 1 , and extends axially between opposite edges  26 ,  28 . 
         [0019]    A pair of flanges, a thick flange  30  and a thin flange  32 , extend radially outwardly of the bearing shell  16  from the opposite edges  26 ,  28  thereof. The flanges  30 ,  32  are formed as one part, or piece, with the bearing shell  16  from a same material. The material is formed and cut into desired lengths. Then the material is bent to form the flanges  30 ,  32  and may then be bent in arcs. Alternatively, the flanges  30 ,  32  may be made separately from the bearing shell  16  and joined mechanically thereto (3-piece construction) as is customary in the art and contemplated by the invention. Each of the upper and the lower thrust bearings  12 ,  14  has the thick flange  30  and the thin flange  32  extending radially from the outer surface  20 . Each of the flanges has an associated axial thickness  34 ,  35 . The thickness  34  of one of the flanges  30  is greater than the thickness  35  that of the other flanges  32 . 
         [0020]    When the bearings  12 ,  14  are arranged in the thrust bearing assembly  10 , the first and the second ends  22 ,  24  of the upper and the lower thrust bearing  12 ,  14  are positioned substantially in mating contact, with the first end  22  of the upper thrust bearing  12  disposed in mating contact with the first end  22  of the lower thrust bearing  14 , and the second end  24  of the upper thrust bearing  12  disposed in mating contact with the second end  24  of the lower thrust bearing  14 . When so are arranged, the thick flange  30  of the upper thrust bearing  12  is aligned or matched radially opposite the thin flange  32  of the lower thrust bearing  14  as illustrated in  FIGS. 1 and 3 . 
         [0021]    Each of the thick flanges  30  and the thin flanges  32  has an inner face  36  and an outer face  38 . The outer face  38  may be contoured as is known in the art and as shown in  FIG. 4 . Preferably, the outer face  38  of the thick flange  30  is contoured while the outer face  38  of the thin flange  32  is free of such contours. In addition to being contoured, the outer face  38  preferably is formed with a series of oil grooves  40 . The oil grooves  40  channel a lubricant to and from the contoured outer face  38  to develop a protective hydrodynamic oil film across the contoured face  38  during operation to reduce friction and wear. The outer faces  38  of the thin flange  32  may also include similar oil grooves to facilitate lubrication in the event contact does occur. 
         [0022]    Aligning the ends  22 ,  24  as set forth above results in the outer faces  38  of the upper and the lower thrust bearings  12 ,  14  being offset from one another by the thickness  34  of the thick flange  30 . The outer face  38  of the thick flange  30  of the upper thrust bearing  12  is in a different plane that the outer face  38  of the thin flange  32  of the lower thrust bearing  14 , as best shown in  FIG. 3 . Because the outer faces  38  are in different planes, when a force is exerted in one direction on the upper thrust bearing  12 , the lower thrust bearing  14  does not become unseated. This result is obtained because the thin flange  32  of the upper thrust bearing  12  is not in contact with adjacent support surfaces to transmit the force. Therefore, once one of the thrust bearings  12 ,  14  is seated, it will not become unseated due to a force in the opposite direction. Also, the thrust bearings  12 ,  14  will have less wear and fatigue because they are only subjected to a force in one of the directions. Once the upper and lower thrust bearings  12 ,  14  are seated properly; the opposite bearing is isolated from the force in the direction to unseat the bearing because of the thin flange  32 . 
         [0023]    The outer faces  38  of the thick and thin flanges  30 ,  32  may also include a bearing material  42  disposed thereon. The bearing material  42  may be ramped to form the contours on the outer face  38 . The bearing material  42  is relatively softer than the underlying base metal of the bearing shell  16  and flanges  30 ,  32 , which are typically made of steel. Those copper or aluminum-based bearing materials typically used in thrust bearing applications may be used in the present invention. Although the invention contemplates other bearing materials as well including polymer-based material. The bearing material  42  may be added to the material before bending the flanges  30 ,  32  or after the flanges  30 ,  32  are bent. Preferably, the bearing material  42  is only present on the outer faces  38  of the thick flanges  30 . If the material is present on both outer faces  38 , then the bearing material  42  on the thin flange may be machined off to reduce the thickness  35  of the thin flange  32  relative to the thick flange  30 . 
         [0024]    Referring to  FIG. 3 , an engine assembly for use in a vehicle (not shown) is shown generally at  44 . The engine assembly has the thrust bearing assembly  10  incorporated therein. The upper and lower thrust bearings  12 ,  14  are preferably identically configured, but arranged opposite from one another in reverse orientation, such that the contoured thick flange  30  of the upper thrust bearing  12  is arranged opposite the thin flange  32  of the lower thrust bearing  14 . The thin flange  32  of the upper thrust bearing  12  is arranged opposite the thick flange  30  of the lower thrust bearing  14 . The engine assembly  44  includes an upper support surface  46 , a shaft  48  received within the upper support surface  46 , and a lower support surface  50 . The upper support surface  46  is preferably an engine block and the lower support surface  50  is preferably a bearing cap. The shaft  48  is preferably a crankshaft  48 . 
         [0025]    The thrust bearing assembly  10  rotatably supports the shaft  48  between the upper thrust bearing  12  and the lower thrust bearing  14  when in mating contact, as described above. A gap  52  is defined between the thick and thin flanges  30 ,  32  of the upper and lower thrust bearings  12 ,  14 , respectively. The gap  52  of the upper thrust bearing  12  receives the upper support surface  46  and the gap  52  of the lower thrust bearing  14  receives the lower support surface  50 . 
         [0026]    In the preferred embodiment, the shaft  48  is the crankshaft having forward and rearward lobes  54 ,  56  next adjacent the bearing assembly  10 . The terms “forward” and “rearward” are used to denote opposite ends or direction of the crankshaft in relation to the front and back of the engine, which may be arranged front to back in the vehicle, or transverse, as the case may be. The forward lobe  54  is closer to the front of the engine assembly  44  and the rearward lobe  56  is closer to the rear of the engine assembly  44 . The thick flange  30  of the upper thrust bearing  12  preferably engages the rearward lobe  56  of the shaft  48  and the thick flange  30  of the lower thrust bearing  14  preferably engages the forward lobe  54  of the shaft  48 . Alternately, the bearings  12 ,  14  may be reversed, such that the thick flange  30  of the upper thrust bearing  12  contacts the forward lobe  54  and the thick flange  30  of the lower thrust bearing  14  contacts the rearward lobe  56 . 
         [0027]    In the preferred embodiment, the upper and the lower thrust bearings  12 ,  14  define a clearance  58  between the thin flange  32  and the upper and the lower support surfaces  46 ,  50 , respectively. The clearance  58  is defined when the thick flange  30  abuts the respective upper and lower support surfaces  46 ,  50  when the upper and the lower support surfaces  46 ,  50  are positioned in the respective gaps  52 . The thick flange  30  has the thickness  34  greater than a sum of the thickness  35  of the thin flange  32  and the clearance  58 . The clearance  58  allows for isolation of the upper and lower thrust bearings  12 ,  14  when force is applied opposite the thick flange  30  of each thrust bearing  12 ,  14  respectively. The thick flange  30  of the upper thrust bearing  12  is the load bearing surface for a forward force and the thick flange  30  of the lower thrust bearing  14  is the load bearing surface for a rearward force. The thin flanges  32  do not receive the load and are therefore non-load bearing flanges. It is to be appreciated that the thin flanges  32  may even be omitted without deviating from the subject invention. When the forward force is applied to the shaft  48 , the lower thrust bearing  14  does not receive that force due to the clearance  58  adjacent the thin flange  32  and therefore the thick flange  30  of the upper thrust bearing  12  receives it. Likewise, when the rearward force is applied to the shaft  48 , the upper thrust bearing  12  does not receive that force due to the clearance  58  adjacent the thin flange  32  and therefore the thick flange  30  of the lower thrust bearing  14  receives it. This reduces the amount of wear and fatigue on the thrust bearing assembly  10  and prevents premature failure. This also ensures that the bearing assembly  10  remains properly seated. 
         [0028]    In operation, the upper thrust bearing  12  is positioned having the upper support surface  46  extending between the thick and the thin flanges  30 ,  32 . Preferably, the upper thrust bearing  12  is positioned with the thick flange  30  toward a rear of the engine assembly  44  and the thin flange  32  toward a front of the engine assembly  44 . After, the upper thrust bearing  12  is positioned, the shaft  48  is positioned adjacent the upper thrust bearing  12 . The lower thrust bearing  14  is then positioned having the lower support surface  50  extending between the thick and the thin flanges  30 ,  32 . Preferably, the lower thrust bearing  14  is positioned with the thick flange  30  toward the front of the engine assembly  44  and the thin flange  32  toward the rear of the engine assembly  44 . The upper and lower thrust bearings  12 ,  14  are positioned such that the thick flange  30  of one is matched radially opposite with the thin flange  32  of the other. The lower support surface  50  is secured to the upper support surface  46  to position the lower thrust bearing  14  in mating contact with the upper thrust bearing  12 . 
         [0029]    Once secured, the thrust bearing assembly  10  rotatably supports the shaft  48 . A rearward force is then applied to the shaft  48  toward the rear of the engine assembly  44  to seat the thick flange  30  of the lower thrust bearing  14  against the lower support surface  50 . Next, a forward force in the opposite direction is applied to the shaft  48  toward the front of the engine assembly  44  to seat the thick flange  30  of the upper thrust bearing  12  against the upper support surface  46 . During operation of the engine, these forward and reward forces are constantly be generated and absorbed by the thrust bearing assembly  10 . The thick flanges  30  of the upper and lower thrust bearings  12 ,  14  carries the load of these forces and the clearance  58  surrounding the thin flanges  32  prevent the upper and lower thrust bearings  12 ,  14  from becoming unseated. Because the thrust bearing assembly  10  does not become unseated, the bending and fatigue of the bearings  12 ,  14  is reduced, as described above. 
         [0030]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.