Abstract:
A bearing shell for a sliding bearing may include a body having a convex outer surface and an alignment feature projecting from the outer surface. The alignment feature may be arranged at an end face of the body. The alignment feature may include a first tapered portion having an axial width that reduces in a direction away from the end face. The first tapered portion may include at least two axial sides extending circumferentially and angled away from parallel with respect to a corresponding axial end face of the body by an angle of 2° to 10°.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to British Patent Application No. 1221213.0, filed Nov. 26, 2012, and International Patent Application No. PCT/GB2013/053050, filed Nov. 19, 2013, both of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to bearing shells for sliding bearings, particularly bearing shells for engine crankshaft bearing assemblies. 
     BACKGROUND 
     Engine bearing assemblies, such as crankshaft main bearings and connecting rod bearings, commonly comprise a pair of lined housings holding a rotatable shaft, with each housing being lined with a bearing shell. Each housing has a generally semi-cylindrical recess, shaped to receive a hollow generally semi-cylindrical bearing shell. The bearing shell typically comprises a backing layer that is provided with one or more layers on its concave inner surface, the innermost layer providing a running surface that faces the rotatable shaft. 
     The bearing shells in each bearing assembly may differ (e.g. having different materials or features), in which case it is preferred to ensure that the correct bearing shell is assembled into each of the housings (i.e. into the correct half of the bearing assembly). Alternatively, or additionally, bearing shells may be asymmetric along their circumference (for example if they are optimised for a particular direction of rotation of the shaft), in which case it is necessary to ensure that the bearing shells are assembled into the housing with the correct orientation. To ensure correct assembly of bearing shells into bearing housings, a bearing shell may be provided with an alignment feature, which projects outwardly from the convex outer surface of the bearing shell. The housing is provided with a corresponding alignment recess that receives the projecting alignment feature of the bearing shell. 
       FIGS. 1A and 1B  illustrate a bearing shell  100  having a first type of alignment feature  102 , which is manufactured by a first process, in which a narrow strip of material is pushed outwards (i.e. by being radially punched), with respect to the centre of curvature of the outer surface  104  of the bearing shell, into a die. The alignment feature  102  has parallel sides  106  parallel to the axial sides  108  of the bearing shell  100  (i.e. having constant axial width W, axial width being measured parallel with the axis of rotation of a shaft received into the bearing shell, and perpendicular to axial sides  108 ). The extent by which the alignment feature  102  projects from the convex outer surface of the bearing shell  100  tapers from a maximum projection level with the end face  110 . For example, in the case that the bearing shell is approximately 20 mm wide (in the axial direction), and has a diameter of 60 mm, the alignment feature may be 3 mm wide, may project 1 to 2 mm from the convex outer surface of the bearing shell, and may extend approximately 5 mm around the circumference from the end face. 
     The alignment feature  102  in  FIGS. 1A and 1B  is shown closer to one axial side  108  than the other. However, it will be appreciated that the position of the alignment feature may be selected according to the individual requirements, and in some cases may be located equidistantly between the axial sides  108 . 
     A second type of alignment feature is formed by a ‘coining’ process in which a punch is driven down onto an axially narrow, outer portion of an end face, which causes flow (i.e. deformation) of the punched material. Material flows out into a corresponding recess in a coining die supporting the bearing shell, and creates an alignment feature having the shape of a broad (i.e. along the axis of the bearing shell), outwardly projecting lip, that is slightly spaced apart from the end face. Any corresponding projection from the internal surface of the bearing shell should be avoided. An alignment feature of this second type, and a corresponding method of manufacture, is described in US2012027328A. 
     An alignment feature of either the first or second types provides a clear indication of the intended orientation of the bearing shell during assembly into a bearing housing (e.g. providing a visual indication to a worker during manual assembly, or providing a detectable indication of orientation during automated assembly), which provides a physical impediment to incorrect assembly. However, disadvantageously, such an alignment feature requires accurate axial alignment between the bearing shell and the bearing housing during assembly, which increases the complexity of assembly, and in particular reduces the reliability of automated assembly. 
     SUMMARY 
     A first aspect of the invention provides a bearing shell for a sliding bearing, the bearing shell having a convex outer surface and an alignment feature projecting from the outer surface adjacent an end face of the bearing shell, wherein the alignment feature comprises a first tapered portion having an axial width that reduces away from the end face, and each side of the first tapered portion is angled away from parallel with an axial end face of the bearing shell by an angle of 2° to 10°. 
     A second aspect of the invention comprises an engine comprising a housing and a bearing shell according to the first aspect, in which the bearing shell is received into a recess in the housing. 
     A third aspect of the invention provides a method of manufacturing a bearing shell for a sliding bearing, the bearing shell having a convex outer surface and an alignment feature projecting from the outer surface adjacent an end face of the bearing shell, wherein the alignment feature comprises a first tapered portion having an axial width that reduces away from the end face, and each side of the first tapered portion is angled away from parallel with an axial end face of the bearing shell by an angle of 2° to 10°, the method comprising: 
     providing a bearing shell or a flat blank for a bearing shell, and 
     forming the alignment feature. 
     Advantageously, such an alignment feature enables less complex and more reliable assembly of a bearing shell into a corresponding bearing housing. In particular such an alignment feature may provide wider axial alignment tolerances than for known alignment features, during assembly of the bearing shell into a corresponding bearing housing. Further, such an alignment feature may provide a degree of axial self-alignment of the bearing shell and bearing housing during assembly. Advantageously, angling each side of the first tapered portion away from parallel with an axial end face of the bearing shell by an angle of up to 10° provides an alignment feature that may be easily assembled into a corresponding recess of the housing. 
     Each side of the tapered portion may be angled away from parallel with an axial end face of the bearing shell by an angle of 3° to 7°. Each side of the tapered portion may be angled away from parallel with an axial end face of the bearing shell by an angle of substantially 5°. 
     The alignment feature may comprise a further portion proximal to the end face, and the first tapered portion distal to the end face. Advantageously, the provision of the further portion may strengthen the alignment feature. 
     The further portion may be a second tapered portion, having an axial width that reduces away from the end face, and wherein the first tapered portion has a greater taper than the second tapered portion. The axial width of the second tapered portion may taper such that each side of the first tapered portion is angled away from an axial end face of the bearing shell by less than 1°. 
     The further portion may have a constant axial width. 
     The first tapered portion may taper such that sides of the tapered portion do not meet. Advantageously, if the sides of the tapered portion do not meet, a stronger connection may be provided between the alignment feature and the main part of the bearing shell. 
     The first tapered portion may have a circumferential length of at least half its mean axial width, and preferably greater than its mean axial width. Advantageously, a longer circumferential length, for a given taper of the first tapered portion enables self-alignment for greater axial misalignment. 
     The alignment feature may project from the outer surface of the bearing shell by an extent that reduces away from the end face, along its circumferential length. 
     The alignment feature may extend circumferentially from substantially level with the end face of the bearing shell (i.e. the alignment feature may end substantially flush with an end face). 
     The alignment feature may be spaced apart circumferentially from the end face of the bearing shell. The alignment feature may be spaced apart from the end face by less than its greatest axial width. 
     The alignment feature may be formed by a process selected from the group comprising: 
     coining, embossing, and punching. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: 
         FIG. 1A  shows a perspective view of a part of a bearing shell and alignment feature according to the prior art; 
         FIG. 1B  shows a view of the alignment feature of Figure lA perpendicular to the outer surface of the bearing shell; 
         FIG. 2A  shows a perspective view of part of a bearing shell and an alignment feature according to a first embodiment of the present invention; 
         FIG. 2B  shows a view of the alignment feature of  FIG. 2A  perpendicular to the outer surface of the bearing shell; 
         FIG. 2C  shows the alignment feature of  FIG. 28  being assembled into a corresponding housing; 
         FIG. 3A  shows a perspective view of a bearing shell and an alignment feature according to a third embodiment of the present invention; 
         FIG. 3B  shows a view of the alignment feature of  FIG. 3A  perpendicular to the outer surface of the bearing shell; and 
         FIGS. 4A and 4B  show alternative views of bearing shells of a further embodiment, viewed perpendicular to the outer surface of the bearing shell. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2A and 2B  illustrate an end part of a bearing shell  200  according to a first embodiment of the present invention. The bearing shell  200  is generally hollow semi-cylindrical, and is provided with an alignment feature  202  that projects outwardly (i.e. radially) from the outer convex surface  204 , projecting away from the centre of curvature of the bearing shell. 
     The alignment feature  202  has a tapered axial width W, having sides  206  that are each angled by an angle θ of 5° with respect to the corresponding axial sides  208  of the bearing shell  200 . Alignment feature  202  has a first end  212  that is substantially level with the adjacent end face  210  of the bearing shell  200 . The alignment feature  202  has a straight second end  214  furthest from the end face  210  of the bearing shell  200 . The alignment feature tapers from W1 at the first end  212  adjacent to the end face  210  to W2 at the second end  214  furthest from the end face. The extent P by which the alignment feature  202  projects outwardly from the outer convex surface  204  of the bearing shell  200  is greatest at the first end  212  adjacent the end face  210  and tapers along the circumferential length L (i.e. perpendicular to the end face  210 ) of the alignment feature  202 , reducing to zero at the opposite second end  214  of the alignment feature. 
       FIG. 2C  shows the relative positions of the partly assembled bearing shell  200  and housing  250 , when the bearing shell is being inserted into the housing in the direction indicated by the arrows A. Advantageously, the alignment feature  202  of the present invention enables self-alignment between the bearing shell  200  and the housing  250 , in the axial direction (i.e. perpendicular to the axial end faces  208 , being the direction of the axis of rotation of a rotatable shaft received into the bearing shell). So, if there is relative axial misalignment M between the bearing shell  200  and the housing  250  as they are initially brought together, due to the mechanical interaction between the sides  206  of the alignment feature  202  and the sides  256  of the corresponding alignment recess  252  into which the alignment feature is received, the bearing shell and housing will become axially aligned once they are fully assembled. 
     In the embodiment illustrated in  FIG. 2A , the extent by which the alignment feature  202  projects P from the outer convex surface  204  of the bearing shell  200  tapers to zero at the second end  214 , furthest from the end face  210 . 
     In the embodiment illustrated in  FIGS. 2A and 2B , the alignment feature extends circumferentially from the first end  212  being substantially level (flush) with the end face  210 . Such an alignment feature may be conveniently manufactured by an outward (radial) punching or embossing operation. 
     In the case of a punching process, a punch is driven against the concave inner surface of the bearing shell in the direction indicated by the arrow F 1 , whilst the convex outer surface  204  is supported by a die with a corresponding recess, into which the alignment feature is formed. The face of the punch is angled relative to the portion of the concave inner surface that it strikes, such that the first end  212  of the alignment features  202  projects outwardly from the convex outer surface by the greatest extent. A shear  216  is formed between the sides  206  of the alignment feature  202  and the main part of the bearing shell  200 , whilst the alignment feature remains joined to the main part of the bearing shell at the second end  214 , about which the alignment feature bends. 
     Alternatively, the end  318  of the alignment feature  302  may be slightly spaced apart S from the end face  410  of the bearing shell  300 , as is illustrated in  FIGS. 3A and 3B . Such an alignment feature  302  may conveniently be formed by a coining process, in which a coining punch is driven down in the direction of arrow F 2  into the end face  310  of the bearing shell  300  to form the alignment feature  302 . In this coining process, the bearing shell  300  is supported by a coining die having a corresponding recess, into which the material of the alignment feature  302  flows, as the coining punch is driven into the end face  310 . 
     The alignment feature may have a plurality of sections along its circumferential length, in which the section further from the end face tapers by a greater amount than the section closer to the end face. As is illustrated in  FIG. 4A , in one embodiment, the alignment feature section  402 A furthest from the end face  410  tapers in axial width W in accordance with the present invention, and the alignment feature section  402 B closest to the end face has a uniform axial width W1. Alternatively, as is illustrated in  FIG. 4B , the alignment feature section  402 B′ closest to the end face  410 ′ may taper in axial width, but by less than the alignment feature section  402 A′ furthest from the end face of the bearing shell  100  (i.e. φ&lt;θ). 
     The figures provided herein are schematic and not to scale. 
     Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
     Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.